Innovative seismic isolation of masonry infills using cellular material at the interface with the surrounding RC frame

Abstract

In this experimental study, a method is presented for the seismic isolation of masonry infill walls from surrounding reinforced concrete frames using polyethylene foam at the interface of infill masonry walls and reinforced concrete frames. The main objective of this research work was to study the change in infill-frame interaction, by using polyethylene sheet for isolation of masonry infill wall from RC frame. For this purpose, two full scaled reinforced concrete frames having infill masonry walls and a window opening, were fabricated. One of the RC infilled frames was having no polyethylene foam at the infill-frame interface (RC Frame 1) while the other frame was having polyethylene foam at the infill-frame interface (RC Frame 2). Data of bare frame was obtained from PhD research work of Engr. Syed Azmat Ali Shah (UET Peshawar, Pakistan). Quasi static cyclic tests were conducted in displacement-controlled manner. Different graphs were plotted from the data obtained during test such as hysteresis curves, energy dissipation curves, envelope or backbone curves, bilinear idealization of backbone curves, stiffness degradation curves and performance levels were also determined for both the RC frames. It is concluded that by using polyethylene foam at the interface of masonry infill wall and RC frame, the infill frame interaction was reduced during early cycles of lateral displacements. At lower values of lateral displacements, response of RC Frame 2 (having PE foam) was similar to bare frame having less stiffness and strength. By further increasing the value of lateral displacement, the polyethylene foam was compressed and therefore infill masonry walls were activated, due to which stiffness and strength of RC Frame 2 were increased and its behavior was similar to infilled frame behavior. It is also concluded that damages produced in infill wall in RC Frame 2 (having PE foam) were less as compared to damages produced in RC Frame 1.