The Impact of Stress Redistribution on Structural Reliability Predictions of Deepwater Jackets

2007 ◽  
Author(s):  
Ronald Schneider ◽  
David J. Sanderson ◽  
Simon D. Thurlbeck
Keyword(s):  
Best Practice ◽  
Structural Reliability ◽  
Stress Redistribution ◽  
Correction Factors ◽  
Structural Members ◽  
Jacket Structures ◽  
Effects Of Stress ◽  
Failure Conditions ◽  
The Impact ◽  
Water Depths

Structural reliability predictions for fixed jacket structures often involve calculating the probabilities of structural members failing and the overall collapse probabilities of the jackets existing in the corresponding damaged condition. It is current best practice to consider only single member failure conditions and to ignore multi member failure conditions since the probability of more than one member failing has been considered to be negligibly small. This approach assumes that the failure of a member is in no way related to the failure of another member, which implies that the two events are statistically independent. However, in reality the two events are not statistically independent since the failure of one member changes the stress state and therefore the failure probability of the remaining members. Two studies conducted to investigate the effects of stress redistribution on platform reliability predictions concluded that, by ignoring the effects of stress redistribution, platform reliability predictions could be significantly overestimated. However, they both concentrated on shallow water jackets and consequently a further study was performed to extend the existing work on stress redistribution to consider jacket structures in greater water depths. The study considered single and dual member failure conditions and compared the effects of including and excluding stress redistribution in reliability calculations. The findings of this work suggest that including stress redistribution reduces the predicted platform reliability. From the results, generic correction factors were derived for different inspection intervals, which account for stress redistribution and dual member failure. These correction factors can be applied to the probabilities derived using current best practice to determine a more realistic estimate of a structure’s reliability.

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.

The Effect of Multiple Member Failure on the Predicted Reliability of Fixed Jacket Structures

2008 ◽  
Author(s):  
D. Sanderson ◽  
A. Nelson ◽  
A. Stacey
Keyword(s):  
Ultimate Strength ◽  
Cross Correlation ◽  
Stress Redistribution ◽  
Design Strength ◽  
Inspection Interval ◽  
Jacket Structures ◽  
Effects Of Stress ◽  
Reliability Assessments ◽  
The Individual ◽  
Large Reserve

Current offshore inspection practice relies on the detection of gross damage, such as flooded member detection. Such an inspection philosophy relies upon the structure’s ability to withstand gross damage for an inspection interval based on the large reserve factors on the jacket design strength in both the undamaged and damaged conditions. This requires a demonstration of the structure’s strength in all of the possible damaged conditions with the most critical member removed. However, the load originally carried by the critical member is redistributed to other neighbouring members which must consequently have an impact on the design fatigue lives of other members and increase the probability of more members failing. Ignoring the effects of stress redistribution due to member failure could therefore result in under-prediction of the probability of a second member failing and hence an optimistic prediction of platform reliability. This paper aims to quantify the effects of stress redistribution on the prediction of platform reliability. Stress and ultimate strength analyses were performed on three platforms in 45m water depth with bracing configurations of varying structural redundancies, namely, single diagonal, inverted K and X-braced, to calculate the stress enhancement in all members due to the individual failure of all other members. These stress enhancements were input into probabilistic fracture mechanics models to calculate the increase in failure probability of these second members due to the failure of a first member. More than 1000 pushover analyses were performed to calculate the ultimate strength of the structures in all single-member failed conditions and many hundreds of dual member failed permutations for each jacket. A cross-correlation of the most significant stress redistribution results and pushover results was used to perform platform reliability assessments. The effect of including stress redistribution and dual member pushover results was shown to reduce the predicted platform reliability for all bracing configurations, mainly due to a number of dual-member failed conditions that weakened the jackets significantly. It is recommended that, in addition to performing single member failed pushover analyses, there is a need to assess dual-member failed conditions that drastically reduce platform strength.

scholarly journals Cost-effectiveness of new MDR-TB regimens: study protocol for the TB-PRACTECAL economic evaluation substudy

BMJ Open ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. e036599
Author(s):  
Sedona Sweeney ◽  
Gabriela Gomez ◽  
Nichola Kitson ◽  
Animesh Sinha ◽  
Natalia Yatskevich ◽  
...  
Keyword(s):  
Economic Evaluation ◽  
Cost Effectiveness ◽  
Best Practice ◽  
Current Treatment ◽  
Outcome Data ◽  
London School ◽  
Main Trial ◽  
Ethical Approval ◽  
Mdr Tb ◽  
The Impact

