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Proceedings Papers

Paper presented at the The Thirteenth ISOPE Pacific/Asia Offshore Mechanics Symposium, October 14–17, 2018

Paper Number: ISOPE-P-18-011

... : mass of flotsam, : operating time This is an approximate formula when the momentum before the collision is thought to have acted as a force product. Although this is a relatively simple

**expression**, it has the advantage that it is easy to adapt to any kind of drifting object. In this paper, at first, we...
Abstract

ABSTRACT This thesis investigates the collision force of driftwoods and small boats due to tsunamis. Even though there are some calculation formulas from past experiments, quantitative approaches for design criteria of tsunami protection structures are not established. Accordingly, to upgrade design criteria of tsunami protection structures, the thesis aimed to investigate into an adaptability of the formulas obtained past researches and new experimental evaluation formula derived from present research comparing with the measurements of hydraulic model experiment. INTRODUCTION On March 11, 2011, Tohoku - Pacific Coast Earthquake tsunami struck a large area on the Pacific coast, especially from Chiba Prefecture to the coastal areas of Aomori Prefecture, where the damage to coastal structures was so great, not only port facilities, but also shore protection facilities such as breakwater, seawall, and sea embankment. In particular, the area around the Fukushima Daiichi nuclear power plant suffered from the damage generated by radiation leak due to tsunamis. On the other hand, it was confirmed that the Kamaishi bay-mouth breakwater delayed reaching tsunami in the bay and had the effect of reducing the tsunami height. In the shore protective facilities such as breakwater, it is considered to have protective effect on the tsunami(Hiraishi et al., 2011). Accordingly, it is necessary to make the shore protective facilities tenacious structure that can withstand the port structure without collapsing even for the largest scale tsunami. In this way, this report investigates the collision force of driftwoods and small boats due to tsunamis. Even though there are some calculation formulas from previous researches, quantitative approaches for design criteria of tsunami protection structures are not established. Accordingly, to upgrade design criteria of tsunami protection structures, the research aimed to investigate into an adaptability of the formulas from previous researches and new experimental evaluation formula derived from present research. In this paper, to compare the measurements with the calculation formula, we have a hydraulic model experiment. With regard to small boat, we use the measurements of experiment conducted in 2017 and of similar experiments conducted in 2016(Okura, 2017) and 2015(Ono and Hiraishi, 2017) as well in this experiment. In contrast, with regard to driftwood, we use the measurements of similar experiments conducted in 2016 and 2015.

Proceedings Papers

Paper presented at the The Sixth ISOPE Pacific/Asia Offshore Mechanics Symposium, September 12–16, 2004

Paper Number: ISOPE-P-04-019

... interpretation ice thickness growth distribution density forecast error density

**expression**characteristic modeling & simulation forecast dmitriev forecast value thickness growth formula About a Possibility for a Probabilistic Interpretation for Forecast Dates when Ice Thickness Growth up to 20...
Abstract

ABSTRACT: The article is concerned with results of probabilistic interpretation for forecast dates when ice thickness growth up to 20-25 cm in the Kara, Laptev, East-Siberian and Chukchi Seas. The method of the probabilistic interpretation is based on the condition forecast errors distribution's approach formulated by the author (Dmitriev, 1997). Its goal is to find a way to estimate categorical (binary) forecast uncertainty for further translating into uncertainty in the quantity of interest to the user ac-cording to "end-to-end" forecasting concept. The results of calculating forecast errors distribution density parameters are given for combining data from the areas mentioned above. It provides a principal possibility to use binary forecasts in continuous optimization during planning sea ice-depended actions. INTRODUCTION At present new techniques are developed for economic situations (which have weather dependent component) where the outcome is a continuous variable and where the decision is also a continuous variable ( Langland et al., 2001; Smith et al., 2001). In accordance with "end-to-end" forecasting concept ( Langland et al., 2001; Smith et al. , 2001) it is necessary to translate uncertainty in the weather into uncertainty in the quantity of interest to the user that is clear for probabilistic forecasts but is a matter of some difficulty with categorical (binary) forecasts in case of continuous (or conditionally continuous) variable. The problem is well known and there are two basic ways to get a solution. A "classic" approach is based on Model Output Statistics (MOS) and it consists of "matrixes of contingency" calculation in accordance to traditional forecast procedures ( Brooks et al., 1996; Murphy, 1985 ; Vorob'ev et al., 2002). A modern approach is based on an ensemble forecasting technique (see, for example, ( Gustafsson., 2002) and its references) with a statistics modelling as a main idea.

