建筑结构抗火性能研究回顾及展望

Review and Prospect of the Study on Behavior of Structures in Fire Conditions

火灾产生的高温可使建筑结构严重破坏甚至倒塌 ,为了保证建筑结构具有足够的抗火能力 ,必须进行建筑结构抗火分析和设计。各国学者对建筑结构抗火性能进行了大量研究 ,取得了丰硕的成果。本文简要介绍火灾科学的产生及发展的进程 ,重点回顾建筑结构抗火性能研究的进展 ,进而对今后发展进行了展望。

It is well known that the most important material properties of concrete and steel, yield strength and modulus of elasticity, are reduced obviously at high temperatures, so it is not unusual that buildings are seriously damaged even collapse in fires. For example, early on the morning of November 3rd, 2003, a fire burst out in an eight-story building used for commercial and residential purposes in Xuanling Village of Zhuhui District in Hengyang, Hunan Province. The building suddenly collapsed during fire and 20 firemen were killed, more than 400 residents lost their houses. It has been reported that there were at least 25 buildings over 4 stories collapsed in fires from 1970 to now.The behavior of structures in fire conditions is very complex, because various factors need to be taken into account, such as variations of member temperature with time, temperature effects on material properties (reduction in strength and stiffness, expansion, creep), material non-linearity, geometric non-linearity, combined actions. Study on the behavior of structures in fires relates following four issues: fire exposure conditions, material properties at elevated temperatures, thermal response of a structure, and mechanical response of a heated structure. The four issues are interrelated, i.e., a description of the fire exposure is used as input to determine the thermal response of a structure. There has been a growing interest in this area in many countries, such as the USA, the UK, Canada, and Australia. Extensive test and numerical programs have been conducted, and many achievements have been obtained.This paper includes three main parts. First, the history of fire science is reviewed briefly. Some important aspects of advance in fire resistance study of structures are reviewed in the second part, including fire growing process, thermal and mechanical properties of steel and concrete at elevated temperature, analysis method for temperature fields in members subjected to fires, explosive spalling of high performance concrete in fires, structural fire tests on constructional elements, full scale fire tests of whole building structures, software development for analyzing the thermal response and mechanical response of structures subjected to fires, etc.. At last, some comments and prospects about the further studies of behavior of structures in fire conditions are provided.