Response of a rigid foundation to a spatially random ground motion

Abstract

SUMMARYA method to obtain the dynamic response of an extended rigid foundation supported on an elastic half-space when subjected to a spatially varying ground motion including both random and deterministic effects is presented. The method relies on an integral representation of the response of the foundation in terms of the free-field ground motion. Numerical results for a rigid square foundation and for a ground motion characterized by a particular spatial coherence function are described. The results obtained indicate that the spatial randomness of the ground motion produces effects similar to the deterministic effects of wave passage including reduction of the translational components of the response at high frequencies and creation of rocking and torsional response components. The possibility of defining an effective apparent horizontal velocity which produces effects equivalent to those from a given spatial randomness is explored.

Site Amplification and Attenuation via Downhole Array Seismogram Inversion: A Comparative Study of the 2003 Miyagi-Oki Aftershock Sequence

“…Finally, forced vibration-based techniques based on impedance function determination in situ (Luco and Wong, 1986) that have allowed the identification of impedance and Poisson's ratios of soil profiles have been shown to yield erratic and unrealistic attenuation values. Compared to noninvasive field investigation techniques, attenuation values obtained using in situ borehole recordings may provide critical constrains on the physical mechanisms of energy absorption and redistribution in the near surface due to the minimization of uncertainty introduced in the inversion forward operator by the a priori knowledge of the total wave field at the borehole level of the site under investigation.…”

Seismic Behaviour of Isolated Rc Bridges Subjected to Asynchronous Seismic Input

“…In each position, the displacement histories change as the seismic wave propagates and changes its characteristics [6,7,11,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. These positions were chosen to consider accelerometric signals at the bridge foundations which have differences due to: (i) the distance among the generation points and (ii) the local site effects due to the soil characteristics below each generation point.…”

“…The generation procedure [6,7,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] used to obtain the input displacement histories at the bridge foundation points was discussed in Lavorato et al [11]. This procedure was implemented in MATLAB [38] as a framework of functions named GAS 2.0 -Generation of Asynchronous Signals -.…”

Reduced-order coupled bidirectional modeling of the Roll-N-Cage isolator with application to the updated bridge benchmark

“…The acceleration time histories are obtained by the procedure presented in [18,19], which relies on the spectral representation method by Shinozuka [20]. At the structuresoil contact points the auto-spectrum of the generated accelerations satisfy the well known KanaiTajimi Power Spectral Density (PSD) as modified by Clough and Penzien [21], while the crossspectra between the motions at different stations are derived from the coherency function proposed by Luco and Wong [22]. In the case at hand, a velocity of the shear waves v s = 3000 m/s and an incoherency factor α = 0.2 were adopted.…”