ABSTRACT
There are a number of uniaxial constitutive material models available in the literature that can be used for developing FBE models for circular CFST columns (Susantha et al., 2001; Sakino et al., 2004; Han et al., 2005 and Liang & Fragomeni, 2009) and for square or rectangular CFST columns (Varma et al., 2005 and Thai et al., 2015). However, the majority of those models are empirical models and have various limitations. For example, the material models proposed by Sakino et al. (2004) gives reasonable predictions but the proposed concrete model cannot accurately predict the residual strength of concrete especially for CFST columns with Ultra-High Strength Concrete (UHSC). To ensure a safe design, the residual resistance is one of the most important factors to be considered (Liew et al., 2014). Moreover, elastic-plastic steel model was used in Sakino et al. (2004) which can-
1 INTRODUCTION
Concrete-Filled Steel Tubular (CFST) columns have been widely used in modern construction throughout the world owing to their excellent performance provided by the composite action between the steel tube and concrete. Extensive research over the last five decades on composite columns has generated numerous results to understand the behaviour of such columns as summarised by Shanmugam and Lakshmi (2001) and Han et al. (2014).
