Abstract

Fiber-reinforced polymer pedestrian bridges are becoming a competitive alternative to conventional concrete or steel pedestrian bridges in the span range from 5 to 30 m. In order to consider it as a viable alternative, it is necessary, among other things, to be price competitive in the total cost of the bridge, including construction and full-life maintenance. One of the ways of making the cost competitive is to normalize a few cross-sections and create a catalog of standard cross-sections and shapes depending on the load conditions and ranges of spans. The objective of this work has been to create this catalog, taking into account the following items: A detailed economic analysis of the impact of every sub cost in the total construction and maintenance cost. A detailed structural analysis and optimization, by using MEF, of different cross-section and laminate solutions has been carried out, both under static and dynamic loads, in order to achieve the best possible design. The preparation of a specialized FEM analysis software that already includes in its database the chosen laminates as well as automatized geometrical construction and standarised load cases definition. With all these tools, it is possible to make highly reusable molds for the laminates and it is possible to make the final cost of the FRP pedestrian bridge more competitive.

Abstract

En esta tesis se describe el desarrollo e implementación de un sistema informático para el tratamiento de toda la información necesaria para un análisis por el Método de los Elementos Finitos o por otros métodos numéricos (diferencias finitas, volúmenes finitos, métodos de contorno, métodos de puntos, etc.).Algunas de sus partes se refieren principalmente al diseño y organización de un sistema de estas características. En otras, se describen los nuevos algoritmos que ha sido necesario desarrollar para cumplir los objetivos propuestos.Las diversas disciplinas que se describen a lo largo de la tesis se pueden diferenciar en:* Organización del sistema. Consiste en definir el tratamiento de todos los datos de un análisis genérico de manera uniforme. También se dan criterios sobre el ordenamiento interno de los datos.* Modelación geométrica. Se presenta una serie de algoritmos que se han desarrollado para tratar y modificar la geometría del modelo.* Generación de malla. Se describen diferentes técnicas y algoritmos para poder realizar la generación de la malla.* Adaptabilidad del sistema a diferentes análisis. Se describe como se ha diseñado y como se realiza la adaptación del sistema a un código de análisis cualquiera.La implementación del conjunto de criterios y algoritmos descritos a lo largo de esta tesis, ha permitido la creación de un sistema que da soporte al proceso de análisis mediante métodos numéricos de modelos, tanto a nivel académico como industrial.

Abstract

One of the major difficulties in meshing 3D complex geometries is to deal with non proper geometrical definitions coming from CAD systems. Typically, CAD systems do not take care of the proper definition of the geometries for the analysis purposes. In addition, the use of standard CAD files (IGES, VDA,...) for the transfer of geometries between different systems introduce some additional difficulties. In this work, a collection of algorithms to repair and/or to improve the geometry definitions are provided. The aim of these algorithms is to make as easy as possible the generation of a mesh over complex geometries given some minimum requirements of quality and correctness. The geometrical model will be considered as composed of a set of NURBS lines and trimmed surfaces. Some examples of application of the algorithms and of the meshes generated from the corrected geometry are also presented in this work

Abstract

This paper presents advances in recent work of the authors to derive a fractional step scheme based on the stabilized finite element method that allows overcoming the above mentioned problem, resulting in a efficient time accurate scheme. The starting point is the modified governing differential equations for the incompressible turbulent viscous flow and the free surface condition incorporating the necessary stabilization terms via a finite calculus (FIC) procedure developed by the authors .  This technique is based on writting the different balance equations over a domain of finite size and retaining higher order terms. These terms incorporate the ingredients for the necessary stabilization of any transient and steady state numerical solution already at the differential equations level. The resulting stabilized equations are integrated in space using the standard finite element method, and in time using an implicit and uncoupled second order fractional step method.

Abstract

Recent developments inmesh and point generation are reviewed. These include: minimal linput meshing, fast meshing for very large problems, volume-to-surface meshing and the generation of cluouds of arbitrary objects. Several examples are included to illustrate the effectiveness of the developed techniques