Improved Park-Ang Two-Parameter Damage Model of Mesh Shell Structures

To reasonably evaluate the damage degree of a single-layer spherical mesh shell structure during an earthquake, we develop an improved two-parameter nonlinear combined damage model based on the existing Park-Ang damage model for mesh-shell structures by subtracting the displacement of the elastic phase from the displacement term and adopting the form of a nonlinear combination of the displacement term and the energy dissipation term. Based on material damage accumulation, 144 sets of numerical models covering different spans, rise/span ratios, roof masses, and member sizes were developed and fitted to obtain the values of the parameters to be determined in the damage model, and then, an improved Park-Ang two-parameter damage model for mesh-shell structures was proposed. The critical values of damage indices of the structure at the four performance points were 0, 0.3, 0.7, and 1. The validity of the two-parameter damage model was verified using a single-layer spherically mesh shell structure with three different structural parameters. The results revealed that the improved Park-Ang two-parameter damage model has a damage value of zero in the elastic phase, which satisfies the lower bound convergence and has a good computational accuracy and small dispersion. In addition, the index values of the four performance points reflect the performance status of the mesh-shell structure, indicating that the improved Park-Ang damage model is suitable for evaluating the damage evolution process of the structure under seismic action. This proposed damage model lays a foundation for vulnerability analysis and seismic risk assessment of mesh shell structures, a basis for post-earthquake repair, the development of an optimal design for mesh shell structures, and the analysis of casualty and economic loss statistics.