asep summit 2012 - balili apd presentation - design of bridges
DESCRIPTION
Bridge DesignTRANSCRIPT
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Design of Reinforced Concrete Design of Reinforced Concrete Bridges as per NSCP 2010 Bridges as per NSCP 2010 VolVol 22By Alden Paul D. Balili, MSCEDLSU-M
OutlineOutline
y Overviewy Highlight of Changes per Chaptery Does not include geotechnical provisions
Who is this for?Who is this for?
y Aspiring Bridge Engineersy Bridge Engineers
Aspiring Bridge Engineer Bridge Engineers
INTRODUCTION TO INTRODUCTION TO BRIDGE DESIGN: BRIDGE DESIGN: SUPERSTRUCTURE PARTSSUPERSTRUCTURE PARTS
Design of Reinforced Concrete Bridges as per NSCP 2010 Vol 2
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Please Note:Please Note:
y Longitudinal direction means in the direction parallel to traffic.y Transverse direction means in the direction
perpendicular to traffic
SUPERSTRUCTURESUPERSTRUCTURE
Longitudinal
Transverse
SUPERSTRUCTURESUPERSTRUCTURE
y Superstructure Section
SUPERSTRUCTURESUPERSTRUCTURE
yWEARING SURFACE
WearingSurface
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SUPERSTRUCTURESUPERSTRUCTURE
yWEARING SURFACE is the portion of the deck which resists traffic
wear. Could be a separate layer of bituminous material,
or Is integral with the deck, (additional thickness
added to the deck)
SUPERSTRUCTURESUPERSTRUCTURE
y DECK
Deck
SUPERSTRUCTURESUPERSTRUCTURE
y DECK Its main function is to distribute loads transversely
along the bridge cross section. Usually integrated with the primary members The wearing surface and barriers are placed on top
of this
SUPERSTRUCTURESUPERSTRUCTURE
y PRIMARY MEMBERS
PrimaryMembers
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SUPERSTRUCTURESUPERSTRUCTURE
y PRIMARY MEMBERS Distributes loads longitudinally and are designed to
resist flexure and shear from traffic loads. Otherwise known as stringers or girders.
SUPERSTRUCTURESUPERSTRUCTURE
y SECONDARY MEMBERS
SecondaryMembers
SUPERSTRUCTURESUPERSTRUCTURE
y SECONDARY MEMBERS Bracing between primary members in the
transverse direction. Helps distribute the loads between primary
members. For prestressed concrete bridges, they are often
called diaphragms. Diaphragms between the ends are called internal
diaphragms. While Diaphragms at the ends are called external diaphragm.
SUPERSTRUCTURESUPERSTRUCTURE
y TRAFFIC BARRIERS
TrafficBarriers
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SUPERSTRUCTURESUPERSTRUCTURE
y TRAFFIC BARRIERSis a device which protects wayward vehicles
from running over the bridge. when a pedestrian walkway is present
protects pedestrians from wayward vehicles.
INTRODUCTION TO INTRODUCTION TO BRIDGE DESIGN: BRIDGE DESIGN: SUBSTRUCTURE PARTSSUBSTRUCTURE PARTS
Design of Reinforced Concrete Bridges as per NSCP 2010 Vol 2
SUBSTRUCTURESUBSTRUCTURE SUBSTRUCTURESUBSTRUCTURE
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SUBSTRUCTURESUBSTRUCTURE
y PIER
SUBSTRUCTURESUBSTRUCTURE
y PIER ..are structures which support the superstructure
at intermediate points between the end supports. A pier which has multiple columns with a beam
joining them on top is usually called a column bent.
SUBSTRUCTURESUBSTRUCTURE
y CAP BEAM (note: column bent shown)
SUBSTRUCTURESUBSTRUCTURE
y CAP BEAM ..the top beam in a bent which ties together the
supporting columns or piles.
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SUBSTRUCTURESUBSTRUCTURE
y Abutment
SUBSTRUCTURESUBSTRUCTURE
y Abutment ..are earth-retaining structures which support the
superstructure at the beginning and end of the bridge. Comes in a variety of forms
SUBSTRUCTURESUBSTRUCTURE
y SHEAR KEY
SUBSTRUCTURESUBSTRUCTURE
y SHEAR KEY ..a short element attached to the abutment or pier
cap beam which prevents the superstructure from sliding transversely against lateral loads
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SUBSTRUCTURESUBSTRUCTURE
y BEARINGS
SUBSTRUCTURESUBSTRUCTURE
y BEARINGS .. are mechanical systems which transmit the
vertical and horizontal loads of the superstructure to the substructure. This is usually composed of flexible material to
accommodate movements of the superstructure and substructure.
SUBSTRUCTURESUBSTRUCTURE
y PEDESTAL
SUBSTRUCTURESUBSTRUCTURE
y PEDESTAL .. Is a short column under the bearings. Usual function is to provide a level surface and
achieve the desired elevation for the bearing .
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SUBSTRUCTURESUBSTRUCTURE
y STEM
SUBSTRUCTURESUBSTRUCTURE
y STEM .. A cantilever wall providing protection from the
earth especially if there is a roadway underneath the bridge (an underpass).
SUBSTRUCTURESUBSTRUCTURE
y BACKWALL
SUBSTRUCTURESUBSTRUCTURE
y BACKWALL .. An extension of the stem which serves as
protection from the earth for the ends of the superstructure.
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SUBSTRUCTURESUBSTRUCTURE
yWINGWALL
SUBSTRUCTURESUBSTRUCTURE
yWINGWALL .. Is attached to the backwall. is designed to assist in confining the soil behind
the abutment.
SUBSTRUCTURESUBSTRUCTURE
y APPROACH SLAB
SUBSTRUCTURESUBSTRUCTURE
y Note: Approach is the section of roadway before and after the structurey Approach Slab .. Is a slab located on the approaches and
supported by the abutment used to prevent settlement of the approach pavement.
