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REHABILITATION AND SEISMIC RETROFITTING DR. K.M. SONICHIEF ENGINEERWEST ZONE I, CPWD, MUMBAI

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EARTHQUAKESEARTHQUAKES DO NOT KILL BUT IT IS THE BUILDINGS WHICH KILLNEARLY 5,00,000 EARTHQUAKES OCCUR EVERY YEARABOUT 1,00,000 ARE FELTMinor 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.

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CASUALTIESLARGE NUMBER OF CASUALTIES OCCUR IN DEVEOPING COUNTRIES. REASONS MAY BE;INADEQUATE DESIGNPOOR CONSTRUCTION AND MAINTENANCELACK OF RESOURCESINADEQUATE KNOWLEDGEINADEQUATE AWARENESSINADEQUATE TRAININGINADEQUATE SAFETY IMPLEMENTATION

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HAITIS E/Q, 12.1.2010; DEATHS-3,16,000; MAGNITUDE:7 4http://haitiearthquake.web.unc.edu/

TANGSHAN, CHINA, 27.7.1976; DEATHS-242,769; MAG. 7.55

travel.smart-guide.net/wp-content/uploads/2010/11/The-Tangshan-Earthquake.jpg

SUMATRA E/Q, 26.12.2004DEATHS;2,27,898MAG. 9.16http://indonesiabackpacker.com/sumatra-earthquakes/

Haiyuan, chinae/q 16.12.1920Deaths; 2,00,000Mag. 7.87

http://forum.china.org.cn/redirect.php?tid=13090&goto=lastpost

Kanto, e/q, Japan; 1.9.1923Deaths-1,42,800Magnitude: 7.98

http://webra.cas.sc.edu/hvri/feature/sep2013_dom.aspx

Pakistan e/q, 18.10.2005Deaths; 86000Mag-7.69

www.golder.com/in/modules.php?name=Newsletters&op=viewarticle&sp_id=109&page_id=1100&article_id=65

Iran e/q, 20.6.1990Deaths-50,000Mag. 7.410https://www.emaze.com/@ATQLQCO/suhey-hernandez-.-Iran-Earthquake

Gujarat e/q, 26.1.2001Deaths-20,085, Mag. 7.611(en.wikipedia.org)

Latur, india e/q 29.3.1993Deaths 9748Mag. 6.212(www.indiatoday.intoday.in)

NEPAL EARTHQUAKE132015, Magnitude: 7.9, deaths over 5000

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

AFGHANISTAN EARTHQUAKE1426th October, 2015

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

15CAUSES OF FAILURE OF MASONRY BUILDINGSPOOR QUALITY OF MORTARIRREGULARITY IN PLANE AND VERTICAL DIRECTIONNO PROVISION OF BANDSNO THOROUGH STONESHEAVY MASS CONCENTRATION AT ROOF LEVELUNSYMMETRICAL BUILDINGS AND FULL OPENINGSUNCONFINED WALL CORNERSINADEQUATELY DESIGNED CANTILEVER ELEMENTS15

CAUSES OF FAILURE OF RCC BUILDINGSSOFT 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)POOR DETAILING OF BEAM COLUMN JUNCTIONSPROVISION OF FLOATING COLUMNSPLAN AND MASS IRREGULARITYINADEQUATE FOUNDATIONPOUNDING OF BUILDINGSINADEQUATE DESIGN AND DETAILINGINADEQUATE CONNECTVITY LIKE ISOLATED STAIRCASES AND WATER TANKS NOT PROPERLY ANCHORED16

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18NORMALLY STRUCTURES REQUIRING REPAIR AND REHABILITATION ARE MORE SUSCEPTIBLE TO DAMAGE, HENCE REPAIR AND REHABILITATION IS VERY IMPORTANT 18

CAUSES OF DETERIORATION OF RCCPENETRATION OF WATER/CHEMICALS LEADING TO CARBONATION, CHLORIDE INGRESS, LEACHING, SULPHATE ATTACK, ALKALI SILICA REACTION ETC LEADING TO CORROSION IN THE REINFORCEMENT 19

