retrofitting of fire damaged rcc slabs,colums,beams retrofitting and rehabilitation

1. retrofitting of existing rcc members Different
strengthening techniques

2. introduction
• Increasing resistant capacity of structure by various techniques.
• Prominent structural elements: Beams, Columns and slab.
• Deformation in elements.
• Restoring strength to its original condition.
• Release of stress on members.
• Seismic strengthening.

3. Problems faced in rcc structures
• Damage to structural members.
• Excessive loading.
• Errors in design or construction.
• Modification of structural system.
• Seismic damage.
• Structural cracks.
• Corrosion due to penetration- honey combs.

4. Retrofitting or reconstruction?
• Economical consideration.
• Immediate solution.
• Improved serviceability.
• Making buildings more suitable for intended use.
• More energy efficient - lowering related carbon emissions.
• Loads may be immediately applied, no cure time.
• Enhancement of strength to increase durability.

5. Factors influencing selection
• Cost of Construction and maintenance.
• Environmental aspects.
• Clearance issues.
• Magnitude of strength to be enhanced.
• Time constraints.
• Existing concrete strength.
• Seismic effect consideration
• Accessibility to work areas.

6. Factors influencing selection
• Cost of Construction and maintenance.
• Environmental aspects.
• Clearance issues.
• Magnitude of strength to be enhanced.
• Time constraints.
• Existing concrete strength.
• Seismic effect consideration
• Accessibility to work areas.

7. Retrofitting techniques
• Conventional techniques
o Section enlargement.
o External plate bonding.
o External post tensioning.
o Ferro cement covering.
o Grouting.
• Advanced strengthening techniques
o Fiber Reinforced polymer(FRP) composites.

8. Section enlargement (RCC JACKETING)
• Entire cross section of member is increased.
• Additional structural reinforcement steel with shear stirrups.
• Process involves surface preparation, additional
reinforcement and concrete curing.
Advantages
• Enhanced strength.
• Increased shear capacity of columns.
• Technique is easy and it does not need special design
criteria.

9. Contd.
Disadvantages
• Increase in member cross section- less floor area.
• Increase dead weight due to extra steel and concrete.
• Prone to high level of corrosion.
• Requires more construction time as it involves curing.
• Production of dust and debris causes pollution and health
hazards.
• Needs shuttering, formworks, reinforced steel, concrete,
concrete pumps, vibrators, etc..,

10. External plate bonding
• Steel plates are attached to the surface of damaged members
forming a three phase steel composite system
• Acts as supplement to existing reinforcement.
Attachment of steel to concrete
o Adhesive connecting mechanism (glue).
o Bolting connecting mechanism.
Advantages
• Stress reduction due to the external steel plate.
• Enhances load bearing capacity.
• decreases chances of cracks and deflection.

11. Contd.
Disadvantages
• Increase in dead load.
• High installation cost due to heavy weight of steel plate.
• If there is any indications of corrosion in the reinforcement
this technique cannot be used.
• Susceptible to high level of premature de-bonding.
• Chances of corrosion is high.
• Bonding between concrete and steel plate.
• Reaction between epoxy adhesive and concrete.

12. EXTERNAL POST TENSIONING.
• High strength steel strands or pre-stressing tendons are used.
• Tendons are pulled and connected to anchor points on member.
• Very much suitable for retrofitting of bridges.
Advantages
• Ability to restress, destress and exchange any external pre-
stressing cable.
• Crack free members.
• Reduce deflection.
• High fatigue and impact resistance.
• Immediate enhancing of load bearing capacity.

13. Contd.
Disadvantages
• Usually requires a greater section depth.
• Exposed to environmental influences.
• Handling of the tensioning devices may be
more difficult.
• High cost.
• Prone to corrosion.
• Skilled person is needed for post tensioning

14. Ferro cement covering
• composite material reinforced with wire mesh and cement mortar
modified with chemicals or polymers with closely spaced layer.
• Process involves surface preparation, orientation of wire mesh
and Ferro concrete finishing.
Advantages
• Enhanced resistance to cracking
• Capacity to carry heavy loads.
• High flexural stiffness compared to ordinary cement.
• Resistance to penetration of water.
• Provide resistance to fire, corrosion and earthquake.

