Offshore General Introduction Analysis
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Previous | Next | Next | Contents ESDEP WG 15A STRUCTURAL STRUCT URAL SYSTEMS: OFFSHORE
Lecture 15A.1: Offshore Structures: General Introduction OBJECTIVE/SCOPE
To identify the basic vocabulary, to introduce the major concepts for offshore platform structures, and to explain where the basic structural requirements for design are generated. PREREQUISITES
None. SUMMARY
The lecture starts with a presentation of the importance of offshore hydro-carbon exploitation, the basic steps in the development process (from seismic exploration to platform removal) and the introduction of the major structural concepts (jacket-based, GBS-based, TLP, floating). The major codes are identified. For the fixed platform concepts (jacket and GBS), the different execution phases are briefly explained: design, fabrication and installation. Special attention is given to some principles of topside design. A basic introduction to cost aspects is presented. Finally terms are introduced through a glossary.
1. INTRODUCTION Offshore platforms are constructed to produce the hydrocarbons oil and gas. The contribution of offshore oil production in the year 1988 to the world energy consumption was 9% and is estimated to be 24% in 2000. The investment (CAPEX) required at present to produce one barrel of oil per day ($/B/D) and the production costs (OPEX) per barrel are depicted in the table below. Condition
CAPEX $/B/D
OPEX $/B
Average
4000 - 8000
5
Middle East
500 - 3000
1
Non-Opec
3000 - 12000
8
North Sea
10000 - 25000
5 - 10
Deepwater
15000 - 35000
10 - 15
Conventional
Offshore
World oil production in 1988 was 63 million barrel/day. These figures clearly indicate the challenge for the offshore designer: a growing contribution is required from offshore exploitation, a very capital intensive activity. Figure 1 shows the distribution of the oil and gas fields in the North Sea, a major contribution to the world offshore hydrocarbons. It also indicates the onshore fields in England, the Netherlands and Germany.
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2. OFFSHORE PLATFORMS 2.1 Introduction of Basic Types The overwhelming majority of platforms are piled-jacket with deck structures, all built in steel (see Slides 1 and 2).
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Slide 1 : Jacket based platform - Southern sector North Sea
Slide 2 : Jacket based platform - Northern sector North Sea A second major type is the gravity concrete structure (see Figure 2), which is employed in the North Sea in the Norwegian and British sectors.
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A third type is the floating production unit.
2.2 Environment The offshore environment can be characterized by:
water depth at location soil, at seabottom and in-depth wind speed, air temperature waves, tide and storm surge, current ice (fixed, floes, icebergs) earthquakes (if necessary)
The topside structure also must be kept clear of the wave crest. The clearance cleara nce (airgap) usually is taken at approximately 1,50 m, but should be increased if reservoir depletion will create significant subsidence.
2.3 Construction The environment as well as financial aspects require that a high degree of prefabrication must be performed onshore. It is necessary to design to limit offshore work to a minimum. The overall cost of a man-hour offshore is approximately five times that of an onshore man-hour. The cost of construction equipment required to handle loads, and the cost for logistics are also a magnitude higher offshore. These factors combined with the size and weight of the items, require that a designer must carefully consider all construction activities between shop fabrication and offshore installation.
2.4 Codes Structural design has to comply with specific offshore structural codes. The worldwide leading structural code is the API-RP2A [1]. The rec recently ently issued Lloyds rules [2] and the DnV rules [3] are also important. Specific government requirements have to be complied with, e.g. in the rules of Department of Energy (DoE), Norwegian Petroleum Direktorate (NPD). For the detail design of the topside structure the AISC-code [4] is frequently used, and the AWS-code [5] is used for welding.
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In the UK the Piper alpha diaster has led to a completely new approach to regulation offshore. The responsibility for regulatory control has been moved to the Health and Safety Executive (HSE) and the operator has to produce a formal safety assessment (TSA) himself instead of complying with detailed regulations.
2.5 Certification and Warranty Survey Government authorities require that recognized bodies appraise the aspects of structural integrity and issue a certificate to that purpose. The major certification bodies are:
Det norske Veritas (DnV) Lloyds Register of Shipping (LRS) American Bureau of Shipping (ABS) Bureau Veritas (BV) Germanischer Lloyd (GL)
Their requirements are available to the designer [2, 3, 6, 7, 8]. Insurance companies covering transport and installation require the structures to be reviewed by warranty surveyors before acceptance. The warranty surveyors apply standards, if available, on a confidential basis.
3. OFFSHORE DEVELOPMENT OF AN OIL/GAS FIELD 3.1 Introduction The different requirements of an offshore platform and the typical phases of an offshore development are summarized in [9]. After several initial phases which include seismic field surveying, one or more exploration wells are drilled. drilled. Jack-up drilling rigs are used for this purpose for water depths up to 100 - 120 m; for deeper water floating rigs are used. The results are studied and the economics and risks of different development plans are evaluated. Factors involved in the evaluation may include number of wells required, fixed or floated production facilities, number of such facilities, and pipeline or tanker off-loading. As soon as exploitation is decided and approved, there are four main technical activities, prior to production:
engineering and design fabrication and installation of the production facility drilling of production wells, taking 2 - 3 months/well providing the off loading system (pipelines, tankers, etc.).
The drilling and construction interaction is described below for two typical fixed platform concepts.
3.2 Jacket Based Platform for Shallow Water First the jacket is installed. The wells are then drilled by a jack-up drilling unit standing close by with a cantilever rig extending over the jacket. Slide 3 shows a jack-up drilling unit with a cantilever rig. (In this instance it is engaged in exploratory drilling and is therefore working in isolation.)
Slide 3 : Cantilevered drilling rig: Self-elevating (jack-up) exploration drilling platform. Design and construction of the topside are progressed parallel to the drilling, allowing production to start soon after deck installation. For further wells, the jack-up drilling unit will be called once again and will reach over the well area of the production deck. As an alternative to this concept the wells are often accommodated in a separate wellhead platform, linked by a bridge to the production platform (see Slide 1).
