• Journal of the Korean Society for Railway
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• v.16 no.4
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• pp.278-285
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• 2013

The suppression of residual settlement is required on earthwork sections as concrete track is introduced. Use of pile-slab structure is one of the settlement restraining methods applied on soft ground. The slab distributes the upper embankment load and piles transfer the load from the slab to the stiff ground. While this method is very effective in terms of load transfer, it has not yet been established for dealing with the vibration transfer effects and interaction characteristics between a structure and the ground. It is possible that vibration caused by a moving train load is propagated in the upper embankment, because the slab acts as a reflection layer and waves are multi-reflected. In this present paper, wave propagation generated by a moving train load is evaluated in the time and frequency domains to consider a roadbed structure using an artificial impact load and field measured train load. The results confirmed the wave reflection effect on the pile-slab structure, if the embankment height is sufficient, vibration propagation can be stably restrained, whereas if the height is not sufficient, the vibration amplitude is increased.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.619-629
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• 2013

The objective of this study is to estimate shear wave velocity of earth dam materials using artificially generated vibration from blasting events and to verify its applicability. In this study, the artificial blasting and vibration monitoring were carried out at the site adjacent to Seongdeok dam, which is the first blasting test for an existing dam in Korea. The vibrations were induced by 4 different types of blasting with various depths of blasting boreholes and explosive charge weights. During the tests, the acceleration time histories were recorded at the bedrock adjacent to the explosion and the crest of the dam. From frequency analyses of acceleration histories measured at the crest, the fundamental frequency of the target dam could be evaluated. Numerical analyses varying shear moduli of earth fill zone were carried out using the acceleration histories measured at the bedrock as input ground motions. From the comparison between the fundamental frequencies calculated by numerical analyses and measured records, the shear wave velocities with depth, which are closely related to shear moduli, could be determined. It is found that the effect of different blasting types on shear wave velocity estimation for the target dam materials is negligible and the shear wave velocity can be consistently evaluated. Furthermore, comparing the shear wave velocity with the previous researchers' empirical relationships, the applicability of suggested method is verified. Therefore, in case that the earthquake record is not available, the shear wave velocity of earth dam materials can be reasonably evaluated if blasting vibration test is allowed at the site adjacent to the dam.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.3
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• pp.167-174
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• 2021

Recent investigation into the integrity of nuclear containment buildings has highlighted the importance of developing an elaborate diagnostic method to evaluate the distribution and size of cavities inside concrete walls. As part of developing such a method, this paper presents a finite element approach to modeling elastic waves propagating in the containment building walls of a nuclear power plant. We introduce a perfectly matched layer (PML) wave-absorbing boundary to limit the large-scale nuclear containment wall to the region of interest. The formulation results in a semi-discrete form with symmetric damping and stiffness matrices. The transient elastic wave equations for a mixed unsplit-field PML were solved for displacement and stresses in the time domain. Numerical results show that the sensitivity of displacement, velocity, acceleration, and stresses is large depending on the size and location of the cavity. The dynamic response of the wall slightly differs depending on the existence of the containment liner plate. The results of this study can be applied to a full-waveform inversion approach for characterizing cavities inside a containment wall.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.635-643
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• 1998

A spectral element method(SEM) is introduced for the vibration analysis of a rectangular plate subject to dynamic concentrated loads. First, the spectral plate element is derived from the relations between the forces and displacements along the two opposite edges of plate element. The global spectral matrix equation is then formulated by assembling two spectral plate elements so that the dynamic concentrated load is located at the connection nodal line between two plate elements. the concentrated load is then spatially Fourier transformed in the direction of the connection nodal line to transform the two-dimensional plate problem into a simplified equivalent one-dimensional beam-like problem. We may benefit from these procedures in that the spectral results from the present SEM is compared with the exact analytical solutions to prove the remarkable accuracy of the present SEM, while this is not true for conventional finite element solutions, especially at high frequency.

• Journal of Ocean Engineering and Technology
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• v.26 no.4
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• pp.15-22
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• 2012

In this research, the relationship between the bow shape and green water phenomenon on the bow deck of an FPSO was studied using an experimental method. A 140,000 DWT FPSO was used as the objective hull form in the present research. The incident waves were regular types. The heights were 1.0 and 1.5 times the freeboard, and the length was equal in size to LBP. The wave heights and pressures on the deck were measured in experiments. Model tests were performed to determine the effects of bow flare angles, bow shapes, and a forecastle deck. The free heave and pitch conditions were applied to the models in these experiments. From the results of the model tests, an optimized bow shape was designed, which was found to decrease the green water impact loading. The results of this research could be used as fundamental data in the design of a bow shape.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.181-186
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• 2005

A ship runs with various modes of motion due to waves. Among the modes, roll mainly influences on the safety of cargos on the deck of container ship. In order to protect cargo shifting and turning, securing and lashing system are generally installed. In that case, it is necessary that the force and moment at the connection point of containers should be estimated. Therefore we derived mathematical equations to calculate the forces of securing points and lashing wires. Also we calculated those forces and moments about various lashing patterns.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.5
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• pp.489-495
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• 2016

This study focuses on a detailed ball-bearing model for spur gears. The nonlinear ball-bearing stiffness with radial clearance is derived and calculated. The bearing stiffness is used to the 3-degree-of-freedom (DOF) spur gear system model. The mode characteristics of the gear system model are analyzed and verified by performing finite-element analysis (FEA). From the results, the bearing stiffness on the radial clearance was more sensitive under low-load conditions compared to high-load conditions. The bearing stiffness significantly affected the gear dynamics in the low-frequency region, while the mesh stiffness affected the high natural frequency.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.4
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• pp.93-101
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• 1993

This paper deals tilth an efficient algorithm in spectral fatigue analysis of ship structures. The concept of stress influence coefficients is suggested in order to obtain stress transfer functions efficiently which are the structural responses for unit load components. Strip method is applied to obtain the motion response and pressure distributions exerted on the hull. Since a number of the structural analysis should be performed for the various wave frequencies and heading angles in the spectral analysis, the algorithm developed in this study improves the efficiency of the analysis. Finally, the calculation example with application to this concept is shown in this paper.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.5
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• pp.13-23
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• 2001

In the companion paper, F. E. formulation for the geometric and plastic non-linear analysis of steel jacket structures subjected to wave and earthquake loadings was presented and the main processor was developed. In this paper, the pre/post processor are developed in order to analyze the output results effectively as well as to prepare the input data efficiently. Furthermore, the numerical examples are presented and discussed for linear and non-linear analysis of steel jackets under environmental loadings.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.5
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• pp.105-111
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• 2001

The creep crack growth properties in 3.3NiCrMoV steel were investigated at 55$0^{\circ}C$ by using CT specimen under constant load and constant Ct condition that was held during crack growth of Imm distance. Ct lelied on load line displacement rate, C＊usually increased with crack length though load is reduced in order to maintain constant Ct value as crack growth and appeared scatter band. At constant load and Ct region, crack growth slope was 0.900 and 0.844 each, on the other hand C＊ slope was 0.480. Fully coalesced area(FCA) ahead of crack tip increased as Ct increase to the critical value, and after that value FCA decreased. For the tertiary creep stage of crack growth test, the most of displacement was due to the steady state creep, except only small part due to the primary creep and other effects. Therefore, tests were mainly interrupted in the tertiary stage to obtain high value of Ct.