Effect of partially infill wall on the seismic behavior of RC frame buildings

Abstract

The partially infilled Reinforced Concrete (RC) frames have been one of the major victims of the earthquakes in the past. It is normally called as the captive column effect wherein the lower portion of the column is kept captive by the surrounding infill wall while the upper portion is allowed to deform laterally. The upper free portion of the column attracts huge shear force during earthquakes and might get severely damaged and possibly lead to the collapse of the buildings. Although there are a number of studies conducted on the masonry infilled RC frames in general, yet partially infilled frames have not been adequately studied under the dynamic load. In this study, a three storey RC building with partially infill wall on the ground floor is studied under the ground motions with the 475 year return period. The height of the infill wall is varied along the height of the columns and the resulting shear demands are estimated. To study the mitigation measures of the captive column effect, the shear and moment capacities of the ground floor columns are increased by factors of 2.5 and 4 times the original design strength. It was found that the captive column effect is maximum when the infill wall height is 75% of the column clear height. Increasing the shear strength of the column is found to be beneficial but providing the infill wall up to the full height of the column to eliminate the short-column effect is still the most desirable for structure protection.