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.