1、Proceedings of the 2014 Offshore Structural Reliability ConferenceSeptember 16 18, 2014Houston, TexasSpecial Notes Standard is a broad term covering all API documents that have been developed in accordance with APIs “Procedures for Standards Development”. Users of this document should be aware that
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15、electronic, mechanical, photocopying, or otherwise, without prior written permission from the publisher. Contact the Publisher, API Publishing Services, 1220 L Street, NW, Washington, DC 20005 Copyright 2015 American Petroleum Institute Introduction The 2014 Offshore Structural Reliability conferenc
16、e was hosted by API for the same purposes as similar past events such as DIRT (DesignInspectRedundancyTriangle) conference in 1983, the series of Civil Engineering in the Oceans conferences by the American Society of Civil Engineers (ASCE), and the Reliability of offshore structures workshop by the
17、Association of Oil & Gas Producers (OGP) in 2012 now the International Association of Oil & Gas Producers (IOGP). Practitioners and end-users of structural reliability methods were brought together for the purpose of sharing the collective knowledge of applying reliability theories and operating exp
18、eriences in order to address the offshore design and operational challenges facing the industry. These proceedings contain the material presented at this conference that included alternating sessions of instruction and topical papers starting with the history of offshore reliability studies, progres
19、sed to current activities, and then finally outlined issues for future resolution. This event was of interest for operators, engineers, regulators, academics, and anyone else involved in the design and operations of offshore structures. ContentsKeynote 1 History Behind the Development of Limit State
20、 (LRFD) Offshore Structures Design StandardsSession 1 Basic Principles of Structural ReliabilitySession 2 History & Background2.1 Historical Perspective on the Reliability Design of Offshore Platforms for Earthquakes 2.2 Reliability of Fixed Offshore Structures: A Historical Perspective2.3 How Relia
21、ble are Reliability CalculationsSession 3 Environmental Criteria3.1 Approaches for the Probabilistic Modeling for Hurricane-induced Wind and Waves 3.2 Wave Loads on Platform Sub-structures and Decks of Fixed Steel Platforms 3.3 Evolution and Development of Offshore Seismic Criteria3.4 Uncertainty in
22、 Ice Actions on Offshore StructuresKeynote 2 Safety Assessment of Offshore StructuresSession 4 Calibration MethodologiesSession 5 Experience with Structural Reliability5.1 Lessons Learned about Performance Realiability of Jacket Foundations Systems in Gulf of Mexico Hurricanes 5.2 Comparison of Glob
23、al Design Requirements and Failure Rates for Industry Long-term Mooring Systems5.3 Updating the Foundation Strength of the Jacket Structures in a Benign Tropical EnvironmentSession 6 Reliability Methods6.1 Development of API RP 2A-LRFD 2nd Edition6.2 Earthquake Reliability of Onshore Structures and
24、Comparison to Offshore Structures6.3 Reliability Application in Arctic Codes and StandardsKeynote 3A Forward Looking Vision for Offshore Structural ReliabilitySession 7 Industry Trends7.1 Methodology for Developing Acceptance Criteria for Storm Hazards for Offshore Structures - Adopting Current Seis
25、mic Methodologies7.2 Methodology for Developing Acceptance Criteria for Storm Hazards for Offshore Structures - Using Storm Hazard Curves7.3 Examination of FPSO Safety Factors using Storm Hazard CurvesSession 8 Response-based Statistics1Proceedings of the Offshore Structural Reliability Conference 2
26、014 OSRC September 16-18, 2014, Houston, Texas, USA Keynote Paper 1 History behind the development of Limit State (LRFD) Offshore Structures Design Standards Richard Snell Oxford University England, UK ABSTRACT The manner in which reliability is applied to structural engineering is different from mo
27、st other forms of engineering. Other engineering disciplines tend to consider reliability in the context of the performance of many thousands of identical precision made components where physical and performance tests can be used to quantify product reliability. Structures, which may involve many th
28、ousands of tonnes of material and site assembly, are not identical and cannot normally be physically tested on completion. Reliability is therefore addressed in the design and fabrication standards. This paper addresses the early development of structural reliability as a concept, initial applicatio
29、ns to standards development and how it has been incorporated in the International Standards Orgainisation (ISO) Offshore Structures Standard. Offshore Structures designed and fabricated to current standards have in general a satisfactory reliability. An overview of where the industry is in terms of
30、reliability is provided. INTRODUCTION The oil industry has built platforms offshore since 1947. Initially they were in very shallow water using dock piling technology. As they extended out into deeper water tubular jacket structures evolved. The oil first industry specific offshore structures design
31、 recommended practice API RP 2A was developed in the early 1970s by the American Petroleum Institute (API) focusing on the US Gulf of Mexico. This RP has been actively developed with 20 further editions published up to the mid 1990s. Although written primarily for application to US waters it has bee
