Structure Repairs & Rehabilitation Presentation

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Structure Repairs & Rehabilitation Presentation




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Presentations text content in Structure Repairs & Rehabilitation Presentation

Slide1

Structure Repairs & Rehabilitation Presentation

Presentation From

Slide2

Structure Repairs & Rehabilitation

Type Of Building Construction

A. Based On Construction Method

B.

Based On Design & Supervision

Slide3

Structure Repairs & Rehabilitation

A. Based On Construction Method

Load Bearing Wall With Step/Strip Footing

R.C.C. Frame Work

Precast Structural Frame Work

Slide4

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)

Slide5

Structure 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.

Slide6

Structure 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.

Slide7

Structure Repairs & Rehabilitation

Earthquake Effects on Soils & Foundations & Solution Features For Foundations

Type “I” Rock Or Hard Soil

-Well graded gravel Mixtures with or without clay binder, and clayey sands poorly graded or sand clay mixtures(GB,CW,SB,SW & SC) N>30

Type “II” Medium Soils-

All soils N= 10 to 30 & Poorly Graded Sands Or Gravely Sands with Little or No fines (SP) with N>15

Type “III” Soft Soils

Other than SP with N < 10.

Slide8

Structure 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.

Slide9

Structure 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

Slide10

Structure Repairs & Rehabilitation

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

Floor

Opening

Slide11

Structure Repairs & Rehabilitation

Torsion Irregularities are In floor plan like tilting or deformed or Both.Re-entrant Corner If A/L>0.15 to 0.2.

L

A

L

A

L2

A2

L1

A1

Slide12

24 m

A=18m

Structure

Repairs & Rehabilitation

Re- Entrant corner

Plan A

Plan B

Plan C

Plan D

Plan F

In Plan A, As per rule In Y-dir. A/L=18/24=0.75> 0.15 In X-dir. A/L=6/12=0.50> 0.15

12 m

Plan F

Slide13

Structure

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

Slide14

A

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

Slide15

Structure Repairs & Rehabilitation

Weak Storey (lateral Strength of Each storey vary F1 < 0.8 F2 (or F3 )

F1

F2

F3

Slide16

Structure Repairs & Rehabilitation

Redesigning existing structure for nature forces

It is a comprehensive task & require planning which include following Information gathering.

Field investigations including details of sub strata, foundation details, extent of damage

Type of Existing structure & its members stability

Design Data Collection

Identification of components required to be strengthened

Cost Estimates (it is feasible up to 60% of new construction)

Method or Procedure to be fallowed.

Slide17

Structure Repairs & Rehabilitation

Crack Investigation

Location

Profile (vertical, Horizontal, Diagonal)

Crack Size (Depth & length)

Slide18

Structure 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.

Slide19

Structure 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

Slide20

Structure 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.

Slide21

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.

Slide22

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

Slide23

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 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

Slide25

Structure

Repairs & Rehabilitation

Separation Sections to divide One

Building into more.

1

2

1

2

1

2

3

Slide26

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.

Slide27

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

.

Slide28

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.

Slide29

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

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

Slide31

Ld

Ld

≥300 mm

Structure

Repairs & Rehabilitation

Column Reinforcement

6mm Ø @ 150 mm

Middle 2/3

rd

of height

Slide32

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.

Slide33

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.

Slide34

Structure 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

Slide35

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.

Slide36

Structure Repairs & Rehabilitation

For Masonry Structures code consider following

Plinth Bend (if strata is soft, non-uniform)

Lintel level bend

Roof level/ Eve level/ Gable level bend

Reinforcement at corner of wall

Shape, Size & location of Window In Wall

Unsupported Wall length to Height Ratio

Cross wall, Brick Pillar, Buttress

Slide37

Structure Repairs & RehabilitationCyclone Obstructed by Retaining Wall

Cyclones

Slide38

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.

Slide39

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

Slide40

Structure Repairs & Rehabilitation

Believe it or not this wooden school did not crack or fall in Sikkim earth quack even it was neglected structure.

Slide41

Structure Repairs & Rehabilitation

Believe it or not this Ekra school did survive in Sikkim earth quack even it has been poorly built in as Plinth & ground is on same level.

Slide42

Structure Repairs & Rehabilitation

This slide shows joint of plinth beams at corner of column.

