Probabilistic Load Combination Factors of Wave and Whipping Bending Moments

2015 ◽  
Vol 59 (01) ◽  
pp. 11-30
Author(s):  
Maro Corak ◽  
Joško Parunov ◽  
C. Guedes Soares
Keyword(s):  
Extreme Values ◽  
Bending Moment ◽  
Practical Method ◽  
Time Instant ◽  
Regression Equations ◽  
Bending Moments ◽  
Short Term ◽  
Load Combination ◽  
Combination Methods ◽  
Probabilistic Load

Extreme values of wave and whipping bending moments are important in structural design of large containerships. Since the extreme values of these two, partially correlated processes do not occur at the same time instant and even at the same environmental conditions, it is necessary to combine them by using probabilistic load combination methods. The correlation analysis between wave and whipping bending moments is performed and a practical method for calculation of the most probable load combination factor between considered bending moments is presented. Short-term load combination factors are calculated by reconstruction of the signal from the frequency domain solution. Results are validated by comparison with model test data of the 9400-TEU containership for various sea states and speeds and heading angles. Practical regression equations for estimation of the most probable short-term load combination factor are formulated. Regression equations are then used in the computation of the long-term distribution of combined bending moment. The procedure is demonstrated on the example of the two large containerships.

scholarly journals Method for Prediction of Extreme Wave Loads Based on Ship Operability Analysis Using Hindcast Wave Database

2021 ◽  
Vol 9 (9) ◽  
pp. 1002
Author(s):  
Tamara Petranović ◽  
Antonio Mikulić ◽  
Marko Katalinić ◽  
Maro Ćorak ◽  
Joško Parunov
Keyword(s):  
Transfer Functions ◽  
Extreme Values ◽  
Bending Moment ◽  
Ship Motions ◽  
Bending Moments ◽  
Wave Loads ◽  
Extreme Wave ◽  
Short Term ◽  
Passenger Ship ◽  
Limiting Values

The method for the prediction of extreme vertical wave bending moments on a passenger ship based on the hindcast database along the shipping route is presented. Operability analysis is performed to identify sea states when the ship is not able to normally operate and which are likely to be avoided. Closed-form expressions are used for the calculation of transfer functions of ship motions and loads. Multiple operability criteria are used and compared to the corresponding limiting values. The most probable extreme wave bending moments for the short-term sea states at discrete locations along the shipping route are calculated, and annual maximum extreme values are determined. Gumbel probability distribution is then fitted to the annual extreme values, and wave bending moments corresponding to a return period of 20 years are determined for discrete locations. The system reliability approach is used to calculate combined extreme vertical wave bending moment along the shipping route. The method is employed on the example of a passenger ship sailing across the Adriatic Sea (Split, Croatia, to Ancona, Italy). The contribution of the study is the method for the extreme values of wave loads using the hindcast wave database and accounting for ship operational restrictions.

Structural Reliability of Oil Tanker in the Adriatic Sea Damaged in Collision and Exposed to Combined Bending Moments

2018 ◽  
Author(s):  
Maro Ćorak ◽  
Joško Parunov
Keyword(s):  
Structural Reliability ◽  
Adriatic Sea ◽  
Bending Moment ◽  
State Function ◽  
Regression Equations ◽  
Bending Moments ◽  
Damage Stability ◽  
Safety Indices ◽  
Oil Tanker ◽  
Damaged Ship

The aim of the paper is the assessment of structural reliability of oil tanker which may be damaged in collision accident in the Adriatic Sea and exposed to combined, horizontal and vertical bending moments. Damage size is assumed based on the direct numerical simulation of the ship-ship collision. This is justified for some specific sea environments, as the Adriatic Sea, where ship sailing routes and representative ship types involved in accidents are known, so possible collision scenarios may be reasonably predicted. Residual bending moment capacity under combined bending moment is calculated using regression equations developed based on non-linear finite element analysis. Still water vertical bending moments are obtained by damage stability analysis. Vertical and horizontal wave bending moments are determined by short-term response analysis of damaged ship in the Adriatic Sea, using transfer functions obtained by 3D panel hydrodynamic method. Limit state function is defined using interaction equation for damaged ship exposed to combined bending moments. Safety indices are calculated by FORM for different collision scenarios that are generated by MC simulations. Such approach enables to determine the safety indices for the most frequent damages and also to reveal the most critical situations resulting in the lowest safety indices.

scholarly journals Assessment of internal pressure effect, causing additional bending of the pipeline

2020 ◽  
Vol 242 ◽  
pp. 160
Author(s):  
Ramil BAKTIZIN ◽  
Rail ZARIPOV ◽  
Gennadii KOROBKOV ◽  
Radik MASALIMOV
Keyword(s):  
Internal Pressure ◽  
Pressure Effect ◽  
Extreme Values ◽  
Bending Moment ◽  
Extreme Value ◽  
Bending Moments ◽  
Temperature Stresses ◽  
Working Pressure ◽  
Trunk Pipeline ◽  
Bending Stresses

