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 Title
 Investigation of debonding and crack kinking in foam core sandwich beams.
 Creator
 Prasad, Srinivas., Florida Atlantic University, Carlsson, Leif A., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Debond failures in structural sandwich may lead to severe reductions in loadbearing capability of the structure because of impartial transfer of shear and tensile forces between facing and core due to the lack of interfacial bonding. Analysis of interfacial bonding in sandwich specimens subjected to transverse tensile and shear forces is presented. Stress intensity factors computed based on the neartip displacement field are related to experimental crack growth observation on the sandwich...
Show moreDebond failures in structural sandwich may lead to severe reductions in loadbearing capability of the structure because of impartial transfer of shear and tensile forces between facing and core due to the lack of interfacial bonding. Analysis of interfacial bonding in sandwich specimens subjected to transverse tensile and shear forces is presented. Stress intensity factors computed based on the neartip displacement field are related to experimental crack growth observation on the sandwich beams with aluminum skins on a wide range of PVC foam cores. Experimentally it was found that the crack tends to grow at the interface between the bondline and core as opposed to skin/bondline interface. In shear dominated fields, a preexisting flow tended to deflect into the core rather than grow along the interface. The tendency for kinking and the direction of the kink is examined experimentally and analyzed using the finite element method.
Show less  Date Issued
 1993
 PURL
 http://purl.flvc.org/fcla/dt/14861
 Subject Headings
 Finite element method, Sandwich construction, Diffusion bonding (Metals), Fracture mechanics
 Format
 Document (PDF)
 Title
 Investigation of debonding failures in sandwich constructions.
 Creator
 Sendlein, Lyle Scott., Florida Atlantic University, Merry, Stephanie L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Debonding failure of cored marine composite materials is investigated. A new test method that subjects the bond line between the core and the face sheets to a shear stress singularity is presented and studied analytically by laminated beam shear deformation theory, numerically by the finite element method, and experimentally with specimens of glass/polyester face sheets on balsa wood or PVC core sandwich beams.
 Date Issued
 1989
 PURL
 http://purl.flvc.org/fcla/dt/14519
 Subject Headings
 Mobile communication systemsDesign, Wireless communication systemsTechnological innovations, Cellular telephonesDesign
 Format
 Document (PDF)
 Title
 Synchronous spatial array processing for underwater vehicle tracking.
 Creator
 Normand, Olivier., Florida Atlantic University, Schock, Steven G., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Navigation of Unmanned Underwater Vehicles (UUVs) is commonly assisted in confined areas by acoustic positioning systems. The Department of Ocean Engineenng at Florida Atlantic University is developing an altemative system based on submerged modems. This thesis describes an optimal target location estimation technique using a multichannel spatial receiver array (Millscross) used as a development tool combined with a synchronous modem and transponder network mounted on buoys and UUVs. The...
Show moreNavigation of Unmanned Underwater Vehicles (UUVs) is commonly assisted in confined areas by acoustic positioning systems. The Department of Ocean Engineenng at Florida Atlantic University is developing an altemative system based on submerged modems. This thesis describes an optimal target location estimation technique using a multichannel spatial receiver array (Millscross) used as a development tool combined with a synchronous modem and transponder network mounted on buoys and UUVs. The Millscross provides a reference to evaluate the performance of the navigation estimator. Spatial array principles are used to develop decoding and beamforming techniques to process modem messages, enabling the end user (the UUV) to estimate in realtime its own position and navigate in space. A simulation was used to compare actual results with theory and determine the processing and decoding algorithms. These algorithms were then applied to real data to estimate the target position (direction of arrival and geodetic coordinates).
Show less  Date Issued
 2002
 PURL
 http://purl.flvc.org/fcla/dt/12917
 Subject Headings
 Underwater navigation, Underwater acoustics, Signal processingDigital techniques
 Format
 Document (PDF)
 Title
 Stress intensity factors and weight functions for surface cracks using boundary/finite element alternating methods.
 Creator
 Mu, Ruijia., Florida Atlantic University, Reddy, Dronnadula V., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

In the present investigation, the boundary/finite element alternating methods are used to evaluate the stress intensity factors and weight functions for surface crack problems. For two dimensional problems, Westergaard stress functions are used to find the analytical solutions for an infinite plate with an embedded crack, subjected to crack face tractions, and the boundary element method for the numerical solution. The stress intensity factors and weight functions for an arbitrary plate with...
