Structure Repairs & Rehabilitation

Structure Repairs & Rehabilitation

Structure Repairs & Rehabilitation Presentation Presentation From Structure Repairs & Rehabilitation Type Of Building Construction A. Based On Construction Method B. Based On Design & Supervision Structure Repairs & Rehabilitation A. Based On Construction Method Load Bearing Wall With Step/Strip Footing R.C.C. Frame Work Precast Structural Frame Work Structure Repairs & Rehabilitation B. Based On Design & Supervision Engineered Building (Designed & supervised By Engineer) Non-Engineered Building

(Built by Mason, Carpenters without Input From Engineer) Semi Engineered Building (Ex. In masonry Building, where Load bearing wall had not been properly designed. Generally It is built by Architect & Contractors without involving Engineer effectively) Pre- Engineered Buildings (Those Non Engineered building which is complying IS 4326,IS 13827, IS 13828 ,IS 13935) Structure Repairs & Rehabilitation Categories Of Seismic Damage Damage Categories Extent Of Damage In General G1 Slight Non Structural Thin Crack in Plaster, Falling of Damage Plaster bits in limited parts G2

Slight Structural Damage G3 Moderate Structural Damage Small crack in walls, Falling of Plaster in large bits over large areas; Damage of non structural Parts like projecting of cornice, kitchen chimney etc.(The load carrying capacity is not reduced appreciably.) Large & deep Crack in walls; Cracking of walls, columns, piers, & tilting or falling of chimney. (The load carrying capacity of structure is partially reduced.)

Suggested Post Earth Quake Action Building Need Not to Vacated., only architectural repairs required. Building Need Not to Vacated., Cracks in walls need grouting. Architectural repairs carried out to achieve durability. Seismic strengthening is desirable. Building Need to be Vacated for structural restoration & seismic strengthening. Finally Architectural treatment may be carried out. Structure Repairs & Rehabilitation Categories Of Seismic Damage Damage Categories G4

Severe Structural Damage G5 Collapse Extent Of Damage In General Suggested Post Earth Quake Action Gaps occur in walls; Inner or Building has to be vacated. outer wall collapse; Failure of For demolishing or ties. Approximate 50% of the extensive restoration & main structural elements fail. The strengthening work has to building takes a dangerous be carried out. states.

A large part of whole of the Redesign & construction of building collapses. Building . This Table is useful for considering retrofitting to be undertaken & cost for rehabilitation of building. Structure Repairs & Rehabilitation Earthquake Effects on Soils & Foundations & Solution Features For Foundations Type I Rock Or Hard Soil-Well graded gravel Mixtures with or without clay binder, and clayey sands poorly graded or sand clay mixtures(GB,CW,SB,SW & SC) N>30 Type II Medium Soils- All soils N= 10 to 30 & Poorly Graded Sands Or Gravely Sands with Little or No fines (SP) with N>15 Type III Soft Soils Other than SP with N < 10. Structure Repairs & Rehabilitation

S. Type Of Soil No. 1. Type I Hard 2. Type II Medium Damaging Effect Of Earth quake None Not much in Zones II & III Relative Lateral Movement Possible in Zone IV,V Type III Soft Not Much In Zone II Low Water Table Relative Movement Is Possible In Zone

III to V Earth quack Resisting Feature Use any foundation type Use any foundation type Use tie beams in case of Individual column Foundations 3. a. Use Any Type of Foundation. Use plinth bend. Use Plinth beam to connect all type of foundation such as isolated, combined column footings Or provide rafts Or piles as needed for the loads. Structure Repairs & Rehabilitation

S.No. Type Of Soil 3. b. Type III Soft Some relative movement Liquefiable with in Zone II high water table Relative Lateral & Vertical movements in Zone III 3c. Black Cotton Soil Damaging Effect Of Earth quake

Earth quack Resisting Feature Use Plinth beam to connect isolated Foundations Use piles going to stable soil layer or minimum 10 m length. Driven piles preferable. Liquefaction resulting in tilting/ overturning of buildings & structures likely in zones IV & V Improve the soil to a depth of 7 to 8m or up to stable layer if met earlier, by dynamic compaction or by compaction piles. Use piles going to stable soil layer or minimum 10 m length. Driven piles preferable. Soil not seen to be affected in intensity VII shaking in Latur, Jabalpur

earthquakes but effect of ground motion amplified on the buildings Use Plinth beams to connect individual column footings. Use Plinth Band in case of strip foundations. Use of under ream piles preferable Structure Repairs & Rehabilitation Irregular Shape Building Should be Avoided. Diaphragm Discontinuity-(Openings or different shape in Each floor) Opening Floor Out- Of Plan Offset(Discontinuity like Stilt floor, House having open spaces in G.F.) Non Parallel System Structure Repairs & Rehabilitation

