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Articles 901 - 930 of 1043

Full-Text Articles in Civil and Environmental Engineering

Saltwater Intrusion Simulation In Heterogeneous Aquifer Using Lattice Boltzmann Method, Borja Servan Camas Jan 2007

Saltwater Intrusion Simulation In Heterogeneous Aquifer Using Lattice Boltzmann Method, Borja Servan Camas

LSU Master's Theses

This study develops a saltwater intrusion simulation model using a lattice Boltzmann method (LBM) in a two-dimensional coastal confined aquifer. The saltwater intrusion is described by density-dependent groundwater flow and mass transport equations, where a freshwater-saltwater mixing zone is considered. The problem is formulated in terms of hydraulic head instead of pressure, which is recommended in those cases where static pressures dominate to reduce computational cost. The aquifer heterogeneity is explicitly a function of the speed of sound, relaxation parameter and time steps in the LBM. This study explores the equivalent squared sound speed to deal with the spatial-temporal heterogeneity …

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An Experimental Study On Characteristics And Behavior Of Reinforced Soil Foundation, Qiming Chen Jan 2007

An Experimental Study On Characteristics And Behavior Of Reinforced Soil Foundation, Qiming Chen

LSU Doctoral Dissertations

This research study aims at investigating the potential benefits of using the reinforcement to improve the bearing capacity and reduce the settlement of shallow foundations. To implement this objective, a total of one hundred seventeen tests were performed to study the behavior of reinforced soil foundation. The test results showed that the inclusion of reinforcement can significantly improve the soil's bearing capacity and reduce the footing settlement. The geogrids with higher tensile modulus performed better than geogrids with lower tensile modulus. The strain developed along the reinforcement is directly related to the settlement. The test results also showed that the …

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Laboratory Characterization And Numerical Modeling Of Geogrid Reinforced Bases In Flexible Pavements, Munir Darwish Nazzal Jan 2007

Laboratory Characterization And Numerical Modeling Of Geogrid Reinforced Bases In Flexible Pavements, Munir Darwish Nazzal

LSU Doctoral Dissertations

This dissertation documents the results of an extensive research study that was conducted to characterize the behavior of geogrid reinforced base course materials. The research was conducted through an experimental testing and numerical modeling programs. The experimental testing program included performing different laboratory tests to evaluate the effect of various factors on the performance geogrid reinforced base course materials. Finite element models were also developed to investigate the benefits of placing geogrids within the base course layer in a flexible pavement structure. The results of the experimental testing demonstrated that the inclusion of the geogrid reinforcement layer(s) improved the compressive …

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Computer-Aided Weld Inspection By Fuzzy Modeling With Selected Features, Sean Najm Ghazavi Jan 2007

Computer-Aided Weld Inspection By Fuzzy Modeling With Selected Features, Sean Najm Ghazavi

LSU Master's Theses

This thesis develops a computer-aided weld inspection methodology based on fuzzy modeling with selected features. The proposed methodology employs several filter feature selection methods for selecting input variables and then builds fuzzy models with the selected features. Our fuzzy modeling method is based on a fuzzy c-means (FCM) variant for the generation of fuzzy terms sets. The implemented FCM variant differs from the original FCM method in two aspects: (1) the two end terms take the maximum and minimum domain values as their centers, and (2) all fuzzy terms are forced to be convex. The optimal number of terms and …

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Evaluation Of Consolidation Parameters Of Cohesive Soils Using Pcpt Method, Rohit Raj Pant Jan 2007

Evaluation Of Consolidation Parameters Of Cohesive Soils Using Pcpt Method, Rohit Raj Pant

LSU Master's Theses

The piezocone penetration test (PCPT) has emerged as most widely used in situ method for obtaining soil profile as well as physical properties. The PCPT method provides three independent and nearby continuous measurements with the depth; they are: tip stress (qc), sleeve friction (fs) and pore pressure (u1, u2, or u3). These measurements have been successfully used to correlate various soil properties such as undrained shear strength, unit weight and consolidation parameters. This study presents the evaluation of the PCPT interpretation methods for their capability to reasonably estimate the consolidation parameters namely constrained modulus, overconsolidation ratio and vertical coefficient of …

