AN ALTERNATIVE APPROACH FOR ASSESSING ECCENTRICITIES IN ASYMMETRIC MULTISTORY BUILDINGS

摘要

The approximate method, presented in the companion paper, for assessing modal eccentricities of elastic multistory buildings with simple eccentricity is extended in systems composed by elastoplastic resisting bents. Following the technique of the aforementioned paper for computing modal properties of such buildings by means of an equivalent single-story system composed of elastic elements, modal capacity curves of these systems may also be drawn when the resisting elements are defined by a bilinear force-displacement (characteristic) curve. The procedure for constructing element-characteristic curves is based on the methodology presented by the author in an earlier paper, and modal capacity curves of the equivalent single-story system may be drawn by performing a non-linear pushover analysis using the inertia force eccentricity of each mode of this system. Therefore, base shears and their eccentricities for the first two modes of vibration of multistory inelastic buildings can be determined as in real one-story non-linear systems. The method is illustrated in a 10-story partial symmetric building, having along the direction of the ground motion three identical, inelastic, coupled wall bents. The structure is analyzed for a strong ground motion, equal to 1.5 × El Centro earthquake excitation, and the results are compared with those obtained from a step-by-step non-linear time history analysis of the discrete member model.