Structural robustness of reinforced concrete moment resisting frames: deterministic and reliability assessment

This work describes the robustness evaluation of a 2D reinforced concrete moment resisting frame designed in a highly seismic area. In detail, the loss of the central column at the ground-storey level is assumed to trigger the progressive collapse of the frame. At first, a deterministic analysis is elaborated by modelling the frame in the finite element software (FEM) ATENA 2D and performing non-linear pushdown analyses. These analyses consist in applying an increasing vertical displacement in the point of column removal and registering the corresponding reaction. By means of the derived displacement-reaction curves, the capacity of the structure against the removal of the supporting column is studied. Then, a full probabilistic approach is adopted, by sampling 100 different realizations from both material and load properties to evaluate the reliability of the frame. By performing static equivalent non-linear analyses (i.e., amplifying the gravity loads according to properly calibrated dynamic amplification fac-tors) the probability of failure in different cross-sections of the structure is computed. The results demonstrate the lacking safety level associated to the frame under a progressive collapse scenario.