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Study Of Half-Order Bod Reactions, Nicole Plauche Lirette Jan 2007

Study Of Half-Order Bod Reactions, Nicole Plauche Lirette

LSU Master's Theses

Appropriate modeling of Biochemical Oxygen Demand, BOD, is an important part of understanding the character of a wastewater. Much necessary information is gleaned and extracted from the kinetic equation chosen for modeling, especially when a BOD model is included in a dissolved oxygen model. Some information includes the ultimate level of BOD exerted, the rate the BOD demand for dissolved oxygen is exerted, and the critical time at which the minimum level of dissolved oxygen occurs. Although widely used, the first-order kinetic BOD model is not suited for all situations. In some instances, as is the case with constituents found …

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Wind Loads For Petrochemical Structures, Samuel Amoroso Jan 2007

Wind Loads For Petrochemical Structures, Samuel Amoroso

LSU Doctoral Dissertations

Techniques currently available to practicing engineers for estimating wind loads for petrochemical structures have little theoretical or experimental basis. This dissertation research is an effort to expand the understanding of wind effects on petrochemical and other, similar structures. Petrochemical structures introduce geometric scales into wind tunnel model simulations below what are common for enclosed structures. Wind tunnel experiments were performed to help determine whether this will introduce problems in achieving dynamic similarity between models and prototypes. The experiments did not reveal any clear indication that petrochemical structures cannot be modeled in wind tunnels at scales similar to those used for …

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Locally Derived Nonpoint Loading Estimates For The Boeuf River/Bayou Lafourche Watershed, Emerald Purser Roider Jan 2007

Locally Derived Nonpoint Loading Estimates For The Boeuf River/Bayou Lafourche Watershed, Emerald Purser Roider

LSU Doctoral Dissertations

There is currently a great demand for data and models that can be used to quantify nonpoint source pollutant loads from different land-use types. The Louisiana Department of Environmental Quality (LDEQ) is in the process of implementing management programs for impacted water bodies based on the Total Maximum Daily Load (TMDL) of a pollutant. Pollutants of concern include total suspended solids (TSS), nitrogen, and phosphorus. One of the key parameters in determining the TMDL of a water body is the nonpoint source pollutant load from different land-use types. To date, such load estimates in Louisiana are lacking. The primary objective …

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Flow And Distribution Of Water In Fractional Wettability Unsaturated Porous Media, Zaydoun Turkey Abusalem Jan 2007

Flow And Distribution Of Water In Fractional Wettability Unsaturated Porous Media, Zaydoun Turkey Abusalem

LSU Doctoral Dissertations

In recent years, interest in fluid flow and transport in the unsaturated zone has gained more attention, due to growing concerns that the quality of the subsurface environment is adversely affected by agricultural, industrial, and municipal activities. The wettability properties (e.g., water repellency) of soil in the unsaturated zone play an important role in determining fluid movement and ultimate distributions. A number of studies have shown that preferential flow and spatially variable moisture content is likely to occur in water repellant soils. Development of appropriate constitutive relations for numerical modeling becomes even more difficult in systems that contain water repellant …

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Readjustment Of A Regional Geodetic Leveling Network To Account For Temporally And Spatially Variable Vertical Displacement Of Benchmarks, Kurt Shinkle Jan 2007

Readjustment Of A Regional Geodetic Leveling Network To Account For Temporally And Spatially Variable Vertical Displacement Of Benchmarks, Kurt Shinkle

LSU Doctoral Dissertations

This dissertation describes and analyzes the temporally and spatially non-linear nature of the vertical displacement of 1st order geodetic benchmarks in the lower Mississippi Valley and northern Gulf of Mexico coastal region. The least-squares method of adjusting redundant surveying observations is implemented to compute the most likely value of the most recent rates of displacement at node benchmarks within the network, along with estimates of the uncertainty of those values. Using that result, a modification of the standard method of adjusting geodetic leveling networks is developed and demonstrated to compute new elevations for the node benchmarks which accounts for both …

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A Plasticity-Damage Model For Plain Concrete, Umit Cicekli Jan 2006

