Civil & Environmental Engineering

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    NON DESTRUCTIVE EVALUATION OF CHLORIDE IN CONCRETE
    (2011) Bozorgi Fashand, Nafiseh; Amde, Amde M; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Bridge decks in the cold climate region of the country, which have snow part of the year, are exposed to deicer salt in order to overcome the public demand for safe pavements. The chloride content in the salt can penetrate into the concrete through hairline cracks or diffusion in the concrete. This can establish galvanic corrosion microcells, and ultimately damage the concrete and reduce the life performance of the structure through expansive forces created by corroded steel. The issue of chloride penetrating into concrete has been under study and research for a long time. There is a critical need in civil engineering for methods that can nondestructively measure the condition of existing reinforced concrete structures. The focus of this thesis is on a nondestructive prompt gamma neutron activation (PGNA) chloride detector. This technique is a specialized use of prompt gamma/neutron activation, a spectroscopic technique for elemental analysis of materials. The elements of PGNA are identified by characteristic gamma rays emitted from the target material while it is being bombarded with neutrons. The objective of this research is to design a test program for determining the calibration factor, which relates the detected chloride gamma ray counts to the actual chloride concentration in the concrete, and its uncertainties through the use of cast concrete samples with known chloride contents.
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    PROJECT MANAGEMENT MATURITY IN THE CONSTRUCTION INDUSTRY OF DEVELOPING COUNTRIES (THE CASE OF ETHIOPIAN CONTRACTORS)
    (2011) Yimam, Abadir Hassen; Skibniewski, Miroslaw J; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This research has studied the maturity of PM in the construction industry of developing countries; in the course, the research has also identified two major gaps in the existing maturity models and, proposed a PM maturity model to address the gaps and adapt it to the developing countries context. Using the model, maturity assessment of contractors in Ethiopia is undertaken and, low level of PM maturity (Informal practice of the basic processes) is found. Further, the research found ISO certified contractors‟ PM maturity to be higher than those which are not. Similarly, the PM maturity of contractors which took part in Capacity Building Program is found to be higher than those which did not take part .Likewise, Road contractors PM maturity is found to be higher than Building contractors. Moreover, the research found higher maturity level for material, procurement, cost, financial, time, and human resource management. Risk and safety management are found to be the least matured PM areas.
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    The Hydrologic Design of Green Roofs
    (2011) Ahmadian, Soudeh; McCuen, Richard H.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Green roofs are increasingly being used as part of primary urban strategies to improve stormwater management and reduce energy costs. Different methods for green roof design are based on different assumptions and parameters. However, the input parameters are uncertain, which influences design accuracy. A mathematical model was developed to simulate the water movement across and through a green roof. This model was used to assess the sensitivity of the hydrological response of a green roof to roof and rainfall characteristics. Peak discharge rates and depths of runoff mainly depend on the rainfall characteristics. Green roofs can significantly reduce both the peak discharge rates and runoff depths for small storms but they have little effect on large storms. Furthermore, roof characteristics mainly the roof slope is an important design criteria. The model benefits from using the NRCS infiltration equation and curve number, as well as the specific yield of the soil.
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    GUARANTEE DESIGN ON ENERGY PERFORMANCE CONTRACTS UNDER UNCERTAINTY
    (2011) Deng, Qianli; Cui, Qingbin; Jiang, Xianglin; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Due to the growing concerns with climate change and energy supply, Energy Performance Contracting (EPC), which uses the guaranteed future utility savings to repay the initial renovation investments, becomes increasingly popular. However, most Energy Service Companies (ESCOs) set the savings guarantee roughly based on their previous experience, which leads to inaccurate estimates in practice. This paper has built the stochastic models for the savings risks both from the energy price volatility and the facility performance instability, which follow the Geometric Brownian Motions (GBM) and Ito's lemma. Then, a flexible guarantee designing method for ESCOs is developed to minimize the financial risks and a case study has been conducted to show the application. Finally, suggestions have been made for how ESCOs set the guarantee and the extra profit sharing proportion in contracts based on the existing information. This method will help them appropriately allocate risks with successful contract negotiation.
