A Stratified and Classified Performance-Based Seismic Design Method and Its Application in Steel Concentrically Braced Frame Systems

The performance-based seismic design (PBSD) method transforms the qualitative structural seismic precaution objectives of traditional code-based design methods into multi-level performance objectives which can be quantitatively comalyzed. Based on the numerical simulation analysis, the structural performance accuratery evaluated and targeted seismic measures are ernployed to meet specific structural demands. This method is particularly suitable for out-of-code structures and high-performance design where traditional methods are insufficient to optimize structural performance. The paper introduted a stratified and classified PBSD method, which was developed by the authors’ team through extensive research on performance-based seismic design, component performance evaluation criteria, and engineering applications. The method’s key procedures include defining seismic precaution objectives, conceptual design, performance objective setting, structural analysis, and performance evaluation. The approach emphasizes stratification and classification to refine structural and component performance objectives, integrates elasto-plastic analysis into seismic measures, and uses performance evaluation results as a foundation for design decisions, ensuring alignment with specified performance goals. A multi-storey steel concentrically braced frame located in a high seismic intensity zone was taken as a case study to illustrate the practical application of the proposed method, and the engineering applications of the stratified and classified performance-based seismic design method were discussed as well as its differences from the traditional design methods in codes. The design process began with conceptual design, performance objective setting, and preliminary design based on the "weak brace" concept. Structural analysis, performance evaluation, and design adjustments were iteratively optimized by using computational algorithms to minimize steel usage in primary components. The optimization ensured compliance with predefined performance criteria, including structural drifts, stress ratios of components, and damage grades. The results demonstrated that, compared to the original schemes based on the traditional seismic design methods in codes, in the scheme designed by the stratified and classified performance-based seismic design method, the cross sections of braces decreased significantly, while those of columns connected to braces increased. The steel usage in primary components was reduced by 23%. Furthermore, the scheme designed by the proposed method reduced structural drifts and the maximum total seismic input energy, increased plastic deformation energy dissipation, effectively minimized the damages of vertical components, and distributed the damage of braces more uniformly under rarely occurred earthquake, resulting in a more efficient and resilient energy dissipation system. In conclusion, the proposed stratified and classified PBSD method delivers superior seismic performance while optimizing material usage, demonstrating its potential for efficient and resilient structural design.