A Plasticity-Damage Model For Plain Concrete, Umit Cicekli

LSU Doctoral Dissertations

A plastic-damage model for plain concrete is developed in this work. The model uses two different yield criteria: one for plasticity and one for damage. In order to account both for compression and tension loadings, the damage criterion is divided into two parts: one for compression and a second for tension. The superscripts (+) and (-) in this work are used to represent tension and compression cases, respectively. The total stress is decomposed into tension and compressions components. The total strain is decomposed into elastic and plastic parts. The strain equivalence concept is used such that the strains in the …

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Structural Performance Of Approach Slab And Its Effect On Vehicle Induced Bridge Dynamic Response, Xiaomin Shi Jan 2006

Structural Performance Of Approach Slab And Its Effect On Vehicle Induced Bridge Dynamic Response, Xiaomin Shi

LSU Doctoral Dissertations

Differential settlement often occurs between the bridge abutment and the embankment soil. It causes the approach slab to lose its contacts and supports from the soil and the slab will bend in a concave manner. Meanwhile, loads on the slab will also redistribute to the slab ends, which may result in faulting (or "bump") at the slab ends. Once a bump forms, repeating traffic vehicles can deteriorate the expansion joint in turn. In this case, the vehicle receives an initial disturbance before it reaches the bridge. This excitation introduces an extra impact load on the bridge and affects its dynamic …

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Evaluation Of Media Influence And Practical Applications For The Use Of Static Low Density Media Filters In Domestic Wastewater Treatment, Steven Marty Bellelo Jan 2006

Evaluation Of Media Influence And Practical Applications For The Use Of Static Low Density Media Filters In Domestic Wastewater Treatment, Steven Marty Bellelo

LSU Master's Theses

Static Low Density Media filters have been used over the past two decades for nitrification and solids removal in high-density recirculating aquaculture systems. The SLDM filters are submerged biofilters which contain a plastic media with a density less than that of water. The media beds remain packed, or static, during operation except for periodic expansion of the bead bed during a backwash. More recently SLDM filters have been evaluated for secondary clarification of domestic wastewater where concurrent biological treatment and particulate removal occur within one unit. Recirculation is accomplished using airlifts which provide external aeration coupled with multiple pass removal …

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Frictional Interaction Properties Between Geomaterials And Geosynthetics, Julian Javier Coronel Jan 2006

Frictional Interaction Properties Between Geomaterials And Geosynthetics, Julian Javier Coronel

LSU Master's Theses

Soil reinforcement interaction is a primary issue for designing reinforced soil structures. The soil to geosynthetic interaction parameters are influenced by a) Interaction mechanism between geomaterials and geosynthetics (pull-out or direct shear), b) Physical and mechanical properties of geomaterials (density, grain shape and size, grain size distribution, water content, and plasticity of clayey soils), and c) Mechanical properties (tensile peak strength), shape and geometry of geosynthetics. The soil to geogrid interface friction parameters (interface friction angle "δ" and adhesion "ca") for different plasticity indexes, moisture contents, and dry densities were investigated. For this purposes, a large scale direct …

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Partial Continuity In Prestressed Concrete Girder Bridges With Jointless Decks, Ram Naren Mothe Jan 2006

Partial Continuity In Prestressed Concrete Girder Bridges With Jointless Decks, Ram Naren Mothe

LSU Master's Theses

Jointless multi-simple span deck-girder (composite concrete deck with steel or prestressed concrete girders) bridge construction has been accepted as an alternative to jointed construction. Bridge deck joints add to the construction and maintenance costs of the bridge. Bridge support bearing pads deterioration is a common problem in bridges with jointed bridge decks. One of the methods used for building a jointless bridge is to provide a link slab that connects the decks of the adjacent spans. This study mainly focuses on the behavior of the link slab and its effect on the behavior of the bridge system as a whole. …

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Refurbishment Of Louisiana State University Calibration Chamber, Ardita Dushi Jan 2006

