• Title, Summary, Keyword: cable stiffness

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Response evaluation and vibration control of a transmission tower-line system in mountain areas subjected to cable rupture

  • Chen, Bo;Wu, Jingbo;Ouyang, Yiqin;Yang, Deng
    • Structural Monitoring and Maintenance
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    • v.5 no.1
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    • pp.151-171
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    • 2018
  • Transmission tower-line systems are commonly slender and generally possess a small stiffness and low structural damping. They are prone to impulsive excitations induced by cable rupture and may experience strong vibration. Excessive deformation and vibration of a transmission tower-line system subjected to cable rupture may induce a local destruction and even failure event. A little work has yet been carried out to evaluate the performance of transmission tower-line systems in mountain areas subjected to cable rupture. In addition, the control for cable rupture induced vibration of a transmission tower-line system has not been systematically conducted. In this regard, the dynamic response analysis of a transmission tower-line system in mountain areas subjected to cable rupture is conducted. Furthermore, the feasibility of using viscous fluid dampers to suppress the cable rupture-induced vibration is also investigated. The three dimensional (3D) finite element (FE) model of a transmission tower-line system is first established and the mathematical model of a mountain is developed to describe the equivalent scale and configuration of a mountain. The model of a tower-line-mountain system is developed by taking a real transmission tower-line system constructed in China as an example. The mechanical model for the dynamic interaction between the ground and transmission lines is proposed and the mechanical model of a viscous fluid damper is also presented. The equations of motion of the transmission tower-line system subjected to cable rupture without/with viscous fluid dampers are established. The field measurement is carried out to verify the analytical FE model and determine the damping ratios of the example transmission tower-line system. The dynamic analysis of the tower-line system is carried out to investigate structural performance under cable rupture and the validity of the proposed control approach based on viscous fluid dampers is examined. The made observations demonstrate that cable rupture may induce strong structural vibration and the implementation of viscous fluid dampers with optimal parameters can effectively suppress structural responses.

Abnormal Response Analysis of a Cable-Stayed Bridge using Gradual Bilinear Method (Gradual Bilinear Method를 이용한 사장교의 케이블 손상응답 해석)

  • Kim, Byeong-Cheol;Park, Ki-Tae;Kim, Tae-Heon;Hwang, Ji-Hyun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.18 no.6
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    • pp.60-71
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    • 2014
  • Cable-stayed bridge, which is one of the representative long-spanned bridge, needs prompt maintenances when a stay cable is damaged because it may cause structural failure of the entire bridge. Many researches are being conducted to develop abnormal behavior detection algorithms for the purpose of shortening the reaction time after the occurrence of structural damage. To improve the accuracy of the damage detection algorithm, ample observation data from various kinds of damage responses is needed. However, it is difficult to measure an abnormal response by damaging an existing bridge, numerical simulation can be an effective alternative. In most previous studies, which simulate the damage responses of a cable-stayed bridge, the damages has been considered as a load variation without regard to its stiffness variation. The analyses of using these simplification could not calculate exact responses of damaged structure, though it may reserve a sufficient accuracy for the purpose of bridge design. This study suggests Gradual Bilinear Method (GBM) which simulate the damage responses of cable-stayed bridge considering the stiffness and mass variation, and develops an analysis program. The developed program is verified from the responses of a simple model. The responses of a existing cable-stayed bridge model are analyzed with respect to the fracture delay time and damage ratio. The results of this study can be used to develop and verify the highly accurate abnormal behavior detection algorithm for safety management of architecture/large structures.

Design to Control Vibration for Stay Cable with Damper (댐퍼도입에 의한 사장 케이블의 제진설계)

  • Kim, Hyeon Kyeom;Hwang, Jae Woong;Lee, Myeong Jae;Seo, Ju Won
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.1A
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    • pp.51-58
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    • 2008
  • A cable element happens to vibration easily rather than other elements because a cable element has few rotational stiffness. Dynamic motion of stay cable is distinguished from vibration by wind and/or rain and excitation by support movement. Mostly a stay cable is vibrated by wind and/or rain except that when natural periods coincide between stiffening girder and stay cable. It happens to deterioration of serviceability and durability by vortex shedding, rainy-wind induced vibration, and galloping. Additional damping generated by installation of cable damper is well known good scheme against above phenomena. Researchers have lack of effort to develop the recommendations even if cable stayed bridges are designed and constructed in Korea. Therefore, development of the domestic recommendations should be achieved as soon as possible. This study suggests the consistent and systematic recommendations on vibration controlling design of stay cable by installation of damper. It gives readers two important methodologies that one evaluates required damping ratio, the other determines installing point considering efficiency.

