diagnostic approach towards structural repairs

7/30/2019 Diagnostic Approach Towards Structural Repairs

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Diagnost ics approach

towards

St ructu ral repairs


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Typical issues in RCC structures

- Corrosion

- Cracking- Spalling of concre te

- Leakage / seepage

- Bulging of concre te

- Deflection of structural m em bers, etc.,


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CRACKS indicate the beginning ofdeterioration in most cases


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LEAKAGE

Can be very ugly and dangerous


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SPALLING

Result of neglected leakage & cracks for long time


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Factors that lead to Problems

Built in problems (I nternal)

External Causes

Man made causes

Natural calamities


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I nternal Cause

Design issues

Improper selection of materials

Wrong waterproofing specifications

Faulty construction methods


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External Cause

Environmental attack

Chlorides

Carbon dioxide

Sulphates

Humidity


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Man made causes Change in use of structures

Over loading

Unplanned modifications /alterations

Poor maintenance


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Natural calamities

Earthquake

Flood

Fire

Cyclones


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Typical Causes:Corr osion of reba r

- Chemically active soil

- Pollution

- I ndustrial abuse(chemicals)

- High relative hum idity

- Environmental attack

Chlor ide & Co2

induced


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Cracks due tocorrosion

A major problem

Protection reduced

Concrete becomes porous

Entry of CO2 &

Chlorides & moisture


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Co2 induced corrosion


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Chloride induced corrosion


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Approach to syste m at ic repairs

I nspection most important activity

must be done by a professional

- Every structure requires different approach.

E.g. building structure, industrial str, jetty,

cooling towers, intake pump houses, dams,

bridges, etc.,

- All locations of distress should be noted

- Original drawings, if available, should bereferred


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Approach to syste m at ic repairs

Cause and nee d ident ificat ion:

-W hat is m ain cause?

-W hy repairs?

-W hat is the l ife expectancy?

-W hat is the importance of structure?

-I s the need only to patch repairs? Or any

other


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Unless the cause is ident ified and

rem oved, repa irs can not be

effective & com plete.


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NEED??

- Life ext ension

- Strengthening

- I ncrease in loads

- Seismic

- Restorat ion t o

original design

values

- Protection


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Diagnosis:

( Visual inspection + Diagnosis)

Comparison

Structural engineer = Doctor

Pat hological tests = NDT


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Diagnosis:ND Ts are e ffective tools to

determ ine the hea lth of concrete

TO ASSESS PERFORMANCETO ASSESS PERFORMANCE

LEVEL DURING SERVICELEVEL DURING SERVICE

LIFELIFE


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PARAMETERS TO BE EVALUATEDPARAMETERS TO BE EVALUATED

a) STRENGTH ( I N -SI TU)b) DURABI LI TY PERFORMANCE

presence of internal voids/ cracks,materials likely to cause disruption ofconcrete (sulphate or alkali reactiveaggregates), extent or risk of reinf.corrosion, chloride content, cover

thickness, permeability etc.


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NDT:Com m on NDTs are

1 . Rebound ham m er test

2 . USPV

3 . Half cell potent ial met er

4 . Rebar locator

5 . Core te st

6 . Thickness test

7 . Carbonation test

8 . Chem ical a nalysis

diagnostic approach towards structural repairs

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