Civil Engineering Commons^™

Determination Of Area Of Fire Origin Through Examination Of Structural Failure And Deformation, Andrew Thomas Tinsley

Doctoral Dissertations

The effects of fire on steel have long been noted and studied. However, a scientific connection between the area of origin for a fire and the amount of steel deformation observed at the scene has never been established. The development and implementation of this type of analysis has the potential to decrease investigation times significantly as the types of structures to which this method would be applicable are typically large, expansive structures. In order to investigate the relationship between structural steel deformations and a fire’s origin, a series of six tests were performed in a smaller size portal frame steel …

Neutron Diffraction Study Of Engineering Materials Subjected To Complex Loadings, Jeffrey R. Bunn

Doctoral Dissertations

No studies using diffraction have specifically aimed to study the (hkl) specific shear strain of lattice planes to the application of pure shear due to applied torsion. Also no measures of strain resultant from combined loads of tension and shear stress applied simultaneously have been performed. Current techniques simply measure the planar response to axial stress and cannot provide shear strains directly. Shear moduli are not necessarily related through traditional continuum mechanics to planar Youngs’ moduli (E_hkl) from these axial experiments for all materials. This is of significance as most engineering components fail under the …

Impacts Of Climate Change On The Evolution Of The Electrical Grid, Melissa Ree Allen

Doctoral Dissertations

Maintaining interdependent infrastructures exposed to a changing climate requires understanding 1) the local impact on power assets; 2) how the infrastructure will evolve as the demand for infrastructure changes location and volume and; 3) what vulnerabilities are introduced by these changing infrastructure topologies. This dissertation attempts to develop a methodology that will a) downscale the climate direct effect on the infrastructure; b) allow population to redistribute in response to increasing extreme events that will increase under climate impacts; and c) project new distributions of electricity demand in the mid-21^st century.

The research was structured in three parts. The first …

Migrating Towards Using Electric Vehicles In Fleets – Proposed Methods For Demand Estimation And Fleet Design, Taekwan Yoon

Doctoral Dissertations

Carsharing and electric vehicles have emerged as sustainable transportation alternatives to mitigate transportation, environmental, and social issues in cities. This dissertation combines three correlated topics: carsharing feasibility, electric vehicle carsharing fleet optimization, and efficient fleet management. First, the potential demand for electric vehicle carsharing in Beijing is estimated using data from a survey conducted the summer of 2013 in Beijing. This utilizes statistical analysis method, binary logit regression. Secondly, a model was developed to estimate carsharing mode split by the function of utilization and appropriate carsharing fleet size was simulated under three different fleet types: an EV fleet with level …

Stability, Erosion, And Morphology Considerations For Sustainable Slope Design, Isaac Andres Jeldes Halty

Doctoral Dissertations

The construction of more natural and sustainable earth slopes requires the consideration of erosion and runoff characteristics as an integral part of the design. These effects not only result in high costs for removal of sediment, but also a profound damage to the ecosystem. In this dissertation, innovative techniques are developed such that more natural appearing slopes can be designed to minimize sediment delivery, while meeting mechanical equilibrium requirements. This was accomplished by: a) examining the fundamental failure modes of slopes built with minimum compaction (FRA) to enhance quick establishment of forest, b) investigating the geomechanical and erosion stability of …

Selected Durability Studies Of Geopolymer Concrete With Respect To Carbonation, Elevated Temperature, And Microbial Induced Corrosion, Mohammad Sufian Badar

Doctoral Dissertations

This thesis reports a comprehensive study related to the experimental evaluation of carbonation in reinforced geopolymer concrete, the evaluation of geopolymer concretes at elevated temperature, and the resistance of geopolymer concrete to microbial induced corrosion (MIC).

Carbonation: Reinforced concretes, made of geopolymer, prepared from two class F fly ashes and one class C fly ash, were subjected to accelerated carbonation treatment for a period of 450 days. Electrochemical, microstructure and pore structure examinations were performed to evaluate the effect of corrosion caused due to carbonation. GPC specimens prepared from class F fly ash exhibited lower corrosion rates by a factor …

Longitudinal Analysis Of Crash Frequency Data, Mojtaba Ale Mohammadi

Doctoral Dissertations

"This study comprises mainly of three papers. First, a systematic evaluation of the effects of Missouri's Strategic Highway Safety Plan between 2004 and 2007 is presented. Negative binomial regression models were developed for the before-through-change conditions for the various collision types and crash severities. The models were used to predict the expected number of crashes assuming with and without the implementation of MSHSP. This procedure estimated significant reductions of 10% in crashes frequency and a 30% reduction for fatal crashes. Reductions in the number of different collision types were estimated to be 18-37%. The results suggest that the MSHSP was …

A Unified Bond Theory, Probabilistic Meso-Scale Modeling, And Experimental Validation Of Deformed Steel Rebar In Normal Strength Concrete, Chenglin Wu

Doctoral Dissertations

"Bond between deformed rebar and concrete is affected by rebar deformation pattern, concrete properties, concrete confinement, and rebar-concrete interfacial properties. Two distinct groups of bond models were traditionally developed based on the dominant effects of concrete splitting and near-interface shear-off failures. Their accuracy highly depended upon the test data sets selected in analysis and calibration. In this study, a unified bond model is proposed and developed based on an analogy to the indentation problem around the rib front of deformed rebar. This mechanics-based model can take into account the combined effect of concrete splitting and interface shear-off failures, resulting in …

Seismic Repair Of Bridge Columns With Interlocking Spirals And Fractured Bars, Yang Yang

Doctoral Dissertations

"During earthquakes, reinforced concrete (RC) bridge columns may experience different levels of damage such as cracking, spalling, or crushing of concrete and yielding, buckling, or fracture of reinforcing bars. This study developed and assessed permanent and emergency methods to repair damaged bridge columns with fractured longitudinal reinforcement through experimental and modeling work. The permanent repair method involved replacement of the plastic hinge region by removal of spirals, replacement of longitudinal bar segments by mechanically splicing with new bars segments attached with mechanical couplers, replacement of concrete, and installation of an externally bonded carbon fiber reinforced polymer (CFRP) jacket. The emergency …

Rapid Repair Of Severely Damaged Rc Columns Under Combined Loading Of Flexure, Shear, And Torsion With Externally Bonded Cfrp, Ruili He

Doctoral Dissertations

"This research aimed to develop a technique to rapidly repair reinforced concrete (RC) bridge columns for emergency service restoration after severe earthquake damage has occurred. Experimental and analytical studies were conducted to study the performance and effectiveness of the proposed repair method. The experimental study included a series of 1/2-scale RC square bridge columns originally tested to failure under constant axial and increasing cyclic lateral loadings resulting in combined flexure, shear, and torsion with different torsional-to-flexural moment ratios. Using externally bonded carbon fiber reinforced polymer (CFRP) sheets, each column was repaired over a 3-day period and then retested under the …

Plant Uptake Of Environmental Contaminants: Applications In Phytoscreening, Matthew Alan Limmer

Doctoral Dissertations

"Plants interact directly with their surroundings, extracting nutrients and water from the subsurface to support growth and development of the plant. Through the roots, plants also exude and uptake numerous chemicals. Many of the pathways can also be used by environmental contaminants to be translocated to above ground plant tissues. Such uptake of contaminants has proven useful in remediation and phytoscreening - the use of plants to delineate contaminant plumes. Sampling of trees at contaminated field sites has been used to identify areas of groundwater contaminated with a variety of chlorinated solvents. The use of plants as contaminant biosensors requires …