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Publications (49)
A comparison among two blood pressure pulse propagation models has made in this work. One of them is a traditional model based upon the Navier Stockes equations in one spatial dimension, the one along the direction of the arteries (from here NS1D), the other is based the concept of soliton propagation using the Korteweg De Vries equation (named KdV...
Introduction:
A comparison among two blood pressure pulse propagation models has made in this work. One of them is a traditional model based upon the Navier Stockes equations in one spatial dimension, the one along the direction of the arteries (from here NS1D), the other is based the concept of soliton propagation using the Korteweg De Vries equa...
Introduction:
The level of smooth muscle activation or `tone' (VSMT) can be defined as an intrinsic spontaneous level of vasoconstriction that may change in response to biomechanical stimuli such as flow, pressure, hormonal stimuli, neural stimuli, and drugs. Arteries can actively modify arterial pressure pulse wave velocity (PWV) by changing smoo...
A computational procedure is developed in the present paper, allowing the prediction of the ballasted track profile degradation under railway traffic loading. In this procedure, an integration of the short-term and long-term mechanical processes of track deterioration is taken into account, using a track degradation model. This degradation model is...
Many factors have been held responsible for the elevated failure rates of vascular substitutes. Several studies have shown that the lower the mismatches regarding mechanical or functional properties between the native vessel and its vascular substitute, the lower the hemodynamic alterations. From a theoretical point of view, the best substitutes ha...
Introduction:
The interest on computational simulations of biomedical models has increased in the last years. Nevertheless, the viscous properties of vessel all are usually neglected.
Materials and methods:
A 1D model of blood flow and its interaction with the arterial wall was implemented. Non-viscous modeling and the addition of a wall-viscosi...
Application of 1D modelling to arterial networks description provides a computational low cost alternative, compared to 2D/3D simulations. However, wall viscosity is usually neglected in numerical solutions. A simplified 1D tapered model was implemented, considering the vascular path between central (aortic, cBP) and peripheral (radial, rBP) arteri...
This paper presents an investigation, using a numerical approach, of the dynamic response of the vehicle–track system as a function of the mechanical properties of high-speed rail track components. In particular, in this study the stiffness of the rail pad, ballast and sub-grade layer were considered as variable parameters. In order to assess their...
This paper presents an investigation, using a numerical approach, of the dynamic response of the vehicle-track system as a function of the mechanical properties of high-speed rail track components. In particular, in this study the stiffness of the rail pad, ballast and sub-grade layer were considered as variable parameters. In order to assess their...
In pre-surgery decisions in hospital emergency cases, fast and reliable results of the solid and fluid mechanics problems are of great interest to clinicians. In the current investigation, an iterative process based on a pressure-type boundary condition is proposed in order to reduce the computational costs of blood flow simulations in arteries, wi...
Analysis for severe accidents has recently been added to the long list of requisites imposed on nuclear power plants. In this work we study the rationale and justiflcation for this type of analysis. Calculations for the structural response of the containment buildings can be performed on the computer using advanced nonlinear Finite Element codes. A...
The vertical dynamic actions transmitted by railway vehicles to the ballasted track infrastructure are evaluated taking into account models with different degrees of detail. In particular, this matter has been studied from a two-dimensional finite-element model to a fully coupled three-dimensional multibody finite-element model. The vehicle and tra...
In this chapter, a critical review of methods for evaluating dynamic effects on high-speed railway bridges is performed, discussing the relevant features and practical design issues. Closed form solutions for the moving load problem are first discussed and compared to envelopes of impact factors in engineering codes. Moving load models provide the...
The threat of impact or explosive loads is regrettably a scenario to be taken into account in the design of lifeline or critical civilian buildings. These are often made of con-crete and not specifically designed for military threats. Numerical simulation of such cases may be undertaken with the aid of state of the art explicit dynamic codes, howev...
Palabras clave: Explosión, hormigón armado, losa reticulada, colapso progresivo Resumen. Los fenómenos de impacto y explosión sobre estructuras de hormigón tienen efectos en muchos casos catastróficos a pesar de su reducida probabilidad. Las estructuras de hormi-gón no suelen estar diseñadas para resistir este tipo de solicitaciones dinámicas. El a...
The objective of this work is to develop adequate and efficient models for calculation of vertical dynamic traffic load effects on railway track infrastructures, and applications for evaluating the comparative performance of ballast and slab track designs. The calculations are based on dynamic finite element models with direct time integration and...
El tráfico ferroviario genera cargas sobre los elementos de las estructuras de vía cuyo reparto depende de los parámetros de rigidez y masa de la vía y del vehículo. El estudio de dichas cargas es de capital importancia en las nuevas infraestructuras ferro-viarias de alta velocidad. En particular, resultan de especial interés los efectos dinámicos...
Neste artigo, analisa-se numericamente o comportamento dinâmico de um sistema de via ferroviária em laje para tráfego de comboios de alta velocidade. De entre os vários tipos de via existentes seleccionou-se o sistema Rheda 2000, que consiste na última versão de via da família Rheda, tendo sido já aplicado em várias linhas europeias, tais como a HS...
The construction of new high speed railway infrastructure in many European countries is actually a great civil engineering effort. One of the main design issues is related to the fact that trains at speeds above 220 km/h may induce resonance effects in structures as bridges, subway frames, etc. In consequence, the design of such structures requires...
Bridges and viaducts for high speed trains are subject to demanding dynamic loads. In addition to the classical effect of the moving (single) load, much larger and potentially dangerous effects arise from dynamic resonance, for speeds above 220 km/h. The classical methods for evaluation of dynamic impact factors, reflected in the codes of practise...
