Box girder strength under pure bending: Comparison of experimental and numerical results

The progressive collapse behavior of box girder models are studied by the Finite Element Method (FEM) using component and global approaches. By the global FEM method four-point bending is simulated. The nonlinear module of the commercial FEM system COSMOS/M is used. Initial deflections and welding residual stresses are included. Reasonable welding residual stresses are obtained by initial thermal loading and unloading. It is shown that the residual deflections resulting from the thermal stage do not affect the collapse behavior, hence the assumed initial deflections in the buckling modes are not changed. Unloading and reloading in the pre-collapse range are carried out to simulate the welding stress relief in experiments. The ultimate strength is not affected, suggesting that residual stresses are not relieved. Toward an improved efficiency of the global FEM method half-breadth models are validated.