Inelastic Response of R/C Bridges Under Horizontal and Vertical Earthquake Motions

摘要

The relative importance of the vertical component of ground motion on the inelasticresponse of R/C highway bridges is investigated. Particular emphasis is placed on modelingof the deck and piers to account for. complex loading histories under combined verticaland horizontal earthquake motions. Analyses of several columns under non-proportionalvarying axial load indicate the importance of this type of loading on the inelastic behaviorof R/C members. Furthermore, the results show that phasing of the axial load significantlyaffects properties of R/C columns that are very important in seismic design.Analyses of actual bridges indicate that, in general, the vertical motion will increasethe level of response and the amount of damage sustained by a highway bridge. Variationin the strength and the stiffness of the columns, caused by varying axial load due tovertical motion, results in an increase in forces and moments in these elements and theirfoundation. Hysteresis loops are also affected when vertical motion is considered andmore damage is sustained by the columns. Tensile axial load caused by the vertical motionreduces the shear capacity of the columns and the possibility of shear failure prevails.Finally, the magnitude and nature of forces induced by the vertical motion on the abutmentsand foundations are very different compared to cases where vertical motion is notconsidered. Therefore. it is important to consider this component of ground motion inthe design of highway bridges, especially for those located in regions near seismic faults.