Structural design loads for strength and fatigue, computed with a multi-variable load environment model

1970 ◽  
Author(s):  
G. JOHNSON
Keyword(s):  
Structural Design ◽  
Variable Load ◽  
Environment Model ◽  
Design Loads

Structural Design of Production Risers and Offshore Production Terminals

1980 ◽  
Vol 102 (2) ◽  
pp. 106-111
Author(s):  
W. R. Wolfram ◽  
R. H. Gunderson
Keyword(s):  
Structural Design ◽  
Oil Industry ◽  
Analysis Model ◽  
Unique Challenge ◽  
Offshore Production ◽  
Complete Procedure ◽  
Design Loads ◽  
Offshore Oil Industry ◽  
Deepwater Risers ◽  
Offshore Oil

Offshore production terminals and deepwater risers are seeing increasing use by the offshore oil industry. The structural design of these units presents a unique challenge compared to other offshore systems. Development of design loading conditions and fatigue histories is especially interesting due to the complex interaction of nonlinear riser and vessel dynamics, the statistical nature of maximum loads and the need to consider directionality as well as the magnitude of environmental loading. This paper presents a complete procedure for predicting design loads and fatigue histories for production risers and offshore terminals. The emphasis will be on systems wherein a dedicated vessel is connected to the riser by a rigid mooring arm. A number of structural design configurations will be surveyed. Techniques for preliminary sizing, dynamic analysis, model testing and fatigue analysis will be discussed. The application of this procedure to several specific design cases will be summarized.

Fail-Safe Structural Design

1958 ◽  
Vol 62 (574) ◽  
pp. 757-760
Author(s):  
W. T. Koiter
Keyword(s):  
Fatigue Strength ◽  
Structural Design ◽  
Flight Plan ◽  
Design Loads ◽  
Design Requirements ◽  
Fail Safe

MR. Harpur's interesting and stimulating paper (page 363, May 1958 Journal) is obviously of great importance to all who have to face the problem of fatigue strength of aircraft. These comments all refer to Section 3—Design Loads. Mr. Harpur's conclusions are based on analysis of a typical flight plan of a medium haul civil transport, and are formulated as a proposal for two fail-safe design requirements.

scholarly journals STRUCTURAL DESIGN PROCEDURES FOR CONCRETE ARMOUR UNITS

1984 ◽  
Vol 1 (19) ◽  
pp. 172 ◽  
Author(s):  
Kevin R. Hall ◽  
W.F. Baird ◽  
D.J. Turcke
Keyword(s):  
Structural Design ◽  
Rational Design ◽  
Structural Integrity ◽  
Design Procedure ◽  
Analytical Techniques ◽  
Structural Performance ◽  
Design Procedures ◽  
Design Loads ◽  
Resultant Stress ◽  
Hydraulic Stability

A rational design procedure for rubblemound breakwater protection which will ensure both the structural integrity and hydraulic stability of individual concrete armour units and the overall armour system is presented. The procedure involves new experimental techniques for measuring strains in model concrete armour units in a hydraulic model of a breakwater subjected to simulated prototype wave attack and analytical techniques for determining equivalent prototype loads on units. Selected design loads are used to define the resultant stress distribution to allow the designer to take the necessary measures to ensure the structural performance of the unit in a breakwater environment•

Toward a Probabilistic Approach to Determine Nominal Values of Tank Sloshing Loads in Structural Design of Liquefied Natural Gas FPSOs

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Jeom Kee Paik ◽  
Sang Eui Lee ◽  
Bong Ju Kim ◽  
Jung Kwan Seo ◽  
Yeon Chul Ha ◽  
...  
Keyword(s):  
Natural Gas ◽  
Structural Design ◽  
Probabilistic Approach ◽  
Liquefied Natural Gas ◽  
Flow Chart ◽  
Impact Loads ◽  
Operational Conditions ◽  
Oceanic Region ◽  
Design Loads ◽  
Tank Sloshing

The aim of this study is to develop a new probabilistic approach to determine nominal values for tank sloshing loads in structural design of LNG FPSO (liquefied natural gas, floating production, storage, and offloading units). Details of the proposed procedure are presented in a flow chart showing the key subtasks. The applicability of the method is demonstrated using an example of a hypothetical LNG FPSO operating in a natural gas site off a hypothetical oceanic region. It is noted that the proposed method is still under development for determining reliable estimates of extreme sloshing induced impact loads. It is concluded that the developed method is useful for determining the sloshing design loads in ship-shaped offshore LNG installations in combination with virtual metocean data and operational conditions.

