COLLAPSE SAFETY MARGIN-BASED DESIGN OPTIMIZATION OF STEEL STRUCTURES WITH CONCENTRICALLY BRACED FRAMES

Finding an optimum design based on collapse safety assessment for bracing systems in steel structures can result in a safer and economical design, and therefore is highly desirable.Several works in the literature have successfully applied various design methodologies for braced frames.The occurrence of unforeseen events outside the scope of these designs might jeopardize their structural integrity.Therefore, tools such as incremental dynamic analysis a nd modal pushover analysis have been developed to assess the probability of structural collapse.However, their implementation in the design process is challenging because their procedures are onerous and time-consuming.To overcome this issue, a straightforward method utilizing empirical equation to estimate the collapse margin of the structure is used.The proposed methodology uses the brace locations and sections as variables.A probabilistic analysis using multi-element removal identifies the bracing layouts, and explicit equations determine their optimal discrete sections.The methodology creates all the possible schemes, then identifies the optimal one that has the highest safety index based on a targeted collapse margin ratio.Through solving four typical examples of steel framed structures, the practicality, and accuracy of the proposed approach are proved.