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SUBSTRUCTURESUBSTRUCTURE
y FOOTING
SUBSTRUCTURESUBSTRUCTURE
y Footing .. A component which transmits the loads from the
substructure and superstructure to the soil or the piles underneath. A footing supported without piles and resting on
soil is called a spread footing..A footing supported with piles is called a pile
cap
SUBSTRUCTURESUBSTRUCTURE
y PILES
SUBSTRUCTURESUBSTRUCTURE
y PILES .. Are used when the bearing capacity under a
footing is incapable of carrying the gravity loads. .. Extend below to a stronger soil layer or the
underlying rock layer to provide adequate support and to prevent settlement.There are different types of piles ranging from
concrete to steel
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INTRODUCTION TO INTRODUCTION TO NEW NEW NSCPNSCP 2010 2010 VOLVOL 2 2 CODECODE
Design of Reinforced Concrete Bridges as per NSCP 2010 Vol 2
IntroductionIntroduction
y The new NSCP 2010 code adopts the AASHTO LRFD Bridge Design Specifications 2007.y It should be noted that the latest
AASHTO code is 2010. However, revisions from 2007 to 2010 are minimal.
IntroductionIntroduction
y The new NSCP 2010 code adopts the AASHTO LRFD Bridge Design Specifications 2007.y It should be noted that the latest
AASHTO code is 2010. However, revisions from 2007 to 2010 are minimal.
Chapters adapted from Chapters adapted from AASHTO LRFD 2007AASHTO LRFD 2007
AASHTO LRFD BRIDGE 2007 NSCP 2010 Vol 2
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Where are they now?Where are they now?
NSCP Vol 2 - 1997 NSCP 2010 Vol 2
1. General Provisions
2. General Features of Design
3. Loads
4. Foundations
5. Retaining Walls
6. Culverts
7. Substructures
8. Reinforced Concrete
9. Prestressed Concrete
10. Structural Steel
11. Aluminum Design
12. Soil-Corrugated Metal Structure Interaction Systems
13. Timber Structures
14. Elastomeric Bearings
15. TFE Bearing Surface
16. Steel Tunnel Liner Plates
17. Soil Reinforced Concrete Structure Interaction Systems
18. Soil-Thermoplastic Pipe Interaction System
19. Pot Bearings
20. Disc Bearings
21. Seismic Design
Where are they now?Where are they now?
NSCP Vol 2 - 1997 NSCP 2010 Vol 2
1. General Provisions2. General Features of Design
3. Loads
4. Foundations
5. Retaining Walls
6. Culverts
7. Substructures
8. Reinforced Concrete
9. Prestressed Concrete
10. Structural Steel
11. Aluminum Design
12. Soil-Corrugated Metal Structure Interaction Systems
13. Timber Structures
14. Elastomeric Bearings
15. TFE Bearing Surface
16. Steel Tunnel Liner Plates
17. Soil Reinforced Concrete Structure Interaction Systems
18. Soil-Thermoplastic Pipe Interaction System
19. Pot Bearings
20. Disc Bearings
21. Seismic Design
Where are they now?Where are they now?
NSCP Vol 2 - 1997 NSCP 2010 Vol 2
1. General Provisions
2. General Features of Design3. Loads
4. Foundations
5. Retaining Walls
6. Culverts
7. Substructures
8. Reinforced Concrete
9. Prestressed Concrete
10. Structural Steel
11. Aluminum Design
12. Soil-Corrugated Metal Structure Interaction Systems
13. Timber Structures
14. Elastomeric Bearings
15. TFE Bearing Surface
16. Steel Tunnel Liner Plates
17. Soil Reinforced Concrete Structure Interaction Systems
18. Soil-Thermoplastic Pipe Interaction System
19. Pot Bearings
20. Disc Bearings
21. Seismic Design
Where are they now?Where are they now?
NSCP Vol 2 - 1997 NSCP 2010 Vol 2
1. General Provisions
2. General Features of Design
3. Loads4. Foundations
5. Retaining Walls
6. Culverts
7. Substructures
8. Reinforced Concrete
9. Prestressed Concrete
10. Structural Steel
11. Aluminum Design
12. Soil-Corrugated Metal Structure Interaction Systems
13. Timber Structures
14. Elastomeric Bearings
15. TFE Bearing Surface
16. Steel Tunnel Liner Plates
17. Soil Reinforced Concrete Structure Interaction Systems
18. Soil-Thermoplastic Pipe Interaction System
19. Pot Bearings
20. Disc Bearings
21. Seismic Design
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Where are they now?Where are they now?
NSCP Vol 2 - 1997 NSCP 2010 Vol 2
1. General Provisions
2. General Features of Design
3. Loads (Distribution Factors)4. Foundations
5. Retaining Walls
6. Culverts
7. Substructures
8. Reinforced Concrete
9. Prestressed Concrete
10. Structural Steel
11. Aluminum Design
12. Soil-Corrugated Metal Structure Interaction Systems
13. Timber Structures
14. Elastomeric Bearings
15. TFE Bearing Surface
16. Steel Tunnel Liner Plates
17. Soil Reinforced Concrete Structure Interaction Systems
18. Soil-Thermoplastic Pipe Interaction System
19. Pot Bearings
20. Disc Bearings
21. Seismic Design
Where are they now?Where are they now?
NSCP Vol 2 - 1997 NSCP 2010 Vol 2
1. General Provisions
2. General Features of Design
3. Loads
4. Foundations
5. Retaining Walls
6. Culverts
7. Substructures
8. Reinforced Concrete9. Prestressed Concrete10. Structural Steel
11. Aluminum Design
12. Soil-Corrugated Metal Structure Interaction Systems
13. Timber Structures
14. Elastomeric Bearings
15. TFE Bearing Surface
16. Steel Tunnel Liner Plates
17. Soil Reinforced Concrete Structure Interaction Systems
18. Soil-Thermoplastic Pipe Interaction System
19. Pot Bearings
20. Disc Bearings
21. Seismic Design
Where are they now?Where are they now?