Show moreIn the present investigation, the boundary/finite element alternating methods are used to evaluate the stress intensity factors and weight functions for surface crack problems. For two dimensional problems, Westergaard stress functions are used to find the analytical solutions for an infinite plate with an embedded crack, subjected to crack face tractions, and the boundary element method for the numerical solution. The stress intensity factors and weight functions for an arbitrary plate with an edge crack subjected to mixed mode loads are obtained by the alternating technique. For three dimensional problems, an elliptical coordinate system and the gravity potential functions are used to derive the three dimensional analytical solutions for an infinite solid with an embedded crack. The analytical solutions are derived for the cases of shear tractions and normal tractions, separately, by assuming that the tractions are symmetric about both the major and minor axes. Superposition gives the general solutions. The analytical solutions and the finite element method, in conjunction with alternating technique, are used to evaluate the stress intensity factors for a solid with a semielliptical surface crack, subjected to arbitrary loads. A general approach to evaluate the weight functions for a two dimensional plate with a three dimensional semielliptical surface crack is formulated. Numerical examples are evaluated using the formulation developed in the present investigation. The results show good agreement with those from classical solutions. The convergence characteristics of the alternating methods are also discussed. Finally, the formulation is applied to welded plate Tjoints with edge/semielliptical surface cracks, subjected to three point bending, to obtain stress intensity factors.
Show less  Date Issued
 1992
 PURL
 http://purl.flvc.org/fcla/dt/12319
 Subject Headings
 Fracture mechanics, Finite element methodData processing, MaterialsFatigue, Strains and stresses
 Format
 Document (PDF)
 Title
 Structural intensity measurements in thick structures.
 Creator
 Vallory, Joelle., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Structural intensity is propagated through a thick structure by both inplane and outofplane (transverse) waves. These waves propagate at different phase speeds and therefore it is important to distinguish the components of the structural intensity associated with each wave type. To show the presence of these different wave components, experimental results are performed on a thick beam. Using a frequencywavenumber analysis, the different waves and contributions to the structural intensity...
Show moreStructural intensity is propagated through a thick structure by both inplane and outofplane (transverse) waves. These waves propagate at different phase speeds and therefore it is important to distinguish the components of the structural intensity associated with each wave type. To show the presence of these different wave components, experimental results are performed on a thick beam. Using a frequencywavenumber analysis, the different waves and contributions to the structural intensity are identified. The significance of the contributions to the structural intensity are a function of both frequency and thickness of the structure. Using simulated measurements on a thick Lshaped plate, the relative importance between the inplane and outofplane contributions to structural intensity as a function of frequency and thickness is demonstrated. It is shown that inplane wave contributions increase in importance as frequency or thickness increases.
Show less  Date Issued
 1991
 PURL
 http://purl.flvc.org/fcla/dt/14697
 Subject Headings
 Structural dynamics, Noise, Vibration
 Format
 Document (PDF)
 Title
 Study of edge effects in laminated sandwich specimens.
 Creator
 Mankuzhy, Pradeep Prabhakaran., Florida Atlantic University, Merry, Stephanie L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Different methods have been employed to calculate the interlaminar stresses and to study the edge effect in a laminated sandwich specimens under uniaxial tension. However, Finite Element Analysis and Force Balance Method produced stress values which disagreed in both magnitude and sign, a controversy which exists in the case of composite laminates also. Experimental methods, photoelastic coating method and strain gaging, were attempted to obtain the strain distribution on the top surface of a...
Show moreDifferent methods have been employed to calculate the interlaminar stresses and to study the edge effect in a laminated sandwich specimens under uniaxial tension. However, Finite Element Analysis and Force Balance Method produced stress values which disagreed in both magnitude and sign, a controversy which exists in the case of composite laminates also. Experimental methods, photoelastic coating method and strain gaging, were attempted to obtain the strain distribution on the top surface of a sandwich specimen in three point bending. However, these conventional methods failed to show the sharp strain gradient that exists near the free edge. The Force Balance Method was simplified for sandwich specimens by considering the face laminate as a homogeneous and orthotropic material with averaged properties. Simplified expressions were also obtained for calculating the boundary layer thickness. The boundary layer thickness was found to vary linearly with core thickness for the cases considered.
Show less  Date Issued
 1989
 PURL
 http://purl.flvc.org/fcla/dt/14523
 Subject Headings
 Sandwich constructionFatigue, Composite materials, Strains and stresses, Structural analysis (Engineering)
 Format
 Document (PDF)
 Title
 Subsurface structure of an atmospherically forced water column in littoral waters.
