detail design

3-1

SECTION 300 DETAIL DESIGN

301 GENERAL

301.1 DESIGN PHILOSOPHY

Section 300 of this Manual establishes generaldesign guidelines, details, specialrequirements and reasonable alternatives,which, when incorporated by the engineer ina set of bridge plans, will provide a bridgestructure that meets load requirements,provides structural integrity, structuralefficiency and reduces long term maintenanceto a minimum level.

301.2 DESIGN METHODS

Ohio Department of Transportation bridgedesigns are to be developed in generalconformance with AASHTO’s StandardSpecification for the Design of HighwayBridges, latest editions including all interims.Exceptions to AASHTO standards aredocumented in this Manual.

For design of Temporary Structures seeSection 500 of this Manual.

301.3 LOADINGREQUIREMENTS

Highway Structures:

MS18 and Alternate Military Loading ***(Case I or Case II)

* Applies to Steel Structures

** Including liveload factor increase of25%

All bridges shall be designed for a futurewearing surface (FWS) of 2.87 kPa.

Pedestrian and Bikeway Bridges:

To be designed in accordance with AASHTO,"ODOT Policy and Procedure for BicycleProjects", latest edition, and the following:

Bridges which cannot accommodate vehiclesbecause of narrow roadway or walkwaywidths or other access limitations shall bedesigned based on the AASHTO GuideSpecification for Pedestrian Bridges.

Bridges whose width can accommodateservice vehicles shall be designed based on theAASHTO Guide Specification for PedestrianBridges and an M13.5 vehicle.

Railroad Bridges:

Bridges are to be designed in accordance withcurrent AREA specifications and theindividual railway company’s loadingrequirements. All other aspects of thestructure design shall conform to AASHTO.

SECTION 300 DETAIL DESIGN - METRIC SEPTEMBER 1998

3-2

301.3.1 SEISMIC DESIGN

Outlined in this section, are general Seismicdesign requirements for Ohio. Ohio is con-sidered to be in Zone A based on accelerationcoefficients below .09. The followinginformation is only meant to highlightAASHTO requirements. The designer shouldrefer to AASHTO for complete requirements.

Zone A structure designs are to comply withtwo requirements:

• Connection of the superstructure to thesubstructure shall be designed to resist ahorizontal seismic force equal to .20 timesthe dead load reaction force in the restraineddirection. The restrained direction for anexpansion bearing is transverse to thestructure.

• Bearing seats shall be designed to provideminimum support length N, measured nor-mal to the face of an abutment or pier. Nshall not be less than computed by thefollowing formula:

N(in mm) = 203 + 1.67L + 6.67H Where:

L = length, in meters, of the bridge deckto the adjacent expansion joint or tothe end of the bridge deck.

For Abutments

H= average height, in meters, ofcolumns supporting the bridge deckto the next expansion joint.

(single span bridges, H = 0)

For columns and/or piers

H = column or pier height, in meters

For hinges within a span

H = Average height of the adjacent twocolumns or piers, in meters.

301.4 REINFORCING STEEL

Reinforcing steel - ASTM A615M, A616M orA617M, Grade 420, Fy= 420 MPa

All reinforcing steel shall be epoxy coated.

301.4.1 MAXIMUM LENGTH

Generally maximum length of reinforcingsteel should be 12 200 mm. This limit is forboth transit purposes and constructionconvenience. The maximum length before alap splice is required is 18 400 mm.

The length of the short dimension of L-shapedbars should be limited in order not to extendbeyond the sides of a highway vehicle ofmaximum legal width. The short dimensionshould preferably be not greater than 2300mm, and in no case greater than 2450 mm.


3-3

301.4.2 BAR MARKS

Bar marks shall be used on detail plans toidentify the bar’s position and to reference thebar to the reinforcing bar list and description.The actual size of reinforcing steel bar shall bepart of the bar mark.

Example:[16M bar - bar mark - A16M01]

Letters should be incorporated into the barmarks to help identify their location in thedetail plans: Some examples are "A" forabutments, "P" for piers and "S" forsuperstructure.

Example: [A16M01]

Spiral reinforcing should use the letters "SP"to identify its bar mark.

Example: [ SP16M01]

Straight bars used in drilled shafts shallinclude the letters "DS" in their bar mark.

Example: [DS16M01]

A note or legend within the bar list sheet inthe plans shall describe each bar mark’smeaning.

See Figure 301 - -4

301.4.3 LAP SPLICES

Bar splice lengths shall be shown on the plans.

Development and splice lengths shall conformto AASHTO requirements.

Reinforcing steel at construction joints shouldextend into the next pour only by the requiredsplice length.

Reinforcing steel shall not project throughexpansion and contraction joints.

In lieu of lap splices, mechanical splices inaccordance with the requirements of CMS509 may be used.

CMS 509 Mechanical splices, should developa minimum ultimate strength of 125 percent ofthe required yield strength of the reinforcingsteel they connect. Standard reinforcing steeldevelops a minimum ultimate strength of 150percent of the minimum required yieldstrength. The designer should be aware of this17% reduction in the ultimate tensile strengthof the reinforcing at the location of themechanical splice.

Due to lap splice lengths required, thedesigner should use mechanical type splicesfor No. 43M and 57M bars.

Splicing of reinforcing by welding is notpermitted.


3-5

Where a horizontal construction joint is usedin a column or pier, the reinforcement shouldbe continuous and splices avoided if at allpossible. An exception to this is theconstruction joint between a column and afooting, where the reinforcement should bediscontinuous and adequate splice lengthshould be furnished.

For Tension Splice lengths See Figure 302 -Page 3-6

For Compression Splice lengths See Figure303 - Page 3-7

For Development Length Requirements forReinforcing Steel, See Figures 303, 304 &305 - Pages 3-7, 3-8, 3-9

301.4.4 CALCULATINGLENGTHS ANDWEIGHTS OFREINFORCING

Reinforcing steel lengths shall be calculated tothe nearest 25 mm. Standard bend lengthsshall be based on criteria in CMS 509.

The length or height of a spiral is defined asthe distance out-to-out of coils, including thefinishing turns at top and bottom.

The weight of the spiral finish, the additional1-1/2 coils of spiral required at the end of thespiral, AASHTO 8.18.2.2.4, should becalculated and included. For a 765 mmdiameter spiral with 16M bars the additionalweight of 3 coils is 11.0 kg.

See Figure 306 - Page 3-10 for area, weightand diameter of standard reinforcing.

See Figure 307 - Page 3-11 for bar bendingdata.

See Figure 308 - Page 3-12 for standard barlength deductions of common bends.

301.4.5 BAR LIST

Bar lists should include the following:

• Bar Mark• Number of bars required• Overall length required of the bar• Total Weight for each bar mark• Column for type of bar:

"ST" for straight"Number" assigned to"Numbered Bent Bar Detail""Number" and "Series" for series typebars

Dimensions are defined by letters A through Zassociated with the "Numbered Bent BarDetail" showing position of letters.

Spiral reinforcing shall also be included in thedetail plan's bar list. The followinginformation shall be shown on the bar list:

• core diameter • pitch • mark• number• height• weight • plan note for spiral bars

See Figure 301 - Page 3-4


3-13

301.4.6 USE OF EPOXY COATEDREINFORCING STEEL

All reinforcing steel shall be epoxy coatedexcept as noted for prestressed beams inSections 302.5.1.7 and 302.5.2.8.

All approach slabs shall have epoxy coatedreinforcing steel.

301.4.7 MINIMUM CONCRETECOVER FORREINFORCING

The clearances of reinforcing steel from theface of the concrete shall be as follows:

Top reinforcing steel in bridge decks and sidewalks - 65 mm - (including 25 mmmonolithic wearing surface)

Bottom reinforcing steel in bridge decks 40 mm

Bottom steel of footings 75 mm

Column steel or spirals 75 mm

All other concrete 50 mm

Clearances not given in CMS 509.04 shallbe shown in the detail plans.

301.4.8 MINIMUMREINFORCING STEEL

Minimum reinforcing steel requirements shallconform to AASHTO requirements forshrinkage and temperature reinforcement.Reinforcement for shrinkage and temperaturestresses shall be provided near exposedsurfaces of walls and slabs not otherwisereinforced.

The total area of reinforcing steel to beprovided shall be 265 mm2 per meter in eachdirection.

The spacing of temperature and shrinkagereinforcement shall not exceed 3 times thewall or slab thickness, or 450 mm.

301.5 REFERENCE LINE

For structures on a horizontal curve areference line, usually a chord of the curve,shall be provided. This reference line shouldbe shown on the General Plan/Site Plan viewwith a brief description, including, forexample, "Reference Line (centerline bearingto bearing)," and the stations of the pointswhere the reference line intersects the curve.Skews, dimensions of substructure elementsand superstructure elements should be givenfrom this Reference Line, both on the GeneralPlan/Site Plan and on the individual detailsheets. Dimensions from the curve generallyshould be avoided. The distance between thecurve and reference line should bedimensioned at the substructure units. In thismanner a check is available to the contractor.


3-14

The reference tangent can be used ifappropriate.

301.6 UTILITIES

Utilities should not be supported on the faciaof bridge decks.

Utilities, other than gas and water, may be runthrough sidewalk sections or parapets ofbridges but shall be encased in a protectiveconduit.

Utility conduits embedded in concrete shouldbe shown and dimensioned so as to clearconstruction joints by a minimum of 25 mmand other conduits by a minimum of 50 mm.

No utilities shall be embedded in the actualvehicular traffic carrying section of a concretedeck.

Utilities should not be suspended below thebottom of the bridge superstructure.

For approval procedures for installation ofutilities on bridges, please refer to ODOT’s"Utilities Manual", Sections 8.10, page 14,and 8.20, page 23.

301.6.1 UTILITIES ATTACHEDTO BEAMS ANDGIRDERS

All utility lines placed between the stringers ofgrade separation structures should not belocated in the floor panel behind the faciastringer. This is to protect the lines from colli-sions.

Critical utility lines (gas, etc.) which couldcontribute to the severity of a collision shouldbe located well above the bottom of thesuperstructure or be otherwise protected.

If the bridge design is a composite deck onprestressed box beams, the design may eithereliminate an interior box beam or provide aspace between two interior box beams toprovide utility access in this space. Thisalternative will require a special design forboth the boxbeams and the deck.

301.7 CONSTRUCTIONJOINTS, NEWCONSTRUCTION

Construction joints should be anticipated andprovided for in the detail plans. Jointlocations should be selected such that they areaesthetically least objectionable, allowconstruction to be properly performed and areat locations of minimum stress. Constructionjoints shall be designed to transfer all loads.

302 SUPERSTRUCTURE

302.1 GENERAL

302.1.11.1 CONCRETESUPERSTRUCTURE

Concrete Design Allowables

Superstructure Concrete - Class SLoad Factor Design - 31.0 MPa


3-15

Service Load Design - .33 x 31.0 MPa =10.3 MPa

Substructure Concrete - Class CLoad Factor Design - 27.5 MPa

Service Load Design - .33 x 27.5 MPa =9.2 MPa

302.1.1.1 SUPERSTRUCTURECONCRETEREQUIREMENTS

302.1.1.1.a CLASS SSUPERSTRUCTURECONCRETE

Class S Concrete is the Department’s standardconcrete mix design for superstructureconcrete. The mix design, curing and placingrequirements are defined in the C & MS.

302.1.1.1.b HIGH PERFORMANCECONCRETE

High performance concrete, may be specifiedfor use on bridge structures

High performance concrete mix designs areintended to give a highly dense, veryimpermeable concrete mix resulting in alonger structure life.

High performance concrete is defined inSupplemental Specification 844 whichspecifies the construction, materials, mixdesigns, placement, curing and testingrequirements for this type concrete.

The high performance concrete SupplementalSpecification 844 incorporates concrete mixdesigns for both superstructure andsubstructure concrete.

The bid item for testing of high performanceconcrete shall be included in the plans onlywhen required by the District.

High performance concrete should not be usedas a replacement for the drilled shaft concreteas specified in 524.10.

302.1.1.1.c SELECTION OFCONCRETE FORBRIDGE STRUCTURES

For structures on or off the National HighwaySystem, Class S or high performance concretemay be specified for the superstructure. ClassC or high performance concrete may bespecified for the substructure.

The responsible District Administrator shallbe contacted to confirm the selection ofconcrete type to be used on the specificstructure.

302.1.1.2 WEARING SURFACE

302.1.1.2.a TYPES

• 25 mm monolithic concrete - defined asthe top 25 mm of a concrete deck slab.This 25 mm thickness shall not beconsidered in the structural design of thedeck slab or as part of the compositesection.


3-16

• 64 mm - minimum asphaltic concretewearing surface to be used only on non-composite prestressed box beams.

32 mm minimum of Item 448 AsphaltConcrete Surface Course, Type 1H

32 mm thickness of Item 448 AsphaltConcrete Intermediate Course, Type 1,PG64-28

• Cast in place deck thickness of compositeprestressed box beams shall be aminimum of 155 mm. Also see Section302.5.1.2

302.1.1.2.b FUTURE WEARINGSURFACE

All bridges shall be designed for a futurewearing surface (FWS) of 2.87 kPa.

No future wearing surfaces shall beconsidered as included in the design deckthickness in the analysis and design of thesuperstructure.

302.1.1.3 CONCRETE DECKPROTECTION

3.2.1.1.3.a TYPES

• Epoxy Coated Reinforcing Steel - CMS709.00

• Minimum concrete cover of 65 mm

• Class S concrete

• High Performance Concrete

• Cathodic protection systems

• Drip Strips

• CMS 512, Type D, Membranewaterproofing or CMS 512 Sheet typewaterproofing, Type 3

• Asphaltic concrete wearing surface.

• Liquid coatings, sealants and treatments(for vertical deck surfaces subjected toroadway drainage).

302.1.1.3.b WHEN TO USE

• All reinforcing steel shall be epoxy coated.

• All cast in place concrete decks shall haveminimum concrete top cover of 65 mm.

• A drip strip shall be used on any decks withover the side drainage. See Bridge StandardDrawing DS-1-92M.

• Cathodic protection systems are consideredto be experimental and are to be approvedby the Office of Structural Engineering.Approval will be limited to special cases asconditions warrant.


3-17

• Non-composite box beam bridges, with overthe side drainage, shall have an asphaltconcrete overlay. The overlay shall beplaced over either a waterproofingmembrane, Type D, CMS 512 or sheet typewaterproofing, Type 3, CMS 512.Minimum thickness of overlay is 64 mm -See section 302.1.1.2.a

302.1.1.3.c SEALING OFCONCRETE SURFACESSUPERSTRUCTURE

Specifications for sealing material are definedin a Departmental proposal note. Concretesurfaces shall be sealed with an approvedconcrete sealer as follows:

For bare concrete decks with over-the-sidedrainage; the exterior 230 mm width on thetop of the deck, the deck facia and a 150mm (minimum) width under the deck shallbe sealed with either an epoxy-urethane ornon-epoxy sealer.

On decks with curbs and/or sidewalksand/or parapets a 230 mm width of theroadway along the curbline, the vertical faceof curb, the top of the curb and/or sidewalk,the inside face, top an outside face of theparapet, the deck facia, and a 150 mm(minimum) width under the deck shall besealed with either an epoxy-urethane ornon-epoxy sealer.

For decks with concrete deflector parapetsa 230 mm width of the roadway along the

face of parapet, the inside face, top andoutside face of parapet, the deck facia and a150 mm (minimum) width under the deckshall be sealed with either an epoxy-urethane, or non-epoxy sealer.

For non-composite prestressed concrete boxbeam decks with over-the-side drainage, thefacia of the outside beams and a minimum150 mm width under the beam shall besealed with a non-epoxy sealer.

See Figures:

309 - Page 3-18

310 - Page 3-19

Concrete surfaces that include patches shouldbe sealed with an epoxy-urethane sealer sothe concrete color will remain uniform.

The designer should include in the plansactual details showing the position, locationand area required to be sealed. A plan noteshould not be used to describe the location asthere can be both description andinterpretation problems.

The designer has the option to select a specifictype of sealer, epoxy-urethane or non-epoxy.The designer also has the alternative to justuse a bid item for sealer, with no preference,and allow the contractor to choose based oncost.


3-20

302.2 REINFORCEDCONCRETE DECK ONSTRINGERS

302.2.1 DECK THICKNESS

Bridge deck concrete thickness shall meet therequirements of AASHTO, this Manual andStandards.

For reinforced concrete decks on steel orconcrete stringers the deck thickness shall benot less than the larger of (S + 5200)/36 or215 mm. S being the effective span length inmillimeters.

The 25 mm wearing thickness, section3.2.1.1.2.a, is included in the calculations forminimum concrete deck thickness but not inthe calculations during actual structural designof the deck slab.

For transversely reinforced concrete deckslabs supported on steel stringers the effectivespan length "S" shall be considered equal tothe distance center-to-center of stringersminus 150 mm.

For concrete I-beam stringers the effectivespan length shall meet the requirements ofAASHTO 3.24.1.2.

302.2.2 CONCRETE DECKDESIGN

The concrete deck design shall be inconformance with AASHTO, latest edition,and additional requirements in this Manual.

For continuous slabs on three or moresupports a continuity factor of .80 shall beapplied to the simple span bending momentsfor both live load and dead load.

See Figures 311, 312, 313 & 314 - Pages 3-22,3-23, 3-24, 3-25 for an illustration of a methodof design for a reinforced concrete deck slab.

Upon completing the concrete deck designfrom the example above, or similar method,the designer should assure any cantilevereddeck overhang will not over stress the initialdeck design due to the dead load and thegreater live load of either the vehicle wheelloads or the railing live loads. See relevantAASHTO sections for liveload applicationrequirements. See example Figures 315 &316 - Pages 3-26 & 3-27

Transverse spacing of the top and bottomreinforcing in a deck design shall meet section302.2.4.2

302.2.3 SCREED ELEVATIONS

Screed elevations shall be furnished to ensurethe bridge deck is completed at its correctelevation, including the gutters or edges ofdeck on a bridge without curbs.

The detail structure plans shall include adiagram or table showing the elevations at thetop of the concrete deck that are requiredbefore the concrete is placed. Elevationsshould be shown for both curblines and crownof the roadway and above all steel beam orgirder or prestressed I beam lines for the fulllength of the bridge, at all bearings and at amaximum of 10 000 mm intervals. Elevations


3-21

at mid span are optional and need be shownonly for short spans where the nearest 10 000mm point might be some distance from thepoint of maximum deflection. Elevations atsplice points will be required.

Cases of special geometry, i.e. spirals,horizontal or vertical curves, superelevationtransitions, etc., will require additionalelevation points to define the concrete deckscreed elevations. A sufficient number ofscreed elevations must be provided so thecontractor is not forced to interpolate or makeassumptions in the field.

The designer shall furnish all elevation pointsto allow the proper construction and finishingof the deck.

For bridges with a separate wearing course,the elevations given should be those at the topof the portland cement concrete deck. Providea plan note stating at what surface theelevations are given in order to eliminate anyconfusion.

Screed elevations are not required for boxbeam bridges.

302.2.4 REINFORCEMENT, i.e. SIZE,LENGTH, SPACING

302.2.4.1 LONGITUDINAL

Distribution reinforcement in the topreinforcing layer of a reinforced concrete deckon steel or concrete stringers shall beapproximately 1/3 of the main reinforcement,uniformly spaced.