15. Contd.
Disadvantages
• Number of labor will be higher.
• Rust can be developed on reinforcement if not covered
properly by mortar.
• It is hard to do welding, screw, nut etc.., properly.
• Binding rod and mesh along can be time consuming.
• Proper curing is required.
• Increases dead weight.

16. Retrofit by grouting
• Easiest process which involves placing of cementitious material
in to the cracks created from excessive loading in concrete
member.
• Pressure grouting is generally used.
• It is commonly used when honey combs are observed.
• Prevents reinforcement from corroding.
• Very low or no strength gained.
• After grouting proper curing has to be done but often it is
neglected.
• Not effective as other techniques.

17. Advanced strengthening technique
FIBER REINFORCED POLYMER
• Composite materials: polymer that is reinforced with fiber.
• Fiber reinforcement is to carry load along the length of the fiber, provide strength and
stiffness.
• Flat layer contains an arrangement of unidirectional fibers fabrics embedded within a thin
layer of light polymer matrix material.
• Fibers usually use,
o RESINS= EPOXY/ POLYSTER/VINYLESTER.
o REINFORCEMENT(FIBRES)= CARBON/ GLASS/ ARAMID.

18. Composition of frp
EPOXYPOLYSTER VINYLESTER
RESINS
FIBRES
CARBONGLASS ARAMID

19. Carbon fiber reinforced polymer
Type of composite material in which carbon constitutes the
fiber phase.
• High performance fiber polymer.
• It contains 93 to 95% of carbon.
• Each fiber is 5 to 10 microns in diameter.
• Twice as stiff as steel and five times as strong as steel.
• It is used to make aircrafts, spacecraft parts, racing car
bodies, bicycle frames etc.,

20. Properties of Carbon frp
• High tensile strength.
• CFRP is alkali resistant.
• Light weight.
• Corrosion resistant and chemically stable, hence best suitable for rehabilitation.
• High strength to weight ratio.
• Very low thermal conductivity.
• High ultimate strain, thus suitable to earthquake resistant application.
• Electrically, thermal resistance and is non magnetic.
• Fire resistant/ non flammable.
• High abrasion and wear resistance.

21. Use of CFRP in structural strengthening
CFRP STRIPS
• Performance of CRPF strips depend on the strength of adhesive used to bond the
strips to the concrete surface.
• Strong, ductile and durable structural system can be achieved.
• These are four times stronger than structural steel.
CFRP WRAPS
• Mainly used for corrosion control and retrofitting of rcc members.
• resistance to collapse under earthquake loading
• In a circular column an increase in axial capacity is also achieved by wrapping.
• the confinement of the CFRP wrap enhances the compressive strength of the
concrete and increase in load bearing strength.
• Immediate strength gain and open to traffic.

22. procedure

23. Why this technique?

24. Carbon fiber reinforced polymer
Disadvantages
• High initial cost.
• Lack of knowledge: absence of codes.
• Should be protected from UV radiation.
• Use od resins: problems with de-bonding.
• Composites must be dried before repair because all resin matrices and some
fibers absorb moisture.

25. conclusion
• CFRP are thin, strong, flexible, corrosion resistant and light weight. These properties makes
this technique suitable for all purpose compared to other conventional technique.
• High stiffness, high tensile strength, high chemical resistance, high temperature resistant and
fire resistant made CFRP one of the most popular material in retrofitting of RCC members.
• It possess strength up to five times that of steel being one third of its weight.
• Ease in process, less time consuming and increased resistance to deformation.

26. references
• Traditional solutions for strengthening reinforced concrete slabs by dragoş banu and n.
ţăranu
• Decision selection technic for building strengthening methods a. okakpu1 and g.
ozay2,department of civil engineering, eastern mediterranean university, famagusta, via
mersin10, turkey
• Influence of using cfrp on damaged columns repaired with two different materials abbas
s. al-ameeri 1* nisreen s. mohammed2 haider m. al-baghdadi 31(civil, engineering depart. /
university of babylon, babylon city, iraq,)
• Behaviour of reinforced concrete columns confined with cfrp (carbon fiber reinforced
polymer) c.k.rankoth

27. THANK YOU