Challenges Posed by Tall Buildings to Indian Codes

Abstract

What should be the criteria for limiting height of a building in a given location in the country? Who should specify that limit? Height limitations can be imposed by the local authorities based on the availability of services or heritage considerations, or by the codes based on technical considerations. It is the earthquake loading code that specifies different types of structural systems appropriate under different seismic zones and for various heights. But Indian Standard (IS):1893 does not restrict the height of any building except prohibiting ordinary shear wall frames in seismic zones IV and V. The American Society for Civil Engineers (ASCE) 7 code specifies seismic design category based on its risk category and the severity of the design earthquake ground motion at the site under consideration and restricts certain types of structural systems and their heights. In India, there appears to be no rules or restrictions for developing the plan or a structural system for a tall building. Plans with numerous reentrant corners and offsets are being used. Flat slabs are also being used with and without shear walls. Normal weight bricks are being extensively used for walls without any anchorage. Besides, IS:13920 specifies same level of detailing for ductility for all buildings irrespective of the seismic zone and type of building. There are no guidelines for employing energy dissipating devices and base isolation. It is concluded that there is a need to update the code provisions in IS:456, IS:875, IS:1893 and IS:13920 on an urgent basis.