Submitted by William Justo Figueiro (williamjf) on 2015-08-27T19:47:53Z No. of bitstreams: 1 29e.pdf: 335203 bytes, checksum: 3ac41cb81e40dd080004ab5aace97732 (MD5) / Made available in DSpace on 2015-08-27T19:47:53Z (GMT). No. of bitstreams: 1 29e.pdf: 335203 bytes, checksum: 3ac41cb81e40dd080004ab5aace97732 (MD5) Previous issue date: 2012 / Nenhuma / Os registros de uso de crack no Brasil, nos últimos anos, têm aumentado, causando uma preocupação da sociedade como um todo, devido aos problemas decorrentes da dependência da droga. O tratamento da dependência, bem como a cessação do uso são objetivos possíveis de alcançar, uma vez que já existem usuários que conseguem se abster do crack. O objetivo deste estudo foi estudar as condições associadas à abstinência de crack. Trata-se de um estudo transversal, exploratório com amostragem em bola de neve, que reuniu 495 indivíduos vinculados a diferentes serviços de saúde da região metropolitana de Porto Alegre (RS) em virtude do uso de crack, que responderam um questionário pré-codificado, padronizado e pré-testado. Os dados foram submetidos à análise multivariada por regressão de Poisson com ajuste robusto da variância para estimar a razão de prevalência do desfecho abstinência, definido como referência a intervalos iguais ou superiores a 12 semanas desde o último episódio de consumo. Permaneceram em associação com abstinência: não ter companheiro/a (RP: 1.11 IC 95%: 1.04-1.19, p=0.004), ter familiar em atendimento em saúde mental (RP: 1.10 IC 95%: 1.03-1.17, p=0.004), luto nos últimos 12 meses (RP: 1.07 IC 95%: 1.02-1.13, p=0.007), dificuldades sexuais atribuídas ao crack (RP: 1.08 IC 95%: 1.03-1.13, p=0.003) e reconhecimento de comunidades terapêuticas como recurso efetivo (RP: 1.10 IC 95%: 1.02-1.18, p=0.016). Apareceram em associação negativa com abstinência: já ter fumado crack com pai (RP: 0.83 IC 95%: 0.73-0.95, p=0.009), dependência do crack (RP: 0.91 IC 95%: 0.83-0.99, p=0.038), autopercepção de saúde muito ruim (RP: 0.56 IC 95%: 0.53-0.58, p=0.000) e escore no BDI leve (RP: 0.93 IC 95%: 0.87-0.98, p=0.002) moderado (RP: 0.89 IC 95%: 0.82-0.96, p=0.002).

Os Transtornos por Uso de Substâncias (TUS) são propostos pela Associação Norte-Americana de Psiquiatria e englobam diversas dependências químicas, incluindo o tabagismo e a dependência de crack. O uso de crack tem aumentado consideravelmente nos últimos anos, segundo dados de levantamentos brasileiros e mundiais. Com mecanismo de ação semelhante ao da cocaína, porém com efeito mais rápido, o crack é uma droga que causa grave prejuízo a seus usuários e conduz à dependência em pouco tempo. O tabagismo também é uma condição bastante prevalente no mundo inteiro, sendo que os prejuízos relacionados a esse transtorno envolvem principalmente o desenvolvimento de doenças respiratórias e câncer. Diversos trabalhos têm buscado identificar fatores de suscetibilidade a esses transtornos, sendo que estudos de associação envolvendo genes do sistema de resposta a estresse vêm ganhando importância. O eixo Hipotálamo- Pituitária-Adrenal (HPA) é o sistema de resposta a estresse mais conhecido em humanos e alvo do presente trabalho, uma vez que o funcionamento dessa cascata de sinalização da produção de cortisol pode desempenhar um papel relevante no desenvolvimento de psicopatologias. Além disso, o eixo HPA pode ser considerado um mediador da relação entre situações adversas na infância e o surgimento de TUS. O objetivo desse trabalho, portanto, é investigar o papel de polimorfismos no gene CRHR1 (que codifica o receptor tipo 1 do hormônio liberador de corticotrofina – CRH, hormônio inicial do eixo HPA) sobre o desenvolvimento e características clínicas da dependência química. Para isso, foram realizados dois estudos, envolvendo amostras de