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

4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS
total rotations of CJ-INT reach values greater than 50 mrad both under sagging
and hogging bending moment, implying a suitable ductile behaviour for high ductile
(class H) structures in seismic applications (Eurocode 8, 2002).
CONCRETE STRESS (MPa)
50
45
40
35
30
25
20
15
10
Exterior Complete Joint CJ-EXT
5
0
Loss of resistance
0 25 50 75 100 125 150
ROTATION θ (mrad)
Figure 4.25. Concrete stress vs. global rotation in CJ-INT
Both the monotonic and the cyclic test were performed. In the monotonic test an
imposed displacement load that would produce compression in the concrete slab
was selected. The moment vs. plastic rotation of a beam-column assembly, the
moment vs. plastic rotation of the composite beam connection, and the shear vs.
plastic distortion of the column web panel are shown in the following Figures. The
joint behaviour, and in particular the contribution of the concrete slab in
compression, is very similar to that obtained for the interior joint CJ-INT. Also in this
case, as shown in Figure 4.26, the crushing of the concrete in compression around
the column flange brings about the loss of resistance in the global joint response.
The same phenomenon is evident in the behaviour of the connection (see Figure
4.27) and in the response of the column web panel (see Figure 4.28), that
distortion alone represents more than the 64% of the total joint rotation.
The behaviour of the exterior joint during the cyclic test resulted different from that
of the interior joint. Under hogging bending moment, the exterior portion of the
concrete slab in compression was able to absorb large plastic deformations with
formation of evident cracks at an inclination of 45 degree, as shown in Figure 4.29.
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