about retrofitting and rehabilitation

1. REHABILITATION
AND RETROFITTING
K.V.DASTHA GIRI
14761A0123
CIVIL DEPARTMENT
1

2. EARTHQUAKES
• EARTHQUAKES DO NOT KILL BUT IT IS THE BUILDINGS WHICH
KILL
• NEARLY 5,00,000 EARTHQUAKES OCCUR EVERY YEAR
• ABOUT 1,00,000 ARE FELT
• Minor earthquakes occur nearly constantly around the world in places like
California and Alaska in the U.S., as well as in Mexico, Guatemala, Chile,
Peru, Indonesia, Iran, China, Pakistan, Portugal, Turkey, New Zealand,
Greece, Italy, India and Japan, but earthquakes can occur almost
anywhere.
• CASUALTIES
• LARGE NUMBER OF CASUALTIES OCCUR IN
DEVEOPING COUNTRIES. REASONS MAY BE;
– INADEQUATE DESIGN
– POOR CONSTRUCTION AND MAINTENANCE
– LACK OF RESOURCES
– INADEQUATE KNOWLEDGE
– INADEQUATE AWARENESS
– INADEQUATE TRAINING
– INADEQUATE SAFETY IMPLEMENTATION
2

3. HAITI’S E/Q, 12.1.2010; DEATHS-3,16,000; MAGNITUDE:7
3
http://haitiearthquake.web.unc.edu/

4. SUMATRA E/Q, 26.12.2004
DEATHS;2,27,898
MAG. 9.1
4http://indonesiabackpacker.com/sumatra-earthquakes/

5. TANGSHAN, CHINA, 27.7.1976;
DEATHS-242,769; MAG. 7.5
5

6. NEPAL EARTHQUAKE
6
2015, Magnitude: 7.9, deaths over 5000
http://www.ibtimes.co.uk/nepal-earthquake-you-cant-
rule-out-more-earthquakes-come-1500883

7. AFGHANISTAN EARTHQUAKE
7
26th October, 2015
www.slate.com/blogs/the_slatest/2015/10/26/afghanistan_and_pakistan
_earthquake_is_deadly.html

8. 8
CAUSES OF FAILURE OF MASONRY
BUILDINGS
 POOR QUALITY OF MORTAR
 IRREGULARITY IN PLANE AND VERTICAL DIRECTION
 NO PROVISION OF BANDS
 NO THOROUGH STONES
 HEAVY MASS CONCENTRATION AT ROOF LEVEL
 UNSYMMETRICAL BUILDINGS AND FULL OPENINGS
 UNCONFINED WALL CORNERS
 INADEQUATELY DESIGNED CANTILEVER ELEMENTS
 CAUSES OF FAILURE OF RCC
BUILDINGS
 SOFT STOREY (ONE IN WHICH LATERAL STIFFNESS IS LESS
THAN 70% OF THAT IN THE STOREY IMMEDIATELYABOVE OR
LESS THAN 80% OF THE COMBINED STIFFNESS OF THREE
STOREYS ABOVE)
8

9. • INADEQUATE FOUNDATION
• POUNDING OF BUILDINGS
• INADEQUATE DESIGN AND DETAILING
• INADEQUATE CONNECTVITY LIKE ISOLATED STAIRCASES
AND WATER TANKS NOT PROPERLY ANCHORED
• POOR DETAILING OF BEAM COLUMN JUNCTIONS
• PROVISION OF FLOATING COLUMNS
• PLAN AND MASS IRREGULARITY
• NORMALLY STRUCTURES REQUIRING
REPAIR AND REHABILITATION ARE MORE
SUSCEPTIBLE TO DAMAGE, HENCE
REPAIR AND REHABILITATION IS VERY
IMPORTANT
9

10. CAUSES OF DETERIORATION OF RCC
• PENETRATION OF WATER/CHEMICALS LEADING TO
CARBONATION, CHLORIDE INGRESS, LEACHING, SULPHATE
ATTACK, ALKALI SILICA REACTION ETC LEADING TO
CORROSION IN THE REINFORCEMENT
MAIN REASON OF PENETRATION OF WATER
• POROSITY OF CONCRETE
• PRECAUTIONS TAKEN TO PREVENT POROSITY
• ADEQUATE STRENGTH OF CONCRETE
• PROPER COMPACTION
• WATER PROOFING ON ROOF
• PLASTER ON CONCRETE
• WATER PROOFING PAINTS ON EXPOSED PLASTERED SURFACE
• CAUSE OF DETERIORATION OF
CONCRETE
10

