Wide flanges of steel box bridge girders with limited plasticisation

Eurocode 3 code allows plastic bending resistance to be considered for ultimate limit state calculations if certain requirements are fulfilled. If all the requirements are not satisfied, the new code version prEN 1993‐1‐5:2022(E) allows for limited plasticisation, but it does not provide guidelines for design scenarios. This study analyses the utility of the new version and offers some additional suggestions for improvements. The stress state of a wide girder flange is tracked together with the strain state, and an upper (plastic) strain limit is introduced. The interaction between wide flanges and webs under these circumstances is established. A procedure is developed for calculating the effective width of the flange by controlling the degree of plasticisation. This procedure ensures that the stress states of the flange and the web agree around their contact point. Further, the girder bending resistance is determined with minimal additional design effort. Examples are presented to highlight the effects of these suggestions under different circumstances. The results are compared with those obtained based on the new version of the code.