Seismic Retrofitting Initiatives

2022/01/31

Image: Conceptual diagram of the seismic isolation retrofit method for the Old University Library (constructing a seismic isolation layer beneath the building)

On January 17, 1995 (Heisei 7), the Great Hanshin-Awaji Earthquake occurred, and the "Act on Promotion of Seismic Renovation of Buildings" was enacted that same year. Socially, efforts toward seismic retrofitting began to accelerate from this year onward.

In 1995 and 1996, Keio University conducted seismic evaluations on approximately 100 buildings, including school buildings and hospitals used by students and the general public, focusing on those built before 1981 when the new seismic standards were established. The results showed that half of the buildings owned by Keio University were seismically inadequate. At the time, many of Keio's buildings had been constructed in the 1950s and 1960s under old structural standards, and the executive board felt a sense of crisis. Since facility maintenance cannot be achieved overnight, the university has been continuously working on seismic measures ever since. The "seismic retrofitting rate" refers to the percentage of seismically sound buildings among those owned, excluding machine rooms/warehouses without living space, buildings under 200 square meters, and unused buildings.

While seismic initiatives involve seismic reinforcement, we are also moving forward with the reconstruction of the buildings themselves.

In earnest, starting from 2004, seismic reinforcement of major university and affiliated schools' buildings was carried out intensively over four years. For the 150th anniversary in 2008, many buildings were reconstructed as part of commemorative projects. While reconstruction is done for purposes such as updating aging buildings, realizing new education and research, and improving the facility environment, it also serves to resolve seismic issues. For new buildings, large-scale structures are designed with seismic isolation, and we aim to adopt designs with superior safety and structural integrity compared to general buildings. Following the Great East Japan Earthquake in 2011, we have been planning even more robust buildings.

Work on hospital facilities, which were considered the most difficult, began sequentially in 2011 with the seismic reinforcement of existing wings. With the completion of Building 1 in 2018, the seismic retrofitting of the hospital was finished.

As a result, the seismic retrofitting rate at Keio gradually increased, exceeding 70% in 2006, 80% in 2008, and 90% in 2012. Since then, seismic retrofitting has been gradually progressing for small-scale buildings, infrequently used buildings, and those in remote locations.

The final major project was the seismic retrofitting of the Old University Library. It is an Important Cultural Property, a brick building with the unique conditions of a Meiji-era structure. We adopted the seismic isolation retrofit method and also performed preservation repairs. The renovation work took two years and two months and was completed in May 2019.

Seismic retrofitting initiatives involve significant costs and often require construction under difficult conditions. In this way, the seismic retrofitting rate, which was 50% in 1995, finally reached 100% in 2020 after a quarter-century of effort by those involved.

(Hiroshi Watanabe, Office of Facilities and Property Management)