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Structure Repairs & Rehabilitation Presentation No.3 Presentation From TSG.

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1 Structure Repairs & Rehabilitation Presentation No.3 Presentation From TSG

2 Structure Repairs & Rehabilitation Type Of Building Construction A. Based On Construction Method B. Based On Design & Supervision

3 Structure Repairs & Rehabilitation A. Based On Construction Method Load Bearing Wall With Step/Strip Footing R.C.C. Frame Work Precast Structural Frame Work

4 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)

5 Structure Repairs & Rehabilitation Categories Of Seismic Damage Damage CategoriesExtent Of Damage In GeneralSuggested Post Earth Quake Action G1Slight Non Structural Damage Thin Crack in Plaster, Falling of Plaster bits in limited parts Building Need Not to Vacated., only architectural repairs required. G2Slight 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.) Building Need Not to Vacated., Cracks in walls need grouting. Architectural repairs carried out to achieve durability. Seismic strengthening is desirable. G3Moderate Structural Damage Large & deep Crack in walls; Cracking of walls, columns, piers, & tilting or falling of chimney. (The load carrying capacity of structure is partially reduced.) Building Need to be Vacated for structural restoration & seismic strengthening. Finally Architectural treatment may be carried out.

6 Structure Repairs & Rehabilitation Categories Of Seismic Damage Damage CategoriesExtent Of Damage In GeneralSuggested Post Earth Quake Action G4Severe Structural Damage Gaps occur in walls; Inner or outer wall collapse; Failure of ties. Approximate 50% of the main structural elements fail. The building takes a dangerous states. Building has to be vacated. For demolishing or extensive restoration & strengthening work has to be carried out. G5CollapseA large part of whole of the building collapses. Redesign & construction of Building. This Table is useful for considering retrofitting to be undertaken & cost for rehabilitation of building.

7 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.

8 Structure Repairs & Rehabilitation S. No. Type Of SoilDamaging Effect Of Earth quake Earth quack Resisting Feature 1.Type I HardNoneUse any foundation type 2.Type II Medium Not much in Zones II & III Relative Lateral Movement Possible in Zone IV,V Use any foundation type Use tie beams in case of Individual column Foundations 3. a. Type III Soft Low Water Table Not Much In Zone IIUse Any Type of Foundation. Use plinth bend. Relative Movement Is Possible In Zone III to V 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.

9 Structure Repairs & Rehabilitation S.No.Type Of SoilDamaging Effect Of Earth quake Earth quack Resisting Feature 3. b. Type III Soft Liquefiable with high water table Some relative movement in Zone II Use Plinth beam to connect isolated Foundations Relative Lateral & Vertical movements in Zone III 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. 3c.Black Cotton Soil 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

10 Structure Repairs & Rehabilitation Irregular Shape Building Should be Avoided. Diaphragm Discontinuity-(Openings or different shape in Each floor) Out- Of Plan Offset(Discontinuity like Stilt floor, House having open spaces in G.F.) Non Parallel System Floor Opening

11 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. L A L A L2 A2 L1 A1

12 24 m A=18m Structure Repairs & Rehabilitation Re- Entrant corner 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 12 m Plan F

13 Structure Repairs & Rehabilitation Mass Irregularity Example: IF 2 nd storey Weight> 2.0x3 rd Storey 2 nd storey Weight> 2.0x 1 st 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. 5 4 3 2 1 Elevations

14 A A L2 Structure Repairs & Rehabilitation Vertical Geometrical Irregularity If In Plan Discontinuity in vertical Element Resisting Lateral Force L1 L 2 > 1.5 L 1 L A > 0.15 LA > 0.25 L L a b Shear Wall Upper Floor Lower Floor

15 Structure Repairs & Rehabilitation Weak Storey (lateral Strength of Each storey vary F1 < 0.8 F2 (or F3 ) F1 F2 F3

16 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.

17 Structure Repairs & Rehabilitation Crack Investigation Location Profile (vertical, Horizontal, Diagonal) Crack Size (Depth & length)

18 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 1/3 rd height from bottom & top depending on fixing conditions of column ends. 2.At laps location,if laps are not staggered or not sufficient length.

19 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

20 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.

21 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.

