The Design of Modern Steel Bridges - TEDI

90 The Design of Modern Steel Bridges
References
Buckling of compression flanges of laterally unsupported beams could not
be included in the derivation of the target reliability, as the available statistical
data on the modelling uncertainty were considered to be inconsistent. After
further research into these data, a g m value of 1.20 was adopted for the design
rules in the year 1982 version of reference[8]. The buckling strength formula
for laterally unsupported beams was changed in the year 2000 version of
reference[8], and g m to be used in conjunction with the latest formula has been
specified as 1.05. For buckling of webs of beams in shear, a g m value of 1.05
was considered appropriate for webs of low slenderness which fail primarily by
yielding, while a g m value of about 1.25 was required for very slender webs
that fail by the tension-field mechanism. In the design rules, a g m value of 1.05
was stipulated, along with a variable adjustment factor incorporated in the
strength formula. The calibration exercise showed that the use of these g m
factors and the strength formulae given in BS 5400 Part 3, along with the g fL
and gf3 factors given in BS 5400 Part 2, would require approximately 6% less
steel than in the previous design practice, while achieving the same degree of
reliability on average. Another benefit was the very significant reduction in the
scatter of the failure probability about this mean value, as can be seen from
Table 4.3.
1. Building Code Requirements for Reinforced Concrete (ACI 318–77). American
Concrete Institute, 1977.
2. Specifications for the Design, Fabrication and Erection of Steel Buildings.
American Institute of Steel Construction, 1978.
3. AASHTO Standard Specifications for Highway Bridges, American Association of
State Highway and Transportation Officials, 1996.
4. CP 110: Part 1: 1972. The Structural Use of Concrete. British Standards Institution,
London.
5. BS 5400: Part 1: 1978. Steel, Concrete and Composite Bridges. British Standards
Institution, London.
6. Flint A. R. et al. 1981. The Design of Steel Bridges. Paper 2: The derivation of
safety factors for design of highway bridges. Granada, London.
7. BS 5400: Part 2: 1978. Steel, Concrete and Composite Bridges: Specification for
Loads. British Standards Institution, London.
8. BS 5400: Part 3: 1982: Code of Practice for Design of Steel Bridges. British
Standards Institution, London.
9. BS 153: 1958. Specification for Steel Girder Bridges. British Standards Institution,
London.