Nonlinear Seismic Analysis Of The Tall-building Structures

With the development of city construction, the number of complicated tall building structures is increasing rapidly in our country, some of which go beyond the limitations of Design Codes. As we know, due to the uneven distribution of the masses and lateral-resistant members, the complicated structures are subjected to complex forces as compared with the common buildings, it is difficult for engineers to recognize the weak parts and failure modes of these complicated structures under earthquake. So the research on their behavior under the seismic action is essential. Based on an actual engineering case, this paper focused on two methods of performance-based seismic design: dynamic nonlinear analysis and static nonlinear analysis, and developed research in several aspects as following:(1) On the basis of summarizing the existing nonlinear element model of beam, column and shear wall, and based on fiber model and the concept of variable stiffness, this paper proposed a fiber-line-element model, which mainly was comprised of fiber-element in the elastoplastic region and elastic-element in the elastic region, and their stiffness matrixes were established.(2) Modal analysis: This paper used the fiber model for the beam-column element and fiber-wall model for the shear wall element discussed above, a three–dimensional nonlinear analysis model of a high-rise building was established in the nonlinear analysis and performance assessment soft called PERFORM-3D. Natural frequency and natural period of the structure's 20 order modes were obtained in modal analysis. The dynamic characteristics of the building were displayed.(3) Dynamic nonlinear analysis: This paper used the nonlinear analysis and performance assessment soft mentioned above, the time history analysis of the high-rise building was carried out under the different seismic waves (two natural waves and one man-made wave). The seismic performance of the complicated structure was assessed in conjunction with the earthquake response under different seismic waves, thus we can have a comprehensive recognition about the seismic performances of the structure.(4) Static nonlinear analysis: In this paper, static push-over analysis of an actual project was performed under three different distribution patterns of horizontal loads. Comparing the results of static nonlinear analysis with those of dynamic time-history analysis and response spectrum analysis, it can be seen that three methods are almost consistent in elasticity analysis phase, static nonlinear analysis and dynamic nonlinear analysis are almost consistent in nonlinear analysis phase. So push-over analysis can make reliable assessment to the nonlinear behavior of the structure.