Bending Performance of Lightweight Aggregate Concrete-filled Steel Tube Composite Beam

摘要

A composite beam, which consists of a Lightweight Aggregate Concrete Filled Steel Tube (LACFST), and a reinforced concrete slab deck, was investigated. Bending tests were performed to study its behaviour. Based on the test results and the assumptions therein, calculation methods proposed and design suggestions were proved by finite element analysis. The results shows that the composite beam had good ductility and high bearing capacity. The design bearing capacity can be calculated using a force balance method. The flexural stiffness, at the serviceability-level, can be found by superposition of the slab deck and LACFST beam stiffness. A three-line M-δ model was proposed for the lightweight aggregate concrete steel tube composite beam moment–deflection evolution. After validation by finite element analysis, the neutral axis was suggested as lying between the top of the steel tube and the bottom of the concrete deck when the composite beam failed.