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

4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS
tension). For the calculation of resistance, the actual values of the yield strength as
well as the elasticity modulus of the material are used.
The rotational stiffness of the spring is determined from the flexibilities of its basic
components, each represented by its stiffness coefficient kj obtained in according
with the Eurocode 3. Moreover, for ductile components an elastic-plastic stiffness
coefficient is used; conversely, for the other components only an elastic stiffness
coefficient is used. In Figure 4.32 the characteristics for the two single-sided and
double-sided beam-to-column joint configurations respectively are shown.
Moreover, the moment-rotation relationship for both the two joint configurations are
shown in Figure 4.33: the calculated rotation capacity limits are in evidence in this
figure. These vertical limits in the rotation of the complete joints are due to both the
rotation capacity of the equivalent T-Stub that model the end-plate in bending (±15
mrad), and the rotation capacity of the column web panel in shear (±35 mrad), as
illustrated in Section 3.5.3.
COMPLETE JOINT MOMENT (kNm)
400
300
200
100
0
-100
-200
-300
-100 -75 -50 -25 0 25 50 75 100
ROTATION θ (mrad)
COMPLETE JOINT MOMENT (kNm)
400
300
200
100
0
-100
-200
-300
-100 -75 -50 -25 0 25 50 75 100
ROTATION θ (mrad)
(a) (b)
Figure 4.33. Moment-rotation relationship for the two joint configurations: (a) CJ-INT Joint;
(b) CJ-EXT joint
The analytical models are then compared with the experimental results. The
attention is hence focused on the use of these data for checking the general
validity of the joint model by component with reference to the approximation of the
monotonic and cyclic response.
With regard to the specimen CJ-INT the overall M-θ relationship is compared in
Figure 4.34. Under sagging bending moment the analytical model tends to
overestimate the experimental response and is not able to capture the loss of
resistance due to the crushing of the concrete slab in compression around the
column flange. Similar results are obtained under hogging bending moment, due to
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