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Title: HYDRODYNAMIC LOADS ON OFFSHORE STRUCTURES DURING SUBSEA BLOWOUTS.
Creator: RAJIV, PAKANATI V. S., Florida Atlantic University, Su, Tsung-Chow, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The plume resulting from a subsea well blowout alters the environmental loading on a floating platform which is directly above the well. Horizontal ocean currents deflect the plume and may create a more severe loading on the structure. During the early stages of a blowout the "starting plume" induces forces of a different magnitude on the structure. A preliminary experimental study, investigating the transient loads induced by starting plumes and the effects of currents on blowout plumes, was...
Show moreThe plume resulting from a subsea well blowout alters the environmental loading on a floating platform which is directly above the well. Horizontal ocean currents deflect the plume and may create a more severe loading on the structure. During the early stages of a blowout the "starting plume" induces forces of a different magnitude on the structure. A preliminary experimental study, investigating the transient loads induced by starting plumes and the effects of currents on blowout plumes, was conducted. The results of the experiments showed that the forces involve significant fluctuations which are quite different from the average values. The normal forces induced by starting plumes were slightly greater. Horizontal currents caused an increase in the moment acting on the structure. This is of considerable importance as moments, when coupled with the situation of flooded decks and compartments, may cause the structure to sink.
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Date Issued: 1985
PURL: http://purl.flvc.org/fcla/dt/14267
Subject Headings: Offshore structures--Hydrodynamics--Experiments
Format: Document (PDF)

Title: Characterization of steel cathodic polarization in seawater and its applications in offshore structure cathodic protection design.
Creator: Wang, Weiqing., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Laboratory experiments have been performed to characterize the effects of initial current density and selected variables (initial current density, temperature and surface treatment) upon the cathodic polarization behavior of API 2H Grade 42 steel in natural sea water. The procedure involved galvanic coupling of a cylindrical steel specimen to a larger diameter aluminum sacrificial anode ring through an external resistor, which offset the otherwise impractically small anode/cathode surface...
Show moreLaboratory experiments have been performed to characterize the effects of initial current density and selected variables (initial current density, temperature and surface treatment) upon the cathodic polarization behavior of API 2H Grade 42 steel in natural sea water. The procedure involved galvanic coupling of a cylindrical steel specimen to a larger diameter aluminum sacrificial anode ring through an external resistor, which offset the otherwise impractically small anode/cathode surface area ratio and permitted the desired initial current density to be realized. In the initial polarization stage the change in potential versus current density data with time was found to be linear with a slope equal to the product of the total circuit resistance and cathode surface area and with the vertical intercept corresponding to the anode open circuit potential. Lower temperature or increased flow resulted in reduced polarization and a relatively high current density, but data for experiments employing a particular resistance conformed to straight lines with the same slope R[ext] x A[c] (external resistance times cathode surface area). Some experiments exhibited concave behavior at longer test duration. An explanation for the linear interdependence of potential and current density and the following concave behavior is presented. The laboratory experiments were compared with offshore structure survey results. It is projected that the potential-current density behavior of galvanic cathodic protection (CP) systems of different geometries can be quantitatively interrelated through this slope parameter. Implications of the data are discussed within the context of cathodic protection design, rapid polarization and system performance for offshore structures.
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Date Issued: 1994
PURL: http://purl.flvc.org/fcla/dt/12362
Subject Headings: Steel--Cathodic protection, Seawater, Offshore structures
Format: Document (PDF)

Title: A critical evaluation of current demand determination methods for cathodic protection retrofits of offshore structures.
Creator: Lemieux, Edward John., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Development of a baseline design protocol for cathodic protection retrofits of offshore structures is becoming an increasingly important topic in light of the large number of structures operating beyond their original cp system design life. One of the critical steps in this development is determination of the total anode mass which is required to continue sufficient cathodic protection for which structure current demand must be established. Three current demand determination methods were...
Show moreDevelopment of a baseline design protocol for cathodic protection retrofits of offshore structures is becoming an increasingly important topic in light of the large number of structures operating beyond their original cp system design life. One of the critical steps in this development is determination of the total anode mass which is required to continue sufficient cathodic protection for which structure current demand must be established. Three current demand determination methods were investigated including the Gaussian ammeter, the Potential method, which utilizes the driving potential and anode resistance in its current calculation, and the IR Drop method. To this end, three anodes were deployed at the Naval Research Laboratory, Key West, Fl., and current output determinations were made upon these. Each of the three current measurement methods was evaluated on the basis of accuracy, reliability and feasibility in field use.
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Date Issued: 1997
PURL: http://purl.flvc.org/fcla/dt/15503
Subject Headings: Cathodic protection, Offshore structures, Ocean currents
Format: Document (PDF)

