Masayoshi Nakashima

Japanese Approaches to Repairability and Recovery of Building Structures Subjected to Strong Ground Shaking

Japan has experienced numerous earthquake disasters over the centuries and has accumulated extensive knowledge and developed a wide range of measures related to repairability in the design and construction of buildings and infrastructure, as well as in post-earthquake recovery of damaged facilities. This presentation focuses on buildings and discusses several aspects of repairability and recovery that have already been implemented in actual practice, rather than remaining as concepts for future application. The highlighted points are as follows:

Densely deployed strong-motion seismograph network: Several thousand seismographs have been installed across the country, and their data are used to characterize design ground motions. These data also form the basis of Japan’s nationwide earthquake early warning system.

Seismic design strategies aimed at maximizing repairability: Although not mandatory, recent practice (since the mid-2000s) has shifted toward ensuring elastic behavior under the Japanese Level 2 seismic load (corresponding to an approximate return period of 500 years) by incorporating energy-dissipation devices.

Increased attention to nonstructural damage: The significant life inconvenience and business disruptions caused by nonstructural damage in major earthquakes during the 2000s have heightened awareness of the need to prevent such damage.

Building monitoring: Although optional and market-driven, the installation of sensors, continuous monitoring, and immediate post-earthquake damage assessment are becoming increasingly common, particularly for large buildings.

Owner–constructor partnerships during emergencies: A notable feature in Japan is the very short time between the occurrence of earthquake damage and the dispatch of inspection or repair teams. This rapid response is supported by the Japanese business practice of long-term relationships between building owners and constructors.