Computational Investigation of the Fundamental Period of Reinforced Concrete Frame Buildings with Masonry Infilled Walls

The fundamental period of reinforced concrete (RC) 3D special and intermediate moment frame buildings with and without infilled wall simulation, and also considering the effect of a different number of bays and stories, was investigated. The infilled walls were modeled with the gap between the walls and the columns. The numerical results indicated that the masonry infilled walls have a great effect on the lower height RC frame structures. The infilled walls reduced the fundamental period of the RC intermediate and special moment frames by 53% to 70% and 26% to 57% for the 5- stories frame buildings, and by 37% to 55% for 43% to 49% for the 15-stories frame buildings. Therefore, the fundamental period of the RC intermediate moment frames is more sensitive than the RC special moment frames, particularly in the low-rise buildings. However, by considering the infilled walls, the plan type has a significant effect on the fundamental period of the RC frame building, and by ignoring the infilled walls, the plan type will have a negligible effect on the fundamental period of a RC building frame structure. Moreover, a relatively simple formula was proposed to calculate the fundamental period of RC frame buildings with infilled walls.