Seismic retrofitting of a historic building by using an isolation system with a weak restoring force

Abstract

Historic buildings and cultural relics are valuable and must be preserved carefully. However, such structures may be destroyed during earthquakes owing to the deterioration of their structural performance over time. Therefore, retrofitting protection measures must be adopted. The typical structural style of ancient buildings in China and East Asia involves timber structures. Due to the diversity of the construction environment, the site conditions of such buildings are often unfavorable. Moreover, several important cultural relics in historic buildings exhibit low integrity, and therefore the primary structure must not be influenced during retrofitting. To overcome these problems, this paper proposes the use of an isolation system with a weak restoring force and post-earthquake recentering capacity. The proposed isolation system consists of elastic sliding bearings, laminated rubber bearings, viscous dampers and jack reaction joints. To better isolate lightweight structures under soft soil conditions, the stiffness of the isolation layer must be designed to have a low value, and therefore, the self-recentering ability cannot be realized. Thus, in this work, jack reaction joints were used to recenter the structure after a rare earthquake. Moreover, a performance index was introduced that is suitable for the seismic isolation protection of typical East Asian historic buildings. The proposed isolation system was applied to a famous historic timber building in Shanghai, namely, the Yufo temple, to improve the seismic performance of the translocated structure and nonstructural members. The underpinning system of translocation facilitates the use of the isolation system. The analysis results indicate that the proposed isolation method can help improve the performance of the structure involving both historic buildings and cultural relics and that the superstructure remains unaffected by the reinforcement measures. In addition, this approach can provide guidance for the protection of other cultural historical buildings that have different styles.