• Wind and Structures
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• v.22 no.2
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• pp.235-252
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• 2016

A wind velocity power spectrum (WVPS) with high fidelity is extremely important for accurate prediction of structural buffeting response. WVPS heavily depends on the geographical locations, local terrains and topographies. Hence, field measurement of wind characteristics may be the unique way to obtain the accurate WVPS for a specific region. In this paper, a systematic analysis and discussions of existing WVPSs were performed. Six recorded strong wind data from the structural health monitoring systems (SHMS) of Runyang Suspension Bridge (RSB) and Sutong Cable-stayed Bridge (SCB) in Jiangsu Province of China were selected for analysis. The measured and pre-processed wind velocity data was first transformed from time domain to frequency domain to obtain the measured spectrum. The spectrum for each strong wind was then fitted using the nonlinear least square method and compared with both the fitted spectrum from statistical analysis and the recommended spectrum in specifications. The modified Kaimal spectrum was proved to be the "best" choice for the coastal area of East Jiangsu Province. Finally, a suitable WVPS formula fit for the coastal area of East Jiangsu Province was presented based on the modified Kaimal spectrum. Results in this study provide a more accurate and reliable WVPS for wind-resistant design of engineering structures in the coastal area of East Jiangsu Province.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.1
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• pp.49-57
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• 2021

In the production power transmitting of a floating production system like a wind offshore floating, the power cable should be connected from the surface system into the subsea system. The connection between the surface and the subsea system will make the power cable get a dynamic load like current and wave forces. Based on this condition, a dynamic power cable is required to endure external physical force and vibration in the long-term condition. It needs more requirements than static power cable for mechanical fatigue properties to prevent failures during operations in marine environments where the external and internal loads work continuously. As a process to verify, the durability test of dynamic power cables under the marine operation environment condition was carried out by using domestic technology development.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.64-67
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• 2005

A vibration monitoring system for a small size wind turbine (WIT) is established and operated. The monitoring system consists of monolithic integrated chip accelerometer for vibration monitoring, anemometers for wind data acquisition and auxiliary sensors for atmospheric data. Using the monitoring system, vibration response of a 6kW stand alone WIT generator is investigated. Acceleration data of the WIT tower under various operation condition is acquired in real time using LabVIEW and the data are remotely transferred from the test site to the laboratory in school by internet. Vibration response characteristics of the tower structure are diagnosed in the aspect of stability of W/T. Wind data and electrical power performance are also investigated with the stability problem.

• Wind and Structures
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• v.7 no.3
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• pp.173-186
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• 2004

Flutter derivatives provide the basis of predicting the critical wind speed in flutter and buffeting analysis of long-span cable-supported bridges. In this paper, one popular stochastic system identification technique, covariance-driven Stochastic Subspace Identification(SSI in short), is firstly presented for estimation of the flutter derivatives of bridge decks from their random responses in turbulent flow. Secondly, wind tunnel tests of a streamlined thin plate model and a ${\Pi}$ type blunt bridge section model are conducted in turbulent flow and the flutter derivatives are determined by SSI. The flutter derivatives of the thin plate model identified by SSI are very comparable to those identified by the unifying least-square method and Theodorson's theoretical values. As to the ${\Pi}$ type section model, the effect of turbulence on aerodynamic damping seems to be somewhat notable, therefore perhaps the wind tunnel tests for flutter derivative estimation of those models with similar blunt sections should be conducted in turbulent flow.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.239-240
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• 2015

This paper presents the transient state characteristic and single phase ground fault occurred by deterioration of surge arrester when offshore wind turbine is struck by lightning strike. The wind turbine and submarine cable data are based on the 2.5GW offshore wind farm planned in South Korea Southwest Seashore. During lightning strikes, additional ground fault can lead to damage of the generation components. So, the sensitive analyses are conducted in order to investigate the effects of lightning strike on offshore wind farm.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.645-654
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• 2011

