scholarly journals Influence of Uncertain Factor in Breakwater Design to Encounter Probability of Failure

1997 ◽  
Vol 13 ◽  
pp. 579-584 ◽  
Author(s):  
Hiroyasu KAWAI ◽  
Tetsuya HIRAISHI ◽  
Tsunehiro SEKIMOTO
Keyword(s):  
Probability Of Failure ◽  
Encounter Probability ◽  
Uncertain Factor

Evaluation of Residual Life of Existing Offshore Platforms in Western Offshore, India

2021 ◽  
Author(s):  
A. Renugadevi ◽  
S. Nallayarasu ◽  
S. Karunanithi
Keyword(s):  
Residual Life ◽  
Probability Of Failure ◽  
Oil Field ◽  
Life Extension ◽  
Offshore Platforms ◽  
Strength Assessment ◽  
Encounter Probability ◽  
Reliability Method ◽  
Reserve Strength ◽  
Extension Period

Abstract Western offshore oil field in India has nearly 300 offshore platforms for oil and gas exploration, of which almost 50% of platforms have outlived their life. Life extension of these platforms has become essential for further production activities. In many cases, design level analyses combined with ultimate strength assessment, life extension has been granted. However, risk-based assessment based on the probability of failure based on available reserve strength linked to additional life extension could be a logical method. The Reserve Strength Ratio (RSR) is defined as a ratio of reserve capacity of the jacket structure and the design level environmental loads (1 year or 5year or 10 year or 100-year return period). The encounter probability of these design storms for the life extension period has been established probability for the extension period has been used as a threshold to determining the required RSR using the probability of collapse. For the present study, four typical aged wellhead platforms with different water depths are selected, and RSR is evaluated by carrying out push over analysis. The Monte Carlo Simulation method is used to generate the statistical values of RSR. The probability of failure is then calculated by First Order Reliability Method (FORM) using MATLAB for different RSR values. Reassessment criteria for the existing offshore platforms have been described from the reliability analysis results based on probability failure and encounter probability.

scholarly journals Bridge Safety Analysis Based on the Function of Exceptional Vehicle Transit Speed

2020 ◽  
Vol 14 (1) ◽  
pp. 222-236
Author(s):  
Roberto Ventura ◽  
Benedetto Barabino ◽  
David Vetturi ◽  
Giulio Maternini
Keyword(s):  
Real Data ◽  
Probability Of Failure ◽  
Dynamic Effects ◽  
Encounter Probability ◽  
The Road ◽  
Optimal Speed ◽  
Bridge Safety ◽  
Annual Probability ◽  
Transit Speed ◽  
Bridge Bearing

Background: The road management agencies often prescribe very low-speed limits for exceptional vehicles transiting on the deck. These restrictions aim to reduce the dynamic effects due to the vehicle-bridge interaction because it is assumed that these effects increase with speed. However, sometimes, a reduction in speed increases the encounter probability of two exceptional vehicles travelling in opposite directions and this could compromise the safety of the bridge when the total masses of both vehicles exceed the bridge bearing capacity (or limit mass). Objective: While the literature has investigated the encounter probability in a theoretical way and has investigated the vehicle-bridge interaction, especially in terms of dynamic load increment, to the best of our knowledge, no study has investigated the conjunction probability of encounters and of exceeding the limit mass also by using real data. This paper aims to cover this gap by proposing an integrated model that computes the “Annual Probability of Failure” of the bridge, defined as the likelihood to exceed the “Limit Mass" of the deck when two opposite exceptional vehicles encounter. Methods: According to the probability theory, the “Annual Probability of Failure” can be obtained by multiplying the likelihood that during the reference year, at least once, two exceptional vehicles, travelling in two opposite directions (ascendant and descendant), will be simultaneously on the bridge deck (“Annual probability of encounter”) with the likelihood that the sum of the single masses of two exceptional vehicles randomly extracted from the sample, including the dynamic effects, exceeds the limit mass ml (“Probability of exceeding the limit mass”). Results: The results show that the probability of encounter increases with both the exceptional vehicles flow rate and the length of the span, whereas it decreases with the passing speed. The probability of exceeding the limit mass increases with speed. Nevertheless, by combining both the probabilities, these results suggest the existence of an “Optimal Speed”, which minimizes the “Annual Probability of Failure”. Conclusion: The existence of an “Optimal Speed” should be considered when defining the exceptional vehicle transit rules on bridges as well as the speed limit.

