System Reliability of Structural Steel Frames: Component- and System-Based Design Methods

Abstract

Current design practice for structural steel buildings is largely governed by component-based design methods, which ensure strength and reliability on the level of individual components of a structural system. However, with the recent advances and increasing accessibility of structural modeling and analysis tools, there has been a growing interest in system-based design methods, which ensure strength and reliability on the level of the entire structural system. As the profession moves toward broader adoption of system-based design methods, additional studies are essential to quantify system-level reliabilities and inform future design codes. In this study, we investigate system-level reliabilities achieved by two component-based design methods, Direct Analysis Method and Advanced Elastic Analysis Method, and two system-based design methods, Advanced Inelastic Analysis Method and Direct Design Method. A series of benchmark structural steel frames were first designed using a structural design optimization framework. System reliability analyses that included uncertainties in geometric properties, material properties, and applied loads were then performed on the resulting designs using the Importance Sampling technique. The findings indicate that component-based design methods consistently produce system-level reliabilities that exceed expected target levels; however, these design methods result in designs that are significantly heavier than those produced by system-based design methods. In contrast, the system-based design methods result in significantly lighter designs, with more consistent levels of reliability that are closer to expected target levels. Based on these findings, recommendations are provided to improve system-level reliability calibration procedures and to support the implementation of system-based design methods in future design codes.