10.28: Fire performance of concrete filled steel tubular columns with built‐in stirrups

Abstract

Two concrete filled steel tubular columns with built-in stirrups (i.e., Specimens 1 and 2) and one control column (i.e., concrete filled steel tubular column without built-in stirrups, Specimen 3) were exposed to the ISO834 standard fire, and fire behaviors of the three columns were investigated and compared with each other. The steel usage of Specimen 1 (2) (i.e., total weight of the steel tube and stirrups) was the same as that of Specimen 3 (i.e., weight of the steel tube). The distance between the stirrup's centerline and inner surface of the steel tube was 20mm for Specimen 1, and 50mm for Specimen 2. The height and outer diameter of all the three columns were, respectively, 3800mm and 320mm. The axial load applied to Specimens 1 and 2 was identical with that applied to Specimen 3. Test results show that when the steel usage keeps unchanged, the fire endurance of the concrete filled steel tubular column with built-in stirrups is much longer than that of the column without built-in stirrups. Finally, a finite element analysis (FEA) model was developed and verified against the experimental results, and a parametric study has been preliminarily performed to reveal the fire performance of the concrete filled steel tubular columns with built-in stirrups.Keywords: concrete filled steel tube, fire performance, built-in stirrup 2 EXPERIMENTAL PROGRAM Specimen preparation and material propertiesSchematic diagrams of two CFST columns with built-in stirrups (Specimen 1 and Specimen 2) and one conventional CFST column (Specimen 3, control specimen) are shown in Fig. 1. All the three