Research has shown that secondary bars in thetop mat of reinforced concrete bridge decks onstringers should be small bars at close spacing.Therefore the required secondary bar size shallbe a #13M. The only exception to thisrequirement is if the bar spacing becomes lessthan 75 mm.

For stringer type bridges with reinforcedconcrete decks, the secondary bars shall beplaced above the top of deck primary bars.This helps in reducing shrinkage cracking andadds additional cover over the primary bars.

For reinforced concrete deck slabs on stringertype bridges, where the main reinforcement istransverse to the stringers, additional toplongitudinal reinforcement shall be providedin the negative moment region over the piers.This additional secondary reinforcement shallbe equal to the distributional reinforcement(1/3 of the main reinforcement). Theadditional reinforcement shall be uniformlyspaced and furnished in length equal to 40percent of the length of the longer adjacentstringer span. This reinforcement should beplaced approximately symmetrical to thecenterline of pier bearings but with everyother reinforcing bar staggered 1000 mmlongitudinally.

The total longitudinal reinforcement over apier shall meet the requirements of AASHTO.

302.2.4.2 TRANSVERSE

To facilitate the placement of reinforcing steeland concrete in transversely reinforced deckslabs, the top and bottom main reinforcementshall be equally spaced and placed to coincidein a vertical plane.


3-28

For steel beam or girder bridges with a skewof less than 15 degrees the transversereinforcing may be shown placed parallel tothe abutments. Bridges with a skew greaterthan 15 degrees or where the transversereinforcing will interfere with the shear studsshould have the transverse reinforcementplaced perpendicular to the centerline of thebridge.

For prestressed I-beams or composite boxbeam bridge decks transverse reinforcing shallbe placed perpendicular to the centerline ofthe bridge.

For steel beam or girder bridges, the clearanceof the bottom transverse bars over the top ofany bolted beam splice plates or momentplates should be checked as reinforcing bars ata skew generally cannot be placed betweenbolt heads.

302.2.5 HAUNCHED DECKREQUIREMENTS

Concrete decks on steel beam or girder orprestressed I beam structures shall have adesign concrete haunch of 50 mm. Theminimum 50 mm haunch depth shall bemeasured from the highest top flange pointand the haunch shall be tapered back to theoriginal concrete deck thickness in a 225 mmlength. The concrete haunch shall encase theedges of the top flange.

See Figures 317 & 318 - Page 3-29 & 3-30

302.2.6 STAY IN PLACE FORMS

Galvanized steel or any other material type,stay in place forms, are not recommended foruse.

302.2.7 CONCRETEPLACEMENTSEQUENCE

Placement sequences are not generallydetailed for standard steel beam or girderbridges but are left to the contractor. Thedesigner should recognize the need for a poursequence is not limited to long structures withan intermediate expansion device. Otherpossible structure types are bridges with endspans less than 70 percent of internal spans,two span structures, structures whose sizeeliminates one continuous pour, etc.

Placement sequences are required forcontinuous deck prestressed I beam bridges.Standard Drawing PSID-1-95M defines asequence of deck placement for a prestressedI beam bridge.

302.2.8 SLAB DEPTH OFCURVED BRIDGES

For a curved deck on straight steel beams,steel girders or prestressed I beams, the dis-tance from the top of the slab to the top of thebeams or girders will vary from end to end.The slab depth dimension shall show thisvariation by giving the maximum andminimum depth dimensions with theirrespective location, over the piers, center ofspan, etc.


3-31

An alternate is to accommodate thedifferential depth by including it in theCamber Table as geometric camber.

302.2.9 STAGED CONSTRUCTION

For steel beam and girder bridges andprestressed I-beam bridges where the deadload deflection is greater than 6 mm, a deckclosure is required if the bridge is constructedin stages.

For requirements regarding closure pours onbridge widenings or on existing structureswith new concrete decks see Section 400 ofthis Manual.

The closure pour between the stages shall bea minimum width of 800 mm but should bewide enough to accommodate the requiredreinforcing steel lap splices.

Intermediate cross frames and diaphragmsshall not be permanently attached in theclosure pour location until the concrete pourson both sides of the closure pour location havebeen completed.

The two construction joints created by theconcrete closure pour should be sealed withHigh Molecular Weight Methacrylate(HMWM) in accordance with SupplementalSpecification 846. The sealing width shouldbe 600 mm, centered on the constructionjoints.

302.3 CONTINUOUS ORSINGLE SPANCONCRETE SLABBRIDGES

302.3.1 DESIGNREQUIREMENTS

Continuous reinforced concrete slab bridgedesign shall be in conformance withAASHTO, latest edition, and additionalrequirements in this Manual.

For the Strength Design Method, AASHTO’sTable 3.22.1A L+I (Live load and Impact)beta factors shall be increased by a factor of1.25.

For simple span reinforced concrete slabbridges cast in place directly on concretesubstructures, the effective span length shallbe considered equal to the clear span plus two-thirds (2/3) the slab bearing width but notmore than the clear span plus the slabthickness.

Simple span reinforced concrete slab bridgesuperstructures should conform to StandardDrawing SB-6-94M. The reinforcing steelrequired will need to be changed by the designer to comply with the change in StrengthDesign beta factors listed in the paragraphabove.

Multi-span reinforced concrete slab bridgesuperstructures should conform to StandardDrawing CS-1-93M. The reinforcing steelrequired will need to be changed by the designer to comply with the change in StrengthDesign beta factors listed in the paragraphabove.


3-32

302.4 STRUCTURAL STEEL

302.4.1 GENERAL

Composite or non-composite steel beam andgirder superstructures shall be designed usingStrength Design Method (Load FactorDesign). A non-composite design may beused only if the design is the most economical.

Designs incorporating shear connectors in thenegative moment region may be used.

For the Strength Design Method, AASHTO’sTable 3.22.1A L+I (Live load and Impact)beta factors shall be increased by a factor of1.25. This increase in beta factors is not to beused in applying the overload provisions ofAASHTO Section 10.57.

All curved beams or girders shall be designedin accordance with AASHTO, this Manualand the 1993 AASHTO Guide Specificationsfor Horizontally Curved Highway Bridges,including Addenda.

The laterally unsupported length of top flangesof beam and girder members with a concretedeck encasing the top flange or compositelydesigned with studs shall be considered to bezero. In the absence of such fastening ordirect contact of an individual beam or girdermember, the unsupported length shall be con-sidered as the distance between thediaphragms, struts, bridging, or other bracing.

While the final design of a steel stringerbridge with top flanges embedded in aconcrete deck assumes the laterallyunsupported length to be considered zero, thedesigner shall investigate whether, duringconstruction and erection, the supportedlength will be exceeded by non-compositeerection and deck placement stresses.

302.4.1.1 MATERIALREQUIREMENTS

Types of steel to be selected for use in thedesign and construction of bridges is asfollows:

• High strength, low alloy, (A572M) steel,painted, shall be the primary selectedsteel.

• Unpainted A588M weathering steelshould generally be used for streamcrossings and roadways over railroads.

• If unpainted A588M weathering steel isused a 3000 mm length of the beam orgirder adjacent to abutments withexpansion joints and on both sides ofintermediate expansion joints shall bepainted with the IZEU paint system. Allcross frames, end frames or any othersteel in these 3000 mm sections shall alsobe painted. The top coat shall be tintedto a color to closely match FederalStandard No 595a - 20045 or 20059 (thecolor of weathering steel).


3-33

• Painted A572M steel should be used inindustrial areas, corrosive areas, inoverpasses or where subjected toaccumulations of dirt or debris or exposedto continuous moisture.

• A36M painted steel may be considered ifdeflection constraints or strength controlsdo not require the use of the higherstrength steels.

• For galvanized structures A-572M steelshould be used.

For A-588M steel, CMS 513 and 863 requiresoutside and bottom surfaces of facia beams orgirders to be blast cleaned to grade Sa 2 afterconcrete has been placed. This is to helpeliminate major blast cleaning problems on theconstruction site. It does not alleviate the finalrequirements of CMS 513.221. The pay itemwill become an "As per plan" pay item.

302.4.1.2 ATTACHMENTS

Detail plans of steel beam and girder bridgesshall show where welded attachments areallowed for construction purposes.

Welding of attachments, either permanent ortemporary, is not acceptable in tension areas.Welding is allowed in compression areas.Detail plans shall show the extent ofcompression and tension areas.

Welding of scuppers, down spouts or drainagesupports should not be allowed in tension areasof main members.

302.4.1.3 STEEL FABRICATIONCERTIFICATION

CMS 501.04 requires structural steel forbridges, exclusive of expansion joints, bearingdevices and secondary and detail material, befabricated by AISC (American Institute ofSteel Construction) certified fabricators.Recent changes in AISC have created newlevels of fabricators.

AISC Category SBr - fabricators qualifiedfor simple bridge structures

AISC Category Mbr - fabricatorsqualified for all other bridge structures.

AISC has also established a P and Fendorsement for fabricators.

P - Painting of steel structuresendorsement

F - Fracture Critical endorsement.

The Department has established a newSupplemental Specification 863 for structuralsteel. This specification establishes seven (7)levels of fabricator qualification using the newAISC fabricator qualification levels.


3-34

When modifications or repairs to a steelstructure involve only small amounts of mainmaterial, (cross frames, brackets, etc.) requiringlittle or no welding with only a minimalamount of fabrication, such steel, furnishedunder SS 863 , should not require AISCCertification but be defined for theMiscellaneous level. By using this appropriateSS 863 pay item the AISC requirement will bewaived.

302.4.1.4 MAXIMUM AVAILABLELENGTH OF STEELMEMBER

The rolling mills have established certainmaximum lengths of rolled beams. Millscurrently rolling beams can supply up to 35 000mm, but an cost extra is added for lengths over24 300 mm. The designer should consider thislimitation and provide for field splices andallow for optional field splices.

Length of a girder is generally limited by theability to transport the member from thefabricator’s shop to the jobsite. A length of 36000 mm for girders is generally the maximumlength between splices but girder lengths of 49000 mm and greater have been transported toproject sites

302.4.1.5 PAINTING OFSTRUCTURAL STEEL

As fabrication shops can generally apply asuperior paint coat, new structural steel,requiring painting, should have the prime coatshop applied.

This requirement also applies for theapplications of A588M weathering steel whereonly the 3000 mm sections at the end of thestructures or at expansion devices are to bepainted. (Section 302.4.1.1)

302.4.1.5.a TYPES OF PAINTSYSTEMS

The recommended coating system for newstructural steel is the IZEU paint system(Inorganic Zinc, Epoxy, Urethane).

The IZEU paint system should be used for the3000 mm partial painting requirement atexpansion devices of new unpainted A588Msteel superstructure applications.

New steel members being added to widenexisting structures should be painted withIZEU.

If the total existing structure is to be fieldpainted, the existing members should bepainted with the OZEU system (Organic Zinc,Epoxy, Urethane). The OZEU system isbetter for field application as the prime coat ismore forgiving.

Supplemental Specifications 815, for OZEU,and 816, for IZEU, are available.


3-35

302.4.1.5b PAINT SYSTEMS, 3 COATSHOP SYSTEMS

Complete application of all three (3) coats ofpaint at the fabrication shop has beenperformed on some projects. Selected projectshave been those where field access is limited,such as the waterline close to the bottom of thestructure, and large structures. The Office ofStructural Engineering has plan note/specialproposal note for three (3) shop application ofIZEU. (See Appendix)

302.4.1.6 STEEL PIER CAP

Steel pier caps are fracture critical members. Ifthere is no other alternative solution, thepreliminary details of the connection should bereviewed and approved by the Office ofStructural Engineering before completion ofthe detail plans. Structure designs whichrequire stringers to be continuous through, andin the same plane with a steel pier cap or crossbeam, should be avoided if at all possible.

302.4.1.7 OUTSIDE MEMBERCONSIDERATIONS

The designer is to evaluate the actual loads foroutside main members. Heavy sidewalks, largeoverhangs of the concrete deck slab and/or liveloads may cause higher loads on an outsidemember than loads on an internal member.This analysis requirement does not alleviate thedesigner from conforming with AASHTOSection 3.23.2.3.1.4.

In order to facilitate forming, deck slaboverhang should not exceed 1200 mm. Onover the side drainage structures the minimumoverhang shall be 700 mm. Where scuppersare required for bridge deck drainage theoverhang shall be 450 mm.

302.4.1.8 CAMBER ANDDEFLECTIONS

When establishing dead load deflection fordetermining the required shop camber of non-composite steel beam or girder bridges withconcrete deck slabs and determining deckscreed elevations, the weight of curbs,railings, parapets and separate wearingsurface, may be equally distributed to allbeams. Future wearing surfaces shall not beincluded in determining required camber. Thisweight may be assumed (for dead loaddeflection only) to be supported by the beamsacting compositely, based on a moment ofinertia approximately twice that of the beam.Therefore, deflection due to dead loads abovethe deck slab may be based on one-half of theweight distributed to each beam, using thebeam moment of inertia.

When establishing dead load deflection fordetermining the required shop camber ofcomposite beam or girder bridges withconcrete deck slabs and determining deckscreed elevations, the weight of curbs,railings, parapets and separate wearing surfacemay be equally distributed to all beams.Future wearing surfaces shall not be includedin determining required camber.


3-36

The deflection and camber table in the designplans shall detail all points for each beam orgirder line, for the full length of the bridge, ata maximum of 10 meter intervals. Points atmidspan and at splices shall also be detailed inthe deflection and camber table.

In cases of special geometry, i.e. spirals,horizontal or vertical curves, superelevationtransitions, etc., additional points are to bedetailed in the deflection and camber table ifthe normally required points do not adequatelydefine a beam or girder required curvature.

The required shop camber shall in all cases bethe algebraic sum of the computed deflections,vertical and horizontal curve adjustment andshall be measured to a chord between adjacentbearing points.

A camber diagram shall be provided showingthe location of the points developed above andgiving vertical offset dimensions at the bearingpoints from a "Base" or "Work" line betweenabutment bearings.

302.4.1.9 FATIGUE

The following paragraphs are intended toclarify the application of the AASHTO Section10.3 regarding fatigue stresses.

For allowable fatigue stresses reference shall bemade to the AASHTO specifications.

302.4.1.9.a LOADING

In applying loads for fatigue stresses a singlelane of traffic shall be used and positioned toproduce maximum stress ranges in the memberunder consideration.

For service loadings the number and positionof traffic lane units shall conform with theAASHTO specifications, Section 3.11.2.

In computing live load stress ranges forfatigue stresses in structures with concretedecks supported on steel beams a distributionfraction of S/7 shall be used. For serviceloadings the appropriate fractions S/5.5 or S/7shall be used to determine live load bendingmoments. (See AASHTO Section 3.23.2)

To establish the Case of loading for astructure, according to AASHTO Section10.3.2, an estimated Average Daily TruckTraffic shall be determined for the DesignYear. Consideration shall be given to thepotential traffic volumes of the proposedroadway as a result of future industrial orcommercial development.

For steel beam bridges designed for Case Iloading, the intermediate cross frames shall beconnected to the stringers by the use of platestiffeners shop welded to the stringer websand flanges.

302.4.1.9b STRESS CATEGORY

In order not to preclude future rehabilitationinvolving welded attachments, steel memberdesigns in the negative moment regionsshould be limited to an allowable fatiguestress range of Category C, even though shopor field welded attachments are avoided in theoriginal design.


3-37

302.4.1.10 TOUGHNESS TESTS

On steel structures, main load carryingmembers such as beams, moment plates, boltedjoint splice plates (excluding fill plates) requireCharpy V Notch Testing. These componentsshall be identified on the detail plans byplacing "(CVN)" after the component’sdescription.

[Example: W920 x 223 (CVN) ]

The web and all flanges of plate girders shallbe CVN material.

Cross frame members and cross frameconnection stiffeners on horizontally curvedbeam or girder structures are considered mainmembers and shall require and be identified onthe detail plans as CVN.

302.4.1.11 STANDARD END CROSSFRAMES

End cross frames for needed support andreduction of deflection of expansion devicesshould be designed to provide support atintervals not exceeding 1200 mm. Standardexpansion joints have designs alreadyestablished as part of the standard drawings.For suggested details for special conditionsreview existing expansion joint StandardDrawings.

302.4.1.12 BASELINEREQUIREMENTS FORCURVED AND DOG-LEGGED STEELSTRUCTURES

CMS 513 & SS 863 requires the fabricator toinclude in the shop drawings an overall layoutwith dimensions showing the horizontalposition of beam or girder segments withrespect to a full length base or workline.Offsets from this full length base line are to beprovided by the fabricator for each 3000 mmof length. The designer shall provide thisbaseline in the plans along with enoughinformation for the fabricator to be able toreadily calculate the required offsets. Therequirement for this information is especiallycritical on structures located on a curve orspiral or having other complex geometry.

302.4.1.13 INTERMEDIATEEXPANSION DEVISES

Intermediate expansion devices for a structure,if required, shall be located over a pier and thestructural members shall be designed to bediscontinuous at that pier.

302.4.1.14 BOLTED SPLICES

Bolted splices for rolled beams are detailed onStandard Drawing BS-1-93M, sheets 1 thru 4.This Standard incorporates Load Factordesigned beam splices for A36M, A572M orA588M steel materials. The designer isrequired to confirm that the capacity of thestandard splice is greater than the actual loadsfor the designer’s structure.


3-38

For galvanized structures the designer shouldnot specify standard drawing splices. The bolthole size requires a 1.5 mm increase over thestandard drawing’s hole size to allow for theadditional thickness of the zinc coating. Thisincrease in hole size decreases the standarddrawing’s splice capacity. The designer shouldeither evaluate the standard drawing splicebased on the decreased capacity or design anew splice.

Bolt allowable stresses shall be based onAASHTO's values for Class A, ContactSurface, Standard Hole Type.

Beams having bolted splices at bend pointsshall have additional details incorporated in theplans to completely detail the joint require-ments. The minimum edge distances specifiedin AASHTO shall be provided at the edges ofall main members and splice plates.

For splices at bend points the lines of holes inthe beam or girder flanges should be parallel tothe centerline of the web. If the bend angle issmall enough use rectangular splice plates(splice plates should not overhang flange bymore than 13 mm and inside splice platesshould not have to be trimmed to clear web orweb to flange radius). When the angle is toolarge to allow rectangular splice plates theplates should be trimmed to align with theflange edges. In either case minimum edgedistances shall be met.

Bolted compression splices, such as in acolumn, while designed as a friction typeconnection, also require the ends of thespliced members to be in full bearing bymilling of the ends. For compression splicemembers with milled ends the AASHTO re-quirements of Section 10.18.3.1 shall be met.

The designer should recognize that "FULLBEARING" of beams and girders is notdefined by AASHTO. "FULL BEARING"has been generally defined by ODOT as 75percent of the bearing surface in contact andthe other 25 percent with no gap greater than0.8 mm. The designer should recognize thisdefinition when designing in conformance tothe AASHTO design requirements for boltedsplices in compression members.

302.4.1.14.a BOLTS

Field splices in beams and girders shall bebolted connections using high strength bolts,ASTM A-325M.

While the design must specify the size of bolt,the designer should not specify on detail plansthe requirements defining which type, I or III,of A325M bolt to use. These requirements arecovered in the CMS material specifications forA325M bolts.

If a paint system with a zinc based prime coat,OZEU, IZEU or System A, is to be used, thebolts should be galvanized.


3-39

Specifications require the galvanized bolts forIZEU and System A paints. A plan note willbe required to call for galvanized bolts if anOZEU paint system is specified for coatingnew steel. ASTM A325M specifies galvanizedA325M bolts to be type I; therefore the notedoes not need to define type.

