retrofitting of buildingppt

8/13/2019 Retrofitting of BuildingPPT

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240 million houses stock according to 2000 census

85 90 % houses are masonry houses

Stone masonry, Block masonry, Brick masonry

No standardized procedure/ no code

Differs from structure to structure

Depends upon seismic zone

Structural Engineering expert

Structural drawings/ soil data


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Houses not designed to resist earthquakes

People don't know what to do ?

Whether their houses are earthquake safe ?

How strong they are ?

How to make them earthquake safe ?Buildings can be upgraded by minor interventions Seismic Retrofitting

What level of Seismic Retrofitting ?


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Earthquake intensity

Structural configuration and components

Structural condition

Geological condition

Foundation capability

Non-structural components


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Difficulty in estimating the earthquakeparameters, intensity.

Influence of site condition microzonation.

Difficulty in estimation of insitu strength of

materials.

Analytical methods are either unreliable or toocomplex.


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Before the retrofitting to identify the deficiency

After the retrofitting to estimate the adequacyand effectiveness


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Detailed layout (plan and elevation)

Detail of foundation and soil

Structural drawings

Detail of codes used/ design calculations

Vulnerability assessment

If found deficient -retrofitting is done


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Natural frequencies of vibration of the structure

Frequency content of ground motion

Type of local soil and type of foundation

Strength of building material used

Care taken in its detailing for energy absorption

Care taken in construction


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Damage on masonry buildings start from corner separation


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Number of unsafe buildings is alarming

Non-engineered buildings

Faulty original design lack of lateral resistingelements: frames, shear wallsChanges in Codal practicesInadequate detailing of reinforcement

Extensions, Alterations and EncroachmentIncrease in load due to usagePoor and deficient constructionLack of regular maintenance

Degradation of building material/ Corrosion


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Integral box action

Integrity of various components Roof to wall

Wall to wall at corners

Wall to foundation

Limit on openings


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Integral box action

Integrity of various components Roof to wall

Wall to wall at corners

Wall to foundation

Limit on openings


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Many buildings with soft storey collapsed due tofailure of columns at joints in soft storey

The failure occurred due toLack of strength &stiffness of soft storey

strong beam-weak column behaviour of momentresisting frame

lack of ductility due to poor detailing


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Soft storey

Floating columns

In-plane and out-of-plane irregularity

Asymmetric configuration


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Strengthening ExistingMembersReinforcedConcrete Jacketing, Overlay &UnderlaySteel Plate Bonding and Jacketing, Steelsection caging; FRP Plate Bonding and Jacketing

Adding New MembersShearwallsFramesBracingsButtresses


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Conventional cast-in-place concrete

High-strength concrete using shrinkage

compensating admixture

Ferro-cementShotcrete (gunite)

Polymer concrete


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ResinsResin concreteGroutsGluing metal sheets on concreteWelding of new reinforcement

Gluing fibre-reinforced plastic (FRP) sheets onconcreteComposite reinforcing bars


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Fibre reinforced composite

Latest technique in structural rhabilitation

ACS comprises of uni-directional or bi-directional

woven reinforcing fabric saturated with speciallyformulated epoxy matrix


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Quick and easy application procedure results in timeand cost saving

Flexibility of application makes it suitable forapplication on member with any shape or profile

Causes no destruction or disturbance to existing

concreteIt can be used in space constrained areas

No heavy machinery or equipment is required


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It is light weight and easy to install causing nodistress to the member being strengthened

It increases the strength and ductility; enhancesaxial, shear, flexural and tensile capacities

No appreciable increase in member size or deadload

It does not corrode and inhibits further corrosion


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Increasing the size of ground storey columns by jacketing

Addition of RC walls at ground floor

Steel bracings at ground storey

Use of energy dissipating devices such as yieldingbracing or viscous dampers


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Option 1:

Detailed non-linear dynamic analysis to

ensure the deflection of the groundstorey columns to be within safe limits

Option 2: Increased lateral stiffness of the groundstorey to avoid soft storey effect


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The size of the ground storey beams and columns is increased to have the stiffness of theground storey comparable with upper storeys


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The ground storey should be provided with shear walls to increase the stiffness at groundstorey


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THE RESPONSE OF THE STRUCTURE IS

MODIFIED TO REDUCE THE EARTHQUAKEFORCES AND DISPLACEMENTS

STRATEGIES ARE:

1. REDUCTION OF MASS2. BASE ISOLATION3. ENERGY DISSIPATION


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Generally required for large masonry buildings, excavationsare made around the foundations of the building and thebuilding (in piecemeal fashion) is separated from the

foundationsSteel or reinforced concrete beams replace the connectionsto the foundations, while under these, layered rubber andmetal isolating pads replace the material removed, these inturn are attached below to new or existing foundations.

These allow the ground to move while the building,restrained by its inertial mass, remains relatively static.


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Lead rubber bearing


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Directly Increases The Structure DampingLarge relative displacements are required foreffective damping.

More effective in frame structures with large

window openings, than in shear wall buildings.

Sometimes braced frames are required formounting.


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Large Number Seismically Deficient Buildings -QuickAssessment Method

Upgradationof existing buildings is huge job andshould be taken up on buildings importance basis

Government alone cannot do it

Techniques of retrofitting and strengthening shouldbe applied

Techo-financing -tax exemption incentives


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Thank You for your patient hearing

retrofitting of buildingppt

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