SEISMIC RESPONSE OR MULTI-STORY UNBALANCED R/C DUAL BUILDINGS. I: CONCEPT OF DUCTILITY DEMAND

In this study, to determine the effect of different source of eccentricities on the ductility demand distribution of asymmetric RC dual lateral load resistant multi-story buildings, two types of eccentric plan asymmetric models were developed. Since rigorous modeling of inelastic behavior of RC structural members was used, the stiffness distributions of the models are assumed to be related to the strength distribution. This modeling approach is more accurate for multi-story dual lateral load resistant structures, as it adjusts the stiffness of the structural elements based on their strength at each time step. The concept of stiffness eccentricity is modified and used to evaluate the torsional responses of the models. The torsional responses of models including the ductility demands for both stiff and flexible edges elements are normalized to the corresponding values of the symmetric models. It is concluded that using longer shear walls in the flexible edges would impose very large ductility demands as the wall yield displacement is lower and the wall experiences the higher ultimate displacements. Therefore the substantial differences in ductility demands between flexible and stiff edges suggest a need for reassessment of the pertinent code provisions. Also, the distribution of the normalized ductilitydemands along the height of structures is used to assess the torsional effects in multi-story structures.

Keywords:

Strength-Dependent Stiffness , Ductility Demand , Inelastic Torsion , Asymmetric Structures