• 한국산업융합학회 논문집
• /
• 제4권4호
• /
• pp.433-439
• /
• 2001

A large floating structure is attracting great attention in recent years from the view of ocean space utilization. Its huge scale in the horizontal directions compared with the wavelength and relatively shallow depth make this type of floating structure flexible and its wave-induced motion be characterized by the elastic deformation. In this paper, a boundary integral equation method is proposed to predict the wave-induced dynamic response mat-like floating offshore structure. The structure is modeled as an clastic plate and its elastic deformation is expressed as a superposition of free-vibration modes in air. This makes it straightforward to expand the well-established boundary integral technique for rigid floating bodies to include the hydroelastic effects. In order to validate the theoretical analysis, we compare with the experimental result of previous model test. Satisfactory agreement is found between theory and experiment.

• Ocean Systems Engineering
• /
• 제9권4호
• /
• pp.423-448
• /
• 2019

Very Large Floating Structures (VLFS) are one among the solution to pursue an environmentally friendly and sustainable technology in birthing land from the sea. VLFS are extra-large in size and mostly extra-long in span. VLFS may be classified into two broad categories, namely the pontoon type and semi-submersible type. The pontoon-type VLFS is a flat box structure floating on the sea surface and suitable in regions with lower sea state. The semi-submersible VLFS has a deck raised above the sea level and supported by columns which are connected to submerged pontoons and are subjected to less wave forces. These structures are very flexible compared to other kinds of offshore structures, and its elastic deformations are more important than their rigid body motions. This paper presents hydroelastic analysis carried out on an innovative VLFS called truss pontoon Mobile Offshore Base (MOB) platform concept proposed by Srinivasan and Sundaravadivelu (2013). The truss pontoon MOB is modelled and hydroelastic analysis is carried out using HYDRAN-XR^* for regular 0° waves heading angle. Results are presented for variation of added mass and damping coefficients, diffraction and wave excitation forces, RAOs for translational, rotation and deformational modes and vertical displacement at salient sections with respect to wave periods.

• Journal of Theoretical and Applied Mechanics
• /
• 제2권1호
• /
• pp.1-14
• /
• 1996

In this paper, breaking waves are generated in a 2-D wave tank and simulated by using a higher-order boundary element method. A piston-type wavemaker is operated by signals composed of elementary waves. The phase of elementary waves is determined by the linear theory such that they are focused to a prescribed position. Calculated plunging waves coincide well with experiment. A steel box with different plate thicknesses is installed at a predetermined position in the tank. Measured impulsive pressures due to breaking waves are found to be 0.8-1.2$\rho$C2, where $\rho$ corresponds to water density and C to wave celerity. The transverse displacement of the plate is described in terms of modal eigenfunctions. The natural frequencies measured by impact tests in air for thin plate coincide with the computational and theoretical values. The radiationpotential due to plate vibration is derived and the radiation force is expressed in terms of hydroelastic added mass and damping forces. Comparison of natural frequencies of plate in water proves that hydroelastic added mass and damping are properly considered. The measured strain due to regular waves supports the calculated one, but there are apparent discrepancies between theory and experiment in the impulsive case.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제5권1호
• /
• pp.1-20
• /
• 2013

In the present paper, the sloshing resistance performance of a huge-size LNG carrier's insulation system is evaluated by the fluid-structure interaction (FSI) analysis. To do this, the global-local analysis which is based on the arbitrary Lagrangian-Eulerian (ALE) method is adopted to accurately calculate the structural behavior induced by internal LNG sloshing of a KC-1 type LNG carrier insulation system. During the global analysis, the sloshing flow and hydrodynamic pressure of internal LNG are analyzed by postulating the flexible insulation system as a rigid body. In addition, during the local analysis, the local hydroelastic response of the LNG carrier insulation system is computed by solving the local hydroelastic model where the entire and flexible insulation system is adopted and the numerical analysis results of the global analysis such as initial and boundary conditions are implemented into the local finite element model. The proposed novel analysis techniques can potentially be used to evaluate the structural integrity of LNG carrier insulation systems.

