Pushover Load Factors for Fixed Steel Platforms Sensitive to Topside Load and Wave-in-Deck Load

2015 ◽  
Author(s):  
Ramsay Fraser ◽  
Mark Manzocchi ◽  
Richard Gibson
Keyword(s):  
Structural Reliability ◽  
Structural Integrity ◽  
Load Capacity ◽  
Extreme Environments ◽  
Assessment Method ◽  
Assessment Methods ◽  
Performance Criteria ◽  
Reliability Model ◽  
Load Factors ◽  
Jacket Structures

The objective of this paper is to present recent work in the development of a method for the strength assessment of offshore jacket structures subject to storm loading that is consistent across all global offshore regions. Recent developments in the application of response based metocean analysis together with the establishment of a standardized structural reliability model has resulted in an assessment method that can be applied in a consistent manner to all fixed jacket structures in all global regions. Applying this method in the “assessment” stage of the SIM process, as published by API and ISO, would aid global standardization of both the assessment methods and the performance criteria. The assessment methods have evolved over the last 3 years and have been subject to application and testing on several projects involving the assessment of existing offshore jacket structures. They have proven to be capable of discriminating between the differing extreme environments and differing evacuation and unmanning procedures that occur in different regions while being compatible with existing approaches to structural integrity. The paper will describe the standardized structural reliability model and provide examples of load factors for pushover and pushdown analysis for fixed steel offshore platforms that have a storm load capacity that is sensitivity to topside load and wave-in-deck load.

Risk Based Structural Integrity Management Using Bayesian Probabilistic Nets

2006 ◽  
Author(s):  
Roberto Montes-Iturrizaga ◽  
Ernesto Heredia-Zavoni ◽  
Enrique Marcial-Marti´nez ◽  
Michael Havbro Faber ◽  
Daniel Straub ◽  
...  
Keyword(s):  
General Framework ◽  
Structural Reliability ◽  
Structural Integrity ◽  
Suggested Approach ◽  
Annual Probability ◽  
Damage States ◽  
Jacket Structures ◽  
Integrity Management ◽  
Joint Consideration ◽  
Damage Processes

The present paper presents a general framework for integrity management of offshore steel jacket structures allowing for the risk based planning of inspections and maintenance activities with a joint consideration of all relevant deterioration and damage processes. The basic idea behind the suggested approach is to relate the relevant deterioration and damage processes, i.e. the exposure events, to damage states which in turn may be related to the overall integrity of the jacket structural system as measured through the Reserve Strength Ratio (RSR). This facilitates that any state of degradation, irrespective of the cause, can be assessed in terms of their impact on the annual probability of failure for the structure. Taking basis in data as well as subjective information regarding the annual occurrence probabilities of the relevant deterioration and damage processes, together with a probabilistic modeling of the quality of condition control, it is possible to assess the effect of condition control of each type of deterioration and damage phenomena. This then facilitates the development of a general framework for risk based integrity management. In the present work such a framework is formulated using Bayesian Probabilistic Nets (BPN) for evaluating the time varying global structural reliability of jackets subject to progressive deterioration of its members due to the combined effect of different sources of damage.

Structural Reliability Analysis of Loading Platform Cantilever under Multiple Failure Modes

2010 ◽  
Vol 102-104 ◽  
pp. 204-209 ◽  
Author(s):  
Rui Jun Zhang ◽  
Min Li ◽  
Min Qin Zhang ◽  
Xiao Wei Wang
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Failure Modes ◽  
Load Capacity ◽  
Limit State ◽  
Second Order ◽  
Main Beam ◽  
Order Moment ◽  
Reliability Model ◽  
Multiple Failure Modes

Force behaviors of the loading platform of rotating stereo garages is analyzed, equations describing the load capacity and the deformation limit state are proposed for the key sections by applying the second-order moment into the reliability analysis of the main beam. Considering random parameters subject to normal distribution, a reliability model of the main beam of the loading platform is set up based on multiple failure modes and the reliability is analyzed and calculated by using second-order moment. Simulation results show that the reliability model is significant to guide designing on the reliability of rotating stereo garages and improves rotating stereo garages.

