Automobile accident reconstruction has been facilitated by the development of computer based modules to allow evaluation of evidence gathered at the accident scenes. Although the computer modules are based in fundamental physical laws, an understanding of these laws by the user is required for proper application of the computer model in a given accident scenario. Vehicle collision analysis techniques generally separate the collision into three phases: pre-impact, impact, and post impact. The intent of the research is to provide a generalized model to reconstruct two dimensional impact problems in the area of accident reconstruction. There are currently two modeling techniques used to reconstruct the impact phase: the first technique relying exclusively on impulse-momentum theory coupled with friction and restitution, while the second method combines impulse momentum with a relationship between crush geometry and energy loss. Because each method requires very different inputs, the literature would have us believe that both methods are different. We will show that both methods are derived using the same fundamental physical principles and for any given accident scenario, both methods will provide identical results. Each method will be presented in the form of a MathCAD spread sheet that will allow the user to reconstruct a wide variety of accidents controlling just a few parameters (i.e. mass, rotational inertia, angle of approach, etc...). Both methods will provide step by step graphical representation to assure a solid approach to physical fundamentals. The governing equations to the generalized energy approach will be non-dimensionalized and used to define all of the changes in energy (i.e. also referred to as an impulse in power) as a function of a characteristic velocity. Finally, different methods to consistently determine the direction of the force will be presented when additional information from the accident scene is provided.

Fundações constituídas de estacas pré-moldadas cravadas têm, na questão dos controles executivos, significativas vantagens em relação às estacas moldadas in loco: desde a simplicidade executiva dos diagramas de cravação até a sofisticação teórica dos ensaios de carregamento dinâmico, há sempre a possibilidade de expeditas verificações de comportamento da cravação, de homogeneidade de estaqueamento e até estimativas da capacidade de carga. No entanto, assim como o grande número de dispositivos de controle para esse tipo de estaca representa uma vantagem, a diversidade de formas existentes de interpretá-los representa, igualmente, uma desvantagem. Em face disso, a presente pesquisa compilou 881 registros de ensaios de carregamento dinâmico (708 em estacas de concreto e 173 em estacas de aço) e os comparou com as estimativas de resistência da Equação de Energy Approach. A aplicabilidade da equação foi testada aos dois materiais de estaca, principalmente quando se estudaram variações do parâmetro Ksp em relação às diversas grandezas envolvidas na cravação, seus extremos empíricos e uma proposta de calibração à fórmula dinâmica por meio desse parâmetro chave. O estudo dos ensaios dinâmicos também levou à proposição de uma equação para se estimar a energia efetivamente transferida à estaca no golpe do martelo por meio da nega e do repique elástico. O presente estudo também dedicou uma seção à questão das tensões dinâmicas de compressão na cravação, avaliando estimativas de tensões por meio da Equação de Gambini e propondo duas versões alternativas ao método: uma primeira, simplificada e uma de cunho prático, com objetivo de possibilitar rápidas estimativas das tensões de compressão quando ainda em campo. / Driven precast piled foundations have significant advantages in respect of quality control over cast-in-place piles - from the executive simplicity of the blow count diagrams to the theoretical sophistication of dynamic load tests - there is always the possibility of fast and practical driving behavior check, homogeneity and even load capacities estimation. However, as the large number of available quality controls represents an advantage, that diversity can equally represent a disadvantage in respect to interpretation and methodology. Therefore, the present research compiled 881 records of dynamic load tests (708 on concrete piles and 173 on steel piles) and compared them with the resistance estimation with the Energy Approach Equation. The applicability of the equation was tested for both materials, especially when studying its main parameter (Ksp) variation related to several variables involved in pile driving, its empirical extremes and a calibration to the dynamic formula by means of Ksp. The study of the dynamic tests also led to the proposition of an equation to estimate the effective transferred energy to the pile in the hammer stroke by means of the blow count (set) and the elastic rebound. The study also devoted a section to the issue of dynamic compression stresses during driving, evaluating it through Gambini\'s Equation and proposing two alternative versions of that formula: a simplified one and a practical formulation in order to enable field estimations.

