Robust fire design of single plate shear connections

Single plate (shear tab) connections are designed to resist gravity loads by shear. During a fire event, large compressive and tensile forces could damage such connections and threaten the structural integrity of floors especially in multi-storey buildings. A robust design for single plate connections is needed to overcome fire induced forces and moments during both fire growth and fire decay in order to improve the structural integrity of floor systems. Using finite element studies validated by a full-scale frame Cardington building test, we investigated simple and cost-effective modifications of single plate connections to resist the forces and deformations induced by thermal loads during a real fire scenario. Results show that significant improvements in the behavior of such connections could be achieved by any of the following: adding a doubler plate to the beam web, matching the single plate thickness to the beam web thickness, using a larger distance from the bolt-hole centerline to the beam end and increasing the gap distance between the end of the beam to the connected member. Using larger bolt holes can also improve the fire performance through less axial restraint and thus more freedom for the beam to move (expand, contract, rotate) with the fire-imposed thermal loads.