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Theoretical and experimental research of external prestressed timber beams in variable moisture conditions

  • Miljanovic, Sladana;Zlatar, Muhamed
    • Coupled systems mechanics
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    • v.4 no.2
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    • pp.191-209
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    • 2015
  • Hybrid girders can be constructed in different geometrical forms and from different materials. Selection of beam's effective constellation represents a complex process considering the variations of geometrical parameters, changes of built in material characteristics and their mutual relations, which has important effect on the behavior of the girder. This paper presents the theoretical and experimental research on behavior of the timber-steel hybrid girders' different geometrical constellation with external prestressing and in different conditions of timber moisture. These researches are based on linear elastic analysis, and further refine by using the plasticity and damage models.

Experimental evaluation of an inertial mass damper and its analytical model for cable vibration mitigation

  • Lu, Lei;Fermandois, Gaston A.;Lu, Xilin;Spencer, Billie F. Jr.;Duan, Yuan-Feng;Zhou, Ying
    • Smart Structures and Systems
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    • v.23 no.6
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    • pp.589-613
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    • 2019
  • Cables are prone to vibration due to their low inherent damping characteristics. Recently, negative stiffness dampers have gained attentions, because of their promising energy dissipation ability. The viscous inertial mass damper (termed as VIMD hereinafter) can be viewed as one realization of the inerter. It is formed by paralleling an inertial mass part with a common energy dissipation element (e.g., viscous element) and able to provide pseudo-negative stiffness properties to flexible systems such as cables. A previous study examined the potential of IMD to enhance the damping of stay cables. Because there are already models for common energy dissipation elements, the key to establish a general model for IMD is to propose an analytical model of the rotary mass component. In this paper, the characteristics of the rotary mass and the proposed analytical model have been evaluated by the numerical and experimental tests. First, a series of harmonic tests are conducted to show the performance and properties of the IMD only having the rotary mass. Then, the mechanism of nonlinearities is analyzed, and an analytical model is introduced and validated by comparing with the experimental data. Finally, a real-time hybrid simulation test is conducted with a physical IMD specimen and cable numerical substructure under distributed sinusoidal excitation. The results show that the chosen model of the rotary mass part can provide better estimation on the damper's performance, and it is better to use it to form a general analytical model of IMD. On the other hand, the simplified damper model is accurate for the preliminary simulation of the cable responses.

A Study on the Axial Stiffness Prediction of Stand Using Analysis of Variance (분산분석을 이용한 스트랜드의 축강성 예측에 관한 연구)

  • Park, Yong-Dae;Yang, Won-Ho;Heo, Seong-Pil;Seong, Gi-Deuk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.1
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    • pp.127-134
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    • 2001
  • Wire ropes are widely used in cable car, suspension bridge and elevator, etc. and composed of single or multi-layer strands. It is difficult to find out the characteristics of a strand or wire rope because of complicated geometry and contact condition. In this study, the axial stiffness is evaluated using finite element method and reliable finite element analysis model is presented, taking into consideration the convergence on the length. The axial stiffness predictive equation of a strand is developed using analysis of variance, which can be applicable for characterizing the relationship between load and displacement when the strand configuration is determined.

Guidelines of Designing LRB for a Seismically Excited Cable-Stayed Bridge (지진 하중을 받는 사장교를 위한 납고무 받침의 설계 기준 제안)

  • 이성진;박규식;김운학;이인원
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.326-333
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    • 2003
  • Most long-span bridges such as a cable-stayed bridges have a number of long-period modes due to the flexibility, thus the design concept extending the natural period of structures using base isolation system may be difficult to use directly to these structures. But, the effectiveness of LRB for cable-stayed bridges is indicated in several papers. In this study, the guidelines of designing LRB for a seismically excited cable-stayed bridge using benchmark cable-stayed bridge are presented. The design properties of LRB are chosen that the design index(DI) is minimized or little changed for variation of properties. And the seismic performance of designed LRB is also investigated. The consequences show that the perforamnce of designed LRB is better than that of simply designed LRB for several history earthquakes. Moreover, the design properties of LRB are researched to several diffrent dominant frequency of earthquake. The results present that the plastic and elastic stiffness of LRB are affected by the dominant frequency of earthquake.

