sr 1911-1998 steel bridges for railway (en)

8/12/2019 SR 1911-1998 Steel Bridges for Railway (en)

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ICS 93.040

SR 1911October 1998

ROMANIAN STANDARD Classification index G 61

Steel bridges for railwayDesign Rules

Poduri metalice de cale ferat!Prescrip"ii de proiectare

Ponts mtalliques pour chemin de fer

Prescriptions en vue de ltablissement des projets

APPROVAL Approved by the General Manager of IRS on the 14thof April 1997Supersedes STAS 1911 75

CORRESPONDENCE On the approval date of this standard, there is noInternational or European Standard dealing with the samesubject

La data aprob!rii prezentului standard, nu exist! nici unstandard interna"ional sau european care s! se refere laacela#i subiect

la date d`approbation de la prsente notme il n`existe pasde Norme internationale ou europ enne traitant du mmesujet

TIT DESCRIPTORS Bridge, railway metallic profile, design, design rules

ASOCIA!IA DE STANDARDIZARE DIN ROMNIA (ASRO),Adresa po#tal!: str. Mendeleev 21-25, 70168, Bucure#ti 1, Direc"ia General!: Tel.: +40 1 211.32.96; Fax: +40 1 210.08.33,

Direc"ia Standardizare: Tel. : +40 1 310.43.08; +40 1 310.43.09, Fax: +40 1 315.58.70,Direc"ia Publica"ii: Serv. Vnz!ri/Abonamente: Tel: +40 1 212.77.25, +40 1 212.79.20, +40 1 212.77.23, +40 1 312.94.88 ;

Fax : +40 1 210.25.14, +40 1 212.76.20

ASRO Entire or partial multiplication or use of this standard in any kind of publications and by any means (electronically,mechanically, photocopy, micromedia etc.) is strictly forbidden without a prior written consent of ASRO

Ref.: SR 1911:1998 6thedition


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1 GENERAL

1.1 Object and domain of application

1.1.1 The present standard refers to:

- the design of steel structures for new railway bridges, as well as elements of the metallicstructures of the combined bridges affected by the loading from the railway.- verification and consolidation of metallic structures of existing railway bridges.

1.1.2 The present standard does not apply to the design of the elements specifically for suspendedbridges, braces bridges or to other types of bridges with special composition.

1.1.3 The specifications from the present standard apply to all the metallic structures of the bridgeslocated on railway lines with a traffic speed of up to 160 km/h.

For railway lines with a traffic speed higher than 160 km/h supplementary regulations shall beestablished.

1.1.4 In the calculus there can be used also other methods than the ones established by the standard,with a supplementary verification character, if their results have been verified by testing and/or if theyhave been confirmed by the behaviour in exploitation of structures similar to the one being designed.

1.1.5 If, in order to complete or verify the calculus there is also necessary to be used testing a model,their program has to be established by mutual agreement between the designer, beneficiary and aspecialized research institute.

1.2 Reference standards

STAS 500/1 89 General use steels for constructions. Quality technical requirements

STAS 500/2 80 General use steels for constructions. Grades

STAS 794 90 Hot-rolled steel. Round steel for connection means. Dimensions

STAS 796 89 Rivets. General technical quality requirements

STAS 797 80 Steel rivets. Buttonhead rivets. Dimensions

STAS 802 80 Steel rivets. Round top countersunk rivet. Dimensions

STAS 880 88 Quality carbon steel for thermal treatment for machines construction.Grades and technical quality requirements

STAS 922 89 Six-angled bolt nuts. Execution class C

STAS 1257 80 Steel rivets. Small round top countersunk rivet. Dimensions

STAS 1489 78 Railway bridges. Actions

STAS 2242 80 Washers for U and I profiles. Dimensions

STAS 2700/3 89 Screw connection means. Mechanic means and testing methods forscrews and double-ended bolts

STAS 3165 80 Steel rivets. Countersunk rivet head. Dimensions

STAS 3220- 89 Railway bridges. Standard conveys


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STAS 3221 86 Road bridges. Standard coveys and loading classes

STAS 3461 83 Steel bridges for railway and roads. Riveted superstructures. Designrules

SR ISO 3755:1994 Non-alloyed steels cast for general use mechanic constructions

SR ISO 4016:1994 Six-angled screws partially screwed. Degree C

SR ISO 4018:1994 Six-angled screws completely screwed. Degree C

STAS 4031 77 Steel bridges for railway and roads. Abutments from cast steel.Technical and assembling conditions

STAS 4071 89 Six-angle bolt nuts. Execution class A and B

STAS 4272 89 Six-angle screws. Execution class A and B

STAS 4392 84 Normal railway. Gauges

STAS 4531 89 Narrow railway. Gauges

SR ISO 4759-3:1996 Tolerances for assembling elements. Third part: common washers forscrews and bolt nuts with the nominal diameter of the thread from1 mm up to 150 mm including. Grades A and C

STAS 5200/4 91 Common washers. Normal dimensions series. Execution class A

STAS 5200/5 91 Common washers. Large dimensions series. Execution class Aand C

STAS 5626 92 Bridges. Terminology

STAS 5930 89 Six-angled fitted bolts. Execution class

STAS 6726 85 Welded joints. Forms and dimensions of joints at steel welding under aflux layer

STAS R8542 79 Choosing the steels for metallic constructions

STAS 8796/1 80 High resistance assembling means used with prestressing at steelstructures joints. IP screws. Dimensions

STAS 8796/2 80 High resistance assembling means used with prestressing at steelstructures joints. IP bolt nuts. Dimensions

STAS 8796/3 89 High resistance assembling means used with prestressing at steel

structures joints. IP washers.

STAS 8796/4 89 High resistance assembling means used with prestressing at steelstructures joints. General technical quality conditions

STAS 8949 82 Steels intended for fabrication of assembling means by hot-plasticdistortion

STAS 9330 - 84 Bridges for railway and road. Joints with high resistance screws.Design and execution rules


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STAS 9407 75 Steel bridges for railway and road. Welded superstructures. Executionrules

STAS 10101/1 78 Actions in constructions. Technical weights and permanent loads

STAS 10101/OB 87 Actions in constructions. Classification and grouping of actions forbridges for railway and road

STAS 10564/1 81 Cutting with oxygen of metals. Quality classes of cuts

STAS 11417 86 Metal testing. Traction test on the thickness direction

STAS 12187 88 Steel thick plates for main elements of bridges and viaducts

SR EN 29692:1994 Welding with electric cushion with a coated electrode, welding withelectric cushion in protective gas environment and welding with gasesby melting. Preparation of pieces of steel jointing


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2 MATERIALS

2.1 Steels for construction elements

2.1.1 Steels for the elements of steel bridges are specified in table 1, and their characteristics intable 2.

Table 1

Table 2

2.1.2 Using of steels unspecified in table 1, can be done if these meet the conditions specified instandards for steels, regarding:- the chemical composition,- mechanical characteristics,

Element typeNo.crt.

Main resistanceelements

Secondaryresistanceelements

Abutments

Welded

Riveted

Welded

Riveted

Balancers

Rollers

Plates

Steel

Nomination

Rolled steel

Rolled steel

Cast carbonsteel

Carbon steel ofquality

Rolled steel

Quality Standard number

No.crt.

Steel grade andquality

Breakingstrength(N/mm2)

Standardnumber

Commoncharacteristics

Flowlimit

(N/mm2)

- longitudinal modulusof elasticity:

- transverse modulusof elasticity:

- coefficient oftransverse shrinkage

- coefficient of thermallinear dilatation

- specific weight:


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- welding behavior,established by testing.

2.1.3 There is allowed to use in the elaboration of the structure of the same bridge, as well as in thesame element, of steels of different grades and classes of quality

2.1.4 Choosing the steels grades is done considering the techno-economical characteristics, andchoosing the quality class and the deoxidization degree, is done in order to assure the elements againstthe danger of fragile breaking.

2.2 Steels for rivets, usual screws and high resistance screws.

2.2.1 The characteristics of steels for rivets, usual screws and high resistance screws have to meet thespecifications from table 3.