IntroductionCurrent treatment regimens for multidrug-resistant tuberculosis (MDR-TB) are long, poorly tolerated and have poor outcomes. Furthermore, the costs of treating MDR-TB are much greater than those for treating drug-susceptible TB, both for health service and patient-incurred costs. Urgent action is needed to identify short, effective, tolerable and cheaper treatments for people with both quinolone-susceptible and quinolone-resistant MDR-TB. We present the protocol for an economic evaluation (PRACTECAL-EE substudy) alongside an ongoing clinical trial (TB-PRACTECAL) aiming to assess the costs to patients and providers of new regimens, as well as their cost-effectiveness and impact on participant poverty levels. This substudy is based on data from the three countries participating in the main trial.Methods and analysisPrimary cost data will be collected from the provider and patient perspectives, following economic best practice. We will estimate the probability that new MDR-TB regimens containing bedaquiline, pretomanid and linezolid are cost-effective from a societal perspective as compared with the standard of care for MDR-TB patients in Uzbekistan, South Africa and Belarus. Analysis uses a Markov model populated with primary cost and outcome data collected at each study site. We will also estimate the impact of new regimens on prevalence of catastrophic patient costs due to TB.Ethics and disseminationEthical approval has been obtained from the London School of Hygiene & Tropical Medicine and Médecins Sans Frontières. Local ethical approval will be sought in each study site. The results of the economic evaluation will be shared with the country health authorities and published in a peer-reviewed journal.Trial registration numberClinicalTrials.gov Registry (NCT04207112); Pre-results.

scholarly journals A new approach to radon temporal correction factor based on active environmental monitoring devices

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
T. Dicu ◽  
B. D. Burghele ◽  
M. Botoş ◽  
A. Cucoș ◽  
G. Dobrei ◽  
...  
Keyword(s):  
Radon Concentration ◽  
Residential Buildings ◽  
Indoor Radon ◽  
Smart Device ◽  
Correction Factors ◽  
Indoor Radon Concentration ◽  
Radon Measurements ◽  
The Impact ◽  
Monitoring Devices ◽  
Temporal Correction

AbstractThe present study aims to identify novel means of increasing the accuracy of the estimated annual indoor radon concentration based on the application of temporal correction factors to short-term radon measurements. The necessity of accurate and more reliable temporal correction factors is in high demand, in the present age of speed. In this sense, radon measurements were continuously carried out, using a newly developed smart device accompanied by CR-39 detectors, for one full year, in 71 residential buildings located in 5 Romanian cities. The coefficient of variation for the temporal correction factors calculated for combinations between the start month and the duration of the measurement presented a low value (less than 10%) for measurements longer than 7 months, while a variability close to 20% can be reached by measurements of up to 4 months. Results obtained by generalized estimating equations indicate that average temporal correction factors are positively associated with CO2 ratio, as well as the interaction between this parameter and the month in which the measurement took place. The impact of the indoor-outdoor temperature differences was statistically insignificant. The obtained results could represent a reference point in the elaboration of new strategies for calculating the temporal correction factors and, consequently, the reduction of the uncertainties related to the estimation of the annual indoor radon concentration.

scholarly journals Patient preferences for use of virtual consultations in an orthopaedic rehabilitation setting: Results from a discrete choice experiment

2021 ◽  
pp. 135581962110354
Author(s):  
Anthony W Gilbert ◽  
Emmanouil Mentzakis ◽  
Carl R May ◽  
Maria Stokes ◽  
Jeremy Jones
Keyword(s):  
Conceptual Model ◽  
Discrete Choice Experiment ◽  
Discrete Choice ◽  
Patient Preferences ◽  
Choice Experiment ◽  
Best Practice ◽  
Time Of Day ◽  
Problem Area ◽  
Fractional Factorial ◽  
The Impact

Objective Virtual Consultations may reduce the need for face-to-face outpatient appointments, thereby potentially reducing the cost and time involved in delivering health care. This study reports a discrete choice experiment (DCE) that identifies factors that influence patient preferences for virtual consultations in an orthopaedic rehabilitation setting. Methods Previous research from the CONNECT (Care in Orthopaedics, burdeN of treatmeNt and the Effect of Communication Technology) Project and best practice guidance informed the development of our DCE. An efficient fractional factorial design with 16 choice scenarios was created that identified all main effects and partial two-way interactions. The design was divided into two blocks of eight scenarios each, to reduce the impact of cognitive fatigue. Data analysis were conducted using binary logit regression models. Results Sixty-one paired response sets (122 subjects) were available for analysis. DCE factors (whether the therapist is known to the patient, duration of appointment, time of day) and demographic factors (patient qualifications, access to equipment, difficulty with activities, multiple health issues, travel costs) were significant predictors of preference. We estimate that a patient is less than 1% likely to prefer a virtual consultation if the patient has a degree, is without access to the equipment and software to undertake a virtual consultation, does not have difficulties with day-to-day activities, is undergoing rehabilitation for one problem area, has to pay less than £5 to travel, is having a consultation with a therapist not known to them, in 1 weeks’ time, lasting 60 minutes, at 2 pm. We have developed a simple conceptual model to explain how these factors interact to inform preference, including patients’ access to resources, context for the consultation and the requirements of the consultation. Conclusions This conceptual model provides the framework to focus attention towards factors that might influence patient preference for virtual consultations. Our model can inform the development of future technologies, trials, and qualitative work to further explore the mechanisms that influence preference.

