• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.06a
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• pp.253-254
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• 2014

In offshore, various external forces such as wind force, wave force and impulsive breaking wave force act on offshore structures. Many researches about this forces are published. Kim and Cao(2008) published researche on wave force of vertical cylinder. Kim and Go(2013) performed research on the subgrade reaction by external forces. Among this forces, impulsive breaking force is more massive than other forces, especially. Therefore, the studies about impulsive breaking wave forces have been carried out. Chun and Shim(1999) analyzed dynamic behavior of cylindrical pile subjected to impulsive breaking wave force. In this study, when the impulsive breaking wave force acts on the offshore wind turbine, the subgrade reaction acting on the mono-pile of the offshore wind turbine is calculated by p-y curve. The calculation is carried out to the multi-layered.

• Journal of Navigation and Port Research
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• v.39 no.5
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• pp.385-391
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• 2015

In offshore, various external forces such as wind force, tidal current and impulsive breaking wave force act on offshore wind tower. Among these forces, impulsive breaking wave force is especially more powerful than other forces. Therefore, various studies on impulsive breaking wave forces have been carried out, but the soil reaction are incomplete. In this study, the p-y curve is used to calculate the soil reaction acting on the offshore wind tower when an impulsive breaking wave force occurs by typhoon. The calculation of offshore wind tower against impulsive breaking wave force is applied for the multi-layered soil. The results obtained in this study show that although the same wave height is applied, the soil reaction generated by impulsive breaking wave force is greater than the soil reaction generated by wave force.

• Journal of Ocean Engineering and Technology
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• v.16 no.6
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• pp.7-17
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• 2002

Recently, artificial rocks, instead of buoys, have been placed on the submerged breakwater to indicate its location. The accurate estimation of wave forces on these rocks is deemed necessary for their stability design. Characteristics of the wave force, however, are expected . to be very complicated because of the occurrence of breaking or post-breaking waves. In this regard, wave forces exerted on an artificial rock have been investigated in this paper. The maximum wave force has been found to strongly dependent on the location and shape of the artificial rock that is placed on the submerged breakwater. The plunging breaker occurs near the loading cram edge of a submerged breakwater, which cause impulsive breaking wave force on the rock. Using the Morison equation, with the velocity and acceleration at the front face of the artificial rock and varying water surface level, it is possible to estimate wave forces, even impulsive breaking wave forces, that are acting on the rock installed on a submerged breakwater. The vertical wave force is also found to depend, significantly, on the buoyant force.

• Journal of Ocean Engineering and Technology
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• v.10 no.1
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• pp.75-80
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• 1996

The importance of the impact force on the vertical offshore circular structure member in the surf zone due to the breaking wave has been recognized recently. In this paper characteristics of breaking wave forces and the corresponding estimation procedures for them are investigated. For the characterization of the wave forces, three parts, drag force, inertia force, impact force are categorized and identified, respectively. Among them the impact force is maimly studied and the concise form of the force is proposed with the application scheme for the design of offshore circular structure member. The resulting form porposed here for impact force is well coincided with former research results by other people. Except the impact force, so called Morison equation can be employed for the common offshore structure design. The drag force and inertia force are represented as convertionally for the profile except the breaking part. In the numerical example, for thpical sea condition and the member size, the proposed procedures for the breaking wave forces calculation are demonstrated. It is found that the impact force is the most deminant one comparing with inertia and drag forces in the surf zone.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.220-226
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• 2001

It is important to estimate exactly wave forces acting on various types of offshore structures under the severe environmental conditions in the ocean site. This paper presents an easy experimental method which deals with transient waves. The proposed scheme made it possible to generate breaking waves at any position in the wave tank by changing the maximum slope of the component waves. The theoretical and experimental methods were investigated by generating concentrated waves which acted on a single and multiple cylinders. The waves forces increased rapidly when the models encountered breaking waves. The theoretical results underestimates the forces due to breaking waves. Therefore, the effects due to breaking waves should be considered carefully in the design process of a structure under the influence of breaking waves.

