Analytical Study of Common Rigid Steel Connections under the Effect of Heat

One of the most important members of steel structure’s connection region is beam-to-column connection. Rigid connection in steel moment frame has special role in the behavior of these structures and the fire resistance of these connections can be important. In this paper the behaviors of three common types of rigid connections in Iran under the effect of heat were studied by the use of numerical finite element methods through ABAQUS software. The models were verified by the use of an experimental model through elastic and plastic amplitudes up to collapse and during numerical results, and the effect of large deformation in the nonlinear region has also been considered. The results show that the connection with the end plate had a better performance against heat than other connections. Also reduced stiffness and lateral buckling in this connection were less than other connections. 1. Introduction Steel frames are made of beams and columns that are connected to each other by connection and connection is responsible for the transfer of forces from the beam-to-column connections and withstanding these forces. In order to calculate and design of connections many designers assume connection simple or rigid. Although these simplifications make the analysis and design remarkably easy in fact, the behavior of these connections in terms of rigidity is always a value between this limit; for instance, most of the connections that are assumed to be simple have hard rotational stiffness and rigid connections are also less flexible. This design method can be suitable for the connection modes at room temperature, but when fire occurs, the behavior of joints changes and they have greater impact on the behavior of structure and if in this situation this connection behavior is not treated properly, the design credit may extinct and cause serious damage to the structure. After the accident in which air plane crashed into the twin towers of world trade center, despite the fact that these buildings have been designed for extremely heavy loads and showed resistance against the collision of giant aircraft but acted poorly against the heat of the explosion and after that towers collapsed. In the past, many researchers have studied the effects of fire and heat on steel structures and the result of their researches was several laboratory tests but due to the cost of these tests and lack of complete laboratory facilities the use of numerical methods has been inevitable. Saedi Darian et al. [1–3] conducted experiments on simple connections with seat angles, in both welded and