Laboratory characterization of subgrade soils and unbound granular materials is an essential component of the Mechanistic-Empirical Pavement Design Guide (Pavement ME). The design thickness and performance of a pavement structure are highly dependent on the deformation behaviour of subgrade and granular material. Specifications for granular materials vary among transportation agencies based on the availability of materials, climatic conditions, and function. Specifications aim to provide durable materials that meet design requirements and achieve the target design life with cost effective materials. The objectives of the research are to: • evaluate resilient modulus of typical fine-grained soils under traffic loading. • evaluate resilient modulus, permanent deformation, and permeability of typical unbound granular materials. • evaluate the effect of moisture and fines fraction on the performance of unbound granular materials and subgrade soil. • develop prediction models for resilient modulus to improve reliability of Level 2 inputs in the Pavement ME. • provide test data in support of updating Manitoba Infrastructure and Transportation specifications for unbound granular materials to improve the performance of pavement structures. Resilient modulus tests were conducted on three types of subgrade soil (high plastic clay, sandy clay, and silty sand/sandy silt) at four levels of moisture content. Resilient modulus, permanent deformation and permeability tests were conducted on six gradations representing two types of granular material (100% crushed limestone and gravel) at two levels of moisture content. Prediction models were developed for resilient modulus and compared to the models developed under the Long Term Pavement Performance program. The proposed models provided more reliable predictions with lower root mean square error. The deformation behaviour of the granular materials was classified according to the shakedown and dissipated energy approaches. Among the tested fines contents, limestone and gravel materials with optimum fines contents of 4.5% and 9%, respectively, had better resistance to plastic deformation and higher resilient modulus. The dissipated energy approach can be used to determine the stress ratio for the boundary between post compaction and stable zones from multistage triaxial testing. Result of permeability tests showed that the hydraulic conductivity of unbound granular material increased as the fines content decreased. / February 2016

Although clays are generally considered stable materials under seismic conditions, recent failures initiated in clay layers after earthquakes have emphasized the need to study the cyclic and post-cyclic behavior of these materials. Moreover, if strength loss as a result of cyclic loading were to occur in the material comprising the dam and/or dam foundation, the consequences of failure could be substantial. The objective of this study is to evaluate the effect of plasticity characteristics, mineralogical composition, and accumulated energy on the cyclic behavior, post-cyclic shear strength and the degradation in shear strength due to cyclic loading in normally consolidated clays. Seventeen soil samples prepared in the laboratory from kaolinite, montmorillonite, and quartz were tested using static and cyclic simple shear apparatuses. In addition, the results of cyclic simple shear tests on twelve natural samples were provided by Fugro Consultants, Inc. in Houston, TX. Using the results, cyclic strength curves were developed to represent 2.5%, 5% and 10% double amplitude shear strains. These curves were used to examine the influences of mineralogical composition, plasticity characteristics and shear strain on the cyclic resistance of soil samples. A power function was used to represent the cyclic strength curves. The samples were found to become increasingly resistant to cyclic loading as the plasticity index increased. Moreover, the soils with montmorillonite as the clay mineral were noted to have consistently higher cyclic resistances than the soils with kaolinite as the clay mineral. By examining the power functions, it was found that the cyclic strength curve approaches linearity as the plasticity index increases in soils having kaolinite as the clay mineral. However, the opposite trend is observed in soils having montmorillonite as the clay mineral. The study shows that the post-cyclic shear strength increases with increasing plasticity index. Moreover, the post-cyclic shear strengths of soils with montmorillonite as the clay mineral were significantly higher than the post-cyclic shear strengths of soils with kaolinite as the clay mineral. The degradation in shear strength due to cyclic loading appeared unaffected by mineralogy, but a greater reduction in strength was noted with decreasing plasticity index. The post-cyclic shear strength was also found to reduce as the number of cycles required to cause 10% double amplitude shear strain increased. The energy approach considering the accumulated energy per unit volume in the soil mass as a result of cyclic loading was also utilized in this study. The results from the energy approach were independent of the cyclic wave form, but were still dependent on the amplitude of the cyclic load used during the testing. An increase in the amplitude of the cyclic loading function results in a decrease in the accumulated energy per unit volume. Furthermore, an increase in the liquid limit and/or plasticity index of the soils containing kaolinite as the clay mineral shows an increase in the accumulated energy, whereas an increase in plasticity of the soils containing montmorillonite as the clay mineral results in a decrease in the amount of accumulated energy. In both types of materials, the amount of accumulated energy per unit volume is found to increase with increasing double amplitude shear strain. Relationship between the ratio of post-cyclic undrained shear strength to the baseline undrained shear strength and the accumulated energy is also determined. / Ph. D.