Behavior, Design and Finite Element Modeling of Shear Connections under Fire Hazard

The current design of steel shear connections in buildings is limited to calculating the shear strength at ambient temperature. During a building fire, the floor systems in steel buildings undergo significant geometric changes which in turn subject the connections to large axial loads and moments in addition to shear from gravity loading. The research presented in this dissertation investigates the behavior of single angle shear connections by utilizing state-of-the-art finite element models. Based on these finite element models, the dissertation discusses the limit states related to the fire performance of shear connections and provides closed-form solutions that can predict their performance. These solutions are a basis for developing a performance-based approach to shear connection design under fire. During a fire event, the axial force compressive demand on the connected beam depends on the connection geometry and on the local buckling capacity of plates at elevated temperature. The capacity of shear connections is based on the tensile capacity of the connections, which is reached during the cooling phase of the fire as the beam contracts. This research proposes simple cost-effective modifications to single plate shear connections to improve their robustness against fire. Finally, double angle shear connections were studied experimentally and with finite element modeling. Comparison of performance with single plate shear connections indicate that angle connections offer more flexibility and thus survive a fire longer than the single plate connections.