Semi-mechanism-based hysteretic model for traditional heavy timber frames with forked column foot joints and various wood panel infill

Abstract

Frames are essential lateral load-resisting elements in traditional Chinese timber structures. This paper presents a semi-mechanism-based hysteretic model for the lateral load-displacement relationship of traditional heavy timber frames with forked column foot joints and various wood panel infill. The backbone curve of the proposed model was determined based on the rocking and the racking mechanisms of the frames. Key points of the backbone curve, including the elastic limit point and the peak load point, and the corresponding tangent stiffness were expressed by the geometrical and physical parameters of the frames. Reloading and unloading paths were defined based on the elastic limit load and the elastic stiffness. Experimental results of typical frames were utilized to verify the proposed model regarding the backbone curve, hysteretic behavior and energy dissipation. Good agreement was achieved. Model-based parametric study was further conducted. The influence of infilled wood panels and vertical compression load was investigated. It is found that the lateral resistance contribution of the wood panels with a door opening is slightly greater than that of wood panels with a window opening, and the performance of frames under higher vertical compression load levels (without causing compression failure of the columns, which is rare) are superior to those under lower levels, e.g., a reduction of 50% in the vertical load can lead to a drop in the peak load and the cumulative dissipated energy of the frame of 13% and 30%, respectively.