Evaluation index and classification of seismic damage of spatial structure

The large-span space structure is widely used in large public buildings such as terminals, high-speed railway stations and exhibition centers, which are crowded with people and have large investment. Under the action of earthquakes, it is necessary not only to ensure its seismic safety, but also to consider its possible degree of earthquake damage and economic losses, that is, to carry out performance-based seismic design. The basic principle of seismic performance design in GB 50011-2010 Code for Seismic Design of Buildings is mainly based on concrete structure, which is not suitable for long-span space structure. Therefore, taking single-layer spherical reticulated shell, single-layer cylindrical reticulated shell and truss as examples, the finite element method is used to analyze their seismic response characteristics and failure modes, determine suitable earthquake damage evaluation indexes, classify their earthquake damage grades, and provide support for performance-based seismic design of large-span spatial structures. According to JGJ 7-2010 “Space frame Structure Technical Regulations”, 15 single-layer spherical reticulated shell structures, 9 single-layer cylindrical reticulated shell structures and 16 tube truss structures with different spans and different vector span ratios were designed by using the design software 3D3S. The finite element software ABAQUS was used to establish these structural finite element models. According to the provisions of GB 50011-2010, 34 ground motions conforming to the target response spectrum of the structure were selected from the ground motion database of the Pacific Earthquake Engineering Research Center, and the three-way amplitude-modulated ground motions of 1∶0.85∶0.65 were performed on the structural input. The response of the structure under different ground motions of different intensity is analyzed, and the seismic response characteristics and failure modes of the structure are summarized.

The results show that: For single-layer spherical reticulated shell structures, the maximum displacement of nodes changes significantly in ground vibration intensity, and the plastic strain energy can fully reflect the damage degree of the structure. Therefore, two parameters, the maximum displacement of nodes and the plastic strain energy reflecting the earthquake damage degree, are used as the evaluation indexes of the structural earthquake damage. Based on the damage index of single-layer spherical reticulated shell structures with different weights, the earthquake damage classification criteria are proposed. For the single-layer cylindrical reticulated shell structure, the structural deformation and seismic displacement response of the structure are similar in the secondary static analysis, indicating that the damage of the structure under static action is further developed on the basis of its seismic damage. Therefore, the static ultimate bearing capacity of the structure before and after the earthquake action is used as the evaluation index of structural seismic damage. Based on the damage index considering the change of static ultimate bearing capacity, the classification criteria of seismic damage of single-layer cylindrical reticulated shell structures are proposed. For the tubular truss structure, a large plastic deformation occurs in the mid-span area of the main truss and near the support, and the structural stiffness is significantly reduced. The plastic strain is used as the seismic damage evaluation index of the large plastic deformation rods, and the damage grade is classified. According to the proportion of the rods with different damage grades, the classification criteria for the seismic damage grade of the tubular truss structure is proposed. The maximum displacement-to-span ratio of single-layer spherical reticulated shell and single-layer cylindrical reticulated shell is positively correlated with the damage index. Therefore, the seismic damage grade of the structure can be divided according to the maximum displacement-to-span ratio, which is simpler and faster.