Finite element analysis of portal frame under fire condition (2016)

The steel structures are widely used in modern industrial factory due to its advantages such as high strength, good plasticity, good sealing property, and short construction period. However the poor fireresistance ability is the most significant weakness of the steel structures. The steel structure workshop is very easy to collapse and damage as long as the fire occurs. So it is very meaningful to study the collapse of steel structures under fire conditions. In this paper, one storey industrial factory buildings with light steel is used as an example and the influence of the intermediate support on the collapse of the steel structure is analyzed by using the finite element software ansys15.0. The damages of the structures are analyzed under the same temperature and load size of the structure. The results show that when the intermediate support is added in the workshop, it can effectively prevent the rapid collapse of the structure and delay the failure time of the structure. Therefore, increasing the intermediate support can effectively improve the overall stability of the structure and we should increase the intermediate support to the workshop in engineering practice. KEYWORD: industrial factory, finite element, intermediate support, collapse   0 10 345log 8 1 T T t    4th International Conference on Mechanical Materials and Manufacturing Engineering (MMME 2016) © 2016. The authors Published by Atlantis Press 665 2 FINITE ELEMENT ANALYSIS MODEL. The model is a portal frame with 70 meters long, 30.8 meters wide and the column spacing is 7 meters. The floor plans of the factory with and without intermediate support are respectively shown in Figure 1 and 2. The column support layouts of A/B/C axis are shown in Figure 3. Fig. 1 Plan layout of workshop with intermediate support Fig. 2 Plan layout of workshop without intermediate support Fig. 3 Supporting layout diagram between pillars of A/C/E axis Dead load of roof is 0.3 KN/m2, roof live load 0.5 KN/m2 and basic snow pressure 0.6 KN/m2. Q345 H type steel is used in Column, beam, intermediate support and other components. The section size of the column and the intermediate support is 500×300×10×12, and the cross section size of the beam is 500×250×10×12. The Lateral bracing is round steel with diameter of 20 and the inclined rod is a steel pipe with diameter of 140 and wall thickness of 4. The model uses ISO834 standard heating curve. The density of steel is 0.00785g/mm3.The specific heat capacity of steel varies with temperature, as shown in Figure 4.The elastic modulus of steel varies with temperature, as shown in Figure 5.The Poisson ratio is 0.3. The coefficient of thermal expansion is 1.4×10-5m/(m·°C).The heat transfer coefficient of steel varies with temperature, as shown in Figure 6.The stress-strain relationship of steel at different temperatures is shown in Figure 7. Fig.4 The curve of specific heat capacity with temperature Fig.5 The curve of elastic modulus of steel with temperature Fig. 6 The curve of thermal conductivity of steel with temperature Failure criterion of steel structure: (1) When the program do not restrain, the component should be judged invalid. (2) The component should be judged invalid when the rate of the deformation bases on: