Presentation. From. Structure Repairs & Rehabilitation. Type Of Building Construction. A. Based On Construction Method. B. . Based On Design & Supervision. Structure Repairs & Rehabilitation. ID: 619848
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Structure Repairs & Rehabilitation Presentation
Presentation From
Slide2Structure Repairs & Rehabilitation
Type Of Building Construction
A. Based On Construction Method
B.
Based On Design & Supervision
Slide3Structure Repairs & Rehabilitation
A. Based On Construction Method
Load Bearing Wall With Step/Strip Footing
R.C.C. Frame Work
Precast Structural Frame Work
Slide4Structure 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)
Slide5Structure Repairs & Rehabilitation
Categories 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.
Slide6Structure Repairs & Rehabilitation
Categories Of Seismic Damage
Damage CategoriesExtent Of Damage In GeneralSuggested Post Earth Quake ActionG4Severe Structural DamageGaps 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.
Slide7Structure 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.
Slide8Structure Repairs & Rehabilitation
S.
No.
Type Of
Soil
Damaging
Effect Of Earth quake
Earth quack Resisting Feature
1.
Type I Hard
None
Use 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 II
Use Any Type of
Foundation. Use plinth bend.
Relative
Movement Is Possible In Zone III to V
Use P
linth beam to connect all type of foundation such as isolated, combined column footings Or provide rafts Or piles as needed for the loads.
Slide9Structure Repairs & Rehabilitation
S.No.
Type Of
Soil
Damaging
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 P
linth 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
Slide10Structure 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
Slide11Structure 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
Slide1224 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
Slide13Structure
Repairs & Rehabilitation
Mass Irregularity Example: IF 2nd storey Weight> 2.0x3rd Storey2nd storey Weight> 2.0x 1st StoreyStiffness 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
Slide14A
A
L2
Structure
Repairs & Rehabilitation
Vertical Geometrical Irregularity IfIn Plan Discontinuity in vertical Element Resisting Lateral Force
L1
L 2 > 1.5 L 1
L
A > 0.15 L
A > 0.25 L
L
a
b
Shear Wall
Upper Floor
Lower
Floor
Slide15Structure Repairs & Rehabilitation
Weak Storey (lateral Strength of Each storey vary F1 < 0.8 F2 (or F3 )
F1
F2
F3
Slide16Structure 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.
Slide17Structure Repairs & Rehabilitation
Crack Investigation
Location
Profile (vertical, Horizontal, Diagonal)
Crack Size (Depth & length)
Slide18Structure Repairs & Rehabilitation
Crack Location In Structure
Foundation:
Cracks Travel vertical in step footing in case of unequal settlement.
Flooring:
It is circular, Linear.
Column:
Generally at 1/3
rd
height from bottom & top depending on fixing conditions of column ends.
At laps location ,if laps are not staggered or not sufficient length.
Slide19Structure Repairs & Rehabilitation
Brick Work:
In wall at ends of lintel in Diagonal upward directions.
Horizontal, generally at slab wall joint , when whole wall sink.
Vertical, in case of unequal settlement
Beam:
Near Support ,visible on both face of beam & bottom.
At centre of beam in its bottom
Slide20Structure Repairs & Rehabilitation
Slab
:
At centre of Span in ceiling (slab bottom)
At top & bottom face of slab near the supporting wall or at top surface in case of cantilever
Plaster:
At joints with R.C.C & brick work
At localized locations in wall due to different reasons
Locations as briefed in cracks in B.W.
Slide21Structure 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.
Slide22Structure 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
Slide23L< 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 Plan
B
L < 3 B ; L < 45 mm
(A < 0 .15 L)
B
A
Slide24
Structure
Repairs & Rehabilitation
Lateral Supports To Long Wall
Buttress Maximum 6m Interval
R.C.C./B.W. Columns Maximum 6m Interval
Slide25Structure
Repairs & Rehabilitation
Separation Sections to divide One
Building into more.
1
2
1
2
1
2
3
Slide26Structure 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.
Slide27Structure 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
.
