Seismically resistant progressive collapse behavior of infilled frame structures under seismic loads and column loss: A numerical investigation

This research investigated the seismic performance of multi-story reinforced concrete (RC) frames with infilled walls. The study employed a two-step numerical approach: first, a verification process ensured the model's accuracy by comparing it to past experimental results. Following validation, a parametric study explored various factors influencing the frames' behavior. These factors included the number of stories (3, 6, and 12), the earthquake ground motion (Vrancea, El Centro, and Kahramanmaras,), and the effect of removing an internal column. Additionally, the study examined the impact of incorporating polypropylene (P.P.) fibers into different parts of the structure: the RC frame itself, the mortar between infill wall bricks, or both. The findings revealed significant improvements in seismic performance due to the presence of infill walls. In the three-story frame, the wall reduced plastic drift by a remarkable 98.9 %. Furthermore, strengthening with P.P. fibers demonstrated exceptional effectiveness. For example, on the first floor of the three-story frame, the maximum drift value dropped from 0.751 to a 0.004 for the IRCPM model (fibers in the infill wall mortar only) and even lower (0.003) for the IPPM model (fibers in both the RC frame and infill wall mortar). These results highlight the potent ability of P.P. fibers to improve earthquake resistance. The study also assessed the efficacy of strengthened infill walls as partial replacements for lost columns. When an internal column was removed, the presence of a P.P. fiberreinforced wall (IPRCL model) helped mitigate the structural impact, reducing the base shear force by 11 % compared to the control model without fibers (CIRCL). Similar trends were observed in taller frames. While including fibers in the RC frame of the 6-story model with a removed column resulted in an 11 % decrease in base shear force, models with fibers in the wall components of the 12-story frame exhibited a 31.62 % increase in base shear force after column removal.