Article justifies accounting for internal pressure effect in the pipeline, causing additional bending of the pipeline. According to some scientists, there is an erroneously used concept of the equivalent longitudinal axial force (ELAF) Sx, which depends on working pressure, temperature stresses, and joint deformations of pipelines with various types of soils. However, authors of the article use ELAF Sx concept at construction of mathematical model of stress-strain state (SSS) for complex section of the trunk pipeline, and also reveal it when analyzing the results of calculating the durability and stability of the pipeline. Analysis of SSS for calculated section of the pipeline was carried out for two statements of the problem for different values of operation parameters. In the first statement, effect of internal pressure causing bending of the pipeline is taken into account, and in the second it is neglected. It is shown that due to effect of ELAF Sx at p0 = 9.0 MPa, Dt = 29 °C extreme value of bend increases by 54 %, extreme values of bending stresses from span bending moment increase by 74 %, and extreme value of bending stresses from support bending moment double with regard to corresponding SSS characteristics of the pipeline. In case of neglecting the internal pressure effect causing additional bending of the pipeline (second statement of the problem), error in calculating the extreme value of bend is 35 %, extreme value of bending stresses from span bending moments is 44 %, and extreme value of bending stresses from support bending moments is 95 %.

Structural Reliability of Oil Tanker in the Adriatic Sea Damaged in Collision and Exposed to Combined Bending Moments

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Maro Ćorak ◽  
Joško Parunov
Keyword(s):  
Monte Carlo ◽  
Structural Reliability ◽  
Adriatic Sea ◽  
Regression Equations ◽  
Bending Moments ◽  
Load Combination ◽  
Horizontal Wave ◽  
Safety Indices ◽  
Oil Tanker ◽  
Damaged Ship

Abstract The aim of the paper is the assessment of structural reliability of oil tanker, damaged in collision accident in the Adriatic Sea and exposed to combined, horizontal, and vertical bending moments. Damage size is assumed based on the direct numerical simulation of the ship–ship collision. This is justified for some specific sea environments, as the Adriatic Sea, where ship sailing routes and representative ship types involved in accidents are known, so possible collision scenarios may be reasonably predicted. Residual bending moment capacity under combined bending moments (CBM) is calculated using regression equations developed based on non-linear finite element analysis. Still-water vertical bending moments are obtained by damage stability analysis for different collision scenarios that are generated by Monte Carlo (MC) simulations. Vertical and horizontal wave bending moments are determined by short-term response analysis of damaged ship in the Adriatic Sea, using transfer functions obtained by 3D panel hydrodynamic method. Monte Carlo time simulations are performed in order to study probabilistic load combination (LC) considering randomness of the wave process due to different phase angles. Limit state function is defined using interaction equation for damaged ship exposed to combined bending moments. Safety indices are calculated by FORM for each damage scenario by using Turkstra's rule for load combination of vertical and horizontal wave bending moments. Such an approach enables to determine the safety indices for the most frequent damages and also to reveal the most critical situations resulting in the lowest safety indices.

Influence of Whipping on Long-term Vertical Bending Moment

2004 ◽  
Vol 48 (04) ◽  
pp. 261-272
Author(s):  
Gro Sagli Baarholm ◽  
Jørgen Juncher Jensen
Keyword(s):  
Nonlinear Response ◽  
Extreme Values ◽  
Bending Moment ◽  
Sea Waves ◽  
Short Term ◽  
Strip Theory ◽  
Long Time ◽  
Wave Induced ◽  
Vertical Bending Moment

This paper is concerned with estimating the response value corresponding to a long return period, say 20 years. Time domain simulation is required to obtain the nonlinear response, and long time series are required to limit the statistical uncertainty in the simulations. It is crucial to introduce ways to improve the efficiency in the calculation. A method to determine the long-term extremes by considering only a few short-term sea states is applied. Long-term extreme values are estimated using a set of sea states that have a certain probability of occurrence, known as the contour line approach. Effect of whipping is included by assuming that the whipping and wave-induced responses are independent, but the effect of correlation of the long-term extreme value is also studied. Numerical calculations are performed using a nonlinear, hydroelastic strip theory as suggested by Xia et al (1998). Results are presented for the S-175 containership (ITTC 1983) in head sea waves. The analysis shows that whipping increases the vertical bending moment and that the correlation is significant.