 Creator
 Chernys, Michael., Florida Atlantic University, Dhanak, Manhar R., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The developing subsurface structure of a shallow subtropical water column during the passage of cold lowpressure atmospheric front is characterized through synoptic and insitu observations during the passage of three separate fronts over South Florida. Subsurface distribution of current, salinity, temperature, density and dissipation rates were examined using an autonomous underwater vehicle (AUV), shipbased instruments, moored instruments and an Ocean Surface Current Radar (OSCR) as the...
Show moreThe developing subsurface structure of a shallow subtropical water column during the passage of cold lowpressure atmospheric front is characterized through synoptic and insitu observations during the passage of three separate fronts over South Florida. Subsurface distribution of current, salinity, temperature, density and dissipation rates were examined using an autonomous underwater vehicle (AUV), shipbased instruments, moored instruments and an Ocean Surface Current Radar (OSCR) as the fronts passed through the region. Airfoil shear probes mounted in a package on the nose of the AUV were used to measure the level and distribution of smallscale turbulence in the water column and to estimate the insitu dissipation rate of turbulent kinetic energy. Prevailing meteorological conditions were determined from two NOAA CMAN stations and, for two of the experiments, from a local Air Sea Interaction Spar buoy (ASIS). The first atmospheric front examined was in December 1998. A significant 10°C drop in air temperature was recorded. The AUV carried out several preprogrammed surveys over a 6day period. A turbulent kinetic energy dissipation rates of O(106W/kg) were observed in the water column during the passage of the front. Fetchlimited, offshore, windinduced surface and subsurface currents were identified during the passage of the front on April 9, 2000. As the winds increased in magnitude and shifted direction, a change in surface current was apparent in the OSCR observations. A bottommounted ADCP and an AUVmounted ADCP both recorded distinct corresponding contributions to the subsurface current due to the winds. Clockwise rotation of the current profile in the water column, consistent with windgenerated currents, was observed. A third lowpressure cold front passed through the region on April 18 an 19, 2000. AUV surveys were carried out as the front passed over the region for 19 hours within a 24hour period. Dissipation rates reached O(10 6W/kg) during the period of the survey and decreased to O(10 8W/kg) subsequently. The distribution of dissipation rate appeared to agree with the characteristic log law for windinduced turbulence at the start of the passage of the front, but was significantly higher subsequently and more dependent on the combination of convective fluxes and wind stress.
Show less  Date Issued
 2002
 PURL
 http://purl.flvc.org/fau/fd/FADT12001
 Subject Headings
 TurbulenceMeasurement, Oceanographic submersibles
 Format
 Document (PDF)
 Title
 Structural modification of Bascule bridges for noise mitigation.
 Creator
 Takkasila, Harinatha Reddy., Florida Atlantic University, Reddy, Dronnadula V., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Noise mitigation and enhancement of skid resistance on Bascule bridge decks, including bridges, pose a considerable challenge. Typically measured noise levels that vary from 60 to 70 dB(A) need to be reduced to eliminate public concern. The objective of this investigation was to find possible modifications to the structure of the open grid decking to reduce the radiated noise from the bridges and at the same time to improve the skid resistance. This study was complementary to the acoustic...
Show moreNoise mitigation and enhancement of skid resistance on Bascule bridge decks, including bridges, pose a considerable challenge. Typically measured noise levels that vary from 60 to 70 dB(A) need to be reduced to eliminate public concern. The objective of this investigation was to find possible modifications to the structure of the open grid decking to reduce the radiated noise from the bridges and at the same time to improve the skid resistance. This study was complementary to the acoustic testing completed in September 1994 at Florida Atlantic University. Deck panels infilled with different types of lightweight infill material for noise mitigation, were tested for fatigue performance and abrasion characteristics. The computer software ANSYS was used to model the grid panel and analyzed for different depths of concrete infill to evaluate the composite action between the infill concrete and the grid panel. A typical case study on counterbalance dynamics of an infilled deck for the Sunrise Boulevard Bridge, included horsepower requirements, trunnion bearing and bending stresses, and flexural strength adequacies of the stringer and floor beams. Skid resistance values for twelve bridges from E274 and Ganalyst measurements were compared for dry and wet conditions, and accident statistics compiled for the period 19881992. The cost analysis of identified options was carried out.
