Prediction of local inelastic demands for RC frames designed according to Eurocode 8.

In order to predict the distribution of forces and deformations in reinforced concrete (RC) frame structures under the maximum credible earthquake that can occur at the site, accurate models of the hysteretic behaviour of the different critical regions of the structure are necessary. To date many analytical models for the nonlinear analysis of RC frame structures have been proposed. These range from very refined and complex local models to simplified global models. The limitation of the simplified global models is their inability to simulate the local behaviour of critical regions and yield accurate estimates of strain and curvature ductilities. On the other hand, the high computational cost associated with refined finite element models is a clear impediment in their use in large dynamic simulations. The model used in the present study belongs to an intermediate class of models, that can be utilized with some success for, both, global response studies of high-rise RC frames and local response studies of structural elements. The hysteretic load-deformation behaviour of RC frame members arises from a combination of flexural rotation due to yielding and bond-slip of reinforcement in the inelastic zone, pull-out of reinforcement in beam-column joints and anchorage zones, and shear deformation, including shear sliding. A rational analysis of the hysteretic behaviour of RC members needs to be based on the description of all deformation sources and of the interactions between the different mechanisms. This approach permits the determination of the relative contribution of each source of inelastic behaviour to the local and global response of RC frames. To date few comprehensive investigations of the effect of the hysteretic behaviour of critical regions on the local and global seismic response of multi-story RC frames are available. The present study aims at improving the state of knowledge in the field. The effect of modeling of inelastic regions on the nonlinear local seismic response of an RC framed building designed according to Eurocode 8 (EC8) under two different ground motions is evaluated. These studies are limited to hysteretic response of critical regions with stiffness but no strength deterioration, thus the effect of softening of critical regions on local response is not investigated in this paper.