NSCP Vol 2 - 1997 NSCP 2010 Vol 2
1. General Provisions
2. General Features of Design
3. Loads
4. Foundations
5. Retaining Walls
6. Culverts
7. Substructures
8. Reinforced Concrete
9. Prestressed Concrete
10. Structural Steel11. Aluminum Design12. Soil-Corrugated Metal Structure Interaction Systems
13. Timber Structures14. Elastomeric Bearings
15. TFE Bearing Surface
16. Steel Tunnel Liner Plates
17. Soil Reinforced Concrete Structure Interaction Systems
18. Soil-Thermoplastic Pipe Interaction System
19. Pot Bearings
20. Disc Bearings
21. Seismic Design
Where are they now?Where are they now?
NSCP Vol 2 - 1997 NSCP 2010 Vol 2
1. General Provisions
2. General Features of Design
3. Loads4. Foundations
5. Retaining Walls
6. Culverts
7. Substructures
8. Reinforced Concrete9. Prestressed Concrete
10. Structural Steel
11. Aluminum Design
12. Soil-Corrugated Metal Structure Interaction Systems
13. Timber Structures
14. Elastomeric Bearings
15. TFE Bearing Surface
16. Steel Tunnel Liner Plates
17. Soil Reinforced Concrete Structure Interaction Systems
18. Soil-Thermoplastic Pipe Interaction System
19. Pot Bearings
20. Disc Bearings
21. Seismic Design
For decks of composite systems
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Where are they now?Where are they now?
NSCP Vol 2 - 1997 NSCP 2010 Vol 2
1. General Provisions
2. General Features of Design
3. Loads
4. Foundations
5. Retaining Walls
6. Culverts
7. Substructures8. Reinforced Concrete
9. Prestressed Concrete
10. Structural Steel
11. Aluminum Design
12. Soil-Corrugated Metal Structure Interaction Systems
13. Timber Structures
14. Elastomeric Bearings
15. TFE Bearing Surface
16. Steel Tunnel Liner Plates
17. Soil Reinforced Concrete Structure Interaction Systems
18. Soil-Thermoplastic Pipe Interaction System
19. Pot Bearings
20. Disc Bearings
21. Seismic Design
Where are they now?Where are they now?
NSCP Vol 2 - 1997 NSCP 2010 Vol 2
1. General Provisions
2. General Features of Design
3. Loads
4. Foundations
5. Retaining Walls6. Culverts
7. Substructures
8. Reinforced Concrete
9. Prestressed Concrete
10. Structural Steel
11. Aluminum Design
12. Soil-Corrugated Metal Structure Interaction Systems
13. Timber Structures
14. Elastomeric Bearings
15. TFE Bearing Surface
16. Steel Tunnel Liner Plates
17. Soil Reinforced Concrete Structure Interaction Systems
18. Soil-Thermoplastic Pipe Interaction System
19. Pot Bearings
20. Disc Bearings
21. Seismic Design (Mononobe Okabe)
Where are they now?Where are they now?
NSCP Vol 2 - 1997 NSCP 2010 Vol 21. General Provisions
2. General Features of Design
3. Loads
4. Foundations
5. Retaining Walls
6. Culverts7. Substructures
8. Reinforced Concrete
9. Prestressed Concrete
10. Structural Steel
11. Aluminum Design
12. Soil-Corrugated Metal Structure Interaction Systems
13. Timber Structures
14. Elastomeric Bearings
15. TFE Bearing Surface
16. Steel Tunnel Liner Plates17. Soil Reinforced Concrete Structure
Interaction Systems18. Soil-Thermoplastic Pipe Interaction
System19. Pot Bearings
20. Disc Bearings
21. Seismic Design
Where are they now?Where are they now?
NSCP Vol 2 - 1997 NSCP 2010 Vol 2
1. General Provisions
2. General Features of Design
3. Loads (Railing load provisions)4. Foundations
5. Retaining Walls
6. Culverts
7. Substructures
8. Reinforced Concrete
9. Prestressed Concrete
10. Structural Steel
11. Aluminum Design
12. Soil-Corrugated Metal Structure Interaction Systems
13. Timber Structures
14. Elastomeric Bearings
15. TFE Bearing Surface
16. Steel Tunnel Liner Plates
17. Soil Reinforced Concrete Structure Interaction Systems
18. Soil-Thermoplastic Pipe Interaction System
19. Pot Bearings
20. Disc Bearings
21. Seismic Design
(Has a lot of new content regarding railings)
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Where are they now?Where are they now?
NSCP Vol 2 - 1997 NSCP 2010 Vol 2
1. General Provisions
2. General Features of Design
3. Loads
4. Foundations
5. Retaining Walls
6. Culverts
7. Substructures
8. Reinforced Concrete
9. Prestressed Concrete
10. Structural Steel
11. Aluminum Design
12. Soil-Corrugated Metal Structure Interaction Systems
13. Timber Structures
14. Elastomeric Bearings15. TFE Bearing Surface
16. Steel Tunnel Liner Plates
17. Soil Reinforced Concrete Structure Interaction Systems
18. Soil-Thermoplastic Pipe Interaction System
19. Pot Bearings20. Disc Bearings21. Seismic Design
SECTION HIGHLIGHTS SECTION HIGHLIGHTS CHAPTER 01CHAPTER 01
Design of Reinforced Concrete Bridges as per NSCP 2010 Vol 2
Chapter 01 HighlightsChapter 01 Highlights
y Description of the different design limit states Service Limit State Fatigue and Fracture Limit State Strength Limit State Extreme Event Limit States
Chapter 01 HighlightsChapter 01 Highlights
y Description of the different design limit states Service Limit Statex Restrictions on stress, deformation and crack width
under regular service conditions.