Torsion Irregularities are In floor plan like tilting or deformed or Both. Re-entrant Corner If A/L>0.15 to 0.2. L2 A2 A L L A L1 A1 Structure Repairs & Rehabilitation Re- Entrant corner

12 m 24 m A=18m Plan A Plan B Plan C Plan D Plan F In Plan A, As per rule In Y-dir. A/L=18/24=0.75> 0.15 In X-dir. A/L=6/12=0.50> 0.15 Plan F Structure Repairs & Rehabilitation 5 Mass Irregularity 4 Example: IF

3 nd rd 2 storey Weight> 2.0x3 Storey 2 1 2nd storey Weight> 2.0x 1st Storey Stiffness Irregularity (If stiffness of different floors are changed by certain limit due to change in height or like omitting load bearing wall at particular floor, change in shape or Size of floor etc. Elevations Structure Repairs & Rehabilitation Vertical Geometrical Irregularity L1 A A L

L L2 If A > 0.25 L A > 0.15 L L 2 > 1.5 L 1 In Plan Discontinuity in vertical Element Resisting Lateral Force Upper Floor a Shear Wall b Lower Floor Structure Repairs & Rehabilitation Weak Storey (lateral Strength of Each storey vary F1 < 0.8 F2 (or F3 ) F3 F2

F1 Structure Repairs & Rehabilitation Redesigning existing structure for nature forces It is a comprehensive task & require planning which include following Information gathering. Field investigations including details of sub strata, foundation details, extent of damage Type of Existing structure & its members stability Design Data Collection Identification of components required to be strengthened Cost Estimates (it is feasible up to 60% of new construction) Method or Procedure to be fallowed. Structure Repairs & Rehabilitation Crack Investigation Location Profile (vertical, Horizontal, Diagonal) Crack Size (Depth & length) Structure Repairs & Rehabilitation

Crack Location In Structure Foundation: 1. Cracks Travel vertical in step footing in case of unequal settlement. Flooring: 1. It is circular, Linear. Column: 1. Generally at 1/3rd height from bottom & top depending on fixing conditions of column ends. 2. At laps location ,if laps are not staggered or not sufficient length. Structure Repairs & Rehabilitation Brick Work: In wall at ends of lintel in Diagonal upward directions. 1. Horizontal, generally at slab wall joint , when whole wall sink. 2. Vertical, in case of unequal settlement Beam: 1. Near Support ,visible on both face of beam & bottom.

2. At centre of beam in its bottom Structure Repairs & Rehabilitation Slab : 1. At centre of Span in ceiling (slab bottom) 2. At top & bottom face of slab near the supporting wall or at top surface in case of cantilever Plaster: 1. At joints with R.C.C & brick work 2. At localized locations in wall due to different reasons 3. Locations as briefed in cracks in B.W. Structure Repairs & Rehabilitation Make structure floor, roof lighter as much as possible. Avoid Un- symmetry of structure as much as possible. For this purpose structure can be divided. Sand Pilling ,Stabilization of weak soil, sandy soil having high water level must be taken care off. Proper Connections of building Elements. Use steel to strengthen laterally for load bearing wall as per code requirement.

Provide adequate plinth protection. Avoid to built Rigid masonry Building freely resting on rock in Earth Quack porn area. Structure Repairs & Rehabilitation Consider retaining wall, breast wall while estimating school building in heavy slope hills. A building shaped like a box, such as rectangular both in plan & elevation is inherently stronger than one that is L-shaped or U-shaped or such a building with wings. Open area should be not more than 50% of built L< 3B up area. B Layout Plan Structure Repairs & Rehabilitation Suitability Of Typical School Building Plan L < 3 B ; L < 45 mm

B (A < 0 .15 L) A L< 3B B C (C < 0 .15 B) Open area should be not more than 50% of Plan area. Layout Plan Structure Repairs & Rehabilitation Lateral Supports To Long Wall R.C.C./B.W. Columns Maximum 6m Interval Buttress Maximum

