An experimental investigation was conducted to study the stiffness of wood diaphragms. Currently there is no method to calculate wood diaphragm stiffness that can reliably account for all of the various framing configurations. Diaphragm stiffness is important in the design of wood framed structures to calculate the predicted deflection and thereby determine if a diaphragm may be classified as rigid or flexible. This classification controls the method by which load is transferred from the diaphragm to the supporting structure below. Multiple nondestructive experimental tests were performed on six full-scale wood diaphragms of varying sizes, aspect ratios, and load-orientations. Each test of each specimen involved a different combination of construction parameters. The construction parameters investigated were blocking, foam adhesive, presence of designated chord members, corner and center sheathing openings, and presence of walls on top of the diaphragm. The experimental results are analyzed and compared in terms of equivalent viscous damping, global stiffness, shear stiffness, and flexural stiffness in order to evaluate the characteristics of each construction parameter and combinations thereof. Recommendations are presented at the end of this study as to the next steps toward development of an empirical method for calculating wood diaphragm stiffness. / Master of Science

Accurate camber prediction in prestressed concrete bridge beams is important to all parties involved in bridge design and construction. Many current prestress loss prediction methods, necessary for proper camber calculation, were developed many years ago and are predicated on assumptions that may no longer be valid as higher strength concrete, wider beam spacing, and longer span lengths become more commonplace. This throws into question which models are appropriate for use in camber calculation by the bridge engineers and contractors of today. Twenty-seven high-strength concrete modified 79 in. Bulb Tee beams with a design compressive strength of 9,000 psi were periodically measured to determine camber growth. Most available models for concrete creep and shrinkage were used to calculate creep and shrinkage strain. The modulus of elasticity equation of each model was used to predict modulus of elasticity of the studied mix. The Shams and Kahn compressive strength and modulus of elasticity equations were modified in order to approximate measured modulus of elasticity. The creep, shrinkage, and modulus of elasticity equations were used as inputs to an incremental time step method. The time-dependent change in beam curvature calculated by the time step method was used to calculate theoretical camber using the Moment-Area method. Predicted camber, using inputs from each considered model, was then compared with measured camber to determine the most accurate camber prediction models. Season of casting was also examined to determine what, if any, affect ambient temperature has on camber growth. For the studied beams, the Shams and Kahn Model for creep, shrinkage, and modulus of elasticity, used as inputs for an incremental time step analysis, were found to most accurately predict camber values. Lower concrete compressive strength was observed for test cylinders from beams cast in summer versus beams cast in winter. Differences in beam deflection based on season of casting showed mixed results. / Master of Science

A series of wind tunnel tests were conducted to determine the aerodynamic forces and moments produced by several clamped oblique wings. The wing sweep and aileron deflection angles were varied throughout a wide range of dynamic pressures. The wing structure was also stiffened. Strains were measured in the swept forward wing panels. Results from these tests showed that increasing the wing structural stiffness or applying aileron deflection would increase the wing divergence speed. The divergence speed decreased as the sweep angle increased. Further tests were conducted with the wing unconstrained in roll. Results showed that an oblique wing will attempt to unload its sweptforward panel by assuming a banked position. The wings were found to flutter before unclamped divergence occurred. Finally, it was found that the wing loading of an oblique wing can remain constant for a given aileron deflection throughout a wide range of velocities including velocities above the clamped divergence speed. / Master of Science

In recent years, leaning arches have been used in frameworks for some tent structures. Various people have studied the behavior of a single vertical arch; however, only a few researchers have considered the three-dimensional behavior of arches and leaning arches. The objective of this thesis is to analyze the three-dimensional nonlinear behavior of leaning arches, particularly the load-deflection and load-frequency relationships, and to provide a basis for future design guidelines. In this study, vertical arches of different shapes and load combinations are analyzed in order to compare with previous results given by other researchers. Then, the behavior of single tilted arches with different tilt angles is considered. Finally, a leaning arch structure, with two arches inclined to each other and joined at the top, is considered. The load displacement and load-frequency relationships, as well as some buckling modes, are discussed and presented in both tabular and graphical formats. / Master of Science

Presented in this work are the results of twelve flexural tests conducted on small-scale coupons to establish the load-deflection behavior of UNS S32003 (ATI 2003®) hot-rolled duplex stainless steel flat plates. All specimens were tested as simply supported beams loaded at the midspan. Test specimens had nominal width and thickness of 1 in. and 0.25 in., respectively. Four different span lengths of 4 in., 6 in., 9 in., and 12 in. were investigated. Analysis of the results showed that the non-linear deflection behavior can be estimated reasonably well by adopting the conventional deflection equation pertaining to an assumed linear elastic material, but after replacing the modulus of elasticity with a secant modulus corresponding to the maximum tension strain resulting from the applied load.

