Dynamic/earthquake analysis - Computational Analysis and Design of Bridge Structures - page 521

Four procedures can
be used in analysis
and rehabilitation
of structures

Modeling (material and geometric)

Linear Nonlinear

Linear
Static

Nonlinear
Static

Linear
Dynamic

Nonlinear
Dynamic

Figure 17.7 Four distinct analytical procedures for seismic analysis.

Table 17.1 Bridge seismic analysis types recommended by Caltrans

Nonlinear static Dynamic

Time-history
analysis—direct
integration
Linear

Equivalent
static
analysis

Incremental
static analysis
(Pushover)

Response
spectrum
analysis—linear Bridge classification Nonlinear

Ordinary standard A R A A A

Ordinary nonstandard N R A A R

Important N R A A R

A: Acceptable analysis type
N: Not acceptable analysis type
R: Acceptable and strongly recommended analysis type, not necessarily comprehensive

A large number of bridges were designed and constructed at a time
when bridge codes had no seismic design provisions or when these pro-
visions were insufficient according to current standards. Many of these
bridges may suffer severe damage when struck by earthquakes, as evi-
denced by recent moderate earthquakes. Linear elastic procedures are
sufficient as long as the structure behaves within elastic limits. If the
structure responds beyond the elastic limits, linear analyses may indi-
cate the location of first yielding but cannot predict failure mechanisms
and account for redistribution of forces during progressive yielding. This
fact makes the elastic procedures insufficient to perform assessments and
retrofitting evaluations for those bridges in particular and structures in
general. Nonlinear (static and dynamic) procedures are the solutions
that can overcome this problem and show the performance level of the