Some fundamental aspects of torsionally coupled structures
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Date
2000
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Abstract
Buildings with coupled lateral and torsional motions are continuously cited as classical examples of structural damage during an earthquake. There is nothing intrinsically wrong with a coupledstructure that justifies such damage; rather, the problem is a poor estimation of the inelastic displacement demand of the resisting planes. Since, the three-dimensional inelastic behavior of a building is rarely used in the building design, approximate code procedures are used for estimating the demand. It is well recognized now that even for single-story structures, the inelastic seismic response is not amenable of being encapsulated into simple code-like rules. Consequently, one procedure for simplified analysis of such structures has been devised. This procedure is based on the use of an ultimate surface in the story shears and torque space. This surface is used in this paper to explain certain research results on the topic as well as to introduce some basic aspects of the inelastic behavior of torsionally-coupled structures. Two examples are presented in which these surfaces have been used in conjunction with a simplified structural model to compute the inelastic response of a base-isolated structure and a seven story reinforced concrete building.