With the development of the technology of the buildings

many new types of the buildings are beyond the current fire safety standards

which have to be designed by the performance based concept.In this paper

the performance based fire safety design method is adopted in the analyses of a composite steel framed building

where many large spaces are located.The evacuation model of the building for simulating the evacuation of people in fire condition is established and the evacuation time is researched through the computer simulation.Considering the shortage of current standards about the fire safety design of the buildings with large space

the temperature increasing of the air in the large space is studied by using the FDS software.Unlike the conventional fire resistant design method based on experiment

the temperature increasing of the structural members is analyzed by the calculating method

which can give more accurate results.Comparisons of the results of the evacuation time and the temperature increasing of the air obtained in the paper to the results based on the current standards show that the latter is more conservative.At last

based on the analytic results and the corresponding specifications of the fire safety design code

the rational data of the evacuation time

temperature increasing of the air and the structural members are determined.