structure repairs & rehabilitation presentation no.3 presentation from tsg

Structure Repairs & Rehabilitation Presentation No.3

Presentation From TSG

Structure Repairs & RehabilitationType 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 & RehabilitationCategories Of Seismic Damage

Damage Categories Extent Of Damage In General Suggested Post Earth Quake Action

G1 Slight Non Structural Damage

Thin Crack in Plaster, Falling of Plaster bits in limited parts

Building Need Not to Vacated., only architectural repairs required.

G2 Slight 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.

G3 Moderate 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.

Structure Repairs & RehabilitationCategories Of Seismic Damage

Damage Categories Extent Of Damage In General Suggested Post Earth Quake Action

G4 Severe 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.

G5 Collapse A 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.

Structure Repairs & RehabilitationEarthquake Effects on Soils & Foundations & Solution

Features For FoundationsType “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 & RehabilitationS.No.

Type Of Soil Damaging Effect Of Earth quake

Earth quack Resisting Feature

1. Type I Hard None Use any foundation type2. 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 SoftLow Water Table

Not Much In Zone II Use 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.

Structure Repairs & RehabilitationS.No. Type Of Soil Damaging Effect Of Earth

quakeEarth quack Resisting Feature

3.b.

Type III SoftLiquefiable with high water table

Some relative movement in Zone II

Use Plinth beam to connect isolatedFoundations

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

Structure Repairs & RehabilitationIrregular 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

FloorOpening

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.

LAL

A

L2A2

L1A1

24 mA=18m


• 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

Structure Repairs & Rehabilitation• Mass Irregularity Example: IF 2nd storey Weight> 2.0x3rd Storey2nd 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.

5

4

3

2

1

Elevations

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 1L

A > 0.15 LA > 0.25 LL

a

bShear Wall

Upper FloorLower Floor

Structure Repairs & Rehabilitation• Weak Storey (lateral Strength of Each storey

vary F1 < 0.8 F2 (or F3 )

F1

F2

F3

Structure Repairs & RehabilitationRedesigning existing structure for nature forcesIt 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.


Crack Investigation• Location• Profile (vertical, Horizontal, Diagonal)• Crack Size (Depth & length)

Structure Repairs & RehabilitationCrack 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 work2. At localized locations in wall due to different

reasons3. 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 up area.

Layout Plan

B

L< 3B

L< 3B

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 PlanB

L < 3 B ; L < 45 mm

(A < 0 .15 L) B

A

Structure Repairs & Rehabilitation Lateral Supports To Long Wall

Buttress Maximum 6m Interval

R.C.C./B.W. Columns Maximum 6m Interval

Structure Repairs & Rehabilitation• Separation Sections to divide OneBuilding into more.

1 2 12 1

2

3

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.

Spacing “h/4”

Structure Repairs & Rehabilitation• Ductility Detailing Column Beam Connection

Level of Casting Of column Lift

Shear Key Pockets

L1

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

≤ 150 mm

Structure Repairs & RehabilitationBeam ReinforcementSpacing

• Splice In Bottom bar: within ¼ of span

• Splice In Top bar: within 2/3 of middle of span

≥ Ld

Ld

Ld

≥300 mm

Structure Repairs & Rehabilitation Column Reinforcement

6mm Ø @ 150 mm

Middle 2/3 rd of height

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 building below that required by the design codes.

Structure Repairs & RehabilitationImportance 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 Zone II III IV V1.5 Building Retrofitting need C D E 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 & RehabilitationCyclone Obstructed by Retaining Wall

• Cyclones

Structure Repairs & RehabilitationAlthough, 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 & RehabilitationBelieve it or not this wooden school did not crack or fall in Sikkim earth quack even it was neglected structure.

Structure Repairs & RehabilitationBelieve 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 & RehabilitationThis 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


Plaster came out in few panel of one old Accra school building in Sikkim earth quack.


•Higher plinth level with plinth protection

h2

b5b4

b7

b8

h2

b2

h1

b5

Structure Repairs & RehabilitationElevation : Distance b1 to b8 changes as per Building

Retrofitting Need

b1

b4 b4

b6

l1 l2

b4

t

1122 2

3

h3 b3


Table :Size, Position Of Opening In Above Figure Description Building Retrofitting

Need/CategoryAction For Retrofitting, if code

requirement not found satisfiedC D & E

Mortar Cement : 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 mm 450 mm If not satisfied the limit than modify location of opening or

make reinforce belt


Table :Size, Position Of Opening In Above Figure Description Building Retrofitting

Need/CategoryAction For Retrofitting, if code requirement not

found satisfiedC D & E

(b1+b2+b3)/l1 ; (b6+b7)/l2 = 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

0.46m 0.42m

0.37m 0.33m

`b4 0.45 m 0.56 m

Structure Repairs & RehabilitationTable :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

C D & E

`h3 (minimum) 600 mm 600 mm

`b8 (Max.) 900 mm 900 mm

≤20 t t

Structure Repairs & RehabilitationElevation : 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 ≥35 t or 8.0 m t≥ 190 mm


• 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 34 Beam

Crack


Item Of Roof/Floor

Requirement as per IS 4326 For School Building category

Retrofitting Action, if code provision not satisfiedC D E

1 2 3 4 5 61. Roof/Floor with

Prefabricated/pre cast element

Tie Beam All round

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.


Item Of Roof/Floor



1 2 3 4 5 63. 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


Item Of Roof/Floor



1 2 3 4 5 64. Jack arch

roof/floorConnect 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.


Item Requirement as per IS 4326 For School Building category

Retrofitting Action, if code provision not satisfied

C D E

1 2 3 4 5 6a. Sloping raftered

roofsPreferably 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.

