【作者】 杨帆；

【导师】 钱稼茹；

【作者基本信息】 清华大学 ， 土木工程， 2010， 博士

【摘要】 大空间钢结构和钢框架结构是体育馆、机场、厂房、仓库、办公楼等人员或物资密集建筑常用的结构类型。钢材的耐火性能较差,此类建筑结构在火灾中容易损伤破坏甚至倒塌。本文通过理论分析和数值计算,研究此两类钢结构在火灾过程中的受力性能、支座反力、损伤发展等,以期为这两类钢结构的抗火设计提供参考。本文主要研究工作及取得的主要成果如下:(1)对大空间钢结构火灾中构件温度分布进行理论分析,提出计算构件温度分布的简化方法,并将该方法发展至火灾冷却阶段。模型计算表明,该方法具有良好精度。提出钢框架结构火灾升温及冷却阶段构件温度场分段成比例的简化计算方法,给出方法的适用范围,分析构件尺寸及受火方式的影响。(2)对大空间钢结构的工程实例进行火灾升温及冷却过程数值模拟,得到其火灾过程中构件屈服发展情况、内力重分布规律,支座反力变化、构件及结构变形、结构破坏形态等结构性能。对钢框架结构进行整体有限元模拟计算,与已有实验结果对比分析,分析其火灾全过程整体受力变形性能及支座反力的发展规律,并提出相关设计建议。(3)提出钢框架结构火灾下基于承载力的四阶段损伤评估方法,并对火灾发生位置、荷载分布、结构尺寸、构件受火情况等影响因素进行系统分析。给出构件屈服、构件破坏、结构局部或整体破坏、极限承载四个损伤阶段的标定值及适用范围。基于四阶段损伤评估,提出钢框架结构火灾损伤实时评估方法,火灾下钢框架结构允许入内扑救的极限温度和时间估算方法,以及钢框架构件防火层厚度计算方法。(4)采用三维精细有限元模型进行钢框架结构火灾下受力性能的计算分析,根据三维模型和二维模型计算结果的综合比较,修正四阶段损伤标定值。编制了《钢框架结构火灾下性能计算辅助建模及分析软件》,该软件能完成钢框架结构参数输入-建模-热学计算-力学计算-结果处理的全过程。更多还原

【Abstract】 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.更多还原