Digital Commons Network^™

Traction And Agricultural Tractor Tire Selection Studies., Francois Pascal Brassart

LSU Historical Dissertations and Theses

A machine was built to study non-rolling tire stiffness and damping coefficients of agricultural tractor tires in the vertical direction. Static deflection on a rigid surface was measured as a function of vertical load. During dynamic experiments, a sinusoidal forcing function was imposed on the test tire to determine dynamic stiffness and damping coefficient from load and deflection measurements. The experimental setup and methodology are described. Ten tires were tested. Both static and dynamic stiffnesses appeared linearly related to inflation pressure. No correlation was found between dynamic properties and excitation frequency. Comparisons among stiffness and damping coefficient values were made …

Development Of Instrumentation To Study The Effects Of Aging On The Small Strain Behavior Of Sands, Heather Jane Miller

Doctoral Dissertations

The shear modulus is a direct indicator of sand fabric stiffness. It is a primary soil parameter affecting the response of sand deposits to cyclic shearing stresses and strains. Among the various factors which influence the shear modulus, the age at testing has been least studied. Typically, age effects have been thought of only in terms of geologic time. Recently, however, observations indicate that age effects operate over much shorter time spans (weeks to months), and that these age effects may be reversible; i.e. the sand fabric becomes stiffer as it evolves with time, but then the acquired stiffness may …

The Utilization Of Municipal Solid Waste Combustion Bottom Ash As A Paving Material, Xishun Zhang

Doctoral Dissertations

A research project was conducted to investigate the potentials of using municipal solid waste combustion bottom ash as a paving material. The effort focused on (i) characterization of the time-dependent properties of the bottom ash, (ii) bottom ash utilization as an unbound material in road subbase and base application, and (iii) bottom ash utilization as an aggregate substitution in hot mixture asphalt. A series of standard or non-standard procedures were employed to evaluate bottom ash behavior.

Results indicate that variability of the physical properties of the bottom ash produced during the two years study period is relatively small in view …

Ground Water Flow Model For Fractured Media, Ernesto Da Silva Pitombeira

Doctoral Dissertations

In fractured rock systems, ground water flow is not as simple and as methodical as in a porous medium. To create a numerical model of such a flow system, a four-part algorithm was written, which included MATLAB$\sp\circler$ as a fundamental component. It was intended that the model output define the zone of influence of pumping stresses. The four model parts are, sequentially: generation of the interconnected fracture geometry; generation of the linear finite element grid; the hydraulic calculations and the influence zone delineation. MATLAB$\sp\circler$ is used to stochastically generate the fracture geometry from empirical estimates of the probability distributions of: …

Micro- And Macro-Experimental Investigations For Modeling Damage In Metal Matrix Composites., Anthony Ray Venson

LSU Historical Dissertations and Theses

Experimental investigations and procedures for the determination of damage are presented for the macro- and micro-analysis of a SiC-Titanium Aluminide metal matrix composite (MMC). Uniaxial tension tests are performed on laminate specimens of two different layups. The layups are balanced symmetric and given as (0/90)$\sb{s}$ and ($\pm45)\sb{s}$, each containing four plies. Dogbone shaped flat plate specimens are fabricated from each of the layups. Specimens for the different layups are loaded to various load levels ranging from rupture load down to 70% of the rupture load at room temperature. By loading specimens to various load levels, damage evolution is experimentally evaluated …

The Development Of Bridge Inspection Strategies Based On A Statistical Analysis Of Deterioration In Underwater Structures., Mark Deymond Fugler

LSU Historical Dissertations and Theses

A comprehensive statistical analysis was performed on the condition data generated by a statewide underwater inspection of bridges in Louisiana. The research defined pertinent underwater structural decay characteristics and established a method for establishing a bridge's propensity for underwater deterioration based upon those relevant factors. The inspection results were reviewed to ascertain the impact of human-bias on the consistency in the bridge condition ratings. Using a set of importance factors obtained through a questionnaire submitted to a group of inspectors, the fuzzy set theory was employed to assist in the removal of data incongruities. A combination of pure fuzzy set …

Use Of Uncertainty Methodology In Identification And Classification Of Soils Based Upon Cpt., Zhongjie Zhang

LSU Historical Dissertations and Theses

The current Cone Penetration Test (CPT) soil engineering classifications have two kinds of uncertainties: randomness and fuzziness. Research indicates that possible solutions to these uncertainties can only be worked out through modeling them. Therefore, a systematic investigation is performed and some preparative tasks are done in advance. First, an efficient soil classification index, U, is defined and several CPT soil classification charts are simplified accordingly. Second, a moving window approach based upon an Intraclass Correlation Coefficient (ICC) to determine normal soil behavior units is adopted so that a correlation between soil types and soil behavior units can be established. Based …

Dynamic Analysis Of Single Piles And Pile Groups, Hazem Gamal El-Marsafawi

Digitized Theses

The determination of stiffness and damping of piles is an important step in the analysis of pile-supported structures subjected to dynamic loading.;The first part of this study examines the use of approximate methods to evaluate the impedance functions of single piles and pile groups. The group impedances derived from the superposition of the two-pile solution are compared with those obtained from direct analysis. Good agreement is observed for floating piles in homogeneous and nonhomogeneous soil profiles. An extensive set of dynamic pile-soil-pile interaction factors is presented in a form suitable for interpolation. An approximate approach for the evaluation of pile-group …

Nonlinear Analysis Of Piles With Application Of Offshore Tower Response, Nagger Mohamed El

Digitized Theses

Three main areas are addressed in this study: (1) Statnamic test analysis. In recent years a new type of pile test employing a short-duration load was developed that became known as pile Statnamic test. A method of dynamic analysis has been formulated for this test. The aim of the analysis is twofold: to calculate the pile head displacements in such a way that a satisfactory match with the data measured during the test is obtained; and using the model parameters established from this comparison to predict the pile capacity. The model is one-dimensional and accounts for slip and energy dissipation …

Dynamic Analysis Of Turbine-Generator-Foundation Systems, Weiming Liu

Digitized Theses

In this dissertation a comprehensive investigation on the dynamic characteristics of turbine-generator-foundation systems is performed. All the major components of the system, including turbine-generator casing, shaft, rotors, journal bearings, deck, piers, foundation mat, piles, and soil medium, have been included. Full interaction between the turbine-generator set, the foundation superstructure, and the soil medium, is considered.;A hybrid method is proposed to establish the mathematical model for the turbine-generator-foundation system, which includes finite element discretization of turbine-generator and foundation superstructure, combined with a soil stiffness matrix derived from the dynamic Green functions of the soil. The soil is modeled as a transversely …

Analysis Of Initial Stresses, Long Term Deformation And Rock Lining Interaction In Tunnels, Ashraf Mohamed Hefny

Digitized Theses

For the design of underground structures in rocks, the initial stresses in the rock mass are a pre-requisite for any analysis. The hydraulic fracturing technique is the only practical method for determining these initial stresses at great depth. For vertical fractures, existing solutions for calculation of stresses are satisfactory. For horizontal or mixed-mode fractures, appropriate solutions are required.;Closed-form solutions for horizontal and mixed-mode fractures including strength anisotropy are developed and applied to several case histories. The reinterpreted horizontal stresses agreed with results derived from convergence measurements and they are also consistent with field observations of excavation performance, indicating that the …