scholarly journals Combination of Permanent and Variable Load Is Dependent

2021 ◽  
Vol 11 (10) ◽  
pp. 4434
Author(s):  
Tuomo Poutanen ◽  
Sampsa Pursiainen ◽  
Tim Länsivaara
Keyword(s):  
Structural Design ◽  
Physical Structure ◽  
Variable Load ◽  
Random Load ◽  
Design Work ◽  
Design Load ◽  
Load Combination ◽  
New Findings ◽  
Multiple Structures ◽  
Multiple Load

This study concerns the combination of the permanent and the variable loads in the structural design. The Eurocodes are used as a reference. Three new findings are presented: (1) In each physical structure, and in every load pair of the permanent load and the variable load, the maximum variable load is the service time load, the 50-year load, i.e., the high value of the variable load. Therefore, no load reduction should be applied in the combination. (2) The governing hypothesis is the independent load combination (ILC) with random load pairs and random single loads. However, the load pairs are not independent as normally one variable load occurs simultaneously in multiple structures and in multiple load pairs inducing correlation between the loads, ultimately full correlation, and the dependent load combination (DLC). (3) In the current Eurocodes, the design load combination applies to one load pair only. However, one design load combination virtually always applies to multiple load pairs which demands using the DLC. The authors have explained earlier that the permanent and variable loads should be combined dependently as the ILC contradicts the physics. The new findings support this conclusion. Changing the current codes towards the DLC approach would simplify them and eases their use in the structural design work.

Design and Welding Challenges in the Infield Flowlines of the Encana Deep Panuke Development

2010 ◽  
Author(s):  
Kenneth A. Macdonald ◽  
Craig Russell
Keyword(s):  
Structural Design ◽  
Steel Substrate ◽  
Pipe Material ◽  
Corrosion Resistant ◽  
Acid Gas ◽  
Industry Research ◽  
Offshore Pipeline ◽  
Clad Layer ◽  
Design Loads ◽  
Corrosion Resistant Alloy

Designing and constructing subsea flowlines to address the implications of aggressive hydrocarbon well fluids — and selecting suitably corrosion-resistant materials for such applications — typically proves challenging and often leads to the specification of clad, lined, or solid corrosion resistant alloy (CRA) linepipe materials. Design and construction guidance for such flowline systems is presently not comprehensive in offshore pipeline standards, even for cases where the thickness of the CRA layer is ignored in the structural design. Acergy are designing, procuring and installing a series of technically challenging infield flowlines within the Encana Deep Panuke gas prospect located off the coast of Sable Island, Nova Scotia. Presently being developed, first gas from the Deep Panuke field is scheduled for the third quarter of 2010 following the tie-in of the infield flowlines to their respective subsea production wellheads. These flowlines are to be installed using the Acergy Falcon, a vessel which has an installation system based on a variable angle J-lay principle and plastic deformation of the pipe. The four 8in production flowlines are clad linepipe comprising a 12.5 mm WT grade 415 (X60) carbon steel substrate with an internal 2.5mm Incoloy Alloy 825 clad layer that is metallurgically bonded to the mother pipe. The single 3in acid gas flowline is solid Inconel Alloy 625. The nominal level of installation plastic strain for the project ranges up to 1.675% in the case of the 8in line. Both lines will be welded by manual GTAW using Inconel 686 filler material. The pipelines are designed and fabricated in accordance with DNV OS-F101 supplemented by new guidance emerging from a DNV joint industry project on clad and lined materials. Metallurgically clad and mechanically bonded (lined) products present a mixture of common and unique challenges when designing and welding flowlines. The existing production limits for pipe dimensions in clad material have for some time now existed on the very cusp of design requirements, especially when using only the thickness of the steel substrate to resist the design loads. Indeed, recently the design demands of some projects have clashed with the available linepipe geometry and the mechanical properties of the clad layer material have of necessity been taken account of in the structural design. The dominant offshore design code, DNV OS-F101, is presently unable to offer specific guidance for including the clad layer and it is only in 2009 that joint industry research has established a viable design methodology for pressure containment wall thickness design which includes the strength effect of the clad layer. In addition to discussing the Deep Panuke design challenges and the welding philosophy for clad pipe, this paper also draws on approaches to welding and NDT successfully taken for the Statoil Tyrihans project in Norway, which used lined pipe material. The general welding philosophy adopted accommodates the continued inability of AUT systems to reliably inspect CRA weldments without false indications from normal metallurgical weld features. A proven approach is taken using intermediate inspection of the root and hot pass using real-time radiography (RTR); effecting any repairs needed; and then re-inspecting the weld upon fill and completion using RTR again. The importance of — and difficulty in — achieving adequate weld metal yield strength in CRA weldments is also discussed.

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