Experimental Research On Seismic Behavior Of Concrete-filled Round-ended Stainless Steel Tubular Bridge Piers

Concrete-filled round-ended stainless steel tubular(CFRSST)bridge pier is a new type of high-performance steel-concrete composite bridge pier,which is composed of steel tube with a round-ended shape,as well as core concrete.This type of piers has the advantages including superior seismic performance,light weight,convenient construction and good corrosion resistance,etc.Research has been carried out on the seismic performance of CFRSST bridge piers under cyclic lateral loads,through a combination of experimental studies,finite element simulations and theoretical analyses,and the following conclusions were obtained:(1)Cyclic tests were conducted on two concrete-filled round-ended steel tubular pier specimens and four CFRSST specimens,including solid and hollow sections.The test results indicated that compared to specimens with ordinary outer steel tube,specimens with stainless steel tube had improved seismic behavior,with plumper hysteretic curves and better energy dissipation capacity,and the skeleton curve descended much slower after the peak.For CFRSST specimens,the lateral bearing capacities were obviously lower under weak-axis bending,compared to strong-axis bending,the lateral load decreased more rapidly after the peak point,and the ductility was obviously lower.Under strong-axis bending,the lateral bearing capacity,the ductility coefficient and the energy dissipation capacity of the CFRSST specimen with hollow section was higher than that with solid section,while under weak-axis bending,although the bearing capacity of the CFRSST specimen was still higher,the ductility coefficient was slightly lower,due to buckling of the flat portion of the inner steel tube.(2)Finite element models of the 6 test specimens were established using the finite element analysis software ABAQUS,and the numerical results were compared with the experimental results for model validation.Parametric studies were conducted on the influence of factors including the nominal yield strength of the outer steel tube,the yield strength of the inner steel tube,the thickness of the outer and inner steel tubes,the hollow section ratio,the core concrete strength,the slenderness ratio,the axial compression ratio,and the length-to-width ratio on the seismic behavior of hollow CFRSST bridge piers.The results showed that the nominal yield strength and the thickness of the outer steel tube,the slenderness ratio and the length-to-width ratio had a great influence on the lateral bearing capacity of the hollow piers;the yield strength and thickness of the inner steel tube and core concrete strength had little effect on the lateral bearing capacity of the hollow piers;when the axial compression ratio increased,the lateral bearing capacity of the hollow piers decreased slightly,but the skeleton curve descended much faster after the peak;with the increase of the hollow section ratio,the lateral bearing capacity of the hollow piers increased first and then decreased.(3)Based on the experimental and FEA analysis results,the restoring force model of CFRSST bridge piers was determined by data fitting.Load-displacement curves were proposed based on the restoring force model,and compared with the experimental results,which could provide a valuable reference for elastoplastic dynamic analyses on of this type of structure.