ULTIMATE CAPACITY OF NARROW TYPE STEEL BOX SECTION FOR RAILWAY SELF-ANCHORED SUSPENSION BRIDGE UNDER BIAS COMPRESSION

The steel box section, with its excellent performance, has been extensively applied in self-anchored suspension bridges.The ultimate capacity of such sections, which needs to be exactly predicted, is crucial to the safety of the whole bridge.A narrow type steel box section (NTSBS) with width to height ratio of 4.18 is deployed in Egongyan Rail Special Bridge, which is a railway self-anchored suspension bridge with 1120 m span in total.In order to comprehensively investigate the ultimate capacity of NTSBS, the behavior of NTSBS under the most unfavorable internal forces is herein studied by means of experiments and numerical simulations.Firstly, a representative steel box girder is selected to be an experimental rescale model and the most unfavorable internal forces are determined by computation analysis.Then, a load test is conducted on the rescale model of NTSBS girder.The experimental method is introduced, including the loading method and layout of measuring points.During this loading procedure, the prestress loss of the steel strands in the self-loading system is considered in order to improve the accuracy of the actual eccentric loading.Subsequently, a finite element (FE) model meshed by shell element is validated using the test results and is used to investigate effects of residual stress and geometric imperfections.Finally, the FE method is extrapolated to the full scale model, the actual ultimate capacity is obtained, and effect of geometric imperfections of mid webs and failure mechanism are investigated.