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

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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 + 217
5. SEISMIC BEHAVIOUR OF RC COLUMNS EMBEDDING STEEL PROFILES modification in the actual applied horizontal displacement and vertical axial force. Considering the geometry of the specimen and of the test set-up we obtain that: • the imposed displacement of the horizontal actuator is greater than the 218 horizontal displacement at the top face of the specimen, due to the angle formed by the top steel distributing beam in the deformed shape of the specimen. Obviously, this inclination depends on the specimen flexibility that varies during the test due to damage in some portions of the specimen. A priori, it is impossible to know correctly this aspect, even if we reconstructed the displacement loading history by means of an elastic numerical model. We have obtained that the ratio between the top displacement of the column and the displacement of the horizontal actuator is given by a factor equal to 1.214; • moreover, the axial load imposed by the vertical actuator (assumed equal to 900 KN) must be maintained constant during the test. The top displacement of the column δx, imposed by the horizontal actuator, modifies the alignment between the specimen and the vertical actuator (see the deformed configuration in Figure 5.28). For this reason, only a component of the imposed axial load is applied to the column. α δ Figure 5.28. Deformed configuration of the specimen and of the test set-up during the test Thus, a geometrical relation to maintain constant the axial load, as a function of the top displacement of the column, was deduced δ θ δ γ
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Dipartimento di Ingegneria Meccanic
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UNIVERSITÀ DEGLI STUDI DI TRENTO D
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Ai miei genitori
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INDEX 1 INTRODUCTION...............
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INDEX iii 4.10.3 Results of the PsD
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1.1 Introduction 1 1 INTRODUCTION I
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1. INTRODUCTION imposes precise con
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1. INTRODUCTION joints whilst 2D mo
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7 2 DUCTILITY AND SEISMIC RESPONSE
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2. DUCTILITY AND SEISMIC RESPONSE O
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Analysis and modelling of the seismic behaviour of high ... - Ingegneria

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