mulheres. No primeiro artigo, a partir de três amostras – (1) 136 usuárias de crack, (2) 55 tabagistas e (3) 262 voluntárias saudáveis – foram identificadas diferenças de freqüências alélicas e genotípicas do SNP rs12944712; além disso, a análise de haplótipos envolvendo tal SNP e o rs110402 revelou maior frequência do haplótipo contendo o alelo G nos dois polimorfismos nos grupos de usuárias de crack e tabagistas. No segundo artigo, foi avaliado o efeito da interação geneambiente envolvendo os mesmos polimorfismos e situações adversas na infância – estimada pela escala Childhood Trauma Questionnaire (CTQ) –sobre características clínicas da amostra de usuárias de crack, como craving e gravidade da dependência – estimados, respectivamente, pelas escalas Cocaine Selective Severity Assessment (CSSA) e Addiction Severity Index (ASI6). A análise não revelou uma interação significativa. A presente dissertação, portanto, revela um efeito do gene CRHR1 sobre o desenvolvimento de TUS, embora esse efeito pareça não se manifestar sobre a gravidade. Mais estudos são necessários visando esclarecer o real efeito do gene e do eixo HPA como um todo sobre os fenótipos e comportamentos aditivos, bem como os mecanismos subjacentes a essa relação. / The Substance Use Disorders (SUD) are proposed by the American Psychiatric Association and comprise several addictions, including tobacco and crack cocaine smoking. The prevalence of crack cocaine dependence has grown considerably, according to survey data from Brazil and worldwide. With mechanism of action similar to cocaine but with faster effect, crack is a drug that causes severe impairments to its users and leads to dependence in a short time. Tobacco smoking is also a highly prevalent condition worldwide, and the impact related to this disorder includes cancer and respiratory diseases. Several studies have attempted the identification of susceptibility factors to these disorders, and association studies involving stress response system genes have been performed. The Hypothalamic-Pituitary-Adrenal (HPA) axis is the best known stress response system, and the signaling cascade production of cortisol may play a role in the development of psychopathology. In addition, HPA axis can be considered a mediator of the relationship between early life adversity and SUD. The aim of this study is to investigate the role of polymorphisms in CRHR1 gene (encoding the corticotrophin releasing factor – CRH – receptor type 1, an initial factor in HPA axis response) on the development and clinical traits of drug dependence. Two studies were conducted on women samples. In the first article, three groups were compared - (1) 136 crack smokers, (2) 55 tobacco smokers and (3) 262 healthy volunteers. Differences in allele and genotype frequencies of the SNP rs12944712 were identified; in addition, the haplotype analysis involving this SNP and rs110402 revealed a higher frequency of the haplotype containing G allele in both polymorphisms in the groups of nicotine dependents and crack smokers. In the second article, we evaluated the effect of a gene-environment interaction involving the same polymorphisms and childhood adversity - estimated by Childhood Trauma Questionnaire (CTQ) scale – on clinical characteristics of the sample of crack users, such as craving and severity of dependence - estimated respectively by the Cocaine Selective Severity Assessment (CSSA) and Addiction Severity Index (ASI6) scales. The analysis did not reveal a significant interaction. This dissertation thus shows an effect of CRHR1 genepolymorphism on the development of SUD, although this effect does not seem to impact disorder severity. More studies are needed in order to clarify the actual effect of the gene and of the HPA axis as a whole on addictive behaviors.

