Abstract
Holes are always opened in the steel tubes during the inspection and revision of initial concrete imperfections in concrete filled steel tubular (CFST) columns. The structural performance of such composite columns with holes may have obvious differences in comparison with normal CFST members. This paper intends to investigate the influences of sectional type, holes location, holes size, and holes depth on CFST stub columns. The typical failure modes, load-deformation responses, the ultimate strength, and ductility were discussed in detail. A total of twenty-eight specimens, twenty CFST columns with holes, four intact CFST specimens, and four reference hollow steel tubes subjected to axial compressive loading, were tested. The experimental results were compared with predictions of Eurocode 4 and finite element analysis. An empirical equation for predicting the ultimate strength of CFST stub columns with holes was proposed.
Highlights
Concrete filled steel tubular (CFST) columns have been widely used in engineering structures, such as high-rise buildings, arch bridges, and high transmission towers
Failure Modes. e typical failure appearances of CFST columns with holes are shown in Figure 3, which indicate that CFST columns with holes demonstrated a different failure mode compared to the intact column
Deformations were initiated from the area around holes, and the cracking of steel tube could be observed and developed accompanied with outward buckling near hole. e effect of holes size on buckling and failure mode was not considerable for the specimens with holes
Summary
Concrete filled steel tubular (CFST) columns have been widely used in engineering structures, such as high-rise buildings, arch bridges, and high transmission towers. Ghanbari Ghazijahani et al [8] examined the effect of different types of dent imperfections on the plastic buckling capacity and the failure modes of short steel tubes under axial compression. Compared with the extensive studies carried out on metal shells or hollow tubes with geometric imperfections, very limited research has been conducted on the CFST composite members with notch or dent imperfections in the steel tubes. Tao et al [9] introduced a function with the shape of initial geometric imperfections for steel plates into numerical model to calculate the ultimate strength of CFST stub columns. Yu et al [10] investigated the effects of concrete strength, notched holes, or full-perimeter notched slots of the steel tube and different loading conditions on the ultimate capacity and the load-deformation behavior of the concrete filled steel tube (CFST) stub columns. Tao et al [12] presented a photogrammetric method to capture the initial imperfections of concrete filled stainless-steel tubular (CFSST) columns in fire and after fire exposure. ey developed a three-dimensional finite element (FE) model of CFSST columns and introduced an amplification factor to consider the initial geometric imperfection as the first buckling mode shape of the column
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