Title: Finite element analysis to study the structural behavior of an underwater acoustic tower.
Creator: Sambandam, Sundaresakumar., Florida Atlantic University, Case, Robert O., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis deals with the static analysis of a three dimensional underwater acoustic tower exclusively designed and fabricated by Harbor Branch Oceanographic Institution, Ft. Pierce, Florida. A commercial finite element package COSMOS/M was used for the finite element analysis. The structural modeling as well as processing of the results was performed using GEOSTAR Ver. 1.65 interactive graphics package. The analysis was concentrated on the main instrument pipe carrying the required...
Show moreThis thesis deals with the static analysis of a three dimensional underwater acoustic tower exclusively designed and fabricated by Harbor Branch Oceanographic Institution, Ft. Pierce, Florida. A commercial finite element package COSMOS/M was used for the finite element analysis. The structural modeling as well as processing of the results was performed using GEOSTAR Ver. 1.65 interactive graphics package. The analysis was concentrated on the main instrument pipe carrying the required instruments for data acquisition. Various environmental loading induced by ocean currents, hydrostatic pressure, buoyancy and self weight of the tower have been considered in the analysis. The construction aspects of the tower as well as the finite element analysis of tower substructures are also discussed. The deflection of the tower due to the imposed loading is studied and deflection profiles are drawn.
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Date Issued: 1992
PURL: http://purl.flvc.org/fcla/dt/14846
Subject Headings: Finite element method, Offshore structures, underwater acoustics--Data processing
Format: Document (PDF)

Title: A STRESS CONCENTRATION ANALYSIS OF SELECTED WELDS FROM FATIGUE SPECIMENS USING THE FINITE-ELEMENT METHOD.
Creator: NEROLICH, SHAUN MICHAEL., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The stress concentration which exists at the toe of an AWS class 'c' weld has been investigated by means of the finite element method. This type of weld is representative of that specified to join tubular members for offshore structures. Welded fatigue specimens were sectioned and the weld profile described in terms of 1) the weld toe radius (R), 2) the reinforcement angle (e) and 3) the filler metal height QH). A statistical analysis was performed to determine the correlation between R, e...
Show moreThe stress concentration which exists at the toe of an AWS class 'c' weld has been investigated by means of the finite element method. This type of weld is representative of that specified to join tubular members for offshore structures. Welded fatigue specimens were sectioned and the weld profile described in terms of 1) the weld toe radius (R), 2) the reinforcement angle (e) and 3) the filler metal height QH). A statistical analysis was performed to determine the correlation between R, e and H from which it was found that they are independent of each other. By use of the finite element method, trends were established for the effect each parameter has on the stress concentration at the weld toe. Analysis of the effect of undercutting was also perfonned and the results used to offer an explanation why fatigue cracks propagate to failure in some cases and arrest in others.
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Date Issued: 1981
PURL: http://purl.flvc.org/fcla/dt/14069
Subject Headings: Offshore structures--Welding, Welded joints--Fatigue
Format: Document (PDF)

Title: Dynamic positioning and motion mitigation of a scaled sea basing platform.
Creator: Marikle, Sean P., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A 6-Degree Of Freedom (DOF) numeric model and computer simulation along with the 1/10th scale physical model of the Rapidly Deployable Stable Platform (RDSP) are being developed at Florida Atlantic University in response to military needs for ocean platforms with improved sea keeping characteristics. The RDSP is a self deployable spar platform with two distinct modes of operation enabling long distance transit and superior seakeeping. The focus of this research is the development of a Dynamic...
Show moreA 6-Degree Of Freedom (DOF) numeric model and computer simulation along with the 1/10th scale physical model of the Rapidly Deployable Stable Platform (RDSP) are being developed at Florida Atlantic University in response to military needs for ocean platforms with improved sea keeping characteristics. The RDSP is a self deployable spar platform with two distinct modes of operation enabling long distance transit and superior seakeeping. The focus of this research is the development of a Dynamic Position (DP) and motion mitigation system for the RDSP. This will be accomplished though the validation of the mathematical simulation, development of a novel propulsion system, and implementation of a PID controller. The result of this research is an assessment of the response characteristics of the RDSP that quantifies the performance of the propulsion system coupled with active control providing a solid basis for further controller development and operational testing.
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Date Issued: 2009
PURL: http://purl.flvc.org/FAU/228767
Subject Headings: Inertial navigation systems, Mobile offshore structures, Design and construction, Wave motion, Theory of, Offshore structures, Dynamics, Feedback control systems
Format: Document (PDF)

