Fire Resistance Study On Restrained Steel Beams By Considering Creep Effect

Significant creep deformation occurs in steel when subjected to elevated temperature and load action, which causes lager impact on the deformation and load capacity of steel beams in fire. Creep has a great effect on restrained steel beam considering catenary action with a long fire duration and high critical temperature. At present, the fire-resistant code of each country, which mainly based on isolated members, have not proposed effective method to evaluate fire resistant performance of restrained steel beam, let alone taking creep at high temperature into consideration.By discretizing the section of steel beam and considering creep, an improved analysis method to study restrained steel beam was proposed based on current theory. The accuracy of the established method was verified through the comparison between the simulated results and test results. The study indicates that creep has great effect on restrained steel beam. Five kinds of creep model commonly used were compared. By comparing the results of the analysis in different creep model, it can be seen that a better agreement was found between test data and analysis results by using Norton creep model.Finite element analysis model for restrained steel beam was established by ANSYS considering creep. Comparison with test data shows that using the curves of stress-strain inclusion of creep can’t simulate the creep in restrained steel beam. The best agreement was found between test data and analytical results by using Poh model of stress-strain curves considering creep.Parametric study was conducted by employing the validated model. The study indicated that the variation of rotational restraint stiffness, yield strength, heating rate and span-depth ratio et al have an obvious influence on critical temperature. Those parameters above are not considered in current fire resistance design standard on restrained steel beam. By doing regression analysis on the results of parametric study, a simplified calculating method is presented to calculate fire resistance of restrained steel beam considering creep effect.