Pushover Experiment on Retrofit of School Buildings by Adding Composite Columns to Partition Brick Walls

Pushover Experiment on Retrofit of School Buildings by Adding Composite Columns to Partition Brick Walls

Thousands of buildings were damaged by the devastated 921 Chi-Chi earthquake. School buildings are the most vulnerable category in public buildings and the retrofit of existing school buildings becomes a stringent issue. In addition to cost effectiveness, the impact of retrofit methods on the functions of the school buildings has to be considered. Therefore, retrofit of school buildings by adding composite columns onto the partition brick walls is proposed in this research. Composite column is divided into two parts and added to the two sides of the partition brick wall with stirrups. The composite column itself will contribute to the seismic capacity of the school building. Moreover, the effective width of the partition brick wall is decreased. Thus, both the out-of-plane strength and the bearing capacity of the partition brick wall are enhanced. For the retrofit onto the partition brick walls, no windows or doors along the corridor have to be removed so that the proposed method is cost effective and the impact on the functions of the buildings is minimized. Based on the frame with partition brick wall of a school building, two full-scale single-story specimens with slabs were designed and fabricated. They were frame with pre-layered brick wall(B1-2); frame with pre-layered brick wall retrofitted by adding composite column(B1-2-C). Reinforced concrete blocks were mounted on the slabs of the specimens to simulate the gravity loading of two stories. In addition, through the L-shaped testing frame, reinforced concrete columns were deformed with double curvatures during cyclic loading tests in order to study the seismic behavior of the school buildings. According to the experimental results, the feasibility of the proposed retrofit method was successfully verified. The strength after retrofit was doubled. When the drift ratio was 15%, the residual strength after retrofit was as high as the maximum strength before retrofit. Nonlinear pushover analysis was also conducted. Good agreement between experimental and analytical results were achieved.