Reliability-Based Load and Resistance Factors Design for Offshore Jacket Platforms in the Bohai Bay： Calibration on Target Reliability Index

The target reliability index has been effectively used as the best solution to deal with the relationship between the structural safety and the optimal economy in any structural design.However,the target reliability index for offshore jacket platforms based on different sea areas in China has never been calibrated.This paper presents an approach for its calibration,and suggests many kinds of associated load cases.The uncertainties of loads and structural resistance are mainly investigated.The target reliability index for structural components,tubular joints and piles of offshore jacket platforms are discussed respectively in detail.Finally,through the calibrated results from the offshore jacket platforms of QK18-1,JZ20-2,SZ36-1 and BZ28-1 in the Bohai Bay,it is proposed to adopt 2.8 as the target reliability index of offshore jacket platforms in the Bohai Bay for a 25-year design period.The results provide significant reference for the design of offshore jacket platforms.     

Study of Partial Coefficients for Design of Semicircular Breakwaters

In the present study,the reliability design of semicircular breakwater is based on the verification of the rules defined by standard specifications,where partial coefficients are introduced to ensure safety.The reliability of the semicircular breakwaters has been analyzed by using the Hasofer-Lind method to determine the reliability index of structure that has correlated loads,utilizing the long-term observed wave data at a given place.The relation curve between reliability index and safety factor in the traditional design method,as well as the relationships between reliability index and partial coefficients,have been obtained.This paper proposes values of partial coefficients for the design expression of semicircular breakwaters in the cases of anti-sliding and anti-overturning.     

Numerical Analysis of Factors Influencing Implosion

-By using gas-liquid two-phase flow theory, a modified mathematical model based on the computational fluid dynamics method SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) is introduced to investigate implosion phenomena in high pressure chambers systematically. A theoretical simulation-prediction method, which is independent of experimental data, is developed in the paper and great improvement has been made on the topic. In the paper, various implosion situations have been simulated and predicted. Effects of a series of factors influencing implosion results and methods of reducing implosion danger have been analysed. The analysis results are of importance to underwater engineering practice.     

Stability Design System of Submarine Pipelines

This paper introduces a stability design system of submarine pipelines. The system can provide a reasonable design procedure for users with reference to domestic and foreign methods and in the light of home engineering experience.     

Design of Distorted Wave Protection Armor Units

In consideration of the global optimization for engineering projects, a group of calculation formulas have been derived by means of theoretical derivation and model tests. On this basis, a design procedure for the distorted units is proposed, by means of which the distorted units of an anology shape and an identical porosity ratio with the original units can be obtained after conducting a distorted enlargement and a normal contraction. The stability waveheight and stability factor of the distorted unit can be calculated with the enlargement factor, a, of the horizontal dimension of the distorted unit, or with the contraction scale, A , of the contracted distorted unit. As a result, the stability of the armor unit can be significantly improved without increasing the quantity of concrete. For the same wave met by the original units, the thickness of placement of the contracted distorted unit can be obviously reduced, thus, a large quantity of concrete can be saved, consequently, economic benefit can be achieved.     

Optimum Design for Offshore Platform Structural Reliability

In this paper, the main problems concerning reliability design of offshore platform structure are described and the general steps for the use of Safety Coefficient Method are presented.     

Reliability-Based Design for Jacket Platform Under Extreme Loads

In this paper, reliability analysis for the offshore jacket platform with the interaction of structure- pile- soil under extreme environmental loads is carried out. The inherent uncertainties of the environmental load, foundation soil, platform itself, and calculating models are evaluated. The action of extreme loads on the offshore platform is modeled as a function of extreme wave height. The system capacity of the whole platform is determined by nonlinear pushover analysis, and the relevant probability property is obtained by the simulation method. The reliability model for the whole jacket platform is described as the relationship between the load and resistance based on the offshore design codes. The reliability of whole platform is calculated by the analytical method and the importance sampling method on the basis of a case study for a tripod jacket platform.     

