Mechanical model of dovetail joints of Min-Zhe woven timber arch bridges

The pseudo-static tests on full-scale models of dovetail joints of Min-Zhe woven timber arch bridges were conducted, the similarities and differences in the force mechanisms of dovetail joints between Min-Zhe woven timber arch bridges and ancient timber buildings were analyzed, and the applicability of the dovetail joint mechanical model in dovetail joints of Min-Zhe woven timber arch bridges was explored. According to the mechanical equilibrium and deformation coordination, the bending moment-rotation mechanical model and calculation formulas of dovetail joints of Min-Zhe woven timber arch bridges were proposed considering the tenon pull-out distance and mortise gap of joints. Through the test data and finite element analysis, the mechanical model and stiffness of dovetail joints of Min-Zhe woven timber arch bridges were verified. The effect of rotation and loading trips on the tenon pull-out distance and that of the mortise gap and axial force on the stiffness of dovetail joints were revealed. Research results show that the hysteresis energy dissipation of the dovetail joints of Min-Zhe woven timber arch bridges increases with the increase in the axial force in elastic stage. When the rotation is greater than 0.04 rad, the component enters the yield phase, and extrusion deformation cannot recover. When the rotation reaches 0.06 rad, the slope of the hysteresis curve stops growing. The dovetail joints are not damaged after loading. Due to the different force mechanisms of dovetail joints between Min-Zhe woven timber arch bridges and ancient timber buildings, the dovetail joint mechanical model of ancient timber buildings is not suitable for dovetail joints of Min-Zhe woven timber arch bridges. The error of bending moment-rotation of dovetail joints of Min-Zhe woven timber arch bridges between the finite element value and test value is only 3.2%, and the errors of positive and negative elastic maximum bending moments between finite element values and test values are 16.7% and -5.2%, respectively, indicating that the established bending moment-rotation mechanical model can accurately reflect the bending moment-rotation change law of joints during rotation. The tenon pull-out distance is influenced by the rotation in elastic phase and by the loading control displacement and loading stages in elastoplastic phase. The joint stiffness increases from 29.46 kN·m·rad^-1 to 52.24 kN·m·rad^-1 when the mortise gap reduces from 0.06 mm to 0.01 mm, indicating that the stiffness of dovetail joints increases with the decrease in the mortise gap. In summary, the proposed mechanical model can provide a reference for protection, repair, and research on the seismic performance of existing Min-Zhe woven timber arch bridges.