Abstract
This study investigated the axial compressive performance of six thin-walled concrete-filled steel tube (CFST) square column specimens with steel bar stiffeners and two non-stiffened specimens at constant temperatures of 20 °C, 100 °C, 200 °C, 400 °C, 600 °C and 800 °C. The mechanical properties of the specimens at different temperatures were analyzed in terms of the ultimate bearing capacity, failure mode, and load–displacement curve. The experiment results show that at high temperature, even though the mechanical properties of the specimens declined, leading to a decrease of the ultimate bearing capacity, the ductility and deformation capacity of the specimens improved inversely. Based on finite element software ABAQUS, numerical models were developed to calculate both temperature and mechanical fields, the results of which were in good agreement with experimental results. Then, the stress mechanism of eight specimens was analyzed using established numerical models. The analysis results show that with the increase of temperature, the longitudinal stress gradient of the concrete in the specimen column increases while the stress value decreases. The lateral restraint of the stiffeners is capable of restraining the steel outer buckling and enhancing the restraint effect on the concrete.
Highlights
The thin-walled concrete-filled steel tubular (CFST) column is designed based on the generalCFST column [1,2,3], in which the thickness of the steel tube is reduced
It can be seen that the steel tubes exhibit buckling after the tests of high-temperature 20–200 ◦ C
The buckling curvatures of the steel tube are in the middle of the column and the adjacent areas, the locations of which are not the same on different sides
Summary
The thin-walled concrete-filled steel tubular (CFST) column is designed based on the general. Because of the unevenly and weaker confinement, CFST columns with a square cross-section have a relatively smaller bearing capacity and ductility, while the steel tube is more prone to buckling [5,6]. To improve the mechanical properties of square or rectangular CFST columns, the key issue is to increase the constraint of the steel tube on concrete. The results showed that these enhanced measures can delay the buckling of steel tubes and improve the bearing capacity and ductility of the columns. This paper studies the mechanical properties of thin-walled square steel tubular concrete columns under high temperature via both experimental and numerical investigations. The outcome of this research is capable of providing a guide for the design of such a kind of component in practical engineering and post-disaster restoration
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