Engineering Commons^™

Hydraulic And Mineralogical Characterization Of Organoclay Before And After Reaction With Non-Aqueous Phase Liquid (Napl), Mostafa Afzalian

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Sediment capping—a method used to stabilize and remediate contaminated subaqueous sediment in lakes or river shores by covering the contaminant with multiple layered materials— is a more effective, economic, and durable in situ treatment compared to ex situ methods such as dredging. The caps are typically composed of porous geomaterials such as gravels, sands, Reactive Core Mat (RCM), including reactive soils (e.g., organoclay) and geosynthetics (e.g., geotextiles). The designed caps are regarded as water-permeable so as not to disturb the sediment; however, the caps become unsaturated state because of trapped gas generated from the decomposition of organic matter. Most of …

Concentration And Treatment Of Odors Generated By Landfills, Gabriel Cohen

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Landfills produce hydrogen sulfide (H₂S), an odorous compound that can be a nuisance and danger to public. Biological treatment, in particular bio-trickling filters, is a method for controlling H₂S emissions but startup costs can be costly. The goal of this study is to provide a low-cost method for improving environmental air quality in Nebraska through an odor control device. This study determined that the Loup Central Landfill located near Elba, NE would be an adequate site for the testing and implementation of the odor control device. The off-gas of the Loup Central Landfill was tested for …

Quantitative Assessment Of Alkali-Silica Reaction In Small And Large-Scale Concrete Specimens Utilizing Nonlinear Acoustic Techniques, Clayton Malone

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Nonlinear resonance techniques have been shown to be sensitive to microcracking in materials, including alkali-silica reaction (ASR) damage in concrete. However, application of nonlinear resonance tests have been limited due to the difficulty of application to large-scale field structures and the inability to quantitatively relate material nonlinearity with damage development. In this study, the development of ASR in concrete prisms and large concrete beam specimens of varying aggregate types and specimen sizes was monitored using linear and nonlinear resonance techniques.

For the concrete prisms, although the linear resonance frequency test could detect initiation and development of ASR damage in specimens …

Biofiltration Of Volatile Organic Compounds Emitted At Ethanol Plants, Mitham Al-Faliti

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Ethanol is a major biofuel source of energy in the U.S. Ethanol production produces several harmful emissions from both fermentation tanks and dryers. CO₂ scrubbers control the emissions from the fermentation tanks, while the emissions from the dryers are controller by regenerative thermal oxidizers. These methods are expensive to operate. A potential alternative is bio-trickling filters. Bio-trickling filters are an inexpensive and environmentally friendly alternative. For this study, two parallel bio-trickling filters were operated one at 25°C called the mesophilic bio-trickling filter and one at 60°C called the thermophilic bio-trickling filter. The mesophilic bio-trickling filter simulates emissions from fermentation …

Development Of A Mash Test Level 4 Open Concrete Bridge Rail, Jacob Delone

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

An open concrete bridge rail was designed and developed according to safety performance guidelines in the American Association of State Highway Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH) for Test Level 4 (TL-4). Systems designed and developed under previous guidance were studied, and their geometric information and full-scale crash testing performance was studied to establish the geometry of the new bridge rail. Yield-Line Theory and the AASHTO Post and Beam design methods were studied, and a modified version of the AASHTO Post and Beam method was utilized to determine the capacity of the new open concrete bridge rail. …

Development Of An Improved Arterial Roadway Performance Reliability Methodology, Ernest Tufuor

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

The need for reliable performance measures of urban arterial roadways is increasing because of the rise in traffic congestion and the high value of travel time. Consequently, travel time reliability (TTR), which combines components of measures of central tendency and measures of dispersion of travel times, has recently received considerable research interest.

The basis of all TTR metrics is the travel time distribution (TTD). Estimating and forecasting arterial TTDs for TTR analysis is the focus of this dissertation. This dissertation proposes a new TTR methodology that is a marked improvement on recent TTR estimation and forecasting methodologies including the current …

Optimum Mixing Design Of Xanthan And Gellan Treated Soils For Slope Stabilization For Weathered Shales And Glacial Tills In Nebraska, Layal Bitar

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Verdigre located in North Eastern Nebraska experienced slope failures. The geological formations of theses slopes largely consist of several layers of weathered shales and glacial tills. It is believed that the weathering process reduced the shear strength of the soils leading to slope failures.

In this study, strength characteristics of Xanthan and Gellan gums treated soil specimens compacted at the optimum moisture content for field application were investigated so that the biopolymer treated soils may be properly used to stabilize the slopes. The untreated and treated samples were subjected to a wet-freeze(-6^oF)-thaw(167^oF)-dry weathering process up to …

Nitrate And Herbicides Removal From Groundwater Using Immobilized Algae, Sara Mollamohammada

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

To improve crop yield and control broadleaf weeds, many farmers apply nitrate-based fertilizers and chemical herbicides to their fields. Excessive use of these chemicals can cause contamination in waterbodies and impact on the public health. The physical and chemical methods have been suggested to remove these herbicides are usually costly. In this study, the capability of immobilized algal beads in removing nitrate and several herbicides of environmental concern from synthetic and actual groundwater and surface water was evaluated.

The experiments were performed in batch, sequencing batch and continuous flow modes and the effect of different operational conditions (light intensity, cultivation …

Riveted Steel Railway Bridge Health Monitoring And Damage Detection, Ahmed Rageh

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Visual inspection is often used to assess the condition of railway bridges at discrete points in time, an approach that can be subjective and possibly unsafe. Alternatively, certain bridges have their condition assessed via the installation of a large number of sensors. These sensors can be costly to place, power and maintain. Therefore, reducing their numbers and maximizing the extracted information is of utmost importance. In addition, evaluating bridge condition from measured response can be quite challenging due to loading and environmental variations, especially when a limited number of sensors are used.

The focus of this research is to develop …

Reliability-Calibrated Ann-Based Load And Resistance Factor Load Rating For Steel Girder Bridges, Francisco Garcia

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

This research aimed to develop a supplemental ANN-based tool to support the Nebraska Department of Transportation (NDOT) in optimizing bridge management investments when choosing between refined modeling, field testing, retrofitting, or bridge replacement. ANNs require an initial investment to collect data and train a network, but offer future benefits of speed and accessibility to engineers utilizing the trained ANN in the future. As the population of rural bridges in the Midwest approaching the end of their design service lives increases, Departments of Transportation are under mounting pressure to balance safety of the traveling public with fiscal constraints. While it is …

Eliminating Rebar Splicing In Transverse Joints Of Precast Full Depth Bridge Deck Panels, David Gee

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

This study looks at the removal of longitudinal rebar splicing when sufficient longitudinal post-tensioning is provided for full-depth precast deck panels for simply supported bridges. Full-depth precast prestressed concrete deck panels are high quality plant produced pretensioned panels. They are often post-tensioned at the site to provide an average net compression in the joint of at least 250 psi due to effective prestress. This is to ensure adequate transfer of load as truck wheels pass over the joint. This net compression on the transverse joint is not explicitly clear by the AASHTO LRFD Bridge Design Specifications. Based on this section, …