Seismic Resistance Analysis And Design Method Study On Large-span Spatial Cable Stay Structures

The large-span spatial cable stay structures composed of rigid structures and flexible cables is one new type of cable hybrid structures. With the wide application of cable stay structures in public buildings, mechanical properties are concerned, especially seismic properties. In addition, the express provisions about large-span structures are not involved in actual structural seismic code of China, which may confine the development of seismicresearch and design.Based on above all, three cable stay engineerings including the steel roof of Zhengzhou International Conference and Exhibition Center, the bridge tower of Donghai Bridge and the stadium ceiling of Jiangning Sports Center Stadium are adopted as subjects investigated in this paper. Furthermore, dynamic responses of the cable stay structures under small earthquake and intensive earthquake are explored to hold seismic properties of large-span spatial cable stay structure, to offer references for further revises about seismic code and to put forward suggestions for actual seismic design of cable stay structures.First, modal analysis on three examples is carried out to discuss self-vibration properties of cable stay structures and effects of structural parameters on dynamic performances.Thereafter, geometry nonlinearity and pre-tensions are considered in analysis, response spectrum method and elastic time-history method is respectively introduced to research under small earthquake. Mass fraction analysis, comparative analysis of combination methods and response spectrum dynamic analysis on structural parameters are carded out. Besides, dynamic responses of calculation examples are analyzed under one-dimension and many-dimensions earthquake action. Thus, the whole distortion figures, axial force figures and moment figures as well as the maximums of structural parts and displacement time-history curves of reference points. Afterwards, under intensive earthquake, geometry nonlinearity and pre-tensions as well as material plasticity are considered in analysis. Elastic-plastic time-history method is used to calculate the displacement maximums, stress maximums and displacement time-history curves of reference points under horizontal and vertical earthquake respectively.At last, results including maximums of internal forces, displacements and reference points of response spectrum method are compared with those of elastic time-history method under small earthquake. And, results including maximums of internal forces, displacements and reference points of elastic time-history method are compared with those of elastic-plastic time-history method under intensive earthquake.Main conclusions are obtained according to above analysis.(1) The cable stay structures are provided with complex dynamic performances so that the contribution of high modes is not ignored.(2) Effects of changes about pre-tensions may not affect structural performances, but effects of changes about boundary conditions do.(3) Different seismic analysis methods are selected to get inherent dynamic performance.(4) Stress values of cable stay structures are small under small earthquake so that the materials are in the elastic phase. Furthermore, it ought to choose elastic time-history method at first to do analysis.(5) The materials of cable stay structures are still in elastic phase under intensive earthquake so that plastic deformations don't happen to the structures. Thus, material plasticity may not be considered in analysis.(6) The intensive impact of earlier intensive earthquake can result in large deformation of cable stay structures, which can play an important role in dynamic damages.