Applying Improved Performance-Based Instructions to Investigate Seismic Performance of a Code-Conforming Steel Trussed-Tube Building

Despite the many advantages of tube systems with braces, known as trussed tubes, no specific seismic design criteria exist in the current regulations to design them, and practitioners utilize common methods used for common building structures to deal with designing such systems. The aim of this study is to investigate the performance of a 31-story steel trussed-tube building designed according to the customary design provisions. To evaluate the performance of the code-conforming designed structure, a three-dimensional nonlinear static (pushover) analysis is employed, and the acceptance criteria corresponding to different performance levels are examined. The obtained performance-based results are then compared with the design based on the customary guidelines, and the shortcomings of common design regulations in the design of trussed-tube buildings are highlighted. By observing the state of the plastic hinges, as well as force-controlled joints at two distinct earthquake hazard levels, it is found that the structure under study, which was loaded, analyzed, and designed exactly in compliance with the requirements of the regulations and standards, does not satisfy the performance criteria. In a typical nonlinear brace hinge, for instance, the results indicate that the LS acceptance criterion has been exceeded by approximately 30 percent at the BSE-1 hazard level. Also, the drifts surpass the 1% limit at specific levels, with the maximum drift reaching approximately 1.4%. As a result, the design of trussed-tube systems based on common codes and regulations can lead to an unsafe design that lacks the expected performance intended in their service life.