Introdução: O consumo de crack tem sido alvo de grande preocupação em vista de sua expressiva expansão e dos problemas sociais e de saúde decorrentes. A cocaína na forma de crack difere das outras vias de uso principalmente pelo seu rápido início de ação, pouco tempo de efeito e alta concentração plasmática, levando a um maior impacto orgânico e a um elevado potencial de dependência. A deterioração física e cognitiva são aspectos centrais na gravidade do uso dessa droga. As taxas de infecção pelo HIV e HCV são elevadas nessa população, mas os fatores de risco associados ainda não estão claros na literatura, em particular no Brasil. Há uma busca por marcadores biológicos que possam auxiliar a avaliar o impacto físico e cerebral ocasionados pelo uso do crack. Achados recentes sugerem que as neurotrofinas cerebrais e marcadores de estresse oxidativo possam ser úteis nesse sentido. Objetivos: Avaliar a prevalência e fatores de risco associados à infecção por HIV e HCV em mulheres usuárias de crack e investigar se os níveis de BDNF, TBARS e PCC em usuários de crack, antes e após desintoxicação, diferem de controles e respectivos correlatos clínicos. Método: O artigo 1 utiliza um desenho transversal com uma amostra de conveniência de 76 mulheres com uso recente de crack. Foram coletados sangue para os testes de HIV/HCV, dados demográficos e instrumentos que avaliaram conhecimento sobre AIDS, consumo de drogas e comportamentos de risco para AIDS. No artigo 2 uma coorte com 49 usuários de crack homens foram recrutados da internação do Hospital Psiquiátrico São Pedro em Porto Alegre e 97 controles comunitários foram obtidos de um bairro pobre da cidade de Canoas (região metropolitana de Porto Alegre). O sangue para análise de BDNF (artigo 2), TBARS e PCC (resultados complementares) foi coletado no primeiro dia de internação e no dia da alta nos usuários de crack e no dia da entrevista nos controles. Nas duas amostras e nos controles os participantes tinham mais de 18 anos e realizaram teste de urina para cocaína. Resultados: No artigo 1, a prevalência de HIV entre as mulheres foi de 37,0% e de HCV de 27,7%, sendo 15,1% a prevalência de co-infecção. A análise ajustada identificou 4 anos ou menos de escolaridade como maior chance de infecção por HIV – RC 4,72 (1,49-14,99) e por HCV RC - 4,51 (1,18-17,27) e ter realizado 3 ou mais testes para HIV na vida - RC 4,26 (1,29-14,04) associado com contaminação por HIV. No artigo 2, os níveis de BDNF entre homens usuários de crack foram significativamente menores na admissão (28,6±11,0) quando comparados com os controles (39,5±10,6) e com o valor na alta hospitalar (35,6±12,3), mesmo após ajuste para as variáveis confundidoras. O valor do BDNF na alta foi um pouco menor nos usuários de crack, mas sem diferença significativa em relação aos controles. O aumento do BDNF teve associação significativa com número de dias de internação e inversa com anos de uso de crack e número de pedras de crack utilizadas no último mês. Os resultados complementares mostram que os valores médios de TBARS e PCC são semelhantes na internação e alta em relação aos controles. Contudo, o valor do TBARS na alta e a alteração durante a internação foram diretamente correlacionados com a gravidade do consumo de crack. Conclusões: Nós encontramos uma alta prevalência de contaminação por HIV e HCV entre mulheres usuárias de crack e o baixo nível educacional foi o fator de risco mais importante identificado. Em relação aos valores de BDNF em homens, foi possível identificar que este se encontra reduzido na vigência do uso de crack, com aumento na abstinência precoce, passando