Fatigue and Fracture Limit State Strength Limit State Extreme Event Limit States
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Chapter 01 HighlightsChapter 01 Highlights
y Description of the different design limit states Service Limit State Fatigue and Fracture Limit Statex Restrictions on stress range as a result of a single
design truck occurring at the number of expected stress range cycles. This is to prevent crack growth due to repetitive loading
Strength Limit State Extreme Event Limit States
Chapter 01 HighlightsChapter 01 Highlights
y Description of the different design limit states Service Limit State Fatigue and Fracture Limit State Strength Limit Statex Strength and stability are provided to resist force
combinations that the bridge is expected to experience.
Extreme Event Limit States
Chapter 01 HighlightsChapter 01 Highlights
y Description of the different design limit states Service Limit State Fatigue and Fracture Limit State Strength Limit State Extreme Event Limit Statesx Ensures structural survival of a bridge during the
following extreme events (Earthquake, floor, ship and vehicle collision)
FYI: FatigueFYI: Fatigue
yWhat is fatigue? Slow degradation of materials due to
repetitive loading and resulting stress reversals. A good example is a paper clip bent back and
forth till failure
Bend up
Bend down
Repeat to failure!
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FYI: FatigueFYI: Fatigue
yWhat is fatigue? Hence, the term stress range is used to
indicate the extreme stresses (+ or - ) a member goes through. Ex: Higher stress range is experienced, when a
section undergoes both positive and negative moment!
-
+
SECTION HIGHLIGHTS SECTION HIGHLIGHTS CHAPTER 02: GENERAL CHAPTER 02: GENERAL DESIGN FEATURESDESIGN FEATURES
Design of Reinforced Concrete Bridges as per NSCP 2010 Vol 2
Chapter 02Chapter 02
y Generally, this chapter indicates required clearances and geometric requirements for bridges as specified by AASHTO.y Requirements for Hydrology analysis are
also indicated.
SECTION HIGHLIGHTS SECTION HIGHLIGHTS CHAPTER 03: LOADS CHAPTER 03: LOADS AND LOAD FACTORSAND LOAD FACTORS
Design of Reinforced Concrete Bridges as per NSCP 2010 Vol 2
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Chapter 03 LoadsChapter 03 Loads
y Things to be discussed Loads and Load Combinations The New Design Truck New Seismic Load Provisions Shrinkage, Creep and Temperature
Chapter 03 LoadsChapter 03 Loads
y Load listPERMANENT LOADS TRANSIENT LOADS
Chapter 03 LoadsChapter 03 Loads
y Load Combinations Strength Strength I Normal vehicular use w/o wind Strength II Special vehicle use w/o wind Strength III No vehicle use with wind
velocity > 90 km/h Strength IV High dead load to live load ratio Strength V Normal vehicular use with wind
= 90 km/h
Chapter 03 LoadsChapter 03 Loads
y Load Combinations Strength
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Chapter 03 LoadsChapter 03 Loads
y Load Combinations Extreme Event Extreme Event 1 Earthquake combination Extreme Event II Load combination
considering the extreme effects of the following (vessel colission, extreme flood) with reduced live load.
Chapter 03 LoadsChapter 03 Loads
y Load Combinations Extreme Event
Chapter 03 LoadsChapter 03 Loads
y Load Combinations Service Service I Normal Bridge Operation w/ 90
kph wind. Used for Reinforced Concrete Crack Control Service II Control of yielding of steel
structures and slip of slip-critical connections Service III Crack control for prestressed
concrete superstructures Service IV Crack control for prestressed
columns/piles
Chapter 03 LoadsChapter 03 Loads
y Load Combinations Service
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Chapter 03 LoadsChapter 03 Loads
y Variable load factors. For certain combinations, variable factors are
used to ensure that members have adequate strength for all possible conditions.
Chapter 03 LoadsChapter 03 Loads
y Variable load factors.
Chapter 03 LoadsChapter 03 Loads
y Example of Variable Load Factors
1.25 DC +LL+WA+FR+EQ0.9 DC +LL+WA+FR+EQ
Ex: Lower gravity loads might result in more conservative column design
Chapter 03 LoadsChapter 03 Loads
y The New Design Truck
Subject to Dynamic Load Allowance (or impact factor)
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Chapter 03 LoadsChapter 03 Loads
y Lane Load = 9.3 kN/m distributed over 3m width
Not subject to Dynamic Load Allowance (or impact factor)
9.3 kN/m
3m
Bridges Bridges Standard Trucks LRFDStandard Trucks LRFD
y Note that the new truck used by the latest LRFD code is called the HL 93. Note that the new code prescribes that truck and lane load are concurrenty HL-93 Standard Shown Below
9.3 kN/m lane load
Bridges Bridges Standard Trucks LRFDStandard Trucks LRFDy For HL93 a new truck for negative moment is
also prescribed. The axle loads are 90% of that for the single trucky HL-93 for Negative moment and interior pier
reactions Shown Below
4300mm 4300mm15000mm MIN
31.5 kN 130.5 kN 130.5 kN 31.5 kN 130.5 kN 130.5 kN
9.3 kN/m lane load
Chapter 03 LoadsChapter 03 Loadsy To take into account dynamic effects (aka the
additional force due to vibration), Dynamic Load allowance (DLA) factor is added.y The dynamic factor to be used are shown
below
Note that the impact factor is now constant and not variable with the span.