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3.3 Jacket and Gravity Based Platform for Deep Water The wells are drilled from a drilling rig on the permanent platform (see Slide 2). Drilling starts after the platform is built and completely installed. Consequently production starts between one and two years after platform installation. In recent years pre-drilled wells have been used to allow an earlier start of the production. In this case the platform has to be installed exactly above the pre-drilled wells.
4. JACKETS AND PILE FOUNDATION 4.1 Introduction Jackets, the tower-like braced tubular structures, generally perform two functions:
They provide the substructure for the production facility (topside), keeping it stable above the waves. They support laterally and protect the 26-30 inch well conductors and the pipeline riser.
The installation methods for the jacket and the piles have a profound impact on the design.
4.2 Pile Foundation The jacket foundation is provided by open-ended tubular steel piles, with diameters up to 2m. The piles are driven approximately 40 - 80 m, and in some cases 120 m deep into the seabed. There are basically three types of pile/jacket arrangement (see Figure 3):
Pile-through-leg concept, where the pile is installed in the corner legs of the jacket. Skirt piles through pile sleeves at the jacket-base, where the pile is installed in guides attached to the jacket leg. Skirt piles can be grouped in
clusters around each of the jacket legs. Vertical skirt piles are directly installed in the pile sleeve at the jacket base; all other guides are deleted. This arrangement results in reduced
structural weight and easier pile driving. In contrast inclined piles enlarge the foundation at the bottom, thus providing a stiffer structure.
4.3 Pile Bearing Resistance Axial load resistance is required for bearing as well as for tension. The pile accumulates both skin friction as well as end bearing resistance.
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Lateral load resistance of the pile is required r equired for restraint of the horizontal forces. These forces lead to significant bending of the pile nnear ear to the seabed. Number, arrangement, diameter and penetration of the piles depend on the environmental loads and the the soil conditions at the location.
4.4 Corrosion Protection The most usual form of corrosion protection of the bare underwater part of the jacket as well as the upper part of the piles in soil is by cathodic protection using sacrificial anodes. A sacrificial anode (approximate 3 kN each) consists of a zinc/aluminium bar cast about a steel tube and welded on to the structures. Typically approximately 5% of the jacket weight is applied as anodes. The steelwork in the splash zone is usually protected by a sacrificial wall thickness of 12 mm to the members.
5. TOPSIDES 5.1 Introduction The major functions on the deck of an offshore platform are:
well control support for well work-over equipment separation of gas, oil and non-transportable components in the raw product, e.g. water, parafines/waxes and sand support for pumps/compressors required to transport the product ashore power generation accommodation for operating and maintenance staff.
There are basically two structural types of topside, the integrated and modularized topside which are positioned either on a jacket or on a concrete gravity substructure.
5.2 Jacket-based Topsides 5.2.1 Concepts
There are four structural concepts in practice. They result from the lifting capacity of crane vessels and the load-out capacity at the yards:
the single integrated deck (up to approx 100 MN) the split deck in two four-leg units the integrated deck with living quarter module the modularized topside consisting of module support frame (MSF) carrying a series of modules.
Slide 4 shows an integrated deck (though excluding the living quarters and helideck) being moved from its assembly building.
Slide 4 : Integrated topside during load out 5.2.2 Structural Design for Integrated Topsides
For the smaller decks, up to approximately 100 MN weight, the support structure consists of trusses or portal frames with deletion of diagonals. The moderate vertical load and shear per column allows the topside to be supported by vertical columns (deck legs) only, down to the top of the piles (situated at approximately +4 m to +6 m L.A.T. (Low Astronomic Tide). 5.2.3 Structural Design for Modularize Modularized d Jacket-based Topsides
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A major modularized topside weighs 200 to 400 MN. In this case the MSF is a heavy tubular structure (Figure 4), with lateral bracing down to the top of jacket.
5.3 Structural Design for Modularized Gravity-based Topsides The topsides to be supported by a gravity-based substructure (see Figure 2) are in a weight range of 200 MN up to 500 MN. The backbone of the structure is a system of heavy box-girders with a height of approximately 10 m and a width of approximately 12 - 15 m (see Figure 5).
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The substructure of the deck is rigidly connected to the concrete column and acts as a beam supporting the deck modules. This connection introduces wave-induced fatigue in the deck structure. A recent development, foreseen for the Norwegian Troll platform, is to provide a flexible connection between the deck and concrete column, thus eliminating fatigue in the deck [10].
6. EQUIPMENT AND LIVING QUARTER MODULES Equipment modules (20-75 MN) have the form of rectangular boxes with one or two intermediate floors. The floors are steel plate (6, 8 or 10 mm thick) for roof and lower floor, and grating for intermediate floors. In living quarter modules (5-25 MN) all sleeping rooms require windows and several doors must be provided in the outer wa walls. lls. This requirement can interfere seriously with truss arrangements. Floors are flat or stiffened plate. Three types of structural concepts, all avoiding interior columns, can be distinguished:
conventional trusses in the walls. stiffened plate walls (so called stressed skin or deck house type). heavy base frame (with wind bracings in the walls).
7. CONSTRUCTION 7.1 Introduction The design of offshore structures has to consider various requirements of construction relating to: 1. 2. 3. 4. 5. 6. 7. 8.
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A documented construction strategy should be available during all phases of the design and the actual design development should be monitored against the construction strategy.
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Construction is illustrated below by four examples.
