Study on out-of-plane flexural behavior of aluminum alloy gusset joints at elevated temperatures

Aluminum alloy gusset (AAG) joint is the most widely applied joint system in aluminum alloy reticulated shells, and the elevated-temperature mechanical behavior of joints have serious influence on the safety of structures. This paper investigated the out-of-plane flexural behavior of AAG joint by means of experimental and numerical analysis, and theoretical formulae of its bearing capacity and bending stiffness were derived. Firstly, elevated-temperature experiments on 9 AAG joints were conducted in a special-shaped oven. The test results revealed that: (1) the failure modes of thin-plate AAG joints at temperatures under 300 °C are block tearing and local buckling of the gusset plate, which remain the same as those at room temperature; (2) when the gusset plate is thick enough (usually as thick or thicker than the flange of the member), the joint zone will not collapse under 300 °C; (3) the initial stiffness approximately remains unvaried, while the ultimate flexural bearing capacity drops with the elevation of temperature. Subsequently, finite element (FE) models using ABAQUS were established and verified by the test results. It is confirmed that the FE models can accurately describe the mechanical performance of the AAG joints at elevated temperatures. Based on the simplified FE model, a parametric study was carried out, considering various aluminum alloy brands, thickness of the gusset plate, radius of the center region of the gusset plate and different temperatures. Finally, the block tearing resistance, the local buckling resistance, and parameters of four-linear bending stiffness model of the FE models were presented, and the theoretical formulae were derived using statistical regression technology. The theoretical formulae were verified to be accurate enough against the experimental and FE results, to estimate the bearing capacity and the nonlinear bending stiffness of AAG joints at elevated temperatures under 300 °C, which can serve for practical engineering.