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Civil-Comp Proceedings
ISSN 1759-3433 CCP: 83
PROCEEDINGS OF THE EIGHTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY Edited by: B.H.V. Topping, G. Montero and R. Montenegro
Paper 252
Seismic Behaviour of an Asymmetric Three-Dimensional Steel Frame with Base Isolation Devices R.C. Barros1 and M.B. César2
1Department of Civil Engineering, Faculty of Engineering (FEUP), University of Porto, Portugal
Full Bibliographic Reference for this paper
, "Seismic Behaviour of an Asymmetric Three-Dimensional Steel Frame with Base Isolation Devices", in B.H.V. Topping, G. Montero, R. Montenegro, (Editors), "Proceedings of the Eighth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 252, 2006. doi:10.4203/ccp.83.252
Keywords: seismic behaviour, base isolation devices, asymmetric 3D metallic frames, parametric studies.
Summary
A parametric study on the use of base isolation devices in frame building
structures is undertaken. Frames were analysed with regular geometry starting from
a base-frame (BF), from which association of BF in height above a certain
asymmetric plant created more complex frames. Energy dissipation occurs in base
isolation (BI) devices, whose characteristics are used in SAP 2000 in order to
develop a parametric study of the behaviour of frames under seismic actions with
reduced forces supported by the structure. Some of the results of a parametric study
are presented graphically, identifying the importance of positioning the seismic
isolation devices used in each structural configuration (Barros and César [1]).
The first approach in the analysis of structures with energy dissipation devices at the base is based on the use of a model with two degrees of freedom (DOF) (Figure 1): one DOF at the level of the base isolators; the second DOF at the floor level (Naeim and Kelly [2]). A system of base isolation devices made of natural rubber guarantees a degree of damping in the order of 10-20% of the critical damping, considerably greater than structural damping factors for steel frames (in the order of 2%). The characteristics of the elastomer used in the BI devices are defined according to the recommendations of SETRA [3] and to the pre-norm pr EN 1337.
The parametric analysis is based on the variation of the structural elements
lengths (beam spans
Qualitative and quantitative comparisons were made on akin variables (the total
acceleration and the relative lateral displacement of a top-floor node) for a set of
geometric-typological properties ( References
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