Abstract

JARA DIAZ, Manuel; HERNANDEZ BARRIOS, Hugo  and  ALVAREZ MOSQUEDA, Otilio. Effect of seismic vertical motions on bridges. Ing. sísm [online]. 2022, n.spe108, pp.79-107.  Epub Mar 10, 2023. ISSN 0185-092X.  https://doi.org/10.18867/ris.108.602.

Typically, the seismic analysis and design of structures considers exclusively the seismic horizontal components, and only in certain cases, the vertical movement is also incorporated in the analysis. A common way to include the vertical seismic demand is by means of a vertical design spectrum having ordinates equal to the ordinates of the horizontal design spectrum reduced by a factor less than one. However, observations from earthquake records have revealed that vertical component of ground motions is especially significant for high frequency content and sites located close to the epicenter, where the vertical acceleration can be even greater than the horizontal components, driving to the conclusion that the reduction of the horizontal spectra as a way to represent the vertical seismic demand is not appropriate. The first aim of this study is to assess the importance of the vertical component by conducting a parametric study of 100 records associated to the subduction process, obtained from the Mexican Strong Motion Database. The acceleration time histories were recorded at distances less than 60 km and for magnitudes larger than 5.0. The second part is focused on the influence of the horizontal and vertical components of ground motions on the structural response of bridges during their staged construction process and also of completed bridges by means of a nonlinear analysis.

Keywords : vertical acceleration; vertical/horizontal acceleration ratio; vertical response spectra; influence of vertical seismic movement on bridges.

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