Overall stability design of T-shaped irregular concrete-filled steel tubular columns under axial compression

Abstract This paper presents investigations into the overall stability design of irregularly-shaped concrete-filled steel tubular columns with T-shape (T-ICFSTCs). The T-ICFSTC consists of I-steel, U-steel, and infilled concrete, forming a multi-cell steel tubular column. They are applied in the T-shaped sectional corner of the intersection between two walls in the residential buildings structures. The overall instability of the slender T-ICFSTCs may still be a significant concern in their strength design when they are placed in a higher spacing between two adjacent floors. This paper mainly focuses on establishing a design method for predicting the overall stability capacity of T-ICFSTCs subjected to axial load. Firstly, experimental investigations of an end-hinged T-ICFSTC and an end-fixed T-ICFSTC under axial load were carried out for checking its overall stability bearing capacity. Subsequently, the refined finite element (FE) model of the T-ICFSTCs is established and validated by the experimental results. In addition, the elastic buckling behavior of T-ICFSTC is studied by employing finite element (FE) eigenvalue buckling analysis, and the corresponding normalized slenderness ratio is obtained in the form of the Euler formula. Finally, based on the FE model validated experimentally, the parametric analyses of T-ICFSTCs are performed to investigate their overall stability capacities through changing the effects of steel ratio, sectional size, and material strength combination between concrete and steel. With these FE parametric analytic results, the overall stability coefficient φ, as well as φ-λ curves of T-ICFSTCs, are then obtained. These curves form the overall stability design formula of T-ICFSTCs loaded axially and apply in a common range of the percentage of load-carrying capacity shared by concrete. This design formula provides fundamentals to further develop a comprehensive design method of the T-ICFSTCs subjected to combined axial loads and moments.