scholarly journals Performance Evaluation on Transmission Tower-Line System with Passive Friction Dampers Subjected to Wind Excitations

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Bo Chen ◽  
Xiang Xiao ◽  
Peng-yun Li ◽  
Wan-li Zhong
Keyword(s):  
Performance Evaluation ◽  
Axial Stiffness ◽  
Parameter Study ◽  
Fe Model ◽  
Optimal Parameters ◽  
Friction Damper ◽  
Transmission Tower ◽  
Lumped Mass ◽  
Line System ◽  
Friction Dampers

The vibration control and performance evaluation on a transmission-tower line system by using friction dampers subjected to wind excitations are carried out in this study. The three-dimensional finite element (FE) model of a transmission tower is firstly constructed. A two-dimensional lumped mass model of a transmission tower is developed for dynamic analysis. The analytical model of transmission tower-line system is proposed by taking the dynamic interaction between the tower and the transmission lines into consideration. The mechanical model of passive friction damper is presented by involving the effects of damper axial stiffness. The equation of motion of the transmission tower-line system incorporated with the friction dampers disturbed by wind excitations is established. A real transmission tower-line system is taken as an example to examine the feasibility and reliability of the proposed control approach. An extensive parameter study is carried out to find the optimal parameters of friction damper and to assess the effects of slipping force axial stiffness and hysteresis loop on control performance. The work on an example structure indicates that the application of friction dampers with optimal parameters could significantly reduce wind-induced responses of the transmission tower-line system.

Response control of a large transmission tower-line system under seismic excitations using friction dampers

2016 ◽  
Vol 20 (8) ◽  
pp. 1155-1173 ◽  
Author(s):  
Bo Chen ◽  
Shun Weng ◽  
Lunhai Zhi ◽  
Dongming Li
Keyword(s):  
Axial Stiffness ◽  
Control Force ◽  
Friction Damper ◽  
Transmission Tower ◽  
Lumped Mass ◽  
Seismic Excitations ◽  
Response Control ◽  
Line System ◽  
Strong Earthquakes ◽  
Friction Dampers

The transmission tower-line system is widely used in electric infrastructures across the world and generally possesses a small stiffness and low structural damping. The excessive vibration of a transmission tower-line system subjected to seismic excitations may induce a structural damage or failure. To avoid the excessive vibration under strong earthquakes, a large transmission tower-line system requires some measures to abate their dynamic responses. Friction damper is a solution to realize the response control of a transmission tower-line system. In this regard, the response mitigation and performance assessment on a transmission tower-line system with friction dampers under strong earthquakes are actively carried out in this study. The analytical model of a transmission line is proposed based on Hamilton’s variational statement of dynamics and Lagrange’s formulation. A two-dimensional lumped mass model of a transmission tower is developed for the dynamic analysis by simplifying the three-dimensional finite element model. The mechanical model of a friction damper is established by considering the effect of damper axial stiffness. The equations of motion and dynamic analytical method of a transmission tower-line system without/with friction dampers subjected to seismic excitations are proposed. In addition, the approach for assessing energy responses of a transmission tower-line system without/with friction dampers subjected to seismic excitations is also developed. A real transmission tower-line system is taken as an example to examine the feasibility of the proposed control approach. The parametric study is conducted to investigate the effects of damper control force, damper stiffness, earthquake intensity, and damper location. The made observations demonstrate that the implementation of friction dampers in a transmission tower-line system can substantially suppress the seismic responses with optimal damper parameters.

