Manual calculation of push-down curve of RC building with lost column at first floor

In this paper, a simple mechanical model to predict the push-down response of a reinforced concrete building subjected to the instantaneous loss of central, intermediate, or corner columns is proposed. Model allows one to derive analytically and in a closed form load and deflection values considering the formation of flexural, arch, and membrane strength mechanisms in beams, columns, and slabs A satisfactory comparison with other existing analytical models of literature able to calculate the multi-linear push-down curve of reinforced concrete buildings subjected to instantaneous loss of a column at the first floor was made. Finally, it was stressed by using the proposed model, that buildings designed in the last decades in Europe for gravity load are not always safe in terms of robustness against progressive collapse phenomena due to the loss of first-floor column.