Parametric study of the progressive collapse of 2D framed structures

In this paper we study the response of 2D framed structures made of reinforced concrete to the sudden removal of columns. For comparative reasons, the 2D frames are considered as part of 3D structures with same overall structural mass and external load potential. In particular, we study two sets of 2D frames, with different height-bay ratio λ of the structural cells. Each set counts 3 frames with different hierarchical level n, defining structures that range from hierarchical to homogeneous. Hierarchical structures have massive primary structure consisting of few large elements while homogeneous structures are made of many thin structural elements. Employing an algorithm based on Discrete Elements, we simulate progressive collapse until the final stage, considering collisions between the structural elements and with the ground. We point out the mechanisms that trigger progressive collapse when the columns are strong and when they are weak. We quantify the robustness in terms of Reserve Strength Ratio RSR and show the influence of λ and n on the RSR, that depends on the activated collapse mechanism and on the extent of the initial damage.