RESEARCH ON THE ULTIMATE BEARING CAPACITY AND SIMPLIFIED DESIGN FORMULAE OF STEEL TRUSS WEB-STEEL REINFORCED CONCRETE (SRC) COMPOSITE ARCHES

The steel truss web-steel reinforced concrete (SRC) composite arch is a novel structure, which combines the advantages of convenient and efficient construction of a stiff skeleton frame and can greatly reduce the self-weight of composite structure action. It is anticipated to increase the spanning capacity of arches and has a good engineering potential. Based on the trial-design of a steel truss web-SRC composite arch bridge of a span of 420m, experiments were carried out on the mechanical behavior of a steel truss web-SRC composite arch model. The experimental results show that:the arch model appeared entire failure mode rather than an out of plane buckling failure; the rates of plastic deformation of the composite arch along the arch axis were much higher than those along the cross-sectional height; final failure of the arch was due to the excessively expanding of the plastic region; the failure mode was similar to the extreme point buckling failure mode of a concrete filled steel tube (CFST) arch. Finite element analysis was also conducted to simulate the mechanical performance of the composite arch. It is shown that the bearing capacity of the composite arch was increased with the increasing wrapping coefficient of external concrete. The bearing capacity was also enhanced with the increase in the ratio of the outer diameter between the web member and the chord. However, the improvement was insignificant when such ratios exceeded a certain limit. The layout details of the steel web members had a great influence on the bearing capacity of the composite arch as well. Based on the test results and the finite element analysis, a simplified design formulae for the determination of ultimate bearing capacity of the composite arch was proposed.