Engineering Commons^™

Evaluating Direct Filtration As An Alternative To Conventional Carbon-Based Advanced Treatment For Indirect Potable Reuse, Savannah M. Flemmer

Civil & Environmental Engineering Theses & Dissertations

Hampton Roads Sanitation District (HRSD) is recharging purified wastewater into the Potomac Aquifer via the Sustainable Water Initiative for Tomorrow (SWIFT) project. Conventional SWIFT treatment applies coagulation, flocculation, sedimentation, ozonation, biofiltration, granular activated carbon (GAC) adsorption, and ultraviolet disinfection to secondary effluent to produce water that meets drinking water standards for managed aquifer recharge. HRSD is considering implementing direct filtration as an alternative to conventional treatment for two additional SWIFT facilities. Direct filtration presents an opportunity for significant cost savings by eliminating sedimentation, shortening flocculation detention time, and reducing coagulant usage. Without upstream removal of solids and organics, however, biofilters …

Effectiveness Of Suspended Lead Dampers In Steel Buildings Under Localized Lateral Impact And Vertical Pulsating Load, Herish Abdullah Hussein

Civil & Environmental Engineering Theses & Dissertations

Presented herein is a study of the effectiveness of suspended lead dampers for use in steel buildings under a localized impact load and a vertical pulsating load. A series of lead spheres mounted on a string are suspended inside the building columns or damping panels to absorb the energy of vibration through a collision between the lead dampers and internal surfaces of the members. Experiments are conducted on a three-story steel building model and a cantilever member with suspended lead dampers and subjected to localized impact loading. The cantilever under impact load is analyzed with a partial differential equation of …

Spatiotemporal Variations Of Precipitation And Climate-Resilient Structure Design In Virginia, Xiaomin Yang

Civil & Environmental Engineering Theses & Dissertations

How to consider effects of climate change on the design and management of hydrology related infrastructure is crucial but remains a challenge for sustaining resilient society. To address this challenge, existing hydrologic design procedures may need to be revised and/or redeveloped to take into account the precipitation non-stationarity resulting from climate change. Using the state of Virginia as a testbed and advanced statistical techniques such as nonparametric test, spatial autocorrelation, linear regression, distribution fitting, and spatial interpolation, this dissertation developed an innovative framework to detect the historical spatiotemporal variations of various precipitation characteristics, namely maximum precipitation intensity, precipitation amount, simple …

Rainfall-Runoff Mechanisms And Flood Mitigation In A Coastal Watershed With Numerous Wetlands And Ponds, Homa Jalaeian Taghadomi

Civil & Environmental Engineering Theses & Dissertations

This study analyzed mechanisms of flooding in Blackwater River Watershed, located in coastal Virginia and hydraulically connected with mid-Atlantic Ocean. The analysis was based on the examination and simulation of the rainfall-runoff relationship, and such an analysis is very important for conventional water resource management and dealing with hydrologic extremes (e.g., floods and droughts, as well as ecological and pollution discharges). The rainfall-runoff relationship is a quantitative description of the hydrologic cycle, a dynamic process that can be interactively influenced by various factors, namely climate, topography, soils, land use and land cover, and land management practice.

In the past 60 …

Stability Of Low Crested And Submerged Breakwaters: A Reanalysis And Model Development, Christopher P. Burgess

Civil & Environmental Engineering Theses & Dissertations

Low-crested and submerged structures (LCS) play an integral part in the stabilization of shorelines for recreational purposes, yet there are a plethora of empirical models and gaps in the understanding of their stability and damage progression. The objectives were: i) to evaluate the present formulae, ii) explore variable importance, iii) formulate a stability model, iv) extend the current datasets and v) explore a new model for LCS. The literature points to an increasing understanding of the initiation of damage of LCS and recent exploration of the shear stress-induced erosion (van Rijn, 2019). Assessment of two existing models (Kramer, 2006 and …

The Impacts Of Surface Gravity Waves On Buoyant Plume Dilution, Bruce William Husselbee

Civil & Environmental Engineering Theses & Dissertations

A common practice in coastal areas is to collect, treat and discharge fluids including treated wastewater, stormwater or power plant effluent to areas of lesser impact. The discharge of these fluids, conveyed through pipelines into coastal areas, continues to be an important human health and environmental concern. The fluid discharged from these pipelines is often buoyant which allows for dilution and dispersion into these ambient waters.