a ter níveis comparáveis aos controles. O aumento do BDNF e a diminuição do TBARS durante a abstinência precoce foram relacionados à menor gravidade de uso do crack. Esses achados sugerem que as variações de BDNF e TBARS após desintoxicação inicial possam ser marcadores da gravidade do uso de crack e de prognóstico, a serem investigados em futuros estudos. / Background: Crack cocaine has a been subject of great concern in view of its widespread use, as well as its increasing social and health problems. Crack cocaine differs from other administration routes primarily by its rapid onset of action, short effect and high plasma concentrations, leading to a higher organic impact and high potential for addiction. Physical and cognitive deterioration are key aspects of crack cocaine induced impairment. Rates of HIV and HCV are high in this population, but risk factors are still unclear in the literature, particularly in Brazil. There is search for biomarkers that may help identify the physical and brain injuries caused by its use. Recent findings suggest that brain neurotrophins and oxidative damage markers may be useful in this regard. Objectives: To ascertain the HIV/HCV serostatus and associated risk behaviors for infection of female crack users. To evaluated BDNF, TBARS and carbonyl levels among crack cocaine users during inpatient treatment, before and after drug withdrawal, vs. healthy controls. Clinical correlates with changes in biomarkers levels were also assessed. Method: Paper 1 is a cross-sectional study with a convenience sample of 76 female crack cocaine users. Subjects answered NIDA’s Risk Behavior Assessment and the AIDS Information Questionnaire. In addition, blood was collected from subjects for HIV/HCV tests. Blood samples for serum BDNF (paper 2), TBARS and PCC (complementary results) evaluations were collected in a cohort of 49 male crack users on the first and last days of hospitalization and in 97 healthy controls. In both samples and in the control group subjects were 18 years old or more and underwent urine tests for cocaine. Results: In paper 1, the overall prevalence of HIV was 37.0%; HCV seroprevalence was 27.7%; 15.1% of the sample was co-infected with HIV and HCV. Four years of schooling or fewer (OR 4.72 - CI 95% ((1.49-14.99)) was associated with HIV and HCV infection (OR 4.51 - CI 95% (1.18-17.27)) after multivariate logistic regression. In paper 2 BDNF levels among male crack users were significantly lower upon admission (28.6±11.0) when compared to controls (39.5±10.6) and discharge (35.6±12.3), even after adjustment for confounding variables. At discharge, BDNF levels between patients and controls were similar. Number of crack rocks used in the last 30 days and years of crack use were inversely correlated with the outcome. Complementary results show that levels of carbonyl and TBARS are similar at admission and discharge compared to controls. However, the TBARS levels at discharge and its variation rate during hospitalization were significantly correlated with the severity of crack cocaine use. Conclusions: We found a very high prevalence of HIV and HCV infection among female crack users, and low education was the most important risk factor associated with both infections. With regard to BDNF levels among men, it was reduced while using crack cocaine increased in early withdrawal reaching levels similar to control group at discharge. Rates of BDNF increase and TBARS decrease were correlated with severity of crack use. These findings suggest that the variation of BDNF and TBARS during early withdrawal may be a marker of severity of crack use.

