Experimental Investigation On The Fire Resistance Performance Of T-shaped Steel Special-shaped Columns

In view of the advantages of high carrying capacity, small cross-section, goodperformance of seismic resistant and beautiful architecture, the application of steelspecial-shaped column is more and more widely. But under the action of the fire, thebasic mechanical performance index fell sharply. Additionally, the steel special-shapedcolumn is open thin-walled bar with irregular cross section, compared with steelreinforced concrete special-shaped columns, its fire area is large and refractoryperformance is poor. It most likely lead to the collapse of the entire structure, once steelspecial-shaped columns fire, which is bound to cause heavy losses, so the study of fireresistance about steel special-shaped columns has important significance.This paper selected typical T-shaped steel special-shaped columns as the researchobject, it revealed the impact of load eccentricity and the welding residual stress on theT-shaped steel special-shaped columns through fire tests and ANSYS simulation. Thespecific studies and results are as follows:1. First，five welded T-shaped steel special-shaped columns were tested in fireunder the standard temperature curve of SIO0834. A T-shaped steel special-shapedcolumn was applied axial load, and the other four were applied the eccentric load ofdifferent eccentricity, then according to the changes of eccentricity, the criticaltemperature, lateral displacement, axial displacement, variation of cross-sectionaltemperature field were analyzed. The test results show that:(1) In the fire test, thetemperature of each T-shaped steel special-shaped column is not evenly distributed, thetemperature of the web1is highest, and flange3the lowest, the difference is about50℃.(2) Regardless of the size of the eccentricity, the vertical displacement of eachT-shaped steel special-shaped column is consistent with the change of temperature.(3)Regardless of the size of the eccentricity, the destruction forms of TZ1-TZ5are theflexural torsional buckling.(4)The critical temperatures of T-shaped steelspecial-shaped columns decrease with the increase of eccentricity under the constantaxial load.(5) Under the constant axial load, the fire-resistant times of T-shaped steelspecial-shaped columns became shorter constantly with the increasing of bendingmoment, but its effect on fire-resistant time became smaller and smaller. 2. Measure the welding residual stress of T-shaped steel special-shaped columns,analyze the law of welding residual stress distribution in T-shaped steel special-shapedcolumns, and then provide the theoretical basis and data for this paper to analyze theeffect of welding residual stress on fire resistance performance of T-shaped steelspecial-shaped columns.3. The finite element numerical simulations of fire resistance performance aboutT-shaped steel special-shaped columns were carried out by the ANSYS finite elementanalysis software, then compared with the experimental results in Chapter3. Accordingto changes of eccentricity, the N-M variation curves of T-shaped steel special-shapedcolumns were determined.Specific conclusions are as follows:(1) Under the constantaxial load, the critical temperatures of T-shaped steel special-shaped columns decreasewith the increasing of eccentricity, and greater the axial pressures of T-shaped steelspecial-shaped columns are, more obvious the influence of eccentricity on the criticaltemperature.(2)When the critical temperatures were same, the axial pressure ofT-shaped steel special-shaped columns decreased with the increasing of bendingmoment, basically linear decreasing trend it showed.(3) When the critical temperatureswere different, the reduced rates of axial pressure of T-shaped steel special-shapedcolumns were the same with the increasing of bending moment.4. Determine the impact of the welding residual stress on fire resistanceperformance of T-shaped steel special-shaped columns by numerical simulation.(1)Under the same load conditions, critical temperature of the T-shaped steelspecial-shaped columns which welding residual stress is applied on is lower than theones which have no welding residual stress.(2) When the loading ratio of T-shaped steelspecial-shaped columns is relatively low, under the same conditions, the difference incritical temperature between T-shaped steel special-shaped columns which weldingresidual stress is applied on and ones which have no welding residual stress is about20℃-40℃; When the loading ratio of T-shaped steel special-shaped columns isrelatively high, under the same conditions, the difference in critical temperaturebetween T-shaped steel special-shaped columns which welding residual stress is appliedon and ones which have no welding residual stress is about50℃-150℃.