Seismic retrofit of a structure using self-centring precast concrete frames with enlarged beam ends

This research proposes a procedure to retrofit existing structures using self-centring post-tensioned precast concrete (SC-PC) frames. The procedure utilises the initial stiffness of the un-retrofitted structure and predicts the required initial stiffness of the retrofitted one using the N2 method. A modified precast beam-end shape is proposed to double the re-centring moment capacity of the retrofit frame at the beam-column interface. Different retrofit cases for two-and three-dimensional structures utilising the proposed and conventional PC beams are investigated. The results of the proposed procedure are verified through non-linear time history analysis using two different sets of earthquake records compatible with the design-level response spectrum. The study results reveal that the SC-PC retrofit frames are quite effective in controlling the earthquake-induced storey drift of the retrofitted structures while eliminating the residual storey drift. The results also indicate the effectiveness of the proposed beam shape in mitigating the inter-storey drift demand of the analysis model structures.