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.

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

2013 ◽  
Vol 57 (1) ◽  
pp. 42-58 ◽  
Author(s):  
Angelo P. Teixeira ◽  
C. Guedes Soares ◽  
Nian-Zhong Chen ◽  
Ge Wang
Keyword(s):  
Uncertainty Analysis ◽  
Bending Moments ◽  
Load Combination ◽  
Longitudinal Bending ◽  
Double Hull

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.

Reliability Analysis of Oil Tankers With Collision Damage

2008 ◽  
Author(s):  
Huirong Jia ◽  
Torgeir Moan
Keyword(s):  
Reliability Analysis ◽  
Load Condition ◽  
Bending Moment ◽  
Bending Moments ◽  
Load Effect ◽  
Damage Scenarios ◽  
Interaction Equation ◽  
Hydrodynamic Code ◽  
Oil Tankers ◽  
Wave Induced

This paper deals with reliability analysis of a damaged tanker conditioned upon collision damage and the damage scenarios following collision. A tanker in full load condition (FLC) and two damage sizes are considered. The ultimate strength of the damaged tanker is assessed by applying Smith’s method, and an interaction equation for vertical and horizontal bending moments (VBM and HBM) is established. The still-water bending moment is calculated by the hydrostatic code ShipShape and the 3D hydrodynamic code WASIM is employed to calculate the wave induced vertical and horizontal bending moments. Correlation between vertical and horizontal bending moments is also considered. An out-crossing rate method is adopted to estimate the failure probability for the vector load effect process, and Monte Carlo simulations are used to account for model uncertainties.

THE INFLUENCE OF CENTRE BOW LENGTH ON SLAMMING LOADS AND MOTIONS OF LARGE WAVE-PIERCING CATAMARANS

2021 ◽  
Vol 160 (A1) ◽  
Author(s):  
J R Shahraki ◽  
G A Thomas ◽  
M R Davis
Keyword(s):  
Wave Height ◽  
Full Scale ◽  
Bending Moments ◽  
Regular Waves ◽  
Large Wave ◽  
Towing Tank ◽  
Segmented Model ◽  
Model Experiments ◽  
Slamming Load ◽  
Wave Induced

The effect of various centre bow lengths on the motions and wave-induced slamming loads on wave-piercing catamarans is investigated. A 2.5 m hydroelastic segmented model was tested with three different centre bow lengths and towed in regular waves in a towing tank. Measurements were made of the model motions, slam loads and vertical bending moments in the model demi-hulls. The model experiments were carried out for a test condition equivalent to a wave height of 2.68 m and a speed of 20 knots at full scale. Bow accelerations and vertical bending moments due to slamming showed significant changes with the change in centre bow, the longest centre bow having the highest wave-induced loads and accelerations. The increased volume of displaced water which is constrained beneath the bow archways is identified as the reason for this increase in the slamming load. In contrast it was found that the length of centre bow has a relatively small effect on the heave and pitch motions in slamming conditions.

Load Combination for Fatigue Analysis of Ship Structures

2004 ◽  
Author(s):  
Yung S. Shin ◽  
Booki Kim ◽  
Alexander J. Fyfe
Keyword(s):  
Bending Moment ◽  
Linear Summation ◽  
Load Combination ◽  
Longitudinal Stiffeners ◽  
Stress Components ◽  
Tank Pressure ◽  
Wave Induced ◽  
Vertical Bending Moment ◽  
Oil Tanker

A methodology for calculating the correlation factors to combine the long-term dynamic stress components of ship structure from various loads in seas is presented. The methodology is based on a theory of a stationary ergodic narrow-banded Gaussian process. The total combined stress in short-tem sea states is expressed by linear summation of the component stresses with the corresponding combination factors. This expression is proven to be mathematically exact when applied to a single random sea. The long-term total stress is similarly expressed by linear summation of component stresses with appropriate combination factors. The stress components considered here are due to wave-induced vertical bending moment, wave-induced horizontal bending moment, external wave pressure and internal tank pressure. For application, the stress combination factors are calculated for longitudinal stiffeners in cargo and ballast tanks of a crude oil tanker at midship section. It is found that the combination factors strongly depend on wave heading and period in the short-term sea states. It is also found that the combination factors are not sensitive to the selected probability of exceedance level of the stress in the long-term sense.

