Thomas Grant 1.SCOPE
1.1 This code is primarily intended to apply to the superstructure of simply supported steel bridges of spans up to 100 m (325 ft) between centers of bearings. Where appropriate, the provisions of the code may be adopted for larger spans or other types of steel bridges, but care should be taken, in these circumstances to make whatever amendments are necessary for fixity at the supports, continuity, and other indeterminate or special conditions.
1.2 Where bridges of the through or semi-through type are adopted, they must be designed to allow for clearances specified in the appropriate schedule of dimensions, for different gauges in the case of Railway bridges or bridges over Railway, and in the case of road bridges clearances as specified by the appropriate authorities.
1.3 For road bridges the design and construction shall comply with the Standard Specifications and Code of Practice for Road-bridges issued by the Indian Roads Congress.
1.4 Any revision or addition or deletion of the provisions of this code shall be issued only through the correction slip to this code. No cognizance shall be given to any policy directives issued through other means.
Note:
- Unless otherwise specified the word „span‟ shall mean effective span.
- Where FPS equivalent are given the figures in the metric units are to be regarded as the standard.
The FPS conversions are approximate. More accurate conversions should be based on IS: 786. - Attention is drawn to the fact that equations in the text, for which no units are specified, are applicable in any system of units, metric or FPS, provided the unit of length and the unit of force used in an equation are the same throughout.
- MATERIALS AND WORKMANSHIP
2.1 Materials and workmanship, including protection against atmospheric corrosion, shall comply with the Indian Railway Standard Specifications B-1, B-2 and B-6 and other specifications mentioned therein.
2.2 This code makes reference to the following standards:
Indian Railway Standard Codes and Specifications
Welded Bridge Code – 1972
B-1 Steel girder bridges
B-2 Erection and riveting of bridge girders
B-6 The manufacture of locomotive turn- tables
M-2 Steel castings
- LOADS, FORCES AND STRESSES
3.1 Loads and Forces to be Taken into Account- For the purpose of computing stresses, the following items shall, where applicable be taken into account in accordance with the requirements specified in the Bridge Rules:
(a) Dead load.
(b) Live load.
(c) Impact effect.
(d) Forces due to curvature and eccentricity of Track.
(e) Temperature effect.
(f) Resistance of expansion bearings to movements
(g) Longitudinal force.
(h) Racking force.
(j) Forces on parapets.
(k) Wind pressure effect.
(l) Forces and effects due to earthquake.
(m)Erection forces and effects.
(n) Derailment loads.
Subject to the provisions of other clauses, all forces shall be considered as applied and all loaded lengths chosen in such a way that the most adverse effect is caused on the member under consideration.
3.2 Combination of Loads and Forces- The following combination of forces shall be considered.
3.2.1 The worst combination possible of dead load with live load, impact effect and forces due to curvature and eccentricity of track. When considering the member whose primary function is
to resist longitudinal and racking forces due to live load, the term live load shall include these
forces.
3.2.2 In case of bridges situated in seismic zones I to III as given in Bridge Rules, only bridges of overall length more than 60 m or individual span more than 15 m for the worst possible
combination of any or all the items „a‟ to „j‟ & „k‟ or „l‟ listed in clause 3.1
3.2.3 In cases of bridges situated in seismic zone IV & V as given in Bridge Rules, the worst
combination possible of any or all the items „a‟ to „j‟ and „k‟ or „l‟ listed in clause 3.1
3.2.4 The worst combination possible of loads and forces during erection.
3.2.5 In case of ballasted deck bridges, the combination of dead load and derailment load
shall be considered as an occasional load.
3.3 Primary and Secondary Stresses
3.3.1 Primary Stress- The primary stresses in the design of triangulated structures are defined as axial stresses in members calculated on the assumption that
all members are straight and free to rotate at the joints;
all joints lie at the intersection of the centroidal axes of the members;
all loads, including the weight of the members are applied at the joints.
