Static behaviour of a two-tiered Dou-Gong system reinforced by super-elastic alloy

The Dou-Gong system in Asian timber structures plays an important role in resisting seismic action. Traditional carpentry in Asia uses timber pegs to connect components, which enables relative movement between components and hence provides friction to dissipate energy in an earthquake. This method, however, has some shortcomings, such as inadequate stiffness to resist a large lateral force, and, therefore, the structures tend to exhibit permanent deformation after earthquakes. This study proposes a new technique by using super-elastic alloy bars to replace conventional wooden peg connections to enhance the seismic performance of the structures. Static pushover experiments were conducted on full-scale two-tiered Dou-Gong systems, and high-strength steel and conventional wooden pegs were used as benchmarks. The ultimate stiffness of the Dou-Gong system has shown an increase when both high-strength steel and super-elastic alloy bars were used, but only super-elastic alloy can provide a consistently high damping ratio. This technique also involves pre-strain of the super-elastic alloy, and the outcomes of this series of experiments have shown that pre-strain of the super-elastic alloy can significantly increase the damping ratio in the structure, and, hence, more energy is dissipated. The results of this paper can be used in projects of timber structures using the Dou-Gong system.