If a structure is un-painted A588M, CMS711.09 requires the use of bolts withweathering steel characteristics. A325Mspecifies that A325M, type III bolts meet thatrequirement. No plan note is required.

Generally, bolted splices should be designedusing 25 mm diameter bolts.

The use of A490M bolts is not permitted.

302.4.1.14.b EDGE DISTANCES

When 25 mm diameter bolts are to be usedsplice plates should be detailed to allow for 50mm edge distances in lieu of the AASHTOrequirements.

This increase to AASHTO’s edge distances isto help alleviate the problem fabricators haveof drilling bolt holes in flange splice plates andmaintaining required minimum edge distances,especially on the inside splice plates.

If larger diameter bolts are specified anadditional 6 mm to the AASHTO minimumedge distance shall be used.

302.4.1.14.c LOCATION OF FIELDSPLICES

Generally bolted splices should be located atpoints of dead load contraflecture on acontinuous structure. Splices may also besupplied to help meet shipping and handlinglimitations. Plans should show optional fieldsplice locations.

302.4.1.15 SHEAR CONNECTORS

AASHTO Sections 10.38.2.3 and 10.38.2.4 onstuds shall be followed.

Shear studs shall be automatic welded studs.The use of channel sections is not allowed. 22mm diameter studs are recommended as astandard diameter. The length of studspecified should be checked withmanufacturers as to availability.

The Department’s policy of using a 50 mmdeep haunch over the top flange will have aneffect on the length of shear studs.

302.4.2 ROLLED BEAMS

302.4.2.1 GALVANIZED BEAMSTRUCTURES

If a galvanized bridge structure is the selectedstructure type, the following problems shouldbe recognized and dealt with by the designer.


3-40

Galvanizing tanks are shallow and normallynot longer than 13 700 mm in length.Therefore, beam lengths should not be longerthan 18 500 mm. Before a design iscompleted, the designer should confirm withlocal galvanizers that the structural membersdetailed can be galvanized by a local plant.

Bolted splice designs will require oversizedholes because standard holes partially fill withgalvanizing. Bolted crossframes will berequired due to field installation issues.Standard Drawing GSD-1-96M has boltedcross frame details that may be specified.

Field welding of cross frames is not analternative to bolting because welding intogalvanizing causes damage to the coating thereis not a quality touch-up system developed toadequately handle the repair of damagedgalvanizing for the large quantity of repairswhich would be required .

302.4.2.2 STIFFENERS

Intermediate stiffeners shall only be used whenrequired for cross frames. Stiffeners shall beminimum 10 mm thickness and wide enough tomake an adequate and easily accessible crossframe connection. Stiffeners should not extendbeyond the edge of flange.

Stiffener plates shall have corners in contactwith both web and flange clipped. The clipdimensions shall be 25 mm horizontally and 65mm vertically. Dimensions are shown on STDDRG. GSD-1-96M

Both sides of the stiffener shall be filletwelded to the beam web and both flanges.See STD DRG GSD-1-96M.

302.4.2.3 INTERMEDIATE CROSSFRAMES

Cross frames connections should be to thewebs or intermediate web stiffeners.

Generally cross frames shall not be spacedmore than 7500 mm.

See Standard Drawings GSD-1-96M forstandard cross frame configurations.

Cross frames should be perpendicular tostringers and be in line across the total widthof the structure. Horizontal legs of crossframe angles should align on both sides of abeam.

For structures with flared stringers, crossframes should be attached at the same relativeposition on both sides of the web. Crossframes should also be positioned as follows:

• For flared structures with a differentialangle between individual stringers of 5degrees or less, the cross frames should beperpendicular to one stringer.

• For flared structures with a differentialangle between individual stringers ofgreater than 5 degrees the actualdifferential angle should be divided evenlybetween connections to both stringers.


3-41

• The designer should show the typicalcrossframe details and the maximumspacing in the plans. Actual spacing of thecrossframes should be left to the structuralsteel fabricator’s detailer to allow fordesigner errors and fabrication fit-up. If adesign requires specific location ofcrossframes those crossframe lines shouldbe marked in the plans to not allowadjustment.

A detail showing a completely boltedconnection for cross frame to the steel memberis shown in Standard Drawing GSD-1-96M.

Holes for erection bolts are normally providedin the connection of cross frames to stiffeners.Provide 20 mm holes in cross frames and 18mm holes in stiffeners for 16 mm bolts. SeeGSD-1-96M.

In phased construction of new steel structurescross frames should not be permanentlyattached between phases until all deadload(deck, parapet, etc.) has been applied to themembers. The cross frames can then bepermanently attached and a deck closure pourcan be completed to finish the superstructure.See Section 302.2.9.

For curved or flared bridges with "dog-legged"beams, cross frames should be placed near thebend points. The cross frames should belocated approximately 300 mm from the bendpoint but not interfere with the splice material.The cross frame should be placed normal to thestringer used to set the 300 mm clearancedimension and should be connected to theadjacent stringer only on the same side of thecenterline of beam splice. The cross frame

units should be similar to standard crossframes but should have an additionalhorizontal angle near the top flange of thestringers.

See Figure 319 - Page 3-42 for plan viewlayout of cross frames for dog-legged beams.

Cross frames for curved beams may be similarto the above design but the designer isrequired to confirm that the members and theirconnections meet the additional loadingsdeveloped in a curved member design.

Both doglegged beam cross frames at thedogleg or curved beam cross frames shall beconnected to the beam by use of weldedstiffeners.

302.4.2.4 WELDS

CMS 513 & SS 863 permits welding by thefollowing processes:

• Shielded Metal Arc Welding (SMAW)

• Flux Cored Arc Welding (FCAW)

• Gas Metal Arc Welding (GMAW)

• Submerged Arc Welding (SAW)

Fabricators may choose to use one or more ofthese processes and each process has itsadvantages. Therefore, the designer shouldnot specify the process.


3-43

The designer should specify fillet weld leg sizerequired, in the case of fillet welds, or CP(complete joint penetration) in the case of fullpenetration groove welds. The designer shouldnot select the joint configuration to be used fora full penetration weld. This should be left tothe fabricator and the welding code.

302.4.2.4a MINIMUM SIZE OFFILLET WELD

Fillet welds shall be designed for requiredstresses but should also meet the following sizerequirements: • Minimum size of fillet weld is based on the

thickness of the thicker steel section in theweld joint. The minimum size of fillet weldis defined by AWS D1.5.

• 6 mm leg for up to 19 mm thick material

• 8 mm leg for greater than 19 mm material

302.4.2.4.b NON-DESTRUCTIVEINSPECTION OF WELDS

Non destructive testing (NDT) of welds isdefined in CMS 513 & SS 863. The designershould be familiar with and understand theseNDT requirements and their application.

For any special NDT inspection of unique orspecial welded joints, the designer shouldclarify the NDT requirements with theStructural Steel Section of the Office of

Structural Engineering. A plan note will berequired in the plans defining any specialrequirements.

302.4.2.5 MOMENT PLATES

Fully welded moment plates shall not be usedin areas of tensile stress due to the poorfatigue characteristics. End bolted coverplates, as defined in AASHTO, are acceptablefor use in zones of tensile stress if costeffective. Welded moment plates may beeconomical in the compression flange areasover the piers of continuous span structuresand may be investigated by the designer.Welded moment plates shall not extend into azone where the calculated total stresses aretensile. Details for moment plates should beapproved by the Office of StructuralEngineering.

302.4.3 GIRDERS

302.4.3.1 GENERAL

Multiple designs should be investigated todetermine the most economical. Often adesign with an unstiffened web, eliminatingtransverse stiffeners, is the most economical.A design with a thicker web is also desirablefrom a maintenance standpoint because fieldand shop painting of stiffeners is a problemand is often a locatized point of failure for thecoating system. Fabrication costs should bereviewed with the Department.

Longitudinal stiffeners shall not be used.


3-44

For haunched girders the corner between theflat bottom flange bearing seat area and thecurved section of the bottom flange should bedetailed as two plates with a full penetrationweld.

In applying the above practices, considerationshould also be given to the availability of platelengths. Plates should not be extended beyondthe lengths which can be furnished by therolling mills.

302.4.3.2 FRACTURE CRITICAL

This section is not intended to recommendfracture critical designs. The designer shouldmake all efforts to not develop a structuredesign which requires fracture criticalmembers.

Fracture critical members are defined inSection 2, Definitions, of the AASHTO/AWSD1.5, chapter 12 Fracture Control Plan.

If a bridge design includes any members ortheir components which are fracture critical,those members and components should beclearly identified as FRACTURE CRITICALMEMBERS (FCM) in the plans. Fracturecritical welds shall also be designated.

A plan note shall be added requiring all FCM’sto be subject to the AASHTO/AWS D1.5,chapter 12, Fracture Control Plan for FractureCritical Non-redundant Steel Bridge Members,latest edition, and welding requirements ofCMS 513 and/or 863.

If a girder is non-redundant, include the entiregirder in the fracture critical steel payquantity. The designer’s required plan noteshall state which parts of the girder, and whichwelds, are actually subject to the fracturecontrol plan.

302.4.3.3 WIDTH & THICKNESSREQUIREMENTS

302.4.3.3.a FLANGES

In addition to design limitations of width tothickness, flanges shall be wide enough thatthe girder will have the necessary lateralstrength for handling and erection. Anempirical rule is that the minimum width oftop flange should be:

W = dw/6 + 65 Round up to the next 25 mm dw = web depth, mm

W = flange width, mmBut not less than 300 mm width.

The minimum thickness for any girder flangeshall be 22 mm.

Generally, selection of flange thicknessesshould conform to the following:

• 22 to 76 mm thick - in even 2 mmincrements.

• Greater than 76 mm thickness - in 5 mmincrements.


3-45

Whenever possible use constant flange widthsthroughout the girder.

In the design of welded steel girders, thethickness of the flange plates is varied alongthe length of the girder in accordance with thebending moment. Each change in platethickness requires a complete penetration butt-weld in the flange plate. These butt-welds arean expensive shop operation requiring con-siderable labor. In determining the pointswhere changes in plate thickness occur, thedesigner should weigh the cost of butt-weldedsplices against extra plate thickness. In manycases it may be advantageous to continue thethicker plate beyond the theoretical stepdownpoint to avoid the cost of the butt-weldedsplice.

In order to help make this decision, guidelinesproposed by United States Steel in theirpamphlet "Fabrication - Its Relation to Design,Shop Practices, Delivery and Costs" may beused. The amount of steel that must be savedto justify providing a welded splice should beas follows:

• A36M steel 135 kg + (0.0175 kg X cross sectional area,in mm2, of the lighter flange plate).

• For 345 MPa steels, A588M & A572M, thecutoff point is 85 percent of the value forA36M steel.

302.4.3.3.b WEBS

The minimum web thickness shall be 10 mm.

See Section 302.4.3.1 for recommendations onuse of unstiffened web designs.

302.4.3.4 INTERMEDIATESTIFFENERS

Intermediate web stiffeners shall be minimum10 mm thickness. Stiffeners that extendbeyond the edge of flange shall be clipped ata 45E angle. All intermediate stiffenersshould be the same size.

Where intermediate stiffeners are to be usedfor the purpose of stiffening the web, it ispreferable to use single stiffeners on alternatesides of the web of interior girders and onlythe inside of the web for facia girders.

Stiffeners shall be provided for the attachmentof cross frames and both ends of the stiffenershall be welded to the flanges to helpeliminate cracking of the web due to out ofplane bending. Both sides of the stiffenershall be fillet welded to the girder web andcompression flange. Cross frame stiffenersshall be welded to the girder web and bothflanges. The designer must investigate thatfatigue criteria is met in these areas.

Stiffener plates shall have corners in contactwith both web and flange clipped. The clipdimensions shall be 25 mm horizontally and65 mm vertically.


3-46

For details of stiffeners see Standard DrawingGSD-1-96M.

302.4.3.5 INTERMEDIATE CROSSFRAMES

Connection of cross frames should be made tothe intermediate web stiffeners. This isnormally done by field welding.

Generally cross frames shall not be spaced atmore than 7500 mm.

See Standard Drawing GSD-1-96M forstandard cross frame details.

In phased construction of new steel structurescross frames should not be permanentlyattached between phases until all deadload(deck, parapet, etc.) has been applied to themembers. Then the cross frames can bepermanently attached and a deck closure pourcan be completed to finish the superstructure.See Section 302.2.9.

On skewed structures, when the differentialdead load deflection of adjacent girders at anyintermediate cross frame location is 13 mm ormore, the erection bolt holes in the cross framemembers should be detailed as 40 x 18 mmlong slotted holes for 16 mm diameter bolts.The slotted holes shall require a 8 mm thickstructural plate washer placed over them. Finalbolting, and the welded connection, shall notbe completed until after the deck concrete hasbeen placed.

For curved or flared bridges with "dog-legged" girders, cross frames should be placednear the bend points. The cross frames shouldbe located approximately 300 mm from thebend point so as not to interfere with thesplice material. The cross frame should beplaced normal to the girder used to set the 300mm clearance dimension and should beconnected only to the stringer on the sameside of the centerline of girder splice. Theyshould be similar to standard cross frameswith an additional horizontal angle near thetop flange of the stringers.

See Figure 319 - Page 3-42 for plan viewlayout of cross frames for dog-leggedmembers.

Cross frames for curved girders may besimilar to the above design but the designer isrequired to confirm the members and theirconnections meet the additional loadingsadded due to curved member designs.

302.4.3.5.a ERECTION BOLTS

For plate girder bridges, erection bolts shall beprovided in the connections of cross frames togirder stiffeners. All bolt holes in stiffener andcross frames should be detailed as 4 mmlarger than the erection bolts. Erection boltsare normally 16 mm diameter.

302.4.3.6 WELDS

CMS 513 & SS 863 permits welding by thefollowing processes:


3-47

• Shielded Metal Arc Welding (SMAW)

• Flux Cored Arc Welding (FCAW)

• Gas Metal Arc Welding (GMAW)

• Submerged Arc Welding (SAW)

Fabricators may choose to use one or more ofthese processes and each process hasadvantages. Therefore, the designer should notspecify the process.

The designer should specify fillet weld leg sizerequired, in the case of fillet welds, or CP(complete joint penetration) in the case of fullpenetration groove welds. The designer shouldnot select the joint configuration to be used fora full penetration weld. This should be left tothe fabricator and the welding code.

For full penetration welds splicing flangematerials or web materials a plan note shouldbe added requiring removal of the weldreinforcement by grinding in the direction ofthe main stresses. The removal ofreinforcement improves fatigue characteristicsand makes NDT interpretation easier.

302.4.3.6.a TYPES

There are generally two (2) types of weldsacceptable for bridge fabrication, fillet andcomplete penetration welds.

302.4.3.6.b MINIMUM SIZE OFFILLET ANDCOMPLETEPENETRATION WELDS,PLAN REQUIREMENTS

Fillets welds shall be designed for requiredstresses but should also meet the followingsize requirements:

• Minimum size of fillet weld is based onthe thickness of the thicker steel section inthe weld joint. The minimum size of weldis defined in AASHTO/AWS D1.5.

• 6 mm leg for up to 19 mm thick material

• 8 mm leg for greater than 19 mm thickmaterial

Complete or full Penetration welds are bydefinition welded through the full section ofthe plates to be joined. No partial penetrationwelds are acceptable for use except insecondary members not subject to tension orreversal stresses.

The designer should specify either fillet weldleg size, in the case of fillet welds, or CP(complete penetration) for complete jointpenetration groove welds. The designer shouldnot detail actual complete penetration weldedjoints symbols but only show the requirementthat the welded joint be Complete JointPenetration, CP.

Inspection and acceptance of a completepenetration weld is based on whether the weldwill be loaded in tension or compression. Inorder to utilize this permissible qualitydifference between welds subjected to only


3-48

compression or tension stresses, detail plans forsteel girders should designate all flange buttwelds which are subjected to compressivestresses only. This designation should be madeby placing the letters "CS" next to fullpenetration welds shown on detail drawings.The following explanatory legend should beplaced on the same detail sheet:

CS - indicates butt weld subject tocompressive stresses only.

302.4.3.6.c INSPECTION OF WELDS,WHAT TO SHOW ONPLANS

Non destructive testing (NDT) of welds isdefined in CMS 513 and/or 863. The designershould be familiar with and understand theseNDT requirements and their application.

For any special NDT inspection of unique orspecial welded joints, the designer shouldclarify the NDT requirements with theStructural Steel Section of the Office ofStructural Engineering. A plan note for anyspecial requirements shall be necessary in thedesign plans.

On railroad bridges, when full penetration webto flange welds are specified, the designershould add a note requiring 50 percentultrasonic inspection. (The designer shouldcheck the AREA specifications and with theactual railroad to confirm the individualrailroad’s requirements for NDT of welds.)

302.5 PRESTRESSEDCONCRETE BEAMS

302.5.1 BOX BEAMS

Physical dimensions and section properties ofbox beam cross sections shall be as shown onStandard Drawing PSBD-1-93M.

Box beams should be limited to a maximumskew of 30 degrees.

Box beam sizes should be limited so the totalweight of transport vehicle and member donot exceed a maximum weight of 54 500 kg.

Multiple span box beam bridges shall bejoined over the piers with a T-joint perStandard Drawing PSBD-1-93M. Structurallythe beams shall be designed as simple spans.

Expansion at the piers shall be accommodatedby elastomeric expansion bearings or byflexibility of the piers if integral design.

The length of abutment seats of prestressedconcrete box beam bridges should be longenough to accommodate the total width out-to-out of all beams including a fit-upallowance of 12 mm per joint between beams.

In order to keep the beam seat from extendingbeyond the facia of any pier of a box beambridge, the length of the pier seat should onlyinclude a fit-up allowance for the jointsbetween the beam of 6 mm per joint.


3-49

For box beam bridges which have skewcombined with grade or which have variablesuperelevation, beam seats shall be designedand dimensioned to provide support for the fullwidth of the box beams.

If a bridge structure’s geometrics cause a bridgedeck in an individual span to have a differentcross slope at one bearing than at the otherbearing, the difference should be evenlydivided so that the box beam seat cross slopesat both bearings are made to be the same. Thisadjustment gives the box beam full support atthe seat without creating any twist or torsion onthe box beam. Any elevation differencescreated by this beam seat adjustment should beadjusted for in the overlay, whether asphaltic orconcrete.

Prestressed box beam members shall besupported by two bearings at each support.

Abutment wingwalls above the bridge seat andbackwalls should not be cast until after boxbeams have been erected. The cast in placewingwall and box beam should normally beseparated by 25 mm joint filler, CMS 705.03.The designer should show both requirements inthe plans. Not casting the backwall andwingwalls until after the box beams are erectedallows the actual box beam fit-up height andwidth variances to not create installationproblems with the joint filler and also helpprevent spalling of the concrete backwall andwingwall due to movements of the elastomericbearings.

For box beam bridges with steel railing, thepost spacing and position of post anchorageshall be detailed on the plans. The designershall check that the post anchor spacing doesnot interfere with tierod locations or the "T"joint over the pier. The designer shouldconfirm that post anchors at the ends ofskewed box beams have both adequateconcrete cover and do not interfere with thetierods. If the designer finds that no postspacing option can comply with the aboverequirements, the option of relocating the tierods may be chosen. See standard drawingsfor maximum allowable spacing of tie rods.

