Engineering Commons^™

Rural To Urban Intercity Transit User Characteristics Analysis, Demand Estimation And Network Design, Hongtai Yang

Doctoral Dissertations

Rural transit always plays a critical role in transporting rural residents, especially the ones who do not have a car, cannot drive, or choose not to drive. Intercity bus (ICB), deviated fixed route transit (DFRT) and demand responsive transit (DRT) are three major modes of rural public transportation. Although there are more DFRT and DRT service providers and services in the US, due to institutional issues, there are much more studies about ICB than DFRT and DRT. Meanwhile, state governments are struggling on how to improve the rural transit system with limited budget. This dissertation is aimed to fill the …

Bedload Transport Sampling, Characterization And Modeling On A Southern Appalachian Ridge And Valley Stream, Patrick Lasater Mcmahon

Doctoral Dissertations

Estimates of bedload transport rates developed from existing transport models are notoriously inaccurate(Wilcock 2001). The gravel bed models addressed in this study include the Meyer-Peter and Muller; Parker, Klingeman, and McLean; and Wilcock two-fraction models. The question of whether or not these models predict bedload transport rates in a Southern Appalachian Ridge and Valley stream is complicated by the fact that these models have only been previously assessed in terms of their agreement with bedload transport rates measured in the Western regions of the U.S. Further, due to the strongly non-linear form of bedload transport models discrete errors and cumulative …

Effects Of Data Resolution And Human Behavior On Large Scale Evacuation Simulations, Wei Lu

Doctoral Dissertations

Traffic Analysis Zones (TAZ) based macroscopic simulation studies are mostly applied in evacuation planning and operation areas. The large size in TAZ and aggregated information of macroscopic simulation underestimate the real evacuation performance. To take advantage of the high resolution demographic data LandScan USA (the zone size is much smaller than TAZ) and agent-based microscopic traffic simulation models, many new problems appeared and novel solutions are needed. A series of studies are conducted using LandScan USA Population Cells (LPC) data for evacuation assignments with different network configurations, travel demand models, and travelers’ compliance behavior.

First, a new Multiple-Source-Nearest-Destination Shortest Path …

Investigation Of Asphalt Pavement Mixture Blending Utilizing Analytical Chemistry Techniques, Benjamin Frank Bowers

Doctoral Dissertations

The use of Reclaimed Asphalt Pavement (RAP) in new pavement mixtures is a topic of interest throughout the transportation industry and academia due its economic and environmental implications. There is concern however about how well the binder from the RAP blends with new, virgin binder when the mixture is created. Insufficient blending of the aged and unaged binders may compromise the long-term pavement performance. In this study, an enhanced staged extraction method is coupled with two chemical testing techniques to develop a novel approach for evaluating blending efficiency from a qualitative and quantitative perspective: Gel Permeation Chromatography (GPC) and Fourier …

Multi-Segment Multi-Criteria Approach For Selection Of Trenchless Construction Methods, Ashikul Islam

Doctoral Dissertations

The research work presented in this thesis has two broad objectives as well as five individual goals. The first objective is to search and determine the minimum cost and corresponding goodness-of-fit by using a different combination of methods that are capable of resolving the problem that exists in multiple segments. This approach can account for variations in unit price and the cost of the design and the inspection associated with multiple methods. The second objective is to calculate the minimum risk for the preferred solution set. The five individual goals are 1) reduction in total cost, 2) application of Genetic …

Structural Health Monitoring And Damage Identification Of Bridges Using Triaxial Geophones And Time Series Analysis, Reza Vasheghani Farahani

Doctoral Dissertations

This study uses the vibration data of two full-scale bridges, subjected to controlled damage, along the I-40 west, near downtown Knoxville, TN, to evaluate the feasibility of time series-based damage identification techniques for structural health monitoring. The vibration data was acquired for the entrance ramp to James White Parkway from I-40 westbound, and the I-40 westbound bridge over 4th Avenue, before the bridges were demolished during I-40 expansion project called Smartfix40. The vibration data was recorded using an array of triaxial geophones, highly sensitive sensors to record vibrations, in healthy and damaged conditions of the bridges. The vibration data is …

In-Plane Shear Investigation On Masonry Walls, Shane Chandler Morrison

Doctoral Dissertations

Analysis has been performed on approximately 200 shear walls of various masonry types, reinforcement, and grouting scenarios to determine the trends of various wall parameters to strength. The database is assembled from that belonging to researchers over the last 30 years.

Strut-and-tie methods from current concrete codes are employed and new methods proposed to calculate the in-plane shear strength of masonry walls. In addition, a simplified method based upon strut-and-tie methodology is presented to calculate the masonry contribution to the in-plane strength of these walls, with contributions from axial load and horizontal reinforcement based upon past data and efficiency of …

Rheological Study Of Asphalt Binders With A Wax-Based Warm Mix Additive And Its Relationships To Mix Compaction And Rutting, Rajan Saha

Doctoral Dissertations

Although the energy saving Warm Mix Asphalt (WMA) technology that produces asphalt mixes at lower temperatures are around for about a decade, there still exist some concerns that are hindering its wide spread implementation. The overall objective of this study is to investigate if the viscosity reductions at higher temperatures have any impacts on asphalt mix compaction and rutting performances. This study reveals that there exists a critical temperature for each asphalt binder below which viscosity will increase with addition of Sasobit®. Therefore, compaction below the critical temperature can negatively impact density.

For PG 64-22, the critical temperature is 104 …

Enamel Coated Steel Reinforcement For Improved Durability And Life-Cycle Performance Of Concrete Structures: Microstructure, Corrosion, And Deterioration, Fujian Tang

Doctoral Dissertations

"This study is aimed (a) to statistically characterize the corrosion-induced deterioration process of reinforced concrete structures (concrete cracking, steel mass loss, and rebar-concrete bond degradation), and (b) to develop and apply three types of enamel-coated steel bars for improved corrosion resistance of the structures. Commercially available pure enamel, mixed enamel with 50% calcium silicate, and double enamel with an inner layer of pure enamel and an outer layer of mixed enamel were considered as various steel coatings. Electrochemical tests were respectively conducted on steel plates, smooth bars embedded in concrete, and deformed bars with/without concrete cover in 3.5 wt.% NaCl …

Shear And Fracture Behavior Of High Performance Concretes, Mahdi Arezoumandi

Doctoral Dissertations

"Concrete is the most widely used man-made material in the world. Like other materials, it has been improved over time. Nowadays, with continued development of science and technology, a new generation of concretes is produced and is termed high performance concretes. A review of previously published work indicates that very few studies (in some cases none) have addressed the structural behavior of full-scale, high performance concrete elements. This study investigated the shear and fracture behavior of two types of high performance concrete - high-volume fly ash concrete (HVFAC) and self-consolidating concrete (SCC). The HVFAC incorporates up to 70% cement replacement …

Numerical Analyses Of Long Carbon Fiber Reinforced Concrete Panels Exposed To Dynamic Loading, Zahra Sadat Tabatabaei

Doctoral Dissertations

"The purpose of this research was to evaluate impact and blast performance of long carbon fiber reinforced concrete experimentally and numerically. Experimental tests were conducted on plain concrete (PC), reinforced concrete, and four different types of long carbon fiber reinforced concrete (LCFRC). The results from each test were then compared to one another. This comparison indicates that adding long carbon fibers to concrete both increases the post-cracking behavior of concrete and decreases the spalls in either an impact or blast test. Among all of the fibers tested, Fiber Type B3 outperformed the other fibers, absorbing more energy during impact. Numerical …