• Computational Structural Engineering
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• v.6 no.4
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• pp.73-82
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• 1993

Investigated in this paper is the effect of fluid-structure interaction between reactor internal components due to their immersion in a confining fluid on the dynamic responses. A non-linear mathematical model is developed for the dynamic analysis of the reactor internals, which includes lumped masses, stiffnesses and hydrodynamic couplings. The hydrodynamic mass matrix which characterizes the fluid-structure interaction is calculated. Also, the equations of motion containing hydrodynamic mass matrix are presented. The responses of the reactor internals due to seismic and pipe break excitations are obtained for the case of with- and without-hydrodynamic couplings and the different response characteristics are investigated.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.413-422
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• 2001

In this study, the effect of hydrodynamic masses is investigated in the dynamic characteristics and earthquake response analyses of the submerged HANARO flow tubes. First, the consistent hydrodynamic masses of the surrounding water are obtained by finite element method. Then, modal analyses and response spectrum analyses are performed and verified by comparing the results with those measured from an experiment. Arbitrary cross-sections of submerged structures and boundary conditions of the surrounding fluid can be considered by using the general benefits of a finite element method comparing with the conventional analytical methods. Practical criteria based on parametric studies are proposed to evaluate the dynamic characteristics of HANARO flow tubes including the hydrodynamic masses.

• Journal of Ocean Engineering and Technology
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• v.21 no.4
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• pp.38-44
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• 2007

The structural response characteristics of Tension leg platforms(TLPs) in waves are examined for presenting the basic data for structural design of TLPs. The numerical approach is based on a combination of the three dimensional source distribution method and the structural response analysis method, in which the superstructure of TLP is assumed to be flexible instead of rigid. Hydrodynamic and hydrostatic forces on the submerged surface of a TLP have been accurately calculated by excluding the assumption of the slender body theory. The hydrodynamic interactions among TLP members, such as columns and pontoons, and the structural damping are included in structural analysis. The mooring forces are estimated as the sum of pretension of tendons and variational tension due to longitudinal displacements. Stiffness matrices of elastic beam elements connecting nodes are formulated by ordinary method of three dimensional frame analysis. The equation of motion about the whole structure is obtained by the sum of forces and moments acting on each nodes.

• International journal of steel structures
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• v.18 no.4
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• pp.1191-1199
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• 2018

Concepts of submerged floating tunnels (SFTs) for land connection have been continuously suggested and developed by several researchers and institutes. To maintain their predefined positions under various dynamic environmental loading conditions, the submerged floating tunnels should be effectively moored by reasonable mooring systems. With rational mooring systems, the design of SFTs should be confirmed to satisfy the structural safety, fatigue, and operability design criteria related to tunnel motion, internal forces, structural stresses, and the fatigue life of the main structural members. This paper presents a feasibility study of a submerged floating tunnel moored by an inclined tendon system. The basic structural concept was developed based on the concept of conventional cable-stayed bridges to minimize the seabed excavation, penetration, and anchoring work by applying tower-inclined tendon systems instead of conventional tendons with individual seabed anchors. To evaluate the structural performance of the new type of SFT, a hydrodynamic analysis was performed in the time domain using the commercial nonlinear finite element code ABAQUS-AQUA. For the main dynamic environmental loading condition, an irregular wave load was examined. A JONSWAP wave spectrum was used to generate a time-series wave-induced hydrodynamic load considering the specific significant wave height and peak period for predetermined wave conditions. By performing a time-domain hydrodynamic analysis on the submerged floating structure under irregular waves, the motional characteristics, structural stresses, and fatigue damage of the floating tunnel and mooring members were analyzed to evaluate the structural safety and fatigue performance. According to the analytical study, the suggested conceptual model for SFTs shows very good hydrodynamic structural performance. It can be concluded that the concept can be considered as a reasonable structural type of SFT.

• Journal of Power System Engineering
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• v.2 no.2
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• pp.81-86
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• 1998

The dynamic response characteristics of Tension Leg Platforms(TLPs) in waves are examined for presenting the basic data for design of TLPs. The numerical approach is based on a combination of the three dimensional source distribution method and the dynamic response analysis method, in which the superstructure of TLP is assumed to be flexible instead of rigid. Restoring forces by hydrostatic pressure on the submerged surface of a TLP have been accurately calculated by excluding the assumption of the slender body theory. The hydrodynamic interactions among TLP members, such as columns and pontoons, and the structural damping are included in the motion and structural analysis. Numerical results are compared with the experimental ones, which are obtained in the literature, concerning the motion and tension responses of a TLP in waves. The results of comparison confirmed the validity of the proposed approach.