• Steel and Composite Structures
• /
• 제42권2호
• /
• pp.243-256
• /
• 2022

A coupled finite element method (FEM)-boundary element method (BEM) for analyzing the hydroelastic response of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) floating plates under moving loads is firstly introduced in this article. For that aim, the plate displacement field is described utilizing a generalized shear deformation theory (GSDT)-based FEM, meanwhile the linear water-wave theory (LWWT)-relied BEM is employed for the fluid hydrodynamic modeling. Both computational domains of the plate and fluid are coincidentally discretized into 4-node Hermite elements. Accordingly, the C1-continuous plate element model can be simply captured owing to the inherent feature of third-order Hermite polynomials. In addition, this model is also completely free from shear correction factors, although the shear deformation effects are still taken into account. While the fluid BEM can easily handle the free surface with a lower computational effort due to its boundary integral performance. Material properties through the plate thickness follow four specific CNT distributions. Outcomes gained by the present FEM-BEM are compared with those of previously released papers including analytical solutions and experimental data to validate its reliability. In addition, the influences of CNT volume fraction, different CNT configurations, water depth, and load speed on the hydroelastic behavior of FG-CNTRC plates are also examined.

• 대한토목학회논문집
• /
• 제30권3B호
• /
• pp.315-324
• /
• 2010

본 논문에서는 대규모 유탄성 해석을 통해 초대형 부유식 해상구조물의 설계 차트를 개발했다. 초기 설계단계에 본 챠트를 이용해서 고비용의 유탄성 해석을 사용하지 않고도 초대형 부유식 해상구조물의 유탄성 거동을 예측이 가능하다. 본 논문에서는 두 가지 종류의 설계챠트 I, II을 개발하여 제시하였다. 설계차트 I은 특정 주파수의 파랑에 대한 구조물의 최대응력 응답진폭함수를 얻을 수 있도록 개발되었다. 설계차트 I의 경우 동일한 변장비와 무차원 구조강성계수를 갖는 모든 구조물에 적용이 가능하다. 설계챠트 I과 파랑스펙트럼의 적분을 통해 설계차트 II를 개발하였으며, Beaufort 풍력급에 따른 Bretschneider 스펙트럼을 적용해 해상의 환경요인을 고려하도록 구성되었다.

• 대한조선학회논문집
• /
• 제39권2호
• /
• pp.11-18
• /
• 2002

본 논문은 착저식 방파제를 고려하여 방파제 후면에 위치한 부유식 해상공항의 파도 중에서 유탄성 응답을 계산하는 방법을 제시하였다. 방파제 효과를 고려한 일반화된 방사문제를 해석하기 위하여 소오스-다이폴 분포법을 사용하였고, 산란문제를 해석하기 위하여 속도포텐셜접속법과 소오스-다이폴 분포법을 이용하였다. 구조물의 응답은 자유-자유 보의 고유 모드함수에 의한 모드 해석법을 사용하여 계산하였다. 계산 모델로 길이가 1000m의 해상공항 구조물을 도입하였고, 방파제의 효과를 살펴보기 위해 방파제와 해상공항사이의 거리 및 입사화랑의 각도를 변화시키면서 수직 응답 및 굽힘 모우멘트 등을 계산하였다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 추계학술대회논문집
• /
• pp.809-814
• /
• 2006

In this paper, the modified direct method employing beam transformation technique is proposed in order to efficiently calculate hydroelastic responses of floating structure. Since the proposed method expresses the displacements of three-dimensional structure with those of transformed beam which leads to small number of equations of motion, the method is numerically efficient compared to the conventional direct method. To verify the efficiency of the proposed method a 500 m-long floating structure under wave loads is considered in numerical example. Displacements, bending moments, torsion moments and shear forces are calculated and computing tine is examined. The results are also compared with those of the conventional direct method.

• 한국해양공학회지
• /
• 제19권4호
• /
• pp.1-8
• /
• 2005

A nonlinear time-domain strip theory for vertical wave loads and ship responses is to be investigated. The hydrodynamic memory effect is approximated by a higher order differential equation without convolution. The ship is modeled as a non-uniform Timoshenko beam. Numerical calculations are presented for the S175 Containership translating with the forward speed in regular waves. The approach described in this paper can be used in evaluating ship motions and wave loads in extreme wave conditions and validating nonlinear phenomena in ship design.

• 한국소음진동공학회논문집
• /
• 제17권1호
• /
• pp.17-23
• /
• 2007

In this paper, the modified direct method employing beam transformation technique is proposed in order to efficiently calculate hydroelastic responses of floating structure. Since the proposed method expresses the displacements of three-dimensional structure with those of transformed beam which leads to small number of equations of motion, the method is numerically efficient compared to the conventional direct method. To verify the efficiency of the proposed method, a 500 m-long floating structure under wave loads is considered in numerical example. Displacements, bending moments, torsion moments and shear forces are calculated and computing time is examined. The results are also compared with those of the conventional direct method.