22 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 up area. Layout Plan B L< 3B

23 C (C < 0.15 B) Structure Repairs & Rehabilitation Suitability Of Typical School Building Plan Open area should be not more than 50% of Plan area. Layout Plan B L < 3 B ; L < 45 mm (A < 0.15 L) B A

24 Structure Repairs & Rehabilitation Lateral Supports To Long Wall Buttress Maximum 6m Interval R.C.C./B.W. Columns Maximum 6m Interval

25 Structure Repairs & Rehabilitation Separation Sections to divide One Building into more. 1 2 1 2 1 2 3

26 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.

27 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.

28 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.

29 Spacing “h/4” Structure Repairs & Rehabilitation Ductility Detailing Column Beam Connection Level of Casting Of column Lift Shear Key Pockets L1 2 d d In length L1,Spacing Of ring < 0.25 times of minimum width of column or ≥ 75mm or ≤ 100mm Ld+10 Ø-2Ø for each bend In length 2d(as shown),Spacing Of Stirrups ≤ (0.25X d) of beam or 8X Ø mm or ≥ 75 mm L1 should be 450 mm or 1/6 th of clear height of column/longer side of column section, whichever is greater

30 ≤ 150 mm Structure Repairs & Rehabilitation Beam Reinforcement Spacing Splice In Bottom bar: within ¼ of span Splice In Top bar: within 2 / 3 of middle of span ≥ Ld

31 Ld ≥300 mm Structure Repairs & Rehabilitation Column Reinforcement 6mm Ø @ 150 mm Middle 2/3 rd of height

32 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.

33 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 building below that required by the design codes.

34 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 ZoneIIIIIIVV 1.5Building Retrofitting needCDEE

35 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.

36 Structure Repairs & Rehabilitation For Masonry Structures code consider following Plinth Bend (if strata is soft, non-uniform) Lintel level bend Roof level/ Eve level/ Gable level bend Reinforcement at corner of wall Shape, Size & location of Window In Wall Unsupported Wall length to Height Ratio Cross wall, Brick Pillar, Buttress

37 Structure Repairs & Rehabilitation Cyclone Obstructed by Retaining Wall Cyclones

38 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.

39 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

40 Structure Repairs & Rehabilitation Believe it or not this wooden school did not crack or fall in Sikkim earth quack even it was neglected structure.

41 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.

42 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

43 Structure Repairs & Rehabilitation Plaster came out in few panel of one old Accra school building in Sikkim earth quack.

44 Structure Repairs & Rehabilitation Higher plinth level with plinth protection

45 h2h2 b5b5 b4b4 b7b7 b8 h2h2 b2b2 h1h1 b5b5 Structure Repairs & Rehabilitation Elevation : Distance b1 to b8 changes as per Building Retrofitting Need b1b1 b4b4 b4b4 b6b6 l1l1 l2l2 b4b4 t 1 1 22 2 3 h3 b3b3

46 Structure Repairs & Rehabilitation Table :Size, Position Of Opening In Above Figure Description Building Retrofitting Need/Category Action For Retrofitting, if code requirement not found satisfied CD & E MortarCement : lime: sand 1:2:9 or CS-1: 6 Cement : lime: sand 1:1:6 or 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 `b5 (Minimum) 230 mm450 mmIf not satisfied the limit than modify location of opening or make reinforce belt

47 Structure Repairs & Rehabilitation Table :Size, Position Of Opening In Above Figure Description Building Retrofitting Need/Category Action For Retrofitting, if code requirement not found satisfied CD & E (b1+b2+b3)/l 1 ; (b6+b7)/l 2 = shall not exceed ( For one Storey Building ) ( For Two Storey Building ) ( For Three & Four Storey Building ) 0.55 m 0.50m 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 0.46m0.42m 0.37m0.33m `b40.45 m0.56 m

48 Structure Repairs & Rehabilitation Table :Size, Position Of Opening In Above Figure Seismic belt at plinth is provided if plinth is 900mm 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. Description Building Retrofitting Need/Category Action For Retrofitting, if code requirement not found satisfied CD & E `h3 (minimum) 600 mm `b8 (Max.) 900 mm

49 ≤20 t t Structure Repairs & Rehabilitation Elevation : Masonry Building With Limitations for retrofitting limit Buttress Can Be Avoided by increasing wall thickness between the cross wall. D V Buttress Wall W Maximum 4.0 M 15 t ≤35 t ≥35 t or 8.0 m t≥ 190 mm

