Analysis and modelling of the seismic behaviour of high ... - Ingegneria
Analysis and modelling of the seismic behaviour of high ... - Ingegneria
Analysis and modelling of the seismic behaviour of high ... - Ingegneria
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5. SEISMIC BEHAVIOUR OF RC COLUMNS EMBEDDING STEEL PROFILES<br />
<strong>the</strong> test because only a cyclic test is executed, that is a test with increase <strong>of</strong><br />
displacement. The principle is that a reference yield displacement ey value in <strong>the</strong><br />
form <strong>of</strong> an absolute value should be defined preliminarily <strong>and</strong> kept for all<br />
specimens, in order to make possible a direct comparison. For composite columns,<br />
<strong>the</strong> estimated interstorey drift angle θy at yielding is 0,5% = 5 mrad. The drift angle<br />
in <strong>the</strong> test is <strong>the</strong> displacement <strong>of</strong> <strong>the</strong> actuator divided by <strong>the</strong> height or length <strong>of</strong> <strong>the</strong><br />
part <strong>of</strong> <strong>the</strong> specimen, which may deform during <strong>the</strong> test. The height <strong>of</strong> column<br />
which is free to deform is 3500 mm (storey height), i.e. from <strong>the</strong> actuator axis to <strong>the</strong><br />
hinge axis, <strong>the</strong>n, ey = θy x 3500 = 17,50 mm is <strong>the</strong> yield displacement (+ <strong>and</strong> -) at<br />
<strong>the</strong> actuator (+ <strong>and</strong> -). The loading history is defined by <strong>the</strong> following sequences,<br />
reported hereafter in Figure 5.27:<br />
• one cycle in <strong>the</strong> intervals:<br />
e y<br />
+ /4, ey − /4; 2 e y<br />
+ /4, ey − /4; 3 e y<br />
+ /4, 3 ey − /4; e y<br />
+ , y<br />
• three cycles in <strong>the</strong> intervals:<br />
2 e y<br />
+ , 2 ey − ; 4 e y<br />
+ , 4 ey − ; … ; (2+2n) e y<br />
+ , (2+2n) y<br />
• more cycles or more intervals may be used if necessary.<br />
y<br />
24<br />
20<br />
16<br />
12<br />
8<br />
4<br />
0<br />
-4<br />
-8<br />
-12<br />
-16<br />
-20<br />
-24<br />
a)<br />
e − ;<br />
Figure 5.27. Multiple-Step Test: adopted ECCS loading history<br />
e − with n = 1, 2, 3,…<br />
Due to <strong>the</strong> set-up configuration used by <strong>the</strong> laboratory <strong>of</strong> <strong>the</strong> University <strong>of</strong> Trento,<br />
some calculations have been conducted in order to obtain <strong>the</strong> correct displacement<br />
<strong>and</strong> force loading history to be applied to <strong>the</strong> horizontal <strong>and</strong> <strong>the</strong> vertical actuators,<br />
respectively. During <strong>the</strong> test, because <strong>of</strong> <strong>the</strong> deformed configuration <strong>of</strong> <strong>the</strong><br />
specimen, <strong>the</strong> steel distributing frame modifies <strong>the</strong> inclination with respect to <strong>the</strong><br />
horizontal line in <strong>the</strong> un-deformed configuration. This means that, both <strong>the</strong><br />
horizontal <strong>and</strong> <strong>the</strong> vertical actuators modify <strong>the</strong>ir original inclination, producing a<br />
e/e y +<br />
217