A model to determine the time to the End of Functional Service Life (EFSL) for concrete bridge decks in Virginia was developed. The service life of Virginia bridge decks is controlled by chloride-induced corrosion of the reinforcing steel. Monte Carlo resampling techniques were used to integrate the statistical nature of the input variables into the model. This is an improvement on previous deterministic models in that the effect of highly variable input parameters is reflected in the service life estimations. The model predicts the time required for corrosion to initiate on 2% of the reinforcing steel in a bridge deck and then a corrosion propagation time period, determined from empirical data, is added to estimate the EFSL for a given bridge deck or set of bridge decks. Data from 36 Virginia bridge decks was collected in order to validate the service life model as well as to investigate the effect of bridge deck construction specification changes. The bridge decks were separated into three distinct groups: 10 bare steel reinforcement decks â 0.47 water/cement (w/c), 16 Epoxy-Coated Reinforcement (ECR) decks â 0.45 w/c, and 10 ECR decks â 0.45 w/(c+pozzolan). Using chloride titration data and cover depth measurements from the sampled bridge decks and chloride corrosion initiation values determined from the literature for bare steel, service life estimates were made for the three sets of bridge decks. The influence of the epoxy coating on corrosion initiation was disregarded in order to allow direct comparisons between the three sets as well as to provide conservative service life estimates. The model was validated by comparing measured deterioration values for the bare steel decks to the estimated values from the model. A comparison was then made between the three bridge deck sets and it was determined that bridge decks constructed with a 0.45 w/(c+p) will provide the longest service life followed by the 0.47 w/c decks and the 0.45 w/c decks, respectively. From this it can be inferred that the addition of pozzolan to the concrete mix will improve the long-term durability of a bridge deck while a reduction in w/c appears to be of no benefit. / Ph. D.

The highway network in the United States, specifically reinforced concrete bridges, is deteriorating at a rapid rate. It is known that chloride-induced corrosion of the reinforcing steel is one of the major causes of the deterioration of concrete bridge decks. Numerous bridge deck protection and overlay systems have been developed to reduce the deterioration rate caused by chloride-induced corrosion. This study investigated the service life of untreated concrete bridge decks and four bridge deck overlay systems: low-slump-dense concrete (LSDC), latex-modified concrete (LMC), micro-silica concrete (MSC), and preformed membranes with hot-mix asphalt overlays (PM-HMA). The research plan consisted of organizing and analyzing data obtained in a 1991 field survey of 52 bridges from various locations in the nation. The field survey was conducted to gather information on existing conditions of untreated and rehabilitated bridge decks. Corrosion measurements were taken to assess the performance of each technique. Statistical models that predict the percent of deterioration on a bridge deck and the corrosion rate for each technique were developed from the field survey data. The components of a deterioration model were combined to define the service life for each bridge deck overlay system and for untreated concrete bridge decks. Other service life estimates for untreated bridge decks and bridge deck overlay systems were also compared. Based on the statistical analysis and service life comparisons, a service life estimate was recommended for predicting the service life for three of the bridge deck overlay systems. / Master of Science

This diploma thesis deals with the design of a virtual twin of cross table MCV 754 QUICK from the Czech manufacturer Kovosvit MAS. The research part describes the basic principles of predictive maintenance methodology and virtual twin technology. The practical part includes a simplification of the initial cross table model. This model was then transferred to the simulation software MSC Adams, where it was optimized so that its behavior corresponds as closely as possible to the physical device. Several simulations were subsequently performed on the model. Then a concept for a predictive method for calculating the remaining service life of individual sections of the ball screw was presented. Simulations performed on a virtual twin served as a source of data to test the proposed method.

