Recently Identified Aspects of Ductile Seismic Torsional Responcse of Reinforced Concrete Buildidngs
Appears on pages(s):
codes; deflections; ductility; earthquake-resistant structures; reinforced concrete; stiffness;strength; structural design; torsion in buildings
With few exceptions, code provisions relevant to torsional phenomena in buildings subjected to seismic effects, are based on elastic structural behaviour. The key parameter is stiffness eccentricity. The appropriateness of this approach to the design of systems expected to respond in a ductile manner is questioned. The degree ofrestraint with respect to system twist, strength eccentricity and the pattern of element yield displacements are considered to be more important parameters. For the purposes ofseismic design, bi-linear force-displacement approximations of the elasto-plastic behaviour of reinforced concrete systems and their constituent elements, are considered to be adequate. Strategies aiming at the elimination of undesirable effects of torsional phenomena in ductile systems are addressed. The findings of this study are based on a re-definition of some common terms of structural engineering, such stiffness, yield displacement and displacement ductility relationships. Contradictions withcorresponding terms applicable to elastic systems are demonstrated. The introduction ofthese features, relevant to bilinear modelling of reinforced concrete elements, precedes the examination of the designer’s options for the control of earthquake-induced displacement demands resulting in system translations and twist.