| With the development of China’s economy, more and more steel buildings come into our lives. Because of the advantages of the steel structure itself, the proportion of high-rise residential steel structure and the large span buildings are increasing year by year. However, there is a fatal weakness of steel material which it is nonflammable material but the poor performance of fire. As the temperature reaches600"C, steel components will basically lost carrying capacity. If the important beams or columns lost bearing capacity, the steel structure will rapidly collapse. However, the general scene of the fire’s temperature will be above800℃, the steel structure must take some fire prevention measures.There are a variety of steel structure fire protection measures, and the most suitable fire protection measures will be found in the dissertation by comparison of the advantages and disadvantages of the different types of fire prevention measures. Based on the powerful ANSYS software as the platform, an object, which is the main beam GL2of the steel frame structure of Building4in Gaoguanling Real Estate District4in Anshan City, is selected to make a numerical analysis on fire performance by using finite element method (FEM). The thermal-structural coupling method is used for the FEM, and the temperature field of the H-shaped steel beams under standard temperature conditions is obtained. At the same time, the temperature field used as the body load is applied in the subsequent analysis of the structure for the calculation of the fire resistance time. In order to be universal, two kinds of boundary conditions are selected:one case is a fixed end and a simply supported end; the other is both fixed ends, to analyze the influence on ultimate fire resistance time of the developed beam under the given boundary conditions. The numerical results show that the ultimate fire resistance time for the beam with two fixed ends is much less shorter than the other.According to the comparative analysis of the steel structure fire protection measures, the thick fire retardant is selected as a fire-resistant protective layer for the H-shaped steel beams. Through the refractory finite element analysis, the influence for the thick fire retardant coating to the limit refractory time of the steel members is obtained. The main parameters of the H-shaped steel beam with a thick fire-resistant coating such as the density, specific heat and thermal conductivity are numerically analyzed for the influence of the element fire performance. The limit refractory time curves for the various beams are obtained. The results show that the fire-resistant properties for the beam with two fixed ends are poorer than that with one fixed end and one simply supported end in the case of the same thermal parameters as using thick fire retardant coating. The fire-resistant performances are linearly increased with increment of the coating thickness, coefficient of heat conductivity and density of the material, and decreased in accordance with the hyperbola curve with increment of the specific heat. Based on the variation regulation of the thermal parameters and limit refractory time, a formula for calculating the required thickness of different fire-resistant coating in certain refractory time is derived. The developed formula can be used as a reference to select the safe and effective paint coating in the thick type of fire retardant paints. |
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