The effects of seawater on the integrity of offshore structures

1978 ◽  
Vol 76 (1-3) ◽  
pp. 95-114
Author(s):  
T. Hodgkiess
Keyword(s):  
Corrosion Fatigue ◽  
Concrete Structures ◽  
Steel Structures ◽  
Offshore Structures ◽  
Internal Environment ◽  
The North ◽  
Recent Developments ◽  
The North Sea ◽  
Corrosion Mechanisms ◽  
Basic Features

SynopsisThis paper reviews the knowledge of deterioration processes which occur when steel and concrete structures are situated in seawater. The basic corrosion mechanisms of steel, together with possible methods of protection, are outlined briefly. With regard to coatings and cathodic protection, recent developments to counteract the increasingly severe conditions encountered by oil-production platforms in the North Sea, are discussed. Concrete structures usually provide a naturally-inhibitive internal environment to confer protection from corrosion to encased steel reinforcements, but mention is made of the possibilities of such protection becoming ineffective during long service in severe offshore conditions.The basic features of corrosion fatigue are described in the light of recent research but some aspects, which are of great importance for the performance of steel structures, are shown to be not well documented or understood. Corrosion fatigue of concrete structures has not been studied extensively, a particularly neglected area being the elucidation of the fundamental mechanisms of deterioration.

scholarly journals Connectivity of larval stages of sedentary marine communities between hard substrates and offshore structures in the North Sea

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Johan van der Molen ◽  
Luz María García-García ◽  
Paul Whomersley ◽  
Alexander Callaway ◽  
Paulette E. Posen ◽  
...  
Keyword(s):  
North Sea ◽  
Offshore Structures ◽  
Marine Communities ◽  
Larval Stages ◽  
The North ◽  
The North Sea ◽  
Hard Substrates

scholarly journals DESIGN, ANALYSIS AND FIELD TEST OF A DYNAMIC FLOATING BREAKWATER

1976 ◽  
Vol 1 (15) ◽  
pp. 159 ◽  
Author(s):  
D.J. Agerton ◽  
G.H. Savage ◽  
K.C. Stotz
Keyword(s):  
Solid Wall ◽  
Offshore Structures ◽  
The Past ◽  
The North ◽  
Production Platform ◽  
Floating Breakwater ◽  
The North Sea ◽  
Floating Breakwaters ◽  
Offshore Oil ◽  
Permanent Wave

Interest in floating breakwaters has been generated in recent years because the concept offers the potential of providing a less expensive alternative to traditional, solid wall type barriers for providing permanent wave protection to the thousands of new recreational boat harbors and marinas that have been built in the past 20 years. Also, they may be able to provide temporary, mobile wave protection during construction and installation of offshore facilities for oil transfer and production operations, defense facilities and other offshore structures in deeper water (depths exceeding 50 to 100 feet). The engineering director of one of the largest and most active offshore oil producing companies recently stated that they would be willing to pay up to $6 million for a mobile, floating breakwater that had the proven capability to significantly reduce risks due to wave action during offshore erection in the North Sea or elsewhere. Considering the investment in just one deep water oil production platform already exceeds $100,000,000, the worth of such a reusable, wave protection system during the critical erection period of a platform should be large.

Emergency Towing: Field Exercises and Simulator-Based Training

2008 ◽  
Author(s):  
Tor E. Berg ◽  
Gunnar Gudmundset ◽  
Ulf Klevstad
Keyword(s):  
Emergency Response ◽  
North Sea ◽  
Offshore Structures ◽  
Coastal Environment ◽  
Traffic Density ◽  
Functional Requirements ◽  
Northern Norway ◽  
The North ◽  
Different Types ◽  
The North Sea

Recently there have been a number of incidents involving drifting ships and offshore structures in the North Sea. Increasing traffic density combined with harsher weather and less experienced crews has led the Norwegian Coastal Administration to focus on improving the skills of personnel on board emergency response vessels operating off the coast of Northern Norway. This is order to reduce the consequences of incidents with disabled vessels sailing in the vulnerable coastal environment of the Norwegian and Barents Seas. In addition to field exercises involving dedicated Norwegian emergency response vessels and different types of vessels made available by shipping companies, training takes place on full mission bridge simulators. As part of an ongoing R&D project, MARINTEK and SMS invite stakeholders to participate in short workshops on topics related to the specification of functional requirements for emergency towing vessels and the sharing of experience from recent emergency towing operations.

scholarly journals Wave current interaction: Effect on force prediction for fixed offshore structures

2018 ◽  
Vol 203 ◽  
pp. 01011
Author(s):  
Mohamed Latheef ◽  
Nasir Abdulla ◽  
Mohd Faieez Mohd Jupri
Keyword(s):  
Vertical Structure ◽  
Offshore Structures ◽  
Base Shear ◽  
Sea State ◽  
Clear Trend ◽  
The North ◽  
Relative Water ◽  
The North Sea ◽  
Current Interaction ◽  
Typical Design

MetOcean conditions in the South China Sea (SCS) indicates that unlike other locations such as the North Sea, the magnitude of the currents can be relatively large. In addition, these currents are strongly sheared. The present study focused on the typical design problem of calculating the ultimate base shear and overturning moments for slender fixed structureswiththe inclusion of the interaction between the currents and the wave field. It has been found that the loads on average can be around 15% larger when this interaction is accounted for in the calculation of the loads, highlighting the importance. In addition, the level of these amplifications were found to be dependent on the sea state steepness and the relative water depth. While no clear trend was found (changed case by case) in the present work, incorporating the vertical structure of the current was found to change the pattern of the amplification of the loads.