A presente dissertação abordou o nível sérico da Cocaine and Amphetamine Regulated Transcript (CART) em uma população altamente vulnerável – díades mães/bebês com história de exposição ao crack na gestação. A CART é um antioxidante endógeno presente desde o período embrionário e ativado por maiores níveis de dopamina. Foram avaliados 57 recém-nascidos expostos (RNE) e 99 não expostos (RNNE), e as suas mães. Utizou-se uma amostragem consecutiva, em um delineamento transversal. Foram considerados potenciais confundidores: dados maternos, como psicopatologia, QI, intensidade do uso de outras substâncias além de crack nos últimos três meses, doenças infecto-contagiosas e outros. Também foram considerados dados dos recém-nascidos (RNs), como apgar, peso e gênero, entre outros. No primeiro artigo, foram comparados os níveis de CART entre RNs com exposição intrauterina (EIU) ao crack vs RNs controles. Além disso, comparamos os níveis séricos de CART entre as mães desses RNs, no período pós-parto imediato. A análise estatística foi através de General Linear Model. A média ajustada da CART foi significativamente maior em RN expostos em comparação aos não expostos (0,18, IC95% 0,09 - 0,27 vs 0,05, IC95% 0,02 - 0,07; p = 0,002, d = 0,68), mesmo considerando-se o efeito da intensidade do uso de álcool nos últimos três meses. Já nas mães, não houve diferença nos níveis da CART entre expostas (mediana = 0,024, amplitude interquartil 1,123, amplitude 0,006222 – 1,126010, n = 44) e não expostas (mediana = 0,031, amplitude interquartil 3,439, amplitude 0,003739 – 3,442805, n= 90, p = 0,08, Mann-Whitney U Test). No segundo artigo, foi analisada a correlação (Spearman correlation test) entre CART no SCU e no sangue periférico materno das usuárias de crack desta mesma amostra. Encontramos correlação direta e moderada (rs= 0,350, p = 0,043). Através dos resultados do primeiro estudo, confirmamos alterações no sistema REDOX destas díades, sendo a CART mais mobilizada na dupla com exposição. A falta de diferença entre as puérperas sugere que a resposta antioxidante endógena possa variar de acordo com a etapa do ciclo vital e, talvez, a cronicidade do estressor – no caso, tempo de uso de crack. Através dos resultados do segundo artigo, concluímos que há um sistema antioxidante endógeno atuando desde cedo no feto em desenvolvimento. Em conjunto, trata-se de dados inovadores, com características de neuroproteção em RNs. Estes achados podem ajudar a elucidar os caminhos neurobiológicos responsáveis pelas alterações de neurodesenvolvimento, contribuindo para a ampliação das possibilidades de intervenções precoces. / The present master’s dissertation addressed the serum level of Cocaine and Amphetamine Regulated Transcript (CART) in a highly vulnerable population - mother/newborn dyads with a history of exposure to crack/cocaine during pregnancy. CART is an endogenous antioxidant present since the embryonic period and activated by higher levels of dopamine. We evaluated 57 exposed and 99 unexposed infants, and their mothers. A consecutive sampling was used in a cross-sectional design. Potential confounders were considered: maternal data, such as psychopathology, IQ, intensity of use of other substances besides crack/cocaine in the last three months, infectious diseases and others. Data on newborns, such as apgar, weight and gender, among others, were also considered. In the first article, we compared the levels of CART among newborns with intrauterine exposure to crack/cocaine vs newborns controls. In addition, we compared the serum levels of CART among the mothers of these newborns in the immediate postpartum period. The statistical analysis was through General Linear Model. The CART adjusted mean was significantly higher in exposed infants compared to non-exposed infants (0.18, 95% CI 0.09 - 0.27 vs 0.05, 95% CI 0.02-0.07, p = 0.002, D = 0.68), even considering the effect of the intensity of alcohol use in the last three months. In the mothers, there was no difference in the CART levels between exposed (median = 0.024, interquartile range 1,123, range 0.006222 - 1.126010, n = 44) and not exposed (median = 0.031, interquartile range 3,439, range 0.003739 - 3,442,805, n = 90, p = 0.08, Mann-Whitney U Test). In the second article, the correlation (Spearman correlation test) between CART in the umbilical cord blood (UCB) and the maternal peripheral blood of the crack/cocaine users of this same sample was analyzed. We found direct and moderate correlation (rs = 0.350, p = 0.043). Through the results of the first study, we confirmed changes in the REDOX system of these dyads, with CART being more mobilized in the pair with exposure. The lack of difference between postpartum women suggests that the endogenous antioxidant response may vary according to the stage of the life cycle and perhaps the chronicity of the stressor - in this case, crack/cocaine use duration. Through the results of the second article, we conclude that there is an endogenous antioxidant system acting at an early stage in the developing fetus. Together, these are innovative data, with characteristics of neuroprotection in newborns. These findings may help elucidate the neurobiological pathways responsible for neurodevelopmental changes, contributing to the expansion of the possibilities of early intervention.

