Analysis Of The Elastic Flexural-torsional Buckling Of Web-Tapered Variable Cross Section Beams Under High Temperature

Porfal light steel structure is getting more and more attention and application in the construction industry because of its unique advantages,such as high strength,light weight,easy installation,better shock resistance,and the advantage of rapid construction.However,due to the poor fire resistance of steel structure,with the occurrence of fire the temperature gradually increased which can lead to the material properties and mechanical properties of the structure changed significantly,severely weakened structure bearing capacity,endangering the safe use of the whole building,it is very vulnerable to damage or even collapse in the fire.Hence,the fire resistance study of steel structure has becoming a popular research direction in recent years,and it does need to improve urgently.In the thesis,refer to domestic and international relevant research results,the following aspects for the web-tapered variable cross section steel beams under high temperature had been studied.(1)It summarized the calculation method of the steel’s thermal performance parameters and mechanical performance parameters under the corresponding temperature with temperature changes.The basic assumption of calculation of the temperature inside the steel were given,and the calculation methods of the temperature inside the steel and the bucking temperature of the steel were discussed.(2)Methods of thermal conduct and the temperature changes curve inside the house under high temperature were discussed.An Cantilever beam under concentrated force at the end was taken for example,the normal stresses and shear stresses inside the web-tapered variable cross section steel beams under high temperature were studied.(3)The elastic strain energy of free torsion and warpage torsion of the web-tapered variable cross section steel beams under high temperature was studied,and the total elastic strain energy of flexural-torsional buckling was given.Further more,the formulas of the critical load for the web-tapered variable cross section steel beams under high temperature were obtained,and the formulas were proved precise through contrasted with finite element solution.(4)The flexural-torsional stability of the web-tapered variable cross section steel beams under high temperature was analyzed by ANSYS finite element software,and its results show good agreement between the finite element analytic results by ANSYS and the results obtained by the proposed method.