Abstract

Many commercial and residential mixed buildings collapsed in 1999 Chi-Chi Earthquake due to the soft and weak bottom story.In the traditional mixed buildings,the open area,such as shop stores and living rooms,were designed on the ground floor,however,the private area,such as residential bedrooms and bathrooms were usually designed on the upper floors.The open area is usually few partition walls,however,the private area needs lots of partition walls.Therefore,the structural system with soft and weak bottom story is a significant problem of the traditional mixed buildings.

Rebuild and seismic retrofit of the existing mixed buildings always has a big challenge because it is very difficult to come out with agreement from the multi-owners of the buildings.However,the occurrence of earthquakes is unpredictable,the seismic capacity of existing buildings should be improved as soon as possible.Therefore,seismic retrofitting in stages may be a feasible strategy[1].The study proposed the seismic retrofit in stages can implement retrofit in the public area without affect into private area.That may be easier to come out with agreement of whole multi-owners.The proposed seismic retrofit in stages aims to improve the problem of soft and weak bottom story.The first phase of retrofit aims to reduce the collapsed probability of the buildings although that may not satisfy the seismic performance of the current seismic design code.The final phase shall still implement retrofit of whole buildings which can satisfy the seismic performance of the current seismic design code.This paper introduces a design procedure of the seismic retrofitting in stages for the existing reinforced concrete buildings with soft and weak bottom story.Moreover,a design example will be provided[2].