Analysis of large plastic deformation of concrete-filled steel tube pier under cyclic loading

Concrete filled steel tube (CFST) pier has the advantages of large bending rigidity, high bearing capacity, small floor area and strong energy dissipation. It has been widely used in urban viaduct. In order to achieve accurate simulation of the impact of steel ductile damage and concrete cracking on the seismic performance of CFST piers under low-cycle reciprocating loads, firstly, the uniaxial tensile tests of domestic Q235, Q345 and Q420 steel was carried out. A parametric deterministic ductile damage model considering the effect of yield strength was proposed. A parametric deterministic combined hardening-ductile damage model was formed. Then, the ABAQUS software was used to the combined hardening-ductile damage model of steel and the triaxial plastic-damage model of concrete, and the horizontal crack insertion technology was adopted to optimize the pier model in the concrete solid element, so as to establish the fine finite element model of CFST pier under low cyclic load. According to the hysteresis curves and buckling patterns of five circular CFST piers and five square CFST piers under unidirectional cyclic loading and two circular CFST piers under bidirectional cyclic loading, the rationality and validity of the fine finite element model were verified. The analysis results show that the solid-shell fine finite element plastic seismic calculation method of CFST pier considering the influence of horizontal cracks and steel ductile damage reasonably reflects the “pinch” effect of hysteretic curve of CFST piers under unidirectional and bidirectional cyclic load and the degradation of bearing capacity in plastic large deformation stage. It can reflect the law of interface slip and restraint of CFST pier. © 2023, Central South University Press. All rights reserved.