7.2 Construction of Jackets and Topsides 7.2.1 Lift Installed Jackets
The jacket is built in the vertical (smaller jackets) or horizontal position (bigger jackets) on a quay of a fabrication site. The jacket is loaded-out and seafastened aboard a barge. At the offshore location the barge is moored alongside an offshore crane vessel. The jacket is lifted off the barge, upended from the horizontal, and carefully set down onto the seabed. After setting down the jacket, the piles are installed into the sleeves and, driven into the seabed. Fixing the piles to the jacket completes the installation. 7.2.2 Launch Installed Jackets
The jacket is built in horizontal position. For load-out to the transport barge, the jacket is put on skids sliding on a straight track of steel beams, and pulled onto the barge (Slide 5).
Slide 5 : Jacket being loaded onto barge by skidding At the offshore location the jacket is slid off the barge. It immerses deeply into the water and assumes a floating position afterwards (see Figure 6).
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Two parallel heavy vertical trusses in the jacket structure are required, capable of taking the support reactions during launching. To reduce forces and moments in the jacket, rocker arms are attached to the stern of the barge. The next phase is to upright the jacket by means of controlled flooding of the buoyancy tanks and then set down onto the seabed. Self-upending jackets obtain a vertical position after the launch on their own. Piling and pile/jacket pile/jacket fixing completes the installation. 7.2.3 Topsides for a Gravity-Based Structure (GBS)
The topside is assembled above the sea on a temporary support near a yard. It is then taken by a barge of such dimensions as to fit between the columns of the temporary support and between the columns of the GBS. The GBS is brought in a deep floating condition in a sheltered site, e.g. a Norwegian fjord. The barge is positioned between the columns and the GBS is then deballasted to mate with and to take over the deck from the barge. The floating GBS with deck is then towed to the offshore site and set down down onto the seabed. 7.2.4 Jacket Topsides
For topsides up to approximately 120 MN, the topside may be installed in one lift. Slide 6 shows a 60 MN topside being installed by floating cranes.
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Slide 6 : Installation of 60MN K12-BP topside by floating crane For the modularized topside, first the MSF will be installed, immediately followed by the modules.
7.3 Offshore Lifting Lifting of heavy loads from barges (Slide 6) is one of the very important and spectacular construction activities requiring a focus on the problem when concepts are developed. Weather windows, i.e. periods of suitable weather conditions, are required for these operations. 7.3.1 Crane Vessel
Lifting of heavy loads offshore requires use of specialized crane vessels. Figure 7 provides information on a typical big, dual crane vessel. Table 1 (page 16) lists some of the major offshore crane vessels.
7.3.2 Sling-arrangement, Slings and Shackles
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Notes: 1. Rated lifting lifting cap capacity acity in me metric tric ttonnes. onnes. 2. When the crane vessels are provi provided ded with two cranes, these cranes are situated at the vessels stern or bow at approximately approximately 60 m distance distance c.t.c. 1. 3. Rev = Lo Load ad capabi capability lity w with ith ful fully ly revol revolving ving crane. crane. Fix = Load capability with crane fixed.
7.4 Sea Transport and Sea Fastening Transportation is performed aboard a flat-top barge or, if possible, on the deck of the crane vessel. The module requires fixing to the barge (see Figure 9) to withstand barge motions in rough seas. The sea fastening concept is determined by the positions of the framing in the module as well as of the "hard points" points" in the barge.
7.5 Load-out 7.5.1 Introduction
For load-out three basic methods are applied:
skidding
platform shearlegs.trailers
7.5.2 Skidding
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Skidding is a method feasible for items of any weight. The system consists of a series of steel beams, acting as track, on which a group of skids with each approximately 6 MN load capacity is arranged. Each skid is provided with a hydraulic jack to control the reaction. 7.5.3 Platform Trailers
Specialized trailer units (see Figure 10) can be combined to act as one unit for loads up to 60 - 75 MN. The wheels are individually suspended and integrated jacks allow adjustment up to 300 mm.
The load capacity over the projected ground area varies from approximately 55 to 85 kN/sq.m. The units can drive in all directions and negotiate curves. c urves. 7.5.4 Shearlegs
Load-out by shearlegs is attractive for small jackets built on the quay. Smaller decks (up to 10 - 12 MN) can be loaded out on the decklegs pre positioned on the barge, thus allowing deck and deckleg to be installed installed in one lift offshore.
7.6 Platform Removal In recent years platform removal has become common. The mode of removal depends strongly on the regulations of the local authorities. Provision for removal should be considered in the design phase.
8. STRUCTURAL ANALYSIS 8.1 Introduction
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The majority of structural analyses are based on the linear theory of elasticity for total system behaviour. Dynamic analysis is performed for the system behaviour under wave-attack if the natural period exceeds 3 seconds. Many elements can exhibit local dynamic behaviour, e.g. compressor foundations, flare-stacks, crane-pedestals, slender jacket members, conductors.
8.2 In-place Phase Three types of analysis are performed:
Survival state, under wave/current/wind attack with 50 or 100 years recurrence period. Operational state, under wave/current/wind attack with 1 or 5 years recurrence period, under full operation. Fatigue assessment. Accidental.
All these analyses are performed on the complete and intact structure. Assessments at damaged structures, e.g. with one member deleted, and assessments of collision situations are occasionally performed.
8.3 Construction Phase The major phases of construction when structural integrity may be endangered are:
Load-out Sea transport Upending of jackets Lifting.
9. COST ASPECTS 9.1 Introduction The economic feasibility of an offshore project depends on many aspects: capital expenditure (CAPEX), tax, royalties, operational expenditure (OPEX). In a typical offshore field development, one third of the CAPEX is spent on the platform, one third on the drilling of wells and one third on the pipelines. Cost estimates are usually prepared in a deterministic approach. Recently cost-estimating using a probabilistic approach has been developed and adopted in major offshore projects. The CAPEX of an installed offshore platform topside amounts to approximately 20 ECU/kg.
9.2 Capital Expenditure (CAPEX) The major elements in the CAPEX for an offshore platform are:
project management and design material and equipment procurement
fabrication transport and installation hook-up and commissioning.