50 Structure Repairs & Rehabilitation Cracks are Cleaned by Air. Nozzles 1 & 4 are fixed by 1:3 mortar. 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. 1 2 3 4 Beam Crack

51 Structure Repairs & Rehabilitation S. No. Item Of Roof/Floor Requirement as per IS 4326 For School Building category Retrofitting Action, if code provision not satisfied CDE 123456 1.Roof/Floor with Prefabricated/ pre cast element Tie Beam All round & R.C. Screeding Provide R.C. screed & Seismic belt or band around 2.Roof/Floor with wooden joists, various covering elements (brick, reeds, etc) & earth fill All round Seismic band & integration of units as rigid horizontal diaphragm Provide Seismic belt around, Interconnect beam ends through wooden planks & diagonal cross ties.

52 Structure Repairs & Rehabilitation S. No. Item Of Roof/Floor Requirement as per IS 4326 For School Building category Retrofitting Action, if code provision not satisfied CDE 123456 3.Sloping roofs with sheet or tile coverings i) Horizontal cross bracing at level of ties of the trusses Install the cross bracings & anchor truss into walls & anchor rafters into seismic belt at eave ii) Cross bracing in the planes of the rafters & purlins

53 Structure Repairs & Rehabilitation S.N o. Item Of Roof/Floor Requirement as per IS 4326 For School Building category Retrofitting Action, if code provision not satisfied CDE 123456 4.Jack arch roof/floor Connect the steel joists by horizontal ties at intervals to prevent spreading & cracking of the arches. Provide Seismic band all round Install steel flats as ties by welding them to the steel joists and provide seismic belt. 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.

54 Structure Repairs & Rehabilitation S.N o. ItemRequirement as per IS 4326 For School Building category Retrofitting Action, if code provision not satisfied CDE 123456 a. Sloping raftered roofs Preferably use full trusses Convert rafters into A – frames or full trusses to reduce thrust on walls b. Unsymmetrical plans Symmetrical plans are suggested Inserting New walls to reduce dissymmetry. c. Perpendicular walls not connected at corners and T- junctions Perpendicular walls should be integrally constructed. Stitch the perpendicular walls using tie rods in drilled holes and grouted or with seismic belts.

55 Structure Repairs & Rehabilitation Beam Jacketing New Bar Beam Chipped Surface painted with epoxy Shortcrete Flooring Along Beam are removed Column

56 Structure Repairs & Rehabilitation Beam strengthening COLUMN New Bars are fixed In Columns for beam in top & bottom face ‘U’ shape stirrups are fixed from bottom of beam into slab Remove Plaster of beam and flooring is removed along beam Jacketing is done using Micro concrete with self flowing admixture. Pull test is carried out grouted bars in drilled holes randomly.

57 Structure Repairs & Rehabilitation Strengthening of Cracked Wall Sectional Elevation Of Wall Clamps or Tie Rod connected to Wire Mesh along cracks Crack wider than 5 mm Grout Port Wire Mesh (50mmx 50 mm Opening) 20x40 mm thick Mortar or Micro concrete

58 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 Side Elevation Grouting ports are fixed 2 to 4 No. / sqm, Grout 1:1: 225 gram of Non Shrinking compound Per 1Bag Of Cement

59 Structure Repairs & Rehabilitation Strengthening of Multiple Cracked Wall Sectional Elevation Of Cracked Or Week Wall 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) 20x40 mm thick Mortar or Micro concrete Grout 1:1 + non shrink compound

60 Structure Repairs & Rehabilitation Cross Wall Connection Strengthening t ≥2t Drilled Hole Tor Rod Grouted Elevation Of Stone Masonry Wall PLAN

61 Structure Repairs & Rehabilitation 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. Fill the concrete from both side & then use non shrink grout Curing for 10 days is must for such element Temporary Support

62 Structure Repairs & Rehabilitation Vertical Face Of Stone Masonry Wall 1.0 m 0.5 m 1.0 m Through Stone are 1.0m apart vertically & horizontally with 0.5 m staggering horizontal

63 Structure Repairs & Rehabilitation 0° Orientation of mesh45° Orientation of mesh Orientation of mesh increases tensile strength of structure by way of increased energy absorption. It is maximum for 45 degree

64 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.