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Chapter 03 LoadsChapter 03 Loads
y To apply the DLA, the wheel loads could be multiplied by (1+DLA Factor) prior to analysis
Before DLA
After DLA = 33%(Multiply original value by 1.33)
46550 N 192850 N 192850 N
Chapter 03 Loads Chapter 03 Loads -- EarthquakeEarthquake
y In Chapter 3, the basic parameters are specified for EQ load computation. These are Acceleration Coefficient Importance Categories Site Effects Response Modification Factor
Bridges : Earthquake loadsBridges : Earthquake loads
y Earthquake Majority of the Philippines is classified as seismic zone 4
(Acceleration Coefficient = 0.4) Earthquake Inertia forces are caused by lateral and vertical
movement of the ground AASHTO 2007 adopts spectral maps for the design
acceleration coefficient As of the moment, spectral maps are still unavailable for the
Philippines and most of the country will still be using an acceleration coefficient of 0.4 (except for the Palawan area).
Bridges : Bridges : Earthquake LoadsEarthquake Loadsy Spectral Map from
NSCP 1997 Vol 2 Bridges
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Bridges : Earthquake LoadsBridges : Earthquake Loads
y Earthquake Earthquake can attack in the two principal directions:
longitudinal and transverse. Codes specify the following load cases for earthquake to
cover earthquakes which attack in a diagonal direction
x 100% Long + 30% Transx 30% Long + 100% Trans
Bridges : Earthquake LoadsBridges : Earthquake Loads
y Earthquake (Procedure using Single Mode) 1) Apply a unit uniform load on the structure. Call this
po(x)
Bridges : Earthquake LoadsBridges : Earthquake Loads
y Earthquake (Procedure using Single Mode) 1) Apply a unit uniform load on the structure. Call this
po(x)
Bridges : Earthquake LoadsBridges : Earthquake Loads
y Earthquake (Procedure using Single Mode) 2) Compute the corresponding deflections due to unit
uniform load. Call these deflection vs(x)
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Bridges : Earthquake LoadsBridges : Earthquake Loads
y Earthquake (Procedure using Single Mode) 3) Compute uniform load per unit length of structure. Call
it w(x)
W(x)
Bridges : Earthquake LoadsBridges : Earthquake Loads
y Earthquake (Procedure using Single Mode) 4)
Bridges : Earthquake LoadsBridges : Earthquake Loads
y Earthquake (Procedure using Single Mode) 5) Compute the Period of vibration
Bridges : Earthquake LoadsBridges : Earthquake Loads
y Earthquake (Procedure using Single Mode) 5) Compute the Elastic Seismic Response coefficient.
A = Acceleration coefficient S = Site coefficient, this is dependent on the soil of the site
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Bridges : Earthquake LoadsBridges : Earthquake Loads
y Earthquake (Procedure using Single Mode) 5) Site coefficient valuesx S = 1.0 for rock type foundationx S = 1.2 for stiff clay or deep cohesionless soilx S = 1.5 for soft to medium-stiff claysx S = 2.0 or soft clays or silts
Bridges : Earthquake LoadsBridges : Earthquake Loads
y Earthquake (Procedure using Single Mode) 6) Compute the actual uniform load on the bridge due to
earthquake
Bridges : Earthquake LoadsBridges : Earthquake Loads
y Earthquake (Procedure using Single Mode) 6) It should be noted, that the procedure computes the
elastic response of the structure. To consider the dissipation of the earthquake force due to
formation of plastic hinges, the forces computed must be divided by R (the response modification factor)
Bridges : Earthquake LoadsBridges : Earthquake Loads
y Earthquake (Procedure using Single Mode) 6) R factors
Note the different factors given the importance of the bridge
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Bridges: Earthquake LoadsBridges: Earthquake Loads
y Multiple column bent
Bridges: Earthquake LoadsBridges: Earthquake Loads
y Single Column
Bridges : Earthquake LoadsBridges : Earthquake Loads
y Lateral Loads come from the following Earthquake (Procedure for estimating forces)x 7) Finally, we must check the overstrength requirements so that the
columns yield first before the cap beam
Bridges : Earthquake LoadsBridges : Earthquake Loads
y Lateral Loads come from the following Earthquake (Procedure for estimating forces)x 7) Why column hinging? (Contrary to buildings)
As per the Paper Structural rehabilitation with advanced composites by F. Seible
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Bridges : Earthquake LoadsBridges : Earthquake Loads
y Lateral Loads come from the following Earthquake (Procedure for estimating forces)x 7) The plastic hinges must form in the column before the beamx To do this we require that the Mn of the cap beam is greater than 1.3
x Mn of the column at a joint.x Also in computing Mn of the column, fy = 1.25 x original value of fy to
account for strain hardeningx Also to prevent the occurrence of shear failure before flexural failure,
the whole pier system must be designed for a lateral shear force which gives a moment equal to 1.3 Mn of the column (with yield strength 1.25fy)
Bridges : Earthquake LoadsBridges : Earthquake Loads
y Designing a pier for ductility. Moment failure must precede shear failure Plastic hinges in the columns and not the beams
Bridges : Earthquake LoadsBridges : Earthquake Loads
y Designing a pier for ductility Longitudinal Forces. Compute EQ forces in the pier Get the dead load on the columns (Use Combination Get corresponding 1.3 Mn for axial load due to dead load Get Shear force at top (Call it Vo), that would produce a
moment in the columns equal to 1.3 Mn
Compare Vo with the EQ forces to get max shear
Bridges : Earthquake LoadsBridges : Earthquake Loads
y Designing a pier for ductility Transverse Forces. 1. Compute EQ forces in the pier2. Get the dead load on the columns (Use Combination 3. Get corresponding 1.3 Mn for axial load for each column due to
dead load4. Get corresponding V that would produce a moment 1.3 Mn for each
column. Add all these Vs to produce Vo5. Using Vo and the dead loads, compute the new axial loads on the
structure.6. Recompute the 1.3Mn for each column given the new axial loads.
Compute the corresponding Vo as per step 57. The recomputed Vo will now be compared with the shear in step 4.
If not within 10% repeat step 3.