• Journal of Wind Energy
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• v.14 no.4
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• pp.29-42
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• 2023

In this study, research and empirical cases of floating offshore wind turbine systems with a tension-leg platform are investigated, and hydrodynamic and structural characteristics according to platform shapes and characteristics during transportation and installation are confirmed. Most platforms are composed of pontoons or corner columns, and these are mainly located below the waterline to minimize the impact of breaking waves and supplement the lack of buoyancy of the center column. These pontoons and corner columns are designed with a simple shape to reduce manufacturing and assembly costs, and some platforms additionally have reinforcements such as braces to improve structural strength. Most of the systems are assembled in the yard and then moved by tugboat and installed, and some platforms have been developed with a dedicated barge for simultaneous assembly, transportation and installation. In this study, we intend to secure the basic data necessary for the design, transportation, and installation procedures of floating offshore wind turbine systems with a tension-leg platform.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.1
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• pp.41-49
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• 2015

Analysis and test of hydrodynamic ram in welded metallic tanks containing water were performed to investigate the phenomena and to understand the effects on the resulting structural behavior. Arbitrary Lagrange-Euler coupling method was used for the analysis of the fluid-structure interaction occurring in the hydrodynamic ram, where the projectile, tank, and water are exchanging load, momentum, and energy during the traveling of the projectile through the water of the tank. For a better representation of the physical phenomena, modeling of the welded edges is added to the analysis to simulate the earlier weld line fracture and its influence on the resulting hydrodynamic ram behavior. Corresponding hydrodynamic tests were performed in a modified gas gun facility, and the following panel-based examinations of various parameters, such as displacement, velocity, stress, and energy, as well as hydrodynamic ram pressure show that the analysis and test are well correlated, and thus the results of the study reasonably explain the characteristics of the hydrodynamic ram. The methodology and procedures of the present study are applicable to the hydrodynamic ram assessment of airframe survivability design concepts.

• Ocean Systems Engineering
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• v.3 no.2
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• pp.149-165
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• 2013

Tension leg platforms (TLP's) are highly nonlinear due to large structural displacements and fluid motion-structure interaction. Therefore, the nonlinear dynamic response of TLP's under hydrodynamic wave loading is necessary to determine their deformations and dynamic characteristics. In this paper, a numerical study using modified Morison Equation was carried out in the time domain to investigate the influence of nonlinearities due to hydrodynamic forces and the coupling effect between all degrees of freedom on the dynamic behavior of a TLP. The stiffness of the TLP was derived from a combination of hydrostatic restoring forces and restoring forces due to cables and the nonlinear equations of motion were solved utilizing Newmark's beta integration scheme. The effect of wave characteristics was considered.

• Computers and Concrete
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• v.16 no.3
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• pp.429-448
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• 2015

The dams are huge structures storing a large amount of water and failures of them cause especially irreparable loss of lives during the earthquakes. They are named as a group of structures subjected to fluid-structure interaction. So, the response of the fluid and its hydrodynamic pressures on the dam should be reflected more accurately in the structural analyses to determine the real behavior as soon as possible. Different mathematical and analytical modelling approaches can be used to calculate the water hydrodynamic pressure effect on the dam body. In this paper, it is aimed to determine the dynamic response of concrete gravity dams using different water modelling approaches such as Westergaard, Lagrange and Euler. For this purpose, Sariyar concrete gravity dam located on the Sakarya River, which is 120km to the northeast of Ankara, is selected as a case study. Firstly, the main principals and basic formulation of all approaches are given. After, the finite element models of the dam are constituted considering dam-reservoir-foundation interaction using ANSYS software. To determine the structural response of the dam, the linear transient analyses are performed using 1992 Erzincan earthquake ground motion record. In the analyses, element matrices are computed using the Gauss numerical integration technique. The Newmark method is used in the solution of the equation of motions. Rayleigh damping is considered. At the end of the analyses, dynamic characteristics, maximum displacements, maximum-minimum principal stresses and maximum-minimum principal strains are attained and compared with each other for Westergaard, Lagrange and Euler approaches.

• Journal of computational fluids engineering
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• v.13 no.1
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• pp.14-20
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• 2008

The flow characteristics around a rudder in open water condition is analyzed by the computational method. Reynolds averaged Navier-Stoke's equation is utilized for the computation. The computational hydrodynamic force coefficients are verified through comparing with the experimental results. The information of these flow characteristics is necessary to predict cavitation and maneuvering performances, to estimate steering gear capacitance, and to get the bending moment which is useful for the structural analysis. The pressure distribution, the three-dimensional flow separation, and the tip vortices are investigated. The pattern of the three-dimensional flow separation is analyzed utilizing a topological rule. The tip vortices are also investigated through a visualization technique.