| As the main building material in steel buildings, steel was often used because of its good structural properties. Steel material properties were very sensitive to temperature whose elastic modulus and yield strength almost kept constant before 200 ℃, and reduced to half while the temperature reached to 500℃, and the steel would come to the plastic stage at600 ℃, and the carrying capacity would been decreased to zero at the same time. As a common damaged form to building, fire that usually last a long time made the temperature inside the building reached to 800-900 ℃ which decreased carrying capacity of building and even made it collapse, led to huge economic losses and casualties. Therefore, fire protection of steel structures has been an important part of the architectural design.At present, the analysis of the structure fire resistance of single components has been relatively mature at home or abroad, while the research on the behavior of composite steel-framed structures in fire condition, is extremely complex. Therefore, it is full of practical significance to study the behavior of composite steel-framed structures in fire conditions on the basis of existing research results at home and abroad. How to test the spatial temperature distribution in the fire process is a primary problem in steel fire resistance design. Currently the standard temperature curve ISO834 is often used to represent to the real spatial temperature distribution which is quite different from it. Different fire load and different architectural form may lead to great difference between the trend of temperature distribution and numerical value which will be directly effect to the structure mechanics response in the subsequent heat-structure coupling analysis. In addition, it is assumed that the temperature is uniform or linear distribution along the beam section, which is consistent with the actual situation. For the above, several work has been done as follow:1.It has been summarized that the research status of steel structure fire resistance, and compared the physical properties and thermal parameters of steel and concrete among various countries systematically. The nonlinear properties of steel at high temperature have been Considered while the thermal conductivity, specific heat, expansion coefficient and other parameters are referred to foreign relevant standards, and combined the actual situation to determine their value that are required in the process of heat-structure analysis in this paper.2. A office building in fire conditions is established by FDS which is used to simulate fire behavior including smoke flow, fire development, indoor temperature field.etc. It has been analyzed that effects of vents on the indoor temperature field in fire, obtained an indoor temperature rising curves which is determined as temperature load applied to steel frame structures.3. The software ABAQUS is used to calculate the temperature field of a steel component which is applied different temperature load including temperature curves obtained from FDSand standard temperature curve, compared two analysis results and made conclusions in the end. The actual temperature field in the structure components is regard as temperature load applied to steel frame structures in heat-structure coupling analysis. The variation of beam span deflection is achieved to infer the structure fire resistance time. In addition, the stress distribution of the overall frame and concrete floors are analyzed. |
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