Models for Simulating the Seismic Response of Concrete Structures - Dynamic Behavior of Concrete and Seismic Engineering - page 257

2D
flexible
support
with
interface

2D flexible
support
without
interface

3D
embedde
d

1D
embedde
d

1D
flexible
support

Model
type

Test

1st
bending
mode

10 Hz 10.3 Hz 8.5 Hz 7.3 Hz 7.4 Hz 7.3 Hz

1st
pumping
mode

45 Hz 40 Hz 28.3 Hz 22.3 Hz 19 Hz 20 Hz

Table 7.3. Main natural modes, test-calculation comparisons

7.4.2.1.1. Interest of simplified modeling for para-seismic studies

Importance of linking conditions at the support-structure interface

This analysis was conducted mainly on the CAMUS I model. For this analysis,
the determination of natural modes was the subject of comparative analyses of
calculations between the multi-layer model and a refined 3D model based on
embedding conditions on a rigid foundation. The results show an excellent
correlation between both calculations led to elasticity. Preliminary tests revealed that
the two main modes were the first bending mode (in the plane of the walls) and the
first vertical pumping mode, which was particularly visible, due to the flexibility of
the table, a versatility not taken into account for the first calculations (Table 7.3). An
accurate description, including the model, table, anchoring bars and the model-table
interface mortar as an option was performed within a 2D EF model. For the two
main modes, the results show the importance of the interface being softer than the
remaining foundation), the taking into account of which allows the experimental
results. As far as the “multi-layer” calculations are concerned, the flexibility of the
table was adjusted to take the effects of the interface mortar into account. As we can
see, the results compared with the experiment prove quite convincing.