Improved factored modal combination method for evaluating in-plane seismic demands of latticed arches

摘要

An improved factored modal combination method is developed for evaluating the in-plane seismic demands of latticed arches. In the method, an improved equivalent static earthquake load profile (ESELP) is proposed and expressed as a combination of several modal ESELPs. Two factors, an extended modal combination factor and a modal load modification factor, are proposed and used to establish the modal ESELPs, in which higher mode and geometrical nonlinear effects are taken into account. A set of improved ESELPs are established by combining the modal ESELPs of the selected modes that contribute significantly to the structural response. The structural demands are obtained from the envelope result of nonlinear pushover analyses using all the improved ESELPs. Three circular latticed arch models and two non-circular latticed arch models are built, and 30 seismic excitations are selected to investigate the applicability of the proposed method. The results show that, for latticed arches whose number of significant modes is less than or equal to three, the proposed method provides relatively high accuracy in the estimation of seismic demands. The mean errors of the seismic demands given by the proposed method are relatively low compared with those obtained from the factored modal combination method and the extended modal pushover analysis.