Precast prestressed concrete frames for seismically retrofitting existing RC frames

Abstract

A precast prestressed concrete frame system with mild press joints is introduced for the seismic retrofit of existing reinforced concrete frames. Cyclic loading tests are conducted on precast prestressed concrete and cast-in-situ reinforced concrete frame subassemblies to investigate the hysteretic behavior and damage characteristics of the frames. The test results demonstrate the damage-tolerance of precast frames in terms of well-controlled cracking and minimized residual drift compared to monolithic RC frames. A simplified numerical model is introduced to simulate the hysteretic behavior of mild press joints. The dynamic seismic response of a prototype building retrofitted by the proposed method is evaluated by numerical analysis. Two retrofit plans with different attached precast frames are compared. The results suggest that a partial retrofit of certain lower stories, which has been a common practice in Japan, may create drift concentration in the upper stories of a building.