65 Structure Repairs & Rehabilitation S.No Classification Of Damageability Of Masonry Buildings 1. 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. 2. Grade 2 : Moderate damage (Slight structural damage, moderate non-structural damage) a) Structural : Cracks in many walls, thin cracks in RC slabs & A.C. sheets b) Non structural :Fall of fairly large pieces of plaster, partial collapse of smoke chimneys on roofs, damage to parapets, chajjas. Roof tiles distributed in about 10% of the area. Minor damage in under structure of slopping roofs.

66 Structure Repairs & Rehabilitation S.No. Classification Of Damageability Of Masonry Buildings 3. 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). 4. 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. 5. 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.

67 Structure Repairs & Rehabilitation S. No. Building Type Description 1 Aa)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 2A+A+ a)Adobe ( un burnt block or brick) walls of single storey b)Rammed earth Pile construction 3Ba)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 4B+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

68 Structure Repairs & Rehabilitation S.No. Building Type Contd. Description 5Ca) Unreinforced masonry walls built from fully 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) 6C+C+ a) Like C (a) type but also having horizontal seismic bands at lintel level of doors and windows( IS 4326) 7Da) 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.

69 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.

70 Structure Repairs & Rehabilitation Damageability Grades Of Masonry Buildings S.No.Type Of Building Zone II (MSK VI or less) Zone III (MSK VII) Zone IV (MSK VIII) Zone V (MSK IX or More) 1A & A+Many( 50%) of grade 1 damage Most( 75%) of grade 3 damage Most of grade 4 damage Many( 50%) of grade 5 Few of grade 2Few (5 to 15%) of grade 4 Few of grade 5 Rest no damageRest of grade 2, 1Rest of grade 3, 2Rest of grade 4, 3 2B & B+Many of grade 2Most of grade 3Many of grade 4 Few of grade 1Few of grade 3Few of grade 4Few of grade 5 Rest no damageRest of grade 1Rest of grade 2Rest of grade 3 3C & C+Many of grade 1Most of grade 2Many of grade3 Few of grade 1Few of grade 2Few of grade 3Few of grade 4 Rest no damageRest of grade 1 Rest of grade 2 4D ---Few of grade 1Few of grade 2Many of grade 2 Note :For re-entrant corners (one of plan irregularity ) consider one grade higher. Few of Grade 3 Detail evaluation is required for vertical,plan irregularity, liquefiable or landslide area structures. (rest of grade 1)

71 Structure Repairs & Rehabilitation Drilling And Grouting Of Tie Rod At Spring Level Weld 12 Ø Load of roof from Arch are transferred through prop. Before Fixing Tie Rod. Grouting using NSC/ Hilti compound

72 Structure Repairs & Rehabilitation X Props are Placed on both side of wall To Support wall above R.C.C. Lintel Or Steel Joist. GROUTING in between wall & lintel

73 Structure Repairs & Rehabilitation Last slide continue Fixing Of Lintel (Or Steel Joist encased in concrete )over Weak Arch PROPS Sectional Elevation showing fixing of Lintel over Arch ROOF ARCH Wall Above Arch

74 Structure Repairs & Rehabilitation Preventing Arch Cracking By providing Ties Bearing Plate “A” Flat Iron Or Rod Connecting Bottom Flanges Of ‘I’ Section by Bolt Or Welding Jack Arch Roof Flat Iron Or Rod “A”

75 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 Non shrinking compound are injected after 14 days of curing Localized bulge

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

77 Structure Repairs & Rehabilitation Strengthening of wall around Door & window 200 mm wide Wire Mesh of 10 Gauge having 8 wire with 25 mm pitch or 250 mm of 13 gauge having 10 wire with 25 mm pitch for D & E category. 250 mm of 13 gauge having 10 vertical wire with 25 mm pitch for “C “ category. Wire mesh is provided on both face for room except those spanning < 5.0M

78 Structure Repairs & Rehabilitation G.I. Mesh Reinforcement in seismic belts in various building categories with overlapping of 300 mm S.NoLength of wall Category CCategory DCategory E In MGNo.WideGNo.WideGNo.Wide 1.≤ 5.0139 250 12925010 280 2.6.012925010 2801014380 3.7.010 28010143801018460 48.0101438010184601012580 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.

