• Smart Structures and Systems
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• v.29 no.4
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• pp.641-652
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• 2022

High-rise structures prone to large vibrations under the action of strong winds, resulting in fatigue damage of the structural components and the foundation. A novel compound damping cable system (CDCS) is proposed to suppress the excessive vibrations. CDCS uses tailored double cable system with increased tensile stiffness as the connecting device, and makes use of the relative motion between the high-rise structure and the ground to drive the damper to move back-and-forth, dissipating the vibration mechanical energy of the high-rise structure so as to decaying the excessive vibration. Firstly, a third-order differential equation for the free vibration of high-rise structure with CDCS is established, and its closed form solution is obtained by the root formulas of cubic equation (Shengjin's formulas). Secondly, the analytical solution is validated by a laboratory model experiment. Thirdly, parametric analysis is conducted to investigate how the parameters affect the vibration control performance. Finally, the dynamic responses of the high-rise structure with CDCS under harmonic and stochastic excitations are calculated and its vibration mitigation performance is further evaluated. The results show that the CDCS can provide a large equivalent additional damping ratio for the vibrating structures, thus suppressing the excessive vibration effectively. It is anticipated that the CDCS can be used as a good alternative energy dissipation system for vibration control of high-rise structures.

• Wind and Structures
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• v.19 no.5
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• pp.481-503
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• 2014

A new theoretical model on rain-wind induced vibration (RWIV) of a continuous stay cable is developed in this paper. Different from the existing theoretical analyses in which the cable was modeled as a segmental rigid element, the proposed scheme focuses on the in-plane and out-of-plane responses of a continuous stay cable, which is identical with the prototype cable on cable-stayed bridge. In order to simplify the complexities, the motion law of the rivulet on the cable surface is assumed as a sinusoidal way according to some results obtained from wind tunnel tests. Quasi-steady theory is utilized to determine the aerodynamic forces on the cable. Equations of motion of the cable are derived in a Cartesian Coordinate System and solved by using finite difference method to obtain the in-plane and out-of-plane responses of the cable. The results show that limited cable amplitudes are achieved within a limited range of wind velocity, which is a unique characteristic of RWIV of stay cable. It appears that the in-plane cable amplitude is much larger than the out-of-plane cable amplitude. Rivulet frequency, rivulet distribution along cable axis, and mean wind velocity profile, all have significant effects on the RWIV responses of the prototype stay cable. The effects of damping ratio on RWIVs of stay cables are carefully investigated, which suggests that damping ratio of 1% is needed to well mitigate RWIVs of prototype stay cables.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.3
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• pp.219-226
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• 2014

A bus duct system for wind tower is introduced. A marine cable has been widely used in wind tower or various offshore structures. However, as the electric load capacity is increases, large number of cable lines must be used to cover the huge amount of electric capacities. Therefore, the installation of the cable lines becomes very difficult due to the heavy weight and volume of the cables. On the other hand, by using a single bus duct system line, the power capacity amount of 16 cables can be delivered with significantly compacted form. However, unlike flexible cables, the bus duct is relatively stiff which could generate the resonance phenomenon in the operating condition of the wind tower. In this study, the vibration characteristics of the bus duct are investigated and its long-term reliability during the life time of the wind tower is verified.

• Structural Engineering and Mechanics
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• v.38 no.2
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• pp.141-156
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• 2011

A cable stayed bridge under construction has low structural damping and is not as stable as the completed bridge. Control countermeasures, such as the installation of energy dissipating devices, are thus required. In this study, the general procedure and key issues on adopting an active control device, the active mass damper (AMD), for vibration control of cable stayed bridges under construction were studied. Taking a typical cable stayed bridge as the prototype structure; a lab-scale test structure was designed and fabricated firstly. A baseline FEM model was then setup and updated according to the modal parameters measured from vibration test on the structure. A numerical study to simulate the bridge-AMD control system was conducted and an efficient LQG-based controller was designed. Based on that, an experimental implementation of AMD control of the transverse vibration of the bridge model was performed. The results from numerical simulation and experimental study verified that the AMD-based active control was feasible and efficient for reducing dynamic responses of a complex structural system. Moreover, the discussion made in this study clarified some critical problems which should be addressed for the practical implementation of AMD control on real cable-stayed bridges.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.2
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• pp.17-22
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• 2009

Estimate method of cable tension forces can be classified into direct method and indirect method. Direct method is not accuracy and it has many restrictions. Therefore, in generally Indirect method, vibration method using natural frequency, has been applied to estimate the tension forces. In this study, cable tensions of recently constructed cable-stayed bridge are measured using string vibration method and this result comparing with result of multiple mode method. To put it brief, the error of string vibration method is not exceeding 2% under 7th mode. Specially third and 4th mode error is not exceeding 1%. safety.

