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EARTHQUAKE RESISTANT
DESIGN
Presented by
U.Vetrivel
Arunai College Of Engineering
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INTRODUCTIONEarthquake is the worst of all natural disasters.
The various techniques be adapted to make the buildingsmore resistant.
Due to shaking of the ground , base of the building will
experience motion & tendency of roof is to stay in itsoriginal position due to inertia force.
Due to wall and column connection, the force will drag theroof along with them.
So its tendency is to attack from the base and at beamcolumn joint and protrude through structure.
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GENERAL DESIGN PHENOMENON
Beam Column Effect
For higher zones strong column and weak beam arebetter.
Beam damage will cause localized effect whereas the column
damages it leads to entire structural damage.
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Joint displacement due to seismic waves Column Failure
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Inverse PendulumEffect
The parking area do not haveany partition walls
It is too weak to carryearthquake force
Design Phenomenon
Stiff masonry walls areavoided and bare frames areconsidered in design calculations.
Steel sections will be raised asvertical reinforcement and hollowblocks as partitions hence the
inverted pendulum effect is notcaptured4
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Beams as a Structural Member Beams are the horizontal members in a structure.
It has two types of failure.flexural failure
Shear Failure
Column as a structural member:
Columns, the vertical members in RC buildings, contain two types ofsteel reinforcements.
Long straight bars placed vertically along the length to sustain axialforce and transverse ties placed horizontally at regular intervalsalong its full length.
Columns can sustain two types of Damage
axial-flexural Failure
shear failure.
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Horizontal Bands and its Role
It holds a masonry building as a Single unit by tying all the wallstogether.
There are four types of bands in a typical Masonry building,namely
1. gable band -employed in pitched or sloped roofs.2.roof band, not required R.C or reinforced brick roofs ,
but used in pitched or sloped roof.
3.lintel band -since it ties the walls together and alsobreaks the monotonous continuity of wall.
4.plinth band- Used in uneven settlement of foundation insoil .
It will be better to use RC bands 6
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Shear Wall
vertical plate-like RC walls called ShearWalls.
Their thickness varies from 150mm to 400mm.
Shear walls are like vertically-oriented wide beams that carry
earthquake loads downwards to the foundation.
It provide around the elevator core or stair well is known as
shear core.
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Edges ofshear walls experience highcompressive and tensile stresses due to
overturning effect.
To ensure that shear walls behave in a
ductile way, concrete in the wall end regions
must be reinforced in a special manner tosustain these load reversals without loosing
strength
End regions of a wall with increased
confinement are called boundary elements
which have high bending strength.
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Short Column Behavior:
Shorter columns suffered moredamage as compared to tallercolumn.
Because of same cross-section
move horizontally
the short column is stiffer,itattracts larger earthquake forceand X-shaped cracks.
Stiffness of a column meansresistance to deformation
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Design Phenomenon:
this effect must be addressed in structural design
the reinforcement must extend beyond the short column into thecolumns vertically above.
the width has to be increased in stone or brick masonry.
Beam Column Joint
more strength is not expected when both materials are same.
have to take care on these unavoidable joints.
During earthquake the upper bars and lower bars act in a different
direction causing elongation or damage of joint. 11
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Design Strategy
In design practice large column size,having large closed loops are placed
inside.
The anchoring of the bars at the endsand Micro concreting in the congestedjunction.
Hidden Beams
They are concealed beams havingtheir depth equal to that of the slab
The load carrying capacity increase to135% with an economical increase ofjust 0.40.5%.
These beams are designed for negativebending moment
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Plastic Hinge
As moment increases, the linear stress distribution formpersists
The extreme fiber stress reaches the yield stress value.
Further increase in the bending moment cannot produce anyincreased fiber-stress and
Finally fibers reach the yield stress the section will yield and
the complete yielding is termed as plastic hinge.
The section now carries the maximum bending momentwithout strain hardening taking place.
The beam will behave as if it is hinged at the plastic section 13
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Reduced Beam Section
This is provided along the length of steel beams.
their area ofcross section lesser than the proceeding section that it willact as a plastic hinge.
In case of steel section also a circular arc will be cut in the requiredflange portion of span.
Reduced Beam Section
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The lateral thrust will be more in domes and shells.
We will be having a thin walled cylindrical tube of diameter about 10to 15 cm and steel rods
Then stressing will be done as per design and then the micro concreteis injected in pressure into the tube.
Techniques to Adopt on Sky Scrappers
In large multistoried buildings provide as Bearing, Bracing, Frictionpendulum and Dampers instead ofbeams, columns, and otherstructural elements to take Vibration produced by lateral force.
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Pre tensioning Technique
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Rubber Bearings
Rubber bearing are made from layers of rubber, a thicksteel plate between the thin steel plates .
Placed between the bottom of a building and its foundation.
The bearings to be strong for vertical load
Weakerfor horizontal loads, so that they can move sidewaysdue to lateral thrust.
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Viscous Dampers
It is shock absorbers.
Containing closed cylinderwith viscous fluid and apiston.
As the piston move in andout of the cylinder oil isforced in and out causingfriction cause buildingsway.
The damper is usuallyinstalled as part of abuilding's bracing system.
Friction Dampers
They are designed tohave moving partswhich slide over eachother.
The damper is made
up from a set of steelplates.
At forces,the platescan slidecreatingfriction causing energy
dissipation.
The plates are speciallytreated to increase thefriction between them.
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Cross Bracings
It is common vertical load distribution.
But we can also adopt this technique tofoundation
It will distribute the load to joints andthrough foundation finally.
Friction Pendulum:
In large multistory buildings, we canalways expect some appreciablemovement in it base due to the vibration
. to resist completely we can allow thestructure to deform at its foundation levelby provision of friction pendulum
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CONCLUSION
Constraint is that, human has to satisfy his unlimited wantsthrough limited resources.
As a part of the civil engineering world, we all have a role to
play in developing newer and more effective techniques toincrease the seismic resistance of buildings to make theminvulnerable to an appreciable intensity of earthquakes
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Reference
MCEER Information Service
IS 1893 2002 CRITERIA FOR EARTHQUAKE
RESISTANCE DEGIN OF STRUCTURES
EARTHQUAKE RESISTANCE TIPS
IITK- bmptc
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THANK U
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