Enhancing the seismic performance of Dou-Gon systems in traditional timber structures

Traditional timber structures such as temples, traditional palace halls and estates that widely distributed in mainland China, Japan, Taiwan and various other regions of Asia are suffering from earthquakes. However, the research efforts have been scarcely seen on the techniques for enhancing the seismic performance of historic timber buildings with the Dou-Gon system. This study developed a technique to enhance the seismic performance of traditional timber buildings with the Dou-Gon system. High-strength steel bars and super-elastic alloy bars are used in this study to substitute conventional Dou-Gon system that uses wooden pegs to connect Dou and the lower structure. In this thesis, the material characterisation of super-elastic alloy is studied by the axial quasi- static loading and dynamic cyclic loading. The results of experiments found that the Cu-Al-Mn super-elastic alloy has a great damping capacity and exceptional recentring capability. The cyclic results demonstrate that the equivalent damping ratio increases with the increase of the loading frequency. Pre-straining of the super-elastic alloy showed a better damping effect compare to the non-prestrained super-elastic alloy. However, when the self-heating temperature becomes the primary governing factor, the equivalent damping ratios slightly reduces with the increase of the loading frequency. The research is based on the analysis of a two-layer Dou-Gon set from an ancient structure called Qinghui Hall at the Weiyuan Temple in Henan province, China. A full scaled specimen was made by glued laminated timber. Static pushover tests and dynamic shaking table tests were carried out under different loading conditions. The factors discussed in this study include vertical load imposed on the Dou-Gon system and the pre-strained levels of super-elastic bars. Analytical models have been built using the software Open System for Earthquake Engineering Simulation (OpenSEES). The parametric study has been carried out and the output acceleration spectrums have been recorded by inputting full scaled seismic waves. The results from static push over, dynamic tests and parametric study have shown that the simple technique with super-elastic alloy enhances the energy dissipation capacity, stiffness and the ultimate strength of the Dou-Gon system. Dou-Gon system with super-elastic alloy bar connections also show a better anti-seismic performance due to its constant damping behaviour and longer fatigue life. Moreover, pre-strain of super-elastic alloy bars can also increase the damping ratios of Dou- Gon system and lead to a greater energy dissipation, not only during the main earthquake shock but also for several aftershocks.