302.5.1.1 DESIGN LOADS AND LOADDISTRIBUTION FACTORS

For both Service Load and Strength DesignMethods, AASHTO’s Table 3.22.1A (Liveload and Impact) beta factors shall beincreased by a factor of 1.25.

For box beam members, the live loaddistribution factors of AASHTO Section3.23.4.3 shall be used.

302.5.1.2 STRANDS

Debonding of strands, by an approved plasticsheath, shall be done to control stresses at theends of the beams.

Deflecting of strands in box beams to limitstresses shall not be allowed.


3-50

The designer shall show on the plans thenumber, spacing and length of debonding. Thebox beam fabricator may have the option tochange the position of debonding as long as thechange is still symmetrical.

Prestressed box beam design data sheets forPSBD-1-93M are based on the use of low lax12.7 mm (99 mm2) strand. These design datasheets do not reflect the increase in beta factorsunder section 302.5.1.1.

Strands extended from a beam to developpositive moment resistance at pier locationsshall not be debonded strands.

302.5.1.2.a TYPE, SIZE OF STRANDS

• Low-relaxation 12.7 mm diameter (As=99mm2) seven wire uncoated strands, ASTMA416, Grade 270.


302.5.1.2.b SPACING

Strands shall be spaced at increments ormultiples of 50 mm.

Location of the centerline of the first row ofstrands shall be 50 mm from the bottom of thebeam. Rows of strands should also have aminimum clearance of 50 mm from the side ofthe beam and preferably 100 mm, if possible.

302.5.1.2.c STRESSES

Initial prestressing loads for low-relaxationstrand shall be as per AASHTO requirementsand shall be detailed on the plans.

Initial stress .75 f's = 1400 MPa

Initial tension load 137 800 N/strand

Stress at release .69 f's = 1285 MPa

Total losses expressed by

Fs = SH + ES + CRc + CRs

Fs = 77.07 + 18.0 fcir - 6.65 fcds

302.5.1.3 COMPOSITE

Composite reinforced deck slabs onprestressed box beams shall be a minimum of155 mm thick and shall be reinforced with No.19M bars, spaced 450 mm longitudinally and225 mm transversely.

On multiple span composite box beam bridgesadditional No. 19M longitudinal reinforcingsteel over the piers shall be required. The No.19M bars shall be alternately spaced with thestandard longitudinal reinforcement and thepier bar's length shall be 40 percent of thelongest adjacent span. The pier bars should beplaced longitudinally and approximatelycentered on the pier but with a 1000 mmstagger.


3-51

For box beam structures with composite decksand concrete parapet and/or sidewalks withconcrete railing the finished roadway widthshould not incorporate fit up tolerances. Tocompensate for fit-up tolerances the compositedeck and barrier and/or sidewalk should bedesigned to cantilever or overhang theboxbeam units by 50 mm to 200 mm each sidewith the fit-up being absorbed in the overhang.A mixture of 1220 mm and 915 mm boxbeamunits may be necessary to meet thisrequirement.

See Figure 320 - Page 3-52 for a sketch of thecross-section of the composite decksuperstructure.

302.5.1.4 NON-COMPOSITEWEARING SURFACE

Non-composite box beam bridges with asphaltoverlays shall have either a waterproofingmembrane as per CMS 512, type D, or a sheetwaterproofing membrane, type 3, placed on theboxes before the 32 mm minimum layers ofCMS type 448 asphaltic concrete is applied.(See section 302.1.1.2.a)

Non-composite box beam bridges with asphaltoverlays shall be limited to a 4 percentcombined grade. Combined grade includesboth the longitudinal and transverse structuregrades.

Combined Grade Cg = ([deck slope]2 +

[transverse grade]2)½

Combined grades greater than 4 percentrequire a composite deck design.

302.5.1.5 CAMBER

In establishing bridge seat elevations andassuring a minimum design slab or overlaythickness, allowance shall be made for camberdue to prestressing as per the following:

A = Design slab thickness

B = Anticipated total camber in the beam= established by design [estimated = 2 x initial (elastic)camber at transfer plus 6 to 12 mm]

C = Adjustment for vertical curve.Positive for crest vertical curve

D = Deflection at mid span - due to deadload of slab, curbs, parapets andsidewalk.

E = Slab depth at beam bearings = A + B -C - D If crest vertical curve correction [C] isgreater than [B-D] design slabthickness [A] will control.

F = Anticipated slab depth at mid-span =A If crest vertical curve correction [C] is(B - D) Then F = A - B + C + D

The designer shall show a longitudinalsuperstructure cross section in the plansdetailing the required thicknesses of the deck,deck components, or slab at centerline ofspans, piers and abutments.


3-53

302.5.1.6 ANCHORAGE

In a box beam design all beams shall beanchored at abutments and piers. The anchorshall be in the center of the cross section of thebox beam and shall conform to StandardDrawing PSBD-1-93M.

Fixed end anchor dowels shall be installed witha non-shrinking grout (mortar). Expansion endanchor dowel holes shall be filled with jointsealer, CMS 705.04.

Preformed expansion joint 705.03, the samethickness as the elastomeric bearing, shall beinstalled under the box beam, around theanchor dowel, to halt the grout or sealer fromleaking through to the beam seat.

302.5.1.7 CONCRETE MATERIALS BOX BEAMS

Design Concrete Strength of shop fabricatedprestressed members = 38.0 MPa at 28 days.

Cast-in-place concrete, (composite decks, pier"T" sections, I- beam diaphragms, etc.) Class Ssuperstructure concrete - 31.0 MPa at 28 days.

For concrete in composite decks see Section302.1.1.1.

302.5.1.8 REINFORCING

Epoxy coated reinforcing steel shall be used incomposite deck slabs and shall be Grade 420,Fy= 420 MPa.

Reinforcing steel used in the standard designbox beams is Grade 420 Fy=420 MPa.

The fabricator, by specification, is required touse a corrosion inhibiting admixture in theconcrete. Reinforcing bars projecting fromthe prestressed members shall be epoxycoated.

Stirrups in boxbeams should completelyenclose the majority of the prestressingstrands.

302.5.1.9 TIE RODS

Tie rods shall be provided and installed as perStandard Drawing PSBD-1-93M.

Diaphragms and transverse tie rods forprestressed concrete box beam spans shall beprovided at midspan for spans up to 15 000mm, at third points for spans from 15 000 mmto 23 000 mm and at quarter points for spansgreater than 23 000 mm.

302.5.2 I BEAMS

AASHTO standard prestressed I-beam shapes,type II through type IV and modified type IV,as shown in standard drawing PSID-1-95M,shall be used.

Modified cross sections other than those onstandard drawing PSID-1-95M should only beused after reviewing this option with theOhio/Indiana/Kentucky Prestressed ConcreteInstitute and with approval of the Office ofStructural Engineering.


3-54

In designing prestressed I-beams, the non-composite section shall be used for computingstresses due to the beam and deck slab. Thecomposite section shall be used for computingstresses due to the superimposed dead, railingand live loads.

302.5.2.1 DESIGN LOADS AND LOADDISTRIBUTION FACTORS

For both Service Load and Strength DesignMethods, AASHTO’s Table 3.22.1A (Liveload and Impact) beta factors shall be increasedby a factor of 1.25.

Prestressed I-beam load distribution factorsshall conform to AASHTO

302.5.2.2 STRANDS

Preferably, straight strands should be used.Debonding of a maximum of 25% the numberof strands in the I-beam, with an approvedplastic sheath, may be done to relieve excessivestresses. More than 25% of the strands can bedebonded if it can be shown that the appliedmoment is less than the cracking moment in thetransistion zone at ultimate load. The numberof debonded strands in any horizontal rowshould not exceed 40% of the strands in thatrow.

Any use of draped strands shall first beapproved by the Office of StructuralEngineering.

The designer shall show on the detail plans thenumber, spacing and the length of requireddebonding per strand, if any.

Strands extended from a beam to developpositive moment resistance at pier locationsshall not be debonded strands.

302.5.2.2.a TYPE, SIZE

• Low-relaxation 12.7 mm diameter (As=99mm2) seven wire uncoated strands, ASTMA416, Grade 270, shall be used


Other, larger diameter, sizes of strands may bespecified with approval of the Office ofStructural Engineering.

302.5.2.2.b SPACING

Strands shall be spaced at increments of 50mm.

A minimum 50 mm dimension from bottomof beam to centerline of the first row ofstrands and any exterior beam surface shallalso be maintained.


3-55

302.5.2.2.c STRESSES

Initial prestressing loads for low-relaxationstrand shall be as per AASHTO requirementsand shall be detailed on the plans.

Initial stress .75 f’s = 1400 MPa

Initial tension load 137 800 N/strand

Stress at release .69 f’s = 1285 MPa

Total losses expressed by Fs = SH + ES + CRc + CRs

Fs = 77.07 + 18.0 fcir - 6.65 fcds

302.5.2.3 CAMBER

A haunch shall be required in the deck toaccount for the I-beam’s maximum camber dueto design prestressing.

In establishing bridge seat elevations andassuring a minimum design slab thickness,allowance shall be made for camber due toprestressing as per the following:

A = Design slab thickness

B = Anticipated total camber in the beam =established by design

C = Adjustment for vertical curve.Positive for crest Vertical curve

D = Deflection due to dead load of slab,diaphragms, curbs, sidewalks andparapets.

E = Design Haunch Depth (minimum 50mm)

F = Slab depth at beam bearings = A + B -C - D + E If crest vertical curve correction [C] isgreater than [B-D] design slabthickness [A+E] will control.

G = Anticipated slab depth at mid-span =A + EIf crest vertical curve correction [C] is(B - D) Then G = A - B + C + D + E

The designer shall show a longitudinalsuperstructure cross section in the plansdetailing the required thicknesses of the deck,deck components, or slab at centerline ofspans, piers and abutments.

302.5.2.4 ANCHORAGE

25M dowel anchors shall be provided at eachfixed pier as per STD DRG PSID-95M

Minimum number of anchors shall be 2 foreach beam line.


3-56

The anchors shall be a minimum of 600 mmlong. Anchors shall be embedded a minimum300 mm into the pier cap and 300 mm into thefield cast-in-place concrete pour whichconnects any two discontinuous prestressed I-beams in the same beam line into a continuousmember. The anchors should be drilled inplace at the centerline of the pier between theends of adjoining prestressed I-beams. Thedesigner should confirm the pier cap hasreinforcing steel clearance to accept theseanchors.

302.5.2.5 DECK SUPERSTRUCTUREAND PRECAST DECKPANEL

It is recommended that only cast-in-placeconcrete decks, Class S or High PerformanceConcrete be designed and used.

The precast panel alternative, previously used,has shown cracking problems at the jointsbetween the panels and there are questions onthe transfer of stresses in the finished decksections.

302.5.2.6 DIAPHRAGMS

Maximum spacing of intermediate diaphragmsshall be 12 000 mm.

Intermediate diaphragms should not makecontact with the underside of the deck becausethey could act as a support to the deck, causingcracking and possible over stressing of the

deck. The top of the intermediate diaphragmshould start at the bottom vertical edge of thetop flange and end at the top of the verticaledge of the bottom flange. Refer to standarddrawing PSID-1-95M for typical diaphragmand reinforcing details.

Intermediate diaphragms of galvanized steelmay be used if approved by the Department.

The designer shall add a note to the plans forprestressed I-beam designs requiring theintermediate diaphragms to be placed andcured at least 48 hours before deck placement.

I-beam designs should include threaded insertdetails for dowels/reinforcement to alloweasier installation of cast-in-place diaphragms,to allow transfer of loads and to help protectthe diaphragms against cracking. Thethreaded inserts and the threaded rods shall begalvanized as per CMS 711.02

End diaphragms shall be provided.Diaphragms shall be cast-in- place. The top ofthe end diaphragm shall make completecontact with the deck. The bottom of the enddiaphragm shall end at the top vertical edge ofthe bottom flange. The bottom of the dia-phragm shall not extend down to the bottomof the I-beam’s bottom flange. Refer tostandard drawing PSID-1-95M for typicaldiaphragm details.


3-57

302.5.2.7 DECK POURINGSEQUENCE

A deck pour sequence is required for allprestressed I-beam designs made continuous atpier locations. Standard drawing PSID-1-95Mestablishes one sequence. The designer shouldeither accept the standard drawing sequence ordetail an alternative.

302.5.2.8 CONCRETE MATERIALSI-BEAMS

Design Concrete Strength of shop fabricatedprestressed members = 38.0 MPa at 28 days.

Cast-in-place concrete, (composite decks, pier"T" sections, I- beam diaphragms, etc.) Class Ssuperstructure concrete - 31.0 MPa at 28 days.

Higher concrete strengths may be specifiedwith approval of the Office of StructuralEngineering.

302.5.2.9 REINFORCING

Unless otherwise specified all reinforcing steelused shall be epoxy coated, Grade 420 Fy=420MPa.

The fabricator, by specification, is required touse a corrosion inhibiting admixture to theconcrete. Reinforcing bars projecting from theprestressed members shall be epoxy coated.

Reinforcing steel stirrups shall completelyenclose the strands for the entire length of thebeam.

For composite designs the total amount oflongitudinal reinforcing steel over the piers,for the deck slab shall be determined inaccordance to AASHTO.

303 SUBSTRUCTURE

303.1 GENERAL

If a pier column, wall or other structuralmember is located in the sloped portion of anembankment, it shall be assumed that inaddition to the earth pressure due to theembankment directly in back of the member,there also will be earth pressure due to theadjacent embankment on each side.

The minimum design earth pressure shall be2.0 kPa unless granular backfill is provided.

303.1.1 SEALING OFCONCRETE SURFACES,SUBSTRUCTURE

Specifications for the sealer can be found in aproposal note. Concrete surfaces shall besealed with a concrete sealer as follows:

The front face of non-integral abutmentbackwalls, from top to bridge seat, thebridge seat and the breastwall down to thegroundline shall be sealed with an epoxy-urethane or non-epoxy sealer. (note: Sealingof the backwall shall not be required onprestressed box beam bridges because thebeams are installed before the backwall isplaced.)


3-58

The exposed surfaces of all wingwalls andretaining walls, exclusive of abutment type,that are within 10 000 mm of any pavementedge shall be sealed with an epoxy-urethanesealer.

Ends and sides of piers exposed to traffic-induced deicer spray, from any direction,shall be sealed with either an epoxy-urethaneor non-epoxy sealer. Top of pier caps needonly be sealed if there is an expansion jointor the tops are subject to exposure to deicerladen water.

The total vertical surface of piers which areadjacent to traffic lanes shall be sealed witheither an epoxy-urethane or non-epoxy sealer.Structures of A-588M weathering steelsuperstructures shall also have their pierssealed as stated above with either an epoxy-urethane or non-epoxy sealer.

The designer should include in the plans actualdetails showing the position, location and arearequired to be sealed. A plan note to describethe position should not be used as there can beboth description and interpretation problems.

The designer has the option to select a specifictype of sealer, epoxy-urethane or non-epoxy.The designer also has the alternative to just usea bid item for sealer, with no preference, andallow the contractor to choose based on cost.

See Figures 321, 322 & 323 - Pages 3-59, 3-60& 3-61

303.2 ABUTMENTS

303.2.1 GENERAL

Abutments should be provided with backwallsto protect the superstructure from contact withthe approach earth fill and to assist inpreventing water from reaching the bridgeseat.

For members designed to retain earthembankments and are restrained fromdeflecting freely at their tops as in a rigidframe bridge, abutment walls keyed to thesuperstructure, and some types of U-abutments, the computed backfill pressureshall be determined by using at rest pressure.

For abutment walls of structures designedwithout provision for expansion betweensuperstructure and substructure and where anappreciable amount of superstructureexpansion is anticipated, passive earthpressure should be considered in the design.

To allow for slight tilting of wall typeabutments after the backfill has been placed,batter the front face 5 mm for each 1000 mmof abutment height. Height is measured frombottom of footing to the roadway surface.

303.2.1.1 PRESSURE RELIEFJOINTS FOR RIGIDPAVEMENT

If rigid concrete pavement or base is to beused adjacent to the structure, the designershall confirm that the roadway plans requireinstallation of type A pressure relief joints, asper Standard Construction Drawing BP-2.3M.


3-62

Pressure relief joints are required to alleviatebackwall pressures on abutments withexpansion devices and to allow freedom ofmovement for integral and semi-integralabutments.

303.2.1.2 BEARING SEAT WIDTH

For all continuous slab bridges, the approachslab seat and the bridge slab seat should beplaced at the same elevation by providing ahaunch on the thinner slab.

For continuous or simple span beam or girderstructures the abutment seat width should be600 mm. Centerline of bearing should be 300mm from face of backwall. Exceptions to thispractice may be necessary for highly skewedstructures.

The configuration for prestressed I-beamabutment bearing seat widths is similar to thosefor the steel beam or girder. The seat widthwill vary due to size of elastomeric bearing,prestressed I-beam flange width and thestructure’s skew.

Abutment bearing seat widths for prestressedbox beams without expansion devices isnormally 400 mm with centerline of bearing225 mm from face of breast wall. The seatwidth for prestressed box beams withexpansion devices is increased with centerlineof bearing still 225 mm from face of breastwall.

AASHTO seismic seat width requirements,based on length and height of structure, mayrequire additional seat width. All definedabutment bearing seat widths can be affecteddue to special considerations for a specificstructure or type of bearing. See Section301.3.1 of this Manual.

303.2.1.2.a BEARING SEATREINFORCEMENT

Bearing areas of abutments may requiresupplementary reinforcement to resist localcompressive and shearing stresses.

The location and spacing of all reinforcing inbridge seats should be chosen to provideadequate clearance for bearing anchorswhether pre-set or drilled in place. Thedesigner should recognize drilled in placeanchors use larger holes than the actualanchor.

A note shall be provided on the substructuredetail sheets cautioning the contractor toplace the reinforcing to avoid interferencewith the anchor bolts. Also a "BearingAnchor Plan" to adequately show the locationof the bearing anchors with respect to themain reinforcing bars and the edges of thebridge seats shall be provided.


3-63

303.2.2 TYPES OF ABUTMENTS

303.2.2.1 ABUTMENTS, FULLHEIGHT

If the computed horizontal forces at the bottomof the full height abutment footing cannot becompletely resisted by the friction of thesubsoil, by the action of vertical and batteredbearing piles, or drilled shafts, or by footingkeys, steel sheet piling rigidly attached to thefooting may be used to provide additionalresistance. See section 303.4.1.1

The minimum projection of the steel sheetpiling below the bottom of the footing shall be1.5 meters. If the sheet piling is placed in frontof battered bearing piles, it also should bespecified to be battered.

Where these short lengths of steel sheet pilingare used, the sheet piles should be anchored tothe face of the toe of the footing by not lessthan two No. 19M reinforcing bars attachednear the top of each sheet pile and includedwith the sheet piling for payment. The No.19M bars shall be long enough to be fullydeveloped in bond.

If a 1500 mm projection of sheet piling belowthe bottom of the footing is found to besufficient, the piles should have a minimumsection modulus of 375 000 mm3 per meter ofwall. For other lengths of sheet piling theminimum required section modulus should becomputed. The plans shall show the minimumrequired section modulus. See plan notesSection 700.

Vertical rustications may be provided at 1200mm centers to fit the width of standardplywood forms or liners.

An alternate to vertical rustications is the useof form liners to provide the wall surface withan aesthetic appearance. While a variety offormliners are available the following criteriashould be met:

• Formliners should not be used when theywill not be visible to the public.

