DAMAGE DETECTION OF TRANSMISSION TOWER BASED ON MODEL REDUCTION UTILIZING AMBIENT VIBRATION DATA

After strong typhoon or earthquake, it is common that some secondary members of many transmission and communication towers were damaged (buckled) by the short term large deflection. When the large wind or earthquake load stop, the damaged secondary members may difficult to be identified through visual inspection. The main objective of this paper is to develop a practical structural damage detection method that is tailor-made for the detection of damaged secondary members of large-scale three-dimentional tower structures. In order to restrain the number of required sensors to a reasonable and affordable value, the proposed method makes use of the substrcutrue concept. Under the proposed sub-structure scheme, only one sensor is required for one substructure. For the 3-dimensional tower example (consists of 324 DOFs) in the case study, only 12 sensors are required for detecting the loss of stiffness in each sub-structure. The proposed method consists of two phases, the modal parameters are first extracted from the ambient vibration responses by the natural excitation technique (NExT) in conjunction with the eigen-system realization algorithm (ERA) in the first phase. In the second phase, the damage locations and the corresponding extents for the secondary members in each sub-structure are then estimated utilizing the identified modes. The proposed method is demonstrated through a series of comprehensive case studies with the consideration of measurement noise. The effect of including different modes in the damage detection result is also studied. As expected, some modes can provide more information for detection damage at certain locations. The case study results are very encouraging showing that it is worth to do further research along this direction.