• Structural Engineering and Mechanics
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• v.72 no.2
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• pp.169-180
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• 2019

The underlying mechanism of the wind-induced vibration of the hangers of the suspension bridges is still not fully understood at present and hence is comprehensively examined in this study. More specifically, a series of field measurements on the No. 2 hanger of the Xihoumen Bridge was first carefully conducted. Large amplitude vibrations of the hanger were found and the oscillation amplitude of the leeward cable was obviously larger than that of the windward cables. Furthermore, the trajectory of the leeward cable was close to an ellipse, which agreed well with the major characteristics of wake-induced vibration. Then, a theoretical model for the wake-induced vibration based on a 3-D continuous cable was established. To obtain the responses of the leeward cable, the finite difference method (FDM) was adopted to numerically solve the established motion equation. Finally, numerical simulations by using the structural parameters of the No. 2 hanger of the Xihoumen Bridge were carried out within the spatial range of $4{\leq}X{\leq}10$ and $0{\leq}Y{\leq}4$ with a uniform interval of ${\Delta}X={\Delta}Y=0.25$. The results obtained from numerical simulations agreed well with the main features obtained from the field observations on the Xihoumen Bridge. This observation indicates that the wake-induced vibration might be one of the reasons for the hanger oscillation of the suspension bridge. In addition, the effects of damping ratio and windward cable movement on the wake-induced vibration of the leeward cable were numerically investigated.

• Journal of the Society of Disaster Information
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• v.13 no.2
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• pp.249-257
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• 2017

Recently, a cable disconnection accident occurred due to a lightning strike at the Seohae Bridge located in Dangjin-Pyeongtaek City. This is a natural occurrence, but it is a recall that it is very important to review the safety issues due to the disconnection of cable bridges. In other words, the role of cables in cable bridges has a profound effect on the safety of the structure, and it has become necessary to grasp the effect on the entire structural system. The cable bridge is an economic bridge that builds the main tower and supports the bottom plate by cable. The influence of the cable is the main member, which is a big influence on the safety of the whole bridge system. In the cable-stayed bridge, the cables exhibit nonlinear behavior because of the change in sag, due to the dead weight of the cable, which occurs with changing tension in the cable resulting from the movement of the end points of the cable as the bridge is loaded. Modal analysis is conducted using the deformed dead-load tangent stiffness matrix. A new concept was presented by using divided a cable into several elements in order to study the effect of the cable vibration (both in-plane and swinging) on the overall bridge dynamics. The result of this study demonstrates the importance of cable vibration on the overall bridge dynamics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.69-72
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• 1998

A study to identify the energized status of the 22.9kV underground power cable by the detection of vibration was reformed. We derived that there exists vibration at double the line frequency in live cables by electromagnetic force. The vibration can be picked up by accelerometer sensor. A prototype was tested on the underground distribution system in Chonan Station, KEPCO. The results are presented and suggest the applicability of the detecting device.

• Structural Engineering and Mechanics
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• v.88 no.4
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• pp.379-387
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• 2023

Wind and earthquake loads may cause strong vibrations in large-span cable-stayed bridges, leading to the inability of the bridge to operate normally. An improved Pounding Tuned Mass Damper (PTMD) system was designed to improve the safety of the large-span cable-stayed bridge. The vibration control effect of the improved PTMD system on the large-span cablestayed bridge under the combined action of earthquake-wind-traffic was studied. Furthermore, the impact of different parameters on the vibration suppression performance of the improved PTMD system was analyzed. The numerical results indicate that the PTMD system is very effective in suppressing the displacements of the bridge caused by both the traffic-wind coupling and traffic-earthquake coupling. Moreover, the number, mass ratio, pounding stiffness, and gap values have a significant influence on the vibration suppression performance of the improved PTMD system. When the number of PTMD is increased from 3 to 9, the vibration reduction ratio of the vertical displacement is increased from 25.39% to 48.05%. As the mass ratio changes from 0.5% to 2%, the vibration reduction ratio increases significantly from 22.23% to 53.30%.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.330-335
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• 2012

A Bus Trunk System for Wind Tower is introduced. A marine cable has been widely used in wind tower or other offshore structure. However, as the electric load capacity is getting increased, the large number of cable lines should be used to cover such a huge amount of electric capacities, which makes the installation make quite difficult due to the heavy weight and volume of the present cables. On the other hand, by using a single bus trunk system line, the power capacity amount of 16 number of cable can be delivered with significant compactness. However, unlike flexible cable, the bus trunk is relatively stiff which could arise resonance phenomenon in the operating condition of wind tower, therefore, the vibration characteristics of bus trunk should be investigated and verify its long-term reliability during the life time of the wind tower.