The increased
frequency of earthquakes around the world has brought home the urgency of
a planned program for ensuring safety in design and instruction of new
buildings and comprehensive need for retrofitting the existing building against
collapse during disasters such as earth quakes, cyclones or flooding.
1. At the time
of building construction, there may not have been idcquate concern
regarding disasters such as earthquakes and hence the building might have been
executed withoutfulfilling the requirements if safety measures.
2. In the case of
old buildings, deterioration of the material with age their changesin the occupancy category
may place the building in a vulnerable category introducing significant
structural deficiency.
During an earthquake
the ground and the structure shakes violently. This back-and-forth motion can
cause a building to fall off its foundation, resulting in major damage to
the structure and
sometimes even total collapse. Seismic retrofit is not rocket science, and the
basic principles are easily understood. One can quickly learn all that is
needed to make informed decisions regarding the retrofitting of one's own
home. Retrofittingfocuses on strengthening the house-to- foundation connections
using specially designed hardware and engineered construction methods. Retrofitting allows a
house to withstand much greater earthquake forces with much less structural
damage.
Since disasters and
the forces generated by them are unpredictable, retrofitting cannot guarantee
that a house will receive no damage at all. However, it has been proven that
retrofitting greatly reduces the amount of damage a house receives and is
highly effective in preventing catastrophic collapse and loss of life. While retrofitting the
building is provided with additional strength, stiffness and ductility to
ensure acceptable performance during future disasters. Modem building codes
have been written so that newer homes usually don't need to be seismically reinforced if
they are properly constructed. However, builders sometimes do not
understand provisions of
the code that are specific to detailing reinforcement and
neglect to follow these aspects of the building code. A proper evaluation will
reveal if a building needs retrofit, regardless of whether it is new or old.
Walls and columns are the most critical elements during disasters.
Thousands of structures in metropolitan areas in India need assessment and
retrofitting if loss of life is to be minimized during disasters. The concepts
of assessment and retrofitting are well known and will enable both life
safety and reduction in loss of property damage. The cost
of retrofitting will not be prohibitive, because only existing weaknesses in
building that are identified during building that are identified during
evaluation are rectified during retrofitting.
Architects do not
design retro- fits; this is something done by j structural or civil
engineers. As in other fields, engineers tend to special ize, so if you choose
to work with an engineer, be sure he is one with special training in retrofit design. Contractors, I who
have had special training in retrofit engineering principles, can take up
installation. Seismic retrofittechnology is continually evolving, and a retrofit contractor
needs to understand and follow the most current seismic retrofit standards.
It is also important that he teams up with a structural engineer. A retrofit
generally costs between 5 percent and 10 per cent of a home's value. For many
home owners the one-time cost of a retrofit equals a few years of earthquake
insurance. And insurance won't prevent or reduce damage to your home, but
retrofitting will.
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