Refurbishment Of Louisiana State University Calibration Chamber, Ardita Dushi

LSU Master's Theses

This thesis focuses on the refurbishment of Louisiana State University calibration chamber. The testing equipments were checked and connected together to complete the calibration chamber system. The data acquisition system was upgraded to National Instruments (NI) SCXI system. Therefore, a compatible computer program language in LabVIEW was developed. LabVIEW is a programming language developed by NI that reads the data from the instruments, displays the data in graphical form, calculates the desired parameters, commands the transducer to apply the required pressure to the specimen, and saves the data at the desired frequency. The Anisotropic Modified Cam Clay Model (AMCCM) following …

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Development And Application Of Methods For Evaluation Of Hurricane Shelters, James P. Gregg Jan 2006

Development And Application Of Methods For Evaluation Of Hurricane Shelters, James P. Gregg

LSU Master's Theses

With the population of hurricane prone regions increasing, it has become more difficult to evacuate entire communities, increasing the need for hurricane shelters in coastal areas. Community officials generally use American Red Cross Standard ARC 4496 to evaluate the suitability of buildings for use as shelters.. ARC 4496 uses a least-risk process that evaluates many building and site characteristics. However, it does not address characteristics of the approaching storm and does not provide insight to the expected hazards and performance of the facility under different hurricane conditions. A new method for evaluating facilities for use as hurricane shelters is proposed. …

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Effect Of Speed Limit Increase On Crash Rate On Rural Two-Lane Highways In Louisiana, Athira Swarna Jayadevan Jan 2006

Effect Of Speed Limit Increase On Crash Rate On Rural Two-Lane Highways In Louisiana, Athira Swarna Jayadevan

LSU Master's Theses

Though the rural two lane roads are the low volume-less traveled roads, the majority of the crashes occur on these roads and the high speed of motor vehicles on these roads is suspected to be one of the main causes for this. This study focused on the development of a methodology to study the impact of a speed limit increase on the crash rate on the rural two lane roads in Louisiana. The Louisiana crash database obtained from the Louisiana Department of Transportation (LADOTD) was used to carry out the analysis. The analysis consisted of the comparison of crash rates …

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A Comparative Analysis Of Hurricane Evacuation Traffic Conditions Using Static And Dynamic Traffic Assignments, Santosh Kumar Andem Jan 2006

A Comparative Analysis Of Hurricane Evacuation Traffic Conditions Using Static And Dynamic Traffic Assignments, Santosh Kumar Andem

LSU Master's Theses

This study compares link flows of evacuation traffic using Static Traffic Assignment (STA) with those obtained from Dynamic Traffic Assignment (DTA) and observed traffic counts. The analysis is conducted on a sample of households from South Carolina who evacuated in the face of hurricane Floyd in 1999. The results indicate that traditional static models have the potential to significantly underestimate congestion levels in the network, and DTA models account for nonuniform demand and traffic dynamics in hurricane evacuation much more realistically. From observed traffic counts, traffic volumes vary considerably during an evacuation and the DTA flow estimates generally reproduced these …

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Calibration Of Flexural Design Of Concrete Members Reinforced With Frp Bars, Sujata Nandkumar Kulkarni Jan 2006

Calibration Of Flexural Design Of Concrete Members Reinforced With Frp Bars, Sujata Nandkumar Kulkarni

LSU Master's Theses

Fiber Reinforced Polymer (FRP) composites have been increasingly accepted in the construction industry as a promising substitute for steel. Bridge deck deterioration is one of the most common deficiencies in a bridge system. The use of FRP bars as reinforcement for concrete bridge decks provides a potential for increased service life, economic, and environmental benefits. This research presents the development of resistance models for concrete members (beams and slabs) reinforced with FRP bars (FRP-RC), for carrying out reliability analysis. The scope of this model is limited to the flexural behavior only; i.e. the failures are not shear failure and debonding. …

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Fundamental Characterization Of Louisiana Hma Mixtures For The 2002 Mechanistic-Empirical Design Guide, Sandeep Obulareddy Jan 2006

Fundamental Characterization Of Louisiana Hma Mixtures For The 2002 Mechanistic-Empirical Design Guide, Sandeep Obulareddy

