• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.6
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• pp.311-322
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• 2018

As a method of seismic-design for pile-supported wharves, equivalent static analysis, response spectrum analysis, and time history analysis method are applied. Among them, the response spectrum analysis is widely used to obtain the maximum response of a structure. Because the ground is not modeled in the response spectrum analysis of pile-supported wharves, the amplified input ground acceleration should be calculated by ground classification or seismic response analysis. However, it is difficult to calculate the input ground acceleration through ground classification because the pile-supported wharf is build on inclined ground, the methods to calculate the input ground acceleration proposed in the standards are different. Therefore, in this study, the dynamic centrifuge model tests and the response spectrum analysis were carried out to calculate the appropriate input ground acceleration. The pile moment in response spectrum analysis and the dynamic centrifuge model tests were compared. As a result of comparison, it was shown that the response spectrum analysis results using the amplified acceleration in the ground surface were appropriate.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.408-410
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• 2006

To chase maximum power point at every moment under a conventional MPPT control method, a voltage and current coming out from PV-cell are needed to be feedbacked. So, the structure of control circuit becomes so complex and the MPPT control is in risk of control failure. In the newly developed control method, the current flowing into SPE cell is the only one considerable factor. So, the structure of control circuit becomes simple and the manufacturing cost of the control device decreases. Especially, in case of a huge system of PV-SPE system, because the voltage coming out from PV-cell is not needed to be feed backed, this system can be operated much more safely. In this paper, the PV-SPE system was actually manufactured based on the simulation model of PSCAD/EMTDC program and the results tested were shown. Authors are sure that it is the most useful method to maximize power from PV to SPE with only a feedback of SPE input current.

• Geotechnical Engineering
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• v.4 no.3
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• pp.19-26
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• 1988

A stochastic numerical model for predictions of differential settlement of foundation Eoils is developed in this Paper. The differential settlement is highly dependent on the spatial variability of elastic modulus of soil. The Kriging method is used to account for the spatial variability of the elastic modulus. This technique provides the best linear unbiased estimator of a parameter and its minimum variance from a limited number of measured data. The stochastic finite element method, employing the first-order second-moment analysis for computations of error Propagation, is used to obtain the means, ariances, and covariances of nodal displacements. Finally, a reliability model of differential settlement is proposed by using the results of the stochastic FEM analysis. It is found that maximum differential settlement occurs when the distance between two foundations is approximately same It with the scale of fluctuation in horizontal direction, and the probability that differential settlement exceeds the allot.able vague might be significant.

• Journal of computational fluids engineering
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• v.21 no.2
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• pp.1-11
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• 2016

Considerable efforts are required to develop a monotone, robust and stable high-order numerical scheme for solving the hyperbolic system. The discontinuous Galerkin(DG) method is a natural choice, but elimination of the spurious oscillations from the high-order solutions demands a new development of proper limiters for the DG method. There are several available limiters for controlling or removing unphysical oscillations from the high-order approximate solution; however, very few studies were directed to analyze the exact role of the limiters in the hyperbolic systems. In this study, the performance of the several well-known limiters is examined by comparing the high-order($p^1$, $p^2$, and $p^3$) approximate solutions with the exact solutions. It is shown that the accuracy of the limiter is in general problem-dependent, although the Hermite WENO limiter and maximum principle limiter perform better than the TVD and generalized moment limiters for most of the test cases. It is also shown that application of the troubled cell indicators may improve the accuracy of the limiters under some specific conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.178-188
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• 2007

In this paper, a half-scaled substructure test was performed to evaluate the buckling and structural safety of an existing transmission tower subjected to wind load. A loading scheme was devised to reproduce the dead and wind loads of a prototype transmission tower, which uses a triangular jig that is mounted on the reduced model to which the similarity law of a half length was applied. As a result of the preliminary numerical analysis carried out to evaluate the stability of a specimen for the design load, it was confirmed that the calculated axial forces of tower leg members were distributed to $80{\sim}90%$ of an admissible buckling load. When the substructured transmission tower was loaded by 270% of its maximum admissible buckling load, it was failed due to the local buckling that is occurred in joints with weak constraints for out-of-plane behavior of leg members. By inspection of load-displacement curves, displacements and strains of members, it is considered that this local buckling was due to additional eccentric force by unbalanced deformation because the time that is reached to yielding stress due to the bending moment is different at each point of a same section.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.329-330
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• 2008

The 181,000 DWT Bulk Carrier has a different deck house type, which is not typical for previous bulk carriers, to meet the new international rules for bulk carriers. This new deck house has much smaller transverse breadth than the hull's transverse breath, resulting in large levels of the transverse response of the deck house. In addition, the longitudinal response of the funnel showed rather a large magnitude of vibration, which are excited by the ship's main excitations such as the main engine H-moment and the propeller surface forte when the ship operates at the NCR and the MCR speeds In the ballast condition. To solve these issues, the global forced vibration analysis has been performed for the ship and the ship structure has been modified to reduce the vibration level by increasing the girder depth and adjusting the engine room tank arrangement.

