Hysteretic behaviors reinforcement of Dou-Gong brackets: Experimental and numerical study

Abstract

Mantou tenon joints have the largest geometry and are subjected to the most complex internal force in a Dou-Gong bracket in ancient palace-style timber buildings, meanwhile, they are also the key connections affecting the hysteretic behaviors of the Dou-Gong bracket. In this study, in order to improve the hysteretic behaviors of the Dou-Gong brackets, wood and lead were used as materials for reinforcement. Three full-scale specimens were fabricated, in which the Mantou tenon joints between the Da-Dou and the Pingban-Fang were the traditional square-sectional Mantou tenon, the circular-sectional Mantou tenon, and the lead rod, respectively. Failure patterns, hysteretic and skeleton curves, stiffness degradation, strength degradation, and energy dissipation capacities were investigated through quasi-static loading tests. Parameter analyses were carried out by the FE method to determine the sectional diameter and the length of the Mantou tenon when the hysteretic behaviors of the Dou-Gong brackets were optimal. The results indicate that the failure pattern of the Dou-Gong bracket with a circular-sectional Mantou tenon does not change, the larger ultimate load and initial stiffness, the smaller stiffness and strength degradation, and stable energy dissipation capacities are exhibited in the reinforced Dou-Gong brackets. However, for the Dou-Gong brackets with a circular-sectional lead rod, bearing capacities, ductility, and the initial stiffness decrease, the rate of stiffness degradation is faster and the Da-Dou is damaged. With the increase of the sectional diameters of the Mantou tenon, the yielding and ultimate load of the Dou-Gong brackets increase evidently. But as the lengths of the tenon increase, the ultimate bearing capacities of the Dou-Gong bracket increase slightly. In terms of the reinforcement suggestions, the mortise should be properly reamed and drilled deeper, and the original Mantou tenon is replaced with a circular one with larger sectional diameters and longer lengths.