Uncertainty Analysis of Load Combination Factors for Global Longitudinal Bending Moments of Double-hull Tankers

2013 ◽  
Vol 57 (01) ◽  
pp. 42-58 ◽  
Author(s):  
Angelo P. Teixeira ◽  
C. Guedes Soares ◽  
Nian-Zhong Chen ◽  
Ge Wang
Keyword(s):  
Probabilistic Models ◽  
Bending Moments ◽  
Design Rules ◽  
Load Combination ◽  
Combination Methods ◽  
Reliability Method ◽  
Longitudinal Bending ◽  
Oil Tankers ◽  
Wave Induced ◽  
Double Hull

The present article aims at assessing the probabilistic characteristics of the load combination factors for global longitudinal bending moments of double-hull tankers. The calculations are performed based on a sample of oil tankers representative of the range of application of the Association of Classification Societies' (IACS)–Common Structural Rules (CSR) design rules. The article starts by reviewing the probabilistic models that have been proposed to model stillwater and wave-induced loads and their characteristic extreme values. Different load combination methods are also reviewed including an analytical method that provides the combined characteristic value of stillwater and wave-induced bending moments based on the Poisson assumption for upcrossing events and using the first-order reliability method in combination with the point-crossing method. The predictions of the different load combination methods are assessed on the basis of a sample of five oil tankers adopted during the IACS-CSR design rules development process. A parametric and an uncertainty propagation study are then performed to identify the range of variation and the probabilistic models of the load combination factors that are applicable to double-hull tankers.

Methods of Computing the Probability of Failure Under Extreme Values of Bending Moment

1972 ◽  
Vol 16 (02) ◽  
pp. 113-123
Author(s):  
Alaa Mansour
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Extreme Values ◽  
Bending Moment ◽  
Random Variable ◽  
Probability Of Failure ◽  
Short Term ◽  
Term Analysis

Methods for predicting the probability of failure under extreme values of bending moment (primary loading only) are developed. In order to obtain an accurate estimate of the extreme values of the bending moment, order statistics are used. The wave bending moment amplitude treated as a random variable is considered to follow, in general, Weibull distribution so that the results could be used for short-term as well as long-term analysis. The probability density function of the extreme values of the wave bending moment is obtained and an estimate is made of the most probable value (that is, the mode) and other relevant statistics. The probability of exceeding a given value of wave bending moment in "n" records and during the operational lifetime of the ship is derived. Using this information, the probability of failure is obtained on the basis of an assumed normal probability density function of the resistive strength and deterministic still-water bending moment. Charts showing the relation of the parameters in a nondimensional form are presented. Examples of the use of the charts for long-term and short-term analysis for predicting extreme values of wave bending moment and the corresponding probability of failure are given.

Probabilistic Load Combination Factors of Wave and Whipping Bending Moments

2015 ◽  
Vol 59 (1) ◽  
pp. 11-30 ◽  
Author(s):  
Maro Ćorak ◽  
Joško Parunov ◽  
C. Guedes Soares
Keyword(s):  
Bending Moments ◽  
Load Combination ◽  
Probabilistic Load

Comparison of Load Combination Methods for Determining Maximum Ship’s Hull Girder Bending Moment

2014 ◽  
Vol 61 (2) ◽  
pp. 94-108 ◽  
Author(s):  
Nian-Zhong Chen ◽  
Lyuben D. Ivanov ◽  
Rachel Bashor
Keyword(s):  
Bending Moment ◽  
Hull Girder ◽  
Load Combination ◽  
Combination Methods

Doing More With Less: Pragmatic Implementation of Vancomycin Area-Under-the-Curve (AUC) Monitoring

2021 ◽  
pp. 089719002110272
Author(s):  
Joanne Huang ◽  
Jeannie D. Chan ◽  
Thu Nguyen ◽  
Rupali Jain ◽  
Zahra Kassamali Escobar
Keyword(s):  
Quality Improvement ◽  
High Risk ◽  
Therapeutic Drug Monitoring ◽  
Paradigm Shift ◽  
Area Under The Curve ◽  
Cost Effective ◽  
Practical Method ◽  
Therapeutic Drug ◽  
Short Term ◽  
Quality Improvement Process

Universal area-under-the-curve (AUC) guided vancomycin therapeutic drug monitoring (TDM) is resource-intensive, cost-prohibitive, and presents a paradigm shift that leaves institutions with the quandary of defining the preferred and most practical method for TDM. We report a step-by-step quality improvement process using 4 plan-do-study-act (PDSA) cycles to provide a framework for development of a hybrid model of trough and AUC-based vancomycin monitoring. We found trough-based monitoring a pragmatic strategy as a first-tier approach when anticipated use is short-term. AUC-guided monitoring was most impactful and cost-effective when reserved for patients with high-risk for nephrotoxicity. We encourage others to consider quality improvement tools to locally adopt AUC-based monitoring.

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