Seismic Analysis for School Building Retrofitted by Reinforced Concrete External Frames

The retrofit methods of school buildings in Taiwan include RC jacketing, wing wall and shear wall etc. However, the school buildings are effected during the construction by those methods. In this paper, we use the method of adding RC external frames where RC slab is used to transfer the shear force between existing building and external frames. In this method, the school buildings are not effected during the construction. So it can decrease the cost. We use the seismic preliminary evaluation, simplified pushover analysis and detailed evaluation to evaluate the seismic performance of the school buildings without and with retrofit. Taking a typical unit of a two-story school building with two classrooms in each floor, from the seismic preliminary evaluation of school building with RC jacketing, the preliminary evaluation of school building with RC external frame is established. So we can use this method to do the preliminary design of school building with RC external frame and check the rationality of school building that has already been retrofitted with RC external frame. Then we use the software ETABS to do the nonlinear static pushover. We can get the capacity curve and the performance peak ground acceleration curve. From the results of pushover analysis, we can use the shear demand formula of the retrofitting slab that we establish in this paper to calculate the shear demand of the retrofitting slab. Then we use the shear formula from Concrete Engineering Design Specification and Commentary as the shear capacity formula of the retrofitting slab. And we can understand the design of retrofitting slab is reasonable. Finally we establish a complete retrofit design process, and we use a full school building structure to verify the rationality of the process. The process can provide the retrofit design suggestion to engineers.