Strain energy damage index (SEDI)

• Accounts for the change in strain energy, when it deforms in mode shape
• Based on the decrease in modal strain energy
• Changes in flexural rigidity
• SEDI for the i^th element centered around i^th degree of freedom can be written as

(15.4)

• = Experimentally determined fractional strain energy for mode j between the end points of element i.
• Applied to isotropic beams and plates, RC beams by the wooden board in, the composite laminated beams, aluminium plate.

Modified Laplacian operator (MLO)

• Localized changes of element stiffness
• The one-dimensional Laplacian of the discrete mode shape can be introduced.

(15.5)

Gapped Smoothing Method

• Based on the idea that a mode shape for an undamaged structure is smooth
• Defined as the square of the difference between the measured data and the smoothed fitting values
• Not provide reliable information due to not very clean information occurring at the ends.

Figure 15.2: Gapped Smoothing Method (GSM).