SEISMIC RETROFITTING OF DORMITORY BUILDINGS WITH SOFT STOREY AND FLOATING COLUMNS

Nakul Singh, Vikram Singh Kashyap

Abstract: Many of the existing building are lacking in adequate earthquake resistance because these are not designed according to modern codes and prevalent earthquake resistant design practice. Also many building that are damaged in earthquake may need not only be repaired but also upgraded of their strength in order to make them seismically resistant. The seismic evaluation and their retrofitting is one of the most challenging task for the structural engineers. The means of retrofitting is to upgrade the strength and structural capacity of the structure to enable it to safely withstand the effect of strong earthquake. There has been a substantial increase in the topic of seismic retrofit of existing buildings in recent years as evidenced by the growing number of research papers published in this area. Attention has been focused worldwide on both building and bridge structures and with the widespread damage to older buildings and bridge structures in the relatively recent bhuj earthquakes, government/owners have begun to take action to prevent similar damage to existing structures in future earthquakes. Open ground storey/soft storey along with the floating columns has been a peculiar feature in the latest multi-storey buildings in India. These features are hugely inadmissible in the buildings which are built in earthquake prone areas. In this Paper, after understanding the behaviour of buildings in earthquakes, why, when, where and how seismic retrofitting is done with shear wall and chevron bracing. Further, a study is performed on an example dormitory building different model with open ground storey and floating columns to highlight the importance of their presence in the seismic analysis using computer program STAAD Pro.V8i The analysis is done with Equivalent Static Analysis/linear elastic static analysis and Response Spectrum Analysis/linear elastic dynamic analysis, as per IS:1893-2002. Various features of lateral stiffness strengthening system, namely lateral bracings, shear walls, increasing the column size in the soft ground storey and their combinations, and are proposed to reduce the stiffness irregularity and discontinuity in the load path incorporated by the soft ground storey and the floating columns respectively. Also, it is inspected that the shear walls are most impressive when used as one long structural wall instead of two short walls having separated by the interrelated beams, and properly placed at the periphery of the buildings to avoid the torsion. It is also noticed that the Chevron braces are most productive when placed under the floating columns to make the force transfer less horizontal

Keywords: Floating Column, Dormitory Building, Static And Dynamic Analysis, Seismic Retrofitting, Soft Storey.

DOI: https://doi.org/10.15623/ijret.2016.0512021