Analysis Of The Fire Resistance Of Steel Structures Exposed To Temperature Field Based On FDS Simulation

Large-space buildings can not only provide comfortable environments, but also meet various functional needs, so they are widely used in recent years.However, steel structure behaves poorly in fire-resistance, since it is easy to get damaged in case of fire. Recent studies of fire-resistance mainly focus on common indoor fire, while the temperature field of large-space fire is different from that of common indoor fire, and the damage of a single member at high temperature does not mean that the whole structure has reached its limit. Thus it is necessary to study the overall fire-resistance performance of steel structure used in large-space buildings under different fire scenarios. This thesis takes a plane frame structure and a space grid structure as research objects, and adopts the numerical simulation technique to study the temperature field distribution and the overall fire-resistance performance of steel structure used in large-space buildings. The main contents of this paper are:(1) The material properties of steel at high temperature are summarized, and the thermal parameters and mechanical parameters are determined for further analysis. Two methods used for the calculation of steel member temperature distribution are introduced, and the results are compared to determine the method adopted in this paper.(2) A plane frame structure warehouse fixed fire model and a space grid structure stadium expansive fire model are built through FDS software. The temperature fields and the fire processes under different fire scenarios are analyzed in order to discuss how they are influenced by the fire position or igniting point.(3) The result simulated by FDS is taken as the temperature field of the fire, and the indoor temperature field is divided into appropriate zones. Then the ANSYS transient thermal analysis method is adopted to calculate the temperature of each member or cell of the two structures under different fire scenarios at different times.(4) The temperature of each member or cells of two structures at different times is imposed to the structures as thermal load, and the ANSYS thermal-structural analysis method is used for the nonlinear whole-process numerical simulation of the structural responses in different fire scenarios, and their fire-resistance properties and fire limits are analyzed. Finally, the fire-resistance design method based on the structural performance is adopted to analyze the influence of fire-retardant coatings with different thickness on the structure’s fire-resistance property.