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

5. SEISMIC BEHAVIOUR OF RC COLUMNS EMBEDDING STEEL PROFILES
In order to understand the behaviour of the joint under cyclic loading, it is important
to evidence the rotation capacity that the panel zone can carry out. As explained
before, the distortion of the panel zone was monitored during the test by means of
the LVDT TR500-2D e TR500-1D. The transducer measurements are combined by
the following formula (Krawinkler, 1978) to obtain the total distortion.
226
γ
( )
( U U )
−1 2
2 ∆ TR500−2 D − ∆ TR500−1D conn = tg ( hsp ) + bsp
2
( hsp + bsp
)
( 5.73 )
where hsp e bsp are the design height and depth of the web panel in shear; ∆UTR500
are the difference between the two measurement of the diagonal LVDT transducer.
As depicted in Figure 5.35, it is possible to underline that the behaviour of the
panel zone is characterized by large energy absorption and displacement ductility,
due to the extensive plastic deformation occurring. One can observe that total
distortions of the joint reach values greater than 35 mrad, implying a suitable
ductile behaviour for high ductile structures in seismic applications. Progressive
strength and stiffness deterioration is then occurring associated to the increase of
plastic deformations of the steel profile and damage in the concrete.
JOINT SHEAR (kN)
1250
1000
750
500
250
0
-250
-500
-750
-1000
-1250
-75 -60 -45 -30 -15 0 15 30 45 60 75
DISTORTION γ (mrad)
Figure 5.35. Joint shear force vs. distortion relationship for COT10
specimen