Master of Science / Department of Civil Engineering / Kyle Riding / Corrosion of reinforcing steel is one of the most common and serious causes of reinforced concrete deterioration. While corrosion is normally inhibited by a passive layer that develops around the reinforcing steel due to the high pH environment of the surrounding concrete, chlorides will break down this protective layer, leading to reinforcement corrosion. Decreasing the diffusivity of the concrete would slow the ingress of chlorides into concrete, and is one of the most economical ways to increase the concrete service life. Optimized concrete mixtures blending portland cement and supplementary cementing materials (SCMs) have become popular throughout the construction industry as a method of improving both fresh and long-term concrete properties such as workability, strength and porosity. It has been shown that use of Class F fly ash, silica fume and ground granulated blast furnace slag (GGBFS) in binary concrete mixture blends can result in a significant reduction in concrete diffusivity. This study investigates the ability of Class C fly ash and ternary concrete mixture blends to also aid in diffusivity reduction. In order to study the effect of incorporation of SCMs into concrete, mixtures containing Class C and Class F fly ash, silica fume and GGBFS were tested following the ASTM C 1556 procedures to measure the concrete’s apparent chloride diffusivity. Structure life cycles were modeled using the measured apparent chloride diffusivities with two finite-difference based life-cycle analysis software packages. To determine whether a correlation between diffusivity and deterioration due to freezing and thawing exists, samples were also tested for their ability to resist deterioration from freezing and thawing cycles using a modified ASTM C 666 Procedure B test. Results show that the use of Class C fly ash yields some service life improvements as compared to the portland cement control mixtures, while ternary mixture blends performed significantly better than the control mixture and equal to or better than the binary SCM mixtures tested. Freeze-thaw tests showed all mixtures to be equally resistant to deterioration due to freezing and thawing.

A energia elétrica é, sem dúvida, um recurso indispensável para a sociedade moderna. A mesma revolucionou o modo de vida do ser humano em todos os aspectos e melhorou substancialmente sua qualidade de vida. A distribuição da energia elétrica cabe ao Sistema Elétrico de Potência – SEP, dividido basicamente em três macro setores: geração, transmissão e distribuição. A eletricidade é efetivamente entregue aos consumidores pelo sistema de distribuição, formado principalmente por redes aéreas sustentadas por postes, estes na sua maioria, feitos de concreto armado. Tendo em vista o adequado fornecimento da energia elétrica à sociedade, se faz necessário assegurar as linhas de distribuição de energia, na qual os postes exercem papel fundamental. Entende-se que o aumento da vida útil dos postes de concreto armado pode colaborar para a redução da manutenção da rede de distribuição, reduzindo o investimento em substituições ou reparos em postes por parte das concessionárias Deste modo, esse trabalho propõe a otimização do traço utilizado na produção de postes de concreto armado em uma empresa de artefatos de concreto, visando à vida útil do mesmo. Para tanto foram realizados estudos visando o aprimoramento da composição dos agregados, adição de material pozolânico, adição de fibras e utilização de aditivos superplastificantes. Para análise dos traços em escala real foram moldados 12 postes, tipo duplo T com 9 metros de comprimento, empregando 5 traços com características distintas. Os postes foram avaliados seguindo a metodologia e requisitos da NBR 8451-1 (ABNT, 2011), parâmetros de resistência mecânica do concreto e penetração de íons cloreto ASTM C1202 (2012). Por meio da análise dos resultados, é apresentado o traço indicado para produção de postes de concreto armado, onde foi possível aprimorar o traço atualmente produzido pela empresa, reduzindo o consumo de cimento de 429 kg/m³ para 351 kg/m³ e reduzindo a taxa de penetração de íons cloreto e aumentando a vida útil do poste de concreto armado de 10 para 60 anos. À vista disso, foi possível aumentar a vida útil do elemento, mesmo com a redução do consumo de cimento e o custo para a produção do traço de concreto. / Electricity is undoubtedly an indispensable resource for modern society. The same has revolutionized the way of life of the human being in all aspects and substantially improved their quality of life. The distribution of electricity is up to the Electric Power System - EPS, basically divided into three macro sectors: generation, transmission and distribution. Electricity is actually delivered to consumers by the distribution system, consisting mainly of overhead lines supported by pylons, these mostly made of reinforced concrete. Given the adequate supply of electricity to society, it is necessary to ensure the power distribution lines, in which the poles play a fundamental role. It is understood that increasing the useful life of reinforced concrete poles can contribute to the reduction of maintenance of the distribution network, reducing investment in replacements or repairs on poles by concessionaires. Thus, this paper proposes the optimal trait used in the production of reinforced concrete poles on a firm concrete artifacts, seeking the life of it For both studies were performed in order to improve the composition of households, adding pozzolanic material, adding fiber and use of superplasticizers additives. For analysis of traces in real scale 12 posts, T type double with 9 feet long, employing five traits were shaped with distinct characteristics. The posts were evaluated following the methodology and requirements of NBR 8451-1 (ABNT, 2011), the mechanical response of concrete and chloride ion penetration ASTM C1202 (2012). By analyzing the results, the dash indicated for production of reinforced concrete poles, where it was possible to improve the trace currently produced by the company, reducing the cement content of 429 kg / m³ to 351 kg / m³ and reducing the rate appears penetration of chloride ions and increasing the service life of reinforced concrete post 10 to 60 years. In view of this, it was possible to extend the life of the element, even with the reduction in cement consumption and the cost for the production of concrete mix.