Show less  Date Issued
 1996
 PURL
 http://purl.flvc.org/fcla/dt/15284
 Subject Headings
 BridgesDesign and construction, Bridges, Iron and steelFloorsEvaluation, BridgesNoise, Tires, Traffic noise
 Format
 Document (PDF)
 Title
 Sensitivity analysis for machine cell formation using mathematical model and computer simulation.
 Creator
 Yelamanchi, Ravi., Florida Atlantic University, Han, Chingping (Jim), College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This thesis presents a mathematical model for the sensitivity analysis of machine cell formation. Computer programs in C were developed. A statistical simulation model is developed to test and verify the mathematical model. The data for machine cell formation in cellular manufacturing is organized in a machine component chart representing the machining requirements of parts in the product mix. The existing machine cell formation models treat the product mix as deterministic. To study the...
Show moreThis thesis presents a mathematical model for the sensitivity analysis of machine cell formation. Computer programs in C were developed. A statistical simulation model is developed to test and verify the mathematical model. The data for machine cell formation in cellular manufacturing is organized in a machine component chart representing the machining requirements of parts in the product mix. The existing machine cell formation models treat the product mix as deterministic. To study the probabilistic nature of the cellular manufacturing, a sensitivity analysis model is presented. The model optimizes the formation of intercellular material handling cost for the machine cell within the constrains of the probability of the product mixture. The results of the mathematical model is compared with the results of the simulation model. It shows that the probabilistic product mix has a influence on the efficiency of the machine cell and the associated total cost.
Show less  Date Issued
 1992
 PURL
 http://purl.flvc.org/fcla/dt/14848
 Subject Headings
 Group technologySimulation methods, Manufacturing processesData processing
 Format
 Document (PDF)
 Title
 Selection of manufacturing tolerances for openchain mechanisms.
 Creator
 Kumar, Arun., Florida Atlantic University, Masory, Oren, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Flexible manufacturing systems play an important role in modern industries. The equipment used in flexible manufacturing systems such as industrial robots, NC machines, conveyors etc. demand high performance and accuracies. The selection of manufacturing tolerances is critical in deciding the accuracy of the mechanism and the manufacturing cost. In the present work a new kinematic model for openchain mechanism is proposed which will help the designer in selecting the manufacturing tolerances...
Show moreFlexible manufacturing systems play an important role in modern industries. The equipment used in flexible manufacturing systems such as industrial robots, NC machines, conveyors etc. demand high performance and accuracies. The selection of manufacturing tolerances is critical in deciding the accuracy of the mechanism and the manufacturing cost. In the present work a new kinematic model for openchain mechanism is proposed which will help the designer in selecting the manufacturing tolerances. The model allows the designer to estimate the manufacturing cost for the required accuracy. By using the model and the cost function, a set of tolerances can be estimated to achieve the required accuracy and/or manufacturing cost. The end point location and the manufacturing cost of the mechanism are expressed as a functions of tolerances and major dimensions. By using these expressions one can optimize the tolerances based on (1) optimizing accuracy under the cost constraint, (2) optimizing cost under the accuracy constraint.
Show less  Date Issued
 1992
 PURL
 http://purl.flvc.org/fcla/dt/14814
 Subject Headings
 Tolerance (Engineering), Machinery, Kinematics of
 Format
 Document (PDF)
 Title
 Separation flow around airfoil with upstream disturbance by discrete vortex method.
 Creator
 Li, Feng., Florida Atlantic University, Su, TsungChow, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The discrete vortex method was applied to the calculation of separation flow past NACA 4412 airfoil: Vortex panel was used to represent the body surface and discrete vortices were used to model the wake. Generally the uniform upstream condition is used in the calculation of separation flow. But actually an airfoil could move in wake of other airfoils or disturbed fluid. In this thesis, discrete vortices were used to model the upstream disturbance to investigate the effect of upstream...
Show moreThe discrete vortex method was applied to the calculation of separation flow past NACA 4412 airfoil: Vortex panel was used to represent the body surface and discrete vortices were used to model the wake. Generally the uniform upstream condition is used in the calculation of separation flow. But actually an airfoil could move in wake of other airfoils or disturbed fluid. In this thesis, discrete vortices were used to model the upstream disturbance to investigate the effect of upstream disturbance to the pressure, lift and drag coefficients around the airfoil. Also the animation of separation flow was made on HP workstation using "Starbase" computer graphic package to study the separation process.