- SCOPE … 1
- MATERIALS AND WORKMANSHIP … 1
- LOADS, FORCES AND STRESSES … 3
3.1 Loads and Forces to be taken into account … 3
3.2 Combination of Loads and Forces … 3
3.3 Primary and Secondary Stresses … 3
3.4 Relief of Stresses … 5
3.5 Allowable Working Stresses for combinations of Loads and Forces … 5
3.6 Fluctuations of Stress (fatigue) … 6
3.7 Permissible Stresses … 7
3.8 Allowable Working Stresses for Parts in Axial Compression. … 7
3.9 Allowable Working Stresses in Bending … 14
3.10 Allowable Shear Stress in Solid Webs of Plate Girders … 21
3.11 Combined Stresses … 21
3.12 Allowable Working Loads on Cylindrical Roller and
Spherical Expansion Bearings … 22
3.13 Allowable Working Pressure on Sliding Bearings. … 23
3.14 Basic Permissible Stresses for Cast Steel in Bearings … 24
3.15 Cast Iron … 24
3.16 Allowable Working Pressure under Bearings or Bed Plates … 24
3.17 Slab Bases for Bearings … 24
3.18 Basic permissible Stresses in Wrought Iron and
Mild Steel of Early Manufacture. … 24
3.19 Special Notes on Working Stresses … 25
3.20 Existing Bridges - DESIGN AND CONSTRUCTION – GENERAL … 26
4.1 Effective Spans … 26
4.2 Effective Length of Struts … 26
4.3 Sectional Area … 27
4.4 Symmetry of Sections … 28
4.5 Minimum Sections … 29
4.6 Spacing and Depth of Girders … 29
4.7 Provision for Temperature, Stress and Deflection … 29
4.8 Anchorage … 29
4.9 Track Structures … 30
4.10 Clevises and Turnbuckles … 30
4.11 Composite Action of Steel and Concrete … 30
4.12 Composite Use of Mild Steel and High Tensile Steel … 30
4.13 Composite Connections … 30
4.14 End Cross Members … 30
4.15 General Provision Against Corrosion … 30
4.16 Camber … 30
4.17 Deflection … 31 - SOLID WEB GIDERS … 31
5.1 Plate Girders and Rolled Beams … 31
5.2 Effective Sectional Area … 31
5.3 Slenderness Ratio … 32
5.4 Effective Length of Compression Flanges … 32
5.5 Flanges … 35
5.6 Connection of Flanges to Web … 36
5.7 Curtailment of Flange Plates
5.8 Web Thickness … 36
5.9 Web Edges … 36
5.10 Web Stiffeners … 36
5.11 Flange Splices … 39
5.12 Splices in Web … 39
5.13 Lateral Bracing … 39 - OPEN WEB GIRDERS … 40
6.1 Intersection at Joints … 40
6.2 General Requirements for Compression Members … 40
6.3 Effective Length of Compression Members other than lacings … 41
6.4 Compression Members Composed of Two Components Back-to-Back 43
6.5 Lacing of Compression Members … 44
6.6 Battening of Compression Members … 45
6.7 General Requirements for Tension Members … 47
6.8 Tension Members Composed of Two Components Back-to-Back … 47
6.9 Lacing of Tension Members … 47
6.10 Battening of Tension Members … 49
6.11 Splices … 49
6.12 Connection at Intersections … 50
6.13 Lug Angles … 50
6.14 Section at pin Holes in Tension Members … 50
6.15 Pin Plates … 51
6.16 Diaphragms in Members … 51
6.17 Lateral Bracing
6.18 Sway Bracing
6.19 Portal Bracing - RIVETING, BOLTING AND WELDING … 52
Effective area in Shear and Bearing of Rivets, Bolts and Pins
Deductions for Holes for Rivets, Bolts and Pins
Minimum Pitch of Rivets and Bolts
Maximum Pitch of Rivets and Bolts
Edge Distance
Hand Driven Rivets
Rivets or Bolts Through Packing
Long Grip Rivets
Rivets in Tension
7.10 Bolts
7.11 General Requirements for Welds
7.12 High Strength Friction Grip (HSFG) Bolts