Structure Repairs & Rehabilitation• Beam Jacketing

New Bar

Beam Chipped Surface painted with epoxy

Shortcrete

Flooring Along Beam are removed

Column


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.

Structure Repairs & RehabilitationStrengthening of Cracked Wall

Sectional Elevation Of Wall

Clamps or Tie Rod connected to Wire Mesh along cracksCrack wider than 5 mm

Grout Port

Wire Mesh (50mmx 50 mm Opening)

20x40 mm thick Mortar or Micro concrete

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 ElevationSide Elevation

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

Structure Repairs & RehabilitationStrengthening 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 wideGrout Port Mortar(1:1) + Non Shrink GroutWire Mesh (50mmx 50 mm Opening)

20x40 mm thick Mortar or Micro concrete

Grout 1:1 + non shrink compound

Structure Repairs & Rehabilitation• Cross Wall Connection Strengthening

t ≥2t

Drilled Hole

Tor Rod Grouted

Elevation Of Stone Masonry WallPLAN

Structure Repairs & Rehabilitation75 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

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


0° Orientation of mesh 45° Orientation of meshOrientation of mesh increases tensile strength of structure by way of increased energy absorption. It is maximum for 45 degree


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 & RehabilitationS.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.

Structure Repairs & RehabilitationS.No. Classification Of Damageability Of Masonry Buildings3. 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.


Building Type

Description

1 A a) Rubble stone in mud mortar or without mortar usually with sloping wooden roof

b) Mud walls , Adobe walls of two storeyc) Un coursed rubble masonry without adequate through stonesd) Masonry with rounded ( undresses) stones

2 A+ a) Adobe ( un burnt block or brick) walls of single storeyb) 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


Building Type

Contd. Description

5 C a) 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)

6 C+ a) Like C (a) type but also having horizontal seismic bands at lintel level of doors and windows( IS 4326)

7 D 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.


• 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.


• Damageability Grades Of Masonry BuildingsS.No.

Type Of Building

Zone II(MSK VI or less)

Zone III(MSK VII)

Zone IV (MSK VIII)

Zone V (MSK IX or More)

1 A & 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 2 Few (5 to 15%) of grade 4

Few of grade 5

Rest no damage Rest of grade 2 , 1 Rest of grade 3 , 2 Rest of grade 4 , 32 B & B+ Many of grade 2 Most of grade 3 Many of grade 4

Few of grade 1 Few of grade 3 Few of grade 4 Few of grade 5Rest no damage Rest of grade 1 Rest of grade 2 Rest of grade 3

3 C & C+ Many of grade 1 Most of grade 2 Many of grade3

Few of grade 1 Few of grade 2 Few of grade 3 Few of grade 4Rest no damage Rest of grade 1 Rest of grade 1 Rest of grade 2

4 D --- Few of grade 1 Few of grade 2 Many of grade 2Note :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)


• 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


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


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


• 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”


• 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


• 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


• 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

Structure Repairs & Rehabilitation• G.I. Mesh Reinforcement in seismic belts in various

building categories with overlapping of 300 mm

S.No Length of wall

Category C Category D Category E

In M G No. Wide G No. Wide G No. Wide1. ≤ 5.0 13 9 250 12 9 250 10 10 2802. 6.0 12 9 250 10 10 280 10 14 3803. 7.0 10 10 280 10 14 380 10 18 4604 8.0 10 14 380 10 18 460 10 12 580

GAUGE (G)10=3.25,G12=2.64,G13=2.34,G14=2.03mmTransverse 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.


• Procedure of Seismic belt Construction1. 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.


S.No

No. Of Storey

Storey Category C Category D Category E

Single Bar in mm

Mesh G 10

Single Bar in mm

Mesh G 10

Single Bar in mm

Mesh G 10

NO. of wire

W NO. of wire

W NO. of wire

W

1. One - - - 10 10 300 12 14 400

2. Two First - - - 10 10 300 12 14 400

3. Ground - - - 12 14 400 16 - -

4. Three 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

•Vertical Belt At Corners & Junction of Rooms

G 10= 3.25 mm dia@ 25 mm; Transverse wire in mesh @ 150 mm. c/c


• Vertical Belt t

t+600B

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


• 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.


• Compressing The Walls for Box Action

ROOM PLAN

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

1 kg(f)/c.m.2

pre stress is sufficient to compress the wall


• 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.


• 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.m2


• 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.


• 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


• 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 YDetail “Y” Refer

Next Slide

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

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.


• 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


• 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. flatWooden Joist

PLAN

Structure Repairs & Rehabilitation• Connection of old brick work with new

150 mm

200 mm

220 mm500 mm

100

12 mm Ø- 1 No.12050

20

New wall

Old wall

Plan Showing connection of Wall

Concrete grout

6 mm Ø- 1 No.

150 mm

Steel bar embedded in mortar

Structure Repairs & Rehabilitation• Connection of New brick wall with Stone

MasonryBrick masonry

Existing old Stone masonry

Structure Repairs & Rehabilitation• Corner Connection

150

1000

16 Ø ,1.15 m

Plan 250 mm

500 mm

500 mm

t

Steel Grouting

8 Ø @200c/c

Section

210

Structure Repairs & Rehabilitation• Strengthening Of Foundations

a. Introducing new load bearing membersb. Improving the drainage of the area to

prevent saturation of foundation soilc. Providing apron around the building to

prevent soaking of foundationd. Adding strong elements in the form of

reinforced concrete strips attached to the existing foundation part of building


• 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

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.

structure repairs & rehabilitation presentation no.3 presentation from tsg

Documents