Performance Based Fragility Analysis Of Transmission Tower-line System Subjected To Wind

With the development of economy in China, the demand for energy is growing faster and faster, but the distribution of energy in our country is unbalance, in order to overcome the contradiction between supply and demand, a series of transmission lines are planning and constructing. As an important part of lifeline engineering, once the transmission lines are destroyed, it will cause the failure of power supply system and a series of secondary disasters, of which the consequences are extremely serious, so its ability to resist natural disasters should be strengthened. As is shown by theoretical analysis and investigation after disaster, the wind disaster is the main factor causing the circuits' failure, how to ensure that the circuits have good performance in strong wind has become a hot research at present. Based on this, the paper rests on the performance design and selects a transmission towerline coupled system as research object, then the vulnerability analysis of the structure under wind disaster has been carried on. The research works are mainly as follows:1. Using the harmonic synthesis method to simulate the fluctuating wind. The characteristics of average wind and fluctuating wind are described. In order to simulate the fluctuating wind, a MATLAB program is written based on the Kaimal wind speed spectrum, of which the influence of spatial correlation is considered. A transmission line is taken as an example and the time-histories of the nodes are simulated, after which the simulated spectrum and the target spectrum are compared, the result shows that the simulation of fluctuating wind is correct.2. Considering the randomness of the materials, a three tower-four span model is built using the finite element software ANSYS, and then the time-history analysis of the towerline system is conducted, as a result, the time-history curve of the tower's top displacement is obtained. The effect of wind direction on the structure is discussed, which shows that the displacement reaches the maximum under the degree of ninety. With the Latin hypercube sampling method, ten samples are taken, for each sample, the tower's top displacements under different wind speed are obtained using finite element method.3. The performance levels of the transmission tower under wind load are obtained under analysis and their values are quantized. The performance levels corresponding to three failure modes of transmission tower are summed up, and then uses the Pushover analysis to get the capacity curve of transmission tower, combining with the experimental results, the limit values corresponding to different performance levels are found in the curve.4. The wind disaster vulnerability function is raised, and the regression analysis of the discrete points calculated by ten samples is carried on, and then the corresponding average value and standard deviation are obtained, at last the vulnerability curves are drawn.