Structure Repairs & Rehabilitation Presentation No.3 Presentation From TSG.
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Transcript of 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
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
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.
Structure Repairs & Rehabilitation
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
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
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
Structure Repairs & Rehabilitation
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
Structure Repairs & Rehabilitation
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
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 34 Beam
Crack
Structure Repairs & RehabilitationS.No.
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.
Structure Repairs & RehabilitationS.No.
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 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
Structure Repairs & RehabilitationS.No.
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 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.
Structure Repairs & RehabilitationS.No.
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
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.
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
Structure Repairs & Rehabilitation
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
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 & 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.
Structure Repairs & RehabilitationS.No.
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
Structure Repairs & RehabilitationS.No.
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.
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 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)
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
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
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
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”
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
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
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
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.
Structure Repairs & Rehabilitation
• 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.
Structure Repairs & Rehabilitation
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
Structure Repairs & Rehabilitation
• 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
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.
Structure Repairs & Rehabilitation
• Compressing The Walls for Box Action
ROOM PLAN
The Vertical Spacing of pre-stressing steel rods shall be 1/3 rd & 2/3rd 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
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
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
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.
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
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 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.
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
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. 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
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
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.