New Joint Exploitation For Single Layer Spatial Grid Structure With Free-Form Surface And Stable Bearing Capacity Analysis Of The Structure Under Wind Load Case

To maintain elegant architectural images, single layer spatial grid structures with free-form surfaces are increasingly employed in practical projects. However, there are still two problems to be solved for such type of design:firstly, to achieve the concept of prefabrication as well as to adapt to complicated location and changeable space geometry relation, this type of structure is quite deficient in the connecting formats of reliable joints; secondly, the analysis of stability bearing capacity under the wind load is rare due to its sophistication and gentleness in structure with the former making it rather difficult to estimate the wind load distribution and the latter causing its sensitiveness to wind load.As for the first problem, this paper developed a new jointed precast connection—the bolt-cylinder joint, and provided the design methods of every component of the bolt-cylinder joint. To verify the reliability of the joint connection, finite element analysis of the joint was conducted. Findings of the analysis are as follows:firstly, this new type of joint has clear path for force transfer and is reasonable in load-bearing; secondly, the thickness of the end-plate of the adapters had a significant impact on the initial rotational stiffness and the ultimate bending moment in the plane but little impact on the initial rotational stiffness and the ultimate bending moment out of plane; thirdly, the length of the sleeve entablature did not much affect the initial rotational stiffness and the ultimate bending moment both in the plane and out of plane. Then, this paper designed three transverse tests for the joint in and out of plane. The experiment proved the reliability of the design methods of each component of the bolt-cylinder joint and the finite element analysis. Last, to better apply the bolt-cylinder joint to practical projects, this paper derived the formula of the initial rotational stiffness and the ultimate bending moment of the joint in and out of the plane and provided both the three-parameter and four-parameter moment-rotation relationships of the joint. The comparison with results of the experiment and the finite element analysis proved that both the three-parameter and four-parameter models can well simulate the moment-rotation relationship with the former was weaker than the latter only in the simulation of the back end.As for the second problem, this paper introduced the numerical wind tunnel which was used to confirm the wind pressure distribution on the surface of structure, and explored the key parameters in the numerical simulation. Then, it provided the wind pressure distribution on the surface of a practical single layer spatial grid structures with free-form surface. Last, taking the project as an example, this paper provided an in-depth discussion about in wind load cases the influence of factors such as the grid size, initial imperfections (including the joint imperfections for location and bar imperfections), geometric nonlinearity, material nonlinearity and the joint stiffness on the structural stability. At the same time, the dynamic stability is explored. Valuable conclusions for the design of single layer spatial grid structures with free-form surface had been obtained as follows:firstly, the joint imperfections for location can reduced the structural bearing capacity to a certain degree; secondly, the bar imperfections had little impact on the structural bearing capacity; thirdly, the account of geometric nonlinearity and material nonlinearity significantly decreased the structural bearing capacity, especially for the latter; fourthly, the joint stiffness did have a weakening impact on the structural bearing capacity and it’s necessary to take into account the joint stiffness when it couldn’t be ensured that the joint was rigid connection; Compared with the bearing capacity of static stability, the bearing capacity has obvious decreased when considering the fluctuating wind load. Therefore, it is necessary to analyze the dynamic stability of single layer spatial grid structure with free-form surface.