32、n applied extensively to offshore structures design worldwide. With the discovery of oil and gas in the harsh waters of NW Europe other national practices and standards in the UK and Norway were developed reflecting the specific needs of this region. Initially the objective of the oil industry stand
33、ards was to address the key design issues such as marine loading, tubular joint design, fatigue, materials selection and fabrication tolerances with a conceptually very simple single WSD load factor. This resulted in an inconsistency in reliability depending on the accuracy with which the extreme ma
34、rine load can be predicted and the ratio of the live load to the self-weight of the platform. The industry is now in the process of migrating to the slightly less simple but more consistent limit state (also LRFD) method for specifying load factors. The oil industry has been behind other structural
35、sectors in applying reliability based design. It is fast catching up. This paper outlines some of the history of the development of reliability based structural design standards and the adoption of them by the oil industry. HISTORY OF STRUCTURAL STANDARDISATION The development of standards in struct
36、ural design has been a very long term process. Early examples of standardisation tended to be in the sphere of military engineering. The Romans had a systemised process operated by a corps of military Keynote 1 - Paper2 engineers for building forts, roads and bridges with variations in standardised
37、design according to the duration of use. An early application of the reliability concept. The Persian King Xerses had sufficient confidence in his military engineering organisation to have ordered it to build a temporary bridge across the Hellespont (Dardanelles) which comprised some 676 identical l
38、inked hulls. Chinese military engineers built the Great Wall to a standardised approach to provide long term protection for their civilisation from the Mongols. Individual ancient civilisations built religious and civic structures in stone in many places around the world. Some such as the Egyptian a
39、nd Mayan pyramids had a degree of standardisation. Others were unique. The durability of these ancient stone structures is a source of wonder to many archaeologists and historians but is not to an engineer. Stone material that had been chemically stable and subject to high compressive forces for mil
40、lions of years was quarried and re-shaped to function in a largely compressive mode. The structures subsequently survived with minimal maintenance for a further few thousand years. Failures have primarily arisen from weathering, removal of material for use in later buildings, conflict and in specifi
41、c regions seismic action rather than classical overload. Much of the ancient civic and domestic built environment used materials that are not generally highly durable, mud, brick and wood. Failures arose from poor construction, inadequate foundation, fire, earthquake and conflict as well as classica
42、l overload. The design attention tended to focus on the decorative rather than structural capability. Over centuries an improved understanding of materials allowed a reduction in conservatism without a reduction in safety. Perhaps the first time that the capability of materials was deliberately stre
43、tched was in the construction of cathedrals in Europe. The great cathedrals were intended to be awe inspiring and were built, often over a period of 100+ years, by masons who observed how the structure performed as it was being built and, if necessary, applied corrections as the building progressed.
44、 They deliberately pushed the bounds of materials and knowledge and sometimes exceeded it. Local structural failures were not uncommon during the construction process. Fortunately most were built in zones of very low seismicity. They produced drawings of their structural details which were available
45、 as guidance to others building later structures. Bridges were the other area where early engineers were forced to extrapolate knowledge and precedent to achieve longer spans. Masonry arch bridges are inherently tolerant of high loads and foundation settlement. The reliability of arch bridges was fi
46、rst documented in a paper written in 1801 (ref 1). Failures arising from scour undermining the foundations were more prevalent than structural overload. The industrial age introducing iron as a construction material accelerated the process of consideration of factors of safety for appropriate reliab
47、ility. The application of cast iron in beams and columns in factories and warehouses and wrought iron chain in suspension bridges was accompanied by early scientific papers providing guidance on aspects of reliability. (refs 2, 3, 4) DEVELOPMENT OF RELIABILITY BASED DESIGN PRINCIPLES The principles
48、of structural reliability as we understand them today were first evolved in the late 1930s. A M Freundenthal at Columbia University was working in this field for civil engineering structures in 1936. A G Pugsley at Bristol University applied the principles of structural reliability to aircraft struc
49、tures in 1942. These two published the first papers that outline the concept as it is currently understood. Freundenthal in 1947 published “The safety of structures” (ref 5). Pugsley in 1951 published “Concepts of safety in Structural Engineering” (ref 6). Both of these authors were strongly of the opinion that structural engineers knowledge of the reliability of structures lags far behind their ability to undertake complex analysis. Both viewed the key need to be improved statistical understanding of the loads to which structures are subject. In a 1956 American Society of C