LSU Master's Theses

The main objective of this research was to develop a catalog for dynamic modulus values inputs in the 2002 Empirical and Mechanistic Guide for Design of New and Rehabilitated Pavement Structures (2002 M-E Design Guide) and to examine the permanent deformation characteristics of Louisiana hot mix asphalt (HMA) mixtures based on four laboratory tests, namely dynamic modulus |E*|, flow number, flow time and hamburg wheel tracker test. In addition, the sensitivity of rut prediction from the 2002 M-E Design Guide, using the dynamic modulus |E*| test results was evaluated and the Witczak and Hirsch models were also evaluated, for the …

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Acoustic Emission Monitoring And Quantitative Evaluation Of Damage In Reinforced Concrete Members And Bridges, Archana Nair Jan 2006

Acoustic Emission Monitoring And Quantitative Evaluation Of Damage In Reinforced Concrete Members And Bridges, Archana Nair

LSU Master's Theses

A considerable proportion of highway bridges in the US, are made of reinforced concrete. The vulnerability of these structures during their long service life is a cause of major concern for civil engineers. Since there is a need to detect and recuperate the condition of the bridge structures numerous innovative non-destructive testing (NDT) techniques have come into the forefront. Of the many available technologies, acoustic emission (AE) monitoring has been the most popular non-destructive technique used on highway bridges. Acoustic emission is a passive monitoring technique. Thus, it can be appropriately used for field bridge monitoring applications. Usually AE monitoring …

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Design And Evaluation Of Automated, Continuous Culture Techniques For Brachionus Rotundiformis, Zhengzhong Zhang Jan 2006

Design And Evaluation Of Automated, Continuous Culture Techniques For Brachionus Rotundiformis, Zhengzhong Zhang

LSU Doctoral Dissertations

A 40-L recirculating rotifer turbidostat (RRT) pilot system consisting of a rotifer reactor, biofilter, foam fractionator, feed container, harvester, and two air-lift pumps was designed to produce B. rotundiformis, a small (S-type) rotifer, that is increasingly demanded for production of small-gape marine finfish larvae. The system’s automatic monitoring (turbidity, pH, conductivity and temperature) and controlling (turbidity, pH, feeding and harvesting) were performed by a Rugid™ computer. A 4 (temperature) x 3 (salinity) study indicated that a 30oC/15 ppt treatment is the most favorable to the growth of B. rotundiformis. Under these conditions, the effect of harvest rate on rotifer system …

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Development Of A Mix Design Methodology For Asphalt Mixtures With Analytically Formulated Aggregate Structures, Khalid Salim Alshamsi Jan 2006

Development Of A Mix Design Methodology For Asphalt Mixtures With Analytically Formulated Aggregate Structures, Khalid Salim Alshamsi

LSU Doctoral Dissertations

This research documents an extensive study on the design and characterization of asphalt mixtures for use as road pavement material. Several aspects of asphalt mixtures were addressed using the state of the art laboratory test equipment and technical literature from different information sources. The research was divided into two phases. Phase one included the design and detailed analysis of compaction and performance characteristics of asphalt concrete mixtures with aggregate structures that were designed using an analytical method of aggregate blending. Three aggregate types were considered in this study: limestone, sandstone, and granite. All the aggregates were crushed aggregates. Three different …

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Use Of Polyhydroxyalkanoates For Denitrification In Recirculating Aquaculture Systems, Maria Teresa Gutierrez-Wing Jan 2006

Use Of Polyhydroxyalkanoates For Denitrification In Recirculating Aquaculture Systems, Maria Teresa Gutierrez-Wing

LSU Doctoral Dissertations

Increasing demand of aquacultural products is driving the industry toward more intensive culture practices. Aquacultural operations are constrained by limitations on the availability high quality waters and regulatory pressures on the discharges. Recirculating systems can address these issues by reducing the amount of water required in the operation. Closed systems are especially suited where biosecurity is important. In closed systems, nitrate accumulates, limiting the time the water can be reused. In marine inland systems, water reuse reduces the cost of salt for make up water. To increase the water reuse time, some form of nitrate removal process must be incorporated …

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Influence Of Typha Latifolia And Phragmites Communis Root Matter On Degredation Of Aged 1,2,3,4-Tetrachlorobenzene In Bayou Sediments, Elaiza Maria Alvarez Jan 2006

Influence Of Typha Latifolia And Phragmites Communis Root Matter On Degredation Of Aged 1,2,3,4-Tetrachlorobenzene In Bayou Sediments, Elaiza Maria Alvarez

