Axial Compression Performance of Square Thin Walled Concrete-Filled Steel Tube Stub Columns with Reinforcement Stiffener under Constant High-Temperature

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.

Optimization of Artificial Intelligence System by Evolutionary Algorithm for Prediction of Axial Capacity of Rectangular Concrete Filled Steel Tubes under Compression

“…In terms of failure modality, local outward buckling failure of the external steel was observed in all specimens, as shown in Figure 2a. This is the same as that observed by other investigations such as Han and Yao [91], Lyu et al [97], Ding et al [98], and Yan et al [99]. Depending on the dimension of the cross section, the locations of the external folding of the steel tube are not the same.…”

“…Last, but not least, for all specimens, concrete in the core was damaged in most of specimens following a shear failure mode, as shown in Figure 2c [97,98]. Besides, the influence of temperature on the failure modality of stub CFST structural members could be referred to in Yan et al [99] (low temperature) and Lyu et al [97] (high temperature). Finally, Angelo et al [100] and Kulkarni et al [101] have tested and discussed about the failure of rectangular CFST structural members in junction with wide beam for earthquake engineering application.…”

“…However, the tensile fracture of the steel tube generally occurred after the peak load [98]. Last, but not least, for all specimens, concrete in the core was damaged in most of specimens following a shear failure mode, as shown in Figure 2c [97,98]. Besides, the influence of temperature on the failure modality of stub CFST structural members could be referred to in Yan et al [99] (low temperature) and Lyu et al [97] (high temperature).…”

“…Failure of rectangular CFST specimens: (a) local outward buckling of steel tube (reproduced with permission from Han[89]), (b) tensile fracture at the welding seam of steel tube (reproduced with permission from Ding et al[98]), (c) damage of concrete core (reproduced with permission from Lyu et al[97]). …”

Prediction of Ultimate Axial Capacity of Square Concrete-Filled Steel Tubular Short Columns Using a Hybrid Intelligent Algorithm

“…Tao et al [6] and Han et al [7] respectively established a finite element model considering material nonlinearity and interaction between concrete and steel tubular, and verified the model with experimental data. Lyu et al [8] analyzed the ultimate bearing capacity, failure mode, and load-displacement curve of square thin-walled CFST short columns with reinforcement stiffener at different temperatures using comparative experiments and ABAQUS simulation. Briefly, the ultimate axial capacity is an essential mechanical index to evaluate the performance of CFST columns under axial compression in both laboratory experiments and numerical simulations [9,10].…”