scholarly journals Reducing environmental impacts from garments through best practice garment use and care, using the example of a Merino wool sweater

2021 ◽  
Author(s):  
Stephen G. Wiedemann ◽  
Leo Biggs ◽  
Quan V. Nguyen ◽  
Simon J. Clarke ◽  
Kirsi Laitala ◽  
...  
Keyword(s):  
Environmental Impacts ◽  
Energy Demand ◽  
Best Practice ◽  
Western Europe ◽  
Impact Category ◽  
Fashion Industry ◽  
Worst Case ◽  
Multiple Users ◽  
Washing Machines ◽  
The Impact

Abstract Purpose Garment production and use generate substantial environmental impacts, and the care and use are key determinants of cradle-to-grave impacts. The present study investigated the potential to reduce environmental impacts by applying best practices for garment care combined with increased garment use. A wool sweater is used as an example because wool garments have particular attributes that favour reduced environmental impacts in the use phase. Methods A cradle-to-grave life cycle assessment (LCA) was used to compare six plausible best and worst-case practice scenarios for use and care of a wool sweater, relative to current practices. These focussed on options available to consumers to reduce impacts, including reduced washing frequency, use of more efficient washing machines, reduced use of machine clothing dryers, garment reuse by multiple users, and increasing number of garment wears before disposal. A sixth scenario combined all options. Worst practices took the worst plausible alternative for each option investigated. Impacts were reported per wear in Western Europe for climate change, fossil energy demand, water stress and freshwater consumption. Results and discussion Washing less frequently reduced impacts by between 4 and 20%, while using more efficient washing machines at capacity reduced impacts by 1 to 6%, depending on the impact category. Reduced use of machine dryer reduced impacts by < 5% across all indicators. Reusing garments by multiple users increased life span and reduced impacts by 25–28% across all indicators. Increasing wears from 109 to 400 per garment lifespan had the largest effect, decreasing impacts by 60% to 68% depending on the impact category. Best practice care, where garment use was maximised and care practices focussed on the minimum practical requirements, resulted in a ~ 75% reduction in impacts across all indicators. Unsurprisingly, worst-case scenarios increased impacts dramatically: using the garment once before disposal increased GHG impacts over 100 times. Conclusions Wool sweaters have potential for long life and low environmental impact in use, but there are substantial differences between the best, current and worst-case scenarios. Detailed information about garment care and lifespans is needed to understand and reduce environmental impacts. Opportunities exist for consumers to rapidly and dramatically reduce these impacts. The fashion industry can facilitate this through garment design and marketing that promotes and enables long wear life and minimal care.

The Impact of Claims Management, Treatment, and Rehabilitation on Recovery and Return to Independence

2012 ◽  
Vol 7 ◽  
pp. 35-39 ◽  
Author(s):  
Liz Cairns ◽  
Maree Dyson ◽  
Sally Canobi ◽  
Nic Vipond
Keyword(s):  
Financial Performance ◽  
Best Practice ◽  
Personal Injury ◽  
Quality Information ◽  
Client Outcomes ◽  
Evaluation Program ◽  
Accident Compensation ◽  
Serious Injury ◽  
The Impact

The use of contemporaneous evaluation in personal injury insurance enables schemes to maintain and enhance their viability through access to quality information on cost, liabilities and outcomes. Best practice in research programs in the sector requires data on client outcomes and financial performance to be collected. This article presents a case study of the research and evaluation program for the National Serious Injury Service of New Zealand's Accident Compensation Corporation.

scholarly journals Impact of COVID-19 pandemic on hip fractures: the central London experience COVID-related urgent geriatric hip trauma (COUGH) study COVERT ( COVid Emergency-Related Trauma and orthopaedics) collaborative

