Structural Reliability Applications in Design and Maintenance Planning of Ships Subjected to Fatigue and Corrosion

2012 ◽  
Author(s):  
Marcos Corrêa Câmara ◽  
Júlio C. Ramalho Cyrino
Keyword(s):  
Reliability Index ◽  
Structural Reliability ◽  
Time Dependent ◽  
Maintenance Planning ◽  
Inspection Planning ◽  
Utilization Factor ◽  
Hull Girder ◽  
Target Reliability Index ◽  
Hull Structure ◽  
Reliability Method

This paper presents structural reliability applications in design and maintenance planning for ships hull structures. For the assessment of structural strength, the model developed consists in an ultimate limit-state of hull-girder considering degradation by corrosion based in a statistical investigation of time-variant hull girder strength made by ABS (American Bureau of Shipping) on 2007. The time dependent reliability index obtained with the minimum elastic section modulus required by the rules of the classification society American Bureau of shipping (ABS), of two ship designs are compared against the results obtained from the target reliability index based design. The target reliability index assessment for corroded hulls is also showed. The monte-carlo simulation reliability method is used to calculate the time-dependent reliability of the primary hull structure. Two approaches of fatigue and corrosion-enhanced fatigue time dependent reliability are developed. A long term stress range applied to a detail is fitted to a weibull distribution based in a known design life. A utilization factor is introduced in order to consider the fraction of time at sea. A risk-based inspection planning is discussed for commercial and naval vessels Both S-N curve and fracture mechanics based reliability methods are used and the results are compared. An example of reliability updating after a inspection result is showed.

Ship Hull Ultimate Strength Reliability Considering Corrosion

1998 ◽  
Vol 42 (02) ◽  
pp. 154-165
Author(s):  
Jeom Kee Paik ◽  
Anil K. Thayamballi ◽  
Sung Kyu Kim ◽  
Soo Hong Yang
Keyword(s):  
Ultimate Strength ◽  
Reliability Index ◽  
Failure Modes ◽  
Ship Hull ◽  
Time Dependent ◽  
General Corrosion ◽  
Wave Load ◽  
Hull Girder ◽  
Corrosion Rates ◽  
Reliability Method

The aim of the present paper is to develop and demonstrate a procedure for assessment of ship hull girder ultimate strength reliability taking into account the degradation of primary members due to general corrosion. The probabilistic model for ultimate hull girder strength is established on the basis of an analytical formula that considers corrosion related time dependent strength degradation in the various failure modes. Corrosion rates and their probabilistic characterization are based on available studies using gauging data. Applicable extreme hull girder loads are calculated using a simplified direct method for wave load calculation together with the IACS design guidance formula for stillwater bending moment. The variability in strength, corrosion rates and loads are accounted for in the second order reliability method (SORM) based on calculations of the time dependent reliability index. The procedure developed is illustrated by application to both tankers and bulk carriers. For a given set of renewal criteria, apart from trends of hull girder section modulus, ultimate strength and the reliability index as a function of vessel age, the probability of steel renewal due to corrosion is also predicted.

scholarly journals Time-Dependent Reliability Analysis of Plate-Stiffened Prismatic Pressure Vessel with Corrosion

Mathematics ◽  
2021 ◽  
Vol 9 (13) ◽  
pp. 1544
Author(s):  
Younseok Choi ◽  
Junkeon Ahn ◽  
Daejun Chang
Keyword(s):  
Reliability Analysis ◽  
Pitting Corrosion ◽  
Pressure Vessel ◽  
Reliability Index ◽  
Structural Reliability ◽  
Pressure Vessels ◽  
Outer Shell ◽  
Time Dependent ◽  
General Corrosion ◽  
Reliability Method

In this study, the structural reliability of plate-stiffened prismatic pressure vessels was analyzed over time. A reliability analysis was performed using a time-dependent structural reliability method based on the response surface method (RSM). The plate-stiffened prismatic pressure vessel had a rectangular cross-section with repeated internal load-bearing structures. For the structural analysis, this repeated structure was modeled as a strip, and a structural reliability analysis was performed to identify changes in the reliability index when general corrosion and pitting corrosion occurred in the outer shell. Pitting corrosion was assumed to be randomly distributed on the outer shell, and the reliability index according to the degree of pit (DOP) and time was analyzed. Analysis results confirmed that the change in the reliability index was larger when pitting corrosion was applied compared with when only general corrosion was applied. Additionally, it was confirmed that above a certain DOP, the reliability index was affected.

