Seismic performance of wedge-shaped box joint of beam and box column in tourism greenhouse structures

In order to meet the requirement of the greenhouse structure construction, a wedge-shaped box joint connecting box column and H-shaped beam was proposed to overcome the inconvenient construction and poor seismic performance of the conventional joint in the H-shaped beam and box section column, such as the conventional outboard plate joint and the internal baffles joint. The finite element simulation analysis of the joints under cyclic loading was carried out by the finite element analysis software ANSYS. The seismic performance of the joint was analyzed and compared with the conventional outboard plate joint and the internal baffles joint. The influences of the flange and web thickness of the beam, and the thickness of the rectangular tube column on the seismic performance of the joint were discussed. The seismic performance of the wedge-shaped box joint was better than that of the outboard plate joint, so it could be applied to the actual engineering instead of the conventional outboard plate joint. The cumulative energy consumption was 25.40% higher than that of the outboard plate joint, and 20.46% lower than that of the internal baffles joint. The stiffness of the wedge-shaped box joint was larger than that of the outboard plate joint. The hysteretic curve of the joint was relatively full, which embodied the good seismic performance. The plastic hinge of the internal baffles joint appeared at about 200 mm outside the column edge. The plastic hinge of the wedge-shaped box joint and the outboard plate joint was about 450 and 500 mm outside the column edge, respectively. However, the region area in the wedge-shaped box joint was smaller than the other joints. The plastic hinge position of the wedge-shaped box joint moved to the middle of the span under cyclic loadings, which ensured the design concept of "strong column with weak beam, strong node with weak component". The thickness of the flange and web of the wedge-shaped box joint had a great influence on the seismic performance. In the case of no exceeding the thickness of the column, the initial stiffness, the yield load and the ultimate bearing capacity of the joint were obviously increased with the increasing of the thickness of the flange and web of the beam, which meant that the seismic performance of the joint was improved. At the same time the adverse consequence of strong beam would not be produced. The change rate of cross section width of wedge-shaped box had a great influence on the energy dissipating capacity of the joint. As the change rate of cross section width decreased from 1:2 to 1:5, the energy dissipating capacity of the joint and the stiffness after yielding increased. However, it was difficult to make the production and installation of the joint. In practical engineering, it was suggested the change rate of cross section width should equal 1:4. Therefore, the distribution of the stress in the wedge-shaped box joint was more reasonable. After solving the defects of the internal baffles joint, such as the inconvenience of the construction and pouring concrete, the bearing capacity and stiffness of the wedge-shaped box joint were improved, which were beneficial to the seismic resistance of a structure. The above results show that the wedge-shaped box joint has a good seismic performance and is more suitable for tourism greenhouse structures.