Analysis of the frictional slip between a layer and a half-space

The numerical analysis of a boundless elastic layer on an elastic halfspace with different material properties under the effects of an uniform surface pressure and a cyclic tangential surface force is presented. Frictional contact conditions are assumed. The study is focussed on the evaluation of the maximum amplitude of the tangential load which produces localized slip between the two regions during the first load cycle but not the subsequent ones. The more simple limit for which no slip exist even for the first cycle is also establishe

Respuesta dinámica de cimentaciones considerando condiciones de contacto con fricción

X Congreso Nacional de Ingeniería Mecánica, celebrado en Madrid en 1992En el presente trabajo se estudia la respuesta en el tiempo de una cimentación superficial situada sobre un semi-espacio, cuando un tren de ondas incide sobre ella. La interacción suelo-cimiento se considera no lineal con posibilidad de separación y deslizamiento, habiéndose supuesto fricción del tipo Coulomb. El algoritmo que se presenta se basa en el Método de los Elementos de Contorno en el dominio del tiempo, y resuelve, para cada intervalo lineal en el que las condiciones de contorno son constantes, el problema difractado.In the present work the time response of a sourface foundation on de half-space when a wave train acts on it, is studied . Non-linear soil-structure interaction. with uplifl .sliding and Colulomb type friction, is considered. The algoritm presented is based on the time domain Boundary Element Method fonnulation, solving the diffracted problem for the differents time steps where the boundary contition are constants

El uso de una solución fundamental compuesta para el cálculo de rigideces de cimentaciones mediante el método de los elementos de contorno

El problema de las rigideaes dinámicas de cimentaciones enterradas puede ser abordado por diversos métodos analíticos y numéricos más o me nos aproximados. Se presenta en primer lugar la formulación dinámica del Me todo de los Elementos de Contorno para este tipo de problemas. Se estudia cómo el empleo de una solución fundamental compuesta disminuye el número de términos despreciados al truncar la discretización de la superficie libre.- Se estudian algunos de los valores de las rigideces estáticas y dinámicas,- obtenidos con la solución fundamental compuesta, y se comparan con los - -- correspondientes a la simple. Se apr cia que en la mayor parte de los casos, con la solución compuesta, se produce una reducción del error debido al - - truncamiento en la discretización de la superficie libre del suelo

Model for the seismic analysis of arch dams including interaction effects

A three-dimensional boundary element model for the seismic analysis of arch dams is presented. The soil and the dam are assumed to be viscoelastic domains the former being boundless. The water is assume to be compressible subject to small amplitude motions. The three domains are discretized into B ."E. in a single model which includes a rigurous representation of the dam-foundation rock interaction, the water-foundation rock interaction and the traveling wave effects. The response of an arch dam (The Morrow Point dam) to harmonic waves propagating vertically is studied. The important influence of the abovementioned interaction and traveling wave effects is clearly shown by computed results. These results are in contrast with sorne obtained by other authors using a F.E. model

A 3D Numerical Mode for HST Induced Vibrations

A general numerical model for the analysis of soil motion due to high-speed train passage and effects on nearby surface and underground structures is presented in this paper. In contrast to other existing approaches, effects on a particular structure and the influence of non-uniform soil conditions along the track can be evaluated. Numerical results are obtained for different situations and some of them are compared with existing experimental records. The experimental values are to a large extent reproduced by the present numerical approach

High-speed train-induced ground motion and interaction with structures

A general numerical model for the analysis of soil motion due to high-speed train passage and effects on nearby surface and underground structures is presented in this paper. Soil, ballast and structures are represented using a three-dimensional time domain boundary element approach. Material damping has been included in the time domain formulation. Equilibrium and compatibility between soil and underground or surface structures is established in a rigorous manner in order to take into account soil–structure interaction. In contrast to other existing approaches, effects on a particular structure and the influence of non-uniform soil conditions along the track can be evaluated. Numerical results are obtained for different situations and some of them are compared with existing experimental records. The experimental values are to a large extent reproduced by the present numerical approach. Ballast influence and effects of high-speed train passage on a concrete underpass structure are analysedMinisterio de Educación y Ciencia BIA2004-03955-C02-01Ministerio de Fomento Proyecto ‘‘Evaluación de efectos dinámicos del ferrocarril’

