USEOF WELDING IN BRIDGES AND STRUCTURES SUBJECT TO DYNAMIC LOADING - CODE OF PRACTICE
1 SCOPE
1.1 This standard covers the use of manual, semiautomatic
and automatic metal-arc welding processes
in the fabrication of steel bridges and structures subject
to dynamic loading by welding.
1.2 This standard also applies to the design, different
stresses to be considered for the design, and
construction of the bridges.
1.3 The welding procedure for this standard shall
apply to IS 9595: 1996 ‘Metal arc welding of carbon
and carbon manganese steels--Recommendations first
revision)‘.
1.4 All the provisions stated for the inspection
of welds in IS 822: 1970 ‘Code of procedure for
inspection of welds’, shall be applicable in conjunction
with the provisions of this standard.
The following Indian Standards contain provisions
which, through reference in this test constitute
provisions of this standard. At the time of publication,
the editions indicated were valid. All standards are
subject to revision and parties to agreements based
on this standard are encouraged to investigate the
possibility of applying the most recent editions of the
standards indicated below:
Title
Carbon dioxide (second revision)
Glossary of terms relating to
welding and cutting of metals
Covered electrodes for metal arc
welding of structural steel first
revision)
Code of procedure for inspection
of welds
Low and medium alloy steel
covered electrodes for manual metal
arc welding (third revision)
Steel for general structural
purposes (fourth revision)
Acceptance tests for wire - flux
combinations for submerged arc
welding of structural steels (first
revision)
Submerged arc welding of mild steel
and low alloy steels -
Recommendations first revision)
Compressed argon (first revision)
Welding rods and bare electrodes
for gas shielded arc welding of
structural steel (first revision)
Bare wire electrodes for submerged
arc welding of structural steels
Approval tests of welding procedures:
Part 1 Fusion welding of steel
Approval tests for welders working
to approved welding procedures:
Part 1 Fusion welding of steel
Approval tests for welders when
welding procedure approval is not
required: Part 1 Fusion welding of
steel
Structural steel-micro alloyed
(medium and high strength
qualities) C firs revision)
Metal arc welding of carbon and
carbon manganese steels -
Recommendations firs revision)
CO, gas shielded metal arc
welding of structural steels -
Recommendations first revision)
For the purpose of this standard, the definitions
given in IS 8 12 shall apply.
4 MATERIALS
4.1 Steel
All steels for the fabrication of structural members,
connections and sections shall be of weldable quality
conforming to IS 2062, IS 8500 and its equivalent
having a maximum carbon equivalent of 0.53 when
calculated by using the formula:
Carbon equivalent = C+-Mn+ Cr+Mo+V+Ni+Cu
6 5 15
4.2 Welding Consumables
4.2.1 Electrodes for Manual Metal Arc Welding
(MMA W)
Covered electrodes shall conform to IS 814 and
IS 1395 as appropriate.
4.2.2 Wire and Flux for Submerged Arc Welding (SAW)
Filler wires shall conform to IS 7280. The wire and
flux combination shall conform to IS 3613 and
IS 4353, as appropriate.
4.2.3 Filler Rods, Wires and Shielding Gases for Gas
Shielded Metal Arc Welding (GMA W)
The filler rods or wire for shielded procedure shall
conform to IS 6419. Electrodes for unshielded or self
shielded procedures are generally of the cored type
and shall deposit weld metal with mechanical properties
not less than those specified as satisfactory for the
particular grade of steel being welded. The shielding
gases may be argon conforming to IS 5760 or CD2
conforming to IS 307. The use of gas mixture IS
permissible, provided they have been proved to be
satisfactory. When a gas mixture is used which has
specified additions, the variation of such additions
shall not exceed +lO percent of the stated.
5 FLUCTUATION OF STRESSES (FATIGUE)
5.1 General
All structural details shall be designed to avoid, as
far as possible, stress concentrations likely to result
in excessive reduction of the fatigue strength of
members or connections. Care shall be taken to avoid
sudden change of shape of a member or part of a
member, especially in regions of tensile stress or local
secondary bending, and steps shall be taken to avoid
aerodynamic and similar vibrations.
5.2 Loads and Stresses to be Considered
Working stresses shall be reduced, where necessary,
to allow for the effects of fatigue. Allowance for
fatigue shall be made for combinations of stresses due
to dead load, live load, impact, lurching and centrifugal
force, including secondary stresses due to eccentricity
of connections and off-joint loading in latticed
structures. Stresses due to wind, temperature and
longitudinal and nosing force, and secondary stresses
due to elastic deformations and joint rigidity, may be
ignored in considering fatigue.
5.2.1 Elements of a structure may be subjected to a
very large variety of stress cycles varying both in
range $JM~J and in magnitude. f,, of maximum
stress. Each element of the structure should be designed
for the number of cycles of different magnitudes of
stress to which that element is liable to be subjected
during the expected life of the structure. The number
of cycles of each magnitude should be estimated by
the engineer in the light of cycles of each magnitude
should be estimated by the engineer in the light of
available data regarding the probable frequency of
each type of loading.
5.2.2 In order to allow for the effect of fatigue the
procedure set down in 5.3 shall be followed , using
the information supplied in Tables 1 to 7. These tables
give the maximum allowable stresses f for different
values of f min,/f Max,,N, , or conversely, values of N
for different values off M,. The notations used represent
the following:
f = maximum allowable tensile or comprehensive
working stress
f min = minimum stress in the element during a
particular stress cycle,
f max= maximum stress in the element during the
same stress cycle, and
N = allowable number of repetitions of this stress
cycle.
5.3 Allowable Working Stresses
5.3.1 In the case of members subjected to a number
of repetitions n, of a single stress cycle, the allowable
working stresses shall be those given in Tables 1 to
7, taking n = N and f max=f. In such cases, if the stress level of f max is smaller then the allowable stress f specification for 10’ cycles, fatigue need not be considered.
5.3.2 In the more general case of members subjected
to a stress spectrum, that is to number of cycles, n,,
n,, etc, different maximum stress levels f,, f2, etc, or
of different ratios of f min /f max or broth are following design method shall be used:
4 All cycles with a maximum stress equal to or
lower than the allowable stress quoted for Class
G type connections in Table 7 for 10” cycles
and For the relevant ratio of f min /f max,shall be
ignored.
b)
Where the loading conditions do not give rise
to groups of clearly defined stresses, all stresses
greater than the allowable stress obtained from
!- able 7 - Class G, as defined in (a), shall be
divided into at least live selected representative
stress levels approximately equally spaced
between the minimum and the maximum of the
stresses to be considered.
For each of the stress cycles the maximum
allowable number of cycles N,, N,, etc, shall
be determined from Tables 1 to 7 by
interpolating the values, if necessary.
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