Engineering Commons^™

Viscoelastic Analysis And Fatigue Characterization Of Bituminous Materials In Two Length Scales Under The Influence Of Aging, Santosh Reddy Kommidi

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

Fatigue cracking in asphalt concrete (AC) is of immense importance to pavement design and analysis because it is one of the most important forms of distress that can lead to structural failure in pavement. Once started, these types of cracks can be combined with other environmental factors leading to detrimental effects such as faster rates of pavement deterioration and shortened pavement life and functionality.

Currently AASHTO TP101, also known as linear amplitude sweep (LAS) specification, is being widely used to evaluate the ability of an asphalt binder to resist fatigue. The LAS method, although mechanistic in its approach, has certain …

Simulation And Prediction Of The Groundwater Level In The Surrounding Area Of The Nebraska Management System Evaluation Area Site In Central Nebraska., Cesar Augusto Gomez Peña

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

An efficient water budget is necessary to develop sustainable practices in irrigated lands and determine future trends. Despite a lack of detailed knowledge, climate change is found to profoundly influence groundwater resources through changes in groundwater recharge, groundwater elevation, and groundwater flow processes. Prediction of the groundwater level (GWL) under a changing climate is essential to improve agricultural management.

The goal of this research is to predict the GWL from 2056 to 2060 in the surrounding area of the MSEA. In order to achieve the target, the first research task is to develop a groundwater flow model and then simulate …

Molecular Dynamics Modeling And Simulation Of Bitumen Chemical Aging, Farshad Fallah

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

Chemical aging of asphalt binder leads to significant changes in its mechanical and rheological properties, resulting in poor pavement behavior and distress. Various laboratory methods have been used to simulate asphalt aging during the service life of the pavement. However, controversy exists regarding the capability of these methods to predict field aging, as various factors interact with the pavement during service and the mechanism behind aging is not fully understood. The two main outcomes of chemical aging are oxidation of asphalt molecules, and change in asphalt SARA (saturate, aromatic, resin, and asphaltene) fractions. Reaction of oxygen with asphalt components forms …

Broadening Understanding Of Roundabout Operation Analysis: Planning-Level Tools And Signal Application, Ahmed Buasali

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

In United States, roundabouts have recently emerged as an effective and efficient alternative to conventional signalized intersections for the control of traffic at junctions. This thesis includes two investigations related to the operations of roundabouts.

The first investigation examines the ability of a planning-level tool (the critical sum method) to serve as an indicator variable for the results of the Highway Capacity Manual’s average delay per vehicle measure for a roundabout facility; to what extent do the results of one predict the results of the other? The critical sum method was found to accurately predict the HCM average delay per …

Impact Of Using Spatially Distributed Soils Information On Flood Hydrograph Simulation With Hec-Hms, Matthew J. Nelson

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

Hydrologic rainfall-runoff models employ numerical equations to simulate the soil absorption of rainfall and resulting runoff. A number of methods have been developed to model these processes, but the parameters used to define these methods can be difficult to directly measure due to the variable nature of soil properties. They often rely on estimation of hydraulic and hydrologic parameters and calibration to produce accurate results.

A challenge with runoff method parameterization is the need for oversimplification using a lumped modeling approach. While distributed hydrologic modeling techniques are now available, distributed runoff methods are limited in use due to the tradition …

Bias And Other Error In Gridded Weather Data Sets And Their Impacts On Estimating Reference Evapotranspiration, Philip A. Blankenau

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

Gridded weather data sets are increasingly used in a variety of hydrologic and agricultural applications due to their complete spatial and temporal coverage. One application of gridded data sets is the estimation of evapotranspiration (ET). Several operational remote sensing (RS) approaches for estimating ET, such as the SEBAL, METRIC and EEFlux models, require estimates of reference ET (ETref), where ETref is expected ET from a hypothetical reference crop of clipped grass or alfalfa. Gridded weather data provide for the computation of ETref in all areas of a remote sensing image, and therefore potentially remove the need for dense weather station …

Influence Of Skew And Nonlinear Deck On Elastic Versus Inelastic Distribution Behavior And Ultimate Capacity Of Steel Girder Bridges, Fayaz Sofi, Joshua Steelman

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

Research Objectives

• Assessment of alternative load distribution methodologies for potential discrepancies that arise when evaluating distribution behavior of skewed steel girder bridges.

• Investigate the influence of skew and material nonlinearities (concrete cracking and steel yielding) on

• Load distribution behavior (elastic versus inelastic).

• System capacities (yielding and ultimate).

Summary and Conclusions • Influence of skew was examined on load distribution behavior, and nonlinear system-based capacities (yielding and ultimate) of composite steel girder bridges in presence of full material nonlinearities. In addition, assessment of two general definitions (beam-line and response fraction approaches) for quantifying load distribution behavior was …

Impact-Resistant Behavior Of Reinforced Concrete Bridge Columns, Chen Fang

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

The damage caused by a vehicle collision on a pier column can be catastrophic for the functionality of a bridge, even a total collapse of the bridge. ❖ A vehicle collision and a subsequent vehicle blast cause more damages on the bridge. ❖ Limited researches have been conducted to investigate the behavior of the bridge subjected to the combined effect of vehicle collision and blast. ❖ It is necessary to analyze the responses of the bridge under the vehicle collision and blast and provide some design suggestions to strengthen the bridge.

Conclusions ❖ The finite element models including column, pile …

Optimizing Steel Railway Truss Bridge Health Monitoring, Ahmed Rageh, Daniel Linzell

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

Problems - Steel Railway Trusses • Aging • Large system – bridge AND railway • Labor intensive condition eval • Reported conditions: Stringer-to-floor beam connections [Haghani 2012] Stringer flange clip angle cracks [Haghani 2012] Unequal eyebars stress distribution [DelGrego 2008] Displaced eyebar pins [DelGrego 2008

Problems – Condition Evaluation • Visual inspection: Prescribed frequency Costly Subjected to human interpretation • Sensors: Focused on a single bridge Extensive array Costly