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Guidelines of Designing Lead Rubber Bearing for a Cable-Stayed Bridge In Control Seismic Response (사장교의 지진 응답 제어를 위한 납고무 받침의 설계 기준 제안)

  • 이성진;박규식;김춘호;이인원
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.509-516
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    • 2003
  • In tile design of base isolation system for building and short-span bridge, shift of the natural period of the structure is main objective. But, most long-span bridges such as a cable-stayed bridges have a number of long-period modes due to their flexibility and small structural damping. thus the design concept of base isolation system for building and short-span brigde may be difficult to use directly to these structures. However, the effectiveness of LRB for cable-stayed bridges is indicated by Ali and Abdel-Ghaffar. In this study, the design procedure and guidelines of LRB for a seismically excited cable-stayed bridge are investigated. The design properties of LRB are chosen that the design index(DI) is minimized or little changed for variation of properties. This result show that the stiffer rubber and bigger lead core size are need to cable-stayed bridges. And the seismic performance of designed LRB is also investigated. The consequences show that the perforamnce of designed LRB is better than that of Naeim-Kelly mettled designning LRB for general building structures. Moreover, the design properties of LRB are researched to several diffrent dominant frequency of earthquake. The results present that the plastic and elastic stiffness of LRB are affected by the dominant frequency of earthquake.

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System identification of the suspension tower of Runyang Bridge based on ambient vibration tests

  • Li, Zhijun;Feng, Dongming;Feng, Maria Q.;Xu, Xiuli
    • Smart Structures and Systems
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    • v.19 no.5
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    • pp.523-538
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    • 2017
  • A series of field vibration tests are conducted on the Runyang Suspension Bridge during both the construction and operational stages. The purpose of this study is devoted to the analysis of the dynamic characteristics of the suspension tower. After the tower was erected, an array of accelerometers was deployed to study the evolution of its modal parameters during the construction process. Dynamic tests were first performed under the freestanding tower condition and then under the tower-cable condition after the superstructure was installed. Based on the identified modal parameters, the effect of the pile-soil-structure interaction on dynamic characteristics of the suspension tower is investigated. Moreover, the stiffness of the pile foundation is successfully identified using a probabilistic finite model updating method. Furthermore, challenges of identifying the dynamic properties of the tower from the coupled responses of the tower-cable system are discussed in detail. It's found that compared with the identified results from the freestanding tower, the longitudinal and torsional natural frequencies of the tower in the tower-cable system have changed significantly, while the lateral mode frequencies change slightly. The identified modal results from measurements by the structural health monitoring system further confirmed that the vibrations of the bridge subsystems (i.e., the tower, the suspended deck and the main cable) are strongly coupled with one another.

Study of structural parameters on the aerodynamic stability of three-tower suspension bridge

  • Zhang, Xin-Jun
    • Wind and Structures
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    • v.13 no.5
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    • pp.471-485
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    • 2010
  • In comparison with the common two-tower suspension bridge, due to the lack of effective longitudinal restraint of the center tower, the three-tower suspension bridge becomes a structural system with greater flexibility, and more susceptible to the wind action. By taking a three-tower suspension bridge-the Taizhou Bridge over the Yangtze River with two main spans of 1080 m as example, effects of structural parameters including the cable sag to span ratio, the side to main span ratio, the deck's dead load, the deck's bearing system, longitudinal structural form of the center tower and the cable system on the aerodynamic stability of the bridge are investigated numerically by 3D nonlinear aerodynamic stability analysis, the favorable structural system of three-tower suspension bridge with good wind stability is discussed. The results show that good aerodynamic stability can be obtained for three-tower suspension bridge as the cable sag to span ratio is assumed ranging from 1/10 to 1/11, the central buckle are provided between main cables and the deck at midpoint of main spans, the longitudinal bending stiffness of the center tower is strengthened, and the spatial cable system or double cable system is employed.