Proceedings Papers

Paper presented at the The First ISOPE Pacific/Asia Offshore Mechanics Symposium, June 24–28, 1990

Paper Number: ISOPE-P-90-098

... wave energy transmission and the theory of vibration, a semi-empirical formula is proposed for simplifying the evaluation of the impact energy and force of ship in regular waves upon the detached piers. coefficient

**expression**ship motion pier strain energy impact energy cable force wave...
Abstract

ABSTRACT: In this paper, the results of model tests of impact energy and forces of moored ships from 20,000 dwt to 200,000 dwt in regular waves upon piers ace synthetically analyzed. Based on the concept of Wave energy transmission and the theory of vibration, a semi empirical formula for evaluating impact energy and forces are proposed. INTRODUCTION In the design of detached piers or platforms in unprotected water areas, the impact loading of ship in waves upon the piers is one of the important problems that are mostly concerned by engineers. Recently, a model test investigating the impact and mooring loading of a 200,000 dwt ship upon a detached pier has been performed by the authors. The dimensions, of the prototype ship are: 315 m in length " 52 m in width and 26 m in depth. Three loading, conditions were taken in the tests, i.e., fully loaded with displacement tonnage of 255,600 t" half loaded with displacement tonnage of 166,000 t and ballasted with displacement tonnage of 106,000t, with drafts of 18.2, m. 13.1 m and 9.1 m for, each " case respectively. The natural frequency of rolling, of the prototype ship is 16,6 s. Together with the previous model studies on the i:m;p.act and mooring loadings of 20,000 dwt, 50,000 dwt ships upon piers by the authors (Gao, 1975 Huang et aI, 1988) and the tests of 20,000 dwt (Li,1982) and 50,000 dwt and 100,000 dwt; (Li, 1985) by other researchers in China, a synthetic analysis is worked out in this paper. Based on the concept of wave energy transmission and the theory of vibration, a semi-empirical formula is proposed for simplifying the evaluation of the impact energy and force of ship in regular waves upon the detached piers.

Proceedings Papers

Paper presented at the The First ISOPE Pacific/Asia Offshore Mechanics Symposium, June 24–28, 1990

Paper Number: ISOPE-P-90-160

... the function of the coordinate (x). and the latitude component of displacement (v) is zero. limit value deformation coefficient

**expression**stability theory boundary classical stability theory curvature deflection function eqn equation equilibrium equation hydrostatic pressure...
Abstract

ABSTRACT: The coefficient of buckling pressure of spherical-cap and spherical shell has been found out on the oblate shell theory. This roefficient demonstrates that the buckling pressure take either the upper limit value or the lower limit value according to the state of deformation of spherical-cap and spherical shell just before the moment of buckling. The results of the experiments usually accord with the lower limit. INTRODUCTION There is great difference between the testing results and classical stability theory value of spherical shell subjected to hydrostatic pressure. It is a difficult problem to find a theoretical formula in stability theory in good agreement with test data. The solution of this problem is of significant both in theory and application. We believe that the buckling area of spherical shell may be treated as a spherical-cap with a circle boundary. Under the uniform pressure, bending deformation symmetrial about the apex of the spherical-cap take place. From this characteristic displacement function (w) can be obtained from eqs (I) and (2). When buckling occurs, the uniform pressure P becomes the buckling pressure (Pcr), we may get the coefficient of buckling pressure from the displacement function (Ii), this coefficient shows that the buckling pressure of a spherical-rap and a spherical shell has upper limit and lower limit values. The upper limit value is the same value calculated by classical stability theory. FUNCTION OF DISPLACEMENT AND COEFFICIENT OF STRESS The curve coordinate system of spherical-cap with circle boundary is assumed with the Line x of the meridian direction and line y of the latitude direction as shown in Fig. 1. From the symmetry of displacement the components (u) and (w) of displacement of a given point with coordinate (x) are of the function of the coordinate (x). and the latitude component of displacement (v) is zero.

Proceedings Papers

Paper presented at the The First ISOPE Pacific/Asia Offshore Mechanics Symposium, June 24–28, 1990

Paper Number: ISOPE-P-90-066

... traditionally based on the Monson equation, in which the wave force at any section of a member is

**expressed**directly in terms of the fluid kinematics which would occur at that section" s location (e.g. Sarpkaya and Isaacson, 1981). The application of the Monson equation to regular waves is straightforward in...
Abstract

