Research on seismic performance of thin-walled stirrup-confined rectangular concrete filled steel tube piers
Compared to circular concrete filled steel tube(CFST)piers,rectangular CFST piers have a larger moment of inertia and stronger stability but have poor constraints on filling concrete.To investigate the influences of end stirrup and loading direction on improving the seismic performance of rectangular CFST piers,quasi-static tests were conducted on two square and two rectangular CFST piers.The study analyzed and compared the effects of end stirrup and loading direction on the bridge piers'stiffness,bearing capacity,energy dissipation,stiffness degradation,and residual deformation.Additionally,a refined three-dimensional solid-shell finite element model of the stirrup CFST piers was established using ABAQUS software,where cracks were introduced in the concrete elements,and ductile damage was introduced in the steel tube elements to consider more accurate degradation patterns of the seismic performance of CFST piers.The research results showed that compared to traditional CFST piers,end stirrup increased the yield load,horizontal peak load,cumulative energy dissipation,and elastic stiffness of restrained steel tube concrete piers by 49.3%,42.8%,24.1%,and 15.1%,respectively,indicating better seismic performance than traditional CFST piers.Compared to weak axis loading,strong axis loading increased the yield load,peak load,cumulative energy dissipation,and elastic stiffness of the piers by 45.1%,44.9%,51.7%,and 7.1%,respectively,indicating that the seismic performance is more effectively utilized under strong axis loading.The refined three-dimensional solid-shell finite element model of the CFST piers established using ABAQUS software showed good agreement with the experimental results and reasonably reflected the"pinching"effect of the hysteresis curve and the degradation of load-carrying capacity during the plastic large deformation stage of the stirrup steel tube concrete piers under cyclic loading.The crack height positions calculated by the finite element model were consistent with the experimental results.The research results provide a reference for further optimizing the design of CFST piers.
stirrupconcrete-filled steel tubepiersseismic performancefinite element analysis
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