ABSTRACT
The virtual displacement vector x1 under the first load system f1 can be obtained using the truncated flexibility matrix constructed by identified modal parameters.
Based on the theory above, the two main sources of error when estimating rigidity reduction using PLFM are: (1) the truncation error of flexibility matrix due to limited number of modes, denoted as ERH ; and (2) the neglect of virtual strain energy within q in Equation (3), denoted as ERE . Note that for the LFM only
ERH exists, while for the PLFM both ERH and ERE exist. The key point of the PLFM is that if the nonlocal first load system f1 can reduce ERH for a large amount and at the same time induce ERE which is much smaller than ERH , the chosen of the non-local first load system should benefit the damage detection results.
