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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Structural classification of granular base pavements using measured deflection bowl parameters

Jooste, Fritz Joubert 15 April 2014 (has links)
M.Ing. (Civil Engineering) / The: structural classification of granular base pavements by means of resilient deflection bowl parameters measured by the Impulse Deflection Meter and application of measured deflections at network level were investigated. The Investigation consisted of a mechanistic analysis and an analysis of observed field results. Curves for structural classification of granular base pavements obtained by regression are presented. The Curves obtained by the analysis of field observations compare well with local experience and theoretical failure criteria. It was found that the mechanistic model used in this study did not yield satisfactory results when simulating deflection behaviour through linear elastic programs. The parameters recommended for future use are Maximum Deflection (Y-rnax), Base Layer Index, or DLl (formerly SCI), Middle Layer Index, or MLl (formerly DOl) and Radius of Curvature. The use of deflection measurements at network level was also investigated. A method for calculating a Structural Stiffness Index to be incorporated into Pavement Management Systems as a Structural Indicator is proposed. Recommendations regarding the density of testing and identification of roads for testing at network level are also made. Several factors influencing deflections and structural bearing capacity are discussed and some recommendation." are made. The main factors influencing deflections and predicted pavement structural capacity were shown to be Temperature, Seasonal Influences and Condition of Surfacing. Further research into the specific influence of these factors on deflections and hearing capacity is needed.
2

Bayesian decision analysis for pavement management

Bein, Piotr January 1981 (has links)
Ideally, pavement management is a process of sequential decisions on a network of pavement sections. The network is subjected to uncertainties arising from material variability, random traffic, and fluctuating environmental inputs. The pavement manager optimizes the whole system subject to resource constraints, and avoids sub optimization of sections. The optimization process accounts for the dynamics of the pavement system. In addition to objective data the manager seeks information from a number of experts, and considers selected social-political factors and also potential implementation difficulties. Nine advanced schemes that have been developed for various pavement administrations are compared to the ideal. Although the schemes employ methods capable of handling the pavement system's complexities in isolation, not one can account for all complexities simultaneously. Bayesian decision analysis with recent extensions is useful for attacking the problem at hand. The method prescribes that when a decision maker is faced with a choice in an uncertain situation, he should pick the alternative with the maximum expected utility. To illustrate the potential of Bayesian decision analysis for pavement management, the author develops a Markov decision model for the operation of one pavement section. Consequences in each stage are evaluated by multi-attribute utility. The states are built of multiple pavement variables, such as strength, texture, roughness, etc. Group opinion and network optimization are recommended for future research, and decision analysis suggested as a promising way to attack these more complex problems. This thesis emphasizes the utility part of decision analysis, while it modifies an existing approach to handle the probability part. A procedure is developed for Bayesian updating of Markov transition matrices where the prior distributions are of the beta class, and are based on surveys of pavement condition and on engineering judgement. Preferences of six engineers are elicited and tested in a simulated decision situation. Multi-attribute utility theory is a reasonable approximation of the elicited value judgements and provides an expedient analytical tool. The model is programmed in PL1 and an example problem is analysed by a computer. Conclusions discuss the pavement maintenance problem from the decision analytical perspective. A revision is recommended of the widespread additive evaluation models from the standpoint of principles for rational choice. Those areas of decision theory which may be of interest to the pavement engineer, and to the civil engineer in general, are suggested for further study and monitoring. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate
3

