The study on modal analysis theory and measurement method for transmission towers

The modal experiment analysis of large structure is effective method of structure health evaluation in new century. Nowadays, the modal experiment data of transmitter tower is few, and moreover the modal experiment of whole transmission tower is nearly blank. This paper study and provide the modal experiment method of whole transmission tower which be stationary reference point and mobile measure point based on environmental exciting. And to apply this method to measure the preceding six orders natural frequency and modes shapes of the whole 500 kV transmission tower. Furthermore, by modal experiment and finite element analysis, the modal of diaphragm of this tower prematurely appears in the low frequency region which is adverse to structure security. So, the structure of diaphragm was optimized to strengthen the stiffness and amend the local vibration of diaphragm.