Modelling failure analysis of RC frame structures with masonry infills under sudden column losses

Robustness of structures is fundamental to limit progressive collapse of buildings in case of accidental loss of columns due to explosions, impacts or materials deterioration. Modelling of progressive collapse response of reinforced concrete (RC) frame structures needs considering extreme geometric and mechanical nonlinearities. Moreover, in the case of infilled frames the collapse mechanism becomes more complex because of the frame-infill interaction. This paper presents a numerical study aimed at proposing: A) an appropriate fiber-section modeling methodology for reinforced concrete frames under large displacement progressive collapse events; b) a new multi-strut fiber macro-element model to account for the influence of masonry infills in the progressive collapse response. Proposed numerical models are developed using the OpenSees software platform. The predictive capacity of the proposed methodology is widely validated in the paper through comparisons with experimental test results and refined numerical simulation pushdown test results. Results show that the new equivalent-strut modeling approach can be suitably employed as a simple assessment method when numerical simulation of progressive collapse scenarios is needed for bare and infilled reinforced concrete frames.