Numerical simulation and parametric studies on the behaviour of concrete sandwiched double steel tubular stub columns

Abstract

Concrete Filled Steel Tubular section (CFST) is found to possess high strength and stiffness properties and has been popularized in high-rise building projects. Nowadays, several alterations are made within this section to improve its structural performance at design as well as at the constructional level. Concrete Sandwiched Double Steel Tube (CSDST) is one such configuration that provides improved fire resistance, impact resistance and efficient connection detailing, in addition to high strength, stiffness and ductility properties. Since experimental investigations become very expensive to study the various parameters influencing their behavioural aspects, numerical techniques are adopted in recent studies. Even though numerical simulations bring ease in performing parametric studies, a well-established theoretical background is needed to correctly interpret its output data. In this study, a numerical model is developed for two types of sandwiched tubes, namely, circular inner and circular outer steel tubes (CSDST CC), and square inner and circular outer steel tubes (CSDST-CS), using ABAQUS software. Here, the concrete confinement equation proposed by the author for CSDST cross-section based on thick-walled cylinder theory is used for defining the concrete material model. The numerical model developed is validated with the experimental results available for CSDST stub columns. Further, a parametric study is conducted to find the limitations on the proposed concrete confining stress. The proposed equation is found to be valid for a wide range of hollowness ratio of the cross-section with compact (class-1) outer steel tubes.