This paper presents the sensitivity analysis of Hilbert-Huang transform (HHT) based
adaptive magnitude spectrum algorithm (AMSA) identified modal frequencies of
reinforced concrete frame structures in both undamaged and damaged states.
Characterized by the a posteriori property, the recently proposed AMSA provides an
alternative frequency identification approach without resorting to the a priori
information about the frequencies to be identified which is needed for other HHT
based identification techniques. Such a property makes AMSA especially appropriate
for frequency identification and damage detection for civil engineering structures, as
the a priori knowledge of the modal frequencies is usually unavailable. To study the
sensitivities of AMSA identified modal frequencies, various acceleration signals
generated by a series of reinforced concrete (RC) plane frame finite element models
with different geometric and stiffness properties representing undamaged states are
analyzed. Then the acceleration signals corresponding to progressive damage
severities simulated by degradation in stiffness properties with two different lengths
of damaged regions are investigated. The results also demonstrate the potential of
applying AMSA in structural health monitoring.