6m Interval Structure Repairs & Rehabilitation Separation Sections to divide One Building into more. 3 1 2 2 1 1 2 Structure Repairs & Rehabilitation Avoid keeping shallow foundation on Black Cotton Soil. Use one type of foundation in a whole building to

avoid differential settlement. Physical quality check on material should me periodic. An addition of room, which is structurally independent from an existing building should be designed & constructed in accordance with the seismic requirements of new compiled structures. Structure Repairs & Rehabilitation Any existing seismic resistance building if occupied for school building then the building has to be rechecked for seismic resistance for building importance factor of 1.5. Projecting parts like cornices, facia stones, parapets etc. should be avoided as for as possible, otherwise they should be properly reinforced and firmly tied to the main structure Refer IS 1893 CLAUSE -7.12.2 Ceiling plaster should be avoided as possible. Structure Repairs & Rehabilitation Whenever one un symmetrical building is divided

into two or more building by separation walls the structure of the divided building up to plinth level is generally monolithic. Refer code IS 4326 5.1 to 5.2 Even Where calculations based on code- based seismic coefficients may not indicate tension steel requirements, the reinforcement suggested in the form of seismic bands & vertical steel bars at corners & junction of walls & jambs of openings must be provided since these are safe guard for probable maximum earthquake. Structure Repairs & Rehabilitation Ductility Detailing L1 should be 450 mm or 1/6 th of clear height of Column Beam Connection Ld+10 -2 for each bend L1 Spacing h/4

2d column/longer side of column section, whichever is greater d In length L1 ,Spacing Of ring < 0.25 times of L1 Shear Key minimum width of column Pockets or 75mm or 100mm In length 2d(as shown) ,Spacing Of Stirrups (0.25X d) of beam or Level of Casting Of 8X mm or 75 mm column Lift Structure Repairs & Rehabilitation Beam Reinforcement

Spacing 150 mm Ld Splice In Bottom bar: within of span Splice In Top bar: within 2/ of middle of span 3 Structure Repairs & Rehabilitation Column Reinforcement 6mm @ 150 mm Ld Ld Middle 2/3 rd of height 300 mm Structure Repairs & Rehabilitation Corrosion resistance precautions should also be taken in ductility detailing of cyclone prone

& tsunami prone coastal areas. IS 456 does not allow R.C.C. below M20 grade. Structure Repairs & Rehabilitation An addition of new structure which is not structurally independent should be designed & constructed such that the entire building conforms to the seismic resistance requirements for new building configuration. The addition should not increase the seismic force in any structural elements of the existing building by more than 5% unless the capacity of the element subject to the increased force is still in compliance with the standard. The addition should not decrease the seismic resistance of any structural element of the existing Structure Repairs & Rehabilitation Importance Factor(I) For Building Depend Upon Functional Use Of Structure Hazardous Consequences Of Its Failure Post Earthquake Personal needs Historical Value

Economic Importance School Building Have I value=1.5 I value 1.5 Zone Building Retrofitting need II C III D IV E V E Structure Repairs & Rehabilitation Seismic wave propagation increases as height of

wall/structure increases. Seismic wave propagation pushes bricks of corner of wall out of building. Movement of Seismic wave through joints of similar or dissimilar component of building ,makes joint open resulting of falling of component of the building. Lateral strength of existing building is improved by grouting, additional of vertical reinforcement concrete coverings on the two sides of the wall,& by pre stressing the wall. Structure Repairs & Rehabilitation Cyclone Obstructed by Retaining Wall Cyclones Structure Repairs & Rehabilitation Although, the 2005 Kashmir earthquake destroyed many houses and schools, But many old buildings did not suffer any damage because they were built with timber elements embedded in brick and stone masonry. Structure Repairs & Rehabilitation

Himachal Pradesh also has old tradition of including many timber elements in stone masonry walls to make the buildings earthquake resistant. These buildings survive earthquakes without any damage Structure Repairs & Rehabilitation Believe it or not this wooden school did not crack or fall in Sikkim earth quack even it was neglected structure. Structure Repairs & Rehabilitation Believe it or not this Ekra school did survive in Sikkim earth quack even it has been poorly built in as Plinth & ground is on same level. Structure Repairs & Rehabilitation This slide shows joint of plinth beams at corner of column. Due to no hook in many of bars in plinth beam ,whole of wall above plinth beam came out with the plinth beam at corner

column in sikkim earth quack Bar without hook Structure Repairs & Rehabilitation Plaster came out in few panel of one old Accra school building in Sikkim earth quack. Structure Repairs & Rehabilitation Higher plinth level with plinth protection Structure Repairs & Rehabilitation Elevation : Distance b1 to b8 changes as per Building Retrofitting Need l l 1 2 b8