Title: Spectrum fatigue of welded structural steel in sea water.
Creator: Clark, A. M., Qian, D., Hartt, William H., Martin, P. E., Czarnecki, M. F., Harbor Branch Oceanographic Institute
Date Issued: 1983
PURL: http://purl.flvc.org/fau/fd/FA00007432
Subject Headings: Offshore structures--Welded joints--Fatigue, Steel, Structural--Fatigue, Seawater
Format: Document (PDF)

Title: Model analysis of a mooring system for an ocean current turbine testing platform.
Creator: Cribbs, Allison Rose., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: In response to Florida's growing energy needs and drive to develop renewable power, Florida Atlantic Universitys Center for Ocean Energy Technology (COET) plans to moor a 20 kW test turbine in the Florida Current. No permanent mooring systems for deepwater hydrokinetic turbines have been constructed and deployed, therefore little if anything is known about the performance of these moorings. To investigate this proposed mooring system, a numeric model is developed and then used to predict the...
Show moreIn response to Florida's growing energy needs and drive to develop renewable power, Florida Atlantic Universitys Center for Ocean Energy Technology (COET) plans to moor a 20 kW test turbine in the Florida Current. No permanent mooring systems for deepwater hydrokinetic turbines have been constructed and deployed, therefore little if anything is known about the performance of these moorings. To investigate this proposed mooring system, a numeric model is developed and then used to predict the static and dynamic behavior of the mooring system and attachments. The model has been created in OrcaFlex and includes two surface buoys and an operating turbine. Anchor chain at the end of the mooring line develops a catenary, providing compliance. Wind, wave, and current models are used to represent the environmental conditions the system is expected to experience and model the dynamic effects on the system. The model is then used to analyze various components of the system. The results identify that a mooring attachment point 1.25 m forward of the center of gravity on the mooring buoy is ideal, and that the OCDP and turbine tether lengths should be no shorter than 25 and 44 m, respectively. Analysis performed for the full system identify that the addition of the floats decreases the tension at the MTB attachment location by 26.5 to 29.5% for minimum current, and 0.10 to 0.31% for maximum current conditions.
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Date Issued: 2010
PURL: http://purl.flvc.org/FAU/2974432
Subject Headings: Marine turbines, Mathematical models, Structural dynamics, Rotors, Design and construction, Offshore structures, Testing
Format: Document (PDF)

Title: Test platform development for measuring surface effect ship response to wave loads.
Creator: Kouvaras, Nicholas, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The goal of this thesis is to develop a test platform for measuring surface effect ship (SES) response to wave loads. The platform is designed and built incorporating a self-propelled vehicle with data acquisition and navigation capabilities. Theoretical analysis is performed, various hardware and electronic parts are designed and built and software applications developed. Wave tank experiments are conducted for test platform evaluation and determination of vehicle response to a range of wave...
Show moreThe goal of this thesis is to develop a test platform for measuring surface effect ship (SES) response to wave loads. The platform is designed and built incorporating a self-propelled vehicle with data acquisition and navigation capabilities. Theoretical analysis is performed, various hardware and electronic parts are designed and built and software applications developed. Wave tank experiments are conducted for test platform evaluation and determination of vehicle response to a range of wave conditions. Furthermore, a three-dimensional model of the AIRCAT scale model SES is created. The theoretical analysis shows that the scale effects in some cases are great, so resonance phenomena cannot be observed. The experimental results clearly show that the heave, pitch and aircushion excess pressure fluctuations increase as the air-blower input level increases. The bow skirt arrangement needs improvements and further experimentation is necessary in order to draw conclusions about the wave loads applied on the skirt.
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Date Issued: 2010
PURL: http://purl.flvc.org/FAU/1927307
Subject Headings: Mobile offshore structures, Design and construction, Wave motion, Theory of, Inertial navigation systems, Oceanographic instruments, Evaluation
Format: Document (PDF)