Radial Buckling of Tensile Armor Wires in Subsea Flexible Pipe—Numerical Assessment of Key Factors

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Alireza Ebrahimi ◽  
Shawn Kenny ◽  
Amgad Hussein
Keyword(s):  
Three Dimensional ◽  
External Pressure ◽  
Axial Stiffness ◽  
Parameter Study ◽  
Fe Model ◽  
Key Factors ◽  
Flexible Pipe ◽  
Analysis And Design ◽  
Axial Forces ◽  
Out Of Plane

Flexible pipes can be used as risers, jumpers, and flowlines that may be subject to axial forces and out-of-plane bending motion due to operational and environmental loading conditions. The tensile armor wires provide axial stiffness to resist these loads. Antibirdcaging tape is used to provide circumferential support and prevent a loss of stability for the tension armor wires, in the radial direction. The antibirdcaging tape may be damaged where a condition known as “wet annulus” occurs that may result in the radial buckling (i.e., birdcaging mechanism) of the tensile armor wires. A three-dimensional continuum finite element (FE) model of a 4 in. flexible pipe is developed using abaqus/implicit software package. As a verification case, the radial buckling response is compared with similar but limited experimental work available in the public domain. The modeling procedures represent an improvement over past studies through the increased number of layers and elements to model contact interactions and failure mechanisms. A limited parameter study highlighted the importance of key factors influencing the radial buckling mechanism that includes external pressure, internal pressure, and damage, related to the percentage of wet annulus. The importance of radial contact pressure and shear stress between layers was also identified. The outcomes may be used to improve guidance in the engineering analysis and design of flexible pipelines and to support the improvement of recommended practices.

scholarly journals Dynamic Responses and Vibration Control of the Transmission Tower-Line System: A State-of-the-Art Review

2014 ◽  
Vol 2014 ◽  
pp. 1-20 ◽  
Author(s):  
Bo Chen ◽  
Wei-hua Guo ◽  
Peng-yun Li ◽  
Wen-ping Xie
Keyword(s):  
Dynamic Analysis ◽  
Vibration Control ◽  
Dynamic Responses ◽  
Analytical Models ◽  
Equivalent Model ◽  
Wind Loading ◽  
Fe Model ◽  
Transmission Tower ◽  
Tuned Mass Dampers ◽  
Line System

This paper presented an overview on the dynamic analysis and control of the transmission tower-line system in the past forty years. The challenges and future developing trends in the dynamic analysis and mitigation of the transmission tower-line system under dynamic excitations are also put forward. It also reviews the analytical models and approaches of the transmission tower, transmission lines, and transmission tower-line systems, respectively, which contain the theoretical model, finite element (FE) model and the equivalent model; shows the advances in wind responses of the transmission tower-line system, which contains the dynamic effects under common wind loading, tornado, downburst, and typhoon; and discusses the dynamic responses under earthquake and ice loads, respectively. The vibration control of the transmission tower-line system is also reviewed, which includes the magnetorheological dampers, friction dampers, tuned mass dampers, and pounding tuned mass dampers.

scholarly journals Shaking Table Array Tests of an Ultra-High-Voltage Cup-Type Transmission Tower-Line System

2019 ◽  
Vol 2019 ◽  
pp. 1-20 ◽  
Author(s):  
Fei Wang ◽  
Ke Du ◽  
Jingjiang Sun ◽  
Fuyun Huang ◽  
Zhenghui Xiong
Keyword(s):  
Ground Motion ◽  
Transmission Lines ◽  
Shaking Table ◽  
Transmission Tower ◽  
Acceleration Response ◽  
Lumped Mass ◽  
Line System ◽  
Transmission Towers ◽  
Tower Model ◽  
Line Coupling

Ultra-high-voltage (UHV) cup-type transmission towers supported with long-span transmission lines are unavoidably subjected to the coupling action between the towers and the transmission lines. Therefore, investigating how tower-line coupling affects UHV cup-type transmission towers is important. In this study, three shaking table array tests of an UHV cup-type transmission tower-line system were carried out to investigate the dynamic characteristics of the coupling action between the towers and transmission lines based on the following four comparative models: a single-tower model, a single-tower model with suspended lumped masses, a three-tower-two-line model, and a five-tower-four-line model. The test results demonstrated that the tower-line coupling interaction had a significant effect on the dynamic characteristics and seismic responses, as the suspended conductor line and the suspended lumped mass decreased the frequency of the transmission tower. Under longitudinal ground motion, the model with the suspended lumped mass had the lowest peak acceleration response and the largest peak displacement response. Under the same ground motion, the four models had similar peak strains in the longitudinal direction. Under transverse-the-line ground motion, the model with the suspended lumped mass had the lowest peak acceleration response and the smallest peak responses for displacement and strain in the transverse direction; therefore, this model is inappropriate for the simulation and seismic evaluation of transmission tower-line systems.