LSU Master's Theses

The purpose of this study was to investigate the effects of Typha latifolia and Phragmites communis root matter in degradation of sediments contaminated with aged 1,2,3,4- Tetrachlorobenzene (1,2,3,4-TeCB). In the present study, complete reductive dechlorination of 1,2,3,4-TeCB was observed in root matter systems, contrasting sediment with no roots present. Microcosms amended with Phragmites communis roots achieved the greatest first-order reaction rate constant over a 4-week period (0.113 d-1, half-life time of 6.13 days). Typha latifolia roots also played an important role in reductive dehalogenation of 1,2,3,4-TeCB, although the first-order reaction rate constant observed within the same period of …

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A Probabilistic Approach For Modeling And Real-Time Filtering Of Freeway Detector Data, Shourie Kondagari Jan 2006

A Probabilistic Approach For Modeling And Real-Time Filtering Of Freeway Detector Data, Shourie Kondagari

LSU Master's Theses

Traffic surveillance systems are a key component for providing information on traffic conditions and supporting traffic management functions. A large amount of data is currently collected from inductive loop detector systems in the form of three macroscopic traffic parameters (speed, volume and occupancy). Such information is vital to the successful implementation of transportation data warehouses and decision support systems. The quality of data is, however, affected by erroneous observations that result from malfunctioning or mis-calibration of detectors. The open literature shows that little effort has been made to establish procedures for screening traffic observations in real-time. This study presents a …

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An Adaptive Multi-Scale Computational Method For Modeling Nonlinear Deformation In Nanoscale Materials, Wenming Wang Jan 2006

An Adaptive Multi-Scale Computational Method For Modeling Nonlinear Deformation In Nanoscale Materials, Wenming Wang

LSU Doctoral Dissertations

In this dissertation a coupled multi-scale computational model for simulating nonlinear deformation processes in crystalline metals at finite temperatures is developed. The computational model uses the finite element method to model the coarse scale response of the material. The constitutive response in the finite element will be modeled through interatomic potentials acting on the underlying homogeneous crystal lattice that characterizes its nanostructure. An adaptive remeshing technique is proposed to automatically delineate regions of severe deformation where homogeneity of the microstructure/deformation is violated. In these regions the finite element will be replaced by a set of deformed atoms which interact with …

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A Nonlocal Model For Coupled Damage-Plasticity Incorporating Gradients Of Internal State Variables At Multiscales, Robert J. Dorgan Jan 2006

A Nonlocal Model For Coupled Damage-Plasticity Incorporating Gradients Of Internal State Variables At Multiscales, Robert J. Dorgan

LSU Doctoral Dissertations

The thermodynamically consistent formulation and the subsequent numerical implementation of a gradient enhanced continuum coupled damage-plasticity model as a constitutive framework to model ill-posed localization problems is presented. By the introduction of "nonlocal," gradient-enhanced measures in the plasticity potential function and yield criterion and in the damage potential function and damage criterion, the proposed model introduces microstructural characteristic material length scales which allows the size of localized zones to be predicted based on material constants, as opposed to local models where the loss of ellipticity causes the localized zones to be mesh dependent.
The gradient model proposed introduces non-linear functions …

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A Stochastic Mesoscopic Cell-Transmission Model For Operational Analysis Of Large-Scale Transportation Networks, Ciprian Danut Alecsandru Jan 2006

A Stochastic Mesoscopic Cell-Transmission Model For Operational Analysis Of Large-Scale Transportation Networks, Ciprian Danut Alecsandru

LSU Doctoral Dissertations

The cell transmission model (CTM), developed by Daganzo in 1994 was not fully exploited as an operations model for analysis of large-scale traffic networks. Because of its macroscopic / mesoscopic features, CTM offers calibration and computational advantages over microscopic models. This study presents a series of enhancements to the original form of CTM. These enhancements show potential to increase the model’s accuracy and realism of traffic flow representation. For example, topological enhancements and modifications to the flow advancing equation are introduced to allow variable cell lengths and non-discrete movements of vehicles between cells. In addition, implementation of lane-changing behavioral logics …

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