Dynamic analysis of a cable-stayed deck steel arch bridge

A theoretical and experimental research work in relation to Barqueta cable-stayed bridge is described in this paper. Barqueta Bridge, across Guadalquivir river, links the city of Seville with the Scientific Park Cartuja 93. At jam hours cars may cover one half of the bridge lanes for more than one hour. Full-scale tests were carried out to measure the bridge dynamic response. The experimental program included the dynamic study for two different live load conditions: the bridge with one half of it lanes full of cars, and the bridge empty of cars. Modal parameters estimations were made based on the acquired data. Ten vibration modes were identified in the fre-quency range of 0-6 Hz by different techniques, being two of these modes very close to each other. The traffic-structure interaction is also studied. Experimental results were compared with those obtained from a three-dimensional finite element model developed in this work. Both sets of results show very good agreement. Finally, a damage identification technique has been applied to determine the integrity of the structure. Results obtained from a test developed in July 2005 have been correlated to experimental results obtained in October 2006 using the damage index methodMinisterio de Educación y Ciencia BIA2004-03955-C02-01Ministerio de Foment

Dynamic study of the Barqueta cable-stayed Bridge

Proceedings of a meeting held 30 January - 2 February 2006, St Louis, Missouri, USA. http://toc.proceedings.com/00102webtoc.pdf Vol. 1A theoretical and experimental research work of the Barqueta cable-stayed bridge is described in this paper. The Barqueta Bridge, across Guadalquivir river, links the city of Seville with the Scientific Park Cartuja 93. At jam hours cars may cover one half of the bridge lanes for more than one hour. Full-scale tests were carried out to measure the bridge dynamic response. The experimental program includes the dynamic study for both cases: the bridge with one half of it lanes full of cars, and empty. Modal parameters estimations were made based on the acquired data. Ten vibration modes have been identified in the frequency range of 0-6 Hz by different techniques, being two of these modes very close to each other. The traffic-structure interaction is also studied. The experimental results were compared with those obtained from a three-dimensional finite element model developed in this work. Both sets of results show very good agreement. Finally, a damage identification technique has been applied to determine the integrity of the structureMinisterio de Educación y Ciencia BIA2004-03955-C02-0

Identificación Dinámica de una Pasarela a partir de la Respuesta originada por Cargas de Servicio

XVI Congreso Nacional de Ingeniería Mecánica, celebrado en León en 2004Los parámetros modales caracterizan dinámicamente a un sistema mecánico. El análisis modal es el método clásico con el que se obtienen dichos parámetros, el cual requiere el conocimiento de tanto la respuesta de la estructura como de la excitación que la origina. Normalmente, las excitaciones a las que están sometidas las estructuras (puentes, altos edificios, etc.) no pueden ser medidas con exactitud. Sin embargo, buenas estimaciones de los parámetros modales pueden ser obtenidas a partir de la respuesta de la estructura a sus cargas de servicio (viento, tráfico, etc.) empleando análisis modal operacional (OMA). En este trabajo se describen los ensayos dinámicos realizados en una pasarela curva, de donde se obtienen los parámetros modales de la estructura. Se han identificado 9 modos de vibración en un rango de frecuencias de 0-30 Hz, y se han comparado los resultados experimentales con un modelo riguroso de elementos finitos.The modal parameters describe the dynamic properties of a mechanical system. The classical modal analysis requires measurements of both the input force and the response. Normally, it is very difficult to measure the excitation on large structures (bridges, tall buildings, etc.). However, reasonable estimates of the modal parameters can be extracted from ambient vibration or output-only response (wind, traffic, humans, etc.). The dynamic behaviour of a curved pedestrian bridge has been investigated by full-scale testing and theoretical models. Nine vibration modes have been identified in the frequency range of 0-30 Hz, by the following algorithms: Enhanced Frequency Domain Decomposition (EFOD) and Stochastic Subspace ldentification (SSI). Ambient modal parameters estimation have been compared with a rigorous threedimensional finite element model, showed very good agreement

Modal identification of a pedestrian bridge by output-only analysis

The modal parameters (natural frequencies, mode shapes and damping ratios) describe the dynamic properties of a mechanical system. The classical modal analysis, based on Frequency Response Function, require measurements of both the input force and the response. Normally, it is very difficult to measure the excitation on large structures (bridges, tall buildings, offshore platforms, etc.). However, reasonable estimates of the modal parameters can be extracted from ambient vibration or output-only response (wind, traffic, humans, etc.). The dynamic behaviour of a curved pedestrian bridge in the University of Seville (Spain) has been investigated by full-scale testing and theoretical models. Nine vibration modes have been identified in the frequency range of 0-20 Hz, by the following algorithms: Enhanced Frequency Domain Decomposition (EFDD) and Stochastic Subspace Identification (SSI). Ambient modal parameters estimation have been compared with a rigorous three-dimensional finite element model, showed very good agreement.Ministerio de Educación y Ciencia DPI2001-2377-C02-01 BIA2004- 03955-C02-0