The right choice of steel – according to the Eurocode - Economical Bridge Solutions based on Innovative Composite Dowels and Integrated Abutments - page 15

Figure 6: Stress-Strain diagram from a HISTAR ® 460 steel

For thermomechanical rolled fine grained steels of the new generation using the QST
process (e.g. HISTAR ® steels), it is remarkable that a decrease of the yield strength in respect
to the material thickness can be avoided without an increase of the alloying elements and the
carbon equivalent value. A comparison of the material thickness to yield strength in relation
to steels according to EN 10025 (2004) and modern HISTAR ® steels according to Z-30.2-5
(2008) is given in Fig. 7. As a result, the right choice of thermomechanical steel gives the
designer an economical advantage in design, as presented in the example of application of
this paper.

Figure 7: Comparison of the material thickness t to yield strength f y in relation to steels

according EN 10025 (2004) and modern HISTAR ® steels according to
Z-30.2-5 (2008)

2.2 Ductility

Ductility is required to avoid brittle failure of structural elements. For steels, a minimum
ductility is required that should be expressed in terms of limits for:

the elongation at failure on a gauge length of 5.65√A 0 (where A 0 is the original cross-
sectional area); Eurocode recommends an elongation at failure not less than 15%;
the ratio f u / f y of the specified minimum ultimate tensile strength f u to the specified
minimum yield strength f y ; Eurocode recommends a minimum value of f u / f y ≥ 1.10.