Models for Simulating the Seismic Response of Concrete Structures - Dynamic Behavior of Concrete and Seismic Engineering - page 259

NOTE.- Some structural damping has been taken into account using Rayleigh's
conventional description, both coefficients of which have been adjusted at 1% on the
first mode and 2% on the second - advances have recently been made on the subject
[RAG 99]. Finally, precautions have been taken as regards the finite element mesh
to ensure objective results on a global scale, at least. Figure 7.17 compares the top
displacement results obtained experimentally as well as by calculation for the whole
loading sequence. Other results concerning load distribution throughout the
damaged or plasticized areas have been obtained [MAZ 98]. All results are of good
quality, which tends to lend credibility to such simplified methods.
Emphasizing the interaction between local behavior and overall function
The dialog between experiment and modeling groups has revealed the
importance of interaction on local and global developments. During the test at the
bottom of the wall we have been able to measure a dynamic variation of the vertical
load with a frequency twice that of the bending moment and raising intensity.
Analysis led to an appreciation of the link between the two phenomena: progressive
cracking of the structure with cracks “breathing” (opening-closing) during loading,
and the activation of the vertical pumping mode due to the flexibility of the table
and the evolution of damage. Within this context, the damage model presented in
section 7.4.2, which takes both effects into account, has revealed a direct connection
between the closing-up stress (V f ) and the intensity variation of the vertical load. A
parametric study was conducted and Figure 7.18 shows this mutual influence for
two particular values of V f , 3 MPa and 1.35 MPa, with the latter value leading to a
connection with the vertical load variations measured.