Behavior Of FRP-Interlayer-Steel Tube Concrete Stub Columns Under Axial Compression

Concrete-filled steel tubular(CFST)structures have been widely used in high-rise buildings,bridges and underground structures due to high bearing capacity,construction convenience and good seismic behaviors.With the development in the application area of CFST,the environment has become harsher,which make steel tube corrode easily and need spend considerable amount of money on the anti-rust measures and routine maintenance.In order to improve the corrosion resistance of CFST,the FRP-interlayer-steel tube concrete columns(FIST)are proposed in this dissertation.Grouting material is used to bond the FRP tube and steel tube to produce a duel-confined composite skin for core concrete.The composite tube is then transported to the construction site,erected on the cushion caps and concreted from inside.FIST is durable for corrosion,high in bearing capacity and easy for assembly construction,which provides large prospects and good potential of applications in bridge construction,building structures and offshore platforms.This dissertation focuses on the experimental study and finite element analysis of FIST stub columns.The specific research work is as follows:(1)Axial compression tests on three FIST stub columns,three FRP-steel tube concrete stub columns(FSCC)and three CFST stub columns are conducted to investigate the failure modes and mechanical behaviors.The experimental results indicate that the confinement from FRP restrains the local buckle of steel tube.The interlayer improves the bearing capacity and ultimate axial deformation of members.The processing of FRP-interlayer-steel tube is practicable and operational.(2)Axial compression tests on twelve FIST stub columns are conducted to investigate the influence of the thickness of FRP tube and steel tube on failure modes and mechanical behaviors.The test results show that the thickness of FRP tube has great influence on the ultimate load and axial deformation of specimens.The ultimate load and deformation increase linearly with the increase of the FRP tube.The ultimate load increases slightly with the increase of the steel confinement factor,but the axial deformation stay stably.Within the range of column height,the transverse deformation and confinement of the FRP tube is uniform.(3)The finite element model of the FIST stub column is built with ABAQUS and verified according to the comparative analysis with test results.The effects of FRP types,the strength of steel tube and core concrete on the axial compressive behaviors of FIST columns are investigated.Based on the mechanical behaviors of FIST stub columns and the existing calculation methods of bearing capacity of composite structures,the method of calculating axial compressive capacity of FIST stub columns is proposed.