Research On The Beam Buckling And Column Behavior In Steel Frame Under Fire

The poor fire-resistance ability is the main weakness of steel structure in that itsmechanical property such as strength and elastic modulus decrease severely in hightemperature. When fire occurs, severe damage or global collapse will happen to the steelstructure. In China, teat-based fire resistance design method is the prevailing fire resistancedesign method for steel structures. However, using the test-based fire resistance designmethod, but it is hard to simulate the magnitude and distribution of loads and the endrestriction conditions of the specimens in the structure. The ultimate fire resistance of thesteel structure and the fire protection measures can be determined through calculation-basedfire resistance design method. Therefore, a thorough study of the calculation-based fireresistancedesignmethodhasgreattheoreticalsignificance andpracticalvalue.In this paper, based on the problems on the fire safety design of steel structures,thefollowingresearcheshavebeenaccomplished:1,Considering the effects of static load and thermal stresses, the buckling analysis ofsteel I-section is applied. Considering the effects of stress redistribution, the stress of steelframe column in fire is studied. By building entitative model, the local buckling of steelI-sectioncolumnisstudied.2,Considering the effects of static load and thermal stresses, eigenvalue bucklinganalysis is applied to the I-section girder in the steel frames based on the finite elementmethod, and the girder's buckling modes in the fire are determined; On the basis of theeigenvalue buckling analysis, considering the material nonlinearities and geometricalnonlinearities, nonlinear buckling analysis is applied to the girder in fire. This paper alsochecks the effects of the various factors of the girder's limited temperature and fire-resistingtime.Thesefactors includerestriction conditions, themagnitudeofload,initial imperfectionsand the catenary's force due to the increasement of the girder's deflection. The influencebetween members exposed to fire and members isolated from fire are also checked in thispaper.3,Temperaturedistributionalongthehighsection isnonuniform.However,temperaturegrad plays an important part in reviewing mechanic performance of beams in fire withdifferent restriction. It is the first time to perform the experiment and simulation forcompositeslab–beaminlocalfireanddeducethermalparameters.