Title: Cathodic polarization response of simulated prestressed concrete piles exposed to natural sea water.
Creator: Chaix, Olivier., Florida Atlantic University, Hartt, William H.
Abstract/Description: Experiments were conducted to determine the effectiveness of localized cathodic polarization for reducing corrosion of simulated prestressed concrete piles containing admixed calcium chloride and exposed to a simulated sea water tidal cycle. The specimens contained both continuous and segmented steel tendons, the purpose of the latter being to facilitate measurement of cathodic protection current. Conductive rubber in an impressed current system was used as the anode material. The specimens...
Show moreExperiments were conducted to determine the effectiveness of localized cathodic polarization for reducing corrosion of simulated prestressed concrete piles containing admixed calcium chloride and exposed to a simulated sea water tidal cycle. The specimens contained both continuous and segmented steel tendons, the purpose of the latter being to facilitate measurement of cathodic protection current. Conductive rubber in an impressed current system was used as the anode material. The specimens were initially freely corroded and then cathodically polarized at a constant current ranging from 0.5 to 1 mA/m$\sp2$ which corresponded to potentials (current-on) which ranged from $-$0.500 to $-$1.100 V(sce) in the anode region. The magnitude of impressed current and its distribution along the embedded steel was monitored as a function of exposure time, level of polarization and water levels. Current-on and instant-off potential distribution for both the continuous and segmented tendons were also measured. The level of cathodic polarization was assessed as a function of position along the specimens by the depolarization method. The results were evaluated within the context of marine bridge substructure cathodic protection technology.
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Date Issued: 1992
PURL: http://purl.flvc.org/fcla/dt/14865
Subject Headings: Corrosion and anti-corrosives, Sea-water corrosion, Offshore structures, Reinforced concrete--Deterioration
Format: Document (PDF)

Title: Effect of cathodic protection and cyclic frequency on corrosion fatigue of selected high strength steels in seawater.
Creator: Badve, Ashwin P., Florida Atlantic University, Hartt, William H.
Abstract/Description: Study of selected candidate steels for offshore application was undertaken to observe the effects of cathodic protection and cyclic frequency on corrosion fatigue life. Keyhole Compact Tension Fatigue experiments under constant amplitude sinusoidal loading and stress ratio of 0.5 were performed on 25.4 mm thick specimens in natural sea water and also in air upon three different steels (Y.S. 500-563 MPa). These steels represented different strengthening techniques, namely precipitation...
Show moreStudy of selected candidate steels for offshore application was undertaken to observe the effects of cathodic protection and cyclic frequency on corrosion fatigue life. Keyhole Compact Tension Fatigue experiments under constant amplitude sinusoidal loading and stress ratio of 0.5 were performed on 25.4 mm thick specimens in natural sea water and also in air upon three different steels (Y.S. 500-563 MPa). These steels represented different strengthening techniques, namely precipitation hardening, direct quenching--a thermomechanical control process (TMCP), and controlled rolling. Cathodic polarization was in the range between freely corroding and -1.10 Volts (SCE). The tests were performed at a frequency of 0.3 and 1.0 Hz. The results are presented in the S-N and potential versus cycles to initiation format. No effect of frequency (1.0-0.3 Hz) was observed at cathodic protection of -1.10 V (SCE). The steels showed an increase in fatigue life to an optimum potential, and excessive potentials were detrimental. The fatigue life in dry air was greater than in laboratory air (~50% RH).
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Date Issued: 1989
PURL: http://purl.flvc.org/fcla/dt/14494
Subject Headings: Marine steel--Fatigue, Offshore structures, Sea-water corrosion, Corrosion and anti-corrosives
Format: Document (PDF)