9.3 Operational Expenditure (OPEX) In the North Sea approximately 20 percent of OPEX are required for offshore inspection, maintenance and repair (IMR). The amount to be spent on IMR over the project life can add up to approximately half the original investment. IMR is the area in which the structural engineer makes a contribution by effort in design, selection of material, improved corrosion protection, accessibility, basic provisions for scaffolding, avoiding jacket attachments dangerous to divers, etc.
10. DEEP WATER DEVELOPMENTS Deep water introduces a wide range of extra difficulties for the operator, the designer and constructor of offshore platforms. Fixed platforms have recently been installed in water of 410 m. depth, i.e. "Bullwinkle" developed by Shell Oil for a Gulf of Mexico location. The jacket weighed nearly 500 MN. The maximum depth of water at platform sites in the North Sea is approximately 220 m at present. The development of the Troll field situated in approximately 305 m deep water is planned for 1993.
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In the Gulf of Mexico and offshore California several fixed platforms in water depths of 250 - 350 m are in operation (Cerveza, Cognac). Exxon has a guyed tower platform (Lena) in operation in 300 m deep water. An option for deeper locations is to use subsea wells with flowlines to a nearby (approximately maximum 10 km) fixed platform at a smaller water depth. Alternatively subsea wells may be used with flexible risers to a floating floating production unit. Subsea wells are now feasible for 300 - 900 m deep water. The deepest wells have been developed off Brasil in moderate weather conditions. The tension leg platform (TLP) seems to be the most promising deepwater production unit (Figure 11). It consists of a semi-submersible pontoon, tied to the seabed by vertical prestressed tethers. The first TLP was Hutton in the North Sea and recently TLP-Jolliet was installed at a 530 m deep location in the Gulf of Mexico. Norwegian Snorre and Heidrun fields have been developed with TLPs as well.
11. CONCLUDING SUMMARY
The lecture starts with the presentation of the importance of offshore hydro-carbon exploitation, the basic steps in the development process (from seismic exploration to platform removal) and the introduction of the major structural concepts (jacket-based, GBS-based, TLP, floating). The major codes are identified. For the fixed platform concepts (jacket and GBS), the different execution phases are briefly explained: design, fabrication and installation. Special attention is given to the principles of topside design. A basic introduction to cost aspects is presented. Finally terms are introduced within a glossary.
12. GLOSSARY OF TERMS AIR GAP Clearance between the top of maximum wave and underside of the topside.
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CAISSONS See SUMPS CONDUCTORS The tubular protecting and guiding the drill string from the topside down to 40 to 100m under the sea bottom. After drilling it protects the well casing. G.B.S. Gravity based structure, sitting flatly on the sea bottom, stable through its weight. HOOK-UP Connecting components or systems, after installation offshore. JACKET Tubular sub-structure under a topside, standing in the water and pile founded. LOAD-OUT The operation of bringing the object (module, jacket, deck) dec k) from the quay onto the transportation barge. PADEARS (TRUNNIONS) Thick-walled tubular stubs, directly receiving slings and transversely welded to the main structure. PADEYES Thick-walled plate with hole, receiving the pin of the shackle, welded to the main structure. PIPELINE RISER The piping section which rises from the sea bed to topside level. SEA-FASTENING The structure to keep the object rigidly connected to the barge during transport. SHACKLES Connecting element (bow + pin) between slings and padeyes. SLINGS Cables with spliced eyed at both ends, for offshore lifting, the upper end resting in the crane hook. SPREADER Tubular frame, used in lifting operation. SUBSEA TEMPLATE Structure at seabottom, to guide conductors prior to jacket installation. SUMPS Vertical pipes from topside down to 5-10 m below water level for intake or discharge. TOPSIDE Topside, the compact offshore process plant, with all auxiliaries, positioned above the waves. UP ENDING Bringing the jacket in vertical position, prior to set down on the sea bottom. WEATHER WINDOW A period of calm weather, defined on basis of operational limits for the offshore marine operation. WELLHEAD AREA Area in topside where the wellheads are positioned including the valves mounted on its top.
13. REFERENCES [1] API-RP2A: Recommended practice for planning, designing and constructing fixed offshore platforms. American Petroleum Institute 18th ed. 1989. The structural offshore code, governs the majority of platforms. [2] LRS Code for offshore platforms. Lloyds Register of Shipping. London (UK) 1988. Regulations of a major certifying authority. [3] DnV: Rules for the classification of fixed offshore installations. Det Norske Veritas 1989. Important set of rules. [4] AISC: Specification for the design, fabrication and erection of structural steel for buildings. American Institute of Steel Construction 1989. Widely used structural code for topsides.
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[5] AWS D1.1-90: Structural Welding Code - Steel. American Welding Society 1990. The structural offshore welding code. [6] DnV/Marine Operations: Standard for insurance warranty surveys in marine operations. Det norske Veritas June 1985. Regulations of a major certifying authority. [7] ABS: Rules for building and classing offshore installations, Part 1 Structures. American Bureau of Shipping 1983. Regulations of a major certifying authority. [8] BV: Rules and regulations for the construction and classification of offshore platforms. Bureau Veritas, Paris 1975. Regulations of a major certifying authority. [9] ANON: A primer of offshore operations. Petex Publ. Austin U.S.A 2nd ed. 1985. Fundamental information about offshore oil and gas operations. [10] AGJ Berkelder et al: Flexible deck joints. ASME/OMAE-conference The Hague 1989 Vol.II pp. 753-760. Presents interesting new concept in GBS design.
