ANALYTICAL METHODS TO ASSESS THE COLLAPSE AND DAMAGE OF REINFORCED CONCRETE WALLS

Abstract

During the great 2010, Chile earthquake, reinforced concrete (RC) buildings showed adequate performance. However, in some of them a particular damage pattern involving brittle failure of RC walls was observed in the lower stories, usually associated with high axial loads and vertical irregularities. The brittle nature of the failure led to a sudden degradation of the bending capacity and lateral stiffness of the walls. Significant research including experimental campaigns and numerical models has been conducted in order to describe the observed damage in RC walls and identify the possible causes of this behavior. This research studies the collapse and damage of shear wall buildings during the Maule earthquake using state-of-the-art analytical models. The proposed analytical research lies within the family of micro models, and uses finite element models with 4-node shell elements to represent the physical interactions that occur in the wall section at finite element level. Inelastic finite element models were developed in DIANA, and the concrete was modeled following the total strain rotating crack approach. First, different stress-strain constitutive relationships for concrete in compression were evaluated and validated with experimental data. The stress-strain constitutive laws were regularized by preserving the compressive fracture energy, for both, unconfined and confined concrete. Once the constitutive models were validated, a real RC resisting plane damaged during the 2010, Chile earthquake was studied in detail, and the observed damage pattern reproduced by means of two-dimensional inelastic pushover analysis. It can be shown that the damage geometry of the shear wall cannot be correctly represented by conventional inelastic models that ignore the true deformation kinematics with lateral and axial interaction. Indeed, the failure mechanism of resisting planes shows strong coupling between lateral and vertical deformations in the plane. Finally, results of a three dimensional inelastic dynamic analysis of the entire building are presented, which show to be consistent with the observed damage after the earthquake and with the 2D model results.