Design Methods for Geotextile Tubes Application in Dike Construction

The technique of geotextile tubes used to construct dikes for land reclamation has been widely used. The tubes are usually filled with slun＇y of soil, such as sand, silt or clay. The tensile stress developed in the geotextile during filling the tube is the dominant factor for construction of a safe dike. The existing design methods are good for designing sausage shaped tubes and can not be directly applied for designing fiat tubes, which are commonly used in dike construction. This paper presents a procedure that can detenmine the relatiorrship among the tube size, the pumping pressure, the unit weight of the slurry, and the tensile stress developed in the geotextile during the tube filing. When the tubes are piling up to form the dike, the tubes in the bottom will sustain the load from the weight of the upper ones. A procedure is also developed to calculate the changes of the mechanical and geometrical behavior of the tubes under the load with a similar method. All these approaches have been programmed, which can help dike designers to select the suitable geotextile and determine the profile of the dike.     

Reliability-Based Optimal Design for Very Large Floating Structure

1 .ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅａｐｐｒａｉｓａｌｏｆａｇｏｏｄｄｅｓｉｇｎｆｏｒａｖｅｒｙｌａｒｇｅｆｌｏａｔｉｎｇｓｔｒｕｃｔｕｒｅ(ＶＬＦＳ)ｔｈａｔｗｉｌｌｓｅｒｖｅｉｎａｓｐｅｃｉ ｆｉｅｄｏｃｅａｎａｒｅａｒｅｑｕｉｒｅｓｔｈａｔｔｈｅｓｔｒｕｃｔｕｒａｌｓｙｓｔｅｍｂｅｅｃｏｎｏｍｉｃａｌｌｙｄｅｓｉｇｎｅｄ ,ｔｈｅｒｅｑｕｉｒｅｍｅｎｔｓｆｏｒｉｔｓｆｕｎｃｔｉｏｎｂｅｓａｔｉｓｆｉｅｄａｎｄｔｈｅｓｔｒｕｃｔｕｒｅｋｅｅｐｓｓｔａｂｌｅｉｎｉｔｓｗｈｏｌｅｓｅｒｖｉｃｅｐｅｒｉｏ…     

Design of Mooring System for Oil Storage Vessels

The floating oil storage system has been proposed as a new facility for Strategic Petroleum Reserve (SPR) in China. Mooring is one of the key technologies to ensure the safety, reliability, and performance of the oil storage system. This paper describes the concept, analysis, design and reliability of the mooring system. For mooring system design of these oil vessels, analysis is essential of the behavior of the vessel in connection with mooring facilities of nonlinear resilience. A nonlinear mathematical model for analyzing a moored vessel is established and solved. Some results of numerical simulations are presented. Assessment of the safety regarding the mooring system in terms of failure probability is carried out. Another simulation model for calculating the failure probability of the mooring system is proposed. The design parameters that have an influence on the characteristics of the failure probability have been identified. The simulation results show that the mooring system has an annual reliab     

Reliability-Based Load and Resistance Factors Design for Offshore Jacket Platforms in the Bohai Bay: Calibration on Design Factors

For the fulfillment of the probability-based structural design for the offshore jacket platforms in the Bohai Bay, the design factors of loads, resistance and load combinations are much necessary to be calibrated according to the proposed target reliability index. Firstly, the limit states function for the offshore jacket platforms is introduced. Then, four approaches to calibrate the factors of load and resistance are presented and compared. Afterwards, the methods to calibrate the load combination factors are developed. Finally, the factors of load, resistance and load combination for the offshore jacket platforms in the Bohai Bay are calibrated and the corresponding design formulae are recommended. The results are proved to be rational in practice, and also illustrate that the proposed target reliability index for offshore jacket platforms in the Bohai Bay is also appropriate.     

