Abstract
A key aspect of the seismic design of structures is the distribution of the lateral strength, because it governs the distribution of the cumulative plastic strain energy (i.e., the damage) among the stories. The lateral shear strength of a story i is commonly normalized by the upward weight of the building and expressed by a shear force coefficient αi. The cumulative plastic strain energy in a given story i can be normalized by the product of its lateral strength and yield displacement, and expressed by a plastic deformation ratio ηi. The distribution αi/α1 that makes ηi equal in all stories is called the optimum yield-shear force distribution. It constitutes a major aim of design; a second aim is to achieve similar ductility demand in all stories. This paper proposes a new approach for deriving the optimum yield-shear force coefficient distribution of structures without underground stories and equipped with metallic dampers. It is shown, both numerically and experimentally, that structures designed with the proposed distribution fulfil the expected response in terms of both damage distribution and inter-story drift demand. Moreover, a comparison with other distributions described in the literature serves to underscore the advantages of the proposed approach.
Highlights
Conventional seismic design allows for damage to a structure under rare or very rare seismic events for economic reasons
This paper proposes a new expression for the optimum yield-shear force coefficient distribution of structures without underground stories and equipped with metallic dampers, for application in the framework of the energy-based seismic design approach
This allows to assume that if the ground motion is scaled down by a factor sy so that the level of plastic deformation in the dampers is zero, i.e., ηi = η ≈ 0, the maximum total elastic force developed by the dampers at each story i in each mode n, s Qmaxn,i, coincides with the lateral strength required on the dampers in each mode n, s Qyn,i, to carry all stories to the brink of yielding, that is s Qmaxn,i = s Qyn,i
Summary
Conventional seismic design allows for damage to a structure under rare or very rare seismic events for economic reasons. In contrast to previous approaches that resort to regression analyses of the responses obtained through iterative trial-and-error calculations of structures subjected to a set of ground motions, the optimum yield-shear force distribution proposed in this study involves applying modal analysis formulation and two basic assumptions: (i) damage basically spreads out evenly among the stories regardless of the level of plastic deformation; and (ii) the ductility demand is approximately the same in all stories. The validity of these assumptions for structures designed with the optimum distribution has been demonstrated in past studies [7].
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