The axial compressive behavior of stone-lightweight aggregate concrete-filled steel tubular stub columns

Abstract

To study the axial compressive mechanical properties of stone-lightweight aggregate concrete-filled steel tubular (SLACFST) stub columns, five circular stone-lightweight aggregate concrete-filled steel tubular (C-SLACFST) and square stone-lightweight aggregate concrete-filled steel tubular (S-SLACFST) stub columns were made by taking the volume replacement ratio of natural gravel aggregate and ceramsite in lightweight aggregate concrete as a variation parameter. After observing their mechanical process and failure modes, the axial load–displacement curves of the specimens were obtained. The influence of gravel replacement ratio on the energy dissipation and stiffness of the specimens was analyzed, and a simplified model for predicting their stiffness degradation was proposed. The plastic damage model was then used to verify those specimens with a finite element, and this model was subsequently adopted in the whole process analysis of these specimens and in finding out the loading relationship between the steel tube and core stone-lightweight aggregate concrete (SLAC). The effects of varying parameters on the compressive behavior of the specimens were investigated, and the extent to which these varying parameters are related to the ultimate bearing capacity of SLACFST was assessed via a grey correlation analysis. Results show that the rigidity of the calculated load–displacement curves in the elastic and elastic–plastic stages is greater than that of the test curves, but the ultimate bearing capacity and peak displacements agree with the test values within an acceptable error. Moreover, the simulated failure modes of the control specimens are the same as the test failure modes. Before reaching the ultimate bearing capacity, the core SLAC made a significant contribution to the bearing capacity of the specimen due to the constraint of steel tube. The negligible influence of gravel replacement ratio on the ultimate bearing capacity of SLACFST specimen. In addition, the nature gravel can inhibit the floating of LAC to a certain extent, so as to achieve the purpose of using SLAC to make SLACFST, reducing the self-weight of the structure while having higher bearing capacity.