NUMERICAL INVESTIGATION OF PRESTRESSED I-BEAM IN CASE OF FIRE

摘要

This paper focuses on the effects of prestress and loads on structural fire response up to failure of bare prestressed steel beams (PSB).Simply supported PSB with external tendons were analyzed.The thermal and structural analysis of PSB were accomplished by the commercial program package ANSYS.The thermal response was carried out under three-side fire exposure of standard fire of ISO834.Two key parameters, ratio of prestress and ratio of load, were taken into account.The results showed that the load ratio played an important role in the fire resistance of PSB.The PSB can obtain the maximum fire resistance when LR is 0.35 and PR is more than 0.45.The general trend is that the fire resistance decreases with the load ratio increasing.The stress in the cable strand finally approaches to zero when PSB fail at high temperature.And the ratio of prestress showed very limited influence on the fire resistance defined according to the limited bearing capacity.The high prestress could delay failure of the cable tendons due to being loose and decreases the deflection of the steel beam at the beginning of the standard fire.