TWO-MODE BASED ESTIMATION OF EQUIVALENT SEISMIC LOADS AND STATIC ESTIMATION OF DYNAMIC RESPONSE OF RETICULAR DOMES SUPPORTED BY DUCTILE SUBSTRUCTURES

摘要

Based on two predominant modes, the present study discusses a scheme to estimate equivalent static seismic loads for a steel reticular dome supported by a ductile substructure subjected to earthquake motions, followed by an application of the estimated loads to static nonlinear analysis to estimate maximum responses of the reticular dome. The proposed scheme is based on a kind of equivalent linearization method for assuming static seismic loads depending on the intensities of input earthquake motions. First, two types of equivalent static seismic loads, both changing with seismic intensity, are estimated under the assumption that the substructure yields under a prescribed base shear force: one seismic force represents mainly the effects of horizontal sway motions and the other represents mainly those of up-and-down motions due to an anti-symmetric mode stimulated by horizontal earthquake motions. Second, the proposed two types of loads are applied for proportioning the member sizes of a steel reticular dome, followed by estimation of nonlinear dynamic responses under severe earthquake motions. Third, the efficiency and accuracy of the proposed two types of seismic loads are proved through comparison between the results based on a static nonlinear analysis using the proposed seimic loads and those by time history dynamic analysis. Finally, an extension of the present scheme is suggested for further application in performance based design.