Health Assessment of Engineering Structures Using Graphical Models - Structural Seismic Design Optimization and Earthquake Engineering - page 359

Table 3. Damage signatures for the SDOF building up to the first non zero direction of change

Damage type Damage in structural components Sensor faults

k - D - k + D + B - B + dr - dr +

Damage signature ( x ) 00+ 00+ 00- 00- - + 0- 0+

measurements (0th order changes) provide ad-
ditional discriminatory power. Higher order effects
eventually manifest as first order effects, and since
we can only measure magnitude and slope reliably,
only the first change (and whether it was discon-
tinuous) is useful. If we measure displacement,
the damage signatures represent a qualitative
measure that reflects how a displacement observa-
tion could be affected by a change in one of the
structure parameters. It is observed from Table 4
that the damage in the stiffness parameter of k1,
k2 and k3 have different signatures on the mea-
surements x 1 , x 2 and x 3 . On the other hand, the

signature of damage in k 1 is the same as the sig-
nature of damage in D 1 (same observation is
valid for k2 and D2). Considering that the MDOF
system models a multi-story building, this obser-
vation is consistent since the reduction in either
the stiffness or the damping coefficient implies
damage to the columns of the same floor. When
multiple causes are identified in the qualitative
step, then all those causes are included in the
quantification step which helps to discriminate
between them.

Figure 7. Damage signature extraction