Application of a New Methodology of Seismic Torsion Design To a Multi-Story Building Structure

Abstract eng:
An experimental research using a 1:5 scale five-story reinforced concrete building model with the irregularities of a soft/weak story and torsion at the ground story revealed that the design eccentricity used in the general codes in itself cannot represent the critical torsional behaviors not only because the range of eccentricities at the peak responses in the time histories of drift and base shear exceeded the range of eccentricity predicted by the code, but also because under severe ground excitations even very small eccentricity does not necessary translate into a small but significantly large drift at the edge frame. To overcome this problem, instead of using the eccentricity as design parameter, a completely new methodology in the design or control of torsionally unbalanced building structures is proposed by defining the design torsional moment in a direct relationship with the shear force given as an ellipse with the maximum points in its principal axes located by the two adjacent torsion-dominant modal spectral values. In this paper, the proposed methodology is applied to the design of a torsionally unbalanced five-story RC building model. Linear and nonlinear time history analyses of the building model are carried out, and the torsional behaviors of the structure designed according to the proposed methodology are evaluated by comparing demand and supply in shear versus torsion relationships in each story.

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