‘Buildings are constructed following BIS earthquake codes’

HT Bureau

GUWAHATI, April 28: Assam Real Estate & Infrastructure Developers’ Association (AREDA) on Wednesday stated that buildings in seismic zone 5 like Guwahati are constructed following the mandatory norms issued by BIS earthquake codes and hence they are resistant to even heavy and devastating earthquakes.

In a statement, AREDA president PK Sharma said that the BIS Codes norms indicate that in case of minor earthquake the building will suffer no damage.

In case of moderate earthquake there would be no damage to structural members but cracking and damage to non-structural components allowed.

While in heavy and devastating earthquakes, damage to even structural members are allowed but buildings must be standing with no loss of human lives.

“The impact of the earthquake was definitely in the heavy and devastating category,” AREDA stated.

Sharma further stated that AREDA has extensively surveyed the earthquake damage and found that damages suffered by the buildings are primarily non-structural damage like wall cracks and the load bearing RCC frame has performed well in all the buildings inspected. “Wall cracks and other non-structural damage have been found which only proves that the RCC frame has performed on expected lines with sufficient ductility to shake without failure,” AREDA stated.

Sharma pointed out one of the mandatory objectives of earthquake resistant constructions is to achieve the required ductility in the building RCC frame.

Ductility is the elasticity of the RCC structure of beams, columns slabs and foundation giving it the ability to shake and sway without deformation when subjected to seismic forces.

“It is the most desirable quality for good earthquake performance as this enables the structure to absorb energy and save the building from collapsing. This ductile RCC frame is connected to non-ductile non RCC members like walls, which are essentially non-structural components and these obviously develop cracks as they cannot shake without deformation like the ductility or elastic RCC frame. Provisions of the BIS earthquake codes never intended to prevent wall cracks in a massive earthquake like this one,” Sharma said.

Sharma further said that the earthquake on Wednesday morning with devastating combination of shallow depth, short distance from epicentre and high magnitude has generated highly destructive seismic forces on the buildings.