Performance evaluation of a special 6-PUS type parallel manipulator

Robotica ◽  
2021 ◽  
pp. 1-15
Author(s):  
Xiaochu Liu ◽  
Yunfei Cai ◽  
Weitian Liu ◽  
Linlong Zhang ◽  
Chengxin Hu
Keyword(s):  
Performance Evaluation ◽  
Natural Frequency ◽  
Parallel Manipulator ◽  
Screw Theory ◽  
Shaking Table ◽  
Axial Stiffness ◽  
Neutral Position ◽  
Dynamics Model ◽  
Force Transmissibility ◽  
Kane Method

Abstract In this paper, a special 6-PUS parallel manipulator (PM) is utilized as a shaking table. Unlike the existing results about 6-PUS PMs, we make the actuator direction collinear with the linkage direction at neutral position. With respect to the application background, a further analysis of the special PM is carried out from the perspective of motion/force transmissibility, natural frequency and acceleration capability. Specially, the complete dynamics model is established based on the Kane method. Then, generalized transmission indices based on the screw theory are utilized to reflect its motion ability, and a model of natural frequency is proposed with the axial stiffness of linkages considered. Finally, the effect of the angle between the actuator direction and the linkage direction α on various performances is analyzed, and other results are included to illustrate its feasibility and usability.

Study on bearing stiffness characteristics with residual stress in carburized layer

2020 ◽  
pp. 095440622096079
Author(s):  
Junshuai Liang ◽  
Ning Li ◽  
Jingyu Zhai ◽  
BaoGang Wen ◽  
Qingkai Han ◽  
...  
Keyword(s):  
Residual Stress ◽  
Contact Stiffness ◽  
Roller Bearing ◽  
High Load ◽  
Axial Stiffness ◽  
Fe Model ◽  
Low Load ◽  
Bearing Stiffness ◽  
Carburized Layer ◽  
Stiffness Characteristics

In this study, a layering method of carburized ring is presented. A finite element (FE) model for analyzing bearing stiffness characteristics is established considering the residual stress in the carburized layer. The residual stress in the carburized layer of a double-row conical roller bearing is tested and the influence of the distribution of residual stress in carburized layer on the bearing stiffness is investigated. Results show that the residual stress in the carburized layer increases the contact stiffness of the bearing by 5% in the low-load zone and 3% in the high-load zone. The radial stiffness of the bearing is increased by 5% in the low-load zone and 3% in the high-load zone. The axial stiffness is increased by 6%, and the angular stiffness increased by 4%. The larger the thickness of the carburized layer, the greater the residual compressive stress in the carburized layer, the deeper the position of the maximum residual stresses in the carburized layer will lead to the greater stiffness of the bearing.

In-Place FE Modeling of Unbonded Flexible Pipelines Capturing Pressure Stiffening and Decoupled Axial/Nonlinear Bending Stiffness

2010 ◽  
Author(s):  
Edvin Hanken ◽  
Evelyn R. Hollingsworth ◽  
Lars S. Fagerland
Keyword(s):  
Water Injection ◽  
Bending Stiffness ◽  
Axial Stiffness ◽  
Fe Model ◽  
Nonlinear Bending ◽  
Upheaval Buckling ◽  
History Effects ◽  
System Integrity ◽  
Non Linear ◽  
Bending Behaviour