• The selected pattern of formliner shouldbe easily visible from a distance. Smallor ornate patterns not easily visible froma distance do not enhance the structureand are not cost effective.

• Minimum cover requirements forreinforcing steel must be met. If aformliner is used minimum concretecover shall not be violated by patterns orindents of the formliner. This willrequire additional concrete and in somecases dimensional changes.

• The cost of formliners selected shouldadd only minimal additional cost to theoverall cost of the concrete (1 to 3percent per meter of the abutment, pier orwall)

• Generic formliner patterns shall bespecified. An alternative of at least threesuppliers listed. Listing of a formlinerpattern only available from one supplierwill not be accepted.


3-64

303.2.2.1.a COUNTERFORTS, FULLHEIGHT ABUTMENTS

For full height abutments exceeding 10 000mm in height, counterforts should beconsidered.

Reinforcing steel in the back, sloping, face ofthe counterfort should be placed in two rowswith 150 mm clearance between rows.Reinforcing steel splices should be staggered aminimum of 1000 mm, by row.

Reinforcing extending from the footing of acounterforted wall into the highly reinforcedareas of the counterforts shall have reinforcingsteel splices staggered.

In counterforted walls, each pocket formed bythe intersection of the counterfort and wallshall be drained.

303.2.2.1.b SEALING STRIP, FULLHEIGHT ABUTMENTS

Use an impervious fabric across the expansionjoints in full height abutments or retainingwalls to eliminate leakage. The imperviousfabric should be CMS 512 Sheet Type 2waterproofing, 1000 mm wide, centered over,and extending the full length of the joint to thetop of the footing. See Section 303.2.5 onrequirements for expansion joints in abutments.

303.2.2.2 CONCRETE SLABBRIDGES ON RIGIDABUTMENTS

For a continuous concrete slab bridgesupported on rigid abutments, the joint betweenthe deck slab and the top of the abutment shall

be troweled smooth and a continuous strip ofelastomeric material shall be recessed into theabutment seat before placement of thesuperstructure concrete.

The above bearing system for slabs on rigidabutments should conform with temperaturemovement and bearing design requirements ofthis Manual.

303.2.2.3 STUB ABUTMENTSWITH SPILL THRUSLOPES

If a stub abutment is to support a bridgehaving provision for relative movementbetween the superstructure and the abutment,two rows of piles are required and the frontrow shall be battered 1:4.

Where two rows of piles are used, the forwardrow shall have approximately twice thenumber of piles as the rear row, with the rearpiles placed directly behind alternate frontpiles.

The perpendicular distance from the surface ofthe embankment to the bottom of the toe ofthe footing should be at least 1200 mm. Ifconcrete slope protection is being provided theperpendicular distance required can bereduced to a minimum of 1000 mm.

The maximum spacing of piles in a single rowor in the front row of a double row shall be2500 mm.

For phased construction projects no abutmentphase shall be designed to be supported onless than three (3) piles or two (2) drilledshafts.


3-65

303.2.2.4 CAPPED PILE STUBABUTMENTS

For capped pile stub abutments which do notprovide for relative movement between thesuperstructure and the abutment, one row ofvertical piles shall be used.

The construction joint at the top of the footingfor cap pile abutments should be shown asoptional.

For phased construction projects no abutmentphase shall be designed to be supported on lessthan three (3) piles or two (2) drilled shafts.

303.2.2.5 ABUTMENTS, SPREADFOOTING TYPE

Where foundation conditions warrant the use ofan abutment on a spread footing, the bottom ofthe footing should be at least 1200 mm belowthe surface of the embankment.

The perpendicular distance from the surface ofthe embankment to the bottom of the toe of thefooting should be at least 1200 mm. Ifconcrete slope protection is being provided theperpendicular distance required can be reducedto a minimum of 1000 mm.

In no case shall the top of the footing be lessthan 300 mm below the surface of theembankment.

303.2.2.6 INTEGRAL ABUTMENTS

Integral Abutment use is limited as defined inSection 200 of this Manual. Integral designshould not be used with curved main membersor main members which have bend points inany stringer line.

For an integral design to work properly, thegeometry of the approach slab, the design ofthe wingwalls, (see section 303.2.4) and thetransition parapets must be compatible withthe freedom required for the integral (beams,deck, backwall, wingwalls and approach slab)connection to rotate and translatelongitudinally.


The horizontal and vertical joint shall besealed at the back face of the backwall by useof a 900 mm wide sheet of nylon reinforcedneoprene sheeting. The sheeting should onlybe attached on one side of the joint to allowfor the anticipated movement of the integralsection. The sheeting shall be secured by theuse of 32 x 3 mm (length x shank diameter)galvanized button head spikes at 225 mm C/Cmax. through a 25 mm outside diameter, 3mm thick galvanized washer. A note for theneoprene sheeting is available in the section600 and the requirements are also shown onstandard Drawing ICD-1-82M.

Integral abutments shall be supported on asingle, row of parallel piles. If an integralabutment design uses steel H piles, they shallbe driven so the pile’s web is parallel to thecenterline of bearing.


3-67

For phased construction projects no abutmentphase shall be designed to be supported on lessthan three(3) piles.

Phased construction integral backwall detailsshall have a closure section detailed betweensections of staged construction to allow fordead load rotation of the main beams orgirders.

Standard Drawing ICD-1-82M shows detailsfor integral abutments with a steel beam orgirder superstructure. Cantilevered or turnbackwingwalls shall not be used with integralabutments.

303.2.2.7 SEMI-INTEGRALABUTMENTS

This abutment design is appropriate for bridgeexpansion lengths up to 80 meters or 125meters total length of structure. Semi- integralabutments require foundation types that arefixed in position (a single row of piles shall notbe used). The expansion and contractionmovement of the bridge superstructure isaccommodated at the end of the approach slab. Semi-integral design should not be used withcurved main members or main members whichhave bend points in any stringer line.

The expansion length for a semi-integralstructure is considered to be (2/3) two thirds ofthe total length of the structure.

Where an existing structure is beingrehabilitated into a semi-integral abutmentdesign, the designer should investigatewhether the existing fixed bearings and pierscan accept the stresses due to the differentialmovement caused by the concept ofmovement for semi-integral abutment designs.

Semi-integral details can be used on wall typeabutments, spill-thru type abutments on two ormore rows of piles, spread footing typeabutments or abutments on drilled shafts.

This design allows the superstructure and theapproach slab to move together independentof the abutment. Therefore wingwalls shouldnot be attached to the superstructure and thevertical joints between them should be parallelwith the centerline of the roadway.

The joints between superstructure andwingwalls are normally filled with 50 mm ofperformed expansion joint filler material,CMS 705.03.

The horizontal joint in the backwall createdbetween the expansion section of the semi-integral abutment and the beam seat is filledwith expanded polystyrene sheet or someequal material to act as form work for theplacement of the upper semi-integral abutmentconcrete.


3-68

Both the horizontal and vertical joints shall besealed at the back face of the backwall by useof a 900 mm wide sheet of nylon reinforcedneoprene sheeting. The sheeting should onlybe attached on one side of the joint to allow forthe anticipated movement of the integralsection.

Semi-integral abutment details are shown instandard drawing SICD-1-96M


For phased construction projects no abutmentphase shall be designed to be supported on lessthan three (3) piles or two (2) drilled shafts.

Phased construction semi-integral backwalldetails shall have a closure section detailedbetween sections of staged construction toallow for dead load rotation of the main beamsor girders.

303.2.3 ABUTMENT DRAINAGE

303.2.3.1 ABUTMENT BACKWALLDRAINAGE

The porous backfill immediately behindabutments and retaining walls should beprovided as per CMS 518. The porous backfillshall be effectively drained by the use of acorrosion resistant pipe system into whichwater can percolate. See section 303.2.3.3 forpossible exceptions.

Porous backfill shall be wrapped with filterfabric, CMS 712.09, Type A. The fabric shallcover the vertical face between the porousbackfill and the excavation, the bottom of theporous backfill and the excavation and includea 150 mm vertical up turn between the porousbackfill and the abutment backwall. Theporous backfill excavation should extend upto the horizontal plane of the subgrade or 300mm below the embankment surface. Thebottom of the porous backfill should extend tothe bottom of the abutment footing exceptwhen the vertical backface of the abutmentfooting extends more than 300 mm out fromthe vertical backface of the abutmentbackwall. Then the Porous backfill shallextend down only to the top of the abutmentfooting. Porous backfill should be 600 mmthick for its full height behind the abutmentand wingwalls except where the verticalbackface of the abutment footing extends out300 mm or less. A pipe drainage system shallbe placed at the bottom of the porous backfilland sloped to allow drainage.

While a single outlet for the pipe drainagesystems in the porous backfill can beadequate, the designer should evaluatewhether the length of the drainage run requiresmultiple outlets to supply the porous backfillwith a positive drainage system.

The pipe drainage system designs shall makeuse of standard corrugated plastic pipesegments, tees and elbows (either 90o oradjustable). Segments should be connected byoverlapping bands. Ends of runs, unlessintended to function as outlets, should haveend caps. While galvanized corrugated pipe


3-70

has been used for years, the inertness and lifeexpectancy of smooth internal wall plasticcorrugated pipe makes this the better materialto specify. CMS 518 calls for 707.33,corrugated plastic pipe, if called for in theplans.

303.2.3.2 BRIDGE SEATDRAINAGE

For full-height or spill-thru non-integral typeabutments supporting steel beams, steel girdersor prestressed I-beams, the drainage of thebearing seat shall be provided by sloping thebearing seat away from the backwall, except atthe bearings.

303.2.3.3 WEEP HOLES IN WALLTYPE ABUTMENTS ANDRETAINING WALLS

Positive drainage with a pipe system in porousbackfill is preferred.

If a location demands the use of weep holes,the weep holes through the abutment andretaining walls should be 150 mm to 300 mmabove normal water or ground line. The porousbackfill with filter fabric behind the wallsshould be shown as extending at least 150 mmbelow the bottom of the weep holes.

Weep hole type drainage systems should not beused with concrete slope protection as the flowundermines the concrete protection, ultimatelycausing its failure.

Where sidewalks are located immediatelyadjacent to wall type abutments or retainingwalls, some type of porous backfill collectionand drainage system, with pipes if necessary,should be used in lieu of weep holes.

303.2.4 WINGWALLS

Wingwalls shall be of sufficient length toprevent the roadway embankment fromencroaching on the stream channel or clearopening. Generally the slope of the fill shallbe assumed as not less than 1 vertical to 2horizontal, and wingwall lengths computed onthis basis.

Wingwalls shall be designed as retainingwalls.

Cantilevered wingwalls shall not be used withintegral abutments as the walls will createadditional pressures due to superstructuremovement.

303.2.5 EXPANSION ANDCONTRACTION JOINTS

Expansion joints should generally be providedevery 30 000 mm with the followingexceptions:

• When the total length of wingwalls andbreastwall exceeds 30 000 mm in length,vertical expansion joints should beprovided just beyond each side of thesuperstructure.


3-71

• When the length of a breastwall exceeds30 000 mm in length, no expansion jointshall be placed under the superstructure.An expansion joint shall be positioned asdescribed in the above paragraph.

An expansion joint shall be filled withpreformed expansion joint material, CMS705.03, or other suitable compressible material.

Expansion joints shall be waterproofed asdescribed in Section 303.2.2.1.b of thisManual.

Contraction joints are not required forabutments.

Reinforcing steel shall not project throughexpansion or contraction joints.

303.2.6 REINFORCING STEEL

303.2.6.1 REINFORCEMENT, "U"AND CANTILEVER WINGS

The minimum amount of reinforcing in thewings, their junctions with the backwall andtheir supports shall be No. 16M bars on 450mm centers, both horizontally and vertically, inboth faces.

If a secondary member, such as a shortcantilevered turnback wing, is attached to anabutment or other member, reinforcing steelshall be provided in the secondary member atits connection to the main member and in allparts of the main member stressed by thesecondary member, even though small, with

adequate lap or bond length at the junctionbetween the several kinds of bars. Theprobable presence of some tensile stress atvarious locations, due to the secondarymember, must be recognized.

303.2.7 FILLS AT ABUTMENTS

The requirements for fills at abutments, timeof settlement, and what and when to usespecial notes to control field construction offills are dealt with in earlier preliminarysections of this Manual. The designer shouldnot attempt to add these requirements to aspecific structure without confirmation fromthe Office of Structural Engineering'sfoundation section.

303.3 PIERS

303.3.1 GENERAL

A "free-standing" pier is defined as one whichdoes not depend upon its attachment to thesuperstructure for its ability to resisthorizontal loads or forces.

The width of footing for a free-standing piergenerally shall be not less than one-fourth theheight of the pier where founded on soil andnot less than one-fifth the height of the pierwhere founded on bedrock.

The minimum width of footing supported bya drilled shaft is the diameter of the shaft.

Where piling is used to support free-standingpiers, the distance between centers of outsidepiles, measured across the footing, generallyshall be not less than one-fifth the height ofthe pier.


3-72

Widths greater than the above shall beprovided if required for proper bearing area orto accommodate the required number of piles.

Height of pier is the distance from bottom offooting to bridge seat.

For multiple span bridges with continuity overpiers, where the height of pier is more than 50percent of the length of superstructure from thepoint of zero movement to such pier, it may beassumed that the pier will bend or tiltsufficiently to permit the superstructure toexpand or contract without appreciable pierstress. This assumption is not permissible ifthe piers are skewed more than 30 degrees.The above rule does not apply to rigid frame orarch bridges.

Slender columns of either concrete or steel maybe designed to bend sufficiently to permit thesuperimposed superstructure to expand andcontract, but the resulting bending stressesshall not exceed the allowable.

For phased construction projects no pier phaseshall be designed to be supported on less thanthree (3) piles, if a cap pile pier or two (2)columns if a cap and column type.

For a new or replacement structure, individualfree standing columns without a cap are notpermitted.

303.3.1.1 BEARING SEAT WIDTHS

Pier bearing seat widths for reinforcedconcrete slab bridges should conform withStandard Drawing CPP-2-94M. Also seeSection 303.3.2.4 of this Manual.

Pier caps on piles, drilled shafts or on columnsare normally a minimum of 915 mm wide.This is the standard width used for continuousspan prestressed box beams and I-beams.Bearing seat widths of 915 mm, whilenormally adequate must be verified by thedesigner of the structure. Large bearings,skew angle, intermediate expansion devices,AASHTO earthquake seat requirements, etc.may require additional width.

303.3.1.2 PIER PROTECTION INWATERWAYS

See Section 200 of this Manual for pilingprojection requirements and Section 600 &700 for plan notes to be added to designdrawings.

303.3.2 TYPES OF PIERS

303.3.2.1 CAP AND COLUMNPIERS, CAP & COLUMNREINFORCEMENT

The cantilever arms of cap and column piersshall be designed for the same impact fractionas the superstructure. (See section 303.3.2.7)


3-73

Longitudinal reinforcing shall conform toAASHTO. Round Columns shall be reinforcedwith spiral reinforcing placed directly outsidethe longitudinal bars.

Round columns are preferred and normallyshould be 915 mm diameter Cap dimensionsshould be selected to meet strengthrequirements and to provide necessary bridgeseat widths. Ends of caps shall be squared andcantilevered. beyond the face of the endcolumn to provide approximately balancedmoments in the cap. Cantilevered pier capsmay have the bottom surface of the cantileversloped upward from the column toward the endof the cap.

Minimum column diameters of 915 mm aregenerally used with spiral reinforcing. Spiralsare made up of 16M diameter bars at 115 mmc/c pitch with a 765 mm outside core diameter.Using the circumference of the spiral as the outto out of the reinforcing steel bar, this columnsize normally has a relatively small ratio of theactual axial load to the column’s axial loadcapacity. (i.e., less than 2/3). Therefore whilethis spiral reinforcement does not conform withAASHTO requirement (8.18.2.2.3) it isacceptable under AASHTO 8.18.2.1 if the ratioof actual loads to design capacity is under 2/3.

For columns where the ratio of actual axialload to axial capacity is greater than 2/3, thespiral reinforcing should conform to AASHTOSection 8.18.2.

At least 3 spacers, devices to position theactual spiral to the required pitch, should beused for 765 mm diameter spirals. Spacersshall be equally spaced along the periphery ofthe spiral.

In no case shall column reinforcement notmeet minimum cross section area, shrinkageand temperature requirements of AASHTO.

303.3.2.2 CAP AND COLUMNPIERS ON PILES

Piers supported on piles generally should haveseparate footings under each column.

Column piers shall have at least 4 piles perfooting.

For grade separation structures, the top of thepier’s footings should be a minimum of 300mm below the level of the bottom of theadjacent ditch. This applies even though thepier is located in a raised earth median barrier.

303.3.2.3 CAP AND COLUMNPIERS ON DRILLEDSHAFTS

Where columns are supported on a drilledshaft foundation, the drilled shaft should be atleast 150 mm larger in diameter than thecolumn. This is to allow for field locationtolerances of the drilled shaft. A drilled shaftfoundation is defined as starting 0.3 meterbelow ground level or 0.3 meter above normalwater.

SECTION 300 DETAIL DESIGN-METRIC SEPTEMBER 1998

3-74

303.3.2.4 CAP AND COLUMN PIERSON SPREAD FOOTINGS

Cap and column piers on spread footings,placed on existing soils or on embankmentfills, should have continuous footings whichshould extend beyond the center of the endcolumn a distance equal to approximately 1/3of the distance between the end column andthe adjacent column, in order to provideapproximately balanced moments.

Cap and Column piers with spread footings onbedrock shall have separate footings undereach column.

For grade separation structures, the top of pierfootings should be a minimum of 450 mmbelow the level of the bottom of the adjacentditch. This applies even though the pier islocated in a raised earth median barrier. In nocase should the bottom of the footings inexisting soil or on embankment fills be abovethe frostline.

The width of footing for a free-standing piergenerally shall be not less than one-fourth theheight of the pier where founded on soil andnot less than one-fifth the height of the pierwhere founded on bedrock.

303.3.2.5 CAPPED PILE PIERS

Steel H piles shall be a minimum HP310 x 79.The piles should be shown on the plans withthe flanges of the H-section perpendicular tothe face of the pier cap.

The distance from the edge of a concrete piercap to the side of a pile shall be not less than200 mm.

The diameter of the exposed portions of cast-in-place reinforced concrete piles generallyshould be 400 mm, but if exposed length,design load or other conditions make itnecessary, larger diameter cast-in-place pilesshould be used. Cast-in-place piles shall bereinforced with a reinforcement cagecomposed of 8-#19M reinforcing bars with a300 mm outside diameter, #13M spiral, witha 300 mm pitch The cage length shouldextend from the finished top of the pile to 5meters below ground level. The reinforcingsteel shall be shown in the structure’sreinforcing bar list and be included in item507 for payment. This will require an as perplan note. The use of cast-in-place pilesgreater than 400 mm in diameter will requirean increase in the width of the cap of StandardDrawing CPP-2-94M. See Section 303.3.3.

Exposed H piles and unreinforced concretepiles shall have pile protection. Seedescription in Standard Drawing CPP-2-94Mor a plan note is available. Also See Section200 for a description of pile protection.

For pile embedment requirements intoconcrete, see Section 303.3.3.

An optional construction joint shall be shownat the top of pier caps for reinforced concreteslab bridges. This joint is optional as somemachine finishing equipment for slab bridgedecks require a uniform depth of freshlyplaced concrete in order to obtain best results.