3 b1 b4 b5 1 h1 b2 h3 2 h2 b4 t b3 2 b4 b6 b7

2 1 b4 h2 b5 Structure Repairs & Rehabilitation Table :Size, Position Of Opening In Above Figure Description Building Retrofitting Need/Category C D&E Action For Retrofitting, if code requirement not found satisfied

Mortar Cement : Cement : lime: sand lime: sand 1:2:9 or 1:1:6 or CS-1: 6 CS-1: 4 Chemical test of mortar is carried out ,if it is less than recommendation than wall grouting or wire mesh fixing or fiber reinforce mortar is carried out If not satisfied the limit than modify location of opening or make reinforce belt `b5 (Minimum)

230 mm 450 mm Structure Repairs & Rehabilitation Table :Size, Position Of Opening In Above Figure Description Building Retrofitting Need/Category C D&E (b1+b2+b3)/l1 ; (b6+b7)/l2 = shall not exceed ( For one Storey Building ) ( For Two Storey 0.55 m Building ) 0.46m

( For Three & Four 0.37m Storey Building ) `b4 0.45 m 0.50m 0.42m 0.33m 0.56 m Action For Retrofitting, if code requirement not found satisfied This limit is fallowed by changing opening size, closing opening or reinforcing opening by belting. Increased spacing b4 either by reducing, shifting window

opening , or belting full width b4 Structure Repairs & Rehabilitation Table :Size, Position Of Opening In Above Figure Description Building Retrofitting Need/Category C D&E Action For Retrofitting, if code requirement not found satisfied 600 mm 600 mm `h3 (minimum) belt(Max.)

at plinth is provided if plinth is 900mm Seismic`b8 900 mm 900 mm above ground. Belt around door, window provided with details as per zone on both face of opening. Ceiling or eve level belt on both side wall for prefab & slopping roof. Gable & ridge level belt on both side of wall in case of pitched roof. Window sill level belt on both face in three story building for achieving category D , E Vertical bar or belt in all story at corner & junction of wall & in jambs for achieving category D,E & in three story in category C. Structure Repairs & Rehabilitation Elevation : Masonry Building With Limitations for retrofitting limit t 190 mm

t Maximum 4.0 M 15 t 35 t or 8.0 m 20 t Buttress Wall 35 t 35 t V W D Buttress Can Be Avoided by increasing wall thickness between the cross wall. Structure Repairs & Rehabilitation

Cracks are Cleaned by Air. Nozzles 1 & 4 are fixed by 1:3 mortar. 1 2 3 4 Beam Crack Then Compressed air is passed through nozzles 1 & 4. Nozzles 2 & 3 are fixed using mortar 1:3. Filled cracks with mortar1:3. Grout Nozzles in this face of beam in sequence of 1,4,2,3.Use sand in grout for nozzle 2 & 3 . Same is fallowed in opposite face of beam for nozzles 1 & 4. Use Non shrinking grout ,which is 225 gram packet for 1 bag of cement. Pressure of grout is normally 3 kg/c.m.2 It vary with size of crack.

Structure Repairs & Rehabilitation S. Item Of No Roof/Floor . 1 2 1. Roof/Floor with Prefabricated/ pre cast element 2. Roof/Floor with wooden joists, various Requirement as per IS 4326 For School Building category C D E

3 4 5 Tie Tie Beam All Beam All round round & R.C. Screeding All round Seismic band & integration of units as rigid horizontal Retrofitting Action, if code provision not satisfied 6 Provide R.C. screed &

Seismic belt or band around Provide Seismic belt around, Interconnect Structure Repairs & Rehabilitation S. Item Of No Roof/Floor . Requirement as per IS 4326 For School Building category C D E Retrofitting Action, if code provision not satisfied

1 2 3. Sloping roofs with sheet or tile coverings 3 4 5 i) Horizontal cross bracing at level of ties of the trusses ii) Cross bracing in the planes of the rafters & purlins 6 Install the cross bracings & anchor truss into walls &

anchor rafters into seismic belt at eave Structure Repairs & Rehabilitation S.N Item Of o. Roof/Floor 1 4. 2 Jack arch roof/floor Requirement as per IS 4326 For School Building category C D E

Retrofitting Action, if code provision not satisfied 3 4 5 6 Connect the steel joists by Install steel flats horizontal ties at intervals as ties by welding to prevent spreading & them to the steel cracking of the arches. joists and provide Provide Seismic band all seismic belt. round Note: R.C. screed consists of minimum 14 mm concrete reinforcement with 6 mm dia bars @ 100 mm c/c both ways(single layer),covering the whole roof /floor.