Há algumas décadas a viga de Benkelman vem sendo utilizada como um meio de controlar a qualidade das camadas de pavimento recém executadas, ao aferir as deflexões máximas na superfície dos materiais. Apesar disto, não existe qualquer referência que auxilie na determinação das deflexões admissíveis, uma vez que nenhuma norma técnica trata sobre os valores aceitáveis para a liberação das camadas. Neste contexto, as responsáveis pela definição dos parâmetros de controle passam a ser as projetistas, que muitas vezes não possuem conhecimento suficiente sobre os materiais de pavimentação para cumprir esta tarefa. O resultado disto são valores de controle sem fundamentos e inconsistentes, que são incapazes de representar de forma fidedigna as condições de campo, gerando uma série de dificuldades em obra. Sendo assim, este trabalho tem por objetivo fazer uma reflexão crítica sobre o modo como as deflexões de controle são definidas pelas projetistas, analisando as considerações de projeto que podem levar a resultados incoerentes em campo e propondo diretrizes para o aperfeiçoamento desta prática. Para isto, foi feita uma revisão bibliográfica sobre os principais fatores que podem afetar os valores de módulos de resiliência dos materiais e, consequentemente, as medidas de deflexões. Complementarmente, foram revisados valores de módulos de resiliências obtidos em laboratório e retroanalisados em pista. Em seguida, foi estudado o caso da obra de ampliação do Aeroporto Internacional Tom Jobim no Rio de Janeiro, em que resultados insatisfatórios de deflexões obtidas em campo levaram a uma revisão dos parâmetros de controle, revelando os principais equívocos cometidos pela projetista e os pontos críticos do processo de determinação dos valores de controle. Com base nisto, foi feita uma análise crítica das deflexões revisadas, mostrando como a variação de alguns critérios e parâmetros pode afetar os resultados e o que isto representa em termos práticos para o controle deflectométrico. Por fim, foi realizado um refinamento dos valores de deflexões de controle definidos pela projetista. / For decades, the Benkelman beam has been used to assure the quality of pavement construction by measuring the maximum deflections on top of the materials. Nevertheless, there are neither technical standards nor any references that determine a range of acceptable values for deflection. In this context, the definition of these parameters of control is the responsibility of the designers, who mostly do not have the expertise to complete the task. Consequently, the control values tend to be inconsistent and unable to represent in a reliable way the site conditions, creating a number of constraints/shortcomings. Hence, the objective of this dissertation is to undertake a critical analysis on the way the acceptable deflections are determined by the designers, evaluating the project assumptions that can lead to incoherent results on site and proposing guidelines for the improvement of this practice. For this, the main factors that can affect the elasticity of the materials and its deflections were reviewed, in addition to typical values of resilient modulus obtained in laboratory and from backanalysis. Next, the case of the Rio de Janeiro International Airport expansion project was studied. On that occasion, the deflections measured on site during the construction of the pavements were constantly greater than the control values indicated in the project. A revision of the parameters was undertaken by the designer to identify the reasons for the discrepancies and thus, unveiling the critical points of the process. Based on that, a critical analysis on the revised deflections was carried out, showing how the variation of some criteria and parameters can affect the results and what this represents in practical terms for the deflectometric control. Finally, a refinement of the acceptable deflections defined by the designer was proposed.