Reliability-Based Inspection of Corroded Ship-Type FPSO Hulls

2006 ◽  
Vol 50 (02) ◽  
pp. 171-180
Author(s):  
Hai-Hong Sun ◽  
C. Guedes Soares
Keyword(s):  
Ultimate Strength ◽  
Thickness Measurement ◽  
Time Dependent ◽  
Stiffened Panel ◽  
Inspection Planning ◽  
Safety Level ◽  
Buckling Strength ◽  
Hull Girder ◽  
Reliability Method ◽  
Corrosion Model

This paper proposes a time-variant probabilistic corrosion model derived from a database with 157 thickness measurement records of 140 tankers. Incorporating the corrosion model in a time-dependent reliability method and referring to a required limit of safety level, a reliability-based inspection planning is proposed for ship-type floating production, storage, and offloading units (FPSOs) based on corrosion renewal criteria that account simultaneously for thickness reduction, hull girder ultimate strength, stiffened panel buckling strength, and plate ultimate strength

scholarly journals Time-Dependent Reliability Analysis of Reinforced Concrete Beams Subjected to Uniform and Pitting Corrosion and Brittle Fracture

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1820
Author(s):  
Mohamed El Amine Ben Seghier ◽  
Behrooz Keshtegar ◽  
Hussam Mahmoud
Keyword(s):  
Reinforced Concrete ◽  
Brittle Fracture ◽  
Reliability Analysis ◽  
Pitting Corrosion ◽  
Structural Reliability ◽  
Time Dependent ◽  
State Function ◽  
Rc Beams ◽  
Highly Nonlinear ◽  
Reliability Method

Reinforced concrete (RC) beams are basic elements used in the construction of various structures and infrastructural systems. When exposed to harsh environmental conditions, the integrity of RC beams could be compromised as a result of various deterioration mechanisms. One of the most common deterioration mechanisms is the formation of different types of corrosion in the steel reinforcements of the beams, which could impact the overall reliability of the beam. Existing classical reliability analysis methods have shown unstable results when used for the assessment of highly nonlinear problems, such as corroded RC beams. To that end, the main purpose of this paper is to explore the use of a structural reliability method for the multi-state assessment of corroded RC beams. To do so, an improved reliability method, namely the three-term conjugate map (TCM) based on the first order reliability method (FORM), is used. The application of the TCM method to identify the multi-state failure of RC beams is validated against various well-known structural reliability-based FORM formulations. The limit state function (LSF) for corroded RC beams is formulated in accordance with two corrosion types, namely uniform and pitting corrosion, and with consideration of brittle fracture due to the pit-to-crack transition probability. The time-dependent reliability analyses conducted in this study are also used to assess the influence of various parameters on the resulting failure probability of the corroded beams. The results show that the nominal bar diameter, corrosion initiation rate, and the external loads have an important influence on the safety of these structures. In addition, the proposed method is shown to outperform other reliability-based FORM formulations in predicting the level of reliability in RC beams.

Non-Probabilistic Structural Reliability Model Based on Ellipsoidal-Bound Model with Restricted Expansion

2011 ◽  
Vol 230-232 ◽  
pp. 920-924
Author(s):  
Kun Feng Li ◽  
Zi Chun Yang ◽  
Gui Feng Liu
Keyword(s):  
Reliability Index ◽  
Structural Reliability ◽  
Insufficient Data ◽  
Reliability Model ◽  
Gap Model ◽  
New Model ◽  
Model Based ◽  
Information Gap ◽  
Reliability Method

When insufficient data are available, probabilistic reliability method is invalid, but the non-probabilistic reliability method based on I-G (information-gap) model is a valid alternative. The most common I-G model, ellipsoidal-bound model, has been updated in this paper by acquiring information about span restrictions of uncertainty quantities and a corresponding non-probabilistic reliability index was proposed. The method for computing the reliability index was also given. The new model can reveal the influence of the span restriction of uncertainty quantities on structural reliability.

System Reliability of Existing Jacket Platform in Malaysian Water (Failure Path and System Reliability Index)

2014 ◽  
Vol 567 ◽  
pp. 307-312 ◽  
Author(s):  
V. John Kurian ◽  
Mohamed Mubarak Abdul Wahab ◽  
T.S. Kheang ◽  
Mohd Shahir Liew
Keyword(s):  
System Reliability ◽  
Reliability Index ◽  
Structural Reliability ◽  
Pushover Analysis ◽  
Probability Of Failure ◽  
Jacket Platform ◽  
First Order ◽  
Failure Path ◽  
Reliability Method ◽  
Two Parameters

The objective of this work is to determine the structural reliability of an existing jacket platform in Malaysia, by determining the system probability of failure and its corresponding reliability index. These two parameters are important indicators for assessing the integrity and reliability of the platform, and will point out whether the platform is suitable for continued operation. In this study, pushover analysis is used to determine possible failure paths of the structure, while First Order Reliability Method (FORM) and Simple Bound Formula are used to determine the failure probability and reliability index. Three failure paths of the platform are established. The reliability index of these paths is found with the highest Reliability Indexto be 18.82 from the 315-degree path, while the system reliability index is 9.23. This illustrates that the platform is robust and the chances of collapse is very small.

Neural network approach to model the limit state surface for reliability analysis

2003 ◽  
Vol 40 (6) ◽  
pp. 1235-1244 ◽  
Author(s):  
Anthony TC Goh ◽  
Fred H Kulhawy
Keyword(s):  
Neural Network ◽  
Reliability Index ◽  
Structural Reliability ◽  
Limit State ◽  
Random Variables ◽  
First Order Reliability Method ◽  
First Order ◽  
The Neural Network ◽  
Reliability Method ◽  
Geotechnical Structures

Structural reliability methods are often used to evaluate the failure performance of geotechnical structures. A common approach is to use the first-order reliability method. Its popularity results from the mathematical simplicity of the method, since only second moment information (mean and coefficient of variation) on the random variables is required. The probability of failure is then assessed by an index known commonly as the reliability index. One critical aspect in determining the reliability index is the explicit definition of the limit state surface of the system. In a problem involving multi-dimensional random variables, the limit state surface is the boundary separating the safe domain from the "failure" (or lack of serviceability) domain. In many complicated and nonlinear problems where the analyses involve the use of numerical procedures such as the finite element method, this surface may be difficult to determine explicitly in terms of the random variables, and therefore the limit state can only be expressed implicitly rather than in a closed-form solution. It is proposed in this paper to use an artificial intelligence technique known as the back-propagation neural network algorithm to model the limit state surface. First, the failure domain is found through repeated point-by-point numerical analyses with different input values. The neural network is then trained on this set of data. Using the optimal weights of the neural network connections, it is possible to develop a mathematical expression relating the input and output variables that approximates the limit state surface. Some examples are given to illustrate the application and accuracy of the proposed approach.Key words: first-order reliability method, geotechnical structures, limit state surface, neural networks, reliability.

