The Finite Element Analysis Of Aluminum Beams In Fire Conditions

Aluminum structure has been more and more applied in all areas of construction projects with its unique advantages, but its poor fire resistance is also worthy of our concentration. The mechanical properties of the aluminum alloy is very different in high temperature and in room temperature-the strength and rigidity of the aluminum alloy is significantly decreased with the temperature increasing and the yield strength and elastic modulus is reduced to zero when the temperature is increased550℃.It may occur serious damage and may even lead to the entire collapse when the aluminum structure under fire. Therefore, the fire-resistance of the aluminum alloy structure is given more and more attention.As we all know, the behavior of beams under fire in whole structures is very different with the simply supported beams. But it is too complex to analyzed the beams as a whole with the around members, so it is suitable for analyzing aluminum beam with boundary condition instead of surrounding members. Summarizing the current research, there is a lot research literature on aluminum beams at room temperature but very little research literature under fire,however, there is no report on the analysis about the behavior of aluminum beams for several conditions. Simply supported, hinged, clamped and so on as extreme boundary conditions of aluminum beams in the engineering, summarizing the development of aluminum beams under these conditions has a very important significance and provides a very important theoretical reference for the later study of the aluminum beams.Based on the finite element software ANSYS, this paper presents the numerical simulation, compared fire behavior of the aluminum beams at several different extreme boundary constraints under fire. Then, discusses the critical temperature in different criterion. Furthermore, some parameters analysis are described, such as the load ratio, beam span and the load type.From these works, it is concluded that the development process of the aluminum beams at these boundary conditions under fire is completely different. For example, the deformation of the aluminum beam has a sudden increase with the temperature increasing when there is no axial force, but the deformation of the aluminum beam increases slowly with the temperature increasing when there is axial force. It indicates that axial constrain has significantly affected on the deformation and the force development of the aluminum beams. The critical temperature and the limit temperature is different under different criterion. the critical temperature and limit temperature the fire-resistance, the critical temperature and limit temperature is highest when fully consider the pulling force of the aluminum beams.Through the finite element numerical simulation, this paper also provides the flexural-torsi onal buckling of the aluminum beams at room temperature and high temperature, then analyzes the influence of the load ratio, load type and geometric imperfections on the critical load and critical temperature. Through analysis, it shows that geometric imperfections has smaller influence than the load ratio. The mid-span deflection and angle increase slowly with the increase of temperature, then suddenly increased at a particular temperature.