Numerical Simulation And Damage Assessment Of Large-space And Steel Frame Structures On Fire

Large-space steel structures and steel frame structures are commonly used in stadiums, airports, factories, warehouses, office buildings, etc. Weak fire resistance of steel material makes such a structure easy to damage or even collapse on fire. In this thesis these two structures are selected to study their performance, support reactions, damage development and other aspects on fire through theoretical analysis and numerical simulation in order to provide informations for fire-resistant design. The main research works and the main achievements are as follows.(1) Theoretical analysis of the temperature distribution of the structural components on fire is performed, and a simplified method of calculating component temperature distribution is proposed. Developing of this method in fire cooling phase is carried out. Calculating results of models show good accuracy of the method. A simplified method for calculating the component temperature field of steel frame in the phase of temperature rising and in the phase of cooling on fire is proposed. The applicable limit of the method is given. The influence of component sizes and fire parameters is studied.(2) Simulation of large-space steel structure projects and steel frame structures in fire rising and cooling process is conducted. Their structural behavior, such as yield of components, redistribution of internal force, reaction forces of supports, deformation of components and structure, damage patterns of structure, are obtained. Finite element simulation and experimental contrast for steel frame structure is executed to analyse the law of structural properties and deformation performances on fire. Fire-resistance design recommendations are presented.(3) A strength based four stage damage assessment method of steel frame structures on fire is proposed. Influence of various factors, such as fire location, fire condition, loading condition and structural dimensions, is systematic analysed. Calibrating values and applicable fields of the four damage stages, i.e., yield of components, damage of components, damage of partial structure or total structure and ultimate bearing capacity, are presented. Based on the four stage damage assessment method, on time damage assessment method of steel frame structures on fire, calculating method of the up limite temperature or up limite time for fighting the fire, calculating of the fire protection layer thickness for steel frame structure components are proposed.(4) A more refined three-dimensional finite element model is developed to study the behavior of steel frame structures on fire. Based on the comprehensive comparison of the three-dimensional model results and the two-dimensional model results, calibrating values of the four damage stages are modified. A software called "Assistant Modeling and Behavior Analysis for Steel Frame Structures on Fire"is developed. The software has ability to complete the overall process of parameter input - modeling - heat calculation - mechanical calculation - result output.