This paper will describe the seismic behaviour of masonry infilled RC frame with a central opening structure under reversed cyclic lateral loading. To achieve the purpose of this study, four 1/4-scale single story and single bay RC frame specimens were tested, i.e. one bare frame, one clay brick masonry infilled RC frame without opening and two clay brick masonry infills with a central opening in infills. The ratios of opening size to panel area were 25% and 40%. Through reversed cyclic lateral loading tests, the seismic performance of RC frames with a central opening brick masonry infills was investigated. As the results, significant distinctions of failure mechanism, lateral strength, stiffness, and ductility were observed between these specimens. In the case of infills with a central opening, the cracks sprouted and developed at the corners of the opening. Although the presence of the opening in infill reduces the lateral strength and stiffness overall structure, the brick infilled frames with a central opening of 25% and 40% of panel area show better seismic performance as compared to the bare frame.

Many researchers have performed a lot of studies of the seismic behavior reinforced concrete (RC) frame with masonry infill. They found that masonry infill affects the lateral strength, stiffness and ductility performance of the RC frame structures. However, when openings appeared in the panel infill for door and windows, the responses of the overall structure are entirely changed. The primary purpose of this study is to experimentally investigate the behavior of brick infilled RC frames possessing single opening and two openings. Four specimens of 1/4-scale single bay RC frames with brick infills were made that were one bare frame, one frame with full infill and two frames with infills having a central opening and two openings with the opening ratio of 25%. The specimens were tested under lateral reversed cyclic loads. Consequently, different responses of failure mechanism, lateral strength, stiffness and energy dissipated were observed among the specimens. The brick full infill failed in shear with propagation cracks in central part of the panel, but in the case of the infills with single and two openings, the cracks were dominated at the corners of the openings. The in-plane strength, stiffness and dissipated energy of infilled frames decreased when openings appeared in the panel. However, the seismic performance of brick infilled frame with the opening of 25% of panel area is better than those of bare frame. The brick infilled frames with a central opening and two openings are similar in lateral strength and dissipated energy. It seems that area and position of the openings control the seismic response to the overall infilled frame structure of the openings

In order to get accuration analytical model for describing the lateral strength of brick masonry with openings, a newly simple method was introduced. Comparison of reinforced concrete frame structures with openings and the experimental results of brick masonry with openings (holes) of 25% and 40% was used in this analytical model. In the high-risk seismic areas many reinforced concrete buildings with infill frame with openings. Where the presence of openings will reduce the strength of the wall. In addition, the influence of the area and location openings in the walls are strongly needed to obtain a more realistic method for designing reinforced concrete structures.The brick mansory was assumed as the non-structural component. However, based on the observations after the earthquake, the presence of brick masonry has a significant contribution to the seismic capacity of reinforced concrete structures. The diagonal strut method was used, where the elastic and plastic behavior of the fill-portal by considering the limited ductility of the infill frame material. The comparison of the new analytical model and the experimental brick masonry with opening 25% and brick masonry with opening 40% shows a good agreement. Finally, it can be said that the new analytical model can be used.