Table 3

2.2.2 The use for rivets, common screws and high resistance screws of steels with other characteristicsthan the one specified in table 3 can be done under the conditions specified in 2.1.2

3 ACTIONS. ACTIONS GROUPING. LOADS REPARTITION

3.1 The actions are considered according to STAS 1489 and STAS 3220.

3.2 Actions grouping is done according to STAS 10101/OB.

Joint type

Rivetedjoints

Joints withusual screws

Joints withprestressedhighresistancescrews

Connection means

Standard numberNomination GradeMechanical

characteristicStandardnumber

Grade of steelfrom the

elements thatare being

assembled

Material

Rivets

Screws

Bolt nuts

Washers

IPScrews

IP Boltnuts

IP Washers

Group

Group

Group

Group

Group

Hardness

*) In order to rivet the elements from OL52 there can be used rivets made from OL44 steel bars having the following

chemical composition: C = (0.100.18)%; Si = (0.250.50)%; Mn = (0.600.80)%; P = maximum 0.05%;S = maximum 0.05%; and the following mechanic characteristics; !r = (440520) N/mm2; "5 #27%;

$r= (360480) N/mm2; specific slump coefficient = 3 : 1.


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3.3 The present standard uses the method of permitted strength. The actions coefficients (na) andgrouping coefficients (ng) from STAS 10101/OB is considered with the maximum value, 1.

3.4 The loads repartition is done according to 3.4.1 and .3.4.2.

3.4.1 The repartition of own weight (of the resistance structure) is considered to be the real one. Forspans under 100 m the loading, from its own weight, can be considered uniformly distributed.

3.4.2 In order to design the elements of the path, the longitudinal runners or the flooring is permittedthat the repartition of the point loads from standard convoys to be according to 3.4.2.1; 3.4.2.2.

3.4.2.1 The load on the wheel can be distributed to three rail supporting points as illustrated in figure 1.

Figure 1

3.4.2.2 The ballast repartition, in the longitudinal sense of the path, of loads which correspond to the

traverses are generally considered uniformly distributed. For the elements of the planks flooring whichundertake directly the path loads the repartition can be considered as showed in figure 2, if it isunfavourable.

Figure 2

3.4.2.3 The ballast repartition, in a transverse sense of the path, of vertical and horizontal forces isconsidered according to figure 3 a, b, c where :

Ph Horizontal forcePv Vertical forcePr Resulting forceh Distance from the weight center of the convoy to the plane tangent the rails crown which is

considered: 2.0 m for normal railway; 1.50 m for tight railways Causeway superelevatione Eccentricity of application of the resulting force at the level of the upper flooring face which

sustains the ballast.

P load on wheela distance between two consecutive

rail supporting points,

Load on traverse

Upper face of the blading whichsustains the ballast


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Figure 3

Upper flooring face whichsustains the ballast




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3.5 The eccentricity of the vertical loads from the railway vehicles convoys is considered by the axleswheel loads ratio 1.25:1.00. The resulting eccentricity is showed in figure 4.

Figure 4

3.6 In the calculus of the elements of the steel bridges structure it is considered the effect ofoffsetting with 5.0 cm from the path axis of the (in plan) regarding to its initial position specified in theproject.

4 DYNAMIC COEFFICIENT

4.1 The dynamic coefficient !with which the load rendered by standard type vehicles convoys aremultiplied, is considered according to STAS 1489.

4.2 The dynamic coefficient is taken into consideration in:

- calculus of all the elements which are part of the supporting structure, including the abutments,- calculus of metallic piers elements,- calculus of pressure from under the bearings,- verification of the ascension from the abutment (negative reactions) of the deck.

5 CALCULUS OF EFFORTS AN DEFORMATIONS

5.1 Calculus principles

5.1.1 In the resistance calculus, for elastic stability and position stability, are taken into considerationthe most unfavourable groups and positions of the actions, considering their compatibility ofsimoultaneous apparition. The efforts, which are produced simoultaneously in the sections of the

elements, are all determined for the same position of the load and actions.5.1.2 The calculus of efforts and deformations in the structural elements of a steel bridge is done in thefollowing steps:- the elements are considered as part from plane static systems, distinct (with no cooperation), in the

structure dimensioning stage;- the elements are considered as part of a spatial static system, in the structure verification stage.

In this case, the calculus can be done as follows:

a) by decomposing the spatial static system in plane static systems stressed by the actions with a effectdeterminant in dimensioning the component elements. It is always considered the mutual influence(cooperation) between the plane static systems where the spatial structure was decomposed,realizing the superposition of the effects.

b) by considering a spatial calculus model which reflects as accurate as possible the real compositionand behaviour of the structure.

P1, P2= Loads on wheels

P0= P1+ P2= Load on axis

= track gauge


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5.1.2.1 For the steel bridge structures with spans %$50 m which have the path sustained on a network ofbeams (stringers and struts) the effect of cooperation can be neglected if there does not exist anyconnection between the beams of the path and the main bracing except of the ties realized by the brakingtaking over and transmitting device located near the middle of the span. In this case there are alsoobserved the specifications from 5.3.1.3 and 5.6.3 from the present standard.

5.1.2.2 Under all the structure composition situations different from the one specified at 5.1.2.1, thecalculus of the efforts and deformations is done according to 5.1.2.

5.1.2.3 The braking taking over and transmission devices can be realized from rods, washers, struts withhigh at horizontal bending rigidity etc.

5.13 The calculus of the efforts and deformations in the elements of the structure is done based onactions and loads specified in STAS 1489, bearing in mind the grouping of the actions specified inSTAS 10101/OB.

5.1.4 In the realization of the model for the structure calculus there is to be considered the real modalityof elements jointing. In the situation where there exists uncertainties regarding the modality of functioningof the joint, shall be chosen the model which leads to the most unfavorable effects for the action to beverified.

5.1.5 If for the calculus are used computer assisted structural analysis programs there shall beindicated in all cases the name of the program, a relevant description and of its performances from whichto result also the hypothesis that it takes into consideration.

5.1.6 The main results obtained by the help of the computer are presented as tables and graphicalrepresentations for each loading case considered. It is compulsory to verify its result scale by a manualcalculus which is to be included in the notes of calculus, justifying the differences obtained by the twomethods.

As a general rule, there is to be avoided the inclusion in the calculus notes of tables with figures, printedfrom the computer. If they contain indispensable values for the verification done, they shall be annexed tothe notes of calculus and shall be clearly defined (nomination, loading cases, units, etc.).

5.1.7 The calculus methods shall contain:- technical regulations on which the design of the structure is based;- plans of the structure from which to result the composition and structure dimensions and of

constitutional elements;- considered actions and their grouping;- the characteristics of the metallic material from the constitutional elements;- calculus models used, hypothesis and simplifications in the structure analysis; their argumentation;- texts and formulas (literally and digitally) which describe the verifications performed.

5.2 Calculus of the stringers

5.2.1 For the stringers dimensioning stage is performed a simplified calculus. In this case the bendingmoments are taken from table 4.

Table 4

In table 4, M0 is the maximum bending moment in the field, for the stringer considered as independent

beam, simply supported with the span equal to the distance between the strut axles.

No.crt.

Moment designation

Moments in final fields of thestringers row

Moments in the intermediary fields

Negative moments on abutment

The value of the moment for


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In case of stringers with different spans, in the evaluation of the negative moment from the sharedsupport, the arithmetic mean for M0of the corresponding maximum moments of the two nearby opening isconsidered.

5.2.2 The verification of the stringers is performed based on efforts determined considering the spatialmodel of structural analysis, according to 5.1.2.

5.2.3 The direct effect of the transverse actions (meandering, wind, centrifugal force) can be estimatedaccording to 5.2.3.1 up to 5.2.3.3.

5.2.3.1 The maximum bending moment Mwh produced by the direct action of the wind on the convoy, pathand stringers, in the stringers from the middle of their bracing panel, can be assessed with:

1Mwh = 20

w.a2

wherew The loading per meter which corresponds to a stringer from the direct action of the

wind on the convoy, path and stringers;a Span of the bracing panel of the stringers.

5.2.3.2 The maximum bending moment Mshproduced by the direct meandering action in a stringers canbe assessed with:

Msh= 0.25 Mos

whereMos The bending moment produced by the meandering force S, entirely, acting over

the upper flange of the stringer, considered as simple supported on the span of astringers bracing panel

5.2.3.3 The maximum bending moment Msh produced by the direct action of the centrifugal force in astringer can be assessed with:

MFch= 0.25 MoFc

whereMoFc The bending moment produced by the direct wind action, considering the simple

supported stringer, with the span equal to the length of a stringers bracing panel

5.2.4 The resulting moment from the direct action of the wind and of the meandering is undertaken onlyby the following elements of the upper flange of the stringer:- metal strips (ribbon iron) and horizontal legs of angle sections, for riveted stringers- metal strips (ribbon iron) for welded stringers

5.2.5 In thestringers calculus can be neglected the efforts coming from:- indirect wind action;- indirect meandering action.

There can be also neglected the axial efforts produced in the stringers by the direct action of the wind,meandering and braking.