• Journal of Ocean Engineering and Technology
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• v.15 no.4
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• pp.8-13
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• 2001

It is important to estimate exactly wave forces acting on various types of offshore structures under the severe environmental conditions in the ocean site. This paper presents an easy experimental method which deals with transient waves. The proposed scheme made it possible to generate breaking waves at any position in the wave tank by changing the maximum slope of the component waves. The theoretical and experimental methods were investigated by generating concentrated waves which acted on a single and multiple cylinders. The waves forces increased rapidly when the models encountered breaking waves. The theoretical results underestimates the forces due to breaking waves. Therefore, the effects due to breaking waves should be considered carefully in the design process of a structure under the influence of breaking waves.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.2
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• pp.100-108
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• 1998

Morison formula has been used in the determination of wave forces acting on vertical cylindrical piles of ocean structures. The formula, however, can be applied to mildly varying varying incident waves with symmetrical shapes. The breaking waves impinge on structures with very high impact forces, which completely differ from the inertia and drag forces of the Morison formula in both magnitudes and characteristics. In the present study, a boundary element method is applied to determine the water particle velocity and acceleration under the breaking waves. A numerical model is then developed to determine breaking wave forces utilizing those water particle kinematics. The results of the model is then developed to determine breaking wave forces utilizing those water particle kinematics. The results of the model agree well with existing experimental data, giving maximal wave forces 3 times and maximal moments 5 times larger than the Morison formula does.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.4
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• pp.439-445
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• 2017

Plunging breaker slamming pressures on vertical or sloping sea dikes are one of the most severe and dangerous loads that sea dike structures can suffer. Many studies have investigated the impact forces caused by breaking waves for maritime structures including sea dikes and most predictions of the breaker forces are based on empirical or semi-empirical formulae calibrated from laboratory experiments. However, the wave breaking mechanism is complex and more research efforts are still needed to improve the accuracy in predicting breaker forces. This study proposes a semi-empirical formula, which is based on impulse-momentum relation, to calculate the slamming pressure due to plunging wave breaking on a sloping sea dike. Compared with some measured slamming pressure data in two literature, the calculation results by the new formula show reasonable agreements. Also, by analysing probability distribution function of wave heights, the proposed formula can be converted into a probabilistic expression form for convenience only.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.3
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• pp.141-148
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• 1999

The magnitude of breaking wave forces given by plunging breakers incident on a pile structure is much greater than the forces calculated by Morison's formula, but those forces may act on pile for very short duration in the range of a few multiples of 0.01 second. Hence, a dynamic analysis for the impact forces of breaking waves may be necessary for the accurate determination of pile displacements in the first stage of design. The time series of the impact force along the pile length is thus required, which may be estimated from the pressure distribution. In the present study, breaking wave pressures are measured for a vertical pile at real field which is easily subjected to plunging breakers in stormy weather conditions. The measured data are analyzed and compared with other results to quantify the characteristics of breaking wave pressures in real fields.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.2
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• pp.136-145
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• 2007

When waves propagating over an underwater shoal break at the top of the shoal, wave heights are drastically decreased in the downstream breaking zone, but a secondary current shooting downstream with strong velocity can be induced by the breaking waves themselves. In the case that an offshore structure is placed in the breaking zone, the estimation of wave farce purely based on the visible wave height may cause an under-design of the structure. Thus, for the safe design of the structure, the breaking wave induced current should be necessarily considered in the comprehensive estimation of design load. In the present study, Boussinesq equation model to calculate the wave height distribution and breaking wave induced current was set up and applied to the scheme of a hydraulic model test previously undertaken. Based on the results of the Boussinesq model, fluid forces acting on the model structure were calculated and compared with the experimental results. The importance of the breaking wave induced current was quantitatively assessed by comparing fluid forces with or without current.