Moment Resistances of wide flange beams with initial imperfection and residual stresses

Abstract

Elastic and inelastic moment resistances of W-steel beams with considering the effects of initial imperfections and residual stresses are numerically investigated in the present study. The numerical model is implemented in ABAQUS in which residual stresses are incorporated by using initial conditions while the initial imperfection is imported through the first lateral-torsional buckling mode. By comparing the FEA moment resistances of W250x45 steel beams against those of the CSA S16 and Eurocodes 3 design standards, it is observed that (i) If the effects of initial imperfections and residual stresses are excluded, the inelastic resistances are close to a fully plasticized section moment. In contrast, if the effects are included, the inelastic resistances are significantly smaller than the fully plasticized moment. (ii) The effects of initial imperfections on the moment resistance are significant for intermediate and long spans. Although the initial imperfection taken in the present study is 4.0 mm, that is within the allowable limit specified in the design standards (i.e., not greater than L/1000), the moment resistances with the taken imperfection are considerably smaller than the design moments specified in the design standards, and (iii) When considering steel beams with the effects of initial imperfection and residual stresses, the moment resistances based on the CSA S16 and EC3-6.3.2.3 solutions are higher, while those based on EC3-6.3.2.2 solution are lower than the moment capacities of the beams with the initial imperfection. This indicates that EC3-6.3.2.2 clause is the most safety design for the moment resistances.