5.2.6 For the dimensioning stage, the fasteners for stringers are established according to 5.2.6.1 and5.2.6.2.

5.2.6.1 The upper continuity plate of the stringers is calculated with a tension stress Hpwith the relation:

MrHp = h

(1)

(2)

(3)

(4)


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whereMr The maximum negative moment from the support;h The lever arm, which is taken:

- at stringers without a seat, the distance from the center of gravity of the plate up tothe inferior edge of the stringer;

- at stringers with a seat, the distance from the center of gravity of the plate, with the

condition that its joint to the base of the stringer to be able to undertake the slippingbetween the stringer and the seat.

5.2.6.2 When the stringers are equipped with two continuity plates, the lever arm is equal to the distancebetween the center of gravity of the two plates.

R = 1.2 (Rg+ %Rp)

whereR Calculated reaction of the stringers;Rg Reaction from permanent loads, considering that the stringers are independent beams

simple supported;

Rp Maximum reaction from the convoy, considering that the stringers are independentbeams simple supported;% Dynamic coefficient.

5.2.7 Verification of the fastening elements of the stringers is performed based on the effortsdetermined considering the spatial structural analysis model, according to 5.1.2.

5.3 Struts calculus

5.3.1 In the dimensioning stage is permitted the simplified calculus of the struts according to 5.3.1.1 upto 5.3.1.5.

5.3.1.1 The simplified calculus of the struts is performed considering that they are beams simplysupported, having the span equal with the distance between the axis of the main beams. In the strutswhich are a part of the frames, there are also considered the efforts corresponding as frame elements.

5.3.1.2 For struts being a part of the decks which are not equipped with special devices in order toassure the cooperation, the simplified calculus is performed considering at loads, the reactions of thestringers, admitting that they are beams simply supported and independent.

5.3.1.3 Under the conditions from 5.3.1.2. the bending moments regarding the vertical axis of the struts,coming from the deformation of the flanges of the main beams, are not considered if the strut which isbeing calculated is at a distance equal to or lesser than 30 m from the braking overtaking andtransmission device and if it has the flanges narrower than 260 mm. Other wise, there are alsoconsidered these moments, increasing the admissible strength resistance with 10%.

5.3.1.4 The struts jointed to the main beams by welding are considered, if an exact calculus lacks,

stressed at the end by a negative moment (Msa) given by the relation:

1Msa = 4

Mo

whereMo Is the maximum field moment of the strut considered as simply supported beam.

5.3.1.5 The joint of the struts to the main beams is calculated, whether or not they are equipped withdevices that ensure the cooperation between the elements of the superstructure, at the calculatedreaction R, given by the relation:

R = 1.2 (Rg+ %Rp)

(5)

(6)

(7)


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whereRg Reaction of the strut from permanent load;Rp Maximum reaction from convoy load;% Dynamic coefficient corresponding to the strut span

5.3.2 The verification of the strut is performed based on the efforts determined considering the spatialstructural analysis model, according to 5.1.2.

5.3.3 The struts with a low path, top side opened, have to realize the rigidity corresponding for thepartial frames, which must to ensure the general stability of the compressed flanges of the main beams.The calculus is performed according to 8.4.5.6.

5.3.4 The verification of the fastening elements of the struts is performed based on the effortsdetermined considering the spatial structural analysis model, according to 5.1.2.

5.4 Calculus of the main solid web girders

5.4.1 The theoretical section variation points of the solid web girders are established such as the

envelope curve of the bending moments to be covered by the diagram of the capable moments (Mcap) ofthe section.

These points are established analytically or graphically. In case of the independent beams simplysupported, they can be established by the relation:

wherex Distance from the support to the theoretical point of interruption;M Beam span;Mx The lowest resistance modulus of the beam section, rightly in the section

variation point:Mmax The highest resistance modulus of the considered beam section.

5.4.1.1 The riveted plates have to exceed the theoretical point established according to 5.4.1 with at leasttwo rivet pairs (figure 5) from which a pair can be placed in the theoretical point.

The rivets between the extremities of two consecutive plates have to ensure the total stressing of theplate that they fasten.

Figure 5

Theoretic oint


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5.4.1.2 The welded ribbon iron can be interrupted in the theoretical point, considering also the frontalcorner weld (figure 6). The lateral and frontal welds from the extremity of a plate and up to the theoreticalpoint of interruption of the next plate have to provide the stressing of the plate which it fastens.

Figure 6

5.5 Calculus of the main trussed beams

5.5.1 For the dimensioning stage is permitted the efforts determination in the bars of the trussed beamsin the hypothesis that they are hinged in the joints.

5.5.2 In the hypothesis of the hinged joints admitted at 5.5.1 the effect of the joints rigidity considered inthe calculus by increasing the axial tension with the coefficient:

lp= 1.25 0.01

e #1.05

wherel The theoretical length of a rode The distance in the beam plan between the center of gravity of the rod section and its

extreme fiber (figure 7)

l10 Lr, there will be proceeded as for a bridge in full curve,with the radius R.

5.7.4.7The determination of the efforts in a plank section located in the transition curve, is performed

based on the value of the centrifugal force established approximately, considering the bridge in circularcurve with the radius px, given by the relation:

(24)

where

x the distance from AR to the considered section, measured on the curve tangent in AR.

6 SECTIONS CALCULUS CHARACTERISTICS

6.1 Elements jointed with rivets or screws

6.1.1 The sections calculus characteristics of the elements jointed with rivets and screws, dependingon the nature of the effort, are the one from table 6.

6.1.2 The attenuation produced by the rivet holes ('A; 'I) in the tensioned pieces are taken inconsideration (figure 12) after the normal line (for example line I-II) or after the sinuous line (for exampleline II-III), as which is more unfavorable. For angles, I or U profiles, the line of braking sinuous isestablished by folding of the wings (planks) according to figure 13.

Figure 11


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Figure 12 Figure 13

Table 6

NOTE - If the symbols from the table are followed by the symbol z or y the value that they represent has to beconsidered regarding the main inertia axis z-z, respectively y-y of the section.

No.crt. Effort Unit stress

Axial effort

Shearingforce

Bending

Free torsion

Constrainedtorsion

The tension

Compression

Slipping

Tangential unitstress

Tension fromthe bending

Compression frombending

Tangential unitstress from torsion

Compression ortension

Sliding

Net area

Calculus section characteristics

Designation Relation of calculus

Gross area

Gross area

The static moment of the section whichslips in rapport with the neuter axis

The inertia moment of the grosssection

The inertia moment of the section for thecalculus of the tensile

The modulus of resistance for tension

The inertia moment of the grosssection

The modulus of resistance forcompression

The free torsion constant

Sectorial area

Sectorial inertia

Static sectorial moment

Symbol

1) For joints with high resistance screws, the in the unit stress established sections are calculated according to STAS 9330.

2) 'A the attenuation area of the section according to 6.1.2 and 6.1.3.3) is considered the gross section of the part which slips.4) 'l the inertia of the sliding section about the neutral axis the sum of the inertia moments of the attenuations from the tensioned area about the

neutral axis (considered for the gross section) .5) Yt the distance from the most tensioned fiber the neutral axis (considered for the gross section).6) Yc the distance from the most compressed fiber to the neutral axis (considered for the gross section).7) hi the width of a washer of the element section (for example: the width of the flange, the height of the solid web of a double T section etc.);

ti the thickness of a washer;a digital coefficient which depends on the shape of the section and which is taken:1.30 for double T, U and boxed profiles with sections:1.15 for sections T and Z;1.00 for angle sectionFor sections composed by riveting or welding h iand tiare taken for each shading rectangle distinctly according to figure 11.

8) ds element of length infinitely small of the median fiber of the washers from which the section is composed;p the distance from the center of rolling-bending, to the direction determined by the indefinite prolongation of the element ds.

9) dA = &.ds infinite area small element of the section; & the thickness of the element ds.w the sectorial area corresponding to the point from the median fiber of the section in which there was considered the element ds, of theelementary dA area.

10) wand dA have the same meaning as in the relation from the point 9 (previously)


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6.1.3 The net aria (An) of the tensional elements, composed by several pieces, fastened by rivets orscrews, is equal to the sum of the areas of all the pieces that compose the section of the element.

For each piece is considered the net aria, either the normal section, or the sinuous section, as it is mostunfavorable, according to the figure 14.

Figure 14

6.2 Elements jointed by welding

6.2.1 The calculus characteristics of the sections assembled only by welding, non-weakened by rivet orscrew wholes are established based on the gross sections.