Slide28Structure 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.
Slide29Spacing
“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
Slide30≤ 150 mm
Structure Repairs & Rehabilitation
Beam ReinforcementSpacingSplice In Bottom bar: within ¼ of spanSplice In Top bar: within 2/3 of middle of span
≥ Ld
Slide31Ld
Ld
≥300 mm
Structure
Repairs & Rehabilitation
Column Reinforcement
6mm Ø @ 150 mm
Middle 2/3
rd
of height
Slide32Structure 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.
Slide33Structure 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.
Slide34Structure Repairs & Rehabilitation
Importance Factor(I) For Building Depend UponFunctional Use Of StructureHazardous Consequences Of Its FailurePost Earthquake Personal needsHistorical ValueEconomic ImportanceSchool Building Have “I” value=1.5
“I”
value
Zone
II
III
IV
V
1.5
Building
Retrofitting need
C
D
E
E
Slide35Structure 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.
Slide36Structure 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
Slide37Structure Repairs & RehabilitationCyclone Obstructed by Retaining Wall
Cyclones
Slide38Structure 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.
Slide39Structure 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
Slide40Structure Repairs & Rehabilitation
Believe it or not this wooden school did not crack or fall in Sikkim earth quack even it was neglected structure.
Slide41Structure 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.
Slide42Structure 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
Slide43Structure Repairs & Rehabilitation
Plaster came out in few panel of one old Accra school building in Sikkim earth quack.
Slide44Structure Repairs & Rehabilitation
Higher plinth level with plinth protection
Slide45h
2
b5
b4
b7
b8
h
2
b
2
h1
b5
Structure
Repairs & Rehabilitation
Elevation :
Distance b1 to b8 changes as per Building Retrofitting Need
b
1
b
4
b
4
b
6
l
1
l
2
b
4
t
1
1
2
2
2
3
h3
b
3
Slide46Structure Repairs & Rehabilitation
Table :Size, Position Of Opening In Above Figure
Description
Building Retrofitting Need/Category
Action For
Retrofitting, if code requirement not found satisfied
C
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
`b
5 (Minimum)
230
mm
450 mm
If not satisfied the limit than modify location of opening or make
reinforce belt
Slide47Structure Repairs & Rehabilitation
Table :Size, Position Of Opening In Above Figure
Description
Building Retrofitting Need/Category
Action For
Retrofitting, if code requirement not found satisfied
C
D & 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
0.46m
0.42m
0.37m
0.33m
`b4
0.45 m
0.56 m
Slide48Structure Repairs & Rehabilitation
Table :Size, Position Of Opening In Above FigureSeismic 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
Slide49≤20 t
t
Structure
Repairs & Rehabilitation
Elevation : Masonry Building With Limitations for retrofitting limitButtress 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
Slide50Structure 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
Slide51Structure Repairs & Rehabilitation
S.No.
Item Of Roof/Floor
Requirement as per IS 4326
For School Building category
Retrofitting Action, if code provision not satisfied
C
D
E
1
2
3
4
5
6
1.
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.
Slide52Structure Repairs & Rehabilitation
S.No.
Item Of Roof/Floor
Requirement as per IS 4326
For School Building category
Retrofitting Action, if code provision not satisfied
C
D
E
1
2
3
4
5
6
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
Slide53Structure Repairs & Rehabilitation
S.No.
Item Of Roof/Floor
Requirement as per IS 4326
For School Building category
Retrofitting Action, if code provision not satisfied
C
D
E
1
2
3
4
5
6
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.
Slide54Structure Repairs & Rehabilitation
S.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
6
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.
Slide55Structure Repairs & Rehabilitation
Beam Jacketing
New Bar
Beam Chipped Surface painted with epoxy
Shortcrete
Flooring Along Beam are removed
Column
Slide56Structure 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.
