LAUSR

Abstract Concrete-filled steel tubular (CFST) trusses are widely used in bridge construction. Inadequate pumping of the concrete and other faults during construction and shrinkage of the concrete may cause interfacial imperfections such as debonding separation at the steel-concrete interface in many early built CFST arch bridges. It is important to investigate the effects of interfacial imperfections on the flexural behavior of CFST trusses. For this, experimental investigations are carried out and four experimental truss models with different interfacial imperfections are tested under four-point bending. Finite element models are also developed to conduct the corresponding mechanism and parametric analyses. The test results show that interfacial imperfections between the steel tube and concrete core have significant effects on the ultimate loading capacity of CFST trusses. The ultimate loading capacity of tested models with 100% interfacial separation, 10% depth separation and 20% depth separation are 9.2%, 18.0% and 37.7% lower than that of the model with fully bonded steel tube and concrete core. The finite element model is validated by the test results and is used to conduct further parametric studies for effects of interfacial imperfections such as friction coefficient, interfacial separation ratio and depth separation ratio on the ultimate load carrying capacity of CFST trusses. The finite element results show that the effect of depth separation on the ultimate load of CFST truss is more significant than other interfacial imperfections, and that the ultimate load of models with a depth separation ratio kh = 10% and kh = 20% are 13% and 33% lower than that of the model with no depth separation. Therefore, it is very important to avoid the depth separation problem in the CFST truss structures.