STOCHASTIC CALCULATION OF LIFETIME PREDICTION FOR COMPONENTS IN METAL STRUCTURES DUE TO THE GROWTH OF MICRODEFECTS

2020 ◽  
Vol 4 (97) ◽  
pp. 69-76
Author(s):  
IGOR N. SILVERSTOV
Keyword(s):  
Fatigue Strength ◽  
Fracture Mechanics ◽  
Stochastic Approach ◽  
Fatigue Curve ◽  
Probability Of Failure ◽  
Lifetime Prediction ◽  
Statistical Distributions ◽  
Metal Structures

A stochastic approach has been developed to evaluate fatigue strength using elements of the fracture mechanics. The article presents a method for determining the initial parameters of statistical distributions. It also considers the method for constructing a fatigue curve for a component of any size and configuration with any given probability of failure.

Vulnerability-Based Design of Sliding Concave Bearings for the Seismic Isolation of Steel Storage Tanks

2016 ◽  
Author(s):  
Hoang Nam Phan ◽  
Fabrizio Paolacci ◽  
Silvia Alessandri ◽  
Phuong Hoa Hoang
Keyword(s):  
Liquid Steel ◽  
Seismic Isolation ◽  
Failure Modes ◽  
Fragility Curves ◽  
Time History ◽  
Probability Of Failure ◽  
Design Parameters ◽  
Economic Losses ◽  
Storage Tanks ◽  
Isolation System

Liquid steel storage tanks are strategic structures for industrial facilities and have been widely used both in nuclear and non-nuclear power plants. Typical damage to tanks occurred during past earthquakes such as cracking at the bottom plate, elastic or elastoplastic buckling of the tank wall, failure of the ground anchorage system, and sloshing damage around the roof, etc. Due to their potential and substantial economic losses as well as environmental hazards, implementations of seismic isolation and energy dissipation systems have been recently extended to liquid storage tanks. Although the benefits of seismic isolation systems have been well known in reducing seismic demands of tanks; however, these benefits have been rarely investigated in literature in terms of reduction in the probability of failure. In this paper, A vulnerability-based design approach of a sliding concave bearing system for an existing elevated liquid steel storage tank is presented by evaluating the probability of exceeding specific limit states. Firstly, nonlinear time history analyses of a three-dimensional stick model for the examined case study are performed using a set of ground motion records. Fragility curves of different failure modes of the tank are then obtained by the well-known cloud method. In the following, a seismic isolation system based on concave sliding bearings is proposed. The effectiveness of the isolation system in mitigating the seismic response of the tank is investigated by means of fragility curves. Finally, an optimization of design parameters for sliding concave bearings is determined based on the reduction of the tank vulnerability or the probability of failure.

A Review of Crack Detection In-Line Inspection Case Studies

2010 ◽  
Author(s):  
Neil Bates ◽  
David Lee ◽  
Clifford Maier
Keyword(s):  
Crack Growth ◽  
Case Studies ◽  
Crack Detection ◽  
Growth Parameters ◽  
Probability Distributions ◽  
Low Frequency ◽  
Probability Of Failure ◽  
Probability Of Detection ◽  
Inspection Data

This paper describes case studies involving crack detection in-line inspections and fitness for service assessments that were performed based on the inspection data. The assessments were used to evaluate the immediate integrity of the pipeline based on the reported features and the long-term integrity of the pipeline based on excavation data and probabilistic SCC and fatigue crack growth simulations. Two different case studies are analyzed, which illustrate how the data from an ultrasonic crack tool inspection was used to assess threats such as low frequency electrical resistance weld seam defects and stress corrosion cracking. Specific issues, such as probability of detection/identification and the length/depth accuracy of the tool, were evaluated to determine the suitability of the tool to accurately classify and size different types of defects. The long term assessment is based on the Monte Carlo method [1], where the material properties, pipeline details, crack growth parameters, and feature dimensions are randomly selected from certain specified probability distributions to determine the probability of failure versus time for the pipeline segment. The distributions of unreported crack-related features from the excavation program are used to distribute unreported features along the pipeline. Simulated crack growth by fatigue, SCC, or a combination of the two is performed until failure by either leak or rupture is predicted. The probability of failure calculation is performed through a number of crack growth simulations for each of the reported and unreported features and tallying their respective remaining lives. The results of the probabilistic analysis were used to determine the most effective and economical means of remediation by identifying areas or crack mechanisms that contribute most to the probability of failure.

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