For fast track pipeline projects the need for costly installation vessels and sophisticated materials for rigid pipeline water injection systems, have made flexible pipelines a competitive alternative. They can be installed with less costly construction vessels, provide a competitive lead time and a corrosion resistant compliant material. Flexible pipelines have relative high axial stiffness and low non-linear bending stiffness which is a challenge to model correctly with FE for in-place analyses of pipelines. Whilst some FE programs can model the non-linear bending behaviour of a flexible pipeline at a given pressure, current FE tools do not include the effect of increased bending resistance as the system is pressurized. Therefore, a 3D FE model in ANSYS was developed to simulate the decoupled axial and nonlinear bending behaviour of a flexible, including the bend stiffening effect for increasing pressure. A description of the model is given in this paper. It will be demonstrated how the FE model can be used to simulate the 3D nonlinear catenary behaviour of an high pressure flexible pipeline tied into a manifold during pressurization. Due to high manifold hub loads during pressurization it is essential that such a model is capable of capturing all effects during pressurization to achieve an acceptable confidence level of the system integrity. It is also described how the FE model is used for upheaval buckling design, capturing non-linearities and load history effects that can reduce the conservatism in the design.

SEISMIC RESPONSE OF POWER TRANSMISSION TOWER-LINE SYSTEM UNDER MULTI-COMPONENT MULTI-SUPPORT EXCITATIONS

2012 ◽  
Vol 06 (04) ◽  
pp. 1250025 ◽  
Author(s):  
TIAN LI ◽  
LI HONGNAN ◽  
LIU GUOHUAN
Keyword(s):  
Seismic Waves ◽  
Power Transmission ◽  
Incident Angle ◽  
Ground Motions ◽  
Three Dimensional ◽  
Transmission Tower ◽  
Line System ◽  
Time Stepping ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

The effect of multi-component multi-support excitations on the response of power transmission tower-line system is analyzed in this paper, using three-dimensional finite element time-stepping analysis of a transmission tower-line system based on an actual project. Multi-component multi-support earthquake input waves are generated based on the Code for Design of Seismic of Electrical Installations. Geometric non-linearity was considered in the analysis. An extensive parametric study was conducted to investigate the behavior of the transmission tower-line system under multi-component multi-support seismic excitations. The parameters include single-component multi-support ground motions, multi-component multi-support ground motions, the correlations among the three-component of multi-component multi-support ground motions, the spatial correlation of multi-component multi-support ground motions, the incident angle of multi-component multi-support seismic waves, the ratio of the peak values of the three-component of multi-component multi-support ground motions, and site condition with apparent wave velocity of multi-component multi-support ground motions.

scholarly journals Improved Reliability of Bladed Disks due to Friction Dampers

1997 ◽  
Author(s):  
Walter Sextro ◽  
Karl Popp ◽  
Ivo Wolter
Keyword(s):  
Dry Friction ◽  
Three Dimensional ◽  
Line Contact ◽  
Two Dimensional ◽  
Centrifugal Forces ◽  
Friction Damper ◽  
Blade Vibration ◽  
Friction Dampers ◽  
Bladed Disk ◽  
Bladed Disk Assembly

Friction dampers are installed underneath the blade platforms to improve the reliability. Because of centrifugal forces the dampers are pressed onto the platforms. Due to dry friction and the relative motion between blades and dampers, energy is dissipated, which results in a reduction of blade vibration amplitudes. The geometry of the contact is in many cases like a Hertzian line contact. A three-dimensional motion of the blades results in a two-dimensional motion of one contact line of the friction dampers in the contact plane. An experiment with one friction damper between two blades is used to verify the two-dimensional contact model including microslip. By optimizing the friction dampers masses, the best damping effects are obtained. Finally, different methods are shown to calculate the envelope of a three-dimensional response of a detuned bladed disk assembly (V84.3-4th-stage turbine blade) with friction dampers.

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