14. ADDITIONAL READING 1. BS 623 6235: 5: Code ooff practi practice ce for fix fixed ed offsh offshore ore structures. structures. British Standards Institution 1982. Important code, mainly for the British offshore sector. 2. DoE Offshore installations: Guid Guidance ance on ddesign esign and construction, U.K. Department of Energy 1990. Governmental regulations for British offshore sector only. 3. UEG: D Design esign of tubu tubular lar jo joints ints ((33 volu volumes). mes). UEG Offshore Research Publ. U.R.33 1985. Important theoretical and practical book. 4. J. W Wardeni ardenier: er: H Hollow ollow sectio sectionn jo joints. ints. Delft University Press 1981. Theoretical publication on tubular design including practical design formulae. 5. ARSE ARSEM: M: Design gui guides des for offsho offshore re structu structures res welded tu tubular bular joi joints. nts. Edition Technip, Paris (France), 1987. Important theoretical and practical book. 6. D. Jo Johnsto hnston: n: Fi Field eld ddevelop evelopment ment optio options. ns.
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Oil & Gas Journal, May 5 1986, pp 132 - 142. Good presentation on development options. 7. G. I. Claum et al: Offshore Structures: Vol 1: Conceptual Design and Hydri-mechanics; Vol 2 - S Strength trength and Safety for Structural Structural design. Springer Verlag, London 1992. Fundamental publication on structural behaviour. 8. W.J. G Graff: raff: In Introduc troduction tion to to offsh offshore ore str structures uctures.. Gulf Publishing Company, Houston 1981. Good general introduction to offshore structures. 9. B.C. G Gerwick: erwick: Const Constructio ructionn of offsh offshore ore stru structures ctures.. John Wiley & Sons, New York 1986. Up to date presentation of offshore design and construction. 10. T.A. Doody et al: Import Important ant consideratio considerations ns for successfu successfull fabricati fabrication on of offshore struc structures. tures. OTC paper 5348, Houston 1986, pp 531-539. Valuable paper on fabrication aspects. 11. D.I. Kars Karsan an et al: An economic stu study dy on paramete parameters rs influen influencing cing the cost of fixed fixed platform platforms. s. OTC paper 5301, Houston 1986, pp 79-93. Good presentation on offshore CAPEX assessment. Previous | Next | Next | Contents
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6/9/2009 PRODUCT FAMILY BROCHURE
Key Components Modeling • Precede Graphical Modeler • Datagen Intelligent Editor ®
• Gap Elements • Superelements • Hull Modeling & Meshing
SACS Analysis Packages
Design and Analysis Software for Offshore Structures & Vessels
Loads • Seastate Wave, Wind, Current Current • Buoyancy, Mud flow • Gravity, Inertial • Skid, Moving
Analysis • SACS IV Solver • Large Deflection (LDF)
SACS is an integrated finite element structural analysis suite of applications that uniquely provides for the design, fabrication, installation, operations, and maintenance of offshore structures, including oil platforms and wind farms. Nearly 40 years of focus on these specialized requirements have made SACS the analysis mainstay for most of the world’s offshore engineers. Virtually all of the world’s energy companies specify SACS software for use by their engineering firms fir ms across the lifecycle of offshore platforms. Three options of the SACS software suites are available: Offshore Structure Enterprise for comprehensive capabilities required for typical offshore jackets, wharfs, and dolphin structures; Offshore Structure Advanced for static topside and deck analysis; and Offshore Structure for static structural analysis.
• PSI Pile/Structure Analysis
Offshore Structure Enterprise:
interactive graphics modeler with advanced 3D capabilities,
• Liquefaction
The Professional Static Offshore package contains capabilities required for typical offshore jackets, wharfs, and dolphin structures. It includes the interactive graphics modeler with advanced advanced 3D capab capabilities, ilities, SACS IV solver and interactive graphics 3D post processor, processor, Seastate, Joint Can, Pile, Combine, Gap, Tow, and LDF large deflection. The package also includes automatic model generation, beam and finite element capability, steel code check and redesign, environmental load generation, tubular connection check, single pile/soil interaction, inertia and moving load generation, tension/ compression nonlinear elements with initial gap, load case combination, linear large deflection analysis, and full output report and plotting capabilities. The package also contains the multi-core analysis capability, allowing the user to conduct multiple analysis of the same type in parallel, saving hours of runtime.
SACS IV Loading, solver and interactive graphics 3DLDF post-processor, Topsides Combine, Gap, Tow, and large deflection. The package also includes automatic model generation, beam and finite element capability, steel code check and redesign, wind and gravity load generation, inertia and moving load generation, tension/compression nonlinear elements with initial gap, load case combination, linear large deflection analysis, and full output report and plotting capabilities.
• Wind Turbine Analysis • Dynpac Modal Analysis • Collapse • Tow, Launch, and Flotation • Motions and Stability
Design • Combine Solution Files • Post Offshore Code Code Design • Concrete design • Postvue Graphical Redesign • Joint Can • Interactive Fatigue
Offshore Structure Advanced:
• Dynamic Fatigue
The Professional Static Topsides package contains capabilities required for typical topside and deck analysis. It includes the
• Wave Fatigue
Offshore Structure: The Professional Static Analysis package contains capabilities required for static structural analysis. It includes the interactive graphics modeler with advanced 3D capabilities, SACS IV solver and interactive graphics 3D post-processor, Combine, Gap, Tow, and LDF large deflection. The package also includes automatic model generation, beam and finite element capability, steel code check and redesign, inertia and moving load generation, tension/compression nonlinear elements with initial gap, load case combination, linear large deflection analysis, and full output report and plotting capabilities.
SACS ANALYSIS PACKAGES
The following add-on modules extend the functionality of any of the three Offshore Structure suites.
Pile Structure Design: Soil/Pile/Structure Soil/Pile/Structur e Interaction Analysis
Wind: Wind Turbine Package
This non-linear add-on package permits non-linear soil/pile/ structure interaction analysis of fixed offshore structures with multiple fixed supports using the PSI program modules. It requires the use of the Offshore Structure, Offshore Structure Advanced, or Offshore Structure Enterprise package.
