Examinando por Autor "Restrepo, Doriam"
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Ítem A novel simple procedure to consider seismic soil structure interaction effects in 2D models(SPRINGER, 2014-09-01) Diego Jaramillo, Juan; David Gomez, Juan; Restrepo, Doriam; Rivera, Santiago; Mecánica AplicadaA method is proposed to estimate the seismic soil-structure-interaction (SSI) effects for use in engineering practice. It is applicable to 2D structures subjected to vertically incident shear waves supported by homogenous half-spaces. The method is attractive since it keeps the simplicity of the spectral approach, overcomes some of the difficulties and inaccuracies of existing classical techniques and yet it considers a physically consistent excitation. This level of simplicity is achieved through a response spectra modification factor that can be applied to the free-field 5%-damped response spectra to yield design spectral ordinates that take into account the scattered motions introduced by the interaction effects. The modification factor is representative of the Transfer Function (TF) between the structural relative displacements and the free-field motion, which is described in terms of its maximum amplitude and associated frequency. Expressions to compute the modification factor by practicing engineers are proposed based upon a parametric study using 576 cases representative of actual structures. The method is tested in 10 cases spanning a wide range of common fundamental vibration periods. © 2014, Institute of Engineering Mechanics, China Earthquake Administration and Springer-Verlag Berlin Heidelberg.Ítem SH Wave Number Green’s Function for a Layered, Elastic Half-Space. Part I: Theory and Dynamic Canyon Response by the Discrete Wave Number Boundary Element Method(SPRINGER BASEL AG, 2014-09-01) Restrepo, Doriam; David Gomez, Juan; Diego Jaramillo, Juan; Mecánica AplicadaWe present a closed-form frequency-wave number (? – k) Green’s function for a layered, elastic half-space under SH wave propagation. It is shown that for every (? – k) pair, the fundamental solution exhibits two distinctive features: (1) the original layered system can be reduced to a system composed by the uppermost superficial layer over an equivalent half-space; (2) the fundamental solution can be partitioned into three different fundamental solutions, each one carrying out a different physical interpretation, i.e., an equivalent half-space, source image impact, and dispersive wave effect, respectively. Such an interpretation allows the proper use of analytical and numerical integration schemes, and ensures the correct assessment of Cauchy principal value integrals. Our method is based upon a stiffness-matrix scheme, and as a first approach we assume that observation points and the impulsive SH line-source are spatially located within the uppermost superficial layer. We use a discrete wave number boundary element strategy to test the benefits of our fundamental solution. We benchmark our results against reported solutions for an infinitely long circular canyon subjected to oblique incident SH waves within a homogeneous half-space. Our results show an almost exact agreement with previous studies. We further shed light on the impact of horizontal strata by examining the dynamic response of the circular canyon to oblique incident SH waves under different layered half-space configurations and incident angles. Our results show that modifications in the layering structure manifest by larger peak ground responses, and stronger spatial variability due to interactions of the canyon geometry with trapped Love waves in combination with impedance contrast effects. © 2014, Springer Basel.Ítem Virtual topography: A fictitious domain approach for analyzing free-surface irregularities in large-scale earthquake ground motion simulation(WILEY-BLACKWELL, 2014-11-16) Restrepo, Doriam; Bielak, Jacobo; Mecánica AplicadaThis paper presents a numerical scheme based on a fictitious domain framework for the numerical modeling of earthquake-induced ground motion in the presence of realistic surface topography of the Earth's crust. We show that by adopting a non-conforming octree-based meshing approach associated with a virtual representation of the surficial irregularity, we can obtain accurate representations of ground motion. From the computational point of view, our methodology proves to be also efficient, and more importantly, it allows us to preserve the salient features of multi-resolution cubic-shaped finite elements for wave propagation applications. We implemented the non-conforming meshing scheme for the treatment of realistic topographies into Hercules, the octree-based finite-element earthquake simulator developed by the Quake Group at Carnegie Mellon University. We tested the benefits of the strategy by benchmarking its results against reference examples, and by means of numerical error estimate analyses. Our qualitative and quantitative comparisons showed a close agreement between our numerical results and the reference results, and also, that the order of convergence of the displacement field is preserved in the presence of surface topography. Moreover, this performance was obtained by using the same mesh refinement techniques with cubic elements as in traditional flat free-surface simulations. © 2014 John Wiley & Sons, Ltd.