Due to no hook in many of bars in plinth beam ,whole of wall above plinth beam came out with the plinth beam at corner column in sikkim earth quack

Bar without hook

Slide43

Structure Repairs & Rehabilitation

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

Slide44

Structure Repairs & Rehabilitation

Higher plinth level with plinth protection

Slide45

h

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

Slide46

Structure Repairs & Rehabilitation

Table :Size, Position Of Opening In Above Figure

Description

Building Retrofitting Need/Category

Action For

Retrofitting, if code requirement not found satisfied

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

Slide47

Structure Repairs & Rehabilitation

Table :Size, Position Of Opening In Above Figure

Description

Building Retrofitting Need/Category

Action For

Retrofitting, if code requirement not found satisfied

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

Slide48

Structure 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

Slide50

Structure Repairs & Rehabilitation

Cracks are Cleaned by Air.

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

1

2

3

4

Beam

Crack

Slide51

Structure Repairs & Rehabilitation

S.No.

Item Of Roof/Floor

Requirement as per IS 4326

For School Building category

Retrofitting Action, if code provision not satisfied

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.

Slide52

Structure Repairs & Rehabilitation

S.No.

Item Of Roof/Floor

Requirement as per IS 4326

For School Building category

Retrofitting Action, if code provision not satisfied

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

Slide53

Structure Repairs & Rehabilitation

S.No.

Item Of Roof/Floor

Requirement as per IS 4326

For School Building category

Retrofitting Action, if code provision not satisfied

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.

Slide54

Structure 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.

Slide55

Structure Repairs & Rehabilitation

Beam Jacketing

New Bar

Beam Chipped Surface painted with epoxy

Shortcrete

Flooring Along Beam are removed

Column

Slide56

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.

Slide57

Structure Repairs & Rehabilitation

Strengthening of Cracked Wall

Sectional Elevation Of Wall

Clamps or Tie Rod connected to Wire Mesh along cracks

Crack wider than 5 mm

Grout Port

Wire Mesh (50mmx 50 mm Opening)

20x40 mm thick Mortar or Micro concrete

Slide58

Structure Repairs & Rehabilitation

School Buildings has to be construct as per Building Category “C”,”D”,”E” ( as per its EQ Zone). These Category define specific mortar for brick work & corresponding strength can be achieved by injecting grout in existing building walls. Same procedure is fallowed in cracked wall having crack width 0.5 to 5 mm with grouting port fixed along crack, spacing @ of wall thickness

Front Elevation

Side Elevation

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

Slide59

Structure Repairs & Rehabilitation

Strengthening of Multiple Cracked Wall

Sectional Elevation Of Cracked Or Week Wall

Tie Rods 300 to 400mm C/C connected to Wire Mesh along cracks

Crack Or Cracks > 5 mm wide

Grout Port Mortar(1:1) + Non Shrink Grout

Wire Mesh (50mmx 50 mm Opening)

20x40 mm thick Mortar or Micro concrete

Grout 1:1 + non shrink compound

Slide60

Structure Repairs & Rehabilitation

Cross Wall Connection Strengthening

t

≥2t

Drilled Hole

Tor Rod Grouted

Elevation Of Stone Masonry Wall

PLAN

Slide61

Structure Repairs & Rehabilitation

75 mm Hole is made carefully through R.R. masonry & S-shape bar is casted using small size aggregate concrete 1:2:4 with NSC or self (free) flowing readymade grout.

Fill the concrete from both side & then use non shrink grout

Curing for 10 days is must for such element

Temporary Support

Slide62

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

Slide63

Structure Repairs & Rehabilitation

0° Orientation of mesh

45° Orientation of mesh

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

Slide64

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.

Slide65

Structure Repairs & Rehabilitation

S.No

Classification Of Damageability Of Masonry Buildings

1.

Grade 1

: Negligible to slight damage ( no structural damage , slight non-structural damage)

a)

Structural

: hair line cracks in very few walls.

b)

Non structural

: Fall of small pieces of plaster only.

:

Fall of loose stones from upper parts of buildings in very few cases.

2.

Grade 2

: Moderate damage (Slight structural damage , moderate non-structural damage)

a)

Structural

: Cracks in many walls , thin cracks in RC slabs & A.C. sheets

b)

Non structural

:Fall of fairly large pieces of plaster , partial collapse of smoke chimneys

on roofs, damage to parapets , chajjas. Roof tiles distributed in about 10% of the area . Minor damage in under structure of slopping roofs.

