Reconstruction of the Shuri Castle: Resilient Structure Design and Use of Local Timber Material

Abstract

On October 31, 2019, people in Okinawa were shocked by the fire of the Shuri Castle. The reason for the fire is still unknown, but the reconstruction project started as a national project with many people hoping to build a better Shuri Castle. In fact, the Shuri Castle had been destroyed by fires several times, and the last Shuri Castle, which burned down in 2019, was built in 1980 after the destruction during WWII. As the spiritual symbol of the Okinawan people, the Shuri Castle reconstruction project was started in 2020, considering viewpoints of increasing its seismic resilience and using local timber materials, which were not included fully in the last construction. The policy for seismic reinforcement is limited because the Shuri Castle is a cultural building, therefore, specific guidelines were considered. For this new reconstruction, an earthquake of five hundred years of probable occurrence and wind speeds of 64 m/sec for a typhoon were regarded as highly safer structural calculations. Some structural elements of the main structure were designed to use local timber as it was in a long time in the past. However, since these local timbers, such as Okinawa-urajirogashi and Inumai, are rare nowadays, their material strengths are not standardized in the national timber standards. Therefore, an experimental program must verify that they are strong enough and can be used as structural elements in this reconstruction. The keynote will introduce some aspects of structural resilience and the material test methodology.