Abstract
Concrete encased steel composite columns have been widely used in high-rise buildings and top-down constructions owning to excellent load-carrying capacity and fire resistance. However, double symmetric composite section is rarely achieved due to the off-center eccentricity of steel kingpost, which is a common problem in top-down constructions. EN1994-1-1 (EC4) simplified method does not provide any explicit provisions for this kind of irregular composite columns, and many designers address this issue by reducing it into a symmetrical cross-section for ease of simple calculation. This paper presents a general method based on nonlinear finite element modelling software ABAQUS to analyze the ultimate strength behavior of concrete-encased composite columns with asymmetrically placed steel section. The accuracy of the FE model is verified against existing test results. Parametric study is performed to further investigate the influence of steel section eccentricity on ultimate strength of stub columns under different loading conditions. A simplified method based on modification of EC4 design approach is developed to construct the moment-axial force interaction diagram. Accuracy of the proposed method is assessed by comparing the analytically predicted results with the numerical results. It is found that the proposed method can be adopted as a useful tool to predict the cross-section resistance of non-symmetrical concrete-encased steel composite columns.
Highlights
Concrete-encased steel composite columns gains increasingly popularity in top-down construction owing to its excellent load-carrying capacity
Following the stipulation specified in various design codes, including Eurocode 4 [4] and American code AISC 360-10 [5], the majority of experimental study focused on columns with steel section positioned exactly at the geometrical centroid of the overall cross-section
This paper present nonlinear Finite Element Analysis (FEA) on normal strength concreteencased steel composite columns with off-center steel section, of which the load-carrying capacity is comprehensively analyzed by varying the load eccentricity and the encased steel section
Summary
Concrete-encased steel composite columns gains increasingly popularity in top-down construction owing to its excellent load-carrying capacity. Chiorean [7] proposed an incremental-iterative procedure to predict interaction diagram and moment capacity contours for arbitrarily-shaped composite crosssections. Chan et al [8] developed a graphically interactive computer program capable of performing cross-section analysis and secondorder analysis using PEP element. This paper present nonlinear Finite Element Analysis (FEA) on normal strength concreteencased steel composite columns with off-center steel section, of which the load-carrying capacity is comprehensively analyzed by varying the load eccentricity and the encased steel section. A simplified design method is proposed to predict cross-sectional strength based on modification of EC4 plastic design approach, and verification of the proposed method is conducted by comparing with FEA result and numerical procedure developed by Chan et al [8]
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