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

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5. SEISMIC BEHAVIOUR OF RC COLUMNS EMBEDDING STEEL PROFILES and shear resistance of the steel sections reduces of a half factor, while the second one guarantees the resistance in bending to be half of that belonging to the original section. Nevertheless, by diminishing the geometrical properties of the concrete sections we obtained a reduction of the bending resistance equal to one fourth of the original section. Hence, the assumptions made for the reduction of the steel profile properties were not adoptable. Indeed, it was necessary to calculate the reduced steel sections following the design criteria already presented in a previous paragraph for the full-scale steel-concrete composite columns, and briefly summarised below: a. the steel section should at least be able to take alone the design axial force of the seismic loading case; b. the steel section alone (not acting composedly) should be able to substitute the deficient concrete section; c. the sections have been chosen in order to not modify the local stiffness EI of the columns and the total stiffness of the original concrete structure (maximum level of modification of the order of 10%); d. the sections have been chosen in order to achieve a favourable performance both along their major axis bending and along their minor axis bending. In the following Figure 5.19 the reduced composite column cross sections adopted in the experiments at the University of Trento are shown. Figure 5.19. Reduced sections for the composite columns to be tested From these sections, corresponding to the respective load cases under study, we extrapolated the scaled 3D composite columns to be analysed. Each cross composite section generated four scaled samples, two with long steel profile (with or without steel plates in the joint), and two with short steel profile in the critical length (with or without horizontal steel plates) as illustrated in Figure 5.20. Therefore, to each design category (static and seismic) belong four composite samples plus another scaled sample without the encased steel profile. The latter operating as a comparison trial for the others. Also four tests along minor axis were 209
5. SEISMIC BEHAVIOUR OF RC COLUMNS EMBEDDING STEEL PROFILES planned. One reinforced concrete (RC) column and one composite (CO) column both for the Static case and for the Seismic A case had to be analysed. The stiffeners were considered with the aim of better understanding the behaviour of the joint panel, i.e. the continuity horizontal plates were welded to the steel profile at the height of the critical joint region to state whether their presence may modify or not the load transfer between concrete and steel. In order to ensure that the load transfer between concrete and steel are efficiently mobilized in critical region of the composite column, an end plate welded at the end of the steel profile was designed. The alternative and possible use of shear connectors welded on the steel flanges in the critical zone was rejected, both to allow for a simplified technical solution and to minimise the fabrication costs of the samples under evaluation. The geometrical specifications for the design of the end plate are highlighted in Figure 5.20. 210 ≤ ≤ ≤ Figure 5.20. Geometrical characteristic of the end plate and stiffeners It is to mention that the side beams were over-designed in respect of the column (not responding to the Capacity Design principle) specifically to allow the study of the joint and column behaviour. On the contrary, another research carried out at the University of Liège, in the presence of a frame, which did not permit the full frame deformation (due to the presence of a bracing system simulating the masonry in-fills), saw the plastic deformation occurring in the column without the ≤
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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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3. SEISMIC BEHAVIOUR OF BOLTED END
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Analysis and modelling of the seismic behaviour of high ... - Ingegneria

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