• Korean Journal of Applied Biomechanics
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• v.20 no.1
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• pp.49-55
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• 2010

The purpose of the study was to analyze kinetic factors required to the three-point jump shot of the basketball games through 3-D analysis and ground reaction force(GRF) analysis. Six university male players participated in this study. The results of the study were showed that (1) resultant velocity in the center of mass(COM) was $0.84{\pm}0.27\;m/s$ since a player didn't shot a ball in the highest peak and shot ball at the moment of going up forward and vertical movement. Therefore, it is necessary to find a proper timing to shot a ball; (2) the angular velocity was largely increased in upper arm and fore arm out of the upper-limb segments and the hands had the largest angular velocity since the body is in a fixed situation and angular speed is rapidly increased by the wrist' snap with the rapid movement of upper arm and forearm at the time of release a ball; (3) it is judged that a player can shot a ball at the accurate and high release point when the player collects power vertically to the maximum by keeping GRF to the right and the rear in a proper way and by keeping the body's balance so that a large power may not be dispersed.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.12
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• pp.88-94
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• 2007

A flexure hinge-based compliant stage driven by stack-type piezoelectric elements has high precision motion but small operational range due to the characteristics of the piezoelectric element. Since the common flexure hinges can be broken by excessive deflection when the displacement is amplified by a high amplification ratio, a flexure hinge mechanism for large deflection is required. A cartwheel-type flexure hinge has an advantage of larger deflection compared with the common flexure hinges. This study presents a rotation stage with cartwheel-type flexure hinges driven by a stack-type piezoelectric element. The characteristics and the performance of the rotation stage are described by the terms of principal resonance frequency, amplification ratio of rotational displacement, maximum rotational displacement and block moment, in which the terms are analyzed by geometric parameters of the rotation stage. The analyzed results will be used as the guideline of the design of the rotation stage.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.742-745
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• 2004

The FRP-concrete composite deck system has advantages of corrosion free and easy construction. The system is, however, comprised of two brittle materials, so that it suffers from inherent disadvantage of lack of ductility. In this study, some conceptual design is presented for preventing the brittle failure of FRP-concrete composite deck at ultimate load level. 4-point bending tests are performed for FRP-concrete composite beams using FRC(Fiber Reinforced Concrete). The specimens use the box-shape FRP member in the lower portion. Four types of concrete with different compressive strengths and ductilities including normal mortar and 3 FRCs are placed in the upper portion. Typical failure mode in the test is identified; Concrete compressive failure occurs first at the maximum moment region, and the interfacial debonding between FRP and concrete member proceeds. Finally, the tensile rupture of FRP member occurs. The specimen using FRC with the high compressive ductility of concrete fails with less brittle manner than other specimens. The reason is that the ductility from the concrete in compression prevents the sudden loss of load-carrying capacity after compressive concrete failure.

• Journal of Ocean Engineering and Technology
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• v.1 no.1
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• pp.57-64
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• 1987

Methods of nonlinear stochastic analysis of guyed towers are studied in this paper. Two different kinds of nonlinearities are considered. They are the nonlinear restoring force from the guying system and the nonlinear hydrodynamic force. Analyses are carried out mainly in the frequency domain using linearization techniques. Two methods for the linearization of the nonlinear stiffness are presented, in which the effects of the steady offset and the oscillating component of the structural motion can be adequately analyzed. those two methods are the equivalent linearization method and the average stiffness method. The linearization of the nonlinear drag force is also carried out considering the effect of steady current as well as oscillatory wave motions. Example analyses are performed for guyed tower in 300m water. Transfer functions and the expected maximum values of the deck displacement and the bending moment near the middle of the tower are calculated. Numerical results show that both of the frequency domain methods presented in this paper predict the responses of the sturcture very reasonably compared with those by the time integration method utilzing the random simulations wave particla motions.