Behaviour and design calculations of recycled aggregate concrete-filled steel tube (RACFST) members

Abstract

This paper describes research work on the performance and design calculations of recycled aggregate concrete filled steel tube (RACFST) members, especially the most recent developments in China. Firstly, experimental studies on RACFST members subjected to short-term static loading, long-term sustained loading and cyclic flexural loading are summarised and analysed, and recent advances in the behaviour of RACFST stub columns after exposure to high temperatures (300–800°C) are also reviewed. The experimental results show that, in general, RACFST members have similar performance to concrete filled steel tube (CFST) members when subjected to the same loading conditions. However, due to the more serious inherent defects of recycled aggregate concrete compared with normal concrete, RACFST members have a lower bearing capacity and stiffness than their CFST counterparts. Secondly, design formulae for RACFST members are suggested and the calculated bearing capacities using the simplified equations generally agree well with the experimental results. Finally, the potential research needs of RACFST structures are discussed.