Slide57Structure 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
Slide58Structure 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
Slide59Structure 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
Slide60Structure Repairs & Rehabilitation
Cross Wall Connection Strengthening
t
≥2t
Drilled Hole
Tor Rod Grouted
Elevation Of Stone Masonry Wall
PLAN
Slide61Structure 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
Slide62Structure 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
Slide63Structure Repairs & Rehabilitation
0° Orientation of mesh
45° Orientation of mesh
Orientation of mesh increases tensile strength of structure by way of increased energy absorption. It is maximum for 45 degree
Slide64Structure 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.
Slide65Structure 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.
Slide66Structure 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.
Slide67Structure Repairs & Rehabilitation
S.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 storey
c)
Un coursed rubble masonry without adequate through stones
d)
Masonry with rounded ( undresses) stones
2
A
+
a)
Adobe ( un burnt block or brick) walls of single storey
b)
Rammed earth Pile construction
3
B
a)
Semi-dressed, rubble , brought to courses, with through stones & long corner stone. unreinforced brick walls with country type wooden
roofs, unreinforced CC block wall constructed in mud mortar or weak lime mortar.
b)
Earthen walls (Adobe , rammed earth ) with horizontal wooden elements
4
B
+
a)
Un reinforced brick masonry in mud mortar with vertical wood posts or horizontal wood element or seismic band (IS 13828)
b)
Unreinforced brick masonry in lime mortar
Slide68Structure Repairs & Rehabilitation
S.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.
Slide69Structure 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.
Slide70Structure 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)
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 , 3
2
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 5
Rest 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 4
Rest 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 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)
Slide71Structure 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
Slide72Structure 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
Slide73Structure 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
Slide74Structure 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”
Slide75Structure 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
Slide76Structure 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
Slide77Structure 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
Slide78Structure Repairs & Rehabilitation
G.I. Mesh Reinforcement in seismic belts in various building categories with overlapping of 300 mm
S.NoLength of wallCategory CCategory DCategory EIn MGNo.WideGNo.WideGNo.Wide1.≤ 5.013925012925010102802.6.0129250101028010143803.7.010102801014380101846048.0101438010184601012580
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.
Slide79Structure Repairs & Rehabilitation
Unless otherwise required for category C,D,E building. Seismic belt is not required for following situation
Under roof & floor if they are R.C.C.
If plinth level is less than 900 mm.
Eve level bend is provided instead of lintel level bend if eve level is not more than 900mm above the door opening.
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.
Slide80Structure 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.
Slide81Structure Repairs & Rehabilitation
S.NoNo. Of StoreyStoreyCategory CCategory DCategory ESingle Bar in mmMesh G 10Single Bar in mmMesh G 10Single Bar in mmMesh G 10 NO. of wireWNO. of wireW NO. of wireW1.One---101030012144002.TwoFirst---101030012144003.Ground---121440016--4.ThreeSecond1010300101030012144005.First1010300121440016256506.Ground121440012144001625650
Vertical Belt At Corners & Junction of Rooms
G 10= 3.25 mm dia@ 25 mm; Transverse wire in mesh @ 150 mm.
c
/c
Slide82Structure 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
Slide83Structure 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.
Slide84Structure 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
Slide85Structure Repairs & Rehabilitation
Before applying compression in the wall it has to ensure that
Wall should not be low strengthening mortar.
It will be better to strengthen week wall by injection grouting first.
Slide86Structure 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
Slide87Structure 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.
Slide88Structure 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
Slide89Structure
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
Slide90Structure 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
Slide91Structure 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.
Slide92Structure 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
Slide93Structure 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
Slide94Structure Repairs & Rehabilitation
Connection of old brick work with new
150 mm
200 mm
220 mm
500 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
Slide95Structure Repairs & Rehabilitation
Connection of New brick wall with Stone Masonry
Brick masonry
Existing old Stone masonry
Slide96Structure 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
Slide97Structure Repairs & Rehabilitation
Strengthening Of Foundations
Introducing new load bearing members
Improving the drainage of the area to prevent saturation of foundation soil
Providing apron around the building to prevent soaking of foundation
Adding strong elements in the form of reinforced concrete strips attached to the existing foundation part of building
Slide98Structure 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
Slide99Structure 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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