ABSTRACT: The present paper describes a selection of recent research relating to random wave forces acting on slender structural members. A brief review of prediction methods for random wave forces is initially given, and recent research into three specific aspects of random wave forces is then described. These relate to (i) the effects of multi-directional waves; (ii) the intermittent forces acting on sections near the water surface; and (hi) wave slamming forces on horizontal cylinders. For the first two cases, corresponding to multi-directional wave loading and to intermittent loading, comparisons are presented between available experimental data, numerically simulated data and theoretical predictions. INTRODUCTION The prediction of wave loads on offshore structures is an important component of offshore design. For structures comprised of slender members, wave force predictions are traditionally based on the Monson equation, in which the wave force at any section of a member is expressed directly in terms of the fluid kinematics which would occur at that section" s location (e.g. Sarpkaya and Isaacson, 1981). The application of the Monson equation to regular waves is straightforward in principle and requires that the kinematics be obtained by an appropriate wave theory. For the case of random waves, the Monson equation may be applied to develop the statistical properties of the forces. These relate to the effects of multi-directional waves; the Intermittent forces acting on sections near the water surface; and wave slamming forces on horizontal cylinders near the free surface. In the case of multi-directional waves, the estimation of forces on a structure is complicated because of the continuously changing direction of the incident flow kinematics associated with the multidirectional waves. The spectral and probabilistic properties of the force taking this into account have been described by Isaacson and Nwogu (1989).

Proceedings Papers

Paper presented at the The First ISOPE Pacific/Asia Offshore Mechanics Symposium, June 24–28, 1990

Paper Number: ISOPE-P-90-077

... ABSTRACT: An efficient and accurate numerical procedure is described for computing the second-order diffraction forces on arbitrary floating bodies in regular waves. Green" s second identity is exploited to

**express**the second-order forces due to the second-order potential in terms of the first...
Abstract

ABSTRACT: An efficient and accurate numerical procedure is described for computing the second-order diffraction forces on arbitrary floating bodies in regular waves. Green" s second identity is exploited to express the second-order forces due to the second-order potential in terms of the first-order quantities alone. The resulting expressions for the second-order forces are evaluated from numerical first-order solutions based on the hybrid integral-equation method. The validity of the numerical procedure is confirmed by comparison of the computed results with the analytical solution for the second-order force on an articulated vertical cylinder. Results from the model tests on a circular dock are also presented to validate the theoretical predictions. INTRODUCTION The wave loads acting on floating structures in irregular seas include the second-order, high- and low-frequency force components at sum- and difference frequencies of the wave group, which arise from nonlinearities due to effects of finite wave elevation and finite body motions. These second-order forces may not be large in magnitude compared with first-order excitation at wave frequencies, but can never be ignored due to the possibilities of exciting resonance frequencies of lightly damped systems. Difference-frequency forces can excite large horizontal excursions of moored structures and large vertical-plane motions of floating structures of small water plane area. Sum-frequency forces can excite resonance oscillations in vertical modes of tension-leg plat-" forms. The prediction of the second-order forces on floating bodies is usually made on the basis of potential flow assumption. The forces can be obtained by integrating the hydrodynamic pressure over the submerged body surface and by retaining terms to second order in wave slope in a consistent perturbation expansion (Ogilvie, 1983). The resulting expressions for the second-order forces involve the contribution from the second-order velocity potential. To obtain this contribution, one may use two alternative approaches.

Proceedings Papers

Paper presented at the The First ISOPE Pacific/Asia Offshore Mechanics Symposium, June 24–28, 1990

Paper Number: ISOPE-P-90-057

... problem diffraction vertical cylinder right-hand side term disturbance cylinder wave solution boundary condition surface wave diffraction specific solution wave diffraction problem wave diffraction

**expression**diffraction problem order diffraction problem asymptotic solution Proceedmgs o...
Abstract

ABSTRACT: Based on the proper description of the condition at infinity for nonlinear surface wave diffraction In physical sense, the high order asymptotic solution as well as the Inhomogeneous boundary condition at infinity for second order surface wave diffraction are obtained. It contributes a complete and rational mathematical model towards the problem, and clarifies the controversy rising among a lot of works about it. I. INTRODUCTION Stokes perturbation expansion has been recognized as an effective method valid for the solution of mild nonlinear sun-ace wave diffraction. The first order wave diffraction theory, i.e., the linear diffraction theory, based on the expansion, is complete and rational in Its mathematical formulation. However, for the diffraction problems of second order and higher orders, the free surface boundary condition is inhomogeneous. The right-hand side inhomogeneous term is recognized as pressure disturbance distributed infinitely on the free surface. Consequently, the question is how to properly define the boundary condition at infinity for the surface wave diffraction problems of second order and higher orders to be consistent with this kind of pressure disturbance. In the context of second order problem, a lot of papers have been published previously [1-5, 7-13]. However, even for the wave diffraction against a vertical cylinder, many solutions of second order problem obtained by different authors exhibit obvious differences, which are partly affected by distinct forms of boundary condition at infinity presented In those papers. II. PHYSICAL CONDITION AT INFINITY FOR SECOND ORDER DIFFRACTION PROBLEM Essentially, the surface wave diffraction phenomenon is the wave motion generated by some active disturbance at infinity and existing in the flow field where some structures of large scale is located. For the nonlinear surface wave diffraction problem, we can't define the physical condition at infinity of assuming an active disturbance source at Infinity.