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Water-assisted crack growth at an epoxy/glass interface was measured as a function of applied strain energy release rate, G, and temperature using a wedge test geometry. The specimens consist of two glass plates bonded with a thin layer of proprietary epoxy adhesive. The crack fronts along the epoxy/glass interfaces were measured using an optical stereomicroscope. The relationship between G and the debonding rate, v, can be measured using this method, and the threshold value of strain energy release rate, Gth, can be determined from the measured data. Two types of testing procedures were conducted in this study: ex situ, i.e., pre-conditioned wedge tests and in situ ones, in which wedges were applied before the specimens were submerged into water. A preliminary model was developed based on the thermal activation barrier concept, and allows the prediction of Gth for the temperatures beyond the testing region. Changes in interfacial strain energy release rate caused by thermal residual stresses in a triple-layered specimen were analyzed in Chapter Three. The method is based on linear elastic fracture mechanics and simple beam theory. The curvature of a bimaterial strip was chosen to characterize the residual stress in the specimen, and the strain energy release rate, caused by both tensile and compressive residual stresses in the adhesive, was derived for an asymmetric double cantilever beam (ADCB) geometry. The contribution of the thermal residual and mechanical stress to the global energy release rate was analyzed. The thermally induced energy release rate, GT, is found to be independent of crack length, but is a function of residual stress level and geometric and material parameters of the specimen. The adhesion of films and coatings to rigid substrates is often measured using blister geometries, which are loaded either by an applied pressure or a central shaft. The measurement will be affected if there are residual stresses that make a contribution to the energy release rate. This effect is investigated using analytical solutions based on the principle of virtual displacements. A geometrically nonlinear finite element analysis is conducted for comparison. Furthermore, the relationships among strain energy release rate, load, deflection, and fracture radius are discussed in detail in Chapter Four. Both analytical solutions and numerical results reveal that uniform tensile residual stresses reduce a specimen's deflection if it experiences plate behavior under small loads. However, this effect diminishes when membrane behavior is dominant. The mechanics of a single-lap joint with different boundary conditions subjected to tensile loading are investigated. Closed-form solutions are obtained for a specimen configuration considering different clamping methods. Based on the approach pioneered by Goland and Reissner, the solutions reported in this paper provide a simple but useful way to understand the effects of boundary conditions on this test geometry. The solutions in this study suggest that different grip configurations mainly affect the response of the specimens if the grip position is close to the joint edge or the loads are small. Generally, the influence caused by different gripping methods is only limited to the boundary region, and the behavior of the joint part subjected to tensile loading is almost the same as that for a simply-supported case. / Ph. D.

[ES] El objetivo de la tesis es proponer una metodología que permita la definición de pasarelas de un único vano a partir de unas condiciones de contorno determinadas, utilizando unos diseños estéticamente atractivos. Se desarrolla el diseño y la formulación geométrica de tres pasarelas paramétricas, denominadas Von Mises, Monocontentio y Bicontentio, cuyo diseño se basa en cinco fundamentos básicos: integración en la geometría del terreno, búsqueda continua de la sencillez, siluetas que emanan del comportamiento estructural, formas unitarias y detalles perdurables. La silueta de la pasarela Von Mises se basa en la gráfica del criterio de comparación de Von Mises de una viga biapoyada, la del prototipo Monocontentio en la ley de momentos de una viga empotrada-apoyada y la de la pasarela Bicontentio en la gráfica de flectores de una viga biempotrada. El trabajo incluye una metodología de formulación, que permite obtener las expresiones matemáticas que gobiernan las principales dimensiones y espesores de las pasarelas, en función de su anchura y su luz. Un análisis comparativo de diferentes tipologías de pasarelas viga permite constatar la eficiencia de los prototipos Von Mises, Monocontentio y Bicontentio. Esta se debe a su canto variable adaptado a los esfuerzos de solicitación y al empotramiento en estribos. Asimismo, se realiza un análisis que liga el enfoque de diseño y el pensamiento ingenieril con la expresión estética de los puentes. La tesis supone la puesta en orden de una particular filosofía de diseño utilizada por el autor en una treintena de puentes proyectados durante los últimos 25 años, para poder ser aplicada de manera sistemática por otros profesionales. / [CA] L'objectiu de la tesi és proposar una metodologia que permeta la definició de passarel·les d'un únic tram a partir d'unes condicions de contorn determinades, utilitzant uns dissenys estèticament atractius. Es desenvolupa el disseny i la formulació geomètrica de tres passarel·les paramètriques, denominades Von Mises, Monocontentio i Bicontentio, el disseny de les quals es basa en cinc fonaments bàsics: integració en la geometria del terreny, cerca contínua de la senzillesa, siluetes que emanen del comportament estructural, formes unitàries i detalls perdurables. La silueta de la passarel·la Von Mises es basa en la gràfica del criteri de comparació de Von Mises d'una biga bi- recolzada, la del prototip Monocontentio en la llei de moments d'una biga encastada-recolzada i la de la passarel·la Bicontentio en la gràfica de flectors d'una biga bi-encastada. El treball inclou una metodologia de formulació, que permet obtindre les expressions matemàtiques que governen les principals dimensions i grossàries de les passarel·les, en funció de la seua amplària i la seua llum. Una anàlisi comparativa de diferents tipologies de passarel·les biga permet constatar l'eficiència dels prototips Von Mises, Monocontentio i Bicontentio. Aquesta es deu al seu cant variable adaptat als esforços de sol·licitació i a l'encast en estreps. Així mateix es realitza una anàlisi que lliga l'enfocament de disseny i el pensament de l'enginyer amb l'expressió estètica dels ponts. / [EN] The purpose of this thesis is to propose a methodology for single-span, pedestrian bridges, based on specific conditions, using an attractive design.This thesis explains the design and geometric formulation of three types of pedestrian bridges, namely Von Mises, Monocontentio and Bicontentio. Their designs are based on five basic principles: (1) integration into the geometry of the environment; (2) permanent search for simplicity; (3) design based on a geometry that emanates from structural behavior; (4) uniform shapes; and (5) enduring details. The silhouette of the Von Mises bridge is inspired by the Von Mises criterion graph, corresponding to a simply- supported beam.The Monocontentio prototype is inspired by the bending moment diagram of a beam fixed at one end and simply supported at the other end. The Bicontentio bridge is inspired by the bending moment diagram of a beam fixed at both ends. This thesis includes a formulation methodology that defines mathematical expressions that govern the main dimensions and thickness of a pedestrian bridge, depending on its respective width and span. A comparative analysis demonstrates the efficiency of these three particular prototypes, due to their variable depth, adapted to the internal forces, and due to fix the structure in abutments. Likewise, this paper analyses and links the design and engineering with the aesthetic expression of the bridges.The author has used this design philosophy in thirty bridge projects over the last 25 years, and such philosophy may be applied in a systematic way by other professionals. / Guisasola Ron, M. (2022). Desarrollo de nuevas formas parametrizadas para pasarelas eficientes y elegantes [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/180776