This article presents an experimental study to investigate the strength of steel‐reinforced concrete‐filled steel tubular (SRCFT) columns reinforced with castellated and common cruciform steel columns under compressive axial load. SRCFT columns are constructed by embedding a reinforcing steel section into the concrete‐filled steel tube (CFT) column, and in this article, a new structural steel shape, namely castellated cruciform steel section, for reinforcing of SRCFT columns was designed. Investigation of SRCFT columns reinforced with castellated steel section indicates evidence of higher strength and applicability in comparison with common reinforcing steel section. A numerical investigation was also carried out with finite element analysis to study the structural behavior of SRCFT columns under lateral cyclic loading. A reasonable agreement was obtained between the results of finite element analysis and the experimental test under axial and lateral cyclic loading. The variables studied included the effect of various types of reinforcing steel sections, flange boost effects of castellated reinforcing steel section, length of columns, compressive strength of concrete, and the tube thickness. As a result, it was revealed that the SRCFT specimen reinforced with castellated cruciform steel sections was effective in enhancing the seismic performance toward more stable hysteresis curves, lower strength degradation, and higher energy dissipation as compared with SRCFT specimens reinforced with common cruciform steel sections.
SRCFT columns are formed by inserting a steel section into a concrete-filled steel tube. These types of columns are named steel-reinforced concrete-filled steel tubular (SRCFT) columns. The current study aims at investigating the various types of reinforcing steel section to improve the strength and hysteresis behavior of SRCFT columns under axial and lateral cyclic loading. To attain this objective, a numerical study has been conducted on a series of composite columns. First, FEM procedure has been verified by the use of available experimental studies. Next, eight composite columns having different types of cross sections were analyzed. For comparison purpose, the base model was a CFT column used as a benchmark specimen. Nevertheless, the other specimens were SRCFT types. The results indicate that reinforcement of a CFT column through this method leads to enhancement in load-carrying capacity, enhancement in lateral drift ratio, ductility, preventing of local buckling in steel shell, and enhancement in energy absorption capacity. Under cyclic displacement history, it was observed that the use of cross-shaped reinforcing steel section causes a higher level of energy dissipation and the moment of inertia of the reinforcing steel sections was found to be the most significant parameter affecting the hysteresis behavior of SRCFT columns.
Purpose The primary purpose of this research was to expand the knowledge base regarding the behavior of steel columns during exposure to fire. This paper presents the numerical study of the effect of heat on the performance of parking steel column in a seven-story steel building under cyclic loading. Design/methodology/approach In this research, the forces and deformations developed during a fire are estimated by using detailed 3D finite-element models. The analyses are in the form of a coupled thermo-mechanical analysis in two types of loading: concurrent loading (fire and cyclic loading) and non-concurrent loading (first fire and then cyclically), and the analyses have been conducted in both states of the fire loading with cooling and without cooling using the ABAQUS software. Further, it was investigated whether, during the fire loading, the specimen was protected by a 3-cm-thick concrete coating and how much it changes the seismic performance. After verification of the specimen with the experimental test results, the column model was investigated under different loading conditions. Findings The result of analyses indicates that the effect of thermal damage on the performance of steel columns, when cooling is happening late, is more than the state in which cooling occurs immediately after the fire. In this paper, thermal–seismic performance of parking steel columns has been specified and the effect of the fire damage has been investigated for the protected steel by concrete coating and to the non-protected steel, under both cooling and non-cooling states. Originality/value This study led to recommendations based on the findings and suggestions for additional work to support performance-based fire engineering. It is clear that predicting force and deformation on steel column during fire is complex and it is affected by many variables. Here in this paper, those variables are examined and proper results have been achieved.
Based on some findings on the two kinds of Concrete Filled Double Skin steel Tube (CFDST) members with circular or square sections, a new kind of CFDST with octagonal and polygonal section have been investigated under axial and cyclic loading. For this purpose, the outer steel wall has various steel shapes and the inner steel wall is the same as circular section and for some part of analyses, the outer tube is the same as circular section and the inner wall has various steel sections. Primarily, FEM procedure has been verified with some available experimental studies and then, seven composite columns with different section types have been analyzed. The results of analyses exhibited the increase in strength and improvement in hysteresis behavior of the proposed steel sections under cyclic loading.
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