Hysteretic behavior of an ancient Chinese multi-layer timber substructure: A full-scale experimental test and analytical model

Fork-column dou-gong connections and mortise-tenon jointed frames are extensively used in the construction of ancient Chinese multi-layer timber structures, and their combined hysteretic behavior is essential for the seismic response of such structures. In this paper, a full-scale substructure model consisting of fork-column dou-gong connections and a mortise-tenon jointed frame was tested under cyclic load. The load-transfer and deformation mechanism between the dou-gong layer and the frame layer was studied, and it was found that the horizontal load was transferred through the friction at the horizontal interface between the two layers. The hysteretic curves, envelope curves, stiffness degradation curves and energy-dissipation abilities of the two layers were assessed and compared. Results shows that the stiffness of the dou-gong layer is about 6.5-14.3 times that of the frame layer, which leads to the larger portion of the loading displacement taken by the frame layer. However, the dissipated energy of the frame layer is much larger than the dou-gong layer. The bilinear model and Pinching4 model were proposed to respectively simulate the behavior of the dou-gong layer and the frame layer, and they were connected in series to represent the experimental model. The hysteretic curve of the analytical model shows good agreement and can reflect the major nonlinear characteristics of the experimental model.