Performance Of Steel Portal Frame Structure With Local Buckling Of Tapered Members

With the increasing widely application of steel portal frame structure with tapered members, it is getting more important to study on its performance under static and seismic loading. The web with high width-thickness ratio is generally applied for tapered H-section members in portal frame, where local buckling may occur and the post-buckling strength is desired to be applied. Many studies have examined the buckling behaviors of tapered H-section members under monotonic static loading or cyclic loading. But few researches on the static and seismic performance of steel portal frame with local buckling of tapered members with thin web are focused.Based on stability theory and nonlinear finite element (FE) method, ANSYS finite element models (FEM) are presented, where shell 181 is adopted and geometric and material nonlinear is taken into account, as well as initial geometric imperfection.Whole process parameter analysis of steel portal frame with tapered H-section members under static loading has been performed. According to the results, such as load-displacement curves, elastic load-carrying capacity, ultimate load-carrying capacity, the local deformation, the development of plasticity etc, the effects of parameters including initial geometric imperfection, web width to thickness ratio, span, height and slope of portal frame on performance of steel portal frame are discussed, and the failure mechanism of steel portal frame considering the post-buckling behavior of thin-walled plates is studied. And then ultimate load-carrying capacity of steel portal frame under different load case is compared to determine the worst load case.After that, Time history analysis is adopted to analyze the response of steel portal frame with different load level under strong earthquake, and the whole failure process of steel portal frame under seismic loading is achieved. Since three portal frames in different span are chosen and their web width to thickness ratio is varied to compare the different responses of portal frame under strong earthquake, the effects of web width to thickness ratio on whole deformation, local deformation and plastic strain development of portal frame are discussed. Finally, the seismic performance of steel portal frame is estimated according to the plastic drift angle limit.