Data processing: measuring – calibrating – or testing – Measurement system – Weight
Reexamination Certificate
1999-03-11
2001-07-17
Assouad, Patrick (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Weight
Reexamination Certificate
active
06263297
ABSTRACT:
The present invention relates to a method applicable to computer programming for predicting lifetime loading of a ship hull during exposure to seawater activity, for use in structural ship hull design.
BACKGROUND OF THE INVENTION
Marine vessels are subject to overall bending loads during seawater exposure due to waves acting on the ship hull, as described in a publication entitled “Cumulative Lifetime Loadings For Naval Ships”, distributed Nov. 15-20, 1998 in Anaheim, Calif. at the 1998 exhibition symposium of the International Mechanical Engineering Congress, relating to “Unsteady Fluid Loading On Naval Structures”. A copy of such publication is submitted herewith as an Appendix and its content is incorporated herein by reference.
Bending loads imposed on marine vessels as a result of seawater activity, have been classified under two principal components acting on the hull structure, consisting of a low frequency wave-induced loading component and a high-frequency slam loading component. Bending loads are currently predicted on the basis of the low frequency component using a simplified “static balance” type of computational method predicated on the assumption of a static equilibrium position for the ship hull on a hypothetical stationary ocean wave. However, such static balance methods for predicting bending loads actually experienced by a ship hull during its lifetime, has a serious shortcoming in failing to take into account various factors, including current statistical information on the sea utilized for low frequency bending calculation and the expected operating life of the ship, as well as the impact of seawater or ocean waves on the hull, referred to as high frequency slam loading. It is therefore an important object of the present invention to address the foregoing referred to shortcomings involving incorrect predictions in bending load magnitudes that a ship may actually experience during its lifetime.
SUMMARY OF THE INVENTION
In accordance with the present invention, slam-induced bending loads imposed on a model ship hull by wave impact is computed in terms of a high frequency loading component as a function of the ship hull geometry, based on probability distribution of maximized cyclic loadings under a program to which input data is supplied by sea trial testing of the model ship. Such computed high frequency loading component is combined with the low frequency loading component heretofore obtained from the same input data by a statistical computation program based on spectral integration of a statistical description of the sea and the ship's response to the sea. Such combining of low and high frequency loading components is performed by an algorithm controlled computational program to provide a bending load prediction output as a function of its occurrence cycles. Also, the distribution of such combined bending loads along the length of the vessel is computed.
REFERENCES:
An investigation of the utility of computer simulation to predict ship structural response in waves, P. Kaplan et al. U.S. Coast Guard Headquarters, Washington, D.C. Jun. 1969.*
Load criteria for ship structural design, Edward V. Lewis et al. U.S. Coast Guard Headquarter, Washington, D.C. 1973.
Michaelson Robert W.
Sikora Jerome P.
Assouad Patrick
Duong Khoi Hung
Shuster Jacob
The United States of America as represented by the Secretary of
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