Engineering Commons^™

Experimental And Theoretical Investigation Of Adsorption Of Water Vapor On Carbon Nanotubes, Pyoungchung Kim

Doctoral Dissertations

The adsorption of water in nanoporous materials becomes an important issue in the environmental fate and applications when one considers the practical use of these materials as adsorbents for hazardous organic compounds in the diverse environments.

In this study, the complexity of water-SWNTs interaction was investigated by morphological and chemical characterization techniques, by gravimetric adsorption measurement and by interpretation of experimental adsorption isotherms by fitting to several existing semi-empirical water adsorption models. Commercially available SWNTs samples were measured for chemical and physical characterization such as O% by x-ray photoelectron spectroscopy, I_D/I_G by Raman spectroscopy and surface and …

Structural Health Monitoring And Damage Evaluation Of Full-Scale Bridges Using Triaxial Geophones: Controlled In-Situ Experiments And Finite Element Modeling, William S. Ragland Ii

Doctoral Dissertations

The purpose of this study was to evaluate the effectiveness of various vibration-based damage detection methods using triaxial vibration records obtained using inexpensive geophones during in-situ, full-scale, damaged bridge tests.

Geophones are passive directional sensors and much cheaper than accelerometers which are typically used for structural vibration measurements. However, magnitude and phase errors associated with a geophone’s output must be corrected for if they are implemented in bridge monitoring systems. This research discusses correction procedures for magnitude and phase errors associated with geophones. A simply supported beam was analyzed to verify that the correction procedures and modal parameter identification procedures …

Development Of Dbt Bridge System With Continuous Joints For Accelerated Construction, Lungui Li

Doctoral Dissertations

Speed of construction has become a critical issue to minimize disruption of traffic and commerce. One of the promising systems for accelerated bridge construction is the use of the decked bulb-tee (DBT) girders for the bridge superstructure. An integral deck that is precast and prestressed with the girder provides benefits of rapid construction along with improved structural performance. However, the limited research and concerns about the use of longitudinal joints as well as intermediate diaphragms limit widespread of the DBT bridge system.

This dissertation presents a study of the continuous for both moment and shear transfer longitudinal joint detail and …

The Influence Of Brick Veneer On Racking Behavior Of Light Frame Wood Shear Walls, Nikola Zisi

Doctoral Dissertations

The racking behavior of an anchored brick veneer – wood frame wall system was investigated analytically. The core wall model simulated a wood frame sheathed with oriented strand board. Brick veneer was then tied to the exterior wall face, and gypsum wallboard sheathing was added on the interior wall face. Two-dimensional linear elastic beam and continuum type elements were used to model these principal wall components. Gap elements were used to prevent sheathing overlap and to model panel bearing at the base. The veneer was supported on compression-only spring elements in the vertical direction and perfectly plastic spring elements in …

Applications Of Electricity In The Rehabilitation And Health Monitoring Of Concrete Structures, Saiprasad Vaidya

Doctoral Dissertations

The dissertation research work presented herein consists of two separate findings: one investigates a potential new coating technique that could be used to rehabilitate deteriorated concrete sewer pipes, and the other researches inducing electrical conductivity into geopolymer concrete to serve as smart material by being able to sense stress changes. Both applications utilize electricity to enhance the performance and/or functionality of hardened cementitious materials.

Microbiologically induced corrosion (MIC) in concrete wastewater conveyance systems is a leading deterioration mechanism in such structures. This work focuses on breaking the MIC cycle by preventing colonization of the bacteria responsible for converting hydrogen sulfide …

Computational Simulation Of Strain Localization: From Theory To Implementation, Shouxin Wu

Doctoral Dissertations

Strain localization in the form of shear bands or slip surfaces has widely been observed in most engineering materials, such as metals, concrete, rocks, and soils. Concurrent with the appearance of localized deformation is the loss of overall load-carrying capacity of the material body. Because the deformation localization is an important precursor of material failure, computational modeling of the onset and growth of the localization is indispensable for the understanding of the complete mechanical response and post-peak behavior of materials and structures. Simulation results can also be used to judge the failure mechanisms of materials and structures so that the …

Seismic Behavior Of Circular Reinforced Concrete Bridge Columns Under Combined Loading Including Torsion, Suriya Prakash Shanmugam

Doctoral Dissertations

"Reinforced concrete (RC) columns of skewed and curved bridges with unequal spans and column heights can be subjected to combined loading including axial, flexure, shear, and torsion loads during earthquakes. The combination of axial loads, shear force, and flexural and torsional moments can result in complex failure modes of RC bridge columns. This study carried out experimental and analytical studies to investigate the seismic performance of circular RC columns under combined loading including torsion. The main variables considered here were (i) the ratio of torsion-to-bending moment (T/M), (ii) the ratio of bending moment-to-shear (M/V) or shear span (H/D), and (iii) …