<p>The valuation of an asset is one of the most important thing with accounting, though one of the most difficult thing as well. However, in deciding useful service life for an intangible asset and property, plant and equipment, there are quite a margin for the companies, which creates a difference between companies and industries. When computing the value of the inventories there are a few possibilities available for the companies, which also can generate differences</p><p>between companies and industries. Although these differences can occur, there might be some similarities in the companies’ estimates. Hence, the purpose of this essay is to establish whether there are any differences in how companies are assessing their useful service life of intangible assets, property, plant and equipment and deciding the value of inventories. To be able to accomplish the purpose, company’s annual reports were used along with other necessary sources, for instance books about accounting principles and theories. The study, furthermore, concluded that there are small differences between companies within the same industry and industries altogether, in their judgment on useful service life and the value of the inventories.</p>

The valuation of an asset is one of the most important thing with accounting, though one of the most difficult thing as well. However, in deciding useful service life for an intangible asset and property, plant and equipment, there are quite a margin for the companies, which creates a difference between companies and industries. When computing the value of the inventories there are a few possibilities available for the companies, which also can generate differences between companies and industries. Although these differences can occur, there might be some similarities in the companies’ estimates. Hence, the purpose of this essay is to establish whether there are any differences in how companies are assessing their useful service life of intangible assets, property, plant and equipment and deciding the value of inventories. To be able to accomplish the purpose, company’s annual reports were used along with other necessary sources, for instance books about accounting principles and theories. The study, furthermore, concluded that there are small differences between companies within the same industry and industries altogether, in their judgment on useful service life and the value of the inventories.

Wood pulp fibers are a unique reinforcing material as they are non-hazardous, renewable, and readily available at relatively low cost compared to other commercially available fibers. Today, pulp fiber-cement composites can be found in products such as extruded non-pressure pipes and non-structural building materials, mainly thin-sheet products. Although natural fibers have been used historically to reinforce various building materials, little scientific effort has been devoted to the examination of natural fibers to reinforce engineering materials until recently. The need for this type of fundamental research has been emphasized by widespread awareness of moisture-related failures of some engineered materials; these failures have led to the filing of national- and state-level class action lawsuits against several manufacturers. Thus, if pulp fiber-cement composites are to be used for exterior structural applications, the effects of cyclical wet/dry (rain/heat) exposure on performance must be known. Pulp fiber-cement composites have been tested in flexure to examine the progression of strength and toughness degradation. Based on scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), energy dispersive spectroscopy (EDS), a three-part model describing the mechanisms of progressive degradation has been proposed: (1) initial fiber-cement/fiber interlayer debonding, (2) reprecipitation of crystalline and amorphous ettringite within the void space at the former fiber-cement interface, and (3) fiber embrittlement due to reprecipitation of calcium hydroxide filling the spaces within the fiber cell wall structure. Finally, as a means to mitigate kraft pulp fiber-cement composite degradation, the effects of partial portland cement replacement with various supplementary cementitious materials (SCMs) has been investigated for their effect on mitigating kraft pulp fiber-cement composite mechanical property degradation (i.e., strength and toughness losses) during wet/dry cycling. SCMs have been found to be effective in mitigating composite degradation through several processes, including a reduction in the calcium hydroxide content, stabilization of monosulfate by maintaining pore solution pH, and a decrease in ettringite reprecipitation accomplished by increased binding of aluminum in calcium aluminate phases and calcium in the calcium silicate hydrate (C-S-H) phase.