Selection and Evaluation of High-Strength Steel for Hutton TLP Tension Leg Elements

1984 ◽  
Vol 106 (1) ◽  
pp. 32-37 ◽  
Author(s):  
M. M. Salama ◽  
J. H. Tetlow
Keyword(s):  
Corrosion Fatigue ◽  
High Strength Steel ◽  
Fatigue Behavior ◽  
High Strength ◽  
Mooring System ◽  
Test Program ◽  
The North ◽  
Extensive Evaluation ◽  
The North Sea ◽  
Control Procedures

The development of the tension leg platform (TLP) for the Hutton Field in the North Sea represents the first application of this deepwater concept. The use of vertical tension legs as the mooring system is the most novel part of the TLP design. One of the unique features of the tension legs is the use of 92.5-mm (3.64-in.) thick tubulars forged from 3 1/2 percent Ni-Cr-Mo-V high-strength steel (795 MPa (115.3 ksi) minimum yield strength) as mooring elements. Because of the importance of these elements to the survival of the TLP, the chemical composition and the steelmaking procedure were critically examined and optimized. In addition, extensive evaluation of the corrosion fatigue behavior of the steel was undertaken. This paper discusses the basis for the steel selection and specification, the results of the rigorous corrosion fatigue test program, and the assessment of the variation of properties along the length and through the thickness of full-size components. These results illustrate the suitability of the proposed high-strength steel for the mooring system application and establish confidence in both steelmaking and quality control procedures.

scholarly journals Reliability Updating of Offshore Structures Subjected to Marine Growth

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 414
Author(s):  
Franck Schoefs ◽  
Thanh-Binh Tran
Keyword(s):  
Limit State ◽  
Dynamic Bayesian Network ◽  
Offshore Structures ◽  
Drag Forces ◽  
The North ◽  
The North Sea ◽  
Inspection And Maintenance ◽  
Inspection Data ◽  
Atlantic Area

Marine growth is a known problem for oceanic infrastructure and has been shown to negatively impact the reliability of bottom-fixed or floating offshore structures submitted to fatigue or extreme loading. Among other effects, it has been shown to change drag forces by increasing member diameters and modifying the roughness. Bio-colonization being highly random, the objective of this paper is to show how one-site inspection data increases reliability by decreasing uncertainties. This can be introduced in a reliability-based inspection framework for optimizing inspection and maintenance (here, cleaning). The modeling and computation are illustrated through the reliability analysis of a monopile in the European Atlantic area subjected to marine growth and according to the plastic collapse limit state. Based on surveys of structures in the North Sea, long-term stochastic modeling (space and time) of the marine growth thickness is first suggested. A Dynamic Bayesian Network is then developed for reliability updating from the inspection data. Finally, several realistic (10–20 measurements) inspection strategies are compared in terms of reliability improvement and the accuracy of reliability assessment.

Study of ISO 19901-3 Building Code Correspondence Factor for Eurocode 3

2013 ◽  
Author(s):  
Nicolas Neumann
Keyword(s):  
Cross Sections ◽  
Steel Structures ◽  
Building Code ◽  
Structural Components ◽  
The North ◽  
A Value ◽  
Eurocode 3 ◽  
European Code ◽  
The North Sea ◽  
Design Resistance

For topside structures ISO 19901-3 rely on national or regional building codes to derive the resistance of structural components. It is, however, required that the design resistance(s) of the building code is matched to the design resistance(s) of ISO 19902 through the use of a building code correspondence factor Kc. Recently, Kc was proposed in the literature to be taken as 0.95 for the European code for steel structures, Eurocode 3 (EN 1993). The present study does not support this value. Instead a value of 0.86 is derived. This lower value is based on the investigation of a topside project in the North Sea, and intends to cover for the stricter requirements to component resistance in ISO 19902 compared to Eurocode 3 for plastic and compact cross-sections.

Improving Corrosion Performance of Thermal Sprayed Coatings with a Zn-Mg-Al Alloy

2019 ◽  
Author(s):  
Christiane Schulz ◽  
Frank Goodwin
Keyword(s):  
Sea Water ◽  
Steel Structures ◽  
Deposition Efficiency ◽  
Product Layer ◽  
Al Alloy ◽  
Spray Process ◽  
The North ◽  
Corrosion Reaction ◽  
The North Sea ◽  
Sprayed Coating

<p>Thermal sprayed zinc and aluminum alloy coatings provide corrosion protection to steel structures. A new thermal sprayed coating with 1-2% of each Al and Mg shows up to 3 times the corrosion resistance of the conventional Zn and ZnAl alloy coatings. Arc sprayed Zn-Mg-Al alloy wire and three reference materials, Zn, Zn-15%Al and Al-5%Mg, gave coatings 100 - 150 µm thick, using either compressed air or nitrogen as an atomizing gas. Formation of splats in the arc wire spray process is dependent on wire chemistry, temperature and size of the particle prior to impact on the substrate. Splat appearance can be correlations with deposition efficiency of the different materials. Corrosion testing was carried out using electrochemical polarization in artificial sea water and by long-term exposure for two years on Heligoland Island in the North Sea. Of the investigated Zn-based materials, ZnMgAl forms the most stable corrosion product layer which delays the anodic corrosion reaction. At the same time ZnMgAl provides sacrificial protection of damaged, uncoated areas of up to 5 mm. Although Al-based coatings, like AlMg5, provide cathodic protection to steel, they suffer from pitting corrosion which can lead - when undiscovered - to sudden catastrophic failure of the structure.</p>

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