Show less  Date Issued
 1991
 PURL
 http://purl.flvc.org/fcla/dt/14739
 Subject Headings
 Vortexmotion, Fluid dynamics
 Format
 Document (PDF)
 Title
 Stability and response of suspension bridges under turbulent wind excitation.
 Creator
 Sternberg, Alex., Florida Atlantic University, Lin, Y. K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This research addresses the linear flutter theory for bridges. A new model for the selfexcited loads is proposed in which oscillatory variation in the loads due to motioninduced vortex activity in the wake, is accounted for. The addition of complex exponential terms generalizes the traditional Prony series representation of the indicial function for the selfexcited loads. Turbulence in the flow direction is included in the selfexcited loads. Hence the system is parametrically excited and...
Show moreThis research addresses the linear flutter theory for bridges. A new model for the selfexcited loads is proposed in which oscillatory variation in the loads due to motioninduced vortex activity in the wake, is accounted for. The addition of complex exponential terms generalizes the traditional Prony series representation of the indicial function for the selfexcited loads. Turbulence in the flow direction is included in the selfexcited loads. Hence the system is parametrically excited and its governing equations have randomly varying coefficients. The state vector of the response is approximated by a Markov vector process. Stochastic averaging is utilized to convert the physical equations into Ito's stochastic differential equations which govern the Markov vector process. Ito's differential rule is then used to construct the equations for the second statistical moments. Motion stability of the system is interpreted as stability of the first and second statistical moments. The computed stability boundaries for the first and second moments are shown to be crucially dependent upon the coupled loads. Unfortunately, parameters for the indicial functions calculated indirectly from the frequencydomain flutter derivatives, are nonunique. Nevertheless, it can be concluded that a bridge deck that exhibits oscillatory selfexcited load behavior is generally less stable (in the mean square) than one with nonoscillatory behavior. The new model that captures the oscillatory behavior concisely, reduces the critical wind speed by more than 10%. Buffeting loads result essentially from the vertical turbulence component. In the present thesis the buffeting loads are expressed as convolution integrals, that account for past history of the fluid flow. Thus the buffeting model considered is based on unsteady aerodynamics rather than the quasisteady model that has been traditionally used in many previous analyses. The time domain unsteady buffeting response analysis, that also incorporates the randomly varying parameters of the selfexcited loads, is the first of its kind. In the illustrative examples, the unsteady buffeting effect is shown to be significant on a singledegreeoffreedom system, whereas it is comparatively less significant with a coupled twodegreeoffreedom system.
Show less  Date Issued
 1988
 PURL
 http://purl.flvc.org/fcla/dt/11921
 Subject Headings
 Suspension bridgesStability, Winds
 Format
 Document (PDF)
 Title
 Stability of an elliptical vortex in a timedependent strain field.
 Creator
 Marshall, Marilyn P., Florida Atlantic University, Dhanak, Manhar R., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

A theoretical study of the stability of twodimensional elliptical vortices in a timedependent, periodically varying external straining flow was conducted. The mean value of the oscillating straining flow was chosen so that the vortex would be stationary in the absence of fluctuations of the external field about the mean. If the frequency of straining is near to the natural frequency of the vortex for smallamplitude oscillations of the vortex core, so that the vortex is forced near its...
Show moreA theoretical study of the stability of twodimensional elliptical vortices in a timedependent, periodically varying external straining flow was conducted. The mean value of the oscillating straining flow was chosen so that the vortex would be stationary in the absence of fluctuations of the external field about the mean. If the frequency of straining is near to the natural frequency of the vortex for smallamplitude oscillations of the vortex core, so that the vortex is forced near its natural frequency, a resonance occurs such that the aspect ratio of the elliptical core boundary initially oscillates with an amplitude that increases linearly with time. After an initial period of growth, the aspect ratio will either follow a bounded limit cycle at large time or it will elongate exponentially with time. The nonlinear evolution of the vortex at large time is studied numerically, and distinct regions of behavior in the parameter space for the vortex are obtained.
Show less  Date Issued
 1992
 PURL
 http://purl.flvc.org/fcla/dt/14817
 Subject Headings
 VortexMotion, Fluid dynamicsMathematical models
 Format
 Document (PDF)
 Title
 Strength and permeability of fly ashmodified concrete in coastal construction.
