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

5. SEISMIC BEHAVIOUR OF RC COLUMNS EMBEDDING STEEL PROFILES
the test because only a cyclic test is executed, that is a test with increase of
displacement. The principle is that a reference yield displacement ey value in the
form of an absolute value should be defined preliminarily and kept for all
specimens, in order to make possible a direct comparison. For composite columns,
the estimated interstorey drift angle θy at yielding is 0,5% = 5 mrad. The drift angle
in the test is the displacement of the actuator divided by the height or length of the
part of the specimen, which may deform during the test. The height of column
which is free to deform is 3500 mm (storey height), i.e. from the actuator axis to the
hinge axis, then, ey = θy x 3500 = 17,50 mm is the yield displacement (+ and -) at
the actuator (+ and -). The loading history is defined by the following sequences,
reported hereafter in Figure 5.27:
• one cycle in the intervals:
e y
+ /4, ey − /4; 2 e y
+ /4, ey − /4; 3 e y
+ /4, 3 ey − /4; e y
+ , y
• three cycles in the intervals:
2 e y
+ , 2 ey − ; 4 e y
+ , 4 ey − ; … ; (2+2n) e y
+ , (2+2n) y
• more cycles or more intervals may be used if necessary.
y
24
20
16
12
8
4
0
-4
-8
-12
-16
-20
-24
a)
e − ;
Figure 5.27. Multiple-Step Test: adopted ECCS loading history
e − with n = 1, 2, 3,…
Due to the set-up configuration used by the laboratory of the University of Trento,
some calculations have been conducted in order to obtain the correct displacement
and force loading history to be applied to the horizontal and the vertical actuators,
respectively. During the test, because of the deformed configuration of the
specimen, the steel distributing frame modifies the inclination with respect to the
horizontal line in the un-deformed configuration. This means that, both the
horizontal and the vertical actuators modify their original inclination, producing a
e/e y +
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