Most substations built in China were concrete structures which have been in use for over 20 years. It indicates the inevitable structural damage. Two non-destructive testing methods based on frequency were introduced. The results show that the regularization frequency rate method can identify the single damage of frame beams. The monotonicity of the low-order regularization frequency rate curve and its combination curve are better, and the damage identification more accurate. Multi-fractures identification method can identify single damage a...
