Comparative Study on Dynamic Response of Buildings with Floating Columns

High-rise buildings are essential for providing the necessary space for both residence and offices due to the lack of large areas in an urban setting. However, these multi-storey buildings are prone to lateral loads such as earthquake loads due to their large mass. Often, columns of such multi-storey buildings are truncated at some level either due to some obstructions or some architectural restrictions. Such columns that do not directly rest on the foundation are called floating columns. The floating columns are generally considered harmful, especially for buildings constructed in seismically active areas. Their existence creates a discontinuity in the path to transfer the load resulting in an inadequate structure performance. Hence, this study focuses on reducing the risk factor due to seismic effects by strengthening buildings with floating columns using the shear walls, bracings, and masonry infills. A typical building with floating columns located at two different seismic zones was considered for the study. This building was strengthened by considering various approaches such as diagonal bracings, shear walls and infill walls. The equivalent static method is used in the study to carry out the seismic analysis. The results indicate that using any strengthening methods mentioned above can significantly reduce storey displacements. However, providing a shear wall is found to be more effective in reducing the storey displacements in both the directions of earthquake forces when compared with other methods. Though infills and bracings can reduce storey drifts, it was also found that at lower storey levels, there is a considerable increase in the storey drifts when bracings and infill walls are considered. This is mainly attributed to the presence of the open first storey. However, the storey drift values reduce at the higher levels.