Initial dilution, defined as the maximum concentration of a discharged fluid at the maximum rise in height within a buoyant plume, is critical in the consideration of the environmental impacts of a discharge into …

Lateral-Torsional Instability And Biaxial Flexure Of Continuous Gfrp Beams Including Warping And Shear Deformations, Waverly G. Hampton

Civil & Environmental Engineering Theses & Dissertations

This dissertation presents an experimental and theoretical study of the lateral-torsional instability and biaxial flexure of Glass Fiber Reinforced Polymer (GFRP) beams including warping and shear deformation effects. The theoretical analysis is based on three simultaneous differential equations of equilibrium with new terms added to account for shear deformation effects. To solve these equations, algorithms based upon a central finite-difference approach are then developed. The experimental study is conducted on a series of single- and multi-span beams subjected to concentrated loads. The predicted beam behavior agreed well with that observed experimentally. The investigation revealed that the ASCE-LRFD Prestandard for pultruded …

A Rule Based Control Algorithm For On-Ramp Merge With Connected And Automated Vehicles, Ehsan Beheshtitabar

Civil & Environmental Engineering Theses & Dissertations

One of the designs for future highways with the flow of Connected Automated Vehicles (CAVs) cars will be a dedicated lane for the CAVs to form platoons and travel with higher speeds and lower headways. The connectivity will enable the formation of platoons of CAVs traveling beside non-platoon lanes. The advent of connectivity between vehicles and the infrastructure will enable advanced control strategies ̶ improving the performance of the traffic ̶ to be incorporated in the traffic system. The merge area in a multilane highway with CAVs is one of the sections which can be enhanced by the operation of …

Numerical Modeling Of Shoreline Response To Storm Tides And Sea Level Rise, Akash Sahu

Civil & Environmental Engineering Theses & Dissertations

In this study, an integrated hydrodynamic, wave, and sediment transport modeling approach is developed for predicting the spatiotemporal variation of erosion of a sandy shoreline due to storm surge, wave action, tidal variations, and relative sea level rise (RSLR). The study site is located at the northern most portion of the city of Norfolk, Virginia, and it is of importance to the city, both in terms of tourism and for the protection that it provides for upland properties against storms. The region, in general, experiences the highest rate of RSLR on the U.S. East Coast which should result in high …

Parallel Jacobi Transformation Algorithm For Generalized Eigen-Solution With Improved Damage Detection Of Truss/Bridge-Type Structures, Maryam Ehsaei

Civil & Environmental Engineering Theses & Dissertations

Serial Jacobi transformation algorithm for the solution of “standard eigen-problems” is re-visited to facilitate the explanation of the proposed parallel transformation algorithm, for which computational efficiency can be realized in this study through “pattern recognition” for the development and explanation of “explicit formulas” to avoid costly matrix time matrix operations. The proposed parallel Jacobi transformation for the solution of “generalized eigen-problems” has also been incorporated into the “improved damage detection” algorithm.

Computational efficiency and robust behaviors for the entire proposed procedures (eigen-solution, damage detection and damage quantification) can be validated through several academic and real-life numerical examples. Numerical results obtained …

Spatiotemporal Downscaling Rainfall Predictions Of North American Regional Climate Change Assessment Program For Entire Virginia, Zhaoyi Cai

Civil & Environmental Engineering Theses & Dissertations

This thesis developed a statistical downscaling approach, which consists of a series of linear regression equations, to spatiotemporally downscale the rainfall predictions from North American Regional Climate Change Assessment Program (NARCCAP) in accordance with the 15-min observed rainfall data at the rain gauges across the state of Virginia. NARCCAP has generated twelve different region-global climate models (RCM-GCMs) with a temporal resolution of 3 hr and a spatial resolution of 50 km over the entire America. Although it has been downscaled already, such resolutions are still too coarse to represent the rain gauges. This means that the RCM-GCMs’ predictions need to …

Numerical Modeling And Field Investigation Of Nearshore Nonlinear Wave Propagation, Elham Sharifineyestani

Civil & Environmental Engineering Theses & Dissertations

First, a phase-resolving frequency-domain wave model that solves nonlinear wave-wave interactions is improved to account for wave dissipation and modulations over viscoelastic mud layer. Model results show satisfactory agreement with laboratory measurements. The model is then used to investigate the combined effect of mud viscoelasticity and nonlinear wave-wave interactions on surface wave evolution using cnoidal and random wave simulations. In general, qualitative measures such as shape of cnoidal waves or pattern of variation in H_rms of random waves are dictated by direct mud-induced damping which, due to resonance effects, has a substantially different structure over viscoelastic mud compared to …

