COMPUTATIONAL MODEL OF NUMERICAL ANALYSIS OF THE PLANAR PRE-STRESSED STEEL TRUSSES IN FIRE

摘要

The computational model of the planar prestressed steel truss subjected to fire load is established based on the previous work about analysis of the structures at ambient temperature,according with main consideration to the response mechanism of the structure in fire. The model provides the convenience that the cables with higher tensile strength used in the structures can be set arbitrarily and stretched for more times. For the convenience of application,the EC3 constitutive model of the steel materials in fire is simplified with series expansion,and the suggested formula for each stage are unified. The fire behaviour of the pre-stressed tubular steel trusses in which the cables are set in two different ways is analyzed with the model presented here and the effect law of different factors on the bearing capacity of the structures in fire is discussed based on numerical results. It is shown that the plan of cable-setting ,value of pretension ,external loads and material grade have great effects on the behaviour and bearing capacity of the pre-stressed steel trusses in fire. Particularly,the different plan of cable-setting results in different critical temperature. The bigger external loads correspond to the smaller critical temperature,and the effect of pre-tension on the temperature is dependent on the plan of cable-setting. The conclusions can be used as basis of in-depth analysis of fire behaviour of the pre-stressed steel structures and fire-resistant design of the structures.