| At present,most of the towers used in China’s HVDC transmission lines are vertical towers,which are relatively heavy and will result in large project investment.However,double-column suspension towers have been widely used in transmission lines by many foreign countries.The advantage of this type of towers is that its weight is 30% to 50% lighter than that of vertical towers.But this kind of towers occupy a larger area than the vertical towers.With the development of power transmission projects from West to East in China,many lines will pass through desert Gobi and other areas,and the economic advantages of double-column suspension towers are obvious.Double-column suspension cable tower is mainly composed of two parts: the cable suspension system and two lattice columns.However,there are few studies on wind-induced response of double-column cable-stayed tower in China.The only research is limited to the reasonable value of tension of the cable,and the research and analysis of the response of the columns under fluctuating wind are the key to the analysis of wind effect of the cable-stayed tower.Based on the wind tunnel tests,The following aspects of the research work were carried out on the suspension tower column:(1)With the test site simulated as a class B geomorphological site,the wind tunnel tests were carried out on the aerodynamic elastic model of the double-column cable tower.Under the action of the pulsating winds at the angle of 90° and 0°,to analyzed the response of Double column suspension tower,explored the wind induced responses of including displacement,acceleration and base reaction force.and the wind-induced coefficients are analyzed.(2)Established the finite element model of tower line system of Double column suspension tower and simulated it with the time course of pulsating wind speed.Found the wind-induced vibration response of the model under the pulsating wind and the structural response with the change of the pre-tension of the cables.Used analysis results compared with the test results to verify the correctness of the modeling.(3)In order to facilitate the frequency domain analysis and calculation of the cable tower,the model simplification idea of the double-column suspension cable tower was proposed.The finite element models were simplified into the double-column column system model,the double-column non-conductor model and the single-column non-conductor model.The correctness of the simplified models were verified by modal analysis and time history analysis.The results show that the four models are in good agreement with the experimental results.(4)Based on the simplified single column model proposed and verified,a frequency domain analysis method of wind vibration coefficient is proposed.According to the dynamic equation of beam in structural dynamics,the vibration mode and frequency equation of double-column cable-stayed tower column are derived.At the same time,based on the frequency domain method,the fluctuating response of the column and the influence of different tension on the lateral bending response of the column are calculated,and the results are compared with the time domain analysis results.(5)The formulas of dimensionless mode shapes of columns with different end spring stiffness are obtained by parameter fitting.The formulas of wind-induced vibration coefficients for double-column cable-stayed towers are derived based on inertial force method and Building Structure Load Code(GB500009-2012)(hereinafter referred to as "Code 2012"),and the tables of relevant parameters are given for reference of wind-resistant design of cable-stayed towers.(6)Based on the static equivalent wind load method proposed by Holmes,the trend of three load components along the height of the tower is analyzed.The wind-induced vibration coefficients of cable-stayed towers are solved by this method.The wind-induced vibration coefficients are substituted into the finite element model for time-history analysis and response checking.The results indicates that the method proposed in this paper can accurately evaluate the wind effect of double-column suspension pylons and can be applied to the structural design of double-column suspension pylons. |
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