EXPERIMENTAL STUDY AND FINITE ELEMENT ANALYSIS ON AXIAL COMPRESSION PERFORMANCE OF HIGH STRENGTH STEEL REINFORCED ULTRA-HIGH PERFORMANCE CONCRETE SHORT COLUMN

In order to study the axial compressive performance of high strength steel reinforced ultra-high performance concrete (HSSRUHPC) short columns, axial compressive loading tests were carried out on specimens. The design parameters included steel ratio, stirrup spacing and stirrup form. The failure process of specimens under axial compression was observed, and the failure patterns and the axial load-displacement curves were obtained. The axial compression performance indexes such as bearing capacity, deformation capacity and stiffness, and the law of strain development of UHPC, of longitudinal reinforcement, of stirrup and of steel were analyzed. Based on experimental study, the finite element analysis models of axial compression performance for HSSRUHPC short columns were established by using Abaqus, and the calculation results agreed well with the test results. And then the parametric analysis was carried out. The results showed that the typical axial compression failure occurred for all specimens, and serrated cracks appeared at the surface of middle part. There are two peak values of load in the axial load-displacement curves. With the stirrup spacing decreasing, the bearing capacity and deformation capacity were both improved, but there was no obvious change in stiffness degradation rate. With the steel ratio increasing, the bearing capacity increased, the deformation capacity increased first and then decreased, and the stiffness degradation was slowed. With the strength of steel increasing, the bearing capacity and deformation capacity both increased, and the increase rate was fast first and then slow. With the compression strength of UHPC increasing, the bearing capacity was improved, but the deformation capacity got worse. The strain of UHPC could reach the tensile peak value and the longitudinal reinforcements yielded by compression before the ultimate point. The tensile strain of stirrups was smaller than one-third of the yield strain at the ultimate point but could reach the yield strain before the failure point. The flange of steel yielded by compression near the ultimate point, and the web yielded later than the flange.