Mechanical Behavior Of Bolted Joint With Slotted-in Steel Plate In Reticulated Timber Shells

The one of key points to build timber latticed shell is to design wood connections. Designers must comprehesively understand the mechanical behavior of the joints. Bolted connection with slotted-in steel plate is commonly used in timber latticed shell. However, it is insufficient comprehensively and clearly understand this joints in China. Therefore, it is of great significance to study the mechanical behavior of the joints.In this paper, the calculation formula for bearing capacity of single-bolted connections with slotted-in steel plate was derived based on the hypotheses of elasto-perfectly plastic model and the perfect rigid plastic model respectively. The differences and similarities of the two were contrasted, and there was only fine distinction on the constant in the formula for the failure mode which forms two plastic hinges. The flexural capacities of two different joints were calculated based on two formulae respectively, and experimental study of them ware conducted. The load-displacement curves and moment-rotation curves were obtained, which are consistent with their theoretical results. After the comparison of the failure mode of the specimens, the failure rules were summarized and new joint was redesigned, and a series of suggestions were developped: symmetric steel braces, elliptical bolt holes, and the bigger margin, edge distance and separation distance to avoid longitudinal shear failure or splitting failure of perpendicular grain, are improvements for the joints.The constitutive relation of wood is very complex. 3D FE material model for wood assuming transversely isotropic elasto-perfect is applied. Different material models are established for different regions(The elastic modulus of the wood nearby the bolt hole was reduced).The material model was verified by simulating joints model test under multi loading conditions in the literature and comparing the test results. Finite element models based on above material constitutive model are established and analyzed. The load-displacement curve from finite element modelling were compared with test results.Multi groups of parameters were chosen for parameter study. The influence of the number of bolts, diameter of bolt, Thickness of the steel plate, axial force on flexural bearing capacity and flexural stiffess of the joints were studied. Finally, finite element analysis were carried out for the hysteretic behavior of two joints,from which hysteresis curve, skeleton curve, degraded stiffness curve and energy dissipation coefficient curve were obtained. Hysteretic performance of the joint was evaluated.Through theoretical calculation, experiment and numerical simulation, the research on bolted connections with slotted-in steel plate was conducted. The joint was optimized and this paper discussed the influence of various parameters on the flexural stiffness and flexural bearing capacity of the joints. It will provide some advantageous suggestions for designing project.