Adaptive Control Of Base Isolation Systems Using The Transmissibility-Based Semi-Active Controller, Ramin Rabiee

Civil & Environmental Engineering Theses & Dissertations

Base isolation system is one of the most effective seismic protection systems which is widely used to protect buildings of high importance against seismic hazards. However, the performance of these systems might be impaired under long-period earthquake ground motions due to the resonance effect. The main focus of this dissertation is the development of an adaptive semi-active control algorithm to improve the performance of conventional base isolation systems. The proposed control law works based on the transmissibility theory, called the transmissibility-based semi-active (TSA) controller, which can adaptively change the damping of the base-isolation system based on the response of the …

Developing Algorithms To Detect Incidents On Freeways From Loop Detector And Vehicle Re-Identification Data, Biraj Adhikari

Civil & Environmental Engineering Theses & Dissertations

A new approach for testing incident detection algorithms has been developed and is presented in this thesis. Two new algorithms were developed and tested taking California #7, which is the most widely used algorithm to date, and SVM (Support Vector Machine), which is considered one of the best performing classifiers, as the baseline for comparisons. Algorithm #B in this study uses data from Vehicle Re-Identification whereas the other three algorithms (California #7, SVM and Algorithm #A) use data from a double loop detector for detection of an incident. A microscopic traffic simulator is used for modeling three types of incident …

Deep Reinforcement Learning Approach For Lagrangian Control: Improving Freeway Bottleneck Throughput Via Variable Speed Limit, Reza Vatani Nezafat

Civil & Environmental Engineering Theses & Dissertations

Connected vehicles (CVs) will enable new applications to improve traffic flow. The focus of this dissertation is to investigate how reinforcement learning (RL) control for the variable speed limit (VSL) through CVs can be generalized to improve traffic flow at different freeway bottlenecks. Three different bottlenecks are investigated: A sag curve, where the gradient changes from negative to positive values causes a reduction in the roadway capacity and congestion; a lane reduction, where three lanes merge to two lanes and cause congestion, and finally, an on-ramp, where increase in demand on a multilane freeway causes capacity drop. An RL algorithm …

Measuring And Modeling Bare Desert Wind Erosion From Steppe Grassland Of Northern China As Affected By Soil Moisture And Climate, Nicholas Morgan Potter

Civil & Environmental Engineering Theses & Dissertations

Soil erosion by wind has been found to be negatively related to soil water content, as evidenced by that for a given area, such a soil erosion can be much less in a wet than a dry year. However, few studies have examined the functional relationship between wind erosion and soil moisture, primarily due to lack of field measured data. The objectives of this study were to: 1) measure wind erosion in field using a portable wind tunnel devised and made by the author; 2) use the measured data to calibrate/validate a wind erosion model previously developed by the author; …

Variable Speed Limit Control At Sag Curves Through Connected Vehicles: Implications Of Alternative Communications And Sensing Technologies, Reza Vatani Nezafat

Civil & Environmental Engineering Theses & Dissertations

Connected vehicles (CVs) will enable new applications to improve traffic flow. This study’s focus is to investigate how potential implementation of variable speed limit (VSL) through different types of communication and sensing technologies on CVs may improve traffic flow at a sag curve. At sag curves, the gradient changes from negative to positive values which causes a reduction in the roadway capacity and congestion. A VSL algorithm is developed and implemented in a simulation environment for controlling the inflow of vehicles to a sag curve on a freeway to minimize delays and increase throughput. Both vehicle-to-vehicle (V2V) and infrastructure-to-vehicle (I2V) …

Latent Choice Models To Account For Misclassification Errors In Discrete Transportation Data, Lacramioara Elena Balan

Civil & Environmental Engineering Theses & Dissertations

One of the most fundamental tasks when it comes to analyzing data using statistical methods is to understand the relationship between the explanatory variables and the outcome. Misclassification of explanatory variables is a common risk when using statistical modeling techniques. In this dissertation, we define ‘misclassification,’ as a response that is reported or recorded in the wrong category; for example, a variable is registered as a one when it should have the value zero. Misclassification can easily happen in any data; for example, in an interview setting where the respondent misunderstands the question or the interviewer checks the wrong box. …

