Robustness And Component Model Of Fin Plate Connections In Fire

Traditional proscriptive and single-member performance-based fire resistance design methods can not consider well the interaction between structural members, which has significant influence on the behaviour of the whole structure in fire. Connections are key components in framed structures. They are subjected to not only shear force and moment, but also axial force in fire. The Stiffness of connections determines the internal force distribution, and hence the behaviour of the whole structure, and the good tying capacity and ductility of connections are key factors to prevent progressive collapse. Traditionally, connections are studied in terms of their moment-rotation behaviour, which can’t represent the behaviour of connections under complex force state. Creation of a new connection model which can be included in performance-based structural fire engineering design is essential to improve the robustness of connections and the whole structure.In this thesis, the robustness of fin plate connection in fire is investigated and its component model is created. The main content includes:(1) A set of fin plate tests under combinations of tension force, shear force and moment and different temperatures are reported. The observations include load bearing capacity, rotation capacity, force-deformation curve and failure mode. The reduction factor of connection resistance with increase of temperature is analyzed. The design methods of controlling the failure mode of fin plate connection in BS5950-1:2000and EN1993-1-8:2005are evaluated.(2) The method of creating three dimensional solid non-linear finite element model of fin plate connection in fire is proposed, which includes the choice of analysis procedure and solution, definition of high temperature material property, choice of element type and definition of contact. An existing simple test is used to conduct mesh convergence study and the correctness of the method is preliminarily verified. (3) Finite element analysis is performed on the robustness tests of fin plate connection in fire. The finite element model is further confirmed by comparing finite element analysis results with test results. In addition, stress field and contact forces can be obtained from finite element analysis which is hard to measure in the tests, the failure mechanism and each bolt force are then analyzed based on these results.(4) Parametric studies are performed to investigate the behaviour of plate in bearing component and bolt in shear component when friction is not considered, based on which the calculation methods of load bearing capacity and stiffness of both components at different temperatures are proposed, and the function relations between force and deformation of both components are established.(5) Parametric study is performed again to investigate the friction force in plate in bearing component when friction is considered. The relation between friction force and the force acting on the component is established, based on which the lap joint component model is simplified and the fin plate connection component model is created finally.(6) The component model is used to simulate the robustness tests of fin plate connection in fire, the accuracy and efficiency of the component model is verified.(7) The application of the component model in improving the robustness of fin plate connection itself and the whole structure is discussed. The design idea on controlling the failure mode of connection in fire is proposed, and the usage of component model in the whole structure fire resistance analysis is demonstrated.