Slide66

Structure Repairs & Rehabilitation

S.No.

Classification Of Damageability Of Masonry Buildings

3.

Grade 3

:

Substantial to heavy damage ( moderate structural damage, heavy non structural damage)

a

) Structural

: Large in extensive cracks in most walls. Wide spread cracking of column & piers.

b)

Non

Structural

: Roof tiles detach. Chimney fracture at the roof line : failure of non structural elements( partitions , gable walls).

4.

Grade 4

: Very heavy damage ( heavy structural damage , very heavy non structural damage) .

New construction may explore

.

For low strength masonry building use IS 13828.

Structural

:

Serious failure of walls (gaps in walls), inner wall collapse ,Partial structural failure of roofs and floors.

5.

Grade 5

: Destruction ( very heavy structural damage).

Total or near total collapse of the building.

For low strength masonry building use IS 13828 in zone IV

& V.

Slide67

Structure 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

Slide68

Structure 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.

Slide69

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.

Slide70

Structure Repairs & Rehabilitation

Damageability Grades Of Masonry Buildings

S.No.

Type Of Building

Zone II

(MSK

VI or less)

Zone III

(MSK VII)

Zone IV

(MSK

VIII)

Zone V

(MSK IX or More)

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)

Slide71

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

Slide72

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

Slide73

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

Slide74

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”

Slide75

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

Slide76

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

Slide77

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

Slide78

Structure 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.

Slide79

Structure 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.

Slide80

Structure Repairs & Rehabilitation

Procedure of Seismic belt Construction

1. Mark the belt on wall & remove the plaster in area.

2. Rack joint 20mm deep & wash with enough water.

3. Apply 15 mm thick 1:3 mortar immediately after washing . Make plaster sufficiently rough.

4. Fix mesh using binding wire & nail of 150 mm @ 450 mm c/c. If mesh is on both face of wall then use anchor to connect both mesh & grout the anchor.

5. Wet the first layer & brush with slurry before doing second layer of 15 mm thick plaster.

6. Do curing for 10 days.

Slide81

Structure 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

Slide82

Structure Repairs & Rehabilitation

Vertical Belt

t

t+600

B

150 mm

300 mm

200 mm wide Mortar belt

150 mm wide Steel Mesh held by wide head 150mm long nail

200 mm overlap in Steel Mesh on each face

Vertical Bar at corner of room

Slide83

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.

Slide84

Structure Repairs & Rehabilitation

Compressing The Walls for Box Action

ROOM PLAN

The Vertical Spacing of pre-stressing steel rods shall be 1/3

rd

& 2/3

rd

of the height of the wall from bottom. In case of slopping roof or pre fabricated element structure provide tie at middle at top of wall & at 1/3

rd

height.

In R.C. slab provide such tie only at mid height of wall

1 kg(f)/c.m.

2

pre stress is sufficient to compress the wall

Slide85

Structure 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.

Slide86

Structure Repairs & Rehabilitation

Strengthening of wall for making fit for compression for pre-stressing

Elevation OF Weak Masonry Wall

Cross Section

Nozzle for Injection Grout

Nozzle spacing 2 to 4 No. per sqm c/c; Grout 1 cement: 1 Water under pressure 1 to 3 kg/c.m

2

Slide87

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.

Slide88

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

Slide89

Structure

Repairs & Rehabilitation

Half Split Bamboo Ties To Rafter

Brace the Rafter to 50 mm Dia Bamboo (B)

Seismic Bend & Rafter should be tied Properly

X

Three

Nails 5Ø filled in member made by splitting bamboo in two part

B

Cross bracings at ends of room

Y

Y

Detail “Y” Refer Next Slide

Slide90

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

Slide91

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.

Slide92

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

Slide93

Structure Repairs & Rehabilitation

Stiffening flat wooden floor/roof Resting On stone or brick masonry

Wood Plank

Diagonal Ties

Tie Plank 100x 25 thick connecting joist & diagonal bracing

1.5 to 3.0 m thick G.I. flat

Wooden Joist

PLAN

Slide94

Structure 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

Slide95

Structure Repairs & Rehabilitation

Connection of New brick wall with Stone Masonry

Brick masonry

Existing old Stone masonry

Slide96

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

Slide97

Structure 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

Slide98

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

Slide99

Structure Repairs & Rehabilitation

Conclusion :

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


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