Calibration of LRFD Format for Steel Jacket Offshore Platform in China Offshore Area （2） ： Load, Resistance and Load Combination Factors

1.IntroductionLoad and Resistance Factor Design(LRFD)isthe commonly adoptedreliability-based designfor-mat for structural design(CNE,1990;AAHTO,1994;OMTC,1983;CMC,1984).Code calibra-tionforthe LRFDformat is a processto determinethetarget reliability by de…     

Calibration of LRFD Format for Steel Jacket Offshore Platforms in China Offshore Area （ 1 ） ： Statistical Parameters of Loads and Resistances

1 .IntroductionThe structural design method has evolvedfromthe workingstress method,damage stage methodtolimit state method.The more recent probabilisticlimit state design method,whichis based onreliabili-tytheory,has beengenerallyacceptedinthe designcode…     

Reliability-Based Load and Resistance Factors Design for Offshore Jacket Platforms in the Bohai Bay: Calibration on Target Reliability Index

The target reliability index has been effectively used as the best solution to deal with the relationship between the structural safety and the optimal economy in any structural design. However, the target reliability index for off-shore jacket platforms based on different sea areas in China has never been calibrated. This paper presents an approach for its calibration, and suggests many kinds of associated load cases. The uncertainties of loads and structural resistance are mainly investigated. The target reliability index for structural components, tubular joints and piles of offshore jacket platforms are discussed respectively in detail. Finally, through the calibrated results from the offshore jacket platforms of QK18-1, JZ20-2, SZ36-1 and BZ28-1 in the Bohai Bay, it is proposed to adopt 2.8 as the target reliability index of offshore jacket platforms in the Bohai Bay for a 25-year design period. The results provide significant reference for the design of offshore jacket platforms.     

Efficient Approximate Method of Global Reliability Analysis for Offshore Platforms in the Ice Zone

Ice load is the dominative load in the design of offshore platforms in the ice zone, and the extreme ice load is the key factor that affects the safety of platforms. The present paper studies the statistical properties of the global resistance and the extreme responses of the jacket platforms in Bahai Bay, considering the randomness of ice load, dead load, steel elastic modulus, yield strength and structural member dimensions. Then, based on the above results, an efficient approximate method of the global reliability analysis for the offshore platforms is proposed, which converts the implicit nonlinear performance function in the conventional reliability analysis to linear explicit one. Finally, numerical examples of JZ20-2 MSW, JZ20-2NW and JZ20-2 MUQ offshore jacket platforms in the Bahai Bay demonstrate the satisfying efficiency, accuracy and applicability of the proposed method.     

极端荷载作用下海洋导管架平台体系可靠度分析

采用非线性倒塌分析方法，考虑桩－土－结构的非线性相互作用，研究了导管架平台在极端荷载作用下承载能力的计算模型，分析了平台结构体系在极端荷载作用下的全倒塌全过程，在此基础上，结合蒙特卡洛法，提出了海洋导管架平台结构的体系可靠度计算方法。最后对工程实例－涠11－4C海洋平台的结构进行了体系可靠性分析，并对比分析了不同的荷载效应计算公式对计算经的影响，研究表明计算经满足工程设计要求，便于工程应用。     

海洋导管架平台的极限强度分析

海洋导管架平台的极限分析是一项较新的研究课题，随着海上采油事业的飞速发展，它已越来越受到海洋工程设计及维修部门的重视。其研究成果不仅能用于设计结构的应力校核，尚可用于现有平台结构的整体安全估算。本文利用非线性模拟技术及线性分析程序的完美结合。成功地分析计算了受集中哉茶作用的空间框架结构，及受静载荷和环境载荷作用下的真实导管架平台极限强度。     

Ultimate Strength Analysis of Offshore Jacket Platform

- The ultimate strength analysis of offshore jacket platforms is a research project which has been developed in recent years. With the rapid development of marine oil industry, the departments of design and IMR (Inspection, Maintenance and Repair) in the offshore engineering have attached great importance to this project. The research procedure applies to both the stress check of new design platforms and the whole safety assessment of existing platforms. In this paper, we combine the pseudo non-linear technique with the linear analysis program and successfully analyze the ultimate strength of the space frame structure subject to the concentrated load and a real jacket platform subject to the dead load and environmental load.