O propósito do presente trabalho é desenvolver a avaliação estrutural de um navio \"Nodriza\" de pequeno porte de aplicação militar e cujo projeto inicial foi orientado à navegação em águas abrigadas com restrições de calado. Porém, requisitos e necessidades afetando a concepção inicial do projeto obrigam este a efetuar percursos em águas profundas com possibilidade de experimentar ciclos de onda. A avaliação estrutural pretende determinar o nível de influência da superestrutura sobre a resistência longitudinal do navio considerando-o submetido a esforços solicitantes próprios de águas não abrigadas. As limitações geradas pelas formas e proporções do navio Nodriza, que não permitem implementar de forma direta as regras de Sociedades Classificadoras para a avaliação estrutural em águas profundas, obriga ao uso de cálculos diretos para sua aprovação. Uma análise mediante o uso de elementos finitos, modelando o navio com e sem participação da superestrutura, permite determinar como esta representa uma significativa influência sobre a resistência longitudinal e tensões finais dos membros principais e membros de suporte, quando é considerada dentro da análise estrutural. Igualmente, implementam-se procedimentos determinísticos propostos pelas regras de sociedades classificadoras para navios convencionais, na procura de estabelecer a conveniência ou não da sua aplicação como método de aproximação para uma avaliação estrutural desta classe de navio militar, cujas características tornam dele um caso particular de análise. / The objective of the present work is to conduct a structural evaluation of the small size, military vessel Nodriza which has been designed for navigation in sheltered waters with draft restrictions. However, new requirements and changes in the operation of this vessel forced deep water navigation with the possible action of wave loading. The structural evaluation seeks to determine the effects of the superstructure on the longitudinal structural resistance for the vessel. Since the geometry and overall dimensions of the ship are not covered by the structural rules of the Classification Societies, a numerical analyses based on the finite element method is conducted for a full model of the vessel. The numerical analyses demonstrate the strong effect of the superstructure on the longitudinal resistance which yields reduced stress levels in primary structural members. The work provides a compelling support to use more refined procedures in the structural design of non-conventional small-sized vessels.

The objective of this research is to determine if the deflection equations currently adopted in ACI 440.1r-15 and previously ACI 440.1r-06 accurately reflect the flexural behavior of an overreinforced Basalt Fiber Reinforced Polymer (BFRP) concrete beam. This was accomplished with experimental, analytical and numerical models. The experiment consisted of two beams doublyreinforced with BFRP rebar. A three-point flexural test on beams with a 30 in. clear span was performed and the deflections were recorded with a dial gauge and LVDT system. This data was compared to the equations from ACI 440.1r-06, ACI 440.1r-15, Branson’s equation and a numerical model created in ANSYS Mechanical APDL. Experimental results show a stiffer beam than expected when compared to the four predictive models for deflection. This can be due to the level of over-reinforcement and the small clear-span to depth ratio. Further research should be conducted to determine the cause for the additional stiffness. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Research, tests and analysis are presented on several reinforcements placed in the asphalt overlay of a roadway built over soft organic soils. Non-destructive Evaluation (NDE) methods and statistical analysis were used to characterize the pavement before and after rehabilitative construction. Before reconstruction, falling weight deflectometer, rut and ride tests were conducted to evaluate the existing pavement and determine the statistical variability of critical site characteristics. Twenty-four 500ft. test sections were constructed on the roadway including sixteen reinforced asphalt and eight control sections at two test locations that possessed significantly different subsoil characteristics. NDE tests were repeated after reconstruction to characterize the improvements of the test sections. Test results were employed to quantify the stiffness properties of the pavement based on load-deflection data to evaluate the relative performance of the reinforced sections. Statistical analysis of the data showed the stiffness of the reinforced sections was consistently higher than the control sections. / by Daniel D. Pohly. / Thesis (M.S.C.