Title: Finite element analysis of the visco-elastic behavior of a spray ice island.
Creator: Thiel, David Ted., Florida Atlantic University, Reddy, Dronnadula V., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis presents a finite element analysis of the viscoelastic (creep) behavior of a spray ice island under its own self-weight and three levels of lateral loads. Spray ice and its use as a construction material are described in the context of other natural ice forms and the ice environment of the Beaufort Sea. The analytical results indicated that creep settlement in the absence of volumetric contraction was nominal over the course of a simulated 21-day construction period and a 79-day...
Show moreThis thesis presents a finite element analysis of the viscoelastic (creep) behavior of a spray ice island under its own self-weight and three levels of lateral loads. Spray ice and its use as a construction material are described in the context of other natural ice forms and the ice environment of the Beaufort Sea. The analytical results indicated that creep settlement in the absence of volumetric contraction was nominal over the course of a simulated 21-day construction period and a 79-day service life. The effects of the applied lateral loads were very localized and did not result in any appreciable deformations in the central working area of the structure. Some evidence of shear plane development and upward passive failure of the island perimeter was observed.
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Date Issued: 1990
PURL: http://purl.flvc.org/fcla/dt/14647
Subject Headings: Ice mechanics, Offshore structures--Dynamics, Sea ice--Beaufort Sea
Format: Document (PDF)

Title: Modeling and control of a vertically tethered marine platform using an active heave compensation system.
Creator: Eide, Linn., Florida Atlantic University, Driscoll, Frederick R.
Abstract/Description: Technology movement toward deeper waters necessitates the control of vertically tethered systems that are used for installing, repairing, and maintaining underwater equipment. This has become an essential ingredient for the future success of the oil industry as the near-shore oil reservoirs are nearly depleted. Increased operation depths cause large oscillations and snap loadings in these longer cables. Research on this topic has been limited, and includes only top feedback control. The...
Show moreTechnology movement toward deeper waters necessitates the control of vertically tethered systems that are used for installing, repairing, and maintaining underwater equipment. This has become an essential ingredient for the future success of the oil industry as the near-shore oil reservoirs are nearly depleted. Increased operation depths cause large oscillations and snap loadings in these longer cables. Research on this topic has been limited, and includes only top feedback control. The controllers developed in this thesis utilize top, bottom and combined top and bottom feedback. They are implemented on a discrete finite element lumped mass cable model. Comparison between PID, LQG and H infinity for all feedback combinations reveal that the Hinfinity controller with both top and bottom feedback has the best performance, while LQG has a more consistent and reliable performance for all feedback cases.
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Date Issued: 2003
PURL: http://purl.flvc.org/fcla/dt/13079
Subject Headings: Cables, Submarine--Mathematical models, Offshore structures--Dynamics, Feedback control systems, Ships--Hydrodynamics
Format: Document (PDF)

FAU Theses and Dissertations (12)	+ -
HBOI Faculty Contributions (1)	+ -

Offshore structures (7)	+ -
Design and construction (3)	+ -
Corrosion and anti-corrosives (2)	+ -
Feedback control systems (2)	+ -
Inertial navigation systems (2)	+ -

Mobile offshore structures (2)	+ -
Offshore structures--Dynamics (2)	+ -
Sea-water corrosion (2)	+ -
Seawater (2)	+ -
Wave motion, Theory of (2)	+ -
Cables, Submarine--Mathematical models (1)	+ -
Cathodic protection (1)	+ -
Dynamics (1)	+ -
Evaluation (1)	+ -
Finite element method (1)	+ -
Ice mechanics (1)	+ -
Marine steel--Fatigue (1)	+ -
Marine turbines (1)	+ -
Mathematical models (1)	+ -
Ocean currents (1)	+ -
Oceanographic instruments (1)	+ -
Offshore structures--Hydrodynamics--Experiments (1)	+ -
Offshore structures--Welded joints--Fatigue (1)	+ -
Offshore structures--Welding (1)	+ -
Reinforced concrete--Deterioration (1)	+ -
Rotors (1)	+ -
Sea ice--Beaufort Sea (1)	+ -
Ships--Hydrodynamics (1)	+ -
Steel, Structural--Fatigue (1)	+ -
Steel--Cathodic protection (1)	+ -

Electronic Thesis or Dissertation (12)	+ -
article (1)	+ -

College of Engineering and Computer Science (9)	+ -
Department of Ocean and Mechanical Engineering (9)	+ -
Florida Atlantic University (9)	+ -
Hartt, William H. (6)	+ -
Badve, Ashwin P. (1)	+ -

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