Structure Repairs & Rehabilitation S.N o. Item 1 2 a. Sloping raftered roofs b. Unsymmetrical plans Requirement as per IS 4326 For

School Building category C D E 3 4 5 Retrofitting Action, if code provision not satisfied 6 Preferably use full Convert rafters into A trusses frames or full trusses to reduce thrust on walls Symmetrical plans Inserting New walls to are suggested

reduce dissymmetry. Structure Repairs & Rehabilitation Beam Jacketing Beam Chipped Surface painted with epoxy Flooring Along Beam are removed New Bar Shortcrete Column Structure Repairs & Rehabilitation Beam strengthening New Bars are fixed In Columns for beam in top & bottom face Remove Plaster of beam and flooring is

removed along beam Jacketing is done U shape stirrups are using Micro fixed from bottom of beam concrete with into slab self flowing admixture. COLUMN Pull test is carried out grouted bars in drilled holes randomly. Structure Repairs & Rehabilitation Strengthening of Cracked Wall 20x40 mm thick Mortar or Micro concrete

Clamps or Tie Rod connected to Wire Mesh along cracks Crack wider than 5 mm Grout Port Wire Mesh (50mmx 50 mm Opening) Sectional Elevation Of Wall Structure Repairs & Rehabilitation School Buildings has to be construct as per Building Category C,D,E ( as per its EQ Zone). These Category define specific mortar for brick work & corresponding strength can be achieved by injecting grout in existing building walls. Same procedure is fallowed in cracked wall having crack width 0.5 to 5 mm with grouting port fixed along crack, spacing @ of wall thickness Front Elevation Grouting ports are fixed

2 to 4 No. / sqm, Grout 1:1: 225 gram of Non Shrinking compound Per 1Bag Of Cement Side Elevation Structure Repairs & Rehabilitation Strengthening of Multiple Cracked Wall 20x40 mm thick Mortar or Micro concrete Grout 1:1 + non shrink compound Tie Rods 300 to 400mm C/C connected to Wire Mesh along cracks Crack Or Cracks > 5 mm wide Grout Port Mortar(1:1) + Non Shrink Grout

Wire Mesh (50mmx 50 mm Opening) Sectional Elevation Of Cracked Or Week Wall Structure Repairs & Rehabilitation Cross Wall Connection Strengthening Drilled Hole Tor Rod Grouted t 2t Elevation Of Stone Masonry Wall PLAN Structure Repairs & Rehabilitation Fill the concrete from both side & then

use non shrink grout 75 mm Hole is made carefully through R.R. masonry & S-shape bar is casted using small size aggregate concrete 1:2:4 with NSC or self (free) flowing readymade grout. Temporary Support Curing for 10 days is must for such element Structure Repairs & Rehabilitation Vertical Face Of Stone Masonry Wall Through Stone are 1.0m apart vertically & horizontally with 0.5 m staggering horizontal 1.0 m

1.0 m 0.5 m Structure Repairs & Rehabilitation 0 Orientation of mesh 45 Orientation of mesh Orientation of mesh increases tensile strength of structure by way of increased energy absorption. It is maximum for 45 degree Structure Repairs & Rehabilitation As per above photograph ,it is possible that the reinforcement would have buckled or elongated or excessive yielding may have occurred. This element can be repaired by replacing the old portion of steel with new steel using butt welding or lap welding instead of just Splicing or overlapping . Additional stirrup ties are to be added in the damaged portion. Additional steel if required ,can be drilled and grouted by epoxy in undisturbed portion. Structure Repairs & Rehabilitation S.No

1. 2. Classification Of Damageability Of Masonry Buildings Grade 1 : Negligible to slight damage ( no structural damage , slight non-structural damage) a) Structural : hair line cracks in very few walls. b) Non structural: Fall of small pieces of plaster only. : Fall of loose stones from upper parts of buildings in very few cases. Grade 2 : Moderate damage (Slight structural damage , moderate Structure Repairs & Rehabilitation S.No. 3. 4. 5. Classification Of Damageability Of Masonry Buildings

