Engineering Commons^™

Fracture Mechanics Of High Strength Concrete Members, Rajendra K. Navalurkar

Dissertations

This study investigates the behavior of High Strength Concrete (HSC) under uniaxial state of stresses. Emphasis is placed on experimental evaluation of important mechanical and fracture properties. Owing to high brittleness of HSC, experimental results especially on tensile behavior have been largely limited and scarce. In this research, direct uniaxial tension tests are employed for determination of the post-peak tensile softening characteristics of HSC. The softening characteristics of high strength concrete is found to be considerably different than that of normal strength concrete (NSC). Fracture energies evaluated form the descending branch of the stress softening reveal significant drop in the …

Relationship Between Precipitation, Surface Runoff, And Shallow Water-Table, Manoj Patel

Theses

In this study, a model was developed to describe the relationship between precipitation, surface runoff, and shallow groundwater table in a watershed that is subjected to groundwater extraction and urbanization. Regression analysis of fourteen years (1976-1989) of time series data for precipitation, stream discharge, ground water elevation, and groundwater extraction yielded good correlation between these parameters.

Analysis of the data associated with groundwater recharge and discharge events that occurred in the watershed from 1976 to 1989 yielded a high correlation between the above cited parameters. Regression analysis utilized to predict monthly variations in groundwater elevations showed a fair correlation between …

Comprehensive Conjunctive-Use Management Of Connected Surface Water Groundwater Systems Using Stochastic Inputs And Uncertainties, Seshadri Suryanarayana

Civil & Environmental Engineering Theses & Dissertations

A comprehensive conjunctive-use management model is developed. The dynamics of flow and solute transport processes in connected surface water groundwater systems are integrated by a dual programming management model. The governing aquifer flow parameters and streamflows are treated as stochastic random processes. Multiple realizations of the random field are generated and are explicitly incorporated in a non-linear optimization model along with other system, environmental, and management constraints. To facilitate management of large aquifer systems, a linked simulation-optimization approach is used. The simulation program generates the response matrices for flow and transport processes. The management model then determines optimal well discharges …

The Constant Fracture Angle Model For Cementitious Materials, Suk Ki Kim

Dissertations

Fracture mechanics of concrete has been investigated for the past two decades using linear elastic and nonlinear fracture mechanics concepts. The models proposed so far remain questionable largely due to specimen dependency of the proposed fracture parameters.

In this study, a new approach for modeling the fracture characteristics of concrete and fiber reinforced concrete is proposed. The model depends on the load CMOD relationship rather than the traditional load-deflection principle. Although energy consumed during fracture is definitely a direct function of the load displacement response, it was observed that traditional displacement measurement included an extraneous and erratic portion due to …

Development Of A Multivariate Qsar Model To Predict Desorption Of Halogenated Aliphatic Hydrocarbons From Activated Sludge Solids, Sudhi Ranjan Mukherjee

Dissertations

Data collected from different wastewater treatment processes have provided statistically significant evidence that many toxic organic contaminants on EPA's list of priority pollutants concentrate several orders of magnitude greater than influent concentrations in industrial and municipal wastewater sludges. Because of the reversibility of sorption processes, it is possible for sorbed organic compounds to desorb at a later time, hence making disposal of these sludges a potential problem. Although a number of models have been developed to predict sorption parameters, they have all been based on empirically derived descriptors whose validity is seriously compromised by the variation in available data for …

Discrete Element Modeling Of Dry Granular Material Using A Massively Parallel Supercomputer, David W. Washington

Dissertations

It is the state-of -the-art within Geotechnical Engineering to model soils as systems of particles rather than using the traditional continuum approach. Simulating these systems of particles for geotechnical boundary value problems results in systems which are of necessity large, motivating the application of massively parallel supercomputers. This thesis pursues such an approach.