A Comparison of Fracture Assessment Methods in Several Structural Integrity Assessment Procedures

2009 ◽  
Author(s):  
Tiecheng Yang ◽  
Xuedong Chen ◽  
Zhichao Fan
Keyword(s):  
Structural Integrity ◽  
Limit Load ◽  
Assessment Method ◽  
Assessment Methods ◽  
Safety Factors ◽  
Specific Calculation ◽  
Integrity Assessment ◽  
Fracture Assessment ◽  
Partial Safety Factors ◽  
Assessment Procedures

For the fracture assessment method internationally used in different structural integrity assessment procedures, such as R6, BS 7910, FITNET API 579 and GB/T 19624, this paper gives the results of analytical comparisons in combination with specific calculation examples by comparing different assessment options or levels, the partial safety factors (PSFs), limit load solutions, stress intensity factor solutions, residual stress distribution and treatment methods, secondary stresses and ρ factor solutions etc., which provide a basis for improvement of fracture assessment methods.

The Effects of Stress Redistribution Due to Member Failure on Structural Reliability of Offshore Steel Jackets

2002 ◽  
Author(s):  
A. Nelson ◽  
D. J. Sanderson ◽  
A. Stacey
Keyword(s):  
Structural Reliability ◽  
Structural Integrity ◽  
Stress Redistribution ◽  
Periodic Inspection ◽  
Inspection Interval ◽  
Time Period ◽  
Jacket Structures ◽  
Integrity Assurance ◽  
The Impact ◽  
Inspection Schedule

Current practice in providing structural integrity assurance of North Sea Steel Jacket structures relies upon periodic inspection of the sub-structures, with FMD being the preferred method of inspection. The time period between inspections, when employing FMD is dependent upon the structure’s level of redundancy. However, little, if any, consideration is given to the effect a failed member has on the stress distribution within the structure and the probability of a second member failing. A study has been completed that investigated the impact of stress redistribution following failure of a member. The study has considered the impact this has on fatigue lives of adjacent members/joints, and ultimately the impact on structural reliability. The findings from this study suggest that for the type of structures considered, the justification for a given inspection schedule should take due account of the impact of stress redistribution and the possibility that a structure might experience a second member failure during an inspection interval.

Structural Reliability Assessment of Offshore Platforms Under Hurricane Events

2007 ◽  
Author(s):  
Liangsheng Wang ◽  
Kaisheng Chen ◽  
Justin Bucknell
Keyword(s):  
Structural Reliability ◽  
Structural Integrity ◽  
Limit State ◽  
Reliability Assessment ◽  
Assessment Method ◽  
Environmental Data ◽  
State Function ◽  
Offshore Platforms ◽  
Wave Load ◽  
Reliability Method

This paper presents a structural reliability assessment method to quantify the probability of platform failure for Trinidad offshore platforms subjected to hurricane events. Platforms are modeled as a series system composed of the topsides and jacket including foundation. The platform failure limit state function is defined in terms of environmental load and platform capacity. The platform capacity is evaluated by non-linear pushover analysis using USFOS program. A parametric relationship of wave load as a function of wave height is derived based on the offshore extreme environmental data. The first order reliability method (FORM) is used to estimate the annual failure probability. The relationship between the probability of platform failure and the reserve strength ratio (RSR) of platforms is investigated. The assessment results could be used to evaluate the level of risk associated with hurricane hazards and may be incorporated into the risk-based underwater inspection (RBUI) program as part of the structural integrity management (SIM) process.

scholarly journals Code Calibration of the Eurocodes

2021 ◽  
Vol 11 (12) ◽  
pp. 5474
Author(s):  
Tuomo Poutanen
Keyword(s):  
High Reliability ◽  
High Accuracy ◽  
Variable Load ◽  
Reliability Model ◽  
Safety Factors ◽  
Rounding Errors ◽  
Code Calibration ◽  
Load Factors ◽  
Characteristic Values

This article addresses the process to optimally select safety factors and characteristic values for the Eurocodes. Five amendments to the present codes are proposed: (1) The load factors are fixed, γG = γQ, by making the characteristic load of the variable load changeable, it simplifies the codes and lessens the calculation work. (2) Currently, the characteristic load of the variable load is the same for all variable loads. It creates excess safety and material waste for the variable loads with low variation. This deficiency can be avoided by applying the same amendment as above. (3) Various materials fit with different accuracy in the reliability model. This article explains two options to reduce this difficulty. (4) A method to avoid rounding errors in the safety factors is explained. (5) The current safety factors are usually set by minimizing the reliability indexes regarding the target when the obtained codes include considerable safe and unsafe design cases with the variability ratio (high reliability/low) of about 1.4. The proposed three code models match the target β50 = 3.2 with high accuracy, no unsafe design cases and insignificant safe design cases with the variability ratio 1.07, 1.03 and 1.04.

