Robustness assessment of reinforced concrete structures for different failure scenarios

This study describes the robustness assessment of 3D reinforced concrete structures analyzing the response of the 2D frames in different design configurations and failure scenarios. The structures are characterized by both frames with wide beams and seismic-resistant frames with deep beams. Three structural design configurations are investigated: the code configuration and two configurations improved with respect to robustness. For any configuration, four different failure scenarios are considered, removing specific supporting columns. For any failure scenario and design configuration, 2D non-linear finite element (NLFE) simulations are carried out to evaluate the behavior of the two frames along the two orthogonal directions. In any analysis, the contribution of the frame, located along the orthogonal direction, is considered by means of translation springs having non-linear constitutive laws specific for the inward and outward movements. By imposing an increasing displacement at the top of the removed column, the corresponding capacity curves have been defined. Successively, the two plane NLFE capacity curves are superimposed to define the global response of the framed structure. This superposition is validated through the comparison with 3D non-linear analyses. The results demonstrate the importance of calibrating the non-linear constitutive laws of the springs, particularly for large vertical displacements and some failure scenarios. The frames with wide beams improve, especially, the global ductility. In addition, it is confirmed the superposition of the plane NLFE capacity curves of the two orthogonal frames. Finally, by means of the energy-based approach, the benefits of the robustness design improvements are highlighted.