6.2.2 The welding belts calculus characteristics are:

- the calculus thickness (a);- the calculus length (l)- the calculus section (As)

- the inertia moment (ls)

6.2.2.1 The calculus thickness (a)The calculus thickness of a welding belt is determined according to table 7.

6.2.2.2 The calculus length (l)

6.2.2.2.1The calculus length of a welding belt is considered, usually, equal to the effective length of thebelt, from which are extracted the terminal craters, each terminal crater being considered of equal lengthas the calculus thickness a of the belt.

If at the butt-jointed welds are used technological pieces, according to figure 15, the calculus length ofthe belt is taken equal to the entire length of the belt.

At welds in K, in Y, or corner, where are used technological pieces or where the belts are tuned back(figure 16) the terminal craters are not extracted.


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if Table 7

No.crt. Seams

Butt-jointed seams

In K, welded on bothsides

In Y

In K, without completepenetration

In Y with cornerseam in the oppositepart

In Y on a single side

Corner seam on a singleside

Corner seam on both

sides

Corner seam on asingle side

Corner seam on bothsides, with deeppenetration

With deep penetration. Semi-automatewelding under layer of flux, in CO2or withelectrodes with deep penetration. In theseam, a represents the height of theisosceles triangle contained, measured asin no. crt. 8 and a represents the calculusthickness.

In seam, a represents the height of theisosceles triangle contained in the seam,measured up to the theoretical point ofthe root

Non-penetration in area c, in which

Welding on a single side, with the rootcompletely, penetrated

Complete penetration by chamfering andre-welding the root on the opposite side

Complete penetration by welding on bothsides

The root of the seam completelypenetrated, or chamfered and re-welded

The scheme of theseam

Welding conditions The calculus thicknessof belt a

If these conditions are not fulfilled, thecalculus thickness (a) is taken accordingto No. crt. 8 11 from this table

and

if

if

In which eminisdetermined byexperimental testing. Itthe welding under layerof flux the depth ofpenetration can beconsidered 0.4a, and the

calculus thickness:a = 1.2a


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Figure 15

Figure 16

6.2.2.2.2When jointing superposed pieces (figure 17) the calculus length of each lateral corner seam,must to fulfill the condition:

15 a %/ %60 a

Figure 17

6.2.2.2.3The calculus length of the seams which joint the solid webs of the composed rods to the flanges(for example in double T sections or boxed) jointed at knobs by rivets, screws or welding, is takenas much equal to the distance measured from the beginning of the rod to knob joint


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up to the end of the seam which joints the webs to the flanges: for example in case of jointing with rivetsor screws, in figure 18 from the first rivet or screw up to the end of the seam between the web andflanges. Along this length all the seams which joint the webs to the flanges have to transmit to these theentire effort.

Figure 18

6.2.2.3The calculus section (As)

6.2.2.3.1The calculus section of a welded joint is considered according to the relation:

(26)

In the sum above, by the nature of the effort which is being transmitted, are comprised the followingseams:- for the transmission of the axial effort, all the seams from the jointed plane;- for the transmission of the shearing force, are considered only the seams whose longitudinal axis isparallel to the shearing force (for example, at the jointing of the section according to figure 19 for the

transmission of the shearing force Tyare generally considered only the seams which joint the web of theprofile, and for the transmission of the shearing force Tz, only the seams that joint the flanges).

6.2.2.3.2 The calculus section of a joint stressed by axial effort having butt-jointed seams as well ascorner (figure 20) are determined by the relation:

As= Asc+ ($Asa (27)

Figure 19


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Figure 20

where:

Asc the cross area of the corner seams;Asa The cross area of the butt-jointed seams;($ A coefficient which considers the different permitted strengths, of the two

types of seams and which has the values:($= 0.6 for Asc/ Asa%1.50($= 0.4 for Asc/ Asa%$2.00

(28)(29)

For intermediary values of the Asc/ Asa ratio, the ($value is obtained by linear interpolation

6.2.2.3.3The calculus section of the corner seams is considered:- either in the bisector plan of the dihedral formed by the two sides of the seam, which passes through

its root, according to figure 21;

- or swinging on one of the planes formed by the sides of the pieces that are being welded, accordingto figure 22.

6.2.2.4The inertia moment (ls)

The inertia moment lsof the corner joint is considered equal to the sum of the inertia moments of thesurface of each seam, regarding to the center of gravity Gsof all the seams.


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Figure 21

Figure 22

For the calculus of the center of gravity and of the inertia moment of the seams, is permitted that thecenter of gravity of each seam is located rightly near its root at half the length.

At the calculus of the inertia moment of a joint which transmits a bending or torsion moment, areconsidered only the seams which, by their position fully contribute to the transmission of the bending ortorsion moment. For example, in figure 19, for the transmission of the bending moment can be consideredonly the seams that joint the flanges.


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7 PERMITTED RESISTANCE

7.1 The permitted resistances for the hot-rolled products which compose the elements of the bridgesstructures are indicated in table 8.

Table 8

7.1.1 Permitted resistances for the hot-rolled products from other steels than the ones from table 8 willbe determined by dividing their yield strength !c to the safety coefficients from table 9. There shall beobserved the specifications from 2.1.2.

Table 9

7.1.2 Permitted resistances of the steels used in abutment means are given by the table 10.

Table 10

No.crt.

The unitstress from

variousstresses

Symbol

Tensioncompression,bending

Shearing

The equivalentunit stress(formula 37)

Trans-formationcoefficientregarding

Qualityclass

Permitted resistances in N/mm of the hot-rolled sheets and profilesbrand:

Actions grouping

1.0

et

et

et

Grouping on actions

1.50

1.35

1.20

1.33

1.25

1.18c1 safety coefficient for normal tangential unit stresses orc2 safety coefficient for equivalent unit stresses (of comparison)

No.crt. Grade of the steel Unit stress

Permitted resistances of the steels usedin the abutment means

Actions grouping

Pressure on the contact line, in N/mm

Tension, compression, bending, in N/mm

Shearing, in N/mm

Equivalent unit stress, in N/mm



*) only for quality classes 3 and 4


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7.2 Permitted resistances for rivets, fitted screws and gross screws are given in table 7

Table 7

7.3 Permitted resistances of the welded seams are indicated in table 12

No.

crt.Fastening

mean

Rivets *)

Screws

Fittedscrews *)

Joint characteristic data

Rivets from OL 34 in OL 37elements

Rivets from OL 44 in OL 52elements

Mechaniccharacteristicsgroup accordingto STAS 2700/3

Unit stress from

various stresses Symbol

Permitted resistances of the steelsused in the abutment means

N/mm2

Actions grouping

Shearing

Pressure on rod

Tension in rod **)

Shearing

Pressure on rod

Tension in rod **)

ShearingPressure on rod

Tension in rod **)

Shearing

Pressure on rod

Tension in rod **)

Shearing

Pressure on rod

Tension in rod **)

$a

!la

!ta

$a

!la

!ta

$a

$a

$a

!la

!la

!la

!ta

!ta

!ta*) Fitting rivets and screws, stressed simultaneously by shearing and tension in the rod, are checked also for equivalent unit stress

according to 8.2.3.6.**) Stressing the rivets by tension in the rod is permitted only in special cases


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Table 12

Typeof

the

welded

seam

Designation

No.crt.From

table7

-

Butt-jointe

dwithcomplete

penetrationbyweldingon

bothsides

orwith

re-welding

oftheroot

-

InKwithc

omplete

penetration,byre-welding

theroot;

Thedirectionoftheunitstresses

regardingt

othelongitudinalaxisof

theseam

Thequality

classoftheseam

Thesymbo

lofthepermitted

resistance

Thepermitted

resistances

in

N/mm

2,inthe

weldedsea

ms

intheelem

ents

fromgrade

steels

Allqualityclasses

Compressionandsimpletension

orfrombending

Normalunitstre

sses!)$p

erpendiculartothelongitudinald

irectionoftheseam

InKwithoutcomp

lete

penetration

InVweldedon

bothsides

withoutcomplete

penetration.

