03.07: Robustness in fire of a new type of beam‐to‐column connection

In this paper a new type of beam‐to‐column connection is introduced, which is capable of absorbing both very large rotations and axial movements, due firstly to thermal elongation and subsequently to extreme weakening of the connected beam. The main idea is to connect the beam and column using a special connector bolted to the column flange using a face‐plate and to the beam web using a fin‐plate. Between these a highly ductile element, which is in this case a hollow circular tube, is included. This plays the crucial role in absorbing beam‐end movements occurring firstly during the expansion of the beam and secondly during its catenary behaviour at very high temperatures.

This study aims to extend the research on this connection to structural case studies in the context of performance‐based structural fire engineering design. The connection has been modelled using different approaches, starting with 3‐D finite element modelling and proceeding to validated simplifications which feed into a component‐based model. In order to make calculations feasible, the mathematical model of the ductile component is developed and calibrated using the information provided by parametrized numerical FEM computations. The component model is developed to be capable of representing the hysteresis occurring due to deformation‐reversals as temperatures rise, as well as failure corresponding to fracture in tension. Thus, the component model is described as a function of displacement and temperature, including sufficiently realistic plastic deformation and fracture criteria. This model is then implemented into global FEM models and utilized to assemble the stiffness matrix of a special connector element used to join the beam and column nodes. This component‐based connection model is then applied in some comparative studies.