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Studies of composite multihull structure under wave loads, extreme loads, and blast loads have been conducted using finite element and computational fluid dynamics (CPF) tools. A comprehensive finite element tool for structural analysis of composite multi-hull structures is developed. Two-way fluid structure interaction (FSI) is implemented by coupling finite element analysis (FEA) and CFD. FEA models have been developed using sandwich construction having composite face sheets and a foam core. Fluid domain was modeled using the CFD code, CFX and a wave motion was simulated based on Sea State 5... In addition to hydrodynamic loads, the simulation of composite ship under extreme loads is performed. Stress analysis was performed and dynamic response of the hull was determined in time domain. In the final analysis, an underwater explosion model was developed to study the composite hull resistance to blast load. / by Siyuan Ma. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Natural frequencies of the double and triple-walled carbon nanotubes are determined exactly and approximately for both types. Approximate solutions are found by using Bubnov-Galerkin and Petrov-Galerkin methods. For the first time explicit expressions are obtained for the natural frequencies of double and triple-walled carbon nanotubes for different combinations of boundary conditions. Comparison of the results with recent studies shows that the above methods constitute quick and effective alternative techniques to exact solution for studying the vibration properties of carbon nanotubes. The natural frequencies of the clamped-clamped double-walled carbon nanotubes are obtained; exact solution is provided and compared with the solution reported in the literature. In contrast to earlier investigation, an analytical criterion is derived to establish the behavior of the roots of the characteristic equation. Approximate Bubnov-Galerkin solution is also obtained to compare natural frequencies at the lower end of the spectrum. Simplified version of the Bresse-Timoshenko theory that incorporates the shear deformation and the rotary inertia is proposed for free vibration study of double-walled carbon nanotubes. It is demonstrated that the suggested set yields extremely accurate results for the lower spectrum of double-walled carbon nanotube. The natural frequencies of double-walled carbon nanotubes based on simplified versions of Donnell shell theory are also obtained. The buckling behavior of the double-walled carbon nanotubes under various boundary conditions is studied. First, the case of the simply supported double-walled carbon nanotubes at both ends is considered which is amenable to exact solution. / Then, approximate methods of Bubnov-Galerkin and Petrov-Galerkin are utilized to check the efficacy of these approximations for the simply supported double-walled carbon nanotubes. Once the extreme accuracy is demonstrated for simply supported conditions, the approximate techniques are applied to two other cases of the boundary conditions, namely to clamped-clamped and simply supported-clamped double-walled carbon nanotubes. For the first time in the literature approximate expression for the buckling loads are reported for these boundary conditions. The dynamic deflection of a single-walled carbon nanotube under impact loading is analyzed by following a recently study reported on the energy absorption capacity of carbon nanotubes under ballistic impact. / by Demetris Pentaras. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Support vector machines (SVMs) are a set of supervised learning methods that have recently been applied for structural damage detection due to their ability to form an accurate boundary from a small amount of training data. During training, they require data from the undamaged and damaged structure. The unavailability of data from the damaged structure is a major challenge in such methods due to the irreversibility of damage. Recent methods create data for the damaged structure from finite element models. In this thesis we propose a new method to derive the dataset representing the damage structure from the dataset measured on the undamaged structure without using a detailed structural finite element model. The basic idea is to reduce the values of a copy of the data from the undamaged structure to create the data representing the damaged structure. The performance of the method in the presence of measurement noise, ambient base excitation, wind loading is investigated. We find that SVMs can be used to detect small amounts of damage in the structure in the presence of noise. The ability of the method to detect damage at different locations in a structure and the effect of measurement location on the sensitivity of the method has been investigated. An online structural health monitoring method has also been proposed to use the SVM boundary, trained on data measured from the damaged structure, as an indicator of the structural health condition.

