Seismic Isolation Retrofit of a Medical Complex by Integrating Two Large-Scale Buildings

Abstract

We developed a methodology of seismic isolation retrofit integrating adjacent buildings using prestressed concrete slabs, and applied it to two large-scale buildings in Hamamatsu City in Shizuoka Prefecture in Japan. It is the first seismic isolation retrofit of hospital in Japan. The two steel-reinforced concrete buildings were nine stories high with one basement, and had been constructed in 1973 and 1975 based on an old structural design code. The two buildings were integrated into one building by connecting individual floors using post-tensioned prestressing cables through slabs. A comparison of microtremors before and after the integration confirmed that the integration worked well. Seismic isolation devices were set up mainly in basement columns using temporary support involving steel brackets and prestressing cables to install devices safely and economically (Masuzawa et al., 2004 [1]). In the seismic design phase, broadband-generated earthquake ground motions for a hypothetical Magnitude 8 earthquake near the site were simulated using a hybrid method (Hisada, 2000 [2], etc.). Safety and functionality were verified by evaluating structural seismic performance based on time-history seismic response analysis.