Transmission Tower Wind Vibration Coefficient Above .100 M

Large span transmission tower above 100m is a kind of structures that sensitive to wind. The wind load is one of major considerations during design process. It proposes the concept of wind vibration coefficient while calculate the wind load. Wind vibration coefficient is magnification factor that equivalent dynamic effect to static effect. The value is very important to the high-rise tower design.The value of wind vibration coefficient in specification only for the structure that width changes along the height of straight line or quality changes along the height of structure. The mutant shape at the top of high-rise tower which is not match the specification. There are two approaches to deal with the wind vibration coefficient of transmission tower which use similar structure type in specification and multiplied by the safety factor for the design. Another is analyzed by using finite element software to get the result of wind vibration coefficient. In the first method, It has document clearly shows the safety factor of single-loop transmission tower below 100 meters, but the parts above 100 meters is still in the exploratory stage. In the second method, Three dimensional simulation has a complex process and multi-node model that time consuming and inefficient.It is proposed a simplified two-dimensional analysis method in this paper, which reduce tower structure to a single vertical pole, and the quality equivalent to the concentration of particle. We establish the two-dimensional model by ANSYS finite element software, then simulate the wind speed spectrum in the MATLAB software by harmonic superposition method and Davenport spectral function. It transform speed spectrum into pressure spectrum then apply it to the model. Finally, calculate the dynamic displacement data in different height by transient dynamic analysis. In one height, wind vibration coefficient equal to dynamic displacement divided by static displacementUse transmission tower across the Han River as an example. Compare specification method, Three dimensional modeling analysis and simplified two-dimensional analysis three method to get wind vibration coefficient. The results show that simplified two- dimensional analysis and three-dimensional modeling analysis get similar data, meanwhile two- dimensional analysis meet the specification requirements. Simplified two-dimensional analysis simplified the modeling process and also get a accurate result of wind vibration coefficient. It is a reasonable method to calculate the wind vibration coefficient of transmission tower.