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    Calibrating Shenandoah Watershed SWAT Model Using A Nonlinear Groundwater Algorithm
    (2011) Wang, Yan; Brubaker, Kaye L.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This study contributes to a project with the Interstate Commission on the Potomac River Basin to build a model of the Potomac watershed using the Soil Water Assessment Tool (SWAT). The 2,937 mi2 Shenandoah watershed represents about 40% of the Potomac Basin by area. The model subdivides the Shenandoah watershed into 28 subwatersheds and 489 hydrologic response units. SWAT's linear-reservoir groundwater algorithm is modified into a new non-linear method. Modeled flows are compared to observations (dating from 1996 to 2006) at 15 USGS stream gages. The model is auto-calibrated using the Parameter Estimation Software (PEST), experimenting with options to improve model performance. The best model results are obtained by applying ordinal weights to the observation groups, decreasing from headwaters to outlet, and pre-calibrating the roughness coefficients using empirical equations. The calibrated model will contribute to understanding hydrological processes and predicting the effects of land use and climate change in the watershed.
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    CATALOG OF MATERIAL PROPERTIES FOR MECHANISTIC-EMPIRICAL PAVEMENT DESIGN
    (2011) Li, Rui; Schwartz, Charles W.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The new pavement design methodology is based on mechanistic-empirical principles that are expected to be used in parallel with and eventually replace the current empirical pavement design procedures. The new mechanistic-empirical pavement design guide (MEPDG) requires greater quantities and quality of input data. Material characterization for the mechanistic-empirical approach, the focus of this thesis, is significantly more fundamental and extensive than in the current empirically-based AASHTO Design Guide. The objective of the thesis is to develop an organized database of material properties for the most common paving materials used in Maryland. A comprehensive material property database in Microsoft Access 2007 has been developed. The database is initially populated with all information received from SHA. It provides complete data management tools for adding and managing future data as well as data display screens for MEPDG. Recommendations for future material testing for Maryland are also provided.
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    A Hybrid Testing Platform for Realistic Characterization of Infrastructure Sensor Technology
    (2011) Mercado, Michael William; Zhang, Yunfeng; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In America's transportation infrastructure, maintaining safe and serviceable bridges is of paramount importance to America's transportation officials. In order to meet the increasing demands for information-based maintenance and repair of civil infrastructures such as highway bridges, an increasing number of structural health monitoring sensors and other non-destructive evaluation (NDE) devices have begun to be implemented on these structures. Before these health monitoring sensors can be implemented on a large scale, they must first be validated and characterized in a controlled environment. This thesis proposes and demonstrates the use of a hybrid testing platform to create a more realistic testbed to evaluate these structural health monitoring sensors for steel bridges. The details of this hybrid testing platform are discussed including the effects of ramp time, stress level, complexity of the virtual model, fatigue, and high temperature testing. The accuracy and practical implementation of this hybrid testing platform are also addressed.
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    ESTIMATING THE FRICTION PERFORMANCE OF HOT MIX ASPHALT PAVEMENTS BASED ON AGGREGATE PROPERTIES AND ROUTE CHARACTERISTICS: ANALYSIS, MODELING AND VALIDATION
    (2011) Awoke, Girum Siraw; Goulias, Dimitrios; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Traffic accidents are one of the major causes of death in the United States. In 2008 alone, more than 37,000 fatalities occurred, accounting for one fatality every thirteen minutes. More than one tenth of fatal accidents occur when pavements are wet and slippery. In wet conditions, a water film is created between the pavement surface and the tire, thereby reducing the amount of available friction. There are several factors that affect the level and type of friction between tires and a wet pavement surface. Some of these factors are microtexture and macrotexture, age of pavement, seasonal and environmental factors, traffic level and composition, individual and blend aggregate properties, binder used in mix, and road location/geometry. The research presented in this dissertation explores the impact of aggregate and mixture properties as well as the role of route characteristics, such as traffic intensity and composition, on the friction performance of Hot Mix Asphalt (HMA) pavements. In the research, various databases for construction, material, pavement management and traffic condition were examined. The data included 5 years of pavement friction readings, construction and material data, and traffic monitoring data. The research included reviewing aggregate quality requirements and friction measurements, and compiling, categorizing and examining the various databases to develop a working dataset/s. In addition, a methodology was developed to isolate and analyze data specific to a given roadway constructed using a known type of aggregate and mix material. The results were then used to estimate pavement friction service life in terms of cumulative traffic loading. Multivariate Regression methods were employed to establish the relationship between Friction Number (FN) and cumulative AADT, for specific aggregates. The research also included establishing relationships between materialproperties/route characteristics and pavement friction, and investigating/developing a model that can be used to predict the friction performance of pavements based on these factors. Partial Least Squares (PLS) Regression, a type of Structural Equation Modeling (SEM) method, was used to extract factors from datasets in order to formulate, test and validate several models out of which the most significant model was selected.