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Chapter 03 Chapter 03 -- Creep, Shrinkage and Creep, Shrinkage and TemperatureTemperaturey For integral bridges, it is important to
compute the effect of creep, shrinkage and temperature due to secondary effects induced by the fixed ends.y The next slides will illustrate the effect of
secondary stresses on the structure
FYI: Secondary StressesFYI: Secondary Stresses
y Given a Bar with length L with one side with no restraints.y If hotter, bar will expandy If colder, bar will contracty The additional or subtracted length, could be expressed as D 'T L
y Please note that under these conditions, no stress is induced on the bar
FYI: Secondary StressesFYI: Secondary Stresses
y Given a Bar with length L with restraints at both ends.y If hotter, bar cant expand, because of this what kind of stress is induced? Compression!
y If colder, bar cant contract, because of this tension stress is induced at each unit element of the bar
Chapter 03 Chapter 03 -- Creep, Shrinkage and Creep, Shrinkage and TemperatureTemperaturey As shown on the previous slides, due to
restraint, there are stresses induced due to creep shrinkage and temperature.y For RC bridges, since we are controlling
tension, the combination with shrinkage and colder temperature will govern the design!
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Chapter 03 Chapter 03 -- Creep, Shrinkage and Creep, Shrinkage and TemperatureTemperaturey The major induced deformation loads are
the following
y The magnitude of these forces were not previously given in the standard specifications for bridges (NSCP Vol2 1997)
Chapter 03 Chapter 03 -- Creep, Shrinkage and Creep, Shrinkage and TemperatureTemperaturey Uniform Temperature Change (TU) Describes the seasonal change in temperature
for a bridge. Ex: If a bridge in PH was constructed at a
temperature of 30o during summer, TU effects would be large during the cold months like December (say 20o temperatures).
Chapter 03 Chapter 03 -- Creep, Shrinkage and Creep, Shrinkage and TemperatureTemperaturey Temperature Gradient
(TG) Due to the difference of
exposure to the elements of the surface and the underside of the bridge, difference in temperature could occur. Common occurrence is
the surface is hotter than the rest of the depth of the bridge or the surface is colder than the rest of the depth.
Hotter at top
Less hot at the bottom
Chapter 03 Chapter 03 -- Creep, Shrinkage and Creep, Shrinkage and TemperatureTemperaturey Shrinkage (SH) Shrinkage occurs in concrete and is due to
the loss of moisture. Shrinkage is composed of two partsx Overall Shrinkagex Differential shrinkage for Composite Decks
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Chapter 03 Chapter 03 -- Creep, Shrinkage and Creep, Shrinkage and TemperatureTemperaturey Shrinkage (SH) Overall shrinkage is the general shrinkage
being experienced by the section Differential shrinkage occurs due to the
difference in age of concrete in composite members. In the section below, the deck slab would shrink more because it is newer.
Chapter 03 Chapter 03 -- Creep, Shrinkage and Creep, Shrinkage and TemperatureTemperaturey Creep (CR) Creep is the additional deformation due to
sustained loading. Since dead load and internal prestress forces
are intended to be there forever, they induce siginificant amount of creep effects.
Chapter 03 Chapter 03 -- Creep, Shrinkage and Creep, Shrinkage and TemperatureTemperaturey Creep (CR) If the ends of a beam are restrained, creep
due to dead load + prestress may induce positive moments at the ends. SECTION HIGHLIGHTS SECTION HIGHLIGHTS
CHAPTER 04: LOADS CHAPTER 04: LOADS AND LOAD FACTORSAND LOAD FACTORS
Design of Reinforced Concrete Bridges as per NSCP 2010 Vol 2
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Chapter 04Chapter 04
y This chapter recommends analysis techniques to be used for bridges.y Things to be discussed: Equivalent Strips for Deck Analysis Distribution Factors for Gravity Loads Dynamic Analysis Specifications for EQ Loads
Chapter 04Chapter 04
y Equivalent Strips for deck analysis. It is common for deck slabs to primarily span
in the transverse direction The bridge code specifies the equivalent
width of this strip
Moment Diagram
A A
Section A-A
Gir
der
Gir
der
P
Eq. W
idth
Chapter 04Chapter 04
y Equivalent Strips for deck analysis. Equivalent widths as per code
Chapter 04Chapter 04
y Distribution Factors approximate the amount of shear and moment that would go to each girder
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Chapter 4Chapter 4
y Common Steps for Moment and Shear1. Get the moment produced by the axle
loads of the truck (note that previously, we use wheel loads for the moment)
2. Multiply the moment by the distribution factor prescribed by the AASHTO code
Live LoadsLive Loads
y Some important terms to note:
Axle Load Wheel Load
Chapter 04 Chapter 04 Distribution FactorsDistribution Factors
y Table of Distribution factors for moment in interior concrete girders.
WhereS = Spacing, mmTs = thickness of slab, mmL = Span, mmNb = number of beamsKg = factor as detailed on the next page
Limitations
Interior
Chapter 04 Chapter 04 Distribution FactorsDistribution Factors
y Factor Kg
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Chapter 04 Chapter 04 Distribution FactorsDistribution Factors
y Table of Distribution factors for Shear in interior concrete girders.
WhereS = Spacing, mmTs = thickness of slab, mmL = Span, mmNb = number of beamsKg = factor as detailed on the next page
Interior
Chapter 04 Chapter 04 Distribution FactorsDistribution Factors
y For exterior girders, the moment and shear is computed by getting the reaction on the exterior girder when the wheel loads are placed 0.6m from the parapet.
0.6m
Chapter 04 Chapter 04 Dynamic AnalysisDynamic Analysisy The latest code requires a different
refinement of analysis depending on the bridge importance.y Before we proceed the following acronyms
are used SM Single Mode UL Uniform load elastic method (simplest
method for EQ loads) MM Multimode Elastic Method (similar to
response spectrum analysis) TH Time History Method
Chapter 04 Chapter 04 Dynamic AnalysisDynamic Analysis
y Requirements as per code for seismic zone 4
Note that TH = time history is required for critical bridges. However, this would most likely be revised due to the lack of a time history record for the Philippines.
