Comparing the seismic performance of concentrically braced frames with and without self-centering behaviour

Conventional concentrically braced frames (CBFs) are designed to provide lateral resistance to earthquake loading through axial resistance of the brace member, as well as providing energy dissipation during earthquake loading through tensile yielding and inelastic buckling of its bracing members. These cycles of inelastic deformation lead to the possibility of residual deformations being present in a structure that has been designed to current seismic code provisions. This paper presents a new self-centering concentrically braced frame (SC-CBF) where a conventional CBF is combined with a post-tensioning (PT) arrangement to give a system that will self-center after earthquake loading. The behaviour and layout of the SC-CBF is first described, followed by the numerical model used to analyse the performance of the system. An example SC-CBF is then designed for a set of performance goals, and their performance is analysed using a suite of design spectrum compatible ground motions. The same structure is then designed using a conventional CBF lateral resisting system and a similar analysis is carried out. The results of the two systems are then compared to show the benefits of using a SC-CBF over a conventional CBF.