MAIN REASON OF PENETRATION OF WATER

POROSITY OF CONCRETE 20

PRECAUTIONS TAKEN TO PREVENT POROSITYADEQUATE STRENGTH OF CONCRETEPROPER COMPACTIONWATER PROOFING ON ROOFPLASTER ON CONCRETEWATER PROOFING PAINTS ON EXPOSED PLASTERED SURFACE21

CAUSE OF DETERIORATION OF CONCRETEAGING OF STRUCTUREPOOR QUALITYPOOR QUALITY OF TESTING/INVESTIGATIONPOOR QUALITY OF DESIGNPOOR QUALITY OF EXECUTION IN TERMS OF MATERIALS/COMPACTION/PAINTS/COVER/RCCPOOR QUALITY OF MAINTENANCE 22

SELECTION OF MATERIALS FOR REHABILITATION/ RETROFITTINGTECHNICAL REQUIREMENTSCOSTAVAILABILITYEXPERTS ADVICEIMPORTANCE OF THE STRUCTUREBALANCE LIFE OF THE STRUCTURETOXICITY OF THE MATERIALAESTHETIC CONSIDERATION23

REHABILITATION METHODSSAND BLASTING FOR REMOVAL OF CORROSIONBINDING/ADDING OF ADDITIONAL REINFORCEMENTWELDINGANCHORING TO THE EXISTING MEMBERS THROUGH SHEAR KEYS OR ANCHORSSHOTCRETINGPLATE BONDINGJACKETINGFIBRE WRAPPINGUNDERPINNING24

PROCEDUREREMOVAL OF LOOSE MATERIALS/RUSTPROVIDING PROTECTIVE LAYER/COATINGPROVIDING BONDING COAT BETWEEN OLD AND NEW MATERIAL/SURFACESPROVIDING STEEL MEMBERS/WELDING/ANCHORS/ SHEAR KEYS TO ENSURE MONOLITHIC ACTION

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RETROFITTINGPLATE BONDINGFIBRE WRAP TECHNIQUES THROUGH GLASS FIBRES/CARBON FIBRESRCC JACKETING26

CAUSES OF FAILURE OF MASONRY BUILDINGSPOOR QUALITY OF MORTARIRREGULARITY IN PLANE AND VERTICAL DIRECTIONNO PROVISION OF BANDSNO THOROUGH STONESHEAVY MASS CONCENTRATION AT ROOF LEVELUNSYMMETRICAL BUILDINGS AND FULL OPENINGSUNCONFINED WALL CORNERSINADEQUATELY DESIGNED CANTILEVER ELEMENTS27

MASONRY STRUCTURES28

VULNERABILITYBRICK/STONE MASONRY STRUCTURES ARE MORE VULNERABLE? DISASTER= VULNERABILITY X HAZARDBRICK STRUCTURES ARE MORE IN THE COUNTRYSO WE NEED SAFE BRICK MASONRY STRUCTURESIF NOT, WE NEED TO MAKE THEM SAFE BY RETROFITTING.29

SEISMIC STRENGTHENING/ RETROFITTINGTHE TECHNIQUE TO UPGRADE THE STRUCTURE FOR EARTHQUAKE RESISTANCE TO THE LEVEL OF PRESENT DAY CODAL REQUIREMENTS HAVING ORIGINAL STRUCTURAL INADEQUACY OR INADEQUACY DUE TO MATERIAL DEGRADATION OVER TIME OR DUE TO ALTERATIONS CARRIED OUT DURING ITS USE OVER THE YEARS

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SEISMIC STRENGTHENINGMAIN PURPOSE OF SEISMIC STRENGTHEING IS TO UPGRADE/PROVIDE THE SEISMIC RESISTANCE ON A BUILDING SO THAT IT BECOMES SAFER UNDER EARTHQUAKE OCCURANCESAVOIDING THE POSSIBILITY OF BRITTLE MODES OF FAILURE BY PROPER REINFORCEMENT AND CONNECTION OF RESISTING MEMBERS