The Wind Turbine package is comprised of the following packages necessary for wind turbine platform design: Offshore Structure Enterprise, Pile Structure Design, Collapse, and Fatigue Enterprise. The package also contains the SACS interfaces to the GH Bladed and FAST wind turbine aero-elastic modules. Full automation including
Collapse: Plastic Non-Linear Add-On
multi-core analysis capability is included for efficient analysis of a large number of time history simulations.
This add-on package performs advanced plastic analysis including pushover, ship impact, and blast non-linear analysis. It requires the use of the Offshore Structure, Offshore Structure Advanced, or Offshore Structure Enterprise package.
Fatigue Advanced – Dynamic Response: Fatigue Package with Dynamic Response This Advanced Dynamic Fatigue package contains the modules required to determine the wind fatigue damage of a dynamic system. This package contains DYNPAC, Fatigue, Interactive Fatigue, and Dynamic Response. It requires the use of the Offshore Structure, Offshore Structure Advanced, or Offshore Structure Enterprise package.
Fatigue Advanced – Wave Fatigue Package with WaveResponse: Response
Parametric Study for the Fatigue Design of a Wind Turbine Transition Piece
This Advanced Dynamic Fatigue package contains the modules required to determine the fatigue damage of a dynamic system subject to wave loads. This package contains DYNPAC, Fatigue, Interactive Fatigue, and Wave Response. It requires the use of the Offshore Structure, Offshore Structure Structure Advanced, or Offshore Structure Enterprise package.
Marine: Marine Installation Add-On The Marine Installation Add-on package permits launch and upending analysis. The package includes the Launch and Flotation program modules, and requires the use of the Offshore Structure, Offshore Structure Advanced, or Offshore Structure Enterprise package.
Marine Enterprise: Hull Modeling and Meshing, Motions, and Stability Analysis The Marine Enterprise Add-on provides modeling and meshing of vessel hulls, calculation of stability, and prediction of vessel motions. It can be used for new or existing FPSO studies, as well as for transportation and installation analysis. It links with the Tow module for calculation of motions induced loads and downstream code checking and fatigue calculations. The package contains the Hull Modeler, Hull Mesher Motions, and Stability modules, and requires the use of the Offshore Structure, Offshore Structure Advanced, or Offshore Structure Enterprise package. Ship Impact Analysis
Fatigue Enterprise: Fatigue Package with Wave Response and Dynamic Response This Advanced Dynamic Fatigue package contains the modules required to perform any dynamic deterministic, time history, or spectral fatigue analysis. This package contains DYNPAC, Fatigue, Interactive Fatigue, Dynamic Response, and Wave Response. It requires the use of the Offshore Structure, Offshore Structure Advanced, or Offshore Structure Enterprise package. Motions prediction on an FPSO.
SACS ANALYSIS PACKAGES
The following software modules extend the functionality of any of the three Offshore Structure suites and are either included within those packages or available as add-on modules. Please consult your Bentley representative for product specifics relative to your needs.
SACS Executive: Common Interface to Program Suite
• Physical member support capab capabilities ilities
• Controls and connects all elements of the SACS system
• Supports full 3D geometry and section properties
• Launches all SACS interactive programs
• Allows SACS model files to be ported directly to a PDMS mac macro ro
• Executes all batch program analyses analyses • Allows access to all SACS system configuration settings, including system file location and security key settings
file, which creates the 3D model in PDMS • Supports PDMS section libraries in addition to creating PDMS sections for sections defined in the SACS model
• Includes command line help and power buttons for the most commonly executed tasks
• Logging functionality
• Professional and other ACIS-enabled CAD packages
• ISM Export to ProSteel and other steel detailing systems
• Specifies analysis options without changing data input file
Data Generator: Interactive Data Generation for all Programs
Precede: Interactive Full Screen Graphics Modeler
• Intelligent full screen editor that labels and highlights data fields and provides help for data input
• Model generation capabilities include geometry, material and section properties, and loading
• Form-filling data input available as well as full screen screen mode
• Automatic input error detection detection
• Automatic data checking
• Maintains data backup
Seastate:
• Beam and/or finite element modeling including plate and shell elements
Environmental Loads Generator • Ability to view plot files on screen
• Automatic offshore jacket and deck generation
• Sends viewed plots to printer/plot printer/plotter ter
• User defined input units
• Supports HP-GL, Postscript, DXF, Windows devices
• Cartesian, cylindrical, or spherical mesh generation
• Metafile (WMF), and SACS N NPF PF plot file
• Automatic weight or load generation including gravity, pressure, and skid mounted equipment loads
• Allows plot size, character size, margins, formats, etc. • Ability to modify chart setting settingss
• Seastate data generation capabilities capabilities
• Full implementation of A API PI 21st edition
• Extensive plotting and reporting capabilities • Code check parameter generation including K-factors and compression flange unbraced lengths • Allows SACS model files to be converted into 3D SAT file format compatible with AutoCAD, AutoCAD, and other CAD systems systems
• Supports five wave theories • Current included or excluded • Generates load due to wind, gravity, buoyanc buoyancy, y, and mud flow
Offshore System Types
SACS has applications for all types of offshore structures & vessels 1. Fixed Platforms
3. Tension Leg Platforms
2. Compliant Tower
4. Semi-Submersibles
5. FPSOs
SACS ANALYSIS PACKAGES
• Marine growth, flooded, and non-flooded member memberss • RAO and acceleration loading including non-structural weights • Moving loads generation • Diameter, Reynolds number, and wake encounter effects dependent drag and inertia coefficients