Grade 3: Substantial to heavy damage ( moderate structural damage, heavy non structural damage) a) Structural: Large in extensive cracks in most walls. Wide spread cracking of column & piers. b) Non Structural : Roof tiles detach. Chimney fracture at the roof line : failure of non structural elements( partitions , gable walls). Grade 4: Very heavy damage ( heavy structural damage , very heavy non structural damage) .New construction may explore. For low strength masonry building use IS 13828. Structural : Serious failure of walls (gaps in walls), inner wall collapse ,Partial structural failure of roofs and floors. Grade 5 : Destruction ( very heavy structural damage). Total or near total collapse of the building. For low strength masonry building use IS 13828 in zone IV & V. S. Building Description No Type . 1 A a)

Rubble stone in mud mortar or without mortar usually with sloping wooden roof b) Mud walls , Adobe walls of two storey c) Un coursed rubble masonry without adequate through stones d) Masonry with rounded ( undresses) stones 2 A+ a) Adobe ( un burnt block or brick) walls of single storey b) Rammed earth Pile construction 3 B a) Semi-dressed, rubble , brought to courses, with through stones & long corner stone. unreinforced brick walls with country type wooden roofs, unreinforced CC block wall constructed in mud mortar or weak lime mortar. b) Earthen walls (Adobe , rammed earth ) with horizontal wooden elements

4 B+ a) Un reinforced brick masonry in mud mortar with vertical wood posts or horizontal wood element or seismic band (IS 13828) b) Unreinforced brick masonry in lime mortar Structure Repairs & Rehabilitation S.No Building Contd. Description . Type 5 C a) Unreinforced masonry walls built from fully Structure Repairs & Rehabilitation 6 C+

7 D dressed( Ashlar ) stone masonry or CC block or burn brick using good lime or cement mortar, either having RC floor/roof or sloping roof having eave level horizontal bracing system or seismic band. b) As at description B (a) with horizontal seismic bands (IS 13828) a) Like C (a) type but also having horizontal seismic bands at lintel level of doors and windows( IS 4326) a) Masonry construction as at type C (a) but reinforced with bands & vertical reinforcement ,etc ( IS 4326) or confined masonry using horizontal & vertical reinforcing of walls. Structure Repairs & Rehabilitation Medvedev-Sponheuer-Karnik (MSK) intensity scale is used to evaluate the severity of ground shaking on the basis of observed efforts in an area of the

earthquake occurrence. In the Scale few means 5-15 % buildings damage, Many means 50%, Most means 75%. For damageability of important building (school) in any zone , should be checked for the just higher zone. Table below provide help in evaluating need for improvement in building in consideration by using simple retrofitting methods for which more detailed evaluation is not feasible. Structure Repairs & Rehabilitation Damageability Grades Of Masonry Buildings S.No . 1 Type Of Zone II Building (MSK VI or less) A & A+ Many( 50%) of

grade 1 damage Few of grade 2 Rest no damage 2 B & B+ Few of grade 1 Rest no damage 3 C & C+ Zone III (MSK VII) Most( 75%) of grade 3 damage Few (5 to 15%) of grade 4 Rest of grade 2 , 1 Many of grade 2

Few of grade 3 Rest of grade 1 Many of grade 1 Few of grade 1 Few of grade 2 Rest no damage Rest of grade 1 4 D --Few of grade 1 Note :For re-entrant corners (one of plan irregularity ) consider one grade higher. Detail evaluation is required for vertical ,plan irregularity , liquefiable or landslide area structures. Zone IV (MSK VIII) Most of grade 4 damage Few of grade 5 Zone V

(MSK IX or More) Many( 50%) of grade 5 Rest of grade 3 , 2 Most of grade 3 Few of grade 4 Rest of grade 2 Most of grade 2 Rest of grade 4 , 3 Many of grade 4 Few of grade 5 Rest of grade 3 Many of grade3 Few of grade 3 Rest of grade 1 Few of grade 2 Few of grade 4 Rest of grade 2

Many of grade 2 Few of Grade 3 (rest of grade 1) Structure Repairs & Rehabilitation Drilling And Grouting Of Tie Rod At Spring Level Grouting using NSC/ Hilti compound Weld 12 Load of roof from Arch are transferred through prop. Before Fixing Tie Rod. Structure Repairs & Rehabilitation X GROUTING in between wall &

lintel Props are Placed on both side of wall To Support wall above R.C.C. Lintel Or Steel Joist. Structure Repairs & Rehabilitation Last slide continue Fixing Of Lintel (Or Steel Joist encased in concrete )over Weak Arch Wall Above Arch ROOF ARCH

PROPS Sectional Elevation showing fixing of Lintel over Arch Structure Repairs & Rehabilitation Preventing Arch Cracking By providing Ties A Flat Iron Or Rod Connecting Bottom Flanges Of I Section by Bolt Or Welding A Bearing Plate Jack Arch Roof Flat Iron Or Rod Structure Repairs & Rehabilitation Arch Supporting Pillar.

