A review of code provisions for torsional seismic effects in buildings
DOI:
https://doi.org/10.5459/bnzsee.30.3.252-263Abstract
A series of recent studies of the seismic torsional response of ductile buildings is condensed and extended to serve as a basis for recommendations for possible amendments of the relevant clauses of the current New Zealand loadings standard [1]. It is postulated that the primary seismic design aim, associated with criteria of the ultimate limit state, should address displacement ductility demands and supply, as affected by twisting of the system, rather than torsional strength. Some well-established parameters, such as yield displacement, element and system stiffness, are redefined to enable the inelastic deformation pattern of rigid diaphragms to be simply quantified. The presentation concludes with specific recommendations and corresponding commentaries in a form suitable, with editorial modifications, for possible adoption as codified design requirements. To illustrate both the relevance of the recommendations and their simplicity, two numerical examples, showing the evaluation of the displacement ductility capacity of a model structure, are appended.
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