Há algumas décadas a viga de Benkelman vem sendo utilizada como um meio de controlar a qualidade das camadas de pavimento recém executadas, ao aferir as deflexões máximas na superfície dos materiais. Apesar disto, não existe qualquer referência que auxilie na determinação das deflexões admissíveis, uma vez que nenhuma norma técnica trata sobre os valores aceitáveis para a liberação das camadas. Neste contexto, as responsáveis pela definição dos parâmetros de controle passam a ser as projetistas, que muitas vezes não possuem conhecimento suficiente sobre os materiais de pavimentação para cumprir esta tarefa. O resultado disto são valores de controle sem fundamentos e inconsistentes, que são incapazes de representar de forma fidedigna as condições de campo, gerando uma série de dificuldades em obra. Sendo assim, este trabalho tem por objetivo fazer uma reflexão crítica sobre o modo como as deflexões de controle são definidas pelas projetistas, analisando as considerações de projeto que podem levar a resultados incoerentes em campo e propondo diretrizes para o aperfeiçoamento desta prática. Para isto, foi feita uma revisão bibliográfica sobre os principais fatores que podem afetar os valores de módulos de resiliência dos materiais e, consequentemente, as medidas de deflexões. Complementarmente, foram revisados valores de módulos de resiliências obtidos em laboratório e retroanalisados em pista. Em seguida, foi estudado o caso da obra de ampliação do Aeroporto Internacional Tom Jobim no Rio de Janeiro, em que resultados insatisfatórios de deflexões obtidas em campo levaram a uma revisão dos parâmetros de controle, revelando os principais equívocos cometidos pela projetista e os pontos críticos do processo de determinação dos valores de controle. Com base nisto, foi feita uma análise crítica das deflexões revisadas, mostrando como a variação de alguns critérios e parâmetros pode afetar os resultados e o que isto representa em termos práticos para o controle deflectométrico. Por fim, foi realizado um refinamento dos valores de deflexões de controle definidos pela projetista. / For decades, the Benkelman beam has been used to assure the quality of pavement construction by measuring the maximum deflections on top of the materials. Nevertheless, there are neither technical standards nor any references that determine a range of acceptable values for deflection. In this context, the definition of these parameters of control is the responsibility of the designers, who mostly do not have the expertise to complete the task. Consequently, the control values tend to be inconsistent and unable to represent in a reliable way the site conditions, creating a number of constraints/shortcomings. Hence, the objective of this dissertation is to undertake a critical analysis on the way the acceptable deflections are determined by the designers, evaluating the project assumptions that can lead to incoherent results on site and proposing guidelines for the improvement of this practice. For this, the main factors that can affect the elasticity of the materials and its deflections were reviewed, in addition to typical values of resilient modulus obtained in laboratory and from backanalysis. Next, the case of the Rio de Janeiro International Airport expansion project was studied. On that occasion, the deflections measured on site during the construction of the pavements were constantly greater than the control values indicated in the project. A revision of the parameters was undertaken by the designer to identify the reasons for the discrepancies and thus, unveiling the critical points of the process. Based on that, a critical analysis on the revised deflections was carried out, showing how the variation of some criteria and parameters can affect the results and what this represents in practical terms for the deflectometric control. Finally, a refinement of the acceptable deflections defined by the designer was proposed.

This thesis presents the results of a research project to investigate the behaviour of the two components of a reverse channel connection to concrete filled tubular sections: the reverse channel and the steel tubular section, at both ambient and elevated temperatures. This research forms part of a European Union funded project on the robustness of joints to composite columns under fire conditions. The specific objectives of this research are to develop methods of quantifying the load-deformation behaviour at various temperatures of the two components. This research has been carried out through a combination of experiments, numerical simulations and analytical developments. Two series of tests have been carried out at different elevated temperatures, one for the reverse channels with lateral loads to the web applied as tensile loads through bolts and one for the concrete filled tubular sections under lateral loads applied through two steel plates (simulating the legs of a reverse channel) in the longitudinal direction of the section. These tests have been used to provide data for the validation of the numerical models based on using the general finite element package ABAQUS. The validated numerical models have been used to conduct a number of parametric studies to provide extensive data for the development of analytical methods to determine the load-deflection characteristics of the two components. For the reverse channel web, the load-deflection relationship consists of two parts and this research has developed analytical equations to predict initial stiffness, yield and ultimate resistance. The initial stiffness is based on extending and simplifying the Timoshenko solution for a plate under a block of lateral loads. The yield resistance is based on the yield line solution that the failure patterns were chosen based on the results attained from test and simulations. The ultimate resistance was calculated based on virtual work principle for the patterns considered in the yield resistance part. For the rectangular concrete filled tubular sections under lateral pulling forces applied through two plates, the load-deflection curve consists of two parts, depicting a linear phase followed by a nonlinear part. This research has developed expressions to calculate initial stiffness, yield resistance, and ultimate resistance. The initial stiffness is formulated according to the Timoshenko solution for a partially loaded plate. The yield resistance is determined by employing yield line solution for the yield patterns obtained from both the test and FE modelling. The ultimate resistance is evaluated by implementing the virtual work principle to the patterns considered in former part. The analytical load-deflection solutions have been compared with the numerical simulation and the experimental results and the agreement is generally satisfactory.

