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RETROFITTING MATERIALS

Yogendra Singh SinghDepartment of Earthquake EngineeringIndian Institute of Technology, Roorkeee

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NEED FOR RETROFITTINGSOURCES OF DEFICIENCY

NON-ENGINEERED BUILDINGS

SEISMIC FORCES NOT CONSIDERED IN DESIGN

ORIGINAL DESIGN AND DETAILING IS DEFICIENT

DEFICIENCIES IN CONSTRUCTION

CHANGES IN CODE OF PRACTICE

CHANGE IN USAGE OF BUILDING

DETERIORATION OF BUILDING MATERIAL CORROSION

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STEPS IN RETROFITTING

SETTING OF GOALS

VISUAL INSPECTION AND STUDY OF DRAWINGS, IF AVAILABLE

IN-SITU TESTING AND PREPARATION OF AS BUILT DRAWINGS

PRELIMINARY EVALUATION

DETAILED EVALUATION

RETROFIT DESIGN

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RETROFITTING GOALS

PERFORMANCE LEVEL DESIRED

COLLAPSE PREVENTION

LIFE SAFETY

IMMEDIATE OCCUPANCY

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MINIMUM INTERRUPTION TO OCCUPANTS

SATISFACTORY PERFORMANCE OVER TIME

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CHALLENGES IN RETROFITTING

AVAILABILITY OF DRAWINGS

IN-SITU ESTIMATION OF STRENGTH RELIABILITY AND ACCURACY OF

TESTING RESULTS

VARIABILITY IN STRENGTH AND OTHER PARAMETERS

EVALUATION TOOLS

RETROFIT DESIGN THEORY AND TOOLS

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RETROFITTING STRATEGIES

STARTEGY 1: STRENGTHENING OF STRUCTURE RETROFITTING IS USUALLY DONE BY ADDING

BRACED FRAMES, SHEAR WALLS, BUTTRESSES OR OTHER SIMILAR ELEMENTS

THIS WILL RESULT IN INCREASE OF STIFFNESS AS WELL AS STRENGTH

STARTEGY 2: REDUCING EARTHQUAKE DEMAND

ADDITION OF BASE ISOLATORS OR ENERGYDISSIPATION UNITS EDUs.

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Retrofitting Materials Grouts for repair of cracks, strengthening of

masonry and honeycombed concrete.

Bonding agents for enhanced bonding betweenold and new concrete, and concrete and reinforcement.

Replacement and jacketing materials for replacing the damaged portions, increasing thesize of members, enhancing the confinement and external reinforcement of the members.

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Injection Grouts Flowable plastic material

Injected under pressure

Negligible shrinkage

Stable without cracking & delemination

Useful for honeycombed concrete and thin cracks

Specially useful for historical structures

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Injection Grouts Cement-Sand Grout

High cement and sand content with a shrinkagecompensating admixture

Gas Forming GroutsAdded Al or C powder forming gas bubbles

Sulfo-aluminate groutsAnhydrous Sulfo-aluminate additive (6%-10%)

Fibre-Reinforced GroutsPropylene Fibres (4%-6%)Steel Fibres (2%-3%)Glass Fibres ( 2-4%)

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Injection Grouts Polymer Grouts

Long Chain HydrocarbonsPolyester, Vinyl ester, Epoxy, Polyurethane, Acrylic

Three Component Grouts for thicker cracks

Two Component Grots for thinner cracks

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Injection Grouts Apparatus

CEMENT-SAND INJECTION GROUT APPARATUS

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Injection Grouts Apparatus

HAND OPERATED MACHINE FOR EPOXY GROUTING

4/20/2010AUTOMATIC MACHINE FOR EPOXY GROUTING

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Injection Grouting Procedure Cleaning of crack with compressed air and

removal of loose material, if any.

Drilling of holes (5 to 10 mm) at several placesalong the length of the crack.

Placing of 'Ports' or 'Nipples' at the mouth of holes.If the cracks are wide and accessible from surface Tports can be installed.

On vertical surfaces, the injection is started from thelowest port till it comes out from the upper nipple.

The port is sealed and injection is started from the upper port. After hardening of the epoxy in a day or so, the sealing resin paste is removed.

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Fixing of Nipples

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Fixing of Nipples

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Replacement and Jacketing MaterialsORDINARY PORTLAND CEMENT CONCRETE Same appearance and thermal movement

Cheap and no special skill required

Shrinkage compensating agent

Higher strength ( at least 5 MPa) than existing concrete

High workability, super plasticizers

Smaller aggregate size

PREPLACED CONCRETE

DRY PACK

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Replacement and Jacketing MaterialsSHOTCRETE / GUNNITING Applied under pressure

Low water content

No frame work required

Can be applied on any surface

Low permeability & shrinkage

Special equipment is requiredDry Mix Type & Wet Mix Type

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Shotcrete Machine

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Replacement and Jacketing MaterialsPOLYMER MODIFIED CONCRETE Polymer latex

Redispersible powder

Better workability

Low permeability

High tensile and bending strength

Improved adhesion and bond with existing concrete

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Jacketing MaterialFIBRE REINFORCED POLYMERS (FRP)

1000-1800

40-1251050-1250

60-70Aramid/epoxy AFRP laminate

1200-2250

120-2501600-1900

65-75Carbon/epoxy CFRP laminate

400-1800

20-551600-2000

50-80Glass fibre/polyester GFRP laminate

Tensile strength (MPa)

E (Long.)(GPa)

Density (kg/m3)

Fibrecontent (% by

weight)Unidirectional

advanced composite materials

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Jacketing MaterialFIBRE REINFORCED POLYMERS (FRP)

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The surfaces are lightly ground to promote adhesion and to radius the corners

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After priming the areas to be repaired, adhesive putty is applied to fill any bug holes or surface irregulari-ties

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The pre-wetted Velacarbis carefully applied to the column and smoothed out.

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The upper layers are applied.

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The final check of the Velacarbfor air bubbles

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A finished and cured repair.

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Joint

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Effect of FRP Confinement

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Confinement of Beams

0

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0 0.05 0.1 0.15 0.2

Curvature (m-1)

M

o

m

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k

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Steel StirrupsConfined

GFRP SingleLayer Confined

GFRP TwoLayer Confined

GFRP ThreeLayer Confined

GFRP FourLayer Confined

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Confinement of Columns

-5000

0

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Moment (kNm)

A

x

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a

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F

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Steel StirrupsConfined

GFRP Single LayerConfined

GFRP Two LayerConfined

GFRP Three LayerConfined

GFRP Four LayerConfined

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Confinement of Columns

0

100

200

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400

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0 0.1 0.2 0.3Curvature (m-1)

M

o

m

e

n

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k

N

m

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Steel StirrupsConfined

GFRP SingleLayer Confined

GFRP TwoLayer Confined

GFRP ThreeLayer Confined

GFRP FourLayer Confined

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THANK YOU !