Effect of Masonry Infill Structure with Openings during Progressive Collapse by Removing a Middle Column

Background/Objectives: Progressive collapse occurs when primary structural element fails due to many reasons such as impact, bomb blast, earthquake, abnormal loading etc., resulting in the failure of adjoining structural elements, which in turn causes partial or total collapse of the structure consequently. It is studied widely in Reinforced Concrete (RC) framed structure. Methods/Statistical Analysis: The present study investigates the comparative behaviour of four bay, five storey RC bare frame, infilled frame and infilled frame with openings and to assess the effect of infill to resist the progressive collapse. A linear static analysis is carried out using finite element software using SAP 2000 and maximum moment (M), shear force (V), axial force (P), deflection (U) for both beams and columns generated before and after middle column removal are studied and compared. Findings: There is an average of 30% and 34% decrease in moments for infilled frames when compared to a bare frame. The percentage of decrease in moments increases to an average of 71% when the column is removed. Similarly, the deflection for infilled frames decreases by35% when compared with bare frame and only 17% increase when infills are provided with openings on removal of column there is average of 88% decrease in deflection for infilled frames when compared with bare frame. It shows that the presence of infilled frames will delay the progressive collapse when compared to bare frames. Application/Improvements: The study can be extended to the non-linear range and also to find its dynamic response.