SEISMIC BEHAVIOR OF PRECAST CONCRETE FILLED DUAL STEEL TUBE COLUMNS IN SOCKET FOUNDATIONS

This paper presents an experimental study on the seismic behavior of precast concrete filled dual steel tube (CFDST) columns in socket foundations.The type of socket foundation is a good choice to accelerate the construction of precast CFDST structures, which involves embedding the precast CFDST column portion into a cavity within the precast footing and then filling the cavity with cast-in-place concrete or grout.In this study, five precast CFDST columns with various column base details were tested under simulated seismic loads until failure, and the effects o f embedment depths and details of column bases on the seismic behavior were evaluated.The test results indicate that all precast CFDST columns with an embedment depth into the socket foundations larger than 1.0D (D is the outer diameter of the column) achieved a desirable plastic hinge failure at the column base.The further increase of the embedment depth larger than 1.0 D and the use of CFRP wraps to confine the column base had no significant improvement on the seismic behavior of the specimens.However, the use of steel rings and the un-bond region left in the column base significantly improved the deformation capacity, ductility and energy-dissipation capacity of the specimens.