Analysis and modelling of the seismic behaviour of high ... - Ingegneria

4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS
where Fb and dn are, respectively, the base shear force and the control node
displacement of the MDoF system.
ii. Definition of the yield force F *
y, which also represents the ultimate strength of
the idealized system; it is equal to the base shear force at the formation of the
plastic mechanism. The initial stiffness of the idealized system is determined in
such a way that the areas under the actual and the idealized force–deformation
curves are equal (see Figure 4.47).
Figure 4.47. Determination of the idealized elasto-perfectly
plastic force-displacement relationship (EC8, 2002)
Based on this assumption, the yield displacement of the idealized SDoF
system d *
y is given by:
*
y
*
* Em
= 2 d m − *
F
d ( 4.32 )
y
where E *
m is the actual deformation energy up to the formation of the plastic
mechanism.
iii. Determination of the period T * of the idealized equivalent SDOF system,
determined by:
*
T 2π
m d
* *
y
*
y
= ( 4.33 )
F
153