3-75

The design of the cap for a capped pile piersupported on bearing piles should be based onthe assumption that any one pile in any threeconsecutive piles does not have sufficientbearing to support axial loads. The cap designdoesn’t need to assume the end piles cannotsupport axial loads.

Although actual performance of this type ofpier indicates this condition to be rare, thisconservatism is recommended.

For phased construction projects no pier orabutment phase shall be designed to besupported on less than three (3) piles.

303.3.2.6 STEEL CAP PIERS

If at all possible this alternative should not beselected. This is a fracture critical design (seesections in steel superstructure) which hashistorically shown both steel member andweld metal cracking problems.

If a steel box girder is required as a pier cap,the design shall allow reasonable access to theinterior for maintenance, inspection and repairpurposes. The box shall not be physicallysmaller that would limit access to the interiorof the box. Access hatches of the box girdershould be bolted and sealed with a neoprenegasket. Access hatches should also be lightenough for a inspector to easily remove them.One recommended lightweight material isABS plastic.

Designers shall assure that all governmentalagency regulations as to enclosed spaces,ventilation, lighting, etc. are complied withwithin any enclosed steel pier cap design.

Box designs with cut away webs to allow forstringers to continue through the box aregenerally not considered acceptable alterna-tives.

Situations which require stringers to becontinuous through, and in the same planewith a steel pier cap or crossbeam should beavoided if at all possible. If there is no otheralternative solution, the preliminary details ofthe connection should be reviewed by theOffice of Stuctural Engineering beforecompleting the plans.

Designers should review all weld details forpossible fatigue problems. Contact the Officeof Structural Engineering for assistance in thisarea.

303.3.2.7 T-TYPE PIERS

The cantilever arms of T-type piers are to bedesigned for the same impact fractionAASHTO requires for the superstructure.

In the cap of a T-type pier, the top layer ofreinforcing bars shall extend the full length ofthe cap and be turned down at the end face thenecessary development length. The secondlayer of reinforcing steel shall extend into thestem of the pier at least the necessarydevelopment length plus the depth of thecantilever at its connection to the stem.


3-76

T type or wall type piers of large cross-sectional area and low unit stresses which arereinforced with a small percentage oflongitudinal bars shall be provided with anominal amount of lateral ties or hoops. In nocase shall the concrete column contain lessreinforcing than necessary to satisfyshrinkage, temperature and columnreinforcement requirements of AASHTO.

303.3.2.8 PIER USE ON RAILWAYSTRUCTURES

For clearance requirements see Section 200 ofthis Manual. Items listed in Section 200 areonly general rules and vary from railroad torailroad. The designer shall confirm with theindividual railroad the actual physicaldimension and design requirements.

303.3.2.9 PIERS ON NAVIGABLEWATERWAYS

Piers in the navigation channel of waterways,unless protected from collision by an adequatefendering system, shall be designed to resistcollision forces based on AASHTO GuideSpecification for Vessel Collision Design ofHighway Bridges.

303.3.2.10 PIER CAPREINFORCING STEELSTIRRUPS

Stirrups for concrete beams of constant depth,such as pier caps, should be detailed usingeither 2 "U" bars with the vertical legs longenough to furnish the required lap length or asingle bar closed type stirrup with 135E bends

at both ends of the rebar. The single barclosed type stirrup should only be selectedwhen minimum required lap lengths cannot beprovided with the "U" type stirrup. Thecorner with the 135E bends of the closed typestirrup should be placed in the compressionzone of the concrete beam.

303.3.3 FOOTING ON PILES

Piles supporting capped pile piers shall beembedded 450 mm into the concrete cap.Other substructure units on a single row ofpiles should have the piles embedded 600 mminto the concrete. A 300 mm embedmentdepth into the concrete footing is required forall other cases. In every case, there shall be atleast 450 mm cover over top of pile.

The distance from the edge of a footing to thecenter of a pile shall be not less than 450 mm.The distance from the edge of a concrete piercap to the side of a pile shall be not less than200 mm.

303.4 FOUNDATIONS

303.4.1 MINIMUM DEPTH OFFOOTINGS

Footings, not exposed to the action of streamcurrents, should be founded based on thefollowing minimum depths:

For grade separation structures the top offooting shall be a minimum of 300 mmbelow the finished ground line. The top offooting should be at least 300 mm below thebottom of any adjacent drainage ditch.


3-77

The bottom of footing shall not be less than1200 mm below, measured normal to, thefinished groundline.

Due to the probability of stream meander,pier footings of waterway crossings in theoverflow section should not be abovechannel bottom unless the channel slopesare well protected against scour. Foundingpier footings at or above the flow lineelevation is discouraged.

Where footings are founded on bedrock (notethat undisturbed shale is rock) the minimumdepth of the bottom of the footing below thestream bed, D, in meters, shall be as computedby the following:

D = T + 0.50Y

T = Thickness of footing (in meters)

Y = distance from bottom of stream bed tosurface of bedrock (in meters)

The footing depth from the above formulashall place the footing not less than 75 mminto the bedrock.

Adjustment may be made to the minimumdepth of the bottom of a footing due to actualfrostline at the structure site.

303.4.1.1 FOOTING, RESISTANCETO HORIZONTALFORCES

The safety factor against horizontal movementat the base of a structure; i.e., the ratio ofavailable resistance to movement to the forces

tending to cause movement, shall be not lessthan 1.5 except as specified below for footingson bearing piles.

The friction resistance between a concretefooting and a cohesionless soil may be takenas the vertical pressure on the base times thecoefficient of friction "f" of concrete on soil.

For coarse-grained soil without silt, "f" maybe taken as 0.55.

For coarse-grained soil with silt, "f" may betaken as 0.45.

For silt, "f" may be taken as 0.35.

If the footing bears upon clay, the resistanceagainst sliding shall be based upon thecohesion of the clay, which may be taken asone-half the unconfined compressive strengthprovided, however, that the frictionalresistance against sliding shall not beconsidered to be greater than that obtainedusing the coefficient "f" of 0.35. If the clay isvery stiff or hard, the surface of the clay shallbe roughened before the concrete is placed.

If the footing bears upon bedrock,consideration shall be given to features of thebedrock structure which may constitute planesof weakness such as laminations orinterbedding. If there is no evidence of suchweakness, the coefficient of friction "f" maybe taken as 0.55 for shale and 0.7 for rock.

If the frictional or shearing resistance of thesupporting material is inadequate to withstandthe horizontal force, additional resistance shallbe provided by one or more of the followingmeans:


3-78

(a) Increase the footing width and/or usefooting keys.

(b) Make allowance for the passive pressuredeveloped at the face of the footing.

(c) Use battered piles, footing struts,sheeting or anchors.

For footings with keys, allowance shall bemade for the shearing resistance furnished bythe supporting material at the elevation of thebottom of the key. Keys generally shall belocated within the middle-half of the footingwidth.

For footings on piles, no allowance shall bemade for the frictional resistance of thefooting concrete on soil. For such footings,the horizontal component of the axial load onbattered piles shall be taken at full value,without the application of the safety factor of1.5. The safety factor shall apply for anyrequired additional resistance provided by thepassive pressure developed in the soil in frontof such foundations. The above may beexpressed by the following formula:

A - C $ 1.5 where,B - C

A = available resistance to movement

B = force tending to cause movement

C = horizontal component of the axialload in battered piles

For structures on piles or soils, the passiveresistance developed on the face of afoundation (assuming a level ground surface)may be based on an equivalent passive fluidweight Wp (kN/m3) for the undisturbedmaterial encountered or anticipated. Theequivalent passive fluid weight may be basedon the following equation:

Wp = W tan2 (45 + Ø/2) kN/m3

where

W = unit soil weight, kN/m3

Ø = angle of internal friction, in degrees.

For soft clays to coarse compact sand andgravels, Wp may vary from 15.7 to 125.7kN/m3, respectively. For firm soils Wp may betaken as equal to 47.1 kN/m3. The totalpassive resistance (Pp) may therefore be basedon the following equation:

Pp = 0.5 Wp (H12 - h12), kN/m

where,

"H1" and "h1" are the effective depth and thesurcharge depth respectively, both in meters.For structures without piles the effective depth"H1" may be measured from the groundsurface to the bottom of the footing or footingkey. For structures on piles the effectivedepth may be extended below the bottom ofthe footing a depth equal to one-fourth thepenetrated length of the piles, but not toexceed 1.5 meters. The surcharge depth "h1"is the depth below ground surface affected by


3-79

seasonal changes or the depth of uncompactedbackfill, whichever is larger. In estimating theabove depths allowance shall be made for thepossibility of future loss of surface material byerosion, scour or possible excavation. For afoundation on piling the effective width forcomputing passive resistance (on the piling)may be equal to the sum of the pile diameters,but not to exceed the length of the footing.

If the preceding methods do not furnishsufficient horizontal resistance, the use ofsheet piling to increase the effective depth(H1) of the passive resistance below theelevation of the bottom of the footing may beincorporated in the design. Such sheet pilingshall be rigidly attached to the footing andcantilevered downward. This sheet piling shallhave sufficient section to resist the cantilevermoment produced by the passive resistancedeveloped in adjacent soil and shall have aconnection to the footing adequate to providethe required fixed condition. See Section303.2.2.1.

Alternate methods of analysis may beacceptable.

303.4.1.2 LOCATION OFRESULTANT FORCESON FOOTINGS

Footings shall be designed to distribute thecombined total vertical and horizontal forcesin such a manner that the required structuralstability is obtained and that the allowable unitbearing values of the subfoundation materialsare not exceeded.

For footings on soils, the resultant of all forcesgenerally should intersect the base of thefooting within its middle third.

For footings on bedrock, the resultant of allforces generally should intersect the base ofthe footing within its middle half or thefooting should be embedded in bedrock to adepth sufficient to prevent footing rotation.

Where the structural stability of the memberis obtained by its attachment to some otherstable portion of the structure, the limitationsof the preceding two paragraphs may notapply.

303.4.1.3 REINFORCING STEELIN FOOTINGS

Secondary reinforcing steel in a footinggenerally should be placed under the mainsteel.

For footings on piles the reinforcing bars shallbe placed near the bottom of the footing ratherthan at the top of the piles.

If the footing dowels (footing to wall orcolumn) are provided, a bent portion of thedowel should lie in the plane of the bottomfooting bars.

For piers in embankment slopes the minimumdowel size and spacing should be No. 25M @300 mm centers. For full length wall typepiers not in embankment slopes and withoutearth overturning forces the minimum dowelsize and spacing should be No. 19M @ 300mm centers.


3-80

At locations where the concrete unit tensilestress approaches the allowable for un-reinforced concrete, reinforcing steel shouldbe provided. This applies particularly to thebottom of the toe and the top of the heel of afooting for a cantilever-type retaining wall orabutment where the footing is thin inproportion to the toe and heel projections. Itmay also apply to the tops of footings for tallpiers where unanticipated longitudinal orlateral movements may induce tension in thetops of the footings.

303.4.2 PILE FOUNDATIONS

303.4.2.1 PILES, PLAN SHEETREQUIREMENTS

For record and project use, each pile for astructure shall be individually identified by aunique number. The designer may choose tonumber each pile on the individualsubstructure plan sheet or on a separate pilelayout sheet.

303.4.2.2 PILES, NUMBER &SPACING

The designer shall comply with the followingmaximum center to center spacing of piles:

• In capped pile piers, 2300 mm.

• In capped pile abutments, 2500 mm.

• In stub abutments, front row, 2500 mm.

• In wall type abutments and retaining walls, front row, 2300 mm.

• Cap and column piers should have at least 4 piles per individual footing.

303.4.2.3 PILES BATTERED

The path of battered piles should be checkedto see that the piles remain within the right-of-way and do not interfere with piles fromadjacent and existing substructure units norconflict with portions of staged construction.

In general, a batter of 1:4 is considereddesirable, but in cases where sufficientresistance is not otherwise attainable, a batterof 1:3 may be specified.

Piles should be battered to resist the streamforces. Battered piles also should be providedwhere necessary to avoid settlement due togroup action by increasing the periphery of thesoil mass.

Abutment piles should be battered normal tothe centerline of bearings.

303.4.2.4 PILES, DESIGN LOADS

The pile’s Ultimate Bearing Value, based oncalculation of dead and live load transferred tothe piles shall be given in the structureGeneral Notes.


3-81

Ultimate Bearing Value load is equal to theactual unfactored design load multiplied by asafety factor of two (2).

The largest of these calculated individual pileUltimate Bearing Value loads for eachsubstructure unit shall be used as the UltimateBearing Value for that substructure unit. Thisvalue for each substructure shall be listed inthe structure General Notes.

The table below for H-piles should be used forselecting the required pile size based on thecalculated Ultimate Bearing Value load foreach substructure unit.

HPile Size

MaximumDesignLoad

UltimatebearingValue

HP250X62 500 kN 1000 kN

HP310X79 650 kN 1300 kN

HP360X108 850 kN 1700 kN

Design load values for H piles are based on amaximum service load stress of 62 MPa.

The following table for pipe piles should beused for selecting the required pile size basedon the calculated Ultimate Bearing Value loadfor each substructure unit.

Pipe PileDiameter

MaximumDesignLoad

UltimatebearingValue

300 mm 450 kN 900 kN

350 mm 650 kN 1300 kN

400 mm 800 kN 1600 kN

The actual value listed in the structure generalnotes should not be the Ultimate BearingValue of the pile size selected, whether H pileor Pipe pile, but the calculated UltimateBearing Value load of the substructure unit orunits.

Maximum specified pile spacings andmaximum allowable Ultimate Bearing loadsshould be utilized to minimize the number ofpiles.

303.4.2.5 PILES, STATIC LOADTEST

A static load test item should be included inthe structure’s estimated quantities if the actualcalculated Ultimate Bearing load for the pilesis 800 kN or more, except as follows:

• A static load test is not necessary if pilesare driven to refusal on bedrock.

• A static load test is not necessary if theestimated linear meters of piles are lessthan 3000 meters.

Structures that require a static load test itemmay also require subsequent static load testsas defined in the following table:


3-82

Estimated Linealmeters of Pile Type

Number of SubsequentStatic Pile Test Loads

3000-6000 1

6000-9000 2

9000-12 000 3

etc. etc.

When more than one type or size of pile isspecified for a structure, the above criteriashall be applied independently for each piletype or size. If a project includes more thanone structure, consideration should be given toreducing the number of static load test items,as generally many of the static load test itemsare non-performed.

303.4.2.6 PILES, DYNAMIC LOADTEST

A dynamic load test item should be includedin the structure’s estimated quantities if theactual calculated Ultimate Bearing load on thepile is 800 kN or more, except as follows:

• A dynamic load test is not required if pilesare driven to refusal on bedrock.

• A dynamic load test is not necessary if theestimated linear meters of piles is less than500 meters.

Structures that require a dynamic load testshall have an estimated pay quantity as listedin the following table.

Estimated linear Metersof Piles

Estimated Pay Quantityin Hours

500-1500 3

1500-3000 6

3000-6000 9

6000-9000 12

9000-12 000 15

etc. etc.

If more than one type or size of pile isspecified for a structure, the above criteriashall be applied independently for each piletype and size.

303.4.3 DRILLED SHAFTS

1065 mm diameter drilled shafts for piers and915 mm diameter for abutments are normallyused.

The diameter of bedrock sockets of a drilledshaft are generally 150 mm less in diameterthan the diameter of the drilled shaft above thebedrock elevation. The 150 mm downsize canbe eliminated for abutment shafts.Reinforcing steel cages should be based on thebedrock socket diameter.

The drilled shaft diameter for the abutmentshafts can be shown as one constant diameterfor the full length of the drilled shaft (throughbedrock and through soil).


3-83

Spiral reinforcement used in the drilled shaftis normally #13M diameter bar at 115 mmpitch with spiral diameter of 150 mm less, outto out of spiral cage than the drilled shaftdiameter. (Note AASHTO specifications donot recognize 115 mm pitch as meeting spiralrequirements definition 8.18.2.2.3) Whensteel casing is left in place, a pitch of 300 mmshould be used for the spiral reinforcing.

Drilled shafts with a diameter of less than 915mm are not recommended.

The diameter of the drilled shafts should be150 mm larger than the pier column diameterso that if the drilled shaft is slightlymislocated, the pier column can still be placedat plan location, although the pier columnwould not be exactly centered on a mislocateddrilled shaft.

For record and project use, each drilled shaftfor a structure shall be individually identifiedby a unique number. The designer maychoose to number the drilled shafts on theindividual substructure plan sheet or on aseparate drilled shaft foundation layout sheet.

A construction joint between the drilled shaftand any column will be required. Thereforethe designer will need to specify reinforcingsteel, incorporating the required lap splices, atthe construction joint.

The designer should develop a lap splice thatwill allow both for required lap and minimumcover due to mis alignment of the drilled shaftversus the column. Possible alternatives aretwo cages, one for the drilled shaft diameterand a second splice cage for the lap to thecolumn.

When the exposed length of the pier columnsis relatively short, one full length reinforcingsteel cage, from the bottom of the drilled shaftup into the pier cap, should be designed. Thesteel cage should be designed to provide a 75mm concrete cover within the pier column.

When the drilled shaft is socketed into thebedrock, the quantity of the reinforcing steelin the drilled shaft should be included with theitem special "Drilled Shaft" for payment. Fordrilled shafts with friction type design wherethe tip elevation is known, the reinforcingsteel should be paid under item 524, DrilledShafts.

A general note as listed in section 600 will berequired.

The top of the drilled shaft is defined as 0.3meter above normal water elevation, for piersin water, and 0.3 meter below the groundsurface for piers not in water.


3-84

304 RAILING

304.1 GENERAL

All structures funded by FHWA are requiredto have railing systems which have beenapproved through actual crash testing of therailing design. Crash testing shall conform thethe requirements of NCHRP document 350.

Projects on the National Highway System soldafter October 1, 1998 are required to havecrash tested permanant railing systemsmeeting or exceeding NCHRP 350 TestingLevel 3(TL3).

Provision should be made in metal railings forexpansion and contraction. If standard railingconnections will not allow for neededexpansion and contraction movement, slidingdevices need to be used.

304.2 TYPES OF RAILING

• Bridge Railing Deflector Parapet Type,New Jersey Shape - Standard DrawingBR-1M

NCHRP TL4 (915 mm)

NCHRP TL5 (1065 mm)

• Deep Beam Guardrail with TubularBack-up - Standard Drawing DBR-2-73M (NCHRP TL 2)

• Bridge Retro-Fit Railing, Thrie BeamBridge Railing for bridges with SafetyCurbs - Standard Drawing TBR-91M

• Transition section for Bridge DeflectorParapet Type

• Bridge Sidewalk Railing with ConcreteParapets - Standard Drawing BR-2-82M(not crash tested. No TL level)

• Portable Concrete Bridge Barrier,Standard Drawing PCB-91M

• Twin Steel Tube Bridge Guardrail -Standard Drawing TST-1-98M (NCHRPTL4)

• Bridge Sidewalk Railing with ConcreteParapets - Standard Drawing BR-2-98M(NCHRP TL4)

304.3 WHEN TO USE

304.3.1 BRIDGE RAILINGDEFLECTOR PARAPETTYPE

Bridge railing deflector parapet, New Jerseyshape, shall be used on all highway & railroadoverpass structures with no sidewalks.

Two (2) heights of bridge railing deflectorparapet, New Jersey shape, are currentlyavailable in Standard Drawing form.


