Designing Steel Joist Seats Subjected to Rollover Forces

The mechanisms governing the response of steel joist seats subjected to rollover forces were identified through physical testing of fifteen specimen pairs and the applications of concepts from Fisher et al. (2002) and Green and Sputo (2002). The experimental test method was developed based on the field observations to more closely resemble actual conditions of steel joists seats in buildings. In doing so, it was observed that the response of joist seats subjected to rollover can be separated into two phases: elastic and inelastic. In both phases, it was observed that the shape of the yield line produced on the bearing seat did not vary with the thickness of the material, as was observed by Green and Sputo (2002), but was consistent across all bearing seat sizes and thicknesses. Applying the yield line concepts from Green and Sputo (2002) and the rollover statics from Fisher et al. (2002) to this new yield line geometry produced a plausible method for predicting joist seat rollover capacity. With more extensive testing across a wider range of bearing seat thicknesses and sizes, the observations from this testing could produce a simple analytical model for predicting rollover capacity of joist seats for industry’s use.