Post: Beam and Finite Element Code Check and Redesign • Beam and plate element code check and redesign
• Weight load cases
• API (including 21st edition), AISC, LRFD, Norsok, Eurocode 3, Canadian, DNV, British Standards, and Danish DS449 code check
• Forces on non-struct non-structural ural bodies
• Plate panel checks in accordance to DnV-RP-C201
• Deterministic and random wave modeling for dynamic response
• Creates updated model with redesigned elements elements
• Member hydrodynamic modeling for static and dynamic analysis
• Modify code check parameters parameters • Load combination capabilities capabilities • Supports codes from 1977 to present • Detailed and summary reports • Hydrostatic collapse analysis analysis • Span (multi-member effects) effects) • ISO 19902
Joint Can: Tubular Joint Code Check and Redesign • Present and past codes including latest API 21st edition, supplement 2, and LRFD, Norsok, DS449, and Canadian • API earthquake and simplified fatigue analysis • ISO 19902 Automatic Joint Meshing
• Connection strength (50 percent) percent) check • Overlapping joints analyzed analyzed
SACS IV Solver: Static Beam and Finite Element Analysis • Beam elements including tubulars, tee tees, s, wide flanges, channels, angles, cones, plate and box girders, stiffened
• Minimum and extreme seismic analysis analysis
Postvue: Interactive Graphics Post Processor
• Discrete Kirchoff Theory (DKT) thin-plates
• Interactive member and tubular joint code check and redesign, with the option to print code check details for latest AISC, ASD and LRFD, API, ISO 19902 codes
• Isoparametric 6-, 8-, and 9-node shell element elementss
• Display shear and bending moment diagrams
• Library of AISC, U.K., European, German German,, Chinese, and Japanese cross sections, as well as user-defined libraries
• Display deflected shapes for static and dynamic analyses
• Member, plate and shell local and global offsets
• Code check and redesign by individual or group of elements
cylinders, and boxes • Solid and plate elements (isotropic and stif stiffened) fened)
• Beam and finite element thermal loads • Elastic supports defined in global or refer reference ence joint coordinate system • Specified support joint displace displacements ments • Unlimited load cases • P-delta effects • Master/slave D DOF OF
• Color plate stress contour plots plots
• Supports same codes as post module • Extensive reporting and plotting plotting capabilities • Color-coded results and unity check check plots • Creates updated input model file for re-analysis re-analysis • Labels UC ratio, stresses, and internal forces on elements
SACS ANALYSIS PACKAGES
PSI: • API P-Y / T-Z Soil • API Adhesion Soil
• User Defined P-Y / T-Z Soil • User Defined Adhesion Soil
Concrete: Reinforced Concrete Code Check and Redesign
• Reservoir (rain flow) cycle coun counting ting method
• Rectangular, Circular, Tee, Tee, and L cross sections
Interactive Fatigue: Interactive Fatigue Life Evaluation
• Beam, bi-axial beam-column, slab, and wall elements supported • Multiple reinforcement patterns patterns can be specified • Code check per ACI 318-89 (Revised 1992)
• ISO 19902
• Shows the 3D view of the connection and allows braces to be selected with the mouse
• Shear reinforcement check and redesign
• Reads connection defaults when joint and/or brace is/are selected, thus eliminating the need to calculate and display
• Reinforcement development length check
• SCFs before viewing capacity or modifying properties
• Deflection and creep calculation
• Recognizes all SCF and S-N options available in the batch program
• Second order/P-delta analysis capabilities capabilities
• Allows SCF theory to be changed for any type connection, including includin g in-line connections and connections with user defined SCFs
Fatigue: Fatigue Life Evaluation and Redesign • Spectral, time history, and deterministic fatigue analysis • Cyclic stress range calculation procedures procedures include wave search, curve fit, and interpolation • SCF calculations recommended recommended by API (including 21st ed. supplements), HSE, DNV, DS449 and Norsok Codes
• Reports have been expanded and rework reworked ed to make them easier to read • Reports and plots can be displayed on the scree screenn and/or saved to a file • Automatic redesign
• Automatic redesign
GAP: Non-linear Analysis With One-way Elements
• API (including 21st ed. supplements), AWS, HSE, and Nor Norsok sok thickness dependent recommended S-N curves
• Accurate simulation of load out or transportation analysis using one-way elements
• Multiple run damage accumulation
• Tens Tension ion or compression gap elements with initial gap
• Pierson-Moskowitz, Pierson-Moskowitz, JONSWAP, Ochi-Hubble double peak, simplified double peek, and user-defined spectra
• General non-linear elemen elements ts
• Automated or user-specified connection details
• Friction element
• Pile fatigue analysis
PSI: Non-linear Soil, Pile, and Structure Interaction
• Creates wave spectra from scatter diagram
• Beam column effects included
• Uses Paris equation to predict crack growth rate due to cyclic stresses
• Non-uniform piles
• Load path dependent joint classifications classifications • Includes wave spreading effects effects
• P-Y and T-Z curves, axial adhesion and springs • API P-Y, T-Z, skin friction and adhesion data generated generated from soil properties per API
SACS ANALYSIS PACKAGES
Non-linear Elasto-plastic Deformations
• Full structural analysis and pile code check API, LRFD, Norsok, HSE, DS449, Canadian, and DNV • Offset P-Y & T-Z curves for muds mudslides lides • Full plotting and graphical representation of soil data and results, including stresses, P-Y, T-Z curves • Soil liquefact liquefaction ion effects
Pile: Isolated 3D Pile Analysis
• Full stress recovery • Superelements can contain other superelements • Translation and rotation of superelements superelements
Combine: Common Solution File Utility • Combines dynamic and static results from one or multiple solution files
• Beam column and pile batter effects includ included ed
• Combines Co mbines results from analyzes having different member, plates, etc.