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IS CODESCODESIS 13935 (JUNE 2009) GUIDELINES FOR REPAIR, RESTORATION, CONDITION ASSESSMENT AND SEISMIC STRENGTHEING OF MASONRY BUILDINGSDRAFT CODE WITH COMMENTARY ON SEISMIC EVALUATION AND STREGTHENING OF EXISTING BUILDINGS FOR RCC STRUTURES

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GENERAL PROVISIONS REQUIRED IN MASONRY BUILDINGSPLINTH BANDLINTEL BAND ROOF SLAB/ROOF BANDCORNER REINFORCEMENTBRICK WORK IN CEMENT MORTAR OF 1:6RESTRICTED OPENINGSADEQUATE FOUNDATION

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SELECTION OF MATERIALS AND TECHNIQUES FOR RETROFITTINGCEMENTSTEEL BOLTS, RODS, ANGLES, BEAMS, CHANNELS, EXPANDED METAL, WELDED WIRE FABRICADMIXTURES TO IMPROVE NON-SHRINKAGE (GROUTS CONSISING POLYMER, NON-SHRINK CEMENT AND SPECIAL SANDS), BOND (EPOXY RESINS) ETC.

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SEQUENCE OF RETROFITTINGREPAIR/REHABILITATIONALL CRACKS SHOULD BE FULLY REPAIREDPRESSURE INJECTION OF NON-SHRINK CEMENT POLYMER GROUT FOR 0.5 TO 5 MM CRACKSREPAIR BY EXPANSIVE CEMENT MORTAR, QUICK SETTING CEMENT, ADDL. SHEAR OR FLEXURAL REINFORCEMENT, STEEL MESH, STEEL RODS

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REPAIR/STRENGTHENING OF WALLSBY GROUTING (CEMENT WATER MIXTURE OR POLYMERIC MORTAR)BY ADDITION OF VERTICAL REINFORCEMENT CONCRETE COVERINGS ON THE TWO SIDES OF THE WALLBY PRESTRESSING WALL

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HORIZONTAL SEISMIC BELTSTO BE PROVIDED ON ALL WALLSON BOTH THE FACESJUST ABOVE THE LINTELBELOW ROOFBELOW FLOORIN CASE OF RCC SLAB ROOF BELT NOT REQUIREDNOT REQUIRED AT PLINTH LEVEL UNLESS PLINTH HEIGHT IS MORE THAN 900 MM

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ON ALL WALLSON BOTH THE FACESABOVE LINTEL

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SEISMIC BELTS AROUND DOOR/WINDOW OPENINGSIN CATEGORY D AND E BUILDINGSMESH OF GAUGE 10 WITH 8 WIRES IN VERTICAL DIRECTION SPACED AT 25 MM IN A BELT WIDTH OF 200MM ORGAUGE 13 WITH 10 WIRES IN VERTICAL DIRECTION SPACED AT 25 MM IN A BELT WIDTH OF 250MM (IN CAT. C BUILDINGS ALSO)

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AROUND OPENINGS

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VERTICAL SEISMIC BELTS AT CORNERSAT THE CORNERS OF ROOMSJUNCTIONS OF THE WALLSWIDTH ON EACH SIDE OF THE CORNER TO BE KEPT 25 MM EXTRA TO THE WIDTH OF THE MESHREIFORCEMENT TO BE STARTED BELOW 300 MM BELOW PLINTH LEVEL

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49AT EXTERNAL CORNERS

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VERTICAL REINFORCEMENT AT INSIDE CORNER

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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

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ANCHORSMECHANICAL ANCHORSCHEMICAL ANCHORS

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57PROCEDURE OF ANCHORING

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SPECIFICATIONS FOR HORIZONTAL SEISMIC BELT

SPEC. FOR VERITICAL REINFORCEMENT59

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Additional steps Repair and rehabilitation to be carried out prior to retrofitting.At the external corners, on each face of the wall, the width of the mesh for corner reinforcement may be kept as minimum 250 mm on each wall so that it covers minimum one brick. The mesh reinforcement at the corners may be kept minimum 300 mm below ground level67

On the internal cross walls since stiffening is available, horizontal seismic belt can be restricted just to have anchoring effect on cross wall. In the present case this was limited to 600 mm.