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SECTION HIGHLIGHTS SECTION HIGHLIGHTS CHAPTER 05: CONCRETE CHAPTER 05: CONCRETE STRUCTURESSTRUCTURES
Design of Reinforced Concrete Bridges as per NSCP 2010 Vol 2
Chapter 05 Chapter 05 Concrete StructuresConcrete Structures
y Provisions for both reinforced and prestressed concrete are now included in this chapter.y Since equations given for this chapter are
common for RC design, only the following will be discussed: Provisions for Crack Control Allowable Stresses for Prestressed Beams Cover Requirements for Reinforcement
Chapter 05 Chapter 05 Concrete StructuresConcrete Structures
y To limit cracking in concrete, the bridge code specifies a minimum amount of spacing which depends on the stress on the steel reinforcement.
Chapter 05 Chapter 05 Concrete StructuresConcrete Structuresy Note that Class 1 exposure is equivalent to
limiting the crack width to 0.43mm. The factor Je can be changed accordingly to the desired crack width. (Ex: a Je = 0.5 corresponds to crack width of 0.22mm.)
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Chapter 05 Chapter 05 Concrete StructuresConcrete Structures
y Recall that there are multiple stages in the design of a prestress concrete girder.These are Transfer Stage Deck is Cast Service Stage
Chapter 05 Chapter 05 Concrete StructuresConcrete Structures
y Transfer Stage Forces
Chapter 05 Chapter 05 Concrete StructuresConcrete Structures
y Deck is Cast
Chapter 05 Chapter 05 Concrete StructuresConcrete Structures
y Service Stage
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Chapter 05 Chapter 05 Concrete StructuresConcrete Structures
y For each stage the bridge code specifies limits on the stresses on the girder. Limits for Compressive Stress at Transfer
Chapter 05 Chapter 05 Concrete StructuresConcrete Structures
y For each stage the bridge code specifies limits on the stresses on the girder. Limits for Tensile Stress at transfer
Chapter 05 Chapter 05 Concrete StructuresConcrete Structures
y For each stage the bridge code specifies limits on the stresses on the girder. Limits for Compressive Stress at Service
Chapter 05 Chapter 05 Concrete StructuresConcrete Structures
y For each stage the bridge code specifies limits on the stresses on the girder. Limits for Tensile Stress at Service
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Chapter 05 Chapter 05 Concrete StructuresConcrete Structures
y For concrete cover, the bridge code recommends the following Min cover to main bars > 25mm Cover to ties and stirrups may be 12mm less
than the ones specified on the table shown on the next slide.
Chapter 05 Chapter 05 Concrete StructuresConcrete Structures
y For concrete cover, the bridge code recommends the following.
SECTION HIGHLIGHTS SECTION HIGHLIGHTS CHAPTER 09: DECKS CHAPTER 09: DECKS AND DECK SYSTEMSAND DECK SYSTEMS
Design of Reinforced Concrete Bridges as per NSCP 2010 Vol 2
Chapter 09: Deck SlabsChapter 09: Deck Slabs
y For this chapter, only provisions for concrete deck slabs will be discussed.
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Chapter 09: Deck SlabsChapter 09: Deck Slabs
y Depth > 175mm unless specified by the bridge owneryWhen deck skew does not exceed 25o,
the transverse reinforcement may be parallel to the skew. Otherwise, it should be perpendicular.
Chapter 09: Deck SlabsChapter 09: Deck Slabs
y Skew less than 25o.
Chapter 09: Deck SlabsChapter 09: Deck Slabs
y Skew > 25o. Transverse reinforcement now perpendicular to longitudinal.
Skew Angle
Chapter 09: Deck SlabsChapter 09: Deck Slabs
y The reinforcement may be designed empirically as long as the following conditions are satisfied Supporting components are made of steel or
concrete The deck is fully cast-in-place and water cured The deck has a uniform depth
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Chapter 09: Deck SlabsChapter 09: Deck Slabs
y The reinforcement may be designed empirically as long as the following conditions are satisfied The ratio of effective length to design depth
does not exceed 18 and is not less than 6.0 Core depth of the slab is not less than
100mm
Chapter 09: Deck SlabsChapter 09: Deck Slabs
y The reinforcement may be designed empirically as long as the following conditions are satisfied Effective length (s effective) does not exceed
4100mm
Chapter 09: Deck SlabsChapter 09: Deck Slabs
y The reinforcement may be designed empirically as long as the following conditions are satisfied There is an overhang beyond the external
girder with a span of 5xSlabThickness. 28 day strength of the deck = 28 MPa Deck is composite with the deck
components. Minimum 4 layers of reinf.
Chapter 09: Deck SlabsChapter 09: Deck Slabs
y Minimum reinforcement as per empirical requirements 0.570mm2/mm for steel in bottom layer 0.380mm2/mm for steel in top layer
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Chapter 09: Deck SlabsChapter 09: Deck Slabs
y Traditional design It is still permitted to design the slabs as
conventional flexure elements. Distribution reinforcement is recommended
as follows
SECTION HIGHLIGHTS SECTION HIGHLIGHTS CHAPTER 11: CHAPTER 11: ABUTMENTS, PIERS AND ABUTMENTS, PIERS AND WALLSWALLS
Design of Reinforced Concrete Bridges as per NSCP 2010 Vol 2
Chapter 11: Abutments, Piers and Chapter 11: Abutments, Piers and WallsWallsy This chapter provides the provisions for
earth pressure forces for conventional and MSE-type retaining walls.
Chapter 11: Abutments, Piers and Chapter 11: Abutments, Piers and WallsWallsy This chapter also specifies the capacity of
typical soil nails into soil or concrete.
