Performance-based seismic design methodology for tall buildings with outrigger and ladder systems

The plethora of efforts needed for conducting the Performance-Based Seismic Design (PBSD) to investigate the tall buildings' performance requires sustainability in developing this approach and facilitating its implementation to obtain an effective final design. To tackle this issue, novel performance-based design procedures are proposed in this study. The novel PBSD procedures commence with integrating the optimization and simplification techniques into the preliminary design stage to rapidly obtain an optimal initial amount of materials required to establish outrigger and ladder systems models. Then, conducting a nonlinear time history analysis with the aid of ETABS and Peforme-3D software to scrutinize the extent to which the initial design approaches the final design and the superiority of each system under frequent or rare earthquake events. The global and component responses are examined for each system under three performance levels: immediate occupancy IO, life safety LS, and collapse prevention CP. The optimization and simplification techniques in the preliminary design stage have reduced the overwhelming efforts required to generate and prepare an optimized preliminary design for both systems. Furthermore, the results of the nonlinear time history analysis found that the ladder system reduced the structure's global response by 27.2% for the lateral displacement and 30.4% for the base shear than the outrigger system. However, the evaluation of the components acceptance criteria confirmed that the ladder system increased the plastic damage distribution in the external structural system's components and reduced it in the internal one. Generally, the preliminary design approached the final design by varied ratios, 60-80% in the ladder system and 60-95% in the outrigger system for different components. Therefore, it is recommended to apply this approach to the outrigger system and improve the ladder system's efficiency. Finally, this study is limited to an optimized preliminary design that approaches the final design and reduces the iteration number of the PBSD procedures. Thus further researches are required to improve and extend the applicably of these procedures.