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Civil-Comp Proceedings
ISSN 1759-3433 CCP: 79
PROCEEDINGS OF THE SEVENTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY Edited by: B.H.V. Topping and C.A. Mota Soares
Paper 178
SDOF System Demands for Performance-Based Design of RC Structures B. Taskin+*
+Department of Civil and Environmental Engineering, University of California-Berkeley, United States of America
Full Bibliographic Reference for this paper
B. Taskin, "SDOF System Demands for Performance-Based Design of RC Structures", in B.H.V. Topping, C.A. Mota Soares, (Editors), "Proceedings of the Seventh International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 178, 2004. doi:10.4203/ccp.79.178
Keywords: reinforced-concrete, single-degree-of-freedom systems, non-linear dynamic analysis, performance based design, stiffness degradation, structural demands, inelastic deformation ratios.
Summary
This paper is focused on the single-degree-of-freedom (SDOF) systems, which
are generally substituted to calculate the seismic demands of a
multi-degree-of-freedom (MDOF) system as in nonlinear static analysis procedures described in
ATC-40 [1] or FEMA-273 [2] and FEMA-356 [3]. It is widely agreed that nonlinear
static analyses are satisfying when a target displacement is encountered and
commonly, this target displacement is determined from the analysis of an equivalent
SDOF system.
Recently, many researchers realized studies on SDOF systems, using different structural characteristics, to pronounce a few: yield strength, ductility, strain-hardening ratio, structural safety levels, etc. within a period range of SDOF systems under the effect of recorded strong motions. Despite the attractiveness of bilinear model's simple application, many studies have demonstrated the significance of stiffness degradation, especially for reinforced-concrete (RC) structures of low to moderate heights.
In this investigation, it is aimed to contribute the recent research by analyzing 156
different SDOF "stiffness-degrading" systems having eight different either ductility
or yield-strength levels with four different strain-hardening ratios. For comparative
purposes, all of the structures are investigated by both bilinear and
stiffness-degrading (modified-Clough) hysteretic models. Excluding the three ensembles of
NERHP site classes B, C, D and two small magnitude ensembles, the rest 130
ground motions of Chintanapakdee and Chopra's [4] strong motion database is used.
The selected 130 motions, making a total of six ensembles represent large
magnitude small or large distance earthquakes as well as near field motions with
fault normal and parallel components either recorded on rock or soil. Computations
are carried out for constant ductility or constant yield strength (reduction factor)
SDOF systems having a damping ratio of are obtained for all six of the ground motion ensembles. Here, ![]() ![]()
It is illustrated in the study that the significant difference in the values of the
inelastic deformation ratios calculated by bilinear and stiffness-degrading models are
observed within the acceleration sensitive region of the response spectrum. The
median of It is concluded that low to moderate rise RC structures in earthquake zones should be evaluated considering the stiffness degradation effect hence its significance in the acceleration sensitive region of the related spectrum. Finally, two empirical equations to calculate the inelastic deformation demands of stiffness degrading SDOF systems are proposed. References
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