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Chapter 11: Abutments, Piers and Chapter 11: Abutments, Piers and WallsWallsy Typical checks for conventional retaining
walls are as follows Bearing Resistance Overturning Subsurface Erosion Passive Resistance Sliding
Chapter 11: Abutments, Piers and Chapter 11: Abutments, Piers and WallsWallsy Of particular importance in this chapter is
the appendix regarding Seismic Design of Abutments and Gravity Retaining Structuresy This appendix details the Mononobe Okabe
method for retaining walls.
Chapter 11: Abutments, Piers and Chapter 11: Abutments, Piers and WallsWallsy An illustration of the Mononobe-Okabe
loads for the active wedge
Chapter 11: Abutments, Piers and Chapter 11: Abutments, Piers and WallsWallsy Variables relevant with figure on the
previous slide
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Chapter 11: Abutments, Piers and Chapter 11: Abutments, Piers and WallsWallsy Important things to note from Appendix
of Chapter 11 For nonyielding abutments, it is recommended
to multiply the acceleration coefficient by 1.5
For seismic zone 4 it is recommended to have monolithic/integral abutments to minimize damage
Chapter 11: Abutments, Piers and Chapter 11: Abutments, Piers and WallsWallsy Example of Non-yielding abutments.
w/ Raked Piles w/ Soil Nails
SECTION HIGHLIGHTS SECTION HIGHLIGHTS CHAPTER 13: CHAPTER 13: RAILINGSRAILINGS
Design of Reinforced Concrete Bridges as per NSCP 2010 Vol 2
Chapter 13: RailingsChapter 13: Railings
y Railings are intended for two things To prevent wayward vehicles from going over
the bridge and protect adjacent property To protect pedestrians from wayward vehicles
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Chapter 13: RailingsChapter 13: Railings
y Railings are intended for the following To prevent wayward vehicles from going over
the bridge and protect adjacent property To protect pedestrians from wayward vehicles Protection of other vehicles near the
collission
Chapter 13: RailingsChapter 13: Railingsy Railings are intended to have different
levels of protection according to the use of the road. Test Level One (TL-1) Areas w/ low speed
and low traffic volume TL-2 Collector roads with favorable site
conditions w/ a small number of heavy vehicles TL-3 Generally acceptable for many high
speed arterial highways w/ favorable site conditions.
Chapter 13: RailingsChapter 13: Railingsy Railings are intended to have different
levels of protection according to the use of the road. TL-4 Generally acceptable for high speed
highways with a mixture of trucks and heavy vehicles TL-5 Similar to TL-4 but with unfavorable
site conditions (Ex: A wayward vehicle may collide with valuable property) TL-6 similar to TL-6 but traffic is expected
to have tanker type trucks
Chapter 13: RailingsChapter 13: Railings
y The height of railing has a requirement depending on the TL level.
TL Height (mm)
1 685
2 685
3 685
4 810
5 1070
6 2290
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Chapter 13: RailingsChapter 13: Railingsy Design forces prescribed for railings are
as follows
SECTION HIGHLIGHTS SECTION HIGHLIGHTS CHAPTER 14: JOINTS CHAPTER 14: JOINTS AND BEARINGSAND BEARINGS
Design of Reinforced Concrete Bridges as per NSCP 2010 Vol 2
Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y Though integral bridges are recommended by the latest bridge code, expansion joints are still needed for very long bridges
Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y Commonly used bearings for expansion joints are Elastomeric Bearing Pads made of rubber.y To add the capacity of Elastomeric
Bearing Pads, they are often reinforced with steel plates as shown below.
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Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y The following limits govern the design of Elastomeric Bearing Pads Shape Factor Allowable Compressive Stress and Deflection Allowable Shear (Lateral) Deformation Allowable Rotation Stability
Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y The following limits govern the design of Elastomeric Bearing Pads AASHTO 2007 recommends two methods
named Method A and Method B. For this presentation only excerpts from
Method B will be shown.
Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y The following limits govern the design of Elastomeric Bearing Pads Properties recommended for bearing pads are
shown below.
Shear Modulus G for each hardness
Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y The following limits govern the design of Elastomeric Bearing Pads Shape Factorx The shape factor is defined as the ratio of the area
to the side area free to bulge.x Looking at one sample below.
L
W
hriArea
Side Area Free to Bulge=
Note that this is done for each layer for reinforced bearing pads
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Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y The following limits govern the design of Elastomeric Bearing Pads Compressive stress (allowable values shown
below)
Vs = Service Stress due to total loadVL = Service stress due to live load
Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y The following limits govern the design of Elastomeric Bearing Pads Compressive deflection (Live load)
Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y The following limits govern the design of Elastomeric Bearing Pads Compressive deflection (Dead load)
Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y The following limits govern the design of Elastomeric Bearing Pads Compressive deflection (Strain)
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Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y The following limits govern the design of Elastomeric Bearing Pads Since stress is non-linear for
reinforced/laminated bearings, the following graphs can also be used to compute strain
Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y The following limits govern the design of Elastomeric Bearing Pads Allowable shear deformation limit
Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y The following limits govern the design of Elastomeric Bearing Pads Allowable Rotation for Combined
Compression and rotationx Uplift requirements are satisfied if
n = number of interior layers
Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y The following limits govern the design of Elastomeric Bearing Pads Allowable Rotation for Combined
Compression and rotationx Bearings subject to shear deformation shall satisfy
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Chapter 14: Joints and BearingsChapter 14: Joints and Bearings
y The following limits govern the design of Elastomeric Bearing Pads Stabilityx Bearings are considered stable if
Where
Design of Reinforced Concrete Design of Reinforced Concrete Bridges as per NSCP 2010 Bridges as per NSCP 2010 VolVol 22THE END! Thank you for listening
By Alden Paul D. Balili, MSCEDLSU-M