Incremental dynamic analysis (IDA) applied to seismic risk assessment of bridges - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 557

3.0

84% IM ⎪ DM (16% DM ⎪ IM)

2.5

2.0

50% IM ⎪ DM (50% DM ⎪ IM)

1.5

1.0

0.5

16% IM ⎪ DM (84% DM ⎪ IM)

0 0

0.02 0.04

Maximum column drift

0.06 0.08 0.1

21.1 An example of IDA curves developed using 44 crustal records for
a 4-span bridge (fractle 16%, 50% and 84% IDA curves are shown by
heavy lines) (Tehrani et al ., 2012).

K S M c

M y

q pc

K e

K c

q y q cap

q ) Chord rotation (

21.2 Backbone curve parameters (adapted from ATC-63, 2008).

θ pc (Ibarra et al. , 2005). These parameters are used to defi ne a component
backbone curve, as shown in Fig. 21.2.
The distinction between cyclic and in-cycle degradation is important issue
that should be considered in modelling (ATC-62, 2008). Dynamic response
of systems with cyclic strength degradation is generally stable, while in-cycle
strength degradation can lead to lateral dynamic instability (i.e., collapse).
In reinforced concrete components, material nonlinearities that can lead to
in-cycle strength degradation include concrete crushing, shear failure, buck-
ling or fracture of longitudinal reinforcement, and splice failures (ATC-62,