• Uses PSI soil data
• Superimposes mode shapes shapes
• Optional pile head springs • Specify force at or below pile head
• “Worst-case” combination combination of dead loads with earthquake response
• Specify pile head displacements • Specified pile head forces or displacemen displacements ts • Automatic generation of linear equivalent pile stubs for dynamic or static analysis • Soil liquefact liquefaction ion effects • Same plotting and code check features as PS PSII
Superelement: Automated Substructure Creation and Application
• Determine extreme wave loads from input spectra spectra
Large Deflection (LDF): Large Deflection Analysis • Iterative solution for geometric geometric • Solves plate membrane problems • Accounts for P-delta effects nonlinearities
Collapse: Non-linear Collapse Analysis • Linear and non-linear material behavior
• Unlimited number of superelements
• Non-linear springs
• Up to 1,000 interface joints per superelement
• Sequential load stacking capability capability
• Translation and rotation of superel superelements ements
• Activate and deactivate elements elements
• User defined stiffness matr matrices ices
• Joint flexibility options
SACS ANALYSIS PACKAGES
• Impact analysis with automatic unloading, built-in DnV ship indentation curves and energy absorption functionality
• Equivalent static load output for accurate stress recovery recovery
• Load cases may contain loading and/or specified displacements
• Time history analysis of wave and wind and time history load
• Includes geometric nonlinearities nonlinearities
• Buoyancy dynamic loads inclu included ded
• Plastic members and finite elements • Includes piles with non-linear soils and plasticity plasticity
• Stress, internal load, base shear, and overturning moment transfer function plots available
• Soil liquefaction effects effects
• Full coupling with Fatigue program
• Plastic DKT plates
• Elastic dynamic response of floating structures including stinger stingerss
• Zero crossing and RMS res responses ponses
• Input and output Power Spectral Densit Densities ies with Probability Distributions
Dynpac: Dynamic Characteristics
• Special features for wind turb turbine ine analysis
• Householder-Givens solution solution • Guyan reduction of non-essential degrees of freedom • Lumped or consistent structural mass generation generation
Dynamic Response: General Dynamic Response and Earthquake Analysis • Frequency domain analysis
• Automatic virtual mass generation generation • Complete seastate hydrodynamic modeling
• Time history, respons responsee spectrum or PSD-based driven input
• User input distributed and concentrated mass
• Time history and harmonic-fo harmonic-force rce driven input
• Non-structural Non-structural weight modeling
• SRSS, CQC and peak modal combination combinationss
• Full 6 DOF modes available for forced response response analysis
• API response spectra library and user input spectra
Wave Response: Dynamic Wave Response
• Wind spectral loading capability
• Deterministic and random waves • Pierson-Moskowitz, Jonswap, Ochi-Hubble, and user wave spectra
• Vibration analysis with multiple input points with user specified frequencies and phasing
• Harris, Von Karmon, and Kaimal wind spectra spectra
• General periodic forces decomposed by Fourier analysis
• Fluid-structure Fluid-structure relative velocity and acceleration accounted for “Modal Acceleration” and non-linear fluid damping
• Ice dynamics analy analysis sis
• Closed form steady state response in the frequency domain
• Response spectrum out output put at any joint
• Structural and fluid damping
• Engine/compressor vibrat vibration ion analysis
Flotation and Upending Analysis • Stability and Upending Analysis • Dual Hook Capabilities
• Buoyancy Tanks, Valves, User Defined Buoyancy
System Requirements Processor: Core 2 processor or better Operating System: Windows 7 or Windows 8 RAM: Minimum 2 GB of RAM
Transportation Analysis • Tow Analysis • Combine Multiple Common Solution Files • Static Analysis with Non-linear GAP Elements • Seafastener Design
Hard Disk: Minimum 2 GB of free hard disk space Display: Graphics card supporting Open GL 128 MB RAM or greater video card with 1280x1024 or higher video resolution
Find out about Bentley at: www.Bentley.com/ Offshore Contact Bentley 1-800-BENTLEY (1-800-236-8539) Outside the US +1 610-458-5000 Global Office Listings www.bentley.com/contact
• Equivalent static load and incrementa incrementall load output resulting from earthquake, ship impact, dropped object and blast analysis. This loading can be used for subsequent linear static analysis or for non-linear collapse analysis • Ship impact analysis
• Properties, forces, and positions plotted vs. step • Upending forces including gravity, sling loads, buoyancy, and buoyancy tank loads generated for any step of the upending sequence • Upending phase summary reports including including pitch, roll, and yaw angles, mud line clearance, etc.
• Dropped object analysis
Launch: Jacket Launch Analysis • Full launch motion time history analysis inc including luding hydrodynamic forces in all directions • Time history of jack jacket et and barge motions
Tow: Transportation Inertia Load Generator • Input motion for six degrees of freedom • Output location for selected points • Automatic weight calculation
• All phases of launch inc included luded
• User input member and joint weights
• Unbalanced loads generated for any positio positionn
• Generates distributed member and plate plate loads
• Launch sequence plot capability inclu including ding barge and jacket silhouette for designated steps
• Converts user defined loads into inertias inertias
• Anchor restraints
MTO: Material Take-Off, Weight Control, and Cost Estimation
Flotation: Jacket Flotation and Upending Analysis
• Member lengths including cuts
• Color coded snapshots of each upending ste stepp
• Steel tonnage and CG location
• Stability and upending analyses
• Material list, cost estimate, estimate, and weight control reports
• Initial floating and on bottom positions provided • Upending steps can include multiple commands • Dual hook capabilities
• Weld volume requirements and cost • Required protective anodes and cost cost • Surface area calculations by elevation elevation
®
SACS
• Buoyancy tanks, valves, user-spec user-specified ified buoyancy and weights and hydrodynamic overrides • Inclusion of marine growth for de-commis de-commissioning sioning
• Anode calculation in accordance to NACE SPO176-2007 (formerly RP0176-2003) and DnV-RP-B401
© 2013 Bentley Systems, Incorporated. Bentley, the “B” Bentley logo, and SACS are either registered or unregistered trademarks or service marks of Bentley Systems, Incorporated or one of its direct or indirect wholly owned subsidiaries. Other brands and product names are trademarks of their respective owners. CSR#3260 09/13
