3.earthquake resistant

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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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3.earthquake resistant

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