 Creator
 Murti, Vasu., Florida Atlantic University, Reddy, Dronnadula V., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Three vital factors, namely environmental protection, savings in energy, and technical benefits, make it advantageous to incorporate fly ash of controlled quality and composition in all concrete construction. The specific objective of this research was to compare the performance characteristics of fly ashmodified concrete with that of normal concrete in the coastal environment. To make this comparison, a series of tests using appropriate ASTM standards were conducted. First, the compressive...
Show moreThree vital factors, namely environmental protection, savings in energy, and technical benefits, make it advantageous to incorporate fly ash of controlled quality and composition in all concrete construction. The specific objective of this research was to compare the performance characteristics of fly ashmodified concrete with that of normal concrete in the coastal environment. To make this comparison, a series of tests using appropriate ASTM standards were conducted. First, the compressive strength development of five mixes was studied. Reinforced beam specimens were then subjected to varying periods of accelerated corrosion with sea water as electrolyte. These were tested under flexure and impact. An attempt was made to predict remaining life. Finally, permeability tests were carried out. Results indicate that fly ash increases compressive strength, improves both moment carrying capacity and impact resistance, and increases watertightness.
Show less  Date Issued
 1989
 PURL
 http://purl.flvc.org/fcla/dt/14545
 Subject Headings
 Fly ash, ConcretePermeability
 Format
 Document (PDF)
 Title
 Soilgeosynthetic reinforcement interaction for mechanically stabilized earth (MSE) wall systems.
 Creator
 Navarrete, Fernando Manuel., Florida Atlantic University, Reddy, Dronnadula V., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The dissertation is an experimental and analytical investigation of the long term performance of mechanically stabilized earth (MSE) walls with geosynthetics, with particular focus on rational methods to enable the determination of the applicable factors for use in Load Resistance Factor Design (LRFD). An overview of current issues concerning MSE walls is followed by an extensive literature review addressing MSE walls, pullout strength, creep and creep rupture, durability and degradation,...
Show moreThe dissertation is an experimental and analytical investigation of the long term performance of mechanically stabilized earth (MSE) walls with geosynthetics, with particular focus on rational methods to enable the determination of the applicable factors for use in Load Resistance Factor Design (LRFD). An overview of current issues concerning MSE walls is followed by an extensive literature review addressing MSE walls, pullout strength, creep and creep rupture, durability and degradation, design methodology, analytical prediction, and field evaluation of MSE walls. The experimental tasks comprise: (i) creep and creep rupture, (ii) durability and degradation, (iii) small scale testing of MSE walls with a model prototype ratio of 1:5.5, and (iv) construction of prototype MSE wall and instrumentation for longterm performance. The analytical work comprises finite difference modeling using the Fast Lagrangian Analysis of Continua (FLAC) software, (i) For creep up to 10,000 hours accelerated exposure for HDPE and PET geogrids, with superambient temperatures and soil water conditions related to soil conditions in Florida, the significant part of creep was due to temperatures and not solution exposures, with creep rupture occurring primarily for HDPE. (ii) For durability, performance at ambient temperatures was extrapolated, based on the Arrhenius method. The variation in degradation between the different solutions was minimal, indicating hydrolysis as the main cause for PET at elevated temperatures. (iii) Two HDPE and two PET reinforcement small scale (1:5.5) MSE walls were tested, with different surcharges each for 72 hour periods. Panel movements, strains in the reinforcement, and wall settlements were measured, indicating values smaller than the predicted, mostly for the smaller surcharges due to distortion caused by scaling neglecting the gravity effect. (iv) For analysis with FLAC computer software, two correction factors "a" and "b" were applied to correct the discrepancies between the model and the test values. The PET MSE small scale wall showed more deviation because the material has a low modulus of elasticity. (v) A preliminary comparison of the small scale and the prototype MSE wall behavior indicated discrepancies due to distortion scaling related to the lack of gravity simulation.
Show less  Date Issued
 2001
 PURL
 http://purl.flvc.org/fcla/dt/11968
 Subject Headings
 Geosynthetics, Load factor design, Retaining walls, Soil stabilization
 Format
 Document (PDF)
 Title
 Software development of a hardwareintheloop simulation and a threedimensional viewer for autonomous underwater vehicles.
 Creator
 Mahieu, Frederi., Florida Atlantic University, An, Edgar, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This thesis describes the development of the hardwareintheloop simulation for FAU Autonomous Underwater Vehicles. The development was based on the existing simulation platform. For more efficiency and flexibility, this simulation package was ported to Linux. The hardwareintheloop simulation enables developers to connect the vehicle directly to a remote simulator. This kind of simulation is used to test the actual software components embedded in the vehicle system. The simulation package...
