We investigate the role of topographic irregularities on the amplitude and phase of earthquake ground motion by means of numerical analysis performed with the open-source finite element software OpenSees. We first perform a verification of the numerical model for simple 2D topographic features and harmonic motions, against: (1) numerical solutions available in the literature and (2) boundary element method analyses utilizing a code specifically developed for this study. The analytical and boundary element solutions provide verification of the OpenSees simulations for simple geometries excited at a single frequency. OpenSees, by contrast, can handle irregular geometries and broadband ground motions. We then perform a comprehensive parametric investigation for a bridge crossing a 260m-deep canyon. Our analyses are performed considering homogeneous stiff rock site conditions to emphasize the role of topographic irregularities only, without the influence of soil/rock layers of varying stiffness. Results are presented in terms of phase angle and amplitude modifications for a few critical locations along the bridge axis, corresponding to the foundations of the central piers of the bridge. We also process results by using cross-correlation measures, showing that 2D topographic irregularities can strongly modify strong ground motions.

INFLUENCE OF TOPOGRAPHIC IRREGULARITIES ON THE AMPLITUDE AND PHASE OF STRONG GROUND MOTIONS

Durante M. G.;Ausilio E.;Zimmaro P.
2018

Abstract

We investigate the role of topographic irregularities on the amplitude and phase of earthquake ground motion by means of numerical analysis performed with the open-source finite element software OpenSees. We first perform a verification of the numerical model for simple 2D topographic features and harmonic motions, against: (1) numerical solutions available in the literature and (2) boundary element method analyses utilizing a code specifically developed for this study. The analytical and boundary element solutions provide verification of the OpenSees simulations for simple geometries excited at a single frequency. OpenSees, by contrast, can handle irregular geometries and broadband ground motions. We then perform a comprehensive parametric investigation for a bridge crossing a 260m-deep canyon. Our analyses are performed considering homogeneous stiff rock site conditions to emphasize the role of topographic irregularities only, without the influence of soil/rock layers of varying stiffness. Results are presented in terms of phase angle and amplitude modifications for a few critical locations along the bridge axis, corresponding to the foundations of the central piers of the bridge. We also process results by using cross-correlation measures, showing that 2D topographic irregularities can strongly modify strong ground motions.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11770/292876
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