Themaximumde

pthofnon-

penetration

c%

$1/5t,

c%

$3mm

Simple

compression

and

compressionby

bending

Simp

letension

andtensionfrom

bend

ing

-

InVweldedona

singlesidewithnon-

penetrationona

depthc%

$1/5t1or

c%

$3mm

-

Ofcornerweldedon

asinglesideoron

bothsides

Simplecompressionand

tensionorfrombending

Alltypesofseams

C

ompression

a

ndsimple

t

ensionorfrom

b

ending

N

ormalunit

s

tressalongthe

a

xis(!ll)

Allquality

classes

Allqualityclasses

Allqualityclasses

Allquality

classes

Slippingor

shearing

Tangentialunit

stressIIor)to

thelongitudinal

axisofthe

seam(

$ll$))

Butt-jointedin

Kand

Vwith

comple

te

penetra

tion

InKandV

without

complete

penetration

andofcorner

Mainunit

stress!1

2)

Equivalentunit

stress!ech

1)

Mainunit

stress!1

Equivalentunit

stress!ech

Allquality

classes

Allquality

classes

Allquality

classes

Unitstressintheseam


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7.3.1 The permitted resistances of the welded seams depend on:- the steel grade (according to table 12);- the nature of the unit stress (!$or $);- the sign of the normal unit stress (+ for tension and for compression);- the direction of the unit stress regarding to the longitudinal axis (!); !ll;$$);$ll).

7.3.2 The quality classes of the welded seams used in the desks of the railway steel bridges are:- IA; IIA; IIIA for butt-jointed seams and of corner in K and Y with complete penetration;- IB; IIB; IIIB for other seams.The execution conditions, of quality check, deviations and flaws allowed in execution, for each qualityclass are specified in STAS 9407.

7.3.3 The quality class of the welded seams is established during the design depending on thefollowing parameters:- the importance of the element in the structure- the importance of the welded seam within the element;- the nature of the unit stresses (alternative, pulsating tension, pulsating compression).

For example

1) for the resistance welded seams (for flanges webs, sheets of the beams or boxed rods) of the resistance mainelements (main beams, stringers, struts) and stressed by alternative or pulsating tension unit stresses is chosenthe with first class of quality.

2) for the seams and elements specified in chapter 1 but stressed by pulsating compressive unit stresses thesecond quality class can be chosen.

3) - the fastening welded seams of the main resistance elements or of secondary elements jointing (stiffeners,connecting link on sim, plates to joint the traverses, diaphragms, etc.) are specified with the second quality class.

4) the welded seams that joint the gusset plates of the bracings or the transverse frames of the main resistanceelements (flanges, walls or beam webs) are specified with the first quality class if the elements from which arejointed are stressed by alternate unit stresses or pulsating tension and second quality class if the elements fromwhich are jointed stressed by pulsating compressive unit stresses.

5) third quality class of the welded seams is used only for the elements of sidewalks and fences for the OL 52elements is not permitted the third quality class.

7.3.4 The quality classes of the welded seams have to be designated in the blueprints and observed inexecution in the factory or on site according to specifications from STAS 9407.

7.4 Permitted tolerances of the unit stresses and maximum unit stresses permitted for the elementsand joints subjected fatigue.

7.4.1 Permitted tolerance of the unit stresses ('!Ra, '$Ra) and the maximum permitted unit stresses(!Ra, $Ra) for elements and joints subjected to fatigue, are specified in table 14 17 and depend on:- the value and the sign of the asymmetry coefficient of the stress cycle (R!; R$);- the nature of the unit stress (!$or $);- the geometry of the element or the joint characterized by the type of notching (only for '!Ra, $Ra);- the grade of the steel (only for the types of notches H, I, J);- the maximum unit stress; (+) for tension and (-) for compression (only for the types of notches H, I, J and only for

'!Ra, $Ra)The asymmetry coefficients of the stressing cycles are defined by the relation:

(30)

(31)


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where!g ; $g Normal unit stresses, respectively tangential from permanent actions;* According to 8.3.6;% Dynamic coefficient, observing the specifications from chapter 4;!$min, T8.5 ;$$min, T8.5 Normal unit stresses, respectively minimum stresses from the action of the T8.5

convoy (2.1.2 from STAS 3220);

!$max, T8.5 ;$$max, T8.5 Normal unit stresses, respectively maximum stresses from the action of the T8.5convoy (2.1.2 from STAS 3220);

7.4.2 For elements of the steel railway bridges structures and their joints, stressed by unit stresses !,the constructive details are included in 10 groups of notching, noted from A to J, according to table 13.

Table 13

NOTE - By smooth surface is understood that the polished surface will have the same rugosity as the one specifiedfor the surface of the used laminated.

Group ofnotching

Representation The description of the element or the jointure

Elements with butt welding, transverse to the acting direction of thestress. The welding is: with back sealing run; polished in the direction

of action of the force, down to the level of the sheet surface; withsmooth surface without notches.The quality class of the welding IA, checked by radiography;

Jump welded junctures, in K or V, continuous for the jointing of thewebs to the bases; jump welded junctures, continuous for the jointing ofthe flange sheets between them; elements with butt welded,longitudinal junctures, with back sealing run. The quality class of thewelding II.

The elements with butt welding, transverse to the direction of theaction of the effort, with back sealing run.The quality class of the welding is IA.

Elements with different sheet thickness jointed transverse to thedirection of the stress action, butt welded, with back sealing run. Thequality class of the welding is IA. Polished in the direction of stressaction, with surface smooth without notches. See figure 76.

Jump welded junctures, continuous, in K or V, fully penetrated,which crosses a butt welded juncture.


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Table 13(continuation)

Group ofnotching


Elements on whose edge, parallel to the direction of stress action , arewelded gusset plates with filled corners at ends with radiusr > 150 mm. The welding of the gusset plates at ends is workedaccording to figure 97.

Elements on which are continuous filler welded, with jump welding,the ends of the sheets which are interrupted. The execution of the

continuous fillet welding according to figure 6.

Jump welded elements, in K or V, fully penetrated, transverse to thedirection of stress action whent > 15 mm.

Elements jointed with off cuts to avoid the intersection of the jumpwelding, in K or V with jump welded junctures, with back sealingrun.

Continuous elements with stiffening diaphragms transverse to thedirection of stress action jump welded with fillet welding, in K or V.The diaphragms can have chamfered corners and continuous weldingoverlapped at ends or with out chamfering; continuous filler welded.

Jump welded elements, in K or V, fully penetrated, with back sealingrun and stressed by bending, with or without shearing force.

Elements cross-jointed with welding in K or V, fully penetrated, withback sealing run, transverse to the direction of stress action.

Elements with jump welded junctures, in K or V, fully penetrated,

transverse to the direction of stress action when t%15 mm.


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Butt welded junctures executed on metallic support plates, transverseto the direction of the stress action. The quality class of the welding isII.

Elements on which are welded pieces of small length (l%100 mm) byjump welding, in K or V, longitudinal to the direction of the stressaction, all along the piece contour.

Elements on which mandrels are welded.

Elements on whose edge, parallel to the direction of the stress action,are welded gusset plates with filleted corners at ands with radius50 mm %r %150 mm. The welding of the gusset plate at ends is workedaccording to figure 97.

Cross-jointed elements with jump welding, transverse to the direction ofstress action.

Elements jointed with jump welding on bath sides stressed by bendingwith or without shearing force.

Elements on whose edge, parallel to the direction of stress action, arewelded gusset plates without filleted corners (the intersection with theelement on a right angle). The welding of the gusset plate can be jumpwelding, in K or in V.

Non-driller elements, stressed by tension or bending. The cutting of thesheet by the cutting torch, having the quality class of the cut accordingto STAS 10564/1.

Group ofnotching



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Group ofnotching


Drilled elements, stressed by tension or bending.

Riveted joints or with prestressed screws stressed by tension orbending


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Table 14

NOTE1 The intermediate values are linear interpolated2 For jump welding, the admissible tolerances for the tangential unit stresses ('$Ra) are reduced by0.6 times.

Translation NOTE all the values written with a coma (e.g.: -1,0 ...) in this table are to be read with a dot (e.g.: -1.0...)

Grade of steel

Notching

group

OL 37 and OL 52


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Table 15

NOTE - For intermediate values of the asymmetry coefficients are linear interpolated.


Grade of steel

Notchinggroup

Sign of themaximum unit

stress


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Table 16



Grade of steel

Notchinggroup

OL 37 and OL 52


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Table 17



Grade of steel

Notchinggroup

Sign of themaximum unit

stress


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7.4.3 The permitted tolerances of the unit stress ('!Ra, '$Ra), for the fatigue check of the elements andjointures which are part of the notching groups H, I, J are indicated in table 15.

7.4.4 The permitted deviation in shearing, '$Ra and in contact pressure on rod '!Ra, for the fatiguecheck of the rivets and fitted screws, are indicated in table 18.

7.4.5 The maximum permitted unit stresses, for the fatigue check of the welded joints, are indicated intable 16.

7.4.6 The maximum permitted unit stresses, for the fatigue check of the elements and joints comprisedin notching groups H, I, J are indicated in table 17.