Show moreThis thesis describes the development of the hardwareintheloop simulation for FAU Autonomous Underwater Vehicles. The development was based on the existing simulation platform. For more efficiency and flexibility, this simulation package was ported to Linux. The hardwareintheloop simulation enables developers to connect the vehicle directly to a remote simulator. This kind of simulation is used to test the actual software components embedded in the vehicle system. The simulation package was enhanced by the addition of a 3D viewer. This thesis describes the whole development process, from feasibility study and implementation to qualification phases. This viewer is platform independent and designed to be connected to the simulator. It renders the AUV moving in a virtual environment. This tool can be used during all development steps, from tuning phases to postmission analysis.
Show less  Date Issued
 2000
 PURL
 http://purl.flvc.org/fcla/dt/15778
 Subject Headings
 Oceanographic submersiblesComputer simulation, Computer softwareDevelopment, Simulation methods, Threedimensional display systems
 Format
 Document (PDF)
 Title
 Steel cathodic polarization and calcareous deposit characteristics in deep seawater.
 Creator
 Chen, Shaowei., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Field and laboratory ambient and simulated deep seawater sacrificial anode cathodic protection experiments were performed by coupling steel specimens to AlZnHg anode through an appropriately sized external resistor and thereby permitting a particular level of cathodic protection from freely corroding to overprotection to be simulated. The effects of sea current velocity, surface preparation, initial current density, temperature and hydrostatic pressure upon cathodic polarization and...
Show moreField and laboratory ambient and simulated deep seawater sacrificial anode cathodic protection experiments were performed by coupling steel specimens to AlZnHg anode through an appropriately sized external resistor and thereby permitting a particular level of cathodic protection from freely corroding to overprotection to be simulated. The effects of sea current velocity, surface preparation, initial current density, temperature and hydrostatic pressure upon cathodic polarization and characteristics of calcareous deposits were investigated in the context of slope parameter and steadystate potential and current density trend. The results revealed that a linear relationship between cathode potential and current density is applicable for design of sacrificial anode cathodic protection systems and analysis of cathodic protection survey data from existing structures both in shallow and deep waters. It was also found that for cathodically polarized steel specimens in ambient (shallow) seawater steadystate cathode potential and current density varied according to a sigmoidal trend that indicates the importance of calcareous deposits in such exposures and demonstrated the utility of rapid polarization. On the other hand, no sigmoidal trend was apparent for field and simulated deep water tests; but instead steadystate current density was constant for potential range between 0.80 and 1.05 v (Ag/AgCl). This disclosed that no particular benefit could be derived from employing rapid polarization in cold water exposures. SEM, EDX and Xray diffraction analysis revealed that the calcareous deposits formed upon specimens exposed at 5C and ambient pressure or 8.96 MPa laboratory experiments exhibited two layer structuresan outer layer of CaCO3 as aragonite and inner layer of Mg(OH)2 as brucite. The morphology and coverage of the deposits depended on the design slope parameter (initial current density). Field testing results indicated that deposits were also composed of CaCO3 and Mg(OH)2 where the former was calcite. Because of the poor coverage of the deposits formed in the deep water condition, limited current density reduction was noted. These results suggest that a different cp design approach and strategy should be considered for deep, cold seawater compared to that commonly used in shallow water environments.
Show less  Date Issued
 1996
 PURL
 http://purl.flvc.org/fcla/dt/12457
 Subject Headings
 Seawater corrosion, Cathodic protection, SteelCorrosion
 Format
 Document (PDF)
 Title
 Stochastic earthquake ground motion modeling.
 Creator
 Zhang, Ruichong., Florida Atlantic University, Lin, Y. K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

A model for earthquake ground motion is developed in this dissertation using principles of geophysics and stochastics. The earth is idealized as being composed of horizontally stratified layers, with uniform physical properties for each layer. The seismic source is assumed to be the result of shear dislocation propagating on a fault line, which is further discretized into a series of point sources at equal intervals. The fundamental problem of the ground motion in a layered medium due to a...
