Investigation of secondary prying in thick built-up T-stub connections using nonlinear finite element modeling

Abstract

This study investigates the prying behavior in thick-flange built-up T-stub/column systems that should be addressed in designing full-strength double tee connections for use in moment resisting frames which satisfy prequalification requirements. In particular, this study focuses on the phenomenon herein indicated as secondary prying, which is related to the additional forces that are introduced into the tension bolts due to significant bending of the column flange.Three-dimensional finite element models that incorporate pretension of fasteners, full contact interactions, and nonlinear material characteristics are used to investigate secondary prying effect in thick-flange T-stub/column system with and without continuity plates. This study provides insight as to whether continuity plates are necessary in columns when designing and detailing full-scale T-stub connections for prequalification. The effect of secondary prying is incorporated into an existing prying strength model for thick T-stubs to quantify the amount of total prying encountered in thick built-up T-stub connections with and without continuity plates. Parameters that impact the secondary prying in thick flange T-stub/column systems were identified based on the geometric configuration that results from the design of full-strength double tee connections with deep girders. The results show that decreasing the effect of secondary prying is achieved through either increasing the column size, or adding continuity plates to the column. This study provides information for detailing columns without continuity plates as well as quantifying the amount of prying so engineers can design for the additional load by increasing the bolt diameter.