This paper presents an investigation on the rotational behaviors of fork-column Dou-Gong. Five scaled specimens in different construction forms were manufactured and tested by low reversed cyclic loading under three different vertical loads. The failure modes, envelope curve, strength degradation, deformability ratio, stiffness degeneration, and energy dissipation were assessed and compared. The results indicated that the increment of the rotational stiffness gradually decreases with increased vertical load. The relationship between rotational stiffness and vertical load can be simplicity expressed by a logarithmic function. The length, construction form, and number of linking beams are the main parameters affecting the rotational behaviors of single Dou-Gong. Reducing the length or enhancing the combined effect of the linking beams can effectively improve the bearing capacity and deformation capacity of the Dou-Gong, as well as energy dissipation capacity. The rotational behaviors of single Dou-Gong with one linking beam are worse than those of Dou-Gong linked by two beams. In addition, the double Dou-Gong exhibits better symmetry and plumper area than the single Dou-Gong, thus resulting in 109%, 78%, and 163% increment in bearing capacity, rotational stiffness, and energy dissipation, respectively. The moment-rotation curve of fork-column Dou-Gong is nearly trilinear and based on the appropriate mechanical parameters from the test results, the nonlinear hysteresis characteristics of the fork-column Dou-Gong can be simulated by an improved double-target model.

This article presents the results of an experimental study on the rotational behavior of degraded Chinese traditional mortise-tenon joints with different degradation types and different degradation degrees. Six joint specimens degraded through artificially simulated method, were tested by reversed cyclic loading, from which the moment-rotation curves were obtained. The results indicated that the rotational behavior of these joints is semi-rigid, the hysteretic curve shapes of degraded joints are same to that of joint without degradation. The maximum moment, yield moment, and initial rotational stiffness of degraded joints decreases as the degraded degree increases, whose empirical degradation relationships were obtained based on the test data. A hysteretic model for degraded traditional mortise tenon joints was proposed. Experimental results were used to validate the proposed hysteretic model. Good agreement between predictions and tests was observed.

This study presents the test results of three specimens of traditional Chinese timber frames (TCTFs) with two types of column heights and two types of vertical loads. The specimens were initially loaded to damage, then strengthened with different numbers of shape memory alloy (SMA) wires and retested. The lateral performance, such as failure modes, envelop curves, stiffness degradation, and energy consumption, was analyzed to evaluate the SMA strengthening effects. Results showed that the lateral bearing capacity, stiffness, and energy consumption of the strengthened specimens were evidently improved, and even exceeded the undamaged level when relatively larger displacements were imposed. An analytical model for frames jointed by semirigid mortise–tenon and hinged column-foot joints (SHFs) was proposed. Lateral load-displacement responses of both the strengthened and unstrengthened specimens were predicted by the model, and good consistency was obtained compared with the test results. The influence of column heights, vertical loads, strengthening degree, and frame spans on lateral behavior of TCTFs also were evaluated through both experiments and parametric studies. This work provides a valuable reference for the restoration of historic timber structures.

This article aims to investigate the contact characteristics of mortise and tenon (M&T) joints in the traditional timber structures. In particular, the normal embedded compressive contact between contact surfaces of M&T joint was investigated. Based on basic contact theory and contact characteristics between mortise and tenon, a normal elasto-plastic contact model, which can reflect the real normal contact behavior of M&T joints in traditional wooden structures, was proposed. Coulomb friction contact was utilized to describe the tangential slipping characteristics of the contact surfaces. Micro-morphology scanning tests of wood samples with different roughness were carried out to determine the parameters involved in the normal contact model. The normal contact model subroutine of M&T joint was compiled by FORTRAN language, implemented into ABAQUS through user-defined interface (UINTER). Then the proposed model was verified by shear tests of wood contact surfaces considering different normal pressures. Finally, a finite element model (FEM) of straight tenon joint subjected to cyclic reversed loading, based on the proposed normal elasto-plastic contact model, was developed, and a FEM considering normal “hard contact” between the contact surfaces, was also performed. The simulation results were validated by the experimental results. Results showed that the user-defined normal elasto-plastic contact FEM was more in line with the actual force state and mechanical behavior of M&T joints, which can more accurately predict the failure modes and simulate the hysteretic behavior of M&T joints, compared to the FEM considering normal “hard contact” of the contact surfaces.