Experimental investigation of the critical collapse behaviour of stiffened box girders under impact bending load

Abstract

For steel thin-walled girders, the loading capacity and failure modes under impact bending load will be significantly different from the static load condition. Critical collapse states, when collapse occurs, are difficult to pinpoint due to the extremely short duration of the impact load and the steady increase in structural deformation. The critical collapse state of the box girders under impact loading should be defined considering the progressive failure process of yielding or buckling from the expansion of local structural members into global regions. In this paper, seven impact experiments were conducted using a drop hammer facility to investigate the failure mechanism and dynamic capacity of the box girders under the impact bending. Three identical girders, fabricated using the same material and welding process, were designed. Seven impact cases were performed, each with varying impact velocities, to measure hammer acceleration, structural strain, and structural displacement. For a smooth transition from intact to collapsed girder in tests, replace it once major plastic deformation occurs. The experimental results were used to obtain the curves of impact load and structural dynamic response. Numerical studies were conducted using the finite element method (FEM) to investigate the dynamic response of girders under various impact velocities, and the results were compared with the experimental results. The critical collapse state of the girder under impact bending was determined. Based on the FEM results for the additional girders of various scantlings, the critical impact velocity of the girders is shown to be related to the cross-section properties. These conclusions are useful for assessing the safety of the box girders under impact bending loads.