3-85

915 mm high deflector parapet. A 915 mmheight is the new minimum height deflectorparapet for two lane structures with an ADTTin one direction of less than 2500. The heightincrease over the old 813 mm high parapet isto allow for future overlays. StandardDrawing BR-1M gives details for the deflectorparapet reinforcing, end transition section andtransition to 813 high parapet.

1065 mm high deflector parapet. A 1065 mmheight is the recommended deflector parapetheight for Interstate, 4 lane divided orstructures with an ADTT, in one direction of2500. Standard Drawing BR-1M gives detailsfor the deflector parapet reinforcing, endtransition section and transition to 813 highparapet.

Bridge structures with sidewalks should haveone of the following:

• If bridge fencing is required a 813 mmhigh, vertically straight, 300 mm thickconcrete parapet is recommended. If thisfence and parapet configuration is used analuminum railing as per Standard DrawingBR-2-98M is not required. See Figure326 - Page 3-90.

• If no bridge fencing is required bridgesidewalk railing with concrete parapets,Standard Drawing BR-2-982M, shall beused.

1270 mm high bridge railing deflector parapetshall be used in median areas where protectionagainst oncoming headlight glare is requiredor to match roadway parapets. Medianparapets should match the height of roadwayparapets.

Bridge decks, which have concrete deflectorparapets installed, shall be checked to confirmstructural adequacy support additional railingand vehicle impact loads.

Concrete parapets, whether New Jersey shapeor sidewalk vertical wall type, should bedesigned and detailed as follows:

All horizontal reinforcing steel shall bedetailed as continuous for the total length ofthe structure.

Crack control joints shall be sawed into theconcrete parapets. Distance between sawedjoints on the structure shall be between 1800and 3050 mm.

The sawcut crack control joint should bedetailed as 25 mm deep, and the joint filledwith a caulking material, federalspecification TT-S-00227E. Thisrequirement is already established on manyof the standard drawings. For special casesa plan note will be required. See section600.

Detail plans for structures with concreteparapets should include detailed locations ofthe crack control joints and verticalreinforcing bars.


3-86

304.3.2 DEEP BEAM RAIL WITHTUBULAR BACK-UP

This railing configuration is not recommendedfor use as the crash testing does not meetNCHRP TL3.

304.3.3 TWIN STEEL TUBEBRIDGE GUARDRAIL

Rural bridges crossing a stream shall use thetwin steel tube bridge guardrail system inaccordance with Standard Drawing TST-1-98M

If a bridge crossing a stream has its decksurface elevation greater than 7.5 metersabove normal water elevation a 915 mm highbridge railing deflector parapet or sidewalkand parapet should be used in lieu of TST-1-98M.

The required bridge terminal assembly sectionbetween standard roadway single W beamguardrail and TST-1-98M is part of TST-1-98M.

304.3.3.1 SPACING

TST-1-98M twin steel tube post spacing shallbe 1905 mm. If this requires an inlet mountedpost on a wingwall the designer should designand specify the inlet mounted post. Inletmounted posts shall be designed in accordancewith AASHTO.

The designer should carefully review positionof posts that are near an obtuse corner of askewed structure for possible interference ofnot just the anchor bolts but the back of theactual installed post with the wingwall.

The designer should confirm the stations tothe centerline of the first posts off the bridge,shown on the site plan, are correct.

304.3.4 BRIDGE RETRO-FITRAILING, THRIE BEAMBRIDGE RAILING FORBRIDGES WITH SAFETYCURBS

Thrie-beam railing as described on StandardDrawing TBR-91M should only be used as aprovisional upgrade on structures with safetycurb and parapets where a safety upgrade isrequired but the structure will have a majorrehabilitation or will be replaced in the nearfuture.

This alternative is not generally recommendedby the Office of Structural Engineering. Amore suitable alternative is concrete refacingof existing safety curb and parapets to a NewJersey barrier shape. See Section 400 of thisManual for additional information on refacingof safety curb and parapets.


3-87

304.3.5 TRANSITION FORBRIDGES DEFLECTORPARAPETS

If deep beam guardrail from the roadway is toconnect with bridge deflector parapets atransition section is required. The Departmenthas standard drawings showing the transitionsection between the roadway deep beamguardrail and 813 mm high bridge railingdeflector parapets.

The deflector parapet transition details shouldbe used on both new structures andrehabilitated structures having concrete para-pets added. Deflector parapet details can beused on either a structure’s turnbackwingwalls, widened approach slabs or directlyon the actual structure.

304.3.6 PORTABLE CONCRETEBRIDGE BARRIERSTANDARD DRAWINGPCB-91M

All phased construction or rehabilitationwhich create a temporary no railing conditiongenerally shall require Portable ConcreteBridge Barrier, PCB-91M, to be installed inaccordance with the requirements of DesignData sheet PCB-DDM.

The designer shall detail the installationrequirements, including the number of anchorbolts per barrier, in the bridge plans.

Pay item for barrier shall be item 622 -Portable Concrete Barrier, 813 mm, BridgeMounted, As Per Plan - meters.

An alternate is the use of temporary twin steeltube bridge guardrail railing with posts anchorsystems designed into the structure if theadditional lane width gained is justified.

Although temporary railing shall be specifiedand completely described in the bridge plans,temporary railing is a roadway item andshould be included in the roadway quantities.

304.3.7 BRIDGE SIDEWALKRAILING WITHCONCRETE PARAPETS -BR-2-82M

This railing configuration is not recommendedfor use as the railing, STD DRG BR-2-82M,has not been crash tested.

304.3.8 BRIDGE SIDEWALKRAILING WITHCONCRETE PARAPETS -BR-2-98M

Recommended for use on bridge structureswith sidewalks of 200 mm height.


3-88

305 FENCING

305.1 GENERAL

The primary purposes of protective fencingare (1) to provide for the security ofpedestrians and (2) to discourage the throwingor dropping of objects from bridges ontolower roadways, railroads, boat lanes oroccupied property.

Fence may be needed on high level bridgeswhere wind may threaten to blow pedestriansor even occasional stranded motorists off thebridge.

Also, on bridges where there is a danger thatthe outside parapet may be mistaken for amedian barrier, persons may jump over theparapet in emergency situations in periods ofdarkness. These situations should be treatedon a case-by-case basis.

Since a falling object problem could occur atany bridge accessible to pedestrians, it isnecessary to consider installation of protectivefencing at such locations.

Generally, fencing attached to bridgestructures for the protection of traffic andpedestrians should conform to Standard Draw-ing VPF-1-90M. The designer may need toenhance this standard to deal withrequirements for the specific structure

305.2 WHEN TO USE

Pedestrian Fencing may be required when atotal of 10 points or greater is achieved for astructure due to the following criteria.

The designer should use the following pointprocedure as a general guide as to the need forfencing.

The affected district should also be consultedfor their input.

The list is not to be construed as all inclusive.Other rationale may be used on a case-by-casebasis. Similarly, retrofitting of bridges whichqualify according to the total index number isnot mandatory if adequate justification for notdoing so can be furnished.

305.3 FENCING CONFIGURATIONS

For structures with sidewalks, the top of fenceshould be a minimum height of 2450 mmabove the sidewalk. For a greater degree ofprotection against objects being thrown fromthe bridge, the fence may be curved tooverhang the sidewalk. For curved fence theposts should be vertical for approximately 2450mm above the sidewalk before curving inwardover the sidewalk. The overhang should be atleast 300 mm less than the width of thesidewalk, with a maximum overhang of 1100mm. The slope of the straight overhangingportion should be 1 vertical to 4 horizontal.The radius of the connecting arc should be 815mm.


For narrow pedestrian bridges, bent pipeframes are generally used with pipe bend radiiof 600 mm at the upper corners and the start ofthe radii about 2450 mm above the sidewalksurface. The fabric should start at the deckline, top of curb or parapet and may stop at theupper end of the bent portion of the frame.


3-89

INDEX POINTS JUSTIFICATION ITEM

2 a. Overpass within an urbanized area of 50,000 or more population

2 b. Overpass with sidewalks but not in an urbanized area as defined in(a.)("Sidewalk" does not include safety curbs 685 mm or less in width.)

2 c. Overpass which is unlighted.

2 d. Overpass not a main thoroughfare, i.e., on collectors or local streets.

2 e. Overpass within 0.8 km of another overpass exclusive of pedestrianbridges, having or requiring protection.

4 f. Overpass within 0.8 km of another overpass having previous reports offalling objects.

4 g. Overpass within 1.6 km of a school, playground or other pedestrianattraction.

4 h. Bridges over any feature which has a high count of boat, rail, vehicular or pedestrian traffic, or includes damage-sensitive property.

6 i. Overpass which has had prior reported incident of falling objects.

10 j. Overpass which is used exclusively by pedestrians.

"OVERPASS" is a bridge over a highway or a railroad.

Fabric on the top horizontal area of the frameis sometimes not installed becauseadventurous youngsters tend to walk on thetop of the enclosure. See Figure 327 - Page 3-91 for an illustration of this configuration. Totry to eliminate the adventurous youngsterproblem, some pedestrian bridges have used aframe design which comes to a peak at thecenter of the structure, similar to a house roofline.

Chain link fabric should not have an openingat the bottom through which large objectscould be pushed. A detail to close the bottomof a fencing section is included on standard

drawing VPF-1-90M. The closure plate detailis required for all fence configurations whichhave tension wire at the bottom of the fencefabric.

Posts and frames may be either plumb orperpendicular to the longitudinal grade of thebridge, subject to considerations of estheticsor practicality of construction. Completedetails of base plates, pipe inserts or othertypes of base anchorage shall be provided onthe plans. If applicable to the specific project,details from Standard Drawing VPF-1-90Mmay be referred to in the project plans.


3-92

305.4 SPECIAL DESIGNS

The following information is given thedesigner as a basis for specialized designs. Itis not intended for designers to develop theirown requirements in lieu of the StandardDrawing VPF-1-90M.

For fence installation projects on newstructures, the installation of a traffic railing(aluminum railing) is not required if the topconcrete parapet or concrete wall is 813 mmabove roadway for structures withoutsidewalks or 813 mm above the top of side-walk for structures with sidewalks. See Figure 326 - Page 3-90

For special fence designs, plan notes shall berequired to define materials, trafficmaintenance, construction procedures andother requirements. The designer shouldfollow the example of Standard DrawingVPF-1-90M for development of requirednotes.

305.5 FENCE DESIGNGENERALREQUIREMENTS

Fencing mesh should consist of supportedwire mesh of the chain- link variety with 25mm diamonds. The core wire is to be 3.05mm with a Polyvinyl chloride coating. (CMS710.03)

Brace and bottom rails shall be clamped toposts or post frames.

The top rail, if any, of a free standing fenceshould be continuous over two or more postsand suitable cap fittings provided.

Bent pipe frames for narrow pedestrianbridges are permitted. Bent pipe frames fornarrow pedestrian bridges should be fabricatedin two or more sections and field spliced at thetop with sleeves bolted to the frame sections.

To prevent pipe blow-ups during galvanizing,both ends of pipe should be open. Thereforebase plates should have holes in them almostequal to the pipe’s inside diameter.

305.5.1 LOADS

Wind Loads

High wind velocity: 50 years (1)

"or"

Maximum velocity: 129 km/hour at 9 metersabove ground (1)

Wind pressure (kPa)

P = 1.326Ch, derived from the formula:

P = 0.0471(1.3V)2CsChCi/1000 (2)

where V = wind velocity (km/h)

1.3 = 30% gust factor

Cs = 1.0 (Shape constant for cylindrical shapes)


3-93

Ch = height constant

Ch above terrain (mm)

.08 0 - 4500

1.0 4500 - 9000

1.1 9000 - 15 000

1.25 15 000 - 30 000

1.40 30 000 - 46 000

1.50 46 000 - 61 000

The centroid of the horizontally projected areaof the fence is to be used to determine theheight above normal terrain and the value ofCh.

Ci = ice constant which shall be taken as unity.

PROJECTED AREAS for wind forces forpolyvinyl chloride coated 3.05 mm core, 25mm mesh, wire, use 20% of the gross horizon-tally projected area.

Additional area for posts, rails and otherhardware need not be considered.

Ref. (1) Isotach’s of the U.S. The 129 km/hline covers the northwestern portion of Ohioand shall be used herein For all of Ohio.

Ref. (2) Specifications for the Design andConstruction of Structural Supports forHighway Signs, AASHTO.

306 EXPANSION DEVICES

306.1 GENERAL

Expansion devices required should provide atotal seal against penetration and moisture.

Expansion devices and their support systemssuch as end floor beams or end cross framesshall be designed for both MS18 Loading and100% impact.

For fabricated steel expansion devices, thedesigner should specify the type of steelrequired. Type of steel should be included asa plan note if requirements in the plans are notcovered by a selected standard drawing.

To protect steel expansion devices metalizingof the exposed surfaces with a protective zinccoating shall be specified. Standard drawingsdefine the requirements for metallizing. Forspecial expansion devices, plan notes will berequired to establish metallizing requirements.

306.1.1 PAY ITEM

Expansion devices, except as specificallylisted in this section, shall be paid for as item516.

For sealed expansion devices the elastomericseal, either strip or compression, shall beincluded in the pay item 516.


3-94

The plans shall clearly show what componentsare included with the expansion devices, Item516. As an example, cross frames, which arefield welded to both the superstructure girdersand the expansion devices, are part of the513/863 structural steel item. The seal isconsidered part of the expansion device andshould be included in the 516 pay item.

306.1.2 EXPANSION DEVICESWITH SIDEWALKS

On structures with sidewalks, the expansiondevices shall be the same type as furnished formain bridge deck expansion joint.

Sidewalk details for standard expansiondevices (strip seals) are shown on thestandards. For non-standard devices curbplate and sidewalk cover plate will berequired. The Curb and sidewalk platesshould be separated at the interface of thesidewalk and curb. See details on StandardDrawings EXJ-2-81M, EXJ-3-82M, EXJ-4-87M, EXJ-5-93M and EXJ-6-95M forsidewalk plates.

306.1.3 EXPANSION DEVICES;STAGE CONSTRUCTION

On projects involving stage construction,joints in the seal armor must be located andshown in the plans. At the stage constructionlines, expansion devices should requirecomplete penetration welded butt joints. Ifbutt welds will be in contact with a sealinggland the butt welded joint shall be groundflush at the contact area.

306.2 EXPANSION DEVICETYPES

306.2.1 ABUTMENT JOINTS INBITUMINOUSCONCRETE, BOX BEAMBRIDGES

This poured joint seal system is capable ofsmall expansion capability, up to 5 mm. Aplan insert sheet, Abutment Joints inBituminous Concrete Box Beam Bridges,Metric, is available from the Department.This device requires two bid items, an itemspecial and item 516.

306.2.2 ABUTMENT JOINTS ASPER AS-1-81M

A group of no or small movement joints usedfor sealing and rotational purposes is detailedon STD DRG AS-1-81M.

306.2.3 EXPANSION JOINTSUSING POLYMERMODIFIED ASPHALTBINDER

This device is generally for use on structureswith concrete or asphalt overlays and whereexpected expansion is 0 to 40 mm. A detail& plan note insert sheet, Polymer ModifiedAsphalt Expansion Joint System, is availablethrough the Office of Structural Engineering’sweb page. This item is bid as a special.

Thickness of the polymer modified joint shallbe a minimum of 50 mm and maximum of 75mm.


3-95

306.2.4 STRIP SEAL EXPANSIONDEVICES

The seal size is limited to a 125 mmmaximum. Unpainted A588M weatheringsteel should not be used in the manufacture ofthis type expansion device as A588M doesnot perform well in the atmosphericconditions an expansion device is subjectedto. Standard Drawings, EXJ-4-87M, EXJ-5-93M and EXJ-6-95M, are available. Thedesigner must ensure that all details arecovered in the plans because the standarddrawing is not inclusive for all structure types.

The strip seal shall be of one piece across thetotal width of the structure. No splices will beacceptable.

306.2.5 COMPRESSION SEALEXPANSION DEVICES

Maximum allowable seal size is 100 mm. A125 mm wide seal shall not be used sinceinstallation problems have been encountered.Compression seal expansion devices arelimited to structures with a maximum skew of15 degrees. Movement should be limited sothat the seal is not compressed greater than 60percent nor less than 20 percent.

The compression seal shall be of one pieceacross the total width of the structure. Nosplices will be acceptable. Standard DrawingsEXJ-2-81M & EXJ-3-82M give generallyused details.

306.2.6 STEEL SLIDING PLATEENDDAMS, RETIREDSTANDARD DRAWINGSD-1-69

In general steel sliding plate enddams are notrecommended for new structures. Thisexpansion device is limited to total movementof 100 mm, including movement in bothdirections. End cross frame support detailsshown on Retired Standard Drawing SD-1-69can generally still be used with all steelsupported expansion devices.

This is not a metric standard and is not forincorporation into project plans. Details, ifused from this old standard should beconverted and added to the actual plan sheets.

Sliding plates should be configured topreclude binding and bearing when the superstructure is supported on elastomeric bearings.

Unpainted A588M materials are notrecommended for construction of this type ofjoint.

306.2.7 MODULAR EXPANSIONDEVICES

Modular expansion devices may be requiredfor structures when total required movementsexceed movement capacity of a strip orcompression seal. Use of modular devicesrequires approval of the Office of StructuralEngineering.


3-96

Modular devices main load bearing beams,support beams and welds shall be designed forfatigue.

The manufacturer of the expansion deviceshall be required by plan note to submitdesign calculations showing that the devicecan meet the impact and fatigue designrequirements.

Modular devices have been known to fail atconnections due to welding and fatigue.Therefore it is recommended the followinggeneral requirements be included in anyproject plan notes:

A. Spacing of support beams shall belimited to 1000 mm centers under mainload bearing beams unless fatiguetesting of the actual welding connectiondetails has been performed to show thata greater spacing is acceptable. Thefatigue cycles should be 2,000,000 +truck load cycles or truck traffic countover the expected life of the structure.

B. Shop or field welds splicing mainbeams, or connections to the mainbeams shall be full penetration weldedand 100 percent non-destructively testedin accordance with AWS D1.5 BridgeWelding Code. Any required fieldsplices or joints and non- destructivetesting shall be located and defined inthe plans.

C. Fabricator’s of modular devices shall becertified AISC, category appropriate forthe work. Review section 302.4.1.3 andcontact the Office of StructuralEngineering for recommendations.

D. Approved manufacturer/fabricator shallsupply a qual i f ied technicalrepresentative to the jobsite during allinstallation procedures.

E. Seals shall be one continuous piecethrough the total length of the structure.

Design of support for the modular device anddeck thickness should allow for multiplestyles or designs of modular devices. Contactsuppliers and become familiar with themodular devices available.

Contact the Office of Structural Engineeringfor sample notes used on other projects.

306.2.8 TOOTH TYPE, FINGERTYPE OR NON-STANDARD SLIDINGPLATE EXPANSIONDEVICES

This is another alternate type of expansiondevice for structures where movements exceedthe capacity of either strip or compression sealdevices. Not generally recommended as thisdevice has sealing, construction, fabrication,support and installation problems. Use of thistype of device requires approval by the Officeof Structural Engineering.


3-97

Use of a tooth type expansion device alsorequires neoprene drainage troughs and asuitable drainage system to carry away thewater. Both the neoprene trough anddownspout to drainage trough connectionmust be detailed completely. Special attentionshould be paid to developing a complete sealat the downspout to trough connection.

Vulcanizing for sealing is recommended overadhesive sealing.

Finger devices shall be designed for fatigueand conform to fracture critical requirementsif the design has fracture critical componentsin it.

