The Wind Vibration Analysis Of Suspension Cable Guyed Tower

Suspension cable guyed tower is a tall, high soft, large-span structure. It is a kindof wind sensitive structure. And in the design of anchor tower structure, wind loadusually tend to be the control load. Because of its large flexibility, anchor tower, underpulsating wind load, will generate a large geometric deformation. Therefore, guyedtower structure possesses geometric nonlinearity. The tower and lines of the anchortower structure have mutual coupling effects. Transmission lines will affect the stiffnessand internal force of the main column of the tower. Thus the wind vibration responsesof the tower are also nonlinear. UHV transmission lines and ultra-high voltagetransmission lines are different in many ways. And thus, for the UHV transmissiontower, these differences make the head size and height of the tower increased, theweight and the loads of tower are also increase accordingly. Considering the factorsmentioned above, this article has carried on the dynamic time history response analysisof the UHV anchor tower structure subjected to fluctuating wind load.Transmission tower structure is generally divided into two major categories:free-standing transmission tower and anchor tower. Suspension cable guyed towerstructure is a form of anchor tower structure. Though free-standing tower has largerdead load, bigger quantity and higher cost, it is more widely adaptable, and can beapplied to a variety of terrain. On the contrary, anchor tower, though has lighter weight,smaller volume, lower cost, its use is limited by certain terrain conditions. Learned fromprevious engineering experience, compared with free-standing tower, the guyed towerhas20%~50%less dead load. So, guyed tower can apparently cut the cost. Then, in theregion with low relief, use the anchor tower structure is more appropriate.The wind vibration analysis in this paper is based on±800kV UHV dc linesthrough the gobi desert region in xinjiang, the main contents and results are as follows:(1) Analysis of the structure’s static characteristics. Establish the detailed finiteelement model of the suspension cable anchor tower structure, and use the finiteelement analysis software ANSYS to analyze the static characteristics of the structure.By analyzing the maximum design stress of the steel cable, the paper identified the staywire’s biggest initial tension. Considering the non-linear deformation, the relationcurves of the internal force of the bracing wire, suspension cable and the main pillarunder the action of gravity without wind load are given. The influence of different initial tension on the internal forces of the structure is analyzed. The results show that underdifferent initial tension of the suspension cable and gravity, the internal force increaseswith the increase of initial tension in a linear relationship.(2) Analysis of the structure’s dynamic characteristics. The formfinding of the cableelement is conducted. And the coordinates positioning of the guide wire and groundwire under the dead weight and wind load is carried. Then the dynamic characteristicsof the structure are analysed. Analysis showed that the first order frequency of thecolumn is to twist around itself. Pillar torsional frequency is almost unanimous with thetower-line system. For the effects of the guide wire and ground wire, in the tower-linesystem, the pillar’s side bend frequency is lower than in single tower. Cable tension willsignificantly increase the torsional rigidity of the post. With the tension increasing, thetorsional frequency increases in a nonlinear way. When the initial tension of thesuspension cable is small, its influence on the modal of the columns is small. When theinitial tension of the suspension cable is rather large, the frequency of the pillardecreases as it increasing.(3) Analysis of wind load time history. Aeroelasticity time history analysis of theguide line is processed. The results show that the wind vibration coefficients are smallerconsidering the pneumatic elasticity than not. At first, simplified beam with springmodel, simplified column tower model and real column tower model is establishedrespectively for the study of the wind vibration response characteristics of the tower.Then both the simplified column tower line model and real column tower line model arefounded to research the response characteristics. The paper discussed the changing trendof the wind vibration coefficient changing with the guide wire and ground wire tension.It shows that the column average displacement decreases as the tension of the guide andground wire increase. But both the dynamic values and the wind vibration coefficientincreased slightly. The paper also discussed the changing trend of the wind vibrationcoefficient according to the changing of the bracing wire tension. It is found that thecolumn average displacement decreases with the increase of the stay wire tension. Andboth the dynamic response and the overall dynamic magnification coefficient increase.(4) Research on wire fracture. In the paper, it is built the finite element analysismodel with the wire fracture, and it is realized the break condition simulation andanalysis. Structure analysis shows that: with the increase of the number of fracture line,column displacement increases sharply in obvious nonlinear relation, and the guide wiretension, the ground wire tension and the column internal force also increased obviously; Anchor fracture may lead to the ground wire breaking. But because the amplificationfactor of the wire is not very big, the tower line system is expected to remain stablestructure.