This study reports a novel and simple technique for successfully coating multi-walled carbon nanotubes (MWCNTs) on to the surface of carbon fibre (CF) fabric for the production of multi-scale CF-epoxy composites. Initially, epoxy composites with multi-scale reinforcement were produced by resin infusion (RI) using woven CF fabric coated with a dispersion of 1 wt. % MWCNTs in an epoxy binder of low molar mass. The effects of this reinforcement on the CF-epoxy interface with MWCNTs was studied in mode I and mode II interlaminar fracture toughness (ILFT) using double-cantilever beam (DCB) and 4 point end-notch flexure (4ENF) tests, respectively. Relative to an equivalent composite reinforced with non-coated CF reinforcement, the binder/MWCNTs coating increased significantly the ILFT of the CF-epoxy composite; in mode I by 105% and in mode II by 50%. This increase in ILFT was attributed to two main effects: Firstly, the binder alone (without MWCNTs), which has a much lower glass transition temperature (Tg) than that the matrix (45 vs. 140 °C), hindered crack propagation and increased the ILFT of the epoxy matrix by 25% for mode I and 15% for mode II; Secondly, the energy absorbing mechanisms of MWCNTs during fracture particularly pull-out and crack bridging. However the Tg of the matrix epoxy of the multi-scale composites was reduced to 118 °C compared to 140 °C, for the unmodified composite, due to phase mixing with the low Tg binder. For RI processing, the CF volume fraction of the composites prepared using coated CF was ≈50% compare to at ≈55% for the composite with non-coated CF. Curing agents were added to the binder, which not only increased the Tg from ≈50 °C to ≈100 °C, but also increased the Tg of the matrix epoxy of the multi-scale composites to 154 °C. Relative to an equivalent composite reinforced with non-coated CF reinforcement, the curable-binder/MWCNTs coating increased the ILFT of the CF-epoxy composite; in mode I by 120% and in mode II by 90%. A hybrid RI-hot press (HP) process was used to prepare CF-epoxy composites from coated fabrics with CF volume fractions of ≈55%. The damping curves for the HP-composites consisted of a β-peak, due to the formation of a third mixed phase, in addition to a γ-peak (assigned to the Tg of the binder) and an α-peak (assigned to the Tg of matrix epoxy). The β-peak, and the uniformly distributed nodular particles observed on the fracture surface of the matrix, by SEM, for HP-composites, are indicative of the formation of mixed-phase particles due to reaction induced phase separation (RIPS). Relative to an equivalent RI-composite, the curable-binder/MWCNTs treatment increased the ILFT of the CF-epoxy multi-scale composite; in mode I by 134% and in mode II by 15% for HP-composites. Impact test results showed that HP-composites absorbed more energy, due to CF fracture, compared to equivalent RI composites, which showed larger delamination areas after 5 J and 10 J impact. The out-of-plane electrical conductivity and thermal conductivity of the HP-composite with CF coated with curable-binder/MWCNTs was increased by ≈38% and ≈50%, respectively, compared to the composite with non-coated CF, indicating formation of MWCNTs networks in the matrix rich areas of the multi-scale composite.