2021 ◽  
Author(s):  
Chang Park ◽  
Kapil Sugand ◽  
Arash Aframian ◽  
Catrin Morgan ◽  
Nadia Pakroo ◽  
...  
Keyword(s):  
Best Practice ◽  
Neck Of Femur ◽  
Health Crisis ◽  
Femur Fractures ◽  
Time Period ◽  
Vulnerable Patients ◽  
Significant Difference ◽  
Usual Residence ◽  
Hip Trauma ◽  
The Impact

Abstract Introduction COVID-19 has been recognized as the unprecedented global health crisis in modern times. The purpose of this study was to assess the impact of COVID-19 on treatment of neck of femur fractures (NOFF) against the current guidelines and meeting best practice key performance indicators (KPIs) according to the National Hip Fracture Database (NHFD) in two large central London hospitals. Materials and methods A multi-center, longitudinal, retrospective, observational study of NOFF patients was performed for the first ‘golden’ month following the lockdown measures introduced in mid-March 2020. This was compared to the same time period in 2019. Results A total of 78 cases were observed. NOFFs accounted for 11% more of all acute referrals during the COVID era. There were fewer overall breaches in KPIs in time to theatre in 2020 and also for those awaiting an orthogeriatric review. Time to discharge from the trust during the pandemic was improved by 54% (p < 0.00001) but patients were 51% less likely to return to their usual residence (p = 0.007). The odds ratio was significantly higher for consultant surgeon-led operations and consultant orthogeriatric-led review in the post-COVID era. There was no significant difference in using aerosol-generating anaesthetic procedures or immortality rates between both years. Conclusion The impact of COVID-19 pandemic has not adversely affected the KPIs for the treatment of NOFF patients with significant improvement in numerous care domains. These findings may represent the efforts to ensure that these vulnerable patients are treated promptly to minimize their risks from the coronavirus.

Structural Analysis of an Offshore Jacket Model Under Seismic Excitation

2008 ◽  
Author(s):  
Helder J. D. Correia ◽  
Anto´nio C. Mendes ◽  
Carlos A. F. S. Oliveira
Keyword(s):  
Point Of View ◽  
Shaking Table ◽  
Seismic Excitation ◽  
Model Structure ◽  
Structural Members ◽  
Jacket Structures ◽  
Reaction Forces ◽  
Nodal Displacements ◽  
Good Agreement

In the present work the action of earthquakes upon offshore jacket structures is analysed by means of ADINA software. Our case-study refers to an existing model structure, previously constructed at the Laboratory of Fluid Mechanics of UBI, which has been analysed from the hydrodynamic point of view — Mendes et al. [1, 2]. The seismic excitation will be imposed at the base of this model structure, with frequencies and amplitudes corresponding to actual earthquake conditions transposed to the model scale of 1:45. The FEM software is utilised to calculate the natural frequencies of the model and to obtain stresses at selected members, as well as their nodal displacements. Our purpose is to quantify maximum stresses occurring in critical structural members and to verify the survivability criterion. The predictions of the numerical model, in terms of the reaction forces at the base and acceleration at the top of the structure, are then correlated with the experimental measurements performed when the model structure is excited in an especially designed shaking table (Correia [3]), revealing a good agreement between both results.

scholarly journals Development of a Best Practice Statement on the Use of Ankle-Foot Orthoses Following Stroke in Scotland

2010 ◽  
Vol 34 (3) ◽  
pp. 245-253 ◽  
Author(s):  
Roy Bowers ◽  
Karyn Ross
Keyword(s):  
Health Service ◽  
Working Group ◽  
Best Practice ◽  
Foot Orthoses ◽  
Ankle Foot Orthoses ◽  
Expert Working Group ◽  
Health Service Quality ◽  
The Impact ◽  
Successes And Challenges

A National Health Service Quality Improvement Scotland (NHS QIS) scoping exercise in 2007 identified the use of ankle-foot orthoses (AFOs) following stroke as a clinical improvement priority, leading to the development of a best practice statement (BPS) on AFO use after stroke. This paper outlines the development process of the BPS which is available from NHS QIS. The authors were involved as part of a working group that included practitioners from the fields of orthotics, physiotherapy, stroke nursing and bioengineering, staff of NHS QIS and a patient representative. In consultation with an NHS QIS health services researcher, the authors undertook a systematic literature review to evidence where possible the recommendations made in the BPS. Where evidence was unavailable, consensus was reached by the expert working group. As the BPS was designed for the non-specialist and non-orthotic practitioner the authors also developed educational resources which were included within the BPS to aid the understanding of the principles underpinning orthotic design and prescription. The BPS has been widely distributed throughout the health service in Scotland and is available electronically at no cost via the NHS QIS website. As part of an ongoing evaluation of the impact of the BPS on the quality of orthotic provision, NHS QIS has invited feedback regarding successes and challenges to implementation.

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