7.4.7 The maximum permitted unit shearing stresses of $Ra and contact pressure on rod !Rla for thefatigue check of the fitting screws and rivets, are indicated in table 19.

8 VERIFICATIONS

8.1 The elements of steel railway bridges and their structure are checked for: resistance, accordingto 8.2, fatigue, according to 8.3, stability, according to 8.4, elastic strains, according to 8.5 and positionalstability, according to 8.6.

8.2 Resistance verifications

8.2.1 Resistance verifications are performed separately for the three actions group from chapter 3.From the calculus must result that the maximum unit stresses do not exceed the accept strength from 7.1up to 7.3.

8.2.2 Resistance verifications of the elements

8.2.2.1 The unit stresses in elements are calculated by the relations:

(32)

(33)

where:

N Axial stress in the element;My;Mz The bending moment regarding the main axis of inertia y-y, respectively z-z;Bw Bi-moment of bending-torsion;Ty;Tz The shearing force from the section parallel to axis y-y, respectively z-z;


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Table 18



Rivets from OL 34 or fitted screws from thegroup of mechanic characteristics 4.6, in

OL 37 elements

Rivets from OL 44 or fitted screws from thegroup of mechanic characteristics 5.6, in

OL 52 elements


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Table 19



Rivets from OL 34 or with fitted screws fromthe group of mechanic characteristics 4.6, in

OL 37 elements

Rivets from OL 44 or with fitted screws fromthe group of mechanic characteristics 5.6, in

OL 52 elements


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y;z The coordinates of the point where !is calculatedt The thickness of the washer where the tangential unit stress Tis calculatedMt The torsion momentMw The bending-torsion moment+ The coefficient that depends on the nature of the stress, according to 8.2.2.1.1 up to

8.2.2.1.6.The calculus characteristics of the sections from the relations 32 and 33 are indicated in table 6depending on the nature of the stress.

8.2.2.1.1Centered axial stress (Mz= My= Bw= 0), +$= 1.

8.2.2.1.2Simple bending (N = Bw= 0), +$= 1.05.Case I: My= 0; Mz ,$0Case II: Mz= 0; My ,$0

For solid web beams in the center of gravity of the flange section, the unit stress must not exceed !aOtherwise, +$$= 1

8.2.2.1.3Oblique bending (N = Bw= 0), +$$= 1.1.

8.2.2.1.4Axial stress and bending by one main axis (Bw= 0), +$$= 1.05Case I: N ,$$0; My= 0; Mz ,$$0Case II: N ,$$0; Mz= 0; My ,$$0

8.2.2.1.5Axial stress and oblique bending (Bw= 0), +$= 1.10.

8.2.2.1.6When all the stresses appearing in relation 32 are different from zero +$= 1.10.

8.2.2.1.7 The calculus characteristics from relation 33 are taken according to table 6 with the

modifications from 8.2.2.1.8.8.2.2.1.8For the boxed elements (figure 23) the third term in relation 33 is:

(34)

where Am= bmhm, is the area en closed by the median contour line (the area shaded in figure 23).

8.2.2.2 The unit stress for local compression !'produced by point loads which act directly on the flangeof a solid web beam is calculated by the relation:

(35)

Figure 23


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whereP The point load transmitted by the wheel;%= 1.7 The dynamic coefficient for the case of the direct action of the load;ti The thickness of the solid web;Z = b + 2h (figure 24). If the rails rest is direct by, without supporting elements :

Z = 2h (figure 25);b The width of the rail supporting element on the flange;h The repartition height up to:

- the axis of the row of neck rivets for riveted beams (figure 24 and figure 25);- bases of the seams which fasten the flange to the solid web, for welded beams

(figure 24);- the end of the connection between the flange and the solid web for laminated

profiles (figure 24)

a) riveted flanges

b) welded flanges or laminated profiles

Figure 24

8.2.2.3 In case of composed stresses which lead to plane states of unit stresses, these are calculated forthe same load group and positions (see 5.1).


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8.2.2.4 The tangent unit stresses $xy and $ yz, one perpendicular to the other and acting on the somesurface element, are added, being checked by the formula:

(36)

8.2.2.5 In case of plane states of unit stresses, in addition to the individual unit stresses is checked alsothe equivalent unit stress, calculated by the formula:

(37)

If the load positions for which the maximum value of the equivalent unit stress, is obtained is unknown,the checking is performed for each of the situations:

!x max and the corresponding!y; $!y max and the corresponding!x; $$max and the corresponding!x; !y

8.2.2.6 The spatial (three-dimensional) stresses are reduced to plane stresses in the most unfavorablesituations

8.2.3 Resistance verifications of the riveted or screwed joints

8.2.3.1 The verifications of the jointing elements (cover plates) and jointing means (rivets and screws) isperformed at the peak maximum stress of the elements or element parts they join.

If the jointing elements (cover plates) have at least the same cross section area (respectively thesame inertia) as the elements they join, their verification is no longer necessary, and shall be performedonly for the jointing means.

8.2.3.2 The jointings of the rompressed rods are checked to that maximum stress, the bucklingcoefficient not being considered. The jointings in the middle rod quarters are checked considering thebuckling coefficient.

8.2.3.3 For the solid web girders, the verification of the covering plates and the rivets or screws that jointhem, is performed:- for the jointing of the flanges: to an axial stress N, according to the formula:

(38)

where:Ac The calculus section of the flange element which is being prolonged;!m The maximum unit stress in the extreme fiber of the flange, in the section of the

joining;- for the jointing of the solid web: to the entire shearing force T, from the section and to the part of the

axial stress N, and of bending moment Mi, which corresponds to the solid web;

(39)

where:N The total axial stress;Ac Gross area of the solid web;Ab Gross area of the entire cross section;

(40)

where:M The bending moment from the cross section of the jointing;li The gross rotative moment of the solid web;l The gross rotative moment of the entire joined section

8.2.3.4 The verification of the riveted joining of the solid webs, is performed by checking of the moststressed rivet by the maximum corresponding effort (Rn), considering all the stresses that can act uponthe joining (the bending moments, axial stresses and the shearing force).


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8.2.3.5 The verification of the neck rivets which fasten the flanges to the webs of the beams with solidwebs (figure 25) are performed the slippage stress and if necessary also to the stress from the loadsapplied directly to the flanges calculated with the relation:

(41)

wheree Distance between the neck rivets;T The maximum shearing force in the section (affected by the dynamic coefficient);S The static moment of the gross section of the strips and angles about the neutral

axis;Ib The gross rotative moment of the entire beam cross section;% Dynamic coefficient (see 8.2.2.2.)P Point load;Z The distribution length (8.2.2.2.; figure 24 and figure 25).

Figure 25

Figure 26

8.2.3.6 The verification of the most stressed rivets is performed by shearing, pressure on the rod andeventually tension in the rod. In case of the simultaneous shearing and tension stresses in the rod, theverification is performed only if !1%!ta,by the relation:


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where!t The normal tension unit stress in the rod;$ The tangent unit stress;!ta The admissible strength for rod tension of the rivet.

8.2.3.7 For the extensions or the jointing where the transmission of the stress is achieved indirectly, byintermediary parts located in between the piece that transmits the stress and the covering piece (coverplate) which undertakes it, the number of rivets is increased by 30% for each intermediary piece. Forexample, at the extension in scale (figure 27) the number n of rivets which join the inferior strip to thecover plate is calculated by the relation:

n = n(1 + 0.3 m) (43)

wheren The number of rivets necessary for the direct transmission of the stress;m The number of intermediary pieces.

8.2.3.8 For jointing with ear angle plates, the number of rivets which corresponds to them must beincreased by 50%, either on the free leg (figure 28 a), or on the leg joined directly to the gusset plate(figure 28 b).

Figure 27

Figure 28

In cases where ear angles are not used, the number of rivets corresponding to the area of the part fromthe section which is not joined directly is increased by 30%.

8.2.3.9 Joinings with high resistance prestressed pre-stressing are verified according to STAS 9330.

8.2.4 Resistance verifications of the joinings and welded seams.

8.2.4.1 The welded seams which undergo simple stresses are verified comparing the maximum effectiveunit stresses (!II; !); $II; $)) from the seams with corresponding admissible strengths from table 12,

according to 8.2.4.1.1 up to 8.2.4.1.4.