A novel optical diffraction based technique is proposed and demonstrated to measure deflections of the order of ~1nm in microcantilevers (MC) designed for sensing ultra-small forces of stress. The proposed method employs a double MC structure where one of the cantilevers acts as the active sensor beam, while the other as a reference. The active beam can respond to any minute change of stress, for example, molecular recognition induced surface stress, through bending (~1nm) relative to the other fixed beam. Optical diffraction patterns obtained from this double slit aperture mask with varying slit width, which is for the bending of MC due to loading, carries the deflection profile of the active beam. A significant part of the present work explores the possibility of connecting diffraction minima (or maxima) to the bending profile of the MC structure and thus the possibility to measure induced surface stress. To start with, it is also the aim to develop double MC sensors using PHDDA (Poly – Hexane diol diacrylate) because this material has the potential to achieve high mechanical deformation sensitivity in even moderately scaled down structures by virtue of its very low Young’s modulus. Moreover, the high thermal stability of PHDDA also ensures low thermally induced noise floors in microcantilever sensors. To demonstrate the proposed optical diffraction-based profiling technique, a bent microcantilever structure is designed and fabricated by an in-house developed Microstereolithography (MSL) system where, essentially one of the microcantilevers is fabricated with a bent profile by varying the gap between the two structures at each cured 2D patterned layer. The diffraction pattern obtained on transilluminating the fabricated structure by a spherical wavefront is analyzed and the possibility of obtaining the deflections at each cross section is ascertained. Since the proposed profiling technique relies on the accurate detection and measurement of shifts of intensity minima on the image plane, analysis of the minimum detectable shift in intensity minima for the employed optical interrogation setup with respect to the minimum detectable contrast and SNR of the optical measurement system is carried out, in order to justify the applicability of the proposed minima intensity shift measurement technique. The proposed novel diffraction based profiling technique can provide vital clue on the origins of surface stress at the atomic and molecular level by virtue of the entire bent profile due to adsorption induced bending thereby establishing microcantilever sensor technology as a more reliable and competitive approach for sensing ultra-low concentrations of biological and chemical agents.

L’évaluation des caractéristiques structurelles des chaussées permet l’optimisation de leur maintenance. La mesure de déflexion est une mesure de base de cette évaluation. Aujourd’hui,seuls la déflexion maximale et le rayon de courbures ont analysés. Pourtant, le curviamètre et le déflectographe relèvent le bassin de déflexion complet dont l’analyse permettrait d’extraire des paramètres plus sensibles à l’endommagement des chaussées. Actuellement, l’interprétation des mesures est seulement qualitative et aucun calcul inverse de l’état de dommage de la structure n’est réalisé. La thèse vise à améliorer l’interprétation des mesures de déflexion. Le fonctionnement des appareils a montré que leurs hypothèses de mesure conduisent à des biais de mesure. Pour pallier ce problème, une procédure de correction des mesures a été mise en place. La comparaison avec des bassins théoriques a montré que la méthode de correction était satisfaisante. Ensuite, une étude numérique visant à déterminer la sensibilité du bassin de déflexion à la présence de différents défauts a été conduite. Celle ci a montré que les indicateurs classiques de la mesure de déflexion étaient peu sensibles à un endommagement dans la chaussée. Une méthodologie a donc été développée pour la création d’indicateurs optimisés à un type de défauts spécifiques. L’étude sur cas théoriques a conduit à l’obtention de résultats concluants. L’ensemble de ces travaux a ensuite été validé sur sites expérimentaux pour des mesures de répétabilité, mais également sur site avec la présence avérée de défauts. Finalement, la thèse a envisagé l’utilisation des travaux précédents sur des mesures réelles recueillies sur itinéraire. / The evaluation of the structural characteristics of pavements is involved in their maintenance. The measurement of deflection is a key indicator of this evaluation. Currently, only the maximum deflection and the radius of curvature are analyzed. However, the curviameter and the deflectograph are able to record the whole deflection bowl and the parameters deduced from thismeasurement could help to better characterized damages on pavements. The interpretation of the measurements is only qualitative and back calculation of pavement layer moduli gives unsatisfactory results. The thesis aims to improve the interpretation of deflection measurements. The working principle of these apparatus and the measurement assumptions introduce several measurement biases.To overcome these issues, a correction process has been developed. The comparison with theoretical basins has given satisfactory results on bituminous or flexible pavements. Then, a numerical study has been conducted to determine the influence of pavements damages on the deflection measurement. By this study, it has been showed that the usual indicators of the deflection measurement are notable to detect all damages. So, a methodology hasbeen developed in order to create an optimized indicator specified to a special defect. A study on numerical results has been conducted to validate the implementation of these indicators. Then, the correction method and these new indicators have been tested on experimental sites with and without damages. At last, the research works have been studied at network level.