Ship Operational and Safety Aspects of Ballast Water Exchange at Sea

1994 ◽  
Vol 31 (04) ◽  
pp. 315-326
Author(s):  
John B. Woodward ◽  
Michael G. Parsons ◽  
Armin W. Troesch
Keyword(s):  
Bending Moment ◽  
Bending Moments ◽  
University Of Michigan ◽  
Bulk Carrier ◽  
Rough Water ◽  
Design Values ◽  
Wave Heights ◽  
Ballast Tanks ◽  
The University ◽  
Wave Induced

A dry bulk carrier, a tanker, and a containership—taken as typical of ships trading to U.S. ports—are analyzed for possible hazards caused by emptying and refilling ballast tanks at sea. Using hydrostatic data furnished by the shipowners, hull bending moments and stabilities are investigated to find the tank-emptying operations that produce the greatest changes in those parameters. As should be expected, bending moment changes do not exceed allowable stillwater values. Changes in GM are insignificant. The worst hydrostatic cases serve as a guide to conditions that should be analyzed in rough water. The University of Michigan SHIPMO program shows that in waves of 10-ft significant height wave-induced bending moments and shears are far below the design values published by the American Bureau of Shipping. On the other hand, in waves of 20-ft significant height, the maximum wave heights that occur occasionally can cause moments or shears that exceed design values. For the 20-ft case, both linear and nonlinear versions of SHIPMO are used.

Bending Moments and Shear Forces in Ships Sailing in Irregular Waves

1981 ◽  
Vol 25 (04) ◽  
pp. 243-251
Author(s):  
J. Juncher Jensen ◽  
P. Terndrup Pedersen
Keyword(s):  
Linear Part ◽  
Vertical Motion ◽  
Bending Moment ◽  
Irregular Waves ◽  
Bending Moments ◽  
Shear Forces ◽  
Strip Theory ◽  
Wave Heights ◽  
Exciting Forces ◽  
Wave Induced

This paper presents some results concerning the vertical response of two different ships sailing in regular and irregular waves. One ship is a containership with a relatively small block coefficient and with some bow flare while the other ship is a tanker with a large block coefficient. The wave-induced loads are calculated using a second-order strip theory, derived by a perturbational procedure in which the linear part is identical to the usual strip theory. The additional quadratic terms are determined by taking into account the nonlinearities of the exiting waves, the nonvertical sides of the ship, and, finally, the variations of the hydrodynamic forces during the vertical motion of the ship. The flexibility of the hull is also taken into account. The numerical results show that for the containership a substantial increase in bending moments and shear forces is caused by the quadratic terms. The results also show that for both ships the effect of the hull flexibility (springing) is a fair increase of the variance of the wave-induced midship bending moment. For the tanker the springing is due mainly to exciting forces which are linear with respect to wave heights whereas for the containership the nonlinear exciting forces are of importance.

Extreme Response Predictions for Jack-Up Units in Second Order Stochastic Waves by FORM

2007 ◽  
Author(s):  
Jo̸rgen Juncher Jensen
Keyword(s):  
Second Order ◽  
Sea State ◽  
First Order ◽  
Reliability Method ◽  
Extreme Response ◽  
Stochastic Waves ◽  
Short Time ◽  
Wave Induced ◽  
Jack Up ◽  
Operational Time

The aim of the present paper is to advocate for a very effective stochastic procedure, based on the First Order Reliability Method (FORM), for extreme value predictions related to wave induced loads. All kinds of non-linearities can be included, as the procedure makes use of short time-domain simulations of the response in question. The procedure will be illustrated with a jack-up rig where second order stochastic waves are included in the analysis. The result is the probability of overturning as function of sea state and operational time.

Combination Factors Suitable for Semi-Probabilistic Design of Floating Production, Storage and Offloading (FPSO) Vessels

2006 ◽  
Author(s):  
Wenbo Huang ◽  
Torgeir Moan
Keyword(s):  
Probabilistic Models ◽  
Probabilistic Design ◽  
Wave Load ◽  
Load Combination ◽  
Load Effects

The paper derived new probabilistic models for still-water loads and the combined still-water and wave load effects of FPSOs. A procedure for determining load combination factors, which is suitable for semi-probabilistic and probabilistic design of FPSOs, is established. The most relevant load combination factors in harsh and benign conditions are derived.

Sign in / Sign up

Export Citation Format

Share Document