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WEAK BEAM DESIGN : The beams in the buildings can be made weak by
reinforcing correct amount of steel in them.
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BUILDINGS SHOULD be
designed like the ductile chain. For example, consider the common urban
residential apartment construction — the multi-storey building made of
reinforced concrete (RC).
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It consists of
horizontal and vertical members, namely beams and columns. The seismic
inertia forces generated at its floor levels are transferred through the
various beams and columns to the ground.
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The correct building
components need to be made very ductile. The failure of a column can
affect the stability of the whole building, but the failure of a beam
causes localised effect.
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Therefore, it is better
to make beams the ductile weak links than columns. This method of
designing RC buildings is called the strong-column weak-beam design
method.
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By using the routine
design codes (meant for design against non-earthquake effects), the
designers may not be able to achieve a ductile structure.
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Special design
provisions are required to help designers improve the ductility of the
structure. Such provisions are usually put together in the form of a
special seismic design code, e.g., IS:13920-1993 for RC structures. These
codes also ensure that adequate ductility is provided in the members where
damage is expected.
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The capacity design
concept in earthquake-resistant design of buildings will fail if the
strengths of the brittle links fall below their minimum assured values.
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The strength of brittle
construction materials, like masonry and concrete, is highly sensitive to
the quality of construction materials, workmanship, supervision, and
construction methods.
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Similarly, special care
is needed in construction to ensure that the elements meant to be ductile
are indeed provided with features that give adequate ductility.
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Thus, strict adherence
to prescribed standards of construction materials and construction
processes is essential in assuring an earthquake-resistant building.
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Regular testing of
construction materials at qualified laboratories (at site or away),
periodic training of workmen at professional training houses, and on-site
evaluation of the technical work are elements of good quality control.
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Sponsored by Building
Material & Technology Promotion Council, New Delhi
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