The following work describes numerical experiments using a Discrete Element Method (DEM) paradigm for soils (Trubal) together with massively parallel computers with Single Instruction Multiple Data (SIMD) architecture. The discrete element method describes the behavior of granular assemblies using the classical mechanics of discrete bodies. The computational …

Development Of A Fiber Optic Polarimetric Sensor For Concrete, Insang Lee

Theses

Development of a fiber optic sensor for embedment in cementitious composites and measurement of displacements associated with the opening of microcracks is described. The sensor can be employed as a transducer for measurement of crack tip opening displacements during fracture tests. A polarization maintaining fiber is used as the sensing element, and transduction mechanism is similar to those of other polarimetric type based sensors. However, the deformation resolving power of the sensor is increased by way of increasing the effective length of the optical fiber. This is done by winding the optical fiber into a coil. A direct relationship between …

Implementation Of Alf Results To Designing Flexible Pavements In Louisiana, Ludfi Djakfar

Doctoral Dissertations

The Louisiana Transportation Research Center (LTRC) recently conducted a research effort using the Accelerated Loading Facility (ALF). The objective of the research was to evaluate a limited number of alternative base materials and construction techniques envisioned to provide a significant reduction in the occurrence of shrinkage and reflected block cracking in the cement-stabilized bases. Nine test sections were constructed for this research, using the same wearing course material but having different thicknesses of crushed stone and soil cement bases and subbases. The soil cement base is the most commonly used base material in Louisiana, whereas crushed stone is a preferred …

A One-Dimensional Model For Storm Breaching Of Barrier Islands, Cheol Shik Shin

Civil & Environmental Engineering Theses & Dissertations

A set of numerical models is developed for simulating the four stages of barrier breaching characterized by one horizontal spatial dimension.

The SBEACH model is employed for the first stage of dune/beach erosion. The Lax-Wendroff two-step explicit scheme for Stage II is developed to simulate initiation of ocean flood propagation on initially dry barrier islands and the method of characteristics (MOC), is employed to compute additional boundary data. The development of the Preissmann implicit scheme for water motion and a forward time centered space explicit scheme for sediment motion in Stages III and IV provide a tool to study the …

The Progressive Failure Analysis Of Cut Slope In Anisotropic Strain Softening Soils, Jong Woon Choi

Civil & Environmental Engineering Theses & Dissertations

The failure phenomena in earth structures such as slopes and embankments on clay foundations are a consequence of the formation of failure surfaces.

A finite difference computer code, FLAC (Itasca Consulting Group, 1993), with the isotropic Mohr-Coulomb plasticity model, is used to analyze the undrained progressive failure of a strain softening soil during a slope excavation process. The focus of the study is on the short-term stability of slopes. In the first series of analyses, which are aimed at the evaluation of anisotropic strength effect on slope stability, the isotropic Mohr-Coulomb plasticity model is slightly modified to implement the anisotropic …

Anaerobic Digestion And Acid Hydrolysis Of Nitrocellulose, Fong-Jung Tai

Dissertations

In this investigation, studies were conducted to evaluate the biodegradation of nitrocellulose in anaerobic batch reactors with and without the supplemental carbon inducers, such as cellulose, cellobiose, and lactose. Results from the anaerobic study show that degradation of nitrocellulose alone is difficult and that nitrocellulose degradative enzymes could be induced by the three inducers tested. As high as 48.91% conversion could be obtained at Cellulose/Nitrocellulose ratio of 1 to I. Studies also indicated that type 20 and 50 celluloses would be more effective and optimum pH was about 6.4 in biodegradation of nitrocellulose. Three testing systems, namely, single-stage, two-stage, and …

Nondestructive Dynamic Load Testing Of Bridges Using Strain Sensors, Suzanne Boland

Theses

This thesis investigates the use of nondestructive bridge load testing utilizing strain sensing equipment. Nondestructive bridge load testing has not been used extensively due to lack of expertise and perceived high cost. It can, however, play a key role when an existing bridge needs to be evaluated. Since most evaluation techniques tend to be conservative, the results from such an evaluation may not represent the real properties of the structural members. The true properties of an existing bridge can be identified using the results from nondestructive static and dynamic load testing. The procedures used to identify a structure with the …

Laboratory And Field Investigations To Determine The Chemical Factors Affecting Zinc And Iron Transport At An Industrial Waste Facility, Michael Lawrence Chasey

Dissertations, Theses, and Masters Projects

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