High-speed railway lines are an important factor for modernisation of transport in Europe, specially in countries such as Spain with a historic deficit in infrastructure. This work will also discuss some issues related to dynamic effects in railway bridges. Firstly we review and comment analysis methods from a practical point of view. Following, is...
A relevant aspect in the design of structures under high speed train loads is the dynamical effects associated to the moving loads of the train. In this paper some calculation methods that are usual in the design of high speed train structures are considered. These methods are based on the integration of the motion equations, with or without consid...
The study of the lateral behaviour of railway bridges and vehicles is an important issue on bridges with low lateral stiffness, which has been defined by ERRI (1996) as those with lateral natural frequencies below 1.2 Hz. This limit applies to the deformation of the deck in one span, and was demonstrated to be a real issue on measurements and model...
A relevant aspect in the design of structures under high speed train loads is the dynamical effects associated to the moving loads of the train. In this paper some calculation methods that are usual in the design of high speed train structures are considered. These methods are based on the integration of the motion equations, with or without consid...
High-speed railway lines are an important factor for modernisation of transport in Europe, specially in countries such as Spain with a historic deficit in infrastructure. This work will also discuss some issues related to dynamic effects in railway bridges. Firstly we review and comment analysis methods from a practical point of view. Following, is...
The dynamic behaviour of bridges strongly affects the infrastructure system of high-speed railways, and is a crucial factor in safety issues and passenger comfort. Dynamics of High-Speed Railway Bridges covers the latest research in this field, including: – Recently developed dynamic analysis techniques; – Train excitations; – Design issues for hig...
We discuss here recent results from several research programmes related to dynamic aspects and vibrations induced by high speed railway traffic, developed at the computational mechanics group, within the “Escuela de Ingenieros de Caminos” of the Technical University of Madrid. The first part of this work concerns the dynamic response of railway bri...
Stress and deformation in arterial wall tissue are factors which may influence significantly its response and evolution. In this work we develop models based on nonlinear elasticity and finite element numerical solutions for the mechanical behaviour and the remodelling of the soft tissue of arteries, including anisotropy induced by the presence of...
In this work the finite element simulation of the simple tension test in metals is discussed. Results from Bridgman as well as experimental measurements obtained with aluminium specimens are compared with numerical simulations. The computational analyses carried out consider several finite element technologies as the Q1/P0 mixed formulation, and va...
Bridges and viaducts for high speed railways are subject to significant dynamic actions. To the classical effect of a (single) moving load one has to add the resonant behaviour which occurs for train speeds above 220 km/h. The provisions for dynamic effects foreseen in existing classical design codes do not cover this possibility of resonance. The...
Mechanical simulation of tissue in the walls of coronary arteries may provide valuable quantitative information for medical
practice, such as understanding the evolution of stenosis, angioplasty processes, and placement of stents and possible restenosis.
The material constitutive models which represent the mechanical response to strain are highly n...
In this work we analyse the use of enhanced strain fields for the purpose of error estimation in finite element solid mechanics applications. The proposed approach evaluates the quality of the solution for standard Galerkin displacement elements, taking into account the enrichment of the solution with enhanced assumed strain mixed elements. The con...
Palabras clave: Cálculo dinámico de estructuras, ferrocarril de alta velocidad. Resumen. Los puentes y viaductos para ferrocarril de alta velocidad están sometidos a accio-nes dinámicas elevadas, ya que al efecto clásico de la carga (aislada) móvil se viene a sumar la resonancia que se manifiesta para velocidades por encima de 220 km/h. Los métodos...
El trabajo desarrollado en esta tesis se encuentra en el contexto de los elementos mixtos con deformaciones supuestas en plasticidad. Empleando las formulaciones para deformaciones infinitesimales y para deformaciones finitas, que se analizan de manera crítica y detallada al principio de este trabajo se investigan diversos aspectos de su comportami...
Se presenta en este trabajo una metodología adecuada para la resolución de algunos problemas de conformado de metales.
Resumen. La infraestructura para alta velocidad ferroviaria es uno de los focos de mayor interés ac-tual en la ingeniería civil en España y Portugal. Son bien conocidos los aspectos dinámicos de la respuesta de los puentes frente a cargas móviles de tráfico. Sin embargo, la alta velocidad ferroviaria ocasiona problemas nuevos debidos a la resonanci...
Bridges and viaducts for high speed trains are subject to demanding dynamic loads, as to the classical effect of the moving (single) load the dynamic resonance appears for speeds above 220 km/h. The classical methods for evaluation of dynamic impact factors available in engineering, reflected in the codes of practise existing until recently, do not...
Palabras clave: Cálculo dinámico de estructuras, ferrocarril de alta velocidad. Resumen. Los puentes y viaductos para ferrocarril de alta velocidad están sometidos a accio-nes dinámicas elevadas, ya que al efecto clásico de la carga (aislada) móvil se viene a sumar la resonancia que se manifiesta para velocidades por encima de 220 km/h. luces corta...
Trains at speeds above 200 km/h may induce resonance in bridges or viaducts. This fact implies the necessity of sufficiently detailed dynamic calculations, which has been included in the latest engineering codes of practise (FS 1997; prEN 1991-2 2002; IAPF 2001). Various mathematical models are available for dynamic analysis of trains of moving loa...
En este artículo se describe una metodología para la estimación de error mediante elementos con formulación de deformaciones mejoradas supuestas y su aplicación a problemas de elasticidad lineal, de elasticidad no lineal con deformaciones finitas y de plasticidad infinitesimal. La relación entre los modos mejorados de deformación y la calidad de la...