Evaluation of pavement joint sealants: a new testing technique

Abo-Qudais, Saad A. 10 November 2009 (has links)
A new method to evaluate the performance of sealants, used in rigid pavement joints, was developed. A special fixture was designed to transfer cyclic in-line deflection, applied by a testing machine, to cyclic normal and shear deflections on a sealant sandwiched between two-2 x 2 x 2 in. portland cement mortar cubes. The normal and shear deflections were applied simultaneously at a specific ratio controlled by the developed fixture. The new testing method simulates field conditions, where shear deflection is caused by vehicle loads while normal deflection is caused by slabs contraction or expansion due to temperature variation. The developed fixture was used to evaluate the performance of three commercially available one-component sealant types: (A, B, and C), A is a low modulus sealant, B is a self leveling type, while C is a sealant which is used with primer. The effect of joint width on sealant performance was investigated using two joint widths (0.25 in. and 0.75 in.), while the weathering effect was evaluated by exposing specimens to 50 cycles of rapid freezing and thawing prior to testing. / Master of Science
4

Performance Characterization of Cement Treated Sand Base Material of Mozambique

De Vos, Ebenhaezer Roux 03 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2007. / Mozambique is investing heavily in rehabilitating and upgrading the current roadway infrastructure. Investigation by the Mozambican roads authority found that some consulting engineers and contractors were not familiar with Mozambican conditions and materials. The World Bank sponsored a research project to support the roadway infrastructure preservation and maintenance efforts. The thesis work presented forms an integral part of the work conducted by the World Bank project research team. The objective of the thesis is to characterise cement stabilized sand bases in Mozambique under Accelerated Pavement Testing (APT) in terms of stiffness and deflection responses under load trafficking. This work forms the basis for developing guidelines for a mechanistic-empirical design method for Mozambican conditions and materials. Reported findings from initial MMLS3 testing conducted for the World Bank project were used to scope the full-scale research study and provided guidelines for the selection and construction of full scale test sections on natural subgrade. The APT presented encompass full-scale pavement testing including wet trafficking cycles to emulate environmental effects.
5

Scheduling algorithms for routine maintenance of roads in maintenance wards of a gravel road network

Burger, A. F. (Adriaan Francois) 04 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The study reported in this thesis focuses on the development of algorithms that can be used to schedule routine maintenance work in maintenance wards of a gravel road network, This was undertaken as part of the development of the Blading Optimisation Module of the Gravel Management System of the Provincial Government: Western Cape. Two scheduling algorithms were developed and mapped to a pilot object model on the computer. The algorithms and application interface takes account of the constraints and variables of routine maintenance that were identified through interviews with personnel of the five District Municipalities contained in the Western Cape. The algorithms are tested and evaluated using the pilot application. Based on the evaluation of the algorithms conclusions are drawn and recommendations are made. / AFRIKAANSE OPSOMMING: Die studie beskryf in hierdie tesis fokus op die ontwikkeling van algoritmes vir die skedulering van roetine instandhoudingswerk in instandhoudingswyke van 'n gruispadnetwerk. Dit is ondemeem tydens die ontwikkeling van die "Blading Optimisation Module" van die "Gravel Management System" van die Provinsiale Regering: Wes Kaap. Twee algoritmes is ontwikkel en afgebeeld op 'n loods-objekmodel op die rekenaar. Die algoritmes en toepassingskoppelvlak maak voorsiening vir die beperkings en veranderlikes wat geidentifiseer is tydens onderhoude met personeel van die distrikmunisipaliteite in die Wes Kaap. Die algoritmes is getoets en geevalueer met behulp van die loodstoepassing. Gevolgtrekkings en aanbevelings word gemaak op grond van die resultate van die evaluasie van die algoritmes.
6

Development of Data Analytics and Modeling Tools for Civil Infrastructure Condition Monitoring Applications

