Design considerations for a base-isolated demonstration building

A base-isolated demonstration building (BIDB) was built in Indonesia as part of an ongoing effort by the United Nations Industrial Development Organization to promote the use of base isolation technology for common structures in earthquake-prone developing countries. The superstructure of the demonstration building is a four-story reinforced concrete frame with masonry infill walls, designed in accordance with the Indonesian Seismic Code. A specially developed isolation system for this project consisted of 16 high-damping natural rubber bearings, which were connected to the columns and foundation using recessed-type connections at the ground level. The seismic isolation provisions from the 1994 Uniform Building Code were adapted to complement the Indonesian Seismic Code requirements for this project, and site-specific spectra were developed and used for the design of the isolation system. This paper discusses the design considerations for the base-isolated demonstration building, the design and testing of the bearings and the cost-effectiveness of the isolation system. The seismic performance of the base-isolated building is discussed in the companion paper. It is expected that this newly developed isolation system, designed specifically for low-axial pressure applications, can be adopted for the earthquake protection of a variety of smaller public buildings-such as housing, schools, and hospitals-in developing countries.