Use props to release load from wall Concrete Bond Stone at 1.0 m spacing Nozzle for grouting cement slurry using non shrinking compound Localized bulge Non shrinking compound are injected after 14 days of curing Structure Repairs & Rehabilitation Strengthening of footing & Column

Top Surface Should Be roughened & suitable epoxy is coated Bottom Bar is Exposed at edges Column Jacketing Bar grouted in drilled hole Bottom Bar welded 12 Addition Of P.C.C. Pull test should be done on Some Drilled & grouted bar . Structure Repairs & Rehabilitation

Strengthening of wall around Door & window 200 mm wide 250 mm of Wire Mesh of 13 gauge 10 Gauge having 10 having 8 wire vertical with 25 mm wire with pitch or 250 25 mm mm of 13 pitch for gauge having C 10 wire with 25 category. mm pitch for D & E category. Wire mesh is provided on both face for

room except those spanning < 5.0M Structure Repairs & Rehabilitation G.I. Mesh Reinforcement in seismic belts in various building categories with overlapping of 300 mm S.No Length of wall In M 1. 5.0 2. 6.0 3. 7.0 4 8.0 Category C G 13 12 10

10 No. 9 9 10 14 Category D Wide G 250 12 250 10 280 10 380 10 No. 9 10 14 18

Wide 250 280 380 460 Category E G 10 10 10 10 No. 10 14 18 12 Wide 280 380

460 580 GAUGE (G)10=3.25,G12=2.64,G13=2.34,G14=2.03mm Transverse wire in G.I.mesh up to 150 mm C/C. Structure Repairs & Rehabilitation Unless otherwise required for category C,D,E building. Seismic belt is not required for following situation 1. Under roof & floor if they are R.C.C. 2. If plinth level is less than 900 mm. 3. Eve level bend is provided instead of lintel level bend if eve level is not more than 900mm above the door opening. 4. For wall of shorter then 5.0 m, one face G.I. mesh & tied to the wall by hook of full width equal to wall @ 2.5 M. C/C & at turning of belt. Structure Repairs & Rehabilitation

Procedure of Seismic belt Construction 1. Mark the belt on wall & remove the plaster in area. 2. Rack joint 20mm deep & wash with enough water. 3. Apply 15 mm thick 1:3 mortar immediately after washing . Make plaster sufficiently rough. 4. Fix mesh using binding wire & nail of 150 mm @ 450 mm c/c. If mesh is on both face of wall then use anchor to connect both mesh & grout the anchor. 5. Wet the first layer & brush with slurry before doing second layer of 15 mm thick plaster. 6. Do curing for 10 days. Structure Repairs & Rehabilitation Vertical Belt At Corners & Junction of Rooms S. No. Of No Storey 1. One

2. Two Storey Category C Single Bar in mm Category D Mesh G 10 NO. of wire W Singl

Mesh e Bar G 10 in mm NO. W of wire Category E Single Bar in mm Mesh G 10 NO. W of wire - -

- 10 10 300 12 14 400 First - - -

10 10 300 12 14 400 Ground - - - 12

14 400 16 - - Second 10 10 300 10 10

300 12 14 400 5. First 10 10 300 12 14

400 16 25 650 6. Ground 12 14 400 12 14

400 16 25 650 3. 4. Three G 10= 3.25 mm [email protected] 25 mm; Transverse wire in mesh @ 150 mm. c/c Structure Repairs & Rehabilitation Vertical Belt t

200 mm overlap in Steel Mesh on each face 150 mm wide Steel Mesh held by wide head 150mm long nail 200 mm wide Mortar belt 150 mm Vertical Bar at corner of room 300 mm t+600

Structure Repairs & Rehabilitation Vertical Bar At Corner of roomL Shape Dowel Roof 75 mm Hole Grout by NSC P.L. G.L. of 8 mm of vertical leg 400 mm & 150 mm horizontal leg First Dowel just above P.L. & next at every 1.0 m Vertical bar at corner & 15 mm covered with 1:3 cement mortar or 1:1.5:3 Micro concrete

