Introduction:
Retrofitting
refers to the addition of new technology or features to older systems. It is method
of increasing resistant capacity of structure by various techniques without
changing its original appearance. Talking about Seismic retrofitting, it is the
modification of existing/ damaged structure to make them more resistant to
seismic activity, ground motion, or soil failure due to earthquakes. It can
also be defined as increasing the seismic resistant of damaged structure by
various techniques. fig.retrofitting in supreme court of nepal
Selection of retrofitting methods derived from the
earthquake survey ,depends on mode of failure, weak and strong design aspects
and structural behaviors. Retrofitting
helps upgrade the earthquake
resistance up to the level
of the present day codes by appropriate techniques.
Concepts
including strengthening, repairing and remolding involved in this process of
Retrofitting. It is an
upgrading of certain building system, such as mechanical, electrical, or
structural, to improve performance, function or appearance. After many
natural disasters , different architecture gets destroyed. To preserve it,
retrofitting is one of best alternative technique applied by Engineers.
fig. Basic model of Retrofitting.
The April 2015 Nepal earthquake (also called Gorkha
earthquake) killed nearly 9,000 people and 22000 houses.
Different historical,valuable,cultural and old monuments including UNESCO World Heritage sites in the Valley, including Kathmandu Durbar Square, Patan Durbar Square, Bhaktapur Durbar Square, Changu Narayan
Temple, Boudhanath
stupa and Swayambhunath Stupa were highly affected. Including
this, various government and non government organization, institutions,officesetc.
were highly destroyed.
Basic
concepts of Retrofitting :
Ø Up gradation of
lateral strength of the structure.
Ø Increase the
ductility of the structure.
Ø Increase
strength and ductility.
Ø strengthening,
repairing and remolding
Benefits
of Retrofitting :
ü Optimization of
existing plant components
ü Adaptation of
the plant for new or changed products
ü Increase in
piece number and cycle time
ü Guaranteed spare
parts availability
Needs
of Retrofitting in Nepal
ü There are
considerable number of RCC structure in Nepal that do not meet the requirements
of the current design standards because of inadequate design and/or
construction errors and need structural upgrading specially to meet the seismic
design requirement
ü After 2015(2072) earthquake, the awareness and need
of seismic detailing has increased
ü Retrofitting is
the best solution to strengthen such building without replacing them.
Advantages
of Retrofitting over Reconstruction:
Criteria
|
Demolition
and reconstruction
|
Retrofitting
|
Involved
costs
|
High
|
Low
|
Time
for construction
|
>1
year
|
3-4
months
|
Disturbance
to regular function
|
High
|
Low
|
Disposal
of Scrapped material
|
Big
problem
|
No
problem
|
Technology(adaptability)
|
Usual,
so no excitement
|
New,
so high excitement, need training
|
Potential
Impact (Replicability)
|
Low/Medium
|
High
|
Reference
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