Experimental Investigation on Composite Girders With CSW-CFST Truss Chords Subjected to Combined Flexure and Torsion

As a new type of composite girders, composite girders with corrugated steel webs and concrete-filled steel tubular (CSW-CFST) truss chords are extensively utilized in bridge engineering. To examine the structural behavior of composite girders with CSW-CFST truss chords subjected to combined flexure and torsion, model tests and finite element analysis (FEA) are employed. Using these efficient tools, the strain distribution, deformation law, failure mode, and bearing capacity of these composite girders subjected to pure torsion and combined flexure and torsion are methodically obtained. The primary objectives are to probe the applicability of existing flexure-torsion relation curves and introduce the calculation method for the bearing capacity of composite girders with CSW-CFST truss chords subjected to combined flexure and torsion. The obtained results reveal that their failure mode is influenced by the initial torsional moment. Further, their bearing capacities due to the applied initial torsional and bending moments can be maximally enhanced by about 21.6% and 6.6%, respectively. The deviation between the predicted bearing capacity by the FEA and that obtained from the tests is less than 8.6%, demonstrating the high accuracy of the FEA model. The contribution of the torsional moment to the flexural bearing capacity is either ignored or underestimated by the existing flexure-torsion relation curves, with a minimum deviation of about 22.3%. By comparing the results acquired by the extended FEA and the calculation method proposed in this paper, it is proved that the proposed calculation method for the bearing capacity of composite girders with CSW-CFST truss chords subjected to combined flexure and torsion may reduce the deviation from 22.3% to 8.3%.