Research On Seismic Behavior Of Dou-Gong Brackets Used In Ancient Timber Buildings Under Different Skew Angle

Chinese ancient buildings have high artistic, historical and scientific value. Especially, Chinese ancient timber buildings(CATB) play an important role in Asian, even in worldwide buildings. However, due to the material properties and disasters, the existing CATB have been damaged seriously, such as the looseness of mortise-tenon, column shaft cleavage, the material degradation of beams, Dou-Gong Brackets skewing and so on. Considering the above bad impact on the overall mechanical performance of the structure, researching on the seismic behavior of CATB under damaged circumstance is important for protecting and maintaining historic buildings. The skewed Dou-Gong Brackets have an effect on the seismic behavior of the structure, so this paper mainly focuses on the performance of finite element models(FEM) of skewed Dou-Gong Brackets which are established by ABAQUS. Conclusions are drew as the following aspects:(1) By simulating the skewed Dou-Gong Brackets under the vertical monotonic loading, load-displacement curves,failure modes and mechanical performance were obtained. The results show that, under vertical load, the failure mode of skewed Dou-Gong Brackets belongs to the crushing collapse of Da-dou, similar to intact ones. Meanwhile, the skewed Dou-Gong Brackets are destructed more seriously. The load-displacement curves can be described by the double broken line model. The stiffness and allowed bearing capacity decrease when skew angle ranged from 0° to 6° increases and the largest drop is about 30%.(2) By simulating the skewed Dou-Gong Brackets under cyclic lateral loading, hysteretic curves and skeleton curves were obtained. The main components’ mechanical performance, the hysteretic behaviors, bearing capacity, rigidity degradation and energy dissipation were analyzed. The results show the intact and damaged joints’ failure mode is shear failure of the dowel and the slip. The hysteretic curves are asymmetrical and the asymmetry is more obvious when the skew angle increases. The load increases when loading-point displacement increases under positive loading and the load increases firstly and then decreases when loading-point displacement increases under reverse loading. Under positive loading, the peak load in skeleton curves increases by over 80% as the damage degree increases. Meanwhile, under reverse loading, the peak load decrease by 80% when the angle is between 0° and 6°. The stiffness and energy dissipation capacity reduce gradually when the damage degree increases, but Dou-Gong Brackets still have a good ability of deformation and energy dissipation. Obviously, the skew angle has an influence on bearing capacity, stiffness and energy dissipation.The research results show that the skew angle has a big effect on seismic behavior of Dou-Gong Brackets. The research results provide valuable references for damage assessment and retrofit of existing ancient timber buildings.