11. • AGING OF STRUCTURE
• POOR QUALITY
– POOR QUALITY OF TESTING/INVESTIGATION
– POOR QUALITY OF DESIGN
– POOR QUALITY OF EXECUTION IN TERMS OF
MATERIALS/COMPACTION/PAINTS/COVER/RCC
– POOR QUALITY OF MAINTENANCE
• SELECTION OF MATERIALS FOR
REHABILITATION/ RETROFITTING
• TECHNICAL REQUIREMENTS
• COST
• AVAILABILITY
• EXPERT’S ADVICE
• IMPORTANCE OF THE STRUCTURE
• BALANCE LIFE OF THE STRUCTURE
• TOXICITY OF THE MATERIAL
• AESTHETIC CONSIDERATION
11

12. REHABILITATION METHODS
• SAND BLASTING FOR REMOVAL OF CORROSION
• BINDING/ADDING OF ADDITIONAL REINFORCEMENT
• WELDING
• ANCHORING TO THE EXISTING MEMBERS THROUGH SHEAR
KEYS OR ANCHORS
• SHOTCRETING
• PLATE BONDING
• JACKETING
• FIBRE WRAPPING
• UNDERPINNING
PROCEDURE
• REMOVAL OF LOOSE MATERIALS/RUST
• PROVIDING PROTECTIVE LAYER/COATING
• PROVIDING BONDING COAT BETWEEN OLD AND NEW
MATERIAL/SURFACES
• PROVIDING STEEL MEMBERS/WELDING/ANCHORS/
SHEAR KEYS TO ENSURE MONOLITHIC ACTION
12

13. RETROFITTING
• PLATE BONDING
• FIBRE WRAP TECHNIQUES THROUGH GLASS FIBRES/CARBON
FIBRES
• RCC JACKETING
CAUSES OF FAILURE OF MASONRY BUILDINGS
• POOR QUALITY OF MORTAR
• IRREGULARITY IN PLANE AND VERTICAL DIRECTION
• NO PROVISION OF BANDS
• NO THOROUGH STONES
• SEISMIC STRENGTHENING/ RETROFITTING
• SEISMIC STRENGTHENING
• MAIN PURPOSE OF SEISMIC STRENGTHEING IS TO
UPGRADE/PROVIDE THE SEISMIC RESISTANCE ON A BUILDING
SO THAT IT BECOMES SAFER UNDER EARTHQUAKE
OCCURANCES 13

14. SELECTION OF MATERIALS AND
TECHNIQUES FOR RETROFITTING
 CEMENT
 STEEL
◦ BOLTS, RODS, ANGLES, BEAMS, CHANNELS, EXPANDED
METAL, WELDED WIRE FABRIC
 ADMIXTURES TO IMPROVE NON-SHRINKAGE (GROUTS
CONSISING POLYMER, NON-SHRINK CEMENT AND SPECIAL
SANDS), BOND (EPOXY RESINS) ETC.
SEQUENCE OF RETROFITTING
 REPAIR/REHABILITATION
 ALL CRACKS SHOULD BE FULLY REPAIRED
◦ PRESSURE INJECTION OF NON-SHRINK CEMENT
POLYMER GROUT FOR 0.5 TO 5 MM CRACKS
◦ REPAIR BY EXPANSIVE CEMENT MORTAR, QUICK
SETTING CEMENT, ADDL. SHEAR OR FLEXURAL
REINFORCEMENT, STEEL MESH, STEEL RODS 14

15. REPAIR/STRENGTHENING OF WALLS
 BY GROUTING (CEMENT WATER MIXTURE OR POLYMERIC
MORTAR)
 BY ADDITION OF VERTICAL REINFORCEMENT CONCRETE
COVERINGS ON THE TWO SIDES OF THE WALL
 BY PRESTRESSING WALL
HORIZONTAL SEISMIC BELTS
◦ IN CASE OF RCC SLAB ROOF BELT NOT REQUIRED
◦ NOT REQUIRED AT PLINTH LEVEL UNLESS PLINTH HEIGHT IS
MORE THAN 900 MM
◦ ON ALL WALLS
◦ ON BOTH THE FACES
15

16. ON ALL WALLS
ON BOTH THE FACES
ABOVELINTEL
16

17. 17

18. AROUND OPENINGS
18

19. VERTICAL SEISMIC BELTS AT CORNERS
 AT THE CORNERS OF ROOMS
 JUNCTIONS OF THE WALLS
 WIDTH ON EACH SIDE OF THE CORNER TO BE KEPT 25 MM
EXTRA TO THE WIDTH OF THE MESH
 REIFORCEMENT TO BE STARTED BELOW 300 MM BELOW
PLINTH LEVEL
19

20. 20
AT EXTERNAL CORNERS

21. VERTICAL REINFORCEMENT
AT INSIDE CORNER
21

22. ROOFS CONSISTING OF STEEL JOISTS FLAT OR SEGMENTAL
ARCHES MUST HAVE HORIZONTAL TIES HOLDING THE JOISTS
HORIZONTALLY IN EACH ARCH SPAN SO AS TO PREVENT
SPREADING OF JOISTS
22