Simplified calculation method for the fundamental period of floating cable-stayed bridge

Abstract

It is important to estimate the longitudinal fundamental period of cable-stayed bridges accurately in the selecting of structure system and evaluating of seismic response of a cable-stayed bridge. A reverse double-mass model to compute the longitudinal fundamental period of a floating cable-stayed bridge is proposed based on the transfer paths of seismic horizontal inertia forces under longitudinal seismic. The simplified calculation formula of the longitudinal fundamental period has been developed using rigidity-based method. In addition, another simplified calculation formula was proposed based on Rayleigh method, in which the coupling of the vertical vibration of the main girder and longitudinal vibration of the bridge can be accounted together. The accuracy of the proposed calculating expressions was verified by finite element analysis using SAP2000 with ten constructed cable-stayed bridges. It indicated that the two formulae developed in this study, especially the formula based on rigidity-based method, were more reliable than single-mass model commonly used and could be effectively applied in simplified calculation of the longitudinal fundamental period of cable-stayed bridges.