"This study presents a general approach for an inverse problem to locate a sudden structural damage in a plate. The sudden damage is modeled as an impulse load and response data are collected at various sensor locations. In this simulation study the response data were generated by the commercial finite element code ANSYS for three square plates: one is an isotropic plate and made of aluminum and the others are two different composite plates made of graphite-epoxy. All plates are simply supported along all their edges. The responses of these plates to both narrow band and wide band loading were analyzed by a wavelet transform. The wavelet coefficient maps for each type of signal was utilized to estimate the shortest path arrival times of flexural waves resulted from the damage by locating the wavelet coefficient peak values of the response data. Using the dispersion relations of wave propagation based on the Mindlin’s plate theory, a set of nonlinear equations were derived to solve this inverse problem and the location of the applied load, which models a structural damage, was determined. The estimated locations for all different types of plates have shown an excellent agreement with the actual location of the impact loads applied. "

A análise da continuidade espacial inclui uma série de ferramentas para estimar e modelar a continuidade de variáveis aleatórias regionalizadas. Ela é a base para muitas das avaliações de depósitos minerais baseadas na geoestatísitca. O modelo ajustado é de grande importância e influencia nos resultados em vários algoritmos de krigagem e simulações subsequentes. Tanto os softwares acadêmicos e comerciais podem melhorar no desenvolvimento dos gráficos, na interatividade com o usuário e no uso de formas automáticas de modelagem. O SGeMS (Stanford Geoestatistical Modeling Software) é um programa gratuito usado entre a comunidade de geoestatísticos ao qual tem um grande potencial de desenvolvimento, mas que, no entanto, ainda não possui todas as ferramentas de análise da continuidade espacial incorporadas. Diferentemente do SGeMS, o GSLIB é uma boa biblioteca gratuita para análise geoestatística e é mais completa, mas as estradas do programa são modificadas pela edição de arquivos .txt e usando linhas de comando o que torna a utilização do software pouco amigável com o usuário, apesar da robustez e qualidade dos programas da biblioteca. Dada as limitações dos mais usados e completos softwares gratuitos de geoestatística, essa dissertação objetiva a transcrição e adaptação do algoritmo do GSLIB (GamV .f) para o software SGeMS, modificando a lógica de programação para criar diferentes ferramentas auxiliares como h-scatterplots e mapas de variograma e covariograma. Os resultados demonstraram que a adaptação de algoritmos antigos leva a uma solução gratuita. Além disso, um algoritmo para a otimização da modelagem de variogramas pelo método dos mínimos quadrados foi desenvolvido. As rotinas foram desenvolvidas ambas em C++ e em Python. Os algoritmos foram validados com os valores obtidos pelo software GSLIB. Todos os desenvolvimentos dos plug-ins foram testados e validados usando dois casos ilustrativos: um depósito de ferro e um caso polimetálico. Os resultados provaram ser consistentes e similares com aqueles obtidos com softwares comerciais e renomados. / The spatial continuity analysis includes a serie of tools to estimate and model the continuity of regionalized random variables. It is the basics for many mineral deposit evaluation methods based on geostatistics. The model adjusted is of paramount importance and influences the results in many subsequent kriging and simulation algorithms. Both commercial and academic softwares can be improved in graphics, users interactivity with and automated tools for modeling spatial continuity. SGeMS (Stanford Geoestatistical Modeling Software) is a freeware program used among the geostatistical community which has an extremely potential for development however it does not have enough variographic or graphical tools. Unlike SGeMS, GSLIB is a good and more complete free library for geostatistical analysis, however the program inputs are modified by editing of .txt files and uses DOS command lines. This makes the software less user friendly, despite its robustness and quality. Given the limitation on both most used and complete freeware geostatistical softwares, this dissertation aims at transcripting and adpating an algorithm from GSLIB(GamV.f) into SGeMS software, handling the programming logic to create different auxiliary tools as h-scatterplot and variomaps. The results demonstrated that the adaptation of the old and stable algortihms lead to an inexpensive solution. Futhermore, an algorithm was developed for optimizing variogram modeling based on weigthed least squares method. The routines were developed in both C++ and Phyton. The algorithms were validated against actual values generated by GSLIB. All developed of plug-ins were tested and validated using two illustration studies: an iron ore deposit and a polymetallic one. The results proved to be consistent and similar to the ones obtained by commercial well known sofwares.