8.2.4.1.1For the seams welded stressed by a force P, the verification is performed by the relation:


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P(!I; !); $I;$)) =

As%$!la; !)a; $la; $)a (44)

where

As The calculus section of the seam according to 6.2.2.3

!I; !); $I; $) Effective maximum unit stresses, parallel (II) respectively perpendicularly ()) to thelongitudinal axis of the seam;

!la; !)a; $la; $)a Admissible strength for the parallel unit stresses, respectively perpendicular, to theaxis of the seam, according to table 12;

P Axial stress N or the shearing force T which acts upon the seam.

8.2.4.1.2 For the seams which undergo a bending moment (M), the verification is performed by therelation

M (45)!I; !); $I; $)= ls

-y$%$!la; !)a; $la; $)a

wherels The rotative moment of the welded seams, according to 6.2.2.4;y The distance from the axis of the center of gravity of the seams to the point where

is performed the verification of the unit stress.

8.2.4.1.3For the longitudinal dozzle seams of the solid web beams the verification is performed by therelation:

T .S (46)$'$= l ..a

%$la

where

T The shearing force from the cross section;S The static moment of the surface which slips regarding the center of gravity of thesection:

l The rotative moment of the entire section;.a The sum of the calculus thickness of the seams which undertake the sliding.

8.2.4.1.4For the joinings and welded seams which undergo free or hindered torsion, in the absence of anexact calculus can be admitted that the stresses in the sections located near the seams are undertakenentirely by them.

8.2.4.2 In welded seams which undergo composed stresses which produce biaxial or triaxial states ofunit stresses, are checked as well for individual unit stresses which should not exceed the correspondingadmissible strength, as for the equivalent unit stress calculated by the relation:

The value of the admissible strength !echais indicated in table 12.In relation 47 are introduced the simultaneous unit stresses which merge into the most unfavorablecombination, which came from the same loading situation. In case that the loading situation which givesthis combination cannot be established are considered successively the cases for which results themaximum value for one of the unit stresses, the other unit stresses being introduced with the valueswhich appear simultaneously to it.The verification for equivalent unit stress is not necessary for the joining of the solid web beams, if thecalculus is performed considering that the bending moment is undertaken by the seams from the flanges,the shearing force by the seams of the web, and the axial stress by all the seams.

8.2.4.3 The joining where the effort is transmitted as well by butt weld seams as by jump welding seamsare verified with the relation 44 based on the section and the rotative moment of calculus, determinedaccording to 6.2.2.3.2. The unit stress resulted is not to exceed the admissible strength corresponding tothe butt weld seams from table 12.


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8.2.4.4 The resistance checks are not required for the following seams (see table 7):- the seams from rows 1 4, perpendicular to the direction of the effort, stressed by compression or

compression from bending;- the seam from row 1, butt-weld, quality class 1, in the joining of the webs;- the seams from rows 1 4, of first quality class, stressed by tension and tension from bending,

perpendicular to the direction of the seams,

8.2.5 Resistance checks in case of cooperation between different means of jointure.In the same joining is considered that there can be realized the cooperation:- of rivets and fitting screws;- welding and high resistance screws prestressed;- high resistance screws prestressed and high resistance prestressed fitted screws.

In these cases, the verification of each joining mean is performed for the part of the stress whichcorresponds by cooperation.

8.2.6 Resistance check of the abutment means

8.2.6.1 Checking of the abutment means, according to STAS 4031/1, is performed with the relations fromthis standard, considering the groups of actions specified in table 20.

Table 20

8.2.6.2 The vertical reactions from the indirect action of the wind, are established by reducing the

horizontal forces to the level of the elements of the abutment means which undertake and transmit thetransverse horizontal forces.

No.crt.

Actiongrouping

Considered reactions

Relation or symbolDesignation Direction ofthe action

Total reaction

Maximum reaction from permanent loads

Dynamic coefficient established according toSTAS 1489

Maximum reaction from mobile loads withoutthe indirect effect of the centrifugal force

vertical

Reaction due to the indirect action ofthe centrifugal force

Reaction due to the direct action of thecentrifugal force

Reactions specified in group I(no. crt. 1 3)

Reaction due to the indirect action of the

wind and meanderingLongitudinal reaction due to the brakingforces

Transverse reaction due to the action ofthe wind and meandering

Longitudinal reaction due to the frictionforce of the mobile abutment means

vertical

where

vertical

horizontal

horizontal

horizontal

horizontal


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8.2.6.3 Establishing the pressure on the bearing, is performed with the relations (figure 29):

- for fixed abutment means:

(48)

- for mobile abutment means :

(49)

where:Rvvertical reaction which is established by the following reactions:

- in group I:RvI= Rt+ Rfci (50)- in group II:RvII= Rt+ Rwi +Rsior (51)

RvII= RvI+ Rwi (52)Ro trTransverse horizontal reaction which is established by the following relations:

- in group I:RotrI= Rfcd (53)- in group II:RotrII= Rwd+ Rsd or (54)RotrII= RotrI+ Rwd (55)

RoI and T Have the signification from table 20h; a; b According to figure 29!a The permitted pressure on the contact surface between the inferior plate of the abutment

mean and bearing

Figure 29

8.2.6.4 Fixed abutment means with balancing arm, are verified by determining the bending in thebalancing arm, produced by the pressure on the contact surface between them and the adjoiningelements or between them and the bearings, considering that Rv is distributed uniformly on the contactsurface.

8.2.6.5 For the mobile abutment means, with rollers, shall be checked the balancing arms according to8.2.4.6 and the pressure on the contact line between the balancing arms and rollers.Pressure check on the contact line (!L) is done with the following relations:

- in group I:(56)

- in group II:

(57)


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where:E Steel modulus of elasticity, in newton per square millimeter;Lc The contact length between the balancing arms and rollers, in millimeters;r The radius of the rollers, in millimeters;!aLI; !aLII Acceptable strength, on the contact line, in group I, respectively group II of

actions, according to table 10, in newtons per square millimeters.

The other terms have the signification from table 20 and 8.2.6.3, with the length in millimeters and forcesin newtons.

8.3 Fatigue

8.3.1 Fatigue checks have to prove the safety of the elements, jointing and jointing means usedregarding to the fatigue breakdown under the action of repeated exploitation stresses, which varybetween extreme values of the same direction (oscillating stresses) or of contrary direction (alternatingstresses).

8.3.2 The fatigue checks is performed only for group I of actions STAS 10101/OB), for all the elements

and jointing means which undergo fatigue (observing the dynamic coefficient, but without considering thebuckling coefficient).

8.3.3 The specifications of the present standard regarding the fatigue checks can be applied only forthe steel superstructures of the railway bridges calculated for the T 8.5 convoy (2.1.2 fromSTAS 3220). For the steel superstructures of the railway bridges calculated for other types of convoysthere shall be elaborated corresponding calculation norms.

8.3.4 The time of exploitation of the structures of the new steel bridges designed in accordance withthe specifications of the present standard is of 100 years. If the beneficiary does not require through thetheme other conditions of exploitation, it is always considered the reference traffic of 21 million tons perrail and year.

8.3.5 When undergoing a overhaul repairs the beneficiary of the structure has to require from anauthorized specialized institute an evaluation of the lifetime consumed based on the real traffic from theprevious exploitation period.

8.3.6 The fatigue checking of the elements, of jointing and of means of jointing, is performed by therelation:

(58)

(59)

where:

and observes the following influences:

*1,i considers the characteristic length / of the elements of the supporting structurewhich are being verified, the static system (independent beams or continuousbeams) and the group of notching. The values *1,iare indicated in table 21;

*2 considers the frequency of meeting of the convoys, on supporting structures withmultiple rails.The values *2are indicated in table 22. For the structures with a single rail *2= 1.0;

*3 considers the loading degree of the rail on which the structure being verified, isplaced expressed by total tonnage of the trains per rail and per year. The values *3are indicated in table 23;

%; !max.T8.5; !min.T8.5; $max.T8.5; $min.T8.5; according to 7.4.1.;'!Ra ;$'$Ra The permitted variations of the unit stresses, for the fatigue check, indicated intables 14; 15 and 18.


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Table 21

Simply supported beamsCharacteristiclength

l(m)

Notching group Notching group Notching group

Field Support

Continuous beams


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Table 22

Table 23


8.3.7 For the characteristic length /, required for the coefficient *1,ifrom table 21, are considered:

- for independent beams, their span- for continuous beams, for field cross sections is considered the span of the respective field and for

the cross sections from the area of the intermediary supports and on a distance equal to 0.15 / oneach side of the intermediary supports is considered the arithmetic mean of the spans from thenearby fields of the considered intermediary support.

- For the struts, the sum of the spans of the outriggers or the longitudinal ribs on both sides of theconsidered strut. In case of the plan kings without outriggers or longitudinal ribs, is considered thereal span of the strut.