Aerospace design requirements mandate acceptable levels of structural failure risk. Probabilistic fatigue models enable estimation of the likelihood of fatigue failure. A key step in the development of these models is the accurate inference of the probability distributions for dominant parameters. Since data sets for these inferences are of limited size, the fatigue model parameter distributions are themselves uncertain. A hierarchical Bayesian approach is adopted to account for the uncertainties in both the parameters and their distribution. Variables specifying the distribution of the fatigue model parameters are cast as hyperparameters whose uncertainty is modeled with a hyperprior distribution. Bayes' rule is used to determine the posterior hyperparameter distribution, given available data, thus specifying the probabilistic model. The Bayesian formulation provides an additional advantage by allowing the posterior distribution to be updated as new data becomes available through inspections. By updating the probabilistic model, uncertainty in the hyperparameters can be reduced, and the appropriate level of conservatism can be achieved. In this work, techniques for Bayesian inference and updating of probabilistic fatigue models for metallic components are developed. Both safe-life and damage-tolerant methods are considered. Uncertainty in damage rates, crack growth behavior, damage, and initial flaws are quantified. Efficient computational techniques are developed to perform the inference and updating analyses. The developed capabilities are demonstrated through a series of case studies.

Landfill facilities are required to have a barrier system that will limit escape of contaminants to groundwater and surface water for the contaminating lifespan of landfill. Heat generated by the biodegradation of waste and chemical reactions in landfills reduces the service-life of geomembranes by accelerating the ageing process of high-density polyethylene. It may also lead to the desiccation of clay components of the liners. Four considerations with respect to the evaluation of the potential effects of liner temperature on the service-life of liners and the potential control of liner temperature are examined. For the first time, the likely temperature and service-life of a secondary geomembrane in a double composite lining system is predicted. It is shown that, in some cases, the temperature is likely to be high enough to substantially reduce the service-life of the secondary geomembrane. The possible effectiveness of using tire chips as passive thermal insulation between the primary and secondary liners, as well as traditional soil materials, is then explored. For the barrier system and contaminant examined, the results show that tire chips could potentially lower the temperature of the secondary geomembrane sufficiently to significantly extend its service-life. However, the use of tire chips brings about other practical issues, which are also discussed in this study. An active alternative method of controlling the increase in the landfill liner temperature is then examined. This approach, which is inspired by geothermal heat pumps, involves an array of cooling pipes beneath the waste. Numerical modelling showed that the hypotetical introduction of the cooling pipes resulted in a reasonable decrease in liner temperature. It is suggested that the proposed technique warrants further consideration. Finally the conditions that may lead to the desiccation of geosynthetic clay liners used in composite liners due to waste generated heat are examined and recommendations regarding possible means of mitigating the effects of heat on the performance of GCLs are presented. For example, numerical modelling shows that the hydration of GCL prior to waste placement, liner temperature, overburden stress, depth to aquifer and moisture content and grain size of subsoil affect desiccation. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2011-07-31 07:34:33.165