Structural identification is the inverse problem of estimating the physical parameters, e.g. element masses and stiffnesses, of a model representing a structural system, using response measurements obtained from the actual structure subjected to operational or well-defined experimental excitations. It is one of the principal focal areas of modal testing and structural health monitoring, with the identified model finding a wide variety of applications, from obtaining reliable response predictions to timely detection of structural damage (location and severity) and consequent planning and validating of maintenance/retrofitting operations. However, incomplete instrumentation of the monitored system and ambient vibration testing generally result in spatially incomplete and arbitrarily normalized measured modal information, often making the inverse problem ill-conditioned and resulting in non-unique identification results. The problem of parameter identifiability addresses the question of whether or not a parameter set of interest can be identified from the available information. The identifiability of any parameter set of interest depends on the number and location of sensors on the monitored system. In this dissertation we study the identifiability of the mass and stiffness parameters of shear-type systems, including 3-dimensional laterally-torsionally coupled rigid floor systems, with incomplete instrumentation, simultaneous to the development of algorithms to identify the complete mass and stiffness matrices of such systems. Both input-output and output-only situations are considered, and mode shape expansion and mass normalization approaches are developed to obtain the complete mass normalized mode shape matrix, starting from the incomplete modal parameters identified using any suitable experimental or operational modal analysis technique. Methods are discussed to decide actuator/sensor locations on the structure which will ensure identifiability of the mass and stiffness parameters. Several possible minimal and near-minimal instrumentation set-ups are also identified. The minimal a priori information necessary in output-only situations is determined, and different scenario of available a priori information are considered. Additionally, tests for identifiability are discussed for both pre- and post-experiment applications. The different theoretical discussions are illustrated using numerical simulations and experimental data. It is shown that the proposed identification algorithms are able to obtain reliably accurate physical parameter estimates even under the constraints of minimal instrumentation, minimal a priori information, and unmeasured input. The different actuator/sensor placement rules and identifiability tests are useful for both experiment design purposes, to determine the necessary number and location of sensors, as well as in identifying possibilities of multiple solutions post-experiment. The parameter identification methods are applied for structural health monitoring using experimental data, and an approach is discussed for probabilistic characterization of structural damage location and severity. A perturbation based uncertainty propagation approach is also discussed for the identification of the distributions of mass and stiffness parameters, reflecting the variability in the test structure, using very limited measured and a priori information.

A Bayesian approach to system identification for structural control and health monitoring contains three main levels of inference, namely model assessment, joint state/parameter estimation and noise estimation. All of them have individually, or as a whole, been studied extensively for offline applications. In an online setting, the middle level of inference (joint state/parameter estimation) is performed using various algorithms such as the Kalman filter (KF), the extended Kalman filter (EKF), the Unscented Kalman filter (UKF), or particle filter (PF) methods. This problem has been explored in depth for structural dynamics. This dissertation focuses on the other two levels of inference, in particular on developing methods to perform them online, simultaneously to the joint state/parameter estimation. The quality of structural parameter estimates depends heavily on the choice of noise characteristics involved in the aforementioned online inference algorithms, hence the need for simultaneous online noise estimation. Model assessment, on the other hand, is an integral part of many engineering applications, since any analytical or numerical mathematical model used for predictive purposes is only an approximation of the real system. An online implementation of model assessment is valuable, amongst others, for structural control applications, and for identifying several models in parallel, some of which might be of deteriorating nature, thus generating some sort of alert. The performance of the proposed online techniques is evaluated using simulated and experimental data sets generated by nonlinear hysteretic systems. Upon completion of the study of hierarchical online system identification (diagnostic phase/estimation), a system/damage prognostic analysis (prognostic phase/prediction) is attempted using a gamma deterioration process. Prognostic analysis is still at a relatively early stage of development in the field of structural dynamics, but it can potentially provide useful insights regarding the lifetime of a dynamically excited structural system. The technique is evaluated on a data set recorded during an experiment involving a full-scale bridge pier under base excitation, tested to impending collapse.