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

3. SEISMIC BEHAVIOUR OF BOLTED END PLATE BEAM-TO-COLUMN STEEL JOINTS
The end plate represents an important component for the joints considered. The
end plate responses of the isolated Tee stub TC-2 and Complete Joint JA1-2A are
plotted in Figure 3.23. As mentioned above, the testing procedure imposes
different cycle amplitudes and affects the number of cycles at failure. However, the
collapse mode is the same, i.e., by plate fracturing, and the evolution of the
hysteretic behaviour has similar features. A comparison between the maximum
force and displacement shows an overestimate of the first parameter of 7% and an
underestimate of the second of 13% with reference to the Tee stub response. The
influence of the interaction between the different components in the joint appears
to be limited. The same comparison between the joint JB1-3 and the corresponding
Tee stubs TC-3 shows similar results, as evidenced in Figure 3.24.
70
REACTION FORCE (kN)
400
300
200
100
0
-100
-200
-300
-400
TC-2
JA1-2A (ENDPLATE)
0 2 4 6 8 10
DISPLACEMENT (mm)
Figure 3.23. Comparison of the experimental
response of the Tee stub TC-2 and the End plate of
the Complete Joint JA1-2A
A more accurate appraisal of the responses of the elemental components can be
obtained if reference is made to key parameters, such as the initial elastic stiffness
and the plastic failure strength, which characterize the envelope of the cyclic
response. A conventional elastic stiffness Ke, a plastic failure strength Fp and an
ultimate displacement ductility factor eu/ey were determined by the bi- and tri-linear
approximations of the envelope curve, traced on the basis of best-fitting and
dissipated energy-equivalence criteria. Values of the elastic stiffness Ke relevant to
the components of joints JA1-2 and JB1-3 and to the corresponding isolated and
coupled Tee stubs are presented in Table 3.6.