Techno-Economic And Life Cycle Assessment Of Hydrothermal Processing Of Microalgae For Biofuels And Co-Product Generation, Andrew P. Bessette

Civil & Environmental Engineering Theses & Dissertations

Traditional processing methods of algae to biofuels require dewatering after harvesting of the algae before the lipids can be extracted. This is typically the most energy intensive and therefore the most expensive step. Old Dominion University (ODU) has successfully utilized a flash hydrolysis (a kind of hydrothermal) process where proteins are solubilized into the liquid phase of product and the remainder lipid-rich, low nitrogen product is separated into a solid phase. The solid phase (lipid-rich) is then an ideal candidate for biofuel feedstock and the liquid phase, or hydrolysate, can be used for coproducts such as a source of nutrients …

Flexural Behavior And Strength Of Doubly-Reinforced Concrete Beams With Hollow Plastic Spheres, Rutvik R. Patel

Civil & Environmental Engineering Theses & Dissertations

This thesis presents the outcome of an investigation into the experimental and theoretical flexural behavior and strength of doubly-reinforced concrete beams with and without hollow plastic spheres. Tests are conducted on two types of beams having simply supported end conditions. To obtain experimental results, a gradually increasing two-point loading is used up to collapse. The experimental load-deflection and load-strain curves are recorded. Theoretical analysis is based on developing non-linear moment-curvature relationships for cross sections with and without hollow spheres. These moment-curvature relationships are then coupled with three separate numerical methods namely, finite difference method, finite integral method and Newmark’s method …

Simulated Dynamics Of Soil Water And Pore Vapor In A Semi-Arid Sandy Ecosystem, Shohreh Pedram

Civil & Environmental Engineering Theses & Dissertations

Understanding dynamics of soil water content (SWC) and pore air relative humidity (RHpa), as influenced by wetting-drying cycles, is crucial for sustaining fragile ecosystems of desert lands across the world and needed for improving the prediction accuracy of global climate change. However, to date, such an understanding is still incomplete. The objective of this dissertation was to examine such dynamics at a typical desert site within the Horqin Sandy Land, located in Mongolian Plateau of north China. The examination was done by using a HYDRUS-1D computer simulation model and the continuous sensor-based soil water data for two calendar years. HYDRUS-1D …

Investigating Physical Processes Associated With Chesapeake Bay And Changjiang Estuary, Arash Niroomandi

Civil & Environmental Engineering Theses & Dissertations

Coastal and estuaries are landforms that not only have great impacts on large marine ecosystem, but also play a significant role in moderating or aggravating natural hazards and erosion risks that are expected to increase with climate change. This dissertation explores some of the concerns associated with coasts and coastal systems. In the second chapter, a thirty seven year wave hindcast (1979-2015) in Chesapeake Bay using NCEP's Climate Forecast System Reanalysis (CFSR) wind is presented. The long-term significant wave heights are generated by the third-generation nearshore wave model SWAN, which is validated using the wave height measurements at buoy stations …

Efficient Algorithms For Solving Size-Shape-Topology Truss Optimization And Shortest Path Problems, Gelareh B. Sanjabi

Civil & Environmental Engineering Theses & Dissertations

Efficient numerical algorithms for solving structural and Shortest Path (SP) problems are proposed and explained in this study. A variant of the Differential Evolution (DE) algorithm for optimal (minimum) design of 2-D and 3-D truss structures is proposed. This proposed DE algorithm can handle size-shape-topology structural optimization. The design variables can be mixed continuous, integer/or discrete values. Constraints are nodal displacement, element stresses and buckling limitations.

For dynamic (time dependent) networks, two additional algorithms are also proposed in this study. A heuristic algorithm to find the departure time (at a specified source node) for a given (or specified) arrival time …

A Household Daily Non-Mandatory Activity Participation And Duration Modeling Accounting For Person Level Budget Constraints, Ivana Vukovic

Civil & Environmental Engineering Theses & Dissertations

A key methodological and behavioral innovative component in recent Activity-Based Models (ABMs) used for transportation planning is the household-level non-mandatory activity participation component. While traditional ABMs use a series of simple models to predict non-mandatory activity participation decisions in a sequential manner (which is often not correct), the Multiple Discrete Continuous Extreme Value (MDCEV) model can model both individual and joint non-mandatory activity participation and time allocation decisions in different out-of-home activities of all household members simultaneously. A key advantage of the MDCEV framework is that it accounts for complex intra-household interactions among different household members by allocating the total …