A Comparison of Disease Assessment Methods for Southern Stem Rot of Peanut

2002 ◽  
Vol 29 (1) ◽  
pp. 66-71 ◽  
Author(s):  
S. L. Rideout ◽  
T. B. Brenneman ◽  
K. L. Stevenson
Keyword(s):  
Alternative Assessment ◽  
Disease Incidence ◽  
Sclerotium Rolfsii ◽  
Correlation Coefficients ◽  
Assessment Method ◽  
Assessment Methods ◽  
Alternative Methods ◽  
Stem Rot ◽  
Disease Assessment ◽  
Time Required

Abstract Southern stem rot (caused by the soilborne fungus Sclerotium rolfsii Sacc.) of peanut (Arachis hypogaea L.) traditionally has been assessed based on the percentage of infected 30.5-cm row segments, commonly referred to as disease incidence. Several alternative disease assessment methods were evaluated in four fungicide trials during the growing season (aboveground ratings) and immediately after peanut inversion (belowground ratings). Pearson's correlation coefficients compared disease assessments and yields for all trials. Across all disease assessment methods, belowground assessments at inversion showed a stronger correlation with yield than in-season aboveground assessments. Several of the alternative assessment methods showed a stronger negative correlation with yield than did the traditional disease incidence rating. However, none of the alternative methods were consistently more precise across all assessment dates and trials. There was a significant positive correlation between many of the alternative methods and the traditional disease incidence method. Furthermore, none of the alternative methods was better than the traditional method for detecting differences among fungicide treatments when subjected to ANOVA and subsequent Waller-Duncan mean separation tests (k-ratio = 100). Based on comparisons of the time required to assess disease intensity, the traditional disease assessment method was found to be the most time efficient method of those tested in this study.

scholarly journals A Practical Nonprobabilistic Reliability Assessment Method on Key Strata Shear Failure in Longwall Mining

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Hebing Luan ◽  
Jiachen Wang ◽  
Guowei Ma ◽  
Ke Zhang
Keyword(s):  
Structural Reliability ◽  
Shear Failure ◽  
Longwall Mining ◽  
Reliability Assessment ◽  
Friction Angle ◽  
Assessment Method ◽  
Mechanical Tests ◽  
Potential Hazard ◽  
Support Design ◽  
Key Strata

Roof cutting has long been a potential hazard factor in longwall panels in some diggings in China. Meanwhile, the key strata structural reliability, which provides an assessment on the stability of overlying roof strata, may be a significant reference for support design in underground coal mines. This paper aims to investigate a practical nonprobabilistic reliability assessment method on key strata. The mechanical tests and the hollow inclusion triaxial strain tests were conducted to measure relevant mechanical parameters and in situ stress. Furthermore, against the typical failure features in Datong Diggings, China, a shear failure mechanical model of key strata is proposed. Then, an allowable-safety-factor based nonprobabilistic stability probability assessment method is given. The sensitivity of geometrical dimensions and uncertainty levels of friction angle and cohesion are further studied. It is found that thickness and span of key strata have more dominative effect on key strata’s stability compared with the other factor and the increase of uncertainty levels results in decrease of stability probability.

Facing extremes: archaeal surface-layer (glyco)proteins

Microbiology ◽  
2003 ◽  
Vol 149 (12) ◽  
pp. 3347-3351 ◽  
Author(s):  
Jerry Eichler
Keyword(s):  
Surface Layer ◽  
Structural Integrity ◽  
Elevated Temperatures ◽  
Protein Biosynthesis ◽  
Extreme Environments ◽  
Archaeal Protein ◽  
The Face ◽  
Micro Organisms ◽  
Physical Challenges ◽  
Insight Into

Archaea are best known in their capacities as extremophiles, i.e. micro-organisms able to thrive in some of the most drastic environments on Earth. The protein-based surface layer that envelopes many archaeal strains must thus correctly assemble and maintain its structural integrity in the face of the physical challenges associated with, for instance, life in high salinity, at elevated temperatures or in acidic surroundings. Study of archaeal surface-layer (glyco)proteins has thus offered insight into the strategies employed by these proteins to survive direct contact with extreme environments, yet has also served to elucidate other aspects of archaeal protein biosynthesis, including glycosylation, lipid modification and protein export. In this mini-review, recent advances in the study of archaeal surface-layer (glyco)proteins are discussed.

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