Damage Identification of a Derrick Steel Structure Based on the HHT Marginal Spectrum Amplitude Curvature Difference

Table 1

Damage condition of the derrick steel structure.

Condition	Damage degree	Damage type	Damage position
1	5%	Single damage	16
2	20%		10
3	30%		5
4	5%	Double damage	8, 14
5	10%		5, 13
6	5%, 10%		5, 13