REHABILITATION AND RETROFITTING

K.V.DASTHA GIRI14761A0123CIVIL DEPARTMENT

1

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

http://haitiearthquake.web.unc.edu/

4

SUMATRA E/Q, 26.12.2004DEATHS;2,27,898MAG. 9.1

http://indonesiabackpacker.com/sumatra-earthquakes/

5

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

6

NEPAL EARTHQUAKE2015, Magnitude: 7.9, deaths over 5000

http://www.ibtimes.co.uk/nepal-earthquake-you-cant-rule-out-more-earthquakes-come-1500883

7

AFGHANISTAN EARTHQUAKE26th October, 2015

www.slate.com/blogs/the_slatest/2015/10/26/afghanistan_and_pakistan_earthquake_is_deadly.html

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 IMMEDIATELY ABOVE OR LESS THAN 80% OF THE COMBINED STIFFNESS OF THREE STOREYS ABOVE)

8

• 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

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

• 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

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 ACTION12

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

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

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 WALLSON BOTH THE FACESABOVE LINTEL

17

18

AROUND OPENINGS

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

AT EXTERNAL CORNERS

21

VERTICAL REINFORCEMENT AT INSIDE CORNER

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

THANK U