Progressive collapse of 2D framed structures: An analytical model

• An analytical model for the collapse of 2D frames after column removal is presented.
• The collapse-mechanism-dependent expressions of the collapse load are obtained.
• A parameter is derived, which predicts what collapse mechanism is triggered.
• The results are compared to data from dynamic nonlinear simulations.
• The proposed analysis can facilitate a preliminary robustness-oriented design.

An analytical model for the collapse of regular 2D framed structures after column removal is presented. Under simplified conditions, we obtain closed form expressions of the upper and lower bounds of the collapse loads, which depend on the activated collapse mechanism. A quantitative geometric/mechanical parameter is also determined that, for a given initial damage, indicates what collapse mechanism is triggered. For several scenarios we evaluate the resistance against progressive collapse initiation as the ratio between the dynamic collapse load after damage and the static collapse load before damage. Our results are compared to data from dynamic nonlinear simulations. The analytical procedure developed here suggests a strategy for a preliminary robustness-oriented design, involving specific solutions in terms of redundancy, compartmentalization, and mechanical properties of columns and beams.