Study On Flexural Behavior Of Rectangular RACFST Beams

Recycled aggregate concrete filled steel tube(RACFST),which consists of recycled aggregate concrete(RAC)and steel tube,can not only take advantage of both steel tube and RAC,but also make up for their drawbacks while bearing alone.The local buckling of steel tube can be avoid or delayed due to the supporting of the core concrete;meanwhile,the confinement provided by the outer steel tube can improve the weakness of strength and elastic modulus,shrinkage and creep of the RAC.The application of RACFST is an effective way to solve the dumping of the waste construction garbage and to relieve the shortage of the natural aggregates.Rectangular RACFST generally has big section moment of inertia and flexible space layout.In practical project,the end of cantilever is often subjected to bending moment,and simultaneously the study on flexural behavior of a composite member is the foundation for the investigation of its performance under combined bending and compression.Therefore,it is very important to study the flexural performance of rectangular RACFST.The behavior and design method of rectangular RACFST under flexural loading are studied experimentally and theoretically in this paper.The main research works are as follows:(1)Tests of 10 beam specimens are carried out to investigate the effect of the recycled coarse aggregate replacement ratio,the sectional depth-to-width ratio and the width-tothickness ratio of steel tube on the failure pattern,moment versus deformation curve,moment capacity and flexural stiffness of the specimens.(2)The finite element analysis(FEA)model is developed by the software ABAQUS based on the determination of the rational constitutive model of steel and core RAC.The predicted failure pattern,moment versus deformation curve and moment capacity generally agree well with the experimental results.(3)Based on the verified FEA model,the influence of recycled coarse aggregate replacement ratio,the depth-to-width ratio,steel ratio and the strength of steel and original concrete on the performance and mechanism of rectangular RACFST beams is investigated.(4)The simplified formulae for the moment capacity of rectangular RACFST are suggested according to the parametric analysis results,and the simplified calculation results accord well with the experimental results.