Jang, Jinwoo January 2016 (has links)
This dissertation focuses on the development of data analytics approaches to two distinct important condition monitoring applications in civil infrastructure: structural health monitoring and road surface monitoring. In the first part, measured vibration responses of a major long-span bridge are used to identify its modal properties. Variations in natural frequencies over a daily cycle have been observed with measured data, which are probably due to environmental effects such as temperature and traffic. With a focus on understanding the relationships between natural frequencies and temperatures, a controlled simulation-based study is conducted with the use of a full-scale finite element (FE) model and four regression models. In addition to the temperature effect study, the identified modal properties and the FE model are used to explore both deterministic and probabilistic model updating approaches. In the deterministic approach (sensitivity-based model updating), the regularization technique is applied to deal with a trade-off between natural frequency and mode shape agreements. Specific nonlinear constraints on mode shape agreements are suggested here. Their capabilities to adjust mode shape agreements are validated with the FE model. To the best of the author's knowledge, the sensitivity-based clustering technique, which enables one to determine efficient updating parameters based on a sensitivity analysis, has not previously been applied to any civil structure. Therefore, this technique is adapted and applied to a full-scale bridge model for the first time to highlight its capability and robustness to select physically meaningful updating parameters based on the sensitivity of natural frequencies with respect to both mass and stiffness-related physical parameters. Efficient and physically meaningful updating parameters are determined by the sensitivity-based clustering technique, resulting in an updated model that has a better agreement with measured data sets. When it comes to the probabilistic approach, the application of Bayesian model updating to large-scale civil structures based on real data is very rare and challenging due to the high level of uncertainties associated with the complexity of a large-scale model and variations in natural frequencies and mode shapes identified from real measured data. In this dissertation, the full-scale FE model is updated via the Bayesian model updating framework in an effort to explore the applicability of Bayesian model updating to a more complex and realistic problem. Uncertainties of updating parameters, uncertainty reductions due to information provided by data sets, and uncertainty propagations to modal properties of the FE model are estimated based on generated posterior samples. In the second part of this dissertation, a new innovative framework is developed to collect pavement distress data via multiple vehicles. Vehicle vibration responses are used to detect isolated pavement distress and rough road surfaces. GPS positioning data are used to localize identified road conditions. A real-time local data logging algorithm is developed to increase the efficiency of data logging in each vehicle client. Supervised machine learning algorithms are implemented to classify measured dynamic responses into three categories. Since data are collected from multiple vehicles, the trajectory clustering algorithm is introduced to integrate various trajectories to provide a compact format of information about road surface conditions. The suggested framework is tested and evaluated in real road networks.
7

An economic analysis of pavement damage caused by studded tires in Oregon

Gray, Judith Ann 02 July 1997 (has links)
This report frames the debate over studded tires in terms of economic principles of marginal cost pricing and efficient resource allocation. In the absence of a user tax, the pavement damage caused by studded tires results in inefficient pricing because social costs associated with the damage are excluded from the price paid by consumers. This leads to over use of studded tires. No attempt was made to quantify the safety effects of studded tire use. A review of research literature was provided to qualitatively support the premise that there is no social benefit from studded tires in Oregon. Quantitative cost analysis was limited to pavement rutting on the state highway system that is sufficient to reduce the useful life of the pavement. The cost estimation was conducted in two stages: first, the wear rates for asphalt and Portland cement concrete (PCC) pavement surfaces were estimated, expressed as inches of rut depth per 100,000 studded tire passes. Linear regression analysis was conducted using rut depth, traffic, and studded tire data from a sample of Oregon highways. A range of wear rates was estimated, reflecting the numerous factors that influence rutting susceptibility of pavements. The mid-points of wear rates for asphalt and PCC were 0.0386" and 0.0093", respectively. Second, the wear rate estimates were used to approximate rutting for the state highway system and to predict resurfacing expenses attributable to studded tire traffic. The results indicate that the cost of studded tire damage on Oregon state highways in 1995 was approximately $10 million. This averages to $8 per tire per year. The implications of the cost are then discussed in terms of the allocation effects of underpricing due to an untaxed externality. The external costs pavement damage caused by studded tires result in inefficient pricing because external costs associated with the damage are excluded from the price paid by consumers. This leads to excess use of studded tires. A studded tires tax sufficient to cover attributable maintenance costs would be in the neighborhood of 30% of the purchase price and would result in a sharp decline in the quantity of studded tires in use. / Graduation date: 1998

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