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Sociais, Departamento de Sociologia, 2015. / Debruçando-se sobre o atual cenário de consumo de crack no contexto brasileiro, as políticas públicas de enfrentamento a esta substância têm encontrado raízes no discurso da epidemia. Tal discurso, fundamentado a partir da construção social do pânico moral e da histeria social, é protagonizado fundamentalmente pela mídia e pelo poder público, a partir da manutenção de notícias diárias que envolvem o tema do crack, assim como de campanhas calcadas na perspectiva de horror e sofrimento. Tal afirmativa foi atestada na análise de mídia do jornal na cidade de Natal/RN denominado Tribuna do Norte. Partindo de um horizonte histórico que desenha o processo de proibição das drogas, o objeto central da pesquisa consistiu na análise da política pública intitulada “Crack, é Possível Vencer” e sua implementação na cidade de Natal/RN, resultado desta conjuntura epidemiológica a partir da necessidade de que algo deve ser feito para banir o “mal do crack” da sociedade. Para compreender a dimensão da implementação deste programa, foram utilizadas as entrevistas estruturadas com usuários de crack realizadas a partir do estudo multicêntrico Perfil dos usuários de crack nas 26 capitais, DF, 9 regiões metropolitanas e Brasil. A partir da análise teórica, concluiu-se que o programa “Crack, é Possível Vencer” é instrumentalizado para controlar as populações em situação de vulnerabilidades associadas e ampliar a gerência do capital nos espaços urbanos, e que o crack, por sua vez, é dispositivo para fortalecer o processo de criminalização da pobreza e de exclusão social. / The use of crack cocaine is regarded as one of the great social evils of the present days. Regarded as a vector element of an epidemic that kills and causes the death of an expressive amount of users, signaling that something must be urgently done by the state to solve this problem. As a response, the Brazilian government presents the plan “Crack, é Possível Vencer” (“Crack, it is possible to win”) as an instrument to face the threat that plagues the socially excluded population. Several investigations were pursued over the narrative of the crack epidemic through the analysis of news transmitted by the newspaper Tribuna do Norte, and the implementation of the “Crack, é Possível Vencer” plan in the city of Natal/RN was researched, through its axis of prevention, care and authority. Structured interviews were also done with users through the multicentric study Profile of Crack users in the 26 capitals, Federal District, 9 metropolitan regions and Brazil. Through the theoretical analysis it was concluded that the “Crack, é Possível Vencer” program is instrumentalized to control populations in the situation of associated vulnerabilities and to expand the management of capital in the urban spaces, and that crack is therefore a tool to strengthen the process of criminalization of poverty and social exclusion.

abstract: Pipeline infrastructure forms a vital aspect of the United States economy and standard of living. A majority of the current pipeline systems were installed in the early 1900’s and often lack a reliable database reporting the mechanical properties, and information about manufacturing and installation, thereby raising a concern for their safety and integrity. Testing for the aging pipe strength and toughness estimation without interrupting the transmission and operations thus becomes important. The state-of-the-art techniques tend to focus on the single modality deterministic estimation of pipe strength and do not account for inhomogeneity and uncertainties, many others appear to rely on destructive means. These gaps provide an impetus for novel methods to better characterize the pipe material properties. The focus of this study is the design of a Bayesian Network information fusion model for the prediction of accurate probabilistic pipe strength and consequently the maximum allowable operating pressure. A multimodal diagnosis is performed by assessing the mechanical property variation within the pipe in terms of material property measurements, such as microstructure, composition, hardness and other mechanical properties through experimental analysis, which are then integrated with the Bayesian network model that uses a Markov chain Monte Carlo (MCMC) algorithm. Prototype testing is carried out for model verification, validation and demonstration and data training of the model is employed to obtain a more accurate measure of the probabilistic pipe strength. With a view of providing a holistic measure of material performance in service, the fatigue properties of the pipe steel are investigated. The variation in the fatigue crack growth rate (da/dN) along the direction of the pipe wall thickness is studied in relation to the microstructure and the material constants for the crack growth have been reported. A combination of imaging and composition analysis is incorporated to study the fracture surface of the fatigue specimen. Finally, some well-known statistical inference models are employed for prediction of manufacturing process parameters for steel pipelines. The adaptability of the small datasets for the accuracy of the prediction outcomes is discussed and the models are compared for their performance. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2018

Vibration-based damage detection methods are used in structural applications to identify the global dynamic response of the system. The purpose of the work presented is to exhibit a vibration-based damage detection algorithm that calculates a damage indicator, based on limited frequency bands of the transmissibility function that have high coherence, as a metric for changes in the dynamic integrity of the structure. The methodology was tested using numerical simulation, laboratory experimentation, and field testing with success in detecting, comparatively locating, and relatively quantifying different damages while also parametrically investigating variables which have been identified as issues within similar existing methods. Throughout both the numerical and laboratory analyses, the results were used to successfully detect damage as a result of crack growth or formation of new cracks. Field results using stochastic operational traffic loading have indicated the capability of the proposed methodology in evaluating the changes in the health condition of a section of the bridge and in consistently detecting cracks of various sizes (30 to 60 mm) on a sacrificial specimen integrated with the bridge abutment and a floor beam. Fluctuations in environmental and loading conditions have been known to create some uncertainties in most damage detection processes; however, this work demonstrated that by limiting the features of transmissibility to frequency ranges of high coherence, the effect of these parameters, as compared to the effect of damage, become less significant and can be neglected for some instances. The results of additional field testing using controlled impact forces on the sacrificial specimen have reinforced the findings from the operational loading in detecting damage.

