Health Monitoring based on Dynamic Flexibility matrix: Theoretical Models versus in-situ Tests

The paper focuses on damage detection of civil engineering structures and
especially on concrete bridges. A method for structural health monitoring
based on vibrational measurements is presented and discussed. Experimentally
identified modal parameters (eigenfrequencies, mode shapes and modal
masses) of bridge structures are used to calculate the inverse stiffness matrix,
the so-called flexibility matrix. By monitoring of the stiffness matrix, damage
can easily be detected, quantified and localized by tracking changes of its individual
elements. However, based on dynamic field measurements, the acquisition
of the flexibility matrix instead of the stiffness matrix is often the only
choice and hence more relevant for practice. But the flexibility-based quantification
and localisation of damage are often possible but more difficult, as it
depends on the type of support and the location of the damage. These issues
are discussed and synthetized, that is an originality of this paper and is believed
useful for engineers in the damage detection of different bridge structures.
First the theoretical background is briefly repeated prior to the illustration
of the differences between stiffness and flexibility matrix on analytical
and numerical examples. Then the flexibility-based detection is demonstrated
on two true bridges with real-time measurement data and the results are
promising.