Steel bar minimum750 mm below G.F. Structure Repairs & Rehabilitation Compressing The Walls for Box Action The Vertical Spacing of pre-stressing steel rods shall be 1/3 rd & 2/3rd of the height of the wall from bottom. In case of slopping roof or pre fabricated element structure provide tie at middle at top of wall & at 1/3rd height. In R.C. slab provide such tie

only at mid height of wall ROOM PLAN 1 kg(f)/c.m.2 pre stress is sufficient to compress the wall Structure Repairs & Rehabilitation Before applying compression in the wall it has to ensure that 1. Wall should not be low strengthening mortar. 2. It will be better to strengthen week wall by injection grouting first. Structure Repairs & Rehabilitation Strengthening of wall for making fit for compression

for pre-stressing Nozzle spacing 2 to 4 No. per sqm c/c; Grout 1 cement: 1 Water under pressure 1 to 3 kg/c.m2 Nozzle for Injection Grout Elevation OF Weak Masonry Wall Cross Section Structure Repairs & Rehabilitation For roofing in zone 3 to 5 ,avoid tiles & use corrugated iron or asbestos sheeting. Asbestos sheet due to radioactivity & snow loading (due to rough surface) is avoided. Avoid false ceiling, otherwise it should be light & flexible like Hessian cloth, bamboo matting, non flammable foam. Structure Repairs & Rehabilitation

Strengthening Of Rafter roof having attic. Steel anchor Flat Intermediate wall 50x3 or 50x4 mm may not exist @ 3 to 4 mtr Apart Rafter Attic Floor Beam Pair of Planks 200x40 mm nailed at ends 100 mm Structure Repairs & Rehabilitation Three Nails 5 filled in member made by splitting bamboo in

two part X Y Y Cross bracings at ends of room B Detail Y Refer Next Slide Half Split Bamboo Ties To Rafter Brace the Rafter to 50 mm Dia Bamboo (B) Seismic Bend & Rafter should be tied Properly Structure Repairs & Rehabilitation New Plank for Detail Y

bracing, at end Rafter bay ,nailed through wall Grouting of bolt Flat on both M.S. Flat clamp face, clamped to plank Structure Repairs & Rehabilitation Where the roof or floor consists of prefabricated units like RC rectangular, T or channel units or wooden poles & joists carrying brick tiles, integration of such unit is necessary. Timber elements could be connected to diagonal planks nailed to them & spiked to an all round wooden frame at the ends. Reinforcement concrete elements may either have 40 mm cast-in situ concrete topping with 6 mm bars @150 c/c both ways or bounded by a horizontal castin situ reinforcement concrete ring beam all round

into which the ends of R.C. elements are embedded. Structure Repairs & Rehabilitation A X 6 [email protected]/c Bar In Topping 16 , 2 No. shear 6 , 2 No.Ring X Cage For Key Key In Wall for RC bend @ 3mtr c/c Pre-fab slab unit Out of400 mm wide RC bend ,150 mm rested in wall Stiffening of an existing floor Structure Repairs & Rehabilitation

Stiffening flat wooden floor/roof Resting On stone or brick masonry Wood Plank Tie Plank 100x 25 thick connecting joist & diagonal bracing Diagonal Ties Wooden Joist 1.5 to 3.0 m thick G.I. flat PLAN Structure Repairs & Rehabilitation Connection of old brick work with new Old wall Steel bar embedded

Concrete grout in mortar 6 mm - 1 No. 150 mm 20 12 mm - 1 No. 120 50 New wall 500 mm 150 mm 100 Plan Showing connection of Wall 220 mm

200 mm Structure Repairs & Rehabilitation Connection of New brick wall with Stone Masonry Brick masonry Existing old Stone masonry Structure Repairs & Rehabilitation t Corner Connection 16 ,1.15 m 1000 210 8 @200c/c Plan Steel Grouting

150 250 mm 500 mm 500 mm Section Structure Repairs & Rehabilitation Strengthening Of Foundations a. Introducing new load bearing members b. Improving the drainage of the area to prevent saturation of foundation soil c. Providing apron around the building to prevent soaking of foundation d. Adding strong elements in the form of reinforced concrete strips attached to the existing foundation part of building Structure Repairs & Rehabilitation

To avoid disturbance to the integrity of the existing wall, during the foundation strengthening process, proper investigation & design is a must. 250 350 300 8,350 x 350 mm 2-16 Top & Bottom Each 400 4-16 350 300

4-16 Structure Repairs & Rehabilitation Conclusion : School building comes under important building of importance factor 1.5 & therefore while using any of above method should be under taken only with consent of structural designer as he is the person who can well judge which method is most suited for getting non collapse criteria for the EQ zone.

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