Disaster Recovery and the Road Ahead - IGNOU

achieved by strengthening the various elements like beams, columns, walls and foundations to turn
the structure anew. The seismic behaviour of existing buildings is affected due to various inadequacies,
material degradation due to time and various changes carried out during the period when the
structure remains under use. Due to various social and other factors, it is not possible to replace
such buildings. Thus, it becomes very important to strengthen the existing buildings seismically.
DID YOU KNOW?
The various codes on earthquake resistant design lay emphasis on the following features
in a building for proper earthquake resistance, entailing desirable properties of ductility,
deformability and damageability:
Structural integrity of all elements of the building like walls, roof, etc.
Diaphragm action in roofs and floor
Provision of bands at different levels like plinth, sill, lintel and roof
Reinforcement around openings
Provision of reinforcement at critical sections
Strengthening after the Earthquake Damage
Here the strength of the structure has to be improved to resist the earthquake forces which are
dynamic in nature. To achieve this, a few new structural elements may require to be added to take
care of the earthquake forces. The dwellings constructed in such a manner thus have no earthquake
resistant features. Some of the weaker points identified in these houses, from earthquake point of
view are:
Wooden under-structures for lateral forces
No bonding between the walls of the stone structures
No necessary beds within the house to provide an integral action in the structure
Massive weight of the walls and the roofs
For retrofitting of houses, following components need to be adopted:
Strengthening the wooden frame to increase its lateral
strength, by installing knee bracing
Stitching the outer and inner wythes of the stone walls
by the installation of ‘through’ stones
Providing a seismic belt around the house
Reducing weight over the roof by soil removal and
water proofing
Retrofitting goes beyond superficial repair and aims at
upgrading of structures. It includes:
Repairing doors and windows Illustration 4
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