The effect of increasing span length and storey height on the progressive failure of reinforced concrete frames with different percentages of openings in the masonry infilled wall

Buildings may be subject to various external threats throughout their lives. These threats can cause progressive Collapse to the structure by damaging the critical structural elements. Studies on structural systems failure in recent years highlight the importance of the progressive collapse phenomenon caused by abnormal loading like crashes, terrorist attacks, explosions, earthquakes, and so on. In this study, the performance of 6-story masonry infilled reinforced concrete frames with varying percentages of openings in progressive failure due to varying span length and floor height is investigated. The frames examined have RC moment-resisting frames that are designed by the Iranian Building code. Progressive collapse simulation by alternative path method by removing the middle column of frames in OpenSees software with nonlinear static analysis. According to the results, In the case frames with 10%, 20%, and 30% openings in the infilled masonry wall, their maximum strength reduced by about 23%, 31%, and 39%. Also, the frame with openings reduces about 62% of the maximum force against the without openings frame. The results show that increasing every 0.5 m of span length from 4 to 6 m, on average, increases the force by about 9%. Also, increasing the height of the floor from 3 to 4 meters, on average, increase the strength of the frames by 13%. The results of this study showed the positive effect of infill, increased span length from 4 to 6 meters and height from 3 to 4 meters, the class is in the process of progressive collapse of RC frames.