Fabricator’s of finger devices shall be certifiedAISC, category appropriate for the work.Review section 302.4.1.3 and contact theOffice of Structural Engineering forrecommendations.

306.3 EXPANSION DEVICEUSES - BRIDGE ORABUTMENT TYPE

306.3.1 INTEGRAL OR SEMI-INTEGRAL TYPEABUTMENTS

No allowance for temperature need be made.

The vertical joint between abutment backwalland approach slab should be finished as perStandard Drawing AS-1-81M, Detail B.

306.3.2 REINFORCEDCONCRETE SLABBRIDGES

The below table specifies joint requirements.Expansion length is defined as the total lengthif no fixed bearing exists, or length from fixedbearing to proposed expansion devicelocation, if one exists.

Expansionlength (mm)

joint required approach slabjoint

0 - 12 000 None AS-1-81Mdetail B

12 000 - 60000

None (1)

PM (2)

AS-1-81Mdetail B

60 000 + PM AS-1-81M

(1) = flexible abutments and piers (CPP-2-94M and CPA-5-94M)

(2) = abutments and/or piers fixed or rigid

PM = Polymer Modified Asphalt Joint

306.3.3 STEEL STRINGER BRIDGES

The below table specifies joint requirementsbased on expansion length defined as the totallength of structure, if no fixed bearing exists,or length from fixed bearing to proposedexpansion device location if one exists.


3-98


joint required approachslab joint

0-10 000 None AS-1-81Mdetail B

10 000-38 000 PM (1) orEXJ-4-87M

AS-1-81Mdetail B

38 000-125 000 EXJ-4-87M AS-1-81M

125 000 + TTED or MED


TTED = Tooth Type expansion device

MED = Modular Expansion Device

(1) = Stringer bridges with sidewalksshould not use polymer modifiedexpansion joint systems.

306.3.4 P R E S T R E S S E DCONCRETE I-BEAMBRIDGES



joint required approachslab joint

0-12 000 None AS-1-81Mdetail B

12 000-65 000 PM (1) orEXJ-6-95M

AS-1-81Mdetail C

65 000-150 000 EXJ-6-95M AS-1-81Mdetail C

150 000 + TTED or MED


TTED = Tooth Type expansion device


(1) = Stringer bridges with sidewalksshould not use polymer modifiedexpansion joint systems

306.3.5 NON-COMPOSITEPRESTRESSED BOXBEAM BRIDGES



3-99


joint required(2)

approachslab joint

0-12 000 PM

12 000 - 65000

PM (1) orEXJ-5-93M

AS-1-81Mdetail A,C,E

65 000-150000 EXJ-5-93M AS-1-81Mdetail C


(1) = Bridges with sidewalks should not usepolymer modified expansion jointsystems

(2) = Joint requirements are for rigid orfixed abutments. For flexibleabutments requiring no expansionmovement a PM joint is recommendedexcept for (1)

306.3.6 COMPOSITEPRESTRESSEDCONCRETE BOX BEAMBRIDGES



joint required(2)

approachslab joint

0-12 000 PM

12 000 - 65 000 PM (1) orEXJ-5-93M

AS-1-81Mdetail C, D,

F

65 000-150000 EXJ-5-93M AS-1-81Mdetail C


TTED = Tooth Type or Steel Sliding plate


(1) = Bridges with sidewalks should not usepolymer modified expansion jointsystems

(2) = Joint requirements are for rigid orfixed abutments. For flexibleabutments requiring no expansionmovement a PM joint is recommendedexcept for (1)

306.3.7 ALL TIMBERSTRUCTURES

No allowance for temperature need be made.


3-100

307 BEARINGS

307.1 GENERAL

The Department’s policy is, wheneverpossible, use laminated elastomeric bearings.

Justification, including design calculationsshowing elastomeric bearings will not beadequate for the structure, must be available.

When specialized bearings, such as pot, discor spherical, are required, the Office ofStructural Engineering has specific proposalnotes available. For specialized bearings thedesigner's detail plans should allow forpossible different bearing heights and seatwidths between manufacturer's bearings.

The notes will require modification, by thedesigner, based on the specific structure.

307.2 BEARING TYPES

307.2.1 ELASTOMERICBEARINGS

The design of elastomeric bearings shallconform to AASHTO. A design data sheet isavailable from the Office of StructuralEngineering for elastomeric bearings for steelbeam and girder bridges. Non laminatedelastomeric bearings are only acceptable ifactual design calculations support their use.

Elastomeric bearings should be designedbased on a selected durometer of either 50 or60.

The designer should specify by note in projectplans the Minimum low temperatureelastomeric grade. As AASHTO specifiesOhio to be in low temperature zone C theminimum grade specified should be Grade 3.(See note section 700.)

Elastomeric bearings should generally belimited to a 125 mm maximum elastomericheight excluding internal laminates with aminimum total height of 25 mm. The designershould evaluate greater height elastomericbearings, or elastomeric bearings with slidingsurfaces, before arbitrarily selectingspecialized, high priced pot spherical or Disctype bearings. This maximum height may bewaived by the Office of StructuralEngineering.

Elastomeric bearings for steel beam and girderbridges will require a load plate. Fieldwelding of a beam or girder to the bearingload plate should be controlled so that thetemperature of the elastomer is subjected todoes not exceed 150E C .

Elastomeric bearings with load plates, shallhave the plate beveled if the rotation and orgrade exceed the limitations of AASHTOSection 14. The load plate thickness requiredby design shall be the minimum thickness ofthe beveled plate. A nominal minimumthickness of 38 mm is recommended but notmandatory

Elastomeric bearings should not bear onunbonded steel surfaces. Therefore all steelplates in contact with an elastomeric bearingsshall be vulcanized to the bearing.


3-101

Vertical deformation of the bearings greaterthan 3 mm are to be compensated for in theelevations of the bridge bearing seats. A noteshall be required in the design plans.

Detail plans shall include the unfactored deadload, live load and total load reactions foreach elastomeric bearing design.

307.2.2 STEEL ROCKER &BOLSTER BEARINGS,RB-1-55M

Generally, this bearing type should only beused in rehabilitation projects where a matchto the existing bearing is required.

This bearing type is presented on StandardDrawing RB-1-55M. The standard drawingalso includes material and maximum loadcapacity requirements for this bearing type.

This bearing is limited to a 50 mm movementin one direction from the vertical.

The assumed rolling and sliding resistance ofrockers is 0.25 DL times r/R, where: DL is thedead load reaction on the rockers, "r" is theradius of the pin, in mm, and "R" is the radiusof the rocker, in mm.

For structures where the grade at the bearingis greater than 2 percent, the upper load plateshall require beveling to match the requiredgrade. The designer shall provide a plan detailof the beveled, upper load plate. Thethickness of the upper load plate at thecenterline of the bearing (dimension C in thestandard drawing) should be held.

Pier and abutment seats should allow thebearing base plate to achieve full seat area.The designer may choose, on structures ofextreme skew, the alternative of clipping thecorner of the bearing plate to save adding add-itional width to the pier and abutment seats.The maximum clip shall not remove morethan 1900 mm2 of bearing base plate surfacearea. The designer shall investigate that thesubstructure can accept the increased loading.

307.2.3 SLIDING BRONZE TYPE& FIXED TYPE STEELBEARINGS

Generally, this bearing type should only beused in rehabilitation projects where a matchto the existing bearing is required. The slidingbronze type expansion bearing is known tofreeze up, therefore, not providing therequired freedom of movement. This bearingtype is normally not recommended even onrehabilitation projects.

This type bearing is found on older steel beamor girder structures and is shown on StandardDrawing FSB-1-62. This standard is notcurrently active but copies are availablethrough the Department. The fixed typebearing shown on Standard Drawing FB-1-82M, originated from the old StandardDrawing FSB-1-62.

In the design of these bearings for steelbridges the assumed coefficient of friction oflubricated bronze sliding bearings is 0.10.


3-102

307.2.4 POT TYPE BEARINGS

Generally pot type bearings are capable ofhigh vertical loads and rotations up to 5degrees, depending on the design. Includedwith Teflon sliding surfaces, they are capableof expansion movement.

AASHTO has both a design and constructionsection for pot bearings. The designer shoulduse these sections and this Manual as a guidein designing, selecting and specifying a potbearing.

Justification must be provided for the use ofPot bearings. As a minimum this justificationshall include calculations showing elastomericbearings, with or without sliding surfaces, willnot be adequate for the structure.

Generic proposal notes for pot bearings areavailable through the Office of StructuralEngineering. The notes will requiremodification, by the designer, based on thespecific structure.

Pot bearings should not be used with otherbearing types.

Pot bearings are not considered proprietaryand, therefore, alternate bearing designs arenot required.

Design plans shall show design requirementsfor both vertical and horizontal loads, requiredmovements, required rotations and maximumfriction factor for the sliding surfaces.

Minimum vertical dead load needs to be 20%of total vertical load.

Design plans should take into account thepossible different sizes and heights ofdifferent manufacturer’s bearings. Abutmentand pier designs should accept thesevariances. This must be shown clearly on theplans so the contractor is informed. Finalbearing height of the supplied bearing can beachieved by fabricating additional thicknessin the bearing base plate to meet elevationrequirements or allowing for adjustment in thebearing seat’s elevation. The plans shouldshow the maximum adjustment allowed in thebearing seat’s elevation if this alternative isselected.

Plans should require anchors for bearings tobe set by use of a steel template with aminimum thickness of 6 mm.

This type of bearing generally accommodatesthe required horizontal movements by use ofPTFE (Teflon) to stainless steel slidingsurfaces. The proposal notes for this type ofbearing also include requirements for thesliding surfaces and materials. The designermust be aware that Teflon to stainless steelfriction factors vary with the loads applied.The lower the load the higher the frictionfactor.

307.2.5 DISC TYPE BEARINGS

Disc bearing are a special type "Proprietary"bearing developed for higher loadings,rotations and movements than standard typesteel rocker, bolster or elastomeric bearings.


3-103

Because Disc bearings are "Proprietary", thedesigner must design and offer alternatebearings as a bidding substitute to complywith FHWA requirements. Generally thechoice is Pot and/or Spherical type bearings.Pot bearings are the recommended alternate.

Justification must be provided for the use ofDisc bearings. As a minimum thisjustification shall include calculationsshowing elastomeric bearings, with or withoutsliding surfaces, will not be adequate for thestructure.

Generic proposal notes for disc bearings areavailable through the office of StructuralEngineering. The notes will requiremodification, by the designer, based on thespecific structure.

Disc bearings should not be used with otherbearing types.

Minimum vertical dead load needs to be 20%of total vertical load.

Design plans should take into account thepossibility of different sizes and heights ofvarious manufacturer’s bearings. Abutmentand pier designs should accept thesevariances. This must be shown clearly on theplans so the contractor is informed. Finalbearing height of the supplied bearing can beachieved by fabricating additional thicknessin the bearing base plate to meet elevationrequirements or allowing for adjustment in thebearing seat’s elevation. The plans shouldshow the maximum adjustment allowed in thebearing seat’s elevation if this alternative isselected.


This type of bearing generally accommodatesthe required horizontal movements by use ofPTFE (Teflon) to stainless steel slidingsurfaces. The proposal notes for this typebearing also include requirements for thesliding surfaces and materials. The designermust be aware that Teflon to stainless steelfriction factors vary with the loads applied.The lower the load the higher the frictionfactor.

307.2.6 SPHERICAL TYPEBEARINGS

Spherical bearings are a special type ofbearing developed for higher loadings,rotations and movements than standard typesteel rocker or bolster bearings, elastomericbearings or pot bearings.

Spherical bearings are not considered aproprietary type bearing.

Justification must be provided for the use ofSpherical bearings. As a minimum thisjustification shall include calculations show-ing elastomeric bearings, with or withoutsliding surfaces, will not be adequate for thestructure.

Generic proposal notes for spherical bearingsare available through the Office of StructuralEngineering. The notes will requiremodification, by the designer, based on thespecific structure.


3-104

Spherical bearings should not be used withother bearing types.

Design plans should take into account thepossibility of different sizes and heights ofvarious manufacturer’s bearings. Abutmentand pier designs should accept thesevariances. This must be shown clearly on theplans so the contractor is informed. Finalbearing height of the supplied bearing can beachieved by fabricating additional thicknessin the bearing base plate to meet elevationrequirements or allowing for adjustment in thebearing seat’s elevation. The plans shouldshow the maximum adjustment allowed in thebearing seat’s elevation if this alternative isselected.


This type of bearing generally accommodatesthe required horizontal movements by use ofPTFE (Teflon) to stainless steel slidingsurfaces. The proposal notes for this typebearing also include requirements for thesliding surfaces and materials. The designermust be aware that Teflon to stainless steelfriction factors vary with the loads applied.The lower the load the higher the frictionfactor.

307.3 GUIDELINES FOR USE

307.3.1 FIXED BEARINGS

307.3.1.1 FIXED TYPE STEELBEARINGS STANDARDDRAWINGS RB-1-55MOR FB-1-82M

These types of fixed bearings have been usedin the past for steel beam or girder bridges.

Fixed bearings, Standard Drawing FB-1-82M,have also been used in conjunction withlaminated elastomeric bearings acting asexpansion bearings. This is especially true inrehabilitation work where this existing fixedbearing type could possibly be salvaged.

Generally steel fixed bearings should belimited to steel beam and girder bridgestructures with a maximum 15 degree skewand 20 meter deck width.

Bolster type fixed bearings (Standard DrawingRB-1-55M) are not recommended forselection on new structures, replacementstructures or total superstructure rehabilita-tion. They may be chosen on wideningprojects to match existing bearings.

307.3.1.2 FIXED LAMINATEDELASTOMERIC - STEELBEAM BRIDGES

Fixed laminated elastomeric bearings arerecommended for use on new steel structures,replacement steel structures or totalsuperstructure rehabilitation.


3-105

A design data sheet for laminated elastomericbearings, "Laminated Elastomeric Bearingsfor Steel Beam and Girder Bridges" isavailable. This design data sheet does notlimit the size of elastomeric bearings.

Elastomeric bearings should be designedbased on selected durometer of either 50 or60.

Other laminated elastomeric bearings willrequire analysis by the designer to fit thespecific structure.

Laminated elastomeric bearings for steel beamand girder bridges shall be designed with aload plate.

For additional information see Section 307.2.1on elastomeric bearings.

307.3.1.3 FIXED LAMINATEDELASTOMERICPRESTRESSED BOXBEAMS

Laminated elastomeric bearings shall be usedfor prestressed concrete box beam bridges.


A fixed bearing condition may be assumed tobe obtained by the use of 25 mm thicklaminated elastomeric bearing pads and the in-stallation of anchor dowels with grout.


307.3.1.4 FIXED LAMINATEDELASTOMERICPRESTRESSED I-BEAM

Laminated elastomeric bearings shall be usedfor prestressed concrete I-beam bridges.

The Department has no standards for fixed orexpansion bearings for prestress I-beamsuperstructure; therefore, the designer isrequired to design the bearing.


The designer should note that prestressed I-beam bridges, whether single or multiplecontinuous spans, would generally follow thesame constraints as prestressed box beambridges.

In designing the bearing for an I-beam bridgesthe designer should verify that the attachmentof the bearing to the I-beam or any lateralrestraining devices for the bearing do notinterfere with placement of the diaphragm.Interference of the bearing with thediaphragms may cause spalling of thediaphragm and future maintenance problems.



3-106

307.3.2 EXPANSION BEARINGS

307.3.2.1 ROCKER BEARINGSSTANDARD DRAWINGRB-1-55M

This type expansion bearing (rocker) in thepast has been used on steel beam or girderbridges.

Generally, this type steel expansion bearing islimited in use to steel beam and girder bridgestructures with a maximum 15 degree skew,20 meter deck width.

Rocker type expansion bearings are notrecommended for selection on new structures,replacement structures or total superstructurerehabilitation. They may be chosen onwidening projects to match existing bearings.

Twin structures, being rehabilitated, whichhave RB-1-55M type bearings should not betied together if overall finished width is to begreater than 20 meters.

307.3.2.2 BRONZE TYPE STEELEXPANSION BEARINGS

This sliding type bearing was used in the paston some steel beam or girder structures. Basedon deleted Standard Drawing FSB-1-62 andnormally used with FB-1-82M type fixedbearing.

This bearing is not recommended for use onnew projects but may be required due to aspecial widening project requiring a match ofexisting bearings. This bearing type hasshown problems with freezing. If jacking isbeing performed on a structure the designershould consider replacing this existing type ofbearing with elastomeric bearings.

Twin structures, being rehabilitated, whichhave FSB-1-62 type bearings should not betied together if the total combined deck widthexceeds 20 meters. This bearing is notdesigned to accept transverse movement.

307.3.2.3 EXPANSIONELASTOMERICBEARINGS BEAM ANDGIRDER BRIDGES

This bearing type is recommended for use onnew structures, replacement structures or totalsuperstructure rehabilitation.

A design data sheet for laminated elastomericbearings called "Laminated ElastomericBearings for Steel Beam and Girder Bridges"is available.


Other laminated elastomeric bearings willrequire analysis by the designer to fit thespecific structure.

Laminated elastomeric bearings for steel beamand girder bridges shall be designed with aload plate.


3-107

When the decks of twin structures are beingtied together, resulting in a total structurewidth in excess of 20 meters laminatedelastomeric bearings shall be required.

307.3.2.4 EXPANSIONELASTOMERICBEARINGSPRESTRESSED BOXBEAMS

Box beam bridges shall have two elastomericbearing pads at each end of each beam. Atleast a 25 mm minimum thickness is requiredbut the bearing shall be designed for therequired movement and rotation.


On skewed bridges, 3 mm thick preformedbearing shim material, CMS 711.21, the sameplan dimensions as the bearing, should beprovided to accommodate any non-parallelismbetween bottom of beam and bridge seat.This non-parallelism between bottom of beamand bridge seat can result from camber andbeam warpage due to skew and fabrication.Generally, half as many preformed bearingpads should be specified as the number ofbearings. The preformed bearing pads shouldbe incorporated in an item 516 in theEstimated Quantities.

307.3.2.5 EXPANSIONELASTOMERICBEARINGSPRESTRESSED I-BEAMS

Unless special limitations exist, elastomericbearings should be selected to handle load,expansion and rotation requirements forprestressed concrete I-beam bridges.


In designing the bearing for an I-beam bridgesthe designer should verify that the attachmentof the bearing to the I-beam or any lateralrestraining devices for the bearing do notinterfere with placement of the diaphragm.Interference of the bearing with thediaphragms may cause spalling of thediaphragm and future maintenance problems.

307.3.3 SPECIALIZEDBEARINGS

Where specialized bearings, such as pot discor spherical, are required, the Office ofStructural Engineering has specific proposalnotes available. Justification must beprovided for the use of Pot bearings. As aminimum this justification shall includecalculations showing elastomeric bearings willnot be adequate for the structure. The noteswill require modification, by the designer,based on the specific structure.

307.3.3.1 POT BEARINGS

See Section 307.2.4 for specific requirementson Pot bearings.


3-108

307.3.3.2 DISC TYPE BEARINGS

See Section 307.2.5 for specific requirementson Disc bearings.

307.3.3.3 SPHERICAL BEARINGS

See Section 307.2.6 for specific requirementson Spherical bearings.

detail design

Documents

pedestrian bridges

railroad bridges

bikeway bridges

load requirements

design of highwaybridges

design philosophysection

design metric

single span bridges