Structural Reliability of a Suezmax Oil Tanker Designed According to New Joint Tanker Project Rules

2006 ◽  
Author(s):  
C. Guedes Soares ◽  
Josˇko Parunov
Keyword(s):  
Structural Reliability ◽  
Progressive Collapse ◽  
Bending Moment ◽  
Single Step ◽  
Moment Capacity ◽  
Hull Girder ◽  
Term Operation ◽  
Reliability Method ◽  
Wave Induced

The paper aims at quantifying the changes in notional reliability levels that result from redesigning an existing suezmax tanker to comply with new Joint Tanker Project (JTP) rule requirement for ultimate vertical bending moment capacity. The probability of structural failure is calculated using a first-order reliability method. The evaluation of the wave-induced load effects that occur during long-term operation of the ship in the seaway is carried out in accordance to IACS recommended procedure. Comparative analysis of long-term distributions of vertical wave bending moment calculated by two independent computer seakeeping codes is performed. The still water loads are defined on the basis of a statistical analysis of loading conditions from the loading manual. The ultimate collapse bending moment of the midship cross section, which is used as the basis for the reliability formulation, is evaluated by JTP single-step procedure and by program HULLCOLL for progressive collapse analysis of ship hull-girders. The reliability assessment is performed for “as-built” and “corroded” states of the existing ship and a reinforced design configuration complying with new JTP rules. It is shown that hull-girder failure probability of suezmax tanker reinforced according to new JTP rules is reduced several times. Sensitivity analysis and a parametric study are performed to investigate the variability of results to the change of parameters of pertinent random variables within their plausible ranges.

scholarly journals DEVELOPED PROBABILISTIC REDUCTION FACTORS FOR LOPHIRA ALATA (EKKI) TIMBER JOISTS SUBJECTED TO CREEP-RUPTURE

2016 ◽  
Vol 36 (1) ◽  
pp. 39-44
Author(s):  
JM Kaura ◽  
A Lawan ◽  
AA Salihu
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Significant Loss ◽  
Creep Rupture ◽  
Time Dependent ◽  
Load Duration ◽  
Design Variables ◽  
Reliability Method ◽  
Load Carrying ◽  
Strength And Stiffness

Wood experiences a significant loss of strength and stiffness when loaded over period of time. This phenomenon is known as creep-rupture. Several models were developed for the estimation of the reduction of load carrying capacity of timber with time. In this paper, the results of time dependent structural reliability analysis of timber joist produced with Lophiraalata (Ekki) timber specie was presented. Three load duration models were considered in the study, namely: The Model proposed by Wood, Gerhards model, and Nielsen. The timber joist was designed in accordance with the Eurocode 5. The uncertainties in all the basic design variables were fully accommodated in the time dependent reliability analysis. The entire process was implemented using a developed MATLAB program employing First Order Reliability Method (FORM). Time dependent mathematical models for modification of safety index to account for the effect of load duration were proposed. The use of both Gerhards and Nielsen model, for the design of Lophiraalata timber members was recommended.  http://dx.doi.org/10.4314/njt.v36i1.6

Study of Computation for Structural Reliability Index Based on Penalty Function Method

2014 ◽  
Vol 635-637 ◽  
pp. 443-446 ◽  
Author(s):  
Hai Tao Lu ◽  
Yu Ge Dong ◽  
Fang Ying Wu
Keyword(s):  
Unconstrained Optimization ◽  
Penalty Function ◽  
Reliability Index ◽  
Function Method ◽  
Structural Reliability ◽  
Limit State ◽  
State Function ◽  
Penalty Function Method ◽  
Design Point ◽  
Reliability Method

According to the geometric meaning of the structural reliability index, an unconstrained optimization model with structural reliability index and design point is obtained by exterior penalty function method. The Powell method, golden section method and extrapolation method are used to solve the unconstrained optimization problem. The proposed method not has to deal with the any derivative of the limited state function, and can been used to obtain structural reliability index and design point of the strong nonlinear limit state function, which first-order reliability method (FORM) may fail to converge. Three examples are given to compare penalty function method with the difference methods. The results show that the given method is simply, effective and precise enough.

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