Blast and Impact Loading and Response of Structures
Car collision, external or internal blast explosions may initiate a supporting column failure. Such local failure may grow rapidly and turn into a progressive collapse of the entire building or of a major part of it.
Infill walls may contribute to reducing the structural frame deformation and increase its resistance. The equivalent diagonal strut is commonly used as a simplified representation of the infill wall, to enable overall analysis of the entire building. The idea of the equivalent strut and definition of its geometrical and mechanical data are based on the behavior of the infill walls under lateral loads, which has been widely investigated for lateral deformation developed under earthquake loading. However, the orthotropic properties of the masonry infill wall raise questions regarding the suitability of this model to represent the infill wall behavior under vertical deformation that occurs in the case of a column failure.
The present investigation aims to shed light on the behavior of infilled frames in case of a supporting column failure. The results of a large-scale experimental investigation on infilled frames show that the behavior of the infill under vertical deformation is entirely different from the behavior of the same frame under lateral loading, and different failure mechanisms are observed. Experiments show that the infill wall may increase the frame resistance by more than 500% and has a potential to reduce the probability of progressive collapse. The behavior of similar masonry infill walls was examined under lateral and vertical loading and major differences were observed. Based on the experimental results and additional numerical simulations a simplified model of the infill wall behavior under vertical deformation was developed. This model may be used in Progressive collapse simulations to assess the contribution of the infill wall.