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    A MATHEMATICAL FRAMEWORK FOR OPTIMIZING DISASTER RELIEF LOGISTICS
    (2011) Mohasel Afshar, Abbas; Haghani, Ali; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In today's society that disasters seem to be striking all corners of the globe, the importance of emergency management is undeniable. Much human loss and unnecessary destruction of infrastructure can be avoided with better planning and foresight. When a disaster strikes, various aid organizations often face significant problems of transporting large amounts of many different commodities including food, clothing, medicine, medical supplies, machinery, and personnel from several points of origin to a number of destinations in the disaster areas. The transportation of supplies and relief personnel must be done quickly and efficiently to maximize the survival rate of the affected population. The goal of this research is to develop a comprehensive model that describes the integrated logistics operations in response to natural disasters at the operational level. The proposed mathematical model integrates three main components. First, it controls the flow of several relief commodities from sources through the supply chain until they are delivered to the hands of recipients. Second, it considers a large-scale unconventional vehicle routing problem with mixed pickup and delivery schedules for multiple transportation modes. And third, following FEMA's complex logistics structure, a special facility location problem is considered that involves four layers of temporary facilities at the federal and state levels. Such integrated model provides the opportunity for a centralized operation plan that can effectively eliminate delays and assign the limited resources in a way that is optimal for the entire system. The proposed model is a large-scale mixed integer program. To solve the model, two sets of heuristic algorithms are proposed. For solving the multi-echelon facility location problem, four heuristic approaches are proposed. Also four heuristic algorithms are proposed to solve the general integer vehicle routing problem. Overall, the proposed heuristics could efficiently find optimal or near optimal solution in minutes of CPU time where solving the same problems with a commercial solver needed hours of computation time. Numerical case studies and extensive sensitivity analysis are conducted to evaluate the properties of the model and solution algorithms. The numerical analysis indicated the capabilities of the model to handle large-scale relief operations with adequate details. Solution algorithms were tested for several random generated cases and showed robustness in solution quality as well as computation time.
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    TOOLS TO SUPPORT TRANSPORTATION EMISSIONS REDUCTION EFFORTS: A MULTIFACETED APPROACH
    (2011) Erdogan, Sevgi; Miller-Hooks, Elise D; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The transportation sector is a significant contributor to current global climatic problems, one of the most prominent problems that today's society faces. In this dissertation, three complementary problems are addressed to support emissions reduction efforts by providing tools to help reduce demand for fossil fuels. The first problem addresses alternative fuel vehicle (AFV) fleet operations considering limited infrastructure availability and vehicle characteristics that contribute to emission reduction efforts by: supporting alternative fuel use and reducing carbon-intensive freight activity. A Green Vehicle Routing Problem (G-VRP) is formulated and techniques are proposed for its solution. These techniques will aid organizations with AFV fleets in overcoming difficulties that exist as a result of limited refueling infrastructure and will allow companies considering conversion to a fleet of AFVs to understand the potential impact of their decision on daily operations and costs. The second problem is aimed at supporting SOV commute trip reduction efforts through alternative transportation options. This problem contributes to emission reduction efforts by supporting reduction of carbon-intensive travel activity. Following a descriptive analysis of commuter survey data obtained from the University of Maryland, College Park campus, ordered-response models were developed to investigate the market for vanpooling. The model results show that demand for vanpooling in the role of passenger and driver have differences and the factors affecting these demands are not necessarily the same. Factors considered include: status, willingness-to-pay, distance, residential location, commuting habits, demographics and service characteristics. The third problem focuses on providing essential input data, origin-destination (OD) demand, for analysis of various strategies, to address emission reduction by helping to improve system efficiency and reducing carbon-intensive travel activity. A two-stage subarea OD demand estimation procedure is proposed to construct and update important time-dependent OD demand input for subarea analysis in an effort to overcome the computational limits of Dynamic Traffic Assignment (DTA) methodologies. The proposed method in conjunction with path-based simulation-assignment systems can provide an evolving platform for integrating operational considerations in planning models for effective decision support for agencies that are considering strategies for transportation emissions reduction.