79 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.

80 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.

81 Structure Repairs & Rehabilitation S. No No. Of Storey StoreyCategory CCategory DCategory E Single Bar in mm Mesh G 10 Singl e Bar in mm Mesh G 10 Single Bar in mm Mesh G 10 NO. of wire W W W 1.One---10 3001214400 2.TwoFirst---10 3001214400 3.Ground---121440016-- 4.ThreeSecond10 30010 3001214400 5.First10 30012144001625650 6.Ground121440012144001625650 Vertical Belt At Corners & Junction of Rooms G 10= 3.25 mm dia@ 25 mm; Transverse wire in mesh @ 150 mm. c /c

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

83 Structure Repairs & Rehabilitation Vertical Bar At Corner of room ‘L’ Shape Dowel of 8 mm of vertical leg 400 mm & 150 mm horizontal leg First Dowel just above P.L. & next at every 1.0 m Steel bar minimum750 mm below G.F. 75 mm Ø Hole Grout by NSC Vertical bar at corner & 15 mm covered with 1:3 cement mortar or 1:1.5:3 Micro concrete Roof P.L. G.L.

84 Structure Repairs & Rehabilitation Compressing The Walls for Box Action ROOM PLAN The Vertical Spacing of pre-stressing steel rods shall be 1/3 rd & 2/3 rd 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 1/3 rd height. In R.C. slab provide such tie only at mid height of wall 1 kg(f)/c.m. 2 pre stress is sufficient to compress the wall

85 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.

86 Structure Repairs & Rehabilitation Strengthening of wall for making fit for compression for pre-stressing Elevation OF Weak Masonry Wall Cross Section Nozzle for Injection Grout Nozzle spacing 2 to 4 No. per sqm c/c; Grout 1 cement: 1 Water under pressure 1 to 3 kg/c.m 2

87 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.

88 Structure Repairs & Rehabilitation Strengthening Of Rafter roof having attic. Pair of Planks 200x40 mm nailed at ends Attic Floor Beam Steel anchor Flat 50x3 or 50x4 mm @ 3 to 4 mtr Apart Intermediate wall may not exist Rafter 100 mm

89 Structure Repairs & Rehabilitation Half Split Bamboo Ties To Rafter Brace the Rafter to 50 mm Dia Bamboo (B) Seismic Bend & Rafter should be tied Properly X Three Nails 5Ø filled in member made by splitting bamboo in two part B Cross bracings at ends of room Y Y Detail “Y” Refer Next Slide

90 Structure Repairs & Rehabilitation Detail “Y” New Plank for bracing, at end bay,nailed through wall Rafter Grouting of bolt Flat on both face, clamped to plank M.S. Flat clamp

91 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 Ø bars @150 c/c both ways or bounded by a horizontal cast-in situ reinforcement concrete ring beam all round into which the ends of R.C. elements are embedded.

92 Structure Repairs & Rehabilitation A Key In Wall for RC bend @ 3mtr c/c Out of400 mm wide RC bend,150 mm rested in wall Pre-fab slab unit Cage For Key 6 Ø, 2 No.Ring 16 Ø, 2 No. shear Stiffening of an existing floor 6 Ø bw@150c/c Bar In Topping X X

93 Structure Repairs & Rehabilitation Stiffening flat wooden floor/roof Resting On stone or brick masonry Wood Plank Diagonal Ties Tie Plank 100x 25 thick connecting joist & diagonal bracing 1.5 to 3.0 m thick G.I. flat Wooden Joist PLAN

94 Structure Repairs & Rehabilitation Connection of old brick work with new 150 mm 200 mm 100 12 mm Ø- 1 No. 120 50 20 New wall Old wall Plan Showing connection of Wall Concrete grout 6 mm Ø- 1 No. 150 mm Steel bar embedded in mortar

95 Structure Repairs & Rehabilitation Connection of New brick wall with Stone Masonry Brick masonry Existing old Stone masonry

96 Structure Repairs & Rehabilitation Corner Connection 150 1000 16 Ø,1.15 m Plan 250 mm 500 mm t Steel Grouting 8 Ø @200c/c Section 210

97 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

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

99 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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