Show moreA model for earthquake ground motion is developed in this dissertation using principles of geophysics and stochastics. The earth is idealized as being composed of horizontally stratified layers, with uniform physical properties for each layer. The seismic source is assumed to be the result of shear dislocation propagating on a fault line, which is further discretized into a series of point sources at equal intervals. The fundamental problem of the ground motion in a layered medium due to a point source at a given source location is first considered. The governing equations of threedimensional wave motion in a uniform layer are presented and solved in both Cartesian and cylindrical coordinates. Wave propagation in a multilayered medium is then analyzed in detail, in which the wave scattering matrices are introduced so that stability and accuracy in numerical calculation can be guaranteed. A detailed review of the mechanism of seismic point source is also provided. Based on the fundamental solution for a point source, an earthquake model is constructed by superposing the solutions associated with a series of point sources along a line which are activated sequentially at random times. Statistical characteristics of earthquake ground motion is then obtained by applying a generalized version of the randompulsetrain theory and its evolutionary spectral representation. Finally the effects of uneven interface on the earthquake ground motion is also analyzed using a firstorder perturbation approach.
Show less  Date Issued
 1992
 PURL
 http://purl.flvc.org/fcla/dt/12290
 Subject Headings
 Earth movements, Earthquakes, Stochastic processes
 Format
 Document (PDF)
 Title
 Simulation, control and optimization of underwater vehicle performance.
 Creator
 Zipf, David Glenn., Florida Atlantic University, Dunn, Stanley E., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This project addresses the simulation, control and optimization of underwater vehicle performance. An analytical model of underwater vehicle motion has been developed. This model is based on a set of six degree of freedom nonlinear differential equations of motion. These equations incorporate inertial, hydrodynamic, hydrostatic, gravity and thruster forces to define the vehicle's motion. The forces are calculated and the equations of motion solved using a finite difference method of...
Show moreThis project addresses the simulation, control and optimization of underwater vehicle performance. An analytical model of underwater vehicle motion has been developed. This model is based on a set of six degree of freedom nonlinear differential equations of motion. These equations incorporate inertial, hydrodynamic, hydrostatic, gravity and thruster forces to define the vehicle's motion. The forces are calculated and the equations of motion solved using a finite difference method of integration. An automatic closed loop control strategy has been developed and integrated into the motion model. The controller determines control plane deflection and thruster output based on sensor provided input, maneuver request and control gain constants. The motion model simulates the effects of these controller requests on the vehicle motion. The controller effects are analyzed and an optimal set of control gains is determined. These optimal gains are determined based on a quantitative comparison of a predefined Performance Index (PI) function. The PI is a function of critical performance values, i.e., energy consumption, and user defined weighted constants. By employing an iteration technique the PI is minimized to provide an optimal set of control gains.
Show less  Date Issued
 1989
 PURL
 http://purl.flvc.org/fcla/dt/14534
 Subject Headings
 Oceanographic submersiblesAutomatic control, Oceanographic submersiblesSimulation methods, Vehicles, Remotely piloted
 Format
 Document (PDF)
 Title
 Simulation of reflection tomographic images of underwater targets with the effect of vehicle motion sensing errors.
 Creator
 Quentin, Gwendoline., Florida Atlantic University, Schock, Steven G., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The Buried Object Scanning Sonar (BOSS) is being developed at Florida Atlantic University to image targets buried under the seabed. Tomographic images are constructed using a sequence of sonar transmissions while the vehicle is moving. This motion causes image distortion and should be measured and removed by mapping the echoes received to an absolute coordinate system. The aim of this thesis is to develop and simulate a technique for generating BOSS images that provide an accurate...
Show moreThe Buried Object Scanning Sonar (BOSS) is being developed at Florida Atlantic University to image targets buried under the seabed. Tomographic images are constructed using a sequence of sonar transmissions while the vehicle is moving. This motion causes image distortion and should be measured and removed by mapping the echoes received to an absolute coordinate system. The aim of this thesis is to develop and simulate a technique for generating BOSS images that provide an accurate representation of target shape and size, by removing vehicle motion while mapping the image pixels. Synthetic acoustic data sets are generated by convolving the autocorrelated FM transmission pulse with the impulse response of an elastic sphere. Synthetic outputs of a Doppler velocity log and a 3axis inertial measurement unit are generated to simulate vehicle motion. Noise is added to the sensor data to show the effects of motion sensor errors on image quality.
Show less  Date Issued
 2003
 PURL
 http://purl.flvc.org/fcla/dt/13040
 Subject Headings
 Ocean tomography, Sonar, Underwater navigation
 Format
 Document (PDF)