Computational Studies Aimed at Defining Bridging Requirements for Steel Joists

Abstract The Steel Joist Institute (SJI) specification’s bridging criteria for open web steel joists are based on conservative analyses completed several decades ago. These criteria have been recently updated in the 43rd edition of the SJI catalog. In an effort to investigate the accuracy and reliability of such design provisions, the Research Committee of the SJI has funded the authors with a multi-phase project that is aimed at determining the feasibility of using sophisticated second-order finite element analysis methods to model the stability of steel joists. An initial pilot study determined that computer models with appropriate boundary conditions could be prepared that accurately predict the stability behavior of steel joists that were previously experimentally tested. With a focus on predicting ideal brace stiffness and bracing forces, computational models of systems of one to ten parallel joists with intermittent out-of-plane bracing were then investigated. Studies that evaluate several possible modes of initial imperfections, load type (including gravity and uplift conditions), bridging type (including horizontal and X-bracing), and bridging support conditions were completed. This paper will provide an overview of this research project and provide several conclusions for defining erection-bridging requirements in SJI’s Standard Specifications.

View content