Performance of a novel ductile connection in steel-framed structures under fire conditions

The component-based model of a novel connection, which is designed to accommodate the high ductility demand of long-span steel beams in fire conditions, has been incorporated into the finite element software Vulcan. A single beam with the novel connections connecting it to rigid supports at both ends is first used to verify that the component-based model has been correctly incorporated into Vulcan, by comparing its results with those from detailed finite element models using the general-purpose package Abaqus. The performance of the novel connection has been compared with that of conventional connection types, including ideally rigid and pinned connections, endplate and web-cleat connections, using a sub-frame model. Results show that, compared with other connection types, the novel connection provides much higher axial and rotational ductilities, to accommodate the deformations generated by the connected beam as its temperature rises. To optimize the performance of the novel connection under the tensile axial forces generated by the eventual catenary action of heated, unprotected beams at high temperatures, parametric studies have been carried out on the influence of four key parameters, including the temperature of the connection, the inner radius of its semi-cylindrical section, the plate thickness and the bolt spacing. It is found that it is possible to optimize connection thickness, protection level, and inner radius of the semicylindrical section in order to delay the occurrence of bolt pull-out failure, and thus enhance a beam’s ultimate failure temperature. Finally, the combined static-dynamic solver of Vulcan is used to simulate the progressive collapse of a three-storey, three-bay frame with these novel connections. This progressive collapse simulation emphasizes the importance of connections for the survival of the entire structure in a fire event.