Nonlinear Material Behavior of the Bridge Components - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 55

In Europe, EC3 (BS EN 1993-1-1) [ 2.11 ] specifies that the nominal
values of the yield strength f y and the ultimate strength f u for structural steel
used for buildings and bridges should be obtained either by adopting the
values f y ¼R eh and f u ¼R m direct from the product standard or by using
the simplification given in Table 2.5 , where R eh and R m are yield and ulti-
mate strengths to product standards. EC3 [ 2.11 ] also specifies that for struc-
tural steels, a minimum ductility is required, which should be expressed in
terms of the limits for the ratio f u / f y (the specified minimum ultimate tensile
strength f u to the specified minimum yield strength f y ), the elongation at fail-
ure on a gauge length of 5 A p (where A o is the original cross-sectional

area), and the ultimate strain e us (where e us corresponds to the ultimate
strength f u ). It should be noted that EC3 [ 2.11 ] specifies that the limiting
values of the ratio f u / f y , the elongation at failure, and the ultimate strain
e u may be defined in the National Annex of the country of construction.
Alternatively, EC3 recommends that f u / f y 1.10, elongation at failure
not less than 0.15, and e u 15 e y , where e y is the yield strain ( e y ¼f y / E s ). Gen-
erally, steels conforming with one of the steel grades listed in Table 2.5
should be accepted as satisfying these requirements. According to EC3,
the modulus of elasticity of steel E s ¼ 210 000 N/mm 2 , shear modulus
G¼ 81,000 N/mm 2 , Poisson's ratio in elastic stage n¼ 0.3, and the coeffi-
cient of linear thermal expansion a¼ 12 10 6 per K (for T 100 C).
It should be noted that for calculating the structural effects of unequal
temperatures in composite concrete-steel structures to EC4 [ 2.12 ] , the
coefficient of linear thermal expansion is taken as a¼ 10 10 6 per K.
Bolts, nuts, and washers used for bridges, according to EC3 (BS EN
1993-2) [1.27], should conform to the reference standards given in EC3
(BS EN 1993-1-8) [ 2.13 ], 2.8: Group 4. The different bolt grades used in
bridges are presented in Table 2.6 . The nominal values of the yield strength
f yb and the ultimate tensile strength f ub are shown in Table 2.6 , and they
should be adopted as characteristic values in calculations, while high-
strength structural bolts of grades 8.8 and 10.9, which conform to the ref-
erence standards given in BS EN 1993-1-8 [ 2.13 ], 2.8: Group 4, may be
used as preloaded bolts when controlled tightening is carried out in accor-
dance with the reference standards given in BS EN 1993-1-8 [ 2.13 ], 2.8:
Group 7. In addition, EC3 (BS EN 1993-2)[1.27] specifies that steel grades
in accordance with the reference standards given in BS EN 1993-1-8 [ 2.13 ] ,
2.8: Group 1, steel grades in accordance with the reference standards given
in BS EN 1993-1-8, 2.8: Group 4, and reinforcing bars conforming to EN
10080 [ 2.14 ] may be used for anchor bolts. The nominal yield strength for
anchor bolts should not exceed 640 N/mm 2 .

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