8.3.8 The coefficient *2, from table 22 depends upon the ratio:

(60)

where'!'; '$' The maximum variations of the unit stress !, respectively $, in the cross section

analyzed from the actions of the T 8.5 convoy, on one of the rails;'!total; '$total The maximum variations of the unit stress !, respectively $, in the cross section

analyzed from the actions of the T 8.5 convoy, on two rails.

8.3.9 For the structures with plankings, when superposing the unit stress from the local bending (L)and general bending (G) the coefficient *1,iis determined by the relation:

(61)

where

(62)

where:'!L; '!G The variation of the unit stresses from the local respectively general bending, in

absolute value. If the most unfavorable combination between the two effects cannot

be established is considered firstly one of the two maximum variation sand the otherone corresponding for the same position of the T 8.5 convoy;/T(L)

/T(G) Coefficients which are being determined by the diagrams in figure 30. For /T(L) isconsidered the span of the outriggers or of longitudinal ribs and for$ /T(G) isconsidered the span of the main beams.

8.3.10 The fatigue check of the elements, jointing and joining means subjected to plane states of unitstresses is performed for each unit stress with the relations (58) and (59), and also for the mostunfavorable unit stresses combination, by the relation:

Milliontonns/year


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where:!x;!y The direct stresses, on the x, respectively y direction, calculated in the point

where the fatigue check is performed;$ The tangential unit stress calculated in the point where the fatigue check is

performed;

!xRa; !yRa;$$RaThe maximum permitted unit stresses for fatigue according to table 16, 17and 19 and the type of notching from table 13.

If the most unfavorable combination of unit stresses cannot be established are considered succesively,the cases when one of the unit stresses is maximum and the others are introduced with thecorresponding values for the same loading case.


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/1-simplysupportedbeamsK=

3.75

/2-simplysupportedbeamsK=

5

/3-continoussupportedbeamsK=3.75

/4-continoussupportedbeamsK=

5


3.75


5

Inscription

Span

L(m)

Figure

30


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For each of the cases is considered the asymmetry coefficient R corresponding to the effort in the pointwhere the fatigue check is performed. The type of notches can be different for each unit stress anddirection of the unit stress.

8.3.11 If for the fatigue checks the maximum unit stresses for fatigue from tables 16, 17 and 19 exceedthe admitted strengths from tables 8, 11 and 12, the check will be performed with the admitted strengthsfrom tables 8, 11 and 12.

8.4 The buckling verification of the straight rods

8.4.1 The buckling verification of the rods with unitary sectionThe rods with unitary section, stressed by centric and eccentric compression, are checked againstbuckling with the relation:

(64)

whereN Centric axial stress

Mz; My Bending moments regarding the axis z-z and y-y;Ab; Wbz; Wby According to table 6;0 The buckling coefficient, according to table 25 up to 28, depending on the

sections groups indicated by table 24. In tables 25 up to 28, / is theslenderness ratio which is calculated by the relation:

(65)

wherelf The buckling length regarding the axis from which the buckling is checked;i The radius of gyration of the gross section regarding the same axis.

Table 24

No.crt.

Classification by sections groups for the buckling calculus

Types of sections and buckling cases Actions groupsymbol

Laminated tubes

Welded tubes

Welded boxed sections

I and H laminated profiles

Profiles I and H welded

I and H laminated profiles, withadditional welded flanges

buckling parallel to theweb

buckling parallel to the flanges

flanges cut with the cutting torch

flanges from strip-steel



buckling parallel to the web

buckling parallel to theweb

U and T laminated profiles

T profiles obtained by cutting laminated I profiles

Profiles with riveted unitary sectionComposed rods fastened by riveting or welding


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Table 25


The buckling coefficient for OL 37, group a of sections

*) for OL 37 the classes 1 and 2, 0is calculated with the values from this table multiplied by k.**) this value is valid for /= 100 104

for /= 105; k = 1.0733for /= 106; k = 1.0811for /= 107 109; k = 1.0900


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Table 26



*) for OL 37 the classes 1 and 2, 0is calculated with the values from this table multiplied by k.**) this value is valid for /= 100 104

for /= 105; k = 1.0766for /= 106; k = 1.0806for /= 107 109; k = 1.0900


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Table 27




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Table 28


8.4.2 The buckling checking of the rods with composed section

8.4.2.1 The rods with composed section, from two or more isolated elements fastened with plates (figure31 a) or braces (figure 31 b) are calculated with relation 64, the buckling coefficient 0 being determinedwith the slenderness according ratio to 8.4.2.2 8.4.2.6.

8.4.2.2 The calculus characteristics of the rods with composed sections are:A area of the gross cross-section of the entire rod;



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Rotative moments of the gross section of the entire rod regarding the main axisy-y, respectively z-z;

Figure 31

- radiuses of gyration of the gross section of the rod regarding the main axis y-y,respectively z-z;

- the buckling length of the entire rod regarding the main axis y-y, respectively z-z(buckling which is produced in a plane perpendicular to these axes);

- the slenderness ratio corresponding to the main axis y-y, respectively z-z(buckling which is produced in a plane perpendicular to these axes);- for the composed rods fastened with plates, represents the slenderness ratio of acomposing element according to the relation:

(66)

where/1 The distance between the axis of two adjoining plates (figure 31 a)

i1 The radius of gyration of a composing element regarding the axis 1-1 (figure 32 35).- for the composed rods fastened with braces (figure 31 b), represents the expression:

(67)

whered The theoretical length of a diagonalz The number of parallel planes where the braces are placed;Ad The gross area of the cross-section of a diagonal (figure 36 a). In case of a double

system, with crossed diagonals (figure 36 b), Ad is the sum of both diagonal cross-section areas;

e The distance between the centers of gravity of the composing elements;/1 The distance between the adjoining cluster joints, from the same composing element.


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Figure 32

Figure 33


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Figure 34

Figure 35


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Figure 36

8.4.2.3 The sections classification of the composed rods for buckling checking is done depending on the

composition, in three groups, as follows:- group I: sections where one of the main axis of inertia does not cross the material; one of theaxes is also the symmetry axis (figure 32 and figure 33);

- group II: sections composed from two cross like placed angles (figure 34);- group III: sections where both of the main axis of inertia do not cross the material (figure 35).

8.2.2.4 For the verification of the composed rods from group 1, to buckling in the direction perpendicularto the axis y-y, is used the transformed slenderness ratio (/yt) according to the relation:

(68)

where m is the number of the composing elements of the composed section which cooperate through

plates or braces.

8.4.2.4.1The ratio has to fulfill the following conditions

and (69)

and to observe the specifications from 8.4.2.9.6.

8.4.2.4.2For the composed rods whose composing elements are close, having in between the adjoiningfront sides a space equal with the thickness of a gusset plate or a little larger, can be taken: /yt=/y, if the

space between the elements is filled with a continuous steel strip.

As described above can be done in case if, in the space between the elements are short steel strips(plates), which observe the condition from 8.4.2.9.5 and 8.4.2.9.6. In this last case in the spaces betweenthe mentioned plates, must exist rivets through disks (washers), spaced at mostly 15 i1.

8.4.2.4.3 The buckling in the perpendicular direction to the axis z-z is checked using the slendernessratio /2according to 8.4.2.2.

8.4.2.5If the condition specified at 8.4.2.5.3 is fulfilled, the verification of the composed rods from group IIis performed only for the buckling in perpendicular direction to the axis z-z, which intersects the material,using the slenderness ratio:


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(70)

where lzand izare taken according to 8.4.2.2.

8.4.2.5.1 If the composed rod (from group II), is a part of a plane system with braces (for example in abeam with braces) and if the leg of one of the angles plates of the section is parallel to the plane of the

system, the buckling length lzis taken equal to the arithmetic mean of the buckling lengths to in the planeof the system and in perpendicular direction to this plane.

8.4.2.5.2For the composed rods made of angles with equal legs, the radius of gyration izcan be takenapproximately:

(71)

where i0 is the radius of gyration regarding the axis which passes through the center of gravity of theentire section and is parallel to the long legs of the angles the axis o-o (figure 34 b).

8.4.2.5.3The l1 / i1ratio shall not be higher than 50 (figure 34 c). Otherwise, a buckling check for eachcomposing element of the composed section shall be performed.

8.4.2.5.4 In order to be considered that they are subjected to centric compression, the rods withcomposed section from group II have to be jointed with ear angles or equipped with fastening platesperpendicular to the plane of the gusset plate and situated near it.

8.2.4.6 For the verification of the composed rods

sr 1911-1998 steel bridges for railway (en)

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