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

Table 2

Damage experimental conditions of the derrick steel structure.

Condition	Damage form	Damage type	Damage position
1	Pin loose	Single damage	The place between second segment and third segment
2		Single damage	The place between third segment and forth segment
3		Double damage	Integrating the first two kinds of damage location