Behavior And Strength Of Rc Spandrel Members Under Unsymmetrical Bending And Torsion Including Cfrp Retrofitting, Muhammad Fahim

Civil & Environmental Engineering Theses & Dissertations

This dissertation presents the outcome of an experimental and theoretical investigation of the behavior and strength of reinforced concrete spandrel members both with and without carbon fiber reinforced polymer (CFRP) retrofitting. Both isolated spandrel members with L-shaped cross section as well as those integrated with reinforced concrete slabs are studied. A series of isolated spandrel members were tested under separate and combined actions of unsymmetrical bending and torsion. Six of these specimens were retrofitted externally with high-strength CFRP strips. Materially nonlinear analysis procedures are also formulated and programmed for the spandrel members with and without CFRP retrofitting. Furthermore, ultimate bending-torsion …

Behavior And Strength Of Non-Prestressed And Prestressed Hillman Composite Beam Including Cfrp Retrofitting, Wajid Khan

Civil & Environmental Engineering Theses & Dissertations

The Hillman Composite Beam (HCB) is a recent innovation used for the first time in 2008 for a bridge construction in USA. It essentially consists of an FRP outer shell, concrete arch inside the shell and steel strands used to tie the two ends of the arch. Being new in the field, the behavior of HCB has not been thoroughly studied. This dissertation presents a study of the flexural behavior and strength of HCB up to the collapse as well as explores the influence of using carbon reinforced polymer (CFRP) retrofitting and prestressed steel for a further increase in HCB …

Dynamic Elasto-Plastic Behavior Of Steel Building Sub-Assemblage Including Cfrp Retrofitting Under Impact Load, Ali Mohammed Salih Aloosi

Civil & Environmental Engineering Theses & Dissertations

This dissertation presents the outcome of a theoretical and experimental study of the dynamic as well as the quasi-static elasto-plastic behavior of a steel building sub-assemblage including carbon fiber reinforced polymer (CFRP) retrofitting. The steel sub-assemblage consists of a beam-column attached to a pair of beams at its top end while its bottom end is fixed. An apparatus is constructed and used for conducting a series of experiments by applying a lateral impact load on the beam-column in the presence or absence of a static axial load. An innovative procedure for determining the shape of the forcing function caused by …

Efficient Domain Decomposition Algorithms And Applications In Transportation And Structural Engineering, Paul W. Johnson Iii

Civil & Environmental Engineering Theses & Dissertations

Domain decomposition is a divide-and-conquer strategy. In the first part of this dissertation, a new/simple/efficient domain decomposition partitioning algorithm is proposed to break a large domain into smaller sub-domains, in such a way as to minimize the number of system boundary nodes and to balance the work load for each sub-domain. This new domain decomposition algorithm is based on the network’s shortest path solution. Numerical results indicate that the new Shortest Distance Decomposition Algorithm outperformed the most widely used METIS algorithm in 21 out of 27 tested (transportation) examples. In the second part of this dissertation, another new/simple and highly …

Changing Trends In Wave Heights In The U.S. Mid-Atlantic Region, Hillary Lane

Civil & Environmental Engineering Theses & Dissertations

The pace and effects of climate change are an area of constant focus for coastal engineers as evolving patterns in the atmosphere worldwide affect the oceans and coasts on a regional and global scale. Surface waves respond to changing wind patterns both locally and from propagating swell, and the difficulty in predicting future wind patterns is well-established. Expectations that climate change will result in more frequent and intense coastal storms and consequently greater wave heights in the North Atlantic are still unrealized, and recent forecasts from a variety of atmosphere-ocean coupled global climate models instead predict decreasing wave heights through …

Global Sensitivity Analysis Of Mat Foundation Behavior By Using Finite Element Modeling, Yang Zhao

Civil & Environmental Engineering Theses & Dissertations

Mat foundation is used mostly for high-rise buildings and, since the demand for high- rise buildings is growing, having extensive understanding of mat foundation behavior leads us into more efficient structural design. Mat foundation behaviors are affected mostly by soil’s materials properties, foundation size, and thickness and loading conditions. In this study, the sensitivity of mat foundation structural responses to some of the design parameters are evaluated. Sobol decomposition, which is a variance-based technique, is used to perform the global sensitivity analysis. In this study, Patran, a finite element-based software, is used for modeling and simulations.

Approximate flexible method is …