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Contd. Mesh reinforcement used should be galvanized steel and anti rusting paint should be applied on the cut points to prevent corrosion.MS washers used on wire mesh should be painted with anti corrosive paint. In the present case, M.S. washers of size 50X50X5 mm were used to anchor the mesh reinforcement.Since it was not possible to provide roof belt of mesh of required width in central portion due to segmental arch construction and ventilators provided near the top portion, MS flat belt was provided.69

The anchors are to be inserted into the hole after the grout is inserted within gel time, which is given 4 minutes for temperature of 30 degree Celsius and 6 minutes for 20 degree Celsius for the anchors and chemical grout used from Hilti India Private Limited.70

In the inside corner reinforcement, a prefabricated MS piece was used having two holes, one used for inserting into the bar which can be adjusted at any position and other end used for inserting anchor. Chemical anchoring was done thereafter. Anchoring on wire mesh should be in staggered (zig-zag) manner.

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72TRAINING, SKILL UPGRADATION AND COMPETENCE DEVELOPMENTSTAKEHOLDERSPOLICY MAKERSTRAINERSPARTICIPANTSIMPLEMENTERS

POLICY MAKERSTRAINERSPARTICIPANTSIMPLEMENTERS

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Item 1 Providing and fixing 250 mm wide or required size seismic belt for retrofitting with 12 gauge (2.64 mm dia) galvanized iron welded mesh with 25 mm spacing of wire on walls at required height (inside and out side the building ) fixed in position with headed nails at required distance complete as per direction of Engineer-in-charge. (Cut end of wire mesh to be painted with NitoZinc Primer)

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Item 2Providing and fixing stainless steel anchors of 8 mm dia (HAS-EM8 x 80 / 14) of HILTI or equivalent on GI wire mesh at required distance in staggered position i/c drilling of 10 mm dia hole with HILTI hammer drill machine TE-6S or equivalent and cleaning of hole by brush and blow out pump. Anchors shall be fixed by resin and hardener pack of HILTI make HY-150/330/2R or equivalent (35 holes per tube of 330 ml) chemical. Mesh will be fixed with MS washer of size 50x50x5 mm painted with NitoZinc primer (FOSROC) on top of the mesh with anchor screwed with nut complete as per direction of Engineer- in- charge.

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Item 3Painting on galvanized iron / steel work such as M.S. angle, flat, cold twisted bars with Protective / Bond coats i.e NitoZinc (FOSROC) primer of approved brand and manufacture as per direction of Engineer-in-charge.(Surface area of steel work shall be measured for payment)

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Item 4Providing and Fixing steel reinforcement bar 10 mm dia for seismic strengthening of building at inside corner i/c fixing with M.S. cleat 50x50x6 mm size having 2 holes. The reinforcement bar shall pass through one hole and other hole shall be used for anchoring into brick / CC wall. (The payment for steel reinforcement, Anchor & grouting at floor and roof shall be paid for separately)76

Item 5Providing and fixing seismic band for seismic strengthening of size 50x5 mm flat iron section at required level including making necessary holes not more than 75 cm apart and keeping in position with nails and finally fixing with Anchors ( Payments for Anchors & its fixing shall be made separately).77

Item 628 mm thick Acrylic modified cement mortar/micro concrete band at required level with mix 1:1:2 (1 cement : 1 coarse sand : 2 graded stone aggregate 6 mm & down nominal size) in two coats admixed with polymer modified compound (Armourcrete / Tapecrete) @ 10% of cement (by weight) used area and including slurry coat of Acrylic cement @ 2.2 kg / sqm mixed with polymer modified compound (Armourcrete/ Tapecrete) @ 10% of cement used and finished smooth complete (top layer will be of 12 mm plaster).

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