Temporal supports is proposed for the large block construction of a double-deck truss girder of a bundle type cable-stayed bridge. The design force of the temporal bents cannot be evaluated by a conventional design procedure with gust factored static wind loads. The uplift forces in BS5400 also can not estimate the design forces of the temporal bents properly for the turbulent wind loads. A frequency-domain buffeting analysis is performed to evaluate the design forces of the temporal bents considering the interactions between the girder and temporal supports. Two cases of modeling are compared to estimate the stiffness contribution of temporal supports in determining design forces, i.e., an analysis model including temporal bents in the structural analysis modeling and an analysis model with fixed supports at the bent tops neglecting the stiffness of temporal bents. The consideration of bent stiffness usually generates smaller reaction forces than rigid support modeling. Consequently, the effectiveness and usefulness of the buffeting analysis procedure with full modeling of temporal supports are demonstrated for the design of a temporal bents of the construction of a bundle type cable-stayed bridge.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.5
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• pp.815-824
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• 2022

The growing integration of intermittent renewable sources like offshore wind energy increases the need for transferring electric energy over long distances, which may include sea crossings. One of the solutions available for bulk electric power transmission across large distances encompassing wide and deep sea is using HVDC submarine power cables. However, there are no standards or research related to the calculation of the continuous allowable current with various ocean conditions of a DC power cable that does not have an alternating magnetic field. In this study, assuming the typical two types of subsea cable models and two areas of the south coast and the west coast marine conditions, a continuous allowable current simulation of DC cables was performed. As a simulation result, the DC cable continuous allowable current find out the gradient reduction characteristics based on subsea base depth.

• Smart Structures and Systems
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• v.23 no.6
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• pp.695-702
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• 2019

The number of cable-stayed bridges has been increasing worldwide, causing issues in maintaining the structural safety and integrity of bridges. The stay cable, one of the most critical members in cable-stayed bridges, is vulnerable to wind-induced vibrations owing to its inherent low damping capacity. Thus, vibration mitigation of stay cables has been an important issue both in academia and practice. While a semi-active control scheme shows effective vibration reduction compared to a passive control scheme, real-world applications are quite limited because it requires complicated equipment, including for data acquisition, and power supply. This study aims to develop an Arduino-based integrated cable vibration control system implementing a semi-active control algorithm. The integrated control system is built on the low-cost, low-power Arduino platform, embedding a semi-active control algorithm. A MEMS accelerometer is installed in the platform to conduct a state feedback for the semi-active control. The Linear Quadratic Gaussian control is applied to estimate a cable state and obtain a control gain, and the clipped optimal algorithm is implemented to control the damping device. This study selects the magnetorheological damper as a semi-active damping device, controlled by the proposed control system. The developed integrated system is applied to a laboratory size cable with a series of experimental studies for identifying the effect of the system on cable vibration reduction. The semi-active control embedded in the integrated system is compared with free and passive mode cases and is shown to reduce the vibration of stay-cables effectively.

• Proceedings of KOSOMES biannual meeting
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• 2018.06a
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• pp.114-114
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• 2018

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.246-252
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• 2000

The nonlinearity of a cable-stayed bridge results in the large displacement of main girder due to a long span, the large axial forces reduce the catenary action of cables and the flexural stiffness. Therefore, the static and dynamic behavior of pylon for a cable-stayed bridge plays an important role in determining its safety. This study was performed to find the behavior of pylon of cable-stayed bridge for the first-order analysis considering of axial load only and for the second-order analysis considering of lateral deflection due to axial load. The axial force and moment values of pylon were different from the results of the first-order analysis and second-order analysis according to pylon shape and cross beam stiffness when the pylon was subjected to earthquake and wind loads. In the second-order analysis, comparing the numerical values of the member forces for the dynamic analysis, types 3 and 4 (A type) were relatively more advantageons types than types 1 and 2 (H type). Considering the stability for pylon of cable-stayed bridge (whole structural system), types 3 and 4 (A type) with pre-buckling of girder were proper types than types 1 and 2 (H type) with buckling of pylon.