Concrete cylinder piles produced by a centrifugally cast, vibrated, roller compacted process have shown promising corrosion durability in marine environments. Three bridges in the Florida Panhandle with approximately 40 years of service in aggressive marine service were examined. A newly constructed marine bridge utilizing concrete cylinder piles was also examined to verify corrosion performance of piles manufactured with modern building materials and construction compared to piles built several decades ago. Survey of the marine bridges showed minimal corrosion distress despite low design concrete cover to steel hoop reinforcements (20-40 mm). Typical concrete distress included minor rust staining but not necessarily indicating corrosion of reinforcement steel. Thin longitudinal cracks were frequently observed but were likely caused by mechanical damage from pile driving rather than stemming from corrosion distress. Chloride ion diffusivity was low, in the order of 1x10-13 m2/s. Other measured parameters such as concrete resistivity, porosity, and water absorption indicate low permeability. Chloride analysis of cracked and uncracked concrete cores from the older bridges in this study did not show pronounced preferential chloride penetration. Chloride analysis from the contemporary marine bridge did show some preferential transport of chloride ions at shallow depths through cracks with further evidence of lower electrical resistivity indicating enhanced electrolyte transport. The pore water pH of concrete samples from the contemporary bridge was high despite the presence of pozzolanic materials suggesting that normal chloride threshold values may be valid.

This thesis is concerned with the characterisation of the parameters governing the tension-softening relations of the cohesive crack model. Parameter identification is an important area in fracture mechanics as it enables the use of a fracture model for the simulation of fracture processes in structures. Research, however, has shown that such a task is not trivial and continues to pose challenging problems to experimentalists and analysts alike. This dissertation presents general and efficient indirect methods for the characterisation of mode I fracture parameters defining the cohesive crack model. The identification problem is formulated as a special type of inverse problem. The formulation is in the form of a constrained optimisation problem known as a mathematical program with equilibrium constraints characterised, in the present instance, by complementarity conditions involving the orthogonality of two-sign constrained vectors. The solution of such a mathematical program is computationally challenging as it is disjunctive and nonconvex by nature. A number of nonlinear programming based approaches are proposed, after appropriate reformulation of the mathematical program as an equivalent nonlinear programming problem. Actual experimental data are used to validate and determine the most suitable algorithm for parameter identification. It was found that the smoothing-based method is by far superior than other schemes. As the problem is nonconvex and the nonlinear program can only guarantee a local or stationary point, global optimisation procedures are introduced in order to verify the accuracy of the solutions obtained by the algorithm. Two evolutionary search methods capable of finding the global optimum are implemented for parameter identification. The results generated by the evolutionary search techniques confirm the reliability of the solutions identified by the best nonlinear programming algorithm. All computations carried out in the thesis suggest the suitability and robustness of the selected algorithm for parameter identification.