Ann vii -structure repairs bihar

Structure Repairs & Rehabilitation In Low Strength

Masonry Buildings

Presentation From TSG

Structure Repairs & RehabilitationLow Strength Masonry Building is Laid in• Fired brick work in clay & mud mortar• Random rubble ; Uncoursed, Undressed stone

masonry in weak mortars made of cement-sand , lime-sand & clay-mud.

Structure Repairs & RehabilitationComponent Of Low Strength Masonry Building:• Foundation• Flooring • Brick/ Stone Columns• Brick Work• Stone Masonry• Wood Work• Slab • Slopping Wooden frame Roof • Plaster

Structure Repairs & RehabilitationLife Of Structure Depend Upon:

A. Geography Of Location

B. Building Material

C. Technology

D. Workmanship

Structure Repairs & Rehabilitation

A . Geography Of Location: • Type of Strata• Water Table• Earth Quack, Wind, Cyclone, Flood, Snow• Pollutant• Land Slide• Tree location w.r.t. building

Structure Repairs & RehabilitationB . Building Materials• Cement• Lime• Fine Sand• Coarse Sand• Coarse Aggregate• Quality of Water• Bamboo/Wood• Brick

Structure Repairs & Rehabilitation C. Technology • Architectural Design• Structural Design Based On Load Bearing Wall• Construction Methods• Quality Practices• Construction Management


D Workmanship• Structural Work • Finishing Work• Water Proofing Work• Development of Drainage (Internal &

External)• Maintenance Of Building

Structure Repairs & Rehabilitation Building Needs Repairs & Retrofitting• Crack & Spalling In Structural Members• Crack & Settlement In Flooring• Crack & Spalling in Non Structural Members• Leakage In Water Supply & Drainage System• Redesigning existing structure for nature

forces• Changed functional requirements


Crack & Spalling In Structural Members• Cracks Occur Due To Settlement In Foundation • Cracks Due To Earth Quack ,Wind• Crack Due To Overloading Of Structure• Crack Due To Reduction in Load Carrying

Capacity of Structure Due To Weathering• Crack Due To Improper Design Of Structure• Crack due to Poor connection Of Structural

Members Resulted From Poor Workmanship

Structure Repairs & RehabilitationCrack & Settlement In Flooring• Due To Improper Plinth Filling• In case of black cotton soil in foundation not replaced

up to sufficient depth by Good Soil under plinth (For generating enough Counter weight upon black cotton soil)

• Water Table vary within the Plinth Sub base (this occur in frequent flooding area & near sea soar)

• Improper curing, Improper laying, Poor Quality of workmanship.

• Improper design for loading i.e. thickness & type of flooring.

Structure Repairs & RehabilitationCrack & Spalling in Non Structural Members• Crack In Plaster• Crack In Finishing• Crack In Water Proofing Work• Vertical cracks in long boundary wall due to

thermal movement Or Shrinkage.• Crack Induced due to thermal changes,

change in moisture content in building material, Chemical Reactions

Structure Repairs & RehabilitationLeakage In Water Supply & Drainage• It may result from structural cracks & settlement• Improper selection of pipe thickness• Improper selection of Supports & its spacing to

Pipe• Improper making Of joints• Non Provision for contraction & expansion

(Particularly when pipe is passing over different type of long structures)

• Non Testing of Pipe before & after laying• Insufficient soil cover over pipe

Structure Repairs & RehabilitationRedesigning existing structure to meet functional requirement

as well as forces generated by NatureIt is a comprehensive task & require planning which include

following Information gathering.• Field investigations including details of sub strata,

foundation details• Type of Existing structure & its members stability• Design Data Collection• Identification of components required to be strengthened,

replaced.• Cost Estimates (it is feasible up to 60% of new construction)• Method or Procedure to be fallowed.


Crack Investigation• Location• Profile (vertical, Horizontal, Diagonal)• Crack Size throughout length (Width,Depth & length) Thin crack< 1mm Medium Crack >1 to 2 mm Wide Crack > 2 mm Crack may be non-uniform width. i.e. Tapper in

width(narrow at one end & wider at other end. )• Static or Live cracks

Structure Repairs & Rehabilitation• Cracks are static or live, is monitored & recorded

by “Tell-Tale” method

Crack in wall

Quick setting mortar or Adhesive

Crack in Glass strips

Glass strips of 2 to 3 C.M. in width & 10 to 12 C.M.in length

Widening Of Crack

Marking in Glass


These Crack occur around opening due to drying shrinkage & thermal movement in a building resulting weakening in the wall.


Expansion & thickening of roots creating concentration of stress at joints & weak locations such as openings

Structure Repairs & RehabilitationThe long horizontal crack resulted due to deflection of slab and lifting up of edge of the slab, combined with horizontal movement in the slab due to shrinkage.


This Cracks are due to pull exerted on the wall by the slab because of drying shrinkage and thermal contraction this pull results in bending of the wall which causes cracking at a weak section, that is, at the lintel or sill level of the window openings. Such cracks generally occurs when windows and room spans are very large. This cracks can be avoided by providing slip joints at slab supports on the walls.

Structure Repairs & RehabilitationConstruction Details Of Bearing Of R.C.C. Roof Slab

Over a Masonry WallConcrete Fillet

Brick tiles or Cement mortar with chequer grove finish

First Course Of parapet masonry is thicker than the wall By half Brick

12 mm wide groove in plaster

Slip Joint(two or three layer of tarred paper are placed over plastered surface)

12 mm Gap ,3/4 filled with Mastic Compound


Thickness of plaster is to much high & silt content is also Very High

Structure Repairs & RehabilitationLonger opening & less bearing & deteriorated lintel load capacity exposes diagonal crack which is widened towards corner wall edge.


Vertical crack under window occur when wall have large window opening & little wall space on both side of opening. Difference in stress due to more stress in wall portion adjoining to window & less stressed portion under sill of window results in crack.


Cantilever Chajja not having main bars on upper face

Structure Repairs & Rehabilitation When two adjacent walls shake in different

directions, their joint at corners comes under a lot of stress. This causes crack at the junction of two walls.

In Normal conditions, cracks in this location comes when one of wall expand more than short wall.

Structure Repairs & Rehabilitation When the long wall bends outward or inwards

vertically in the middle of its length, this stretching causes tension and causes vertical cracks in the walls.

Structure Repairs & Rehabilitation Similarly when the walls bends outward or inwards

horizontally in the middle of its height, this stretching causes tension and causes horizontal cracks in the walls. This happens

at the base of gable wall.

Structure Repairs & Rehabilitation Many times the wall gets pulled from its corners. This results in to tearing of wall in diagonal direction. In the wall if there is a window or a door, then the diagonal crack occur at their corners.

Structure Repairs & Rehabilitation Flexural Tension Cracks At Lintel Level Due to Shrinkage & contraction of R.C.C. Slab

Structure Repairs & Rehabilitation If the window is very large or if there are many doors and windows in a wall, then it tears even more easily in an earthquake.

Structure Repairs & Rehabilitation Many times the roof slides on top

of the walls on which it is sitting on

Structure Repairs & RehabilitationStructural RepairsLoad Bearing Walls: PROCEDURE IN NEXT SLIDE

CRACK IN BRICK

PLACING OF RCC BLOCK AFTER CUTTING HOLE IN B.W.

Structure Repairs & Rehabilitation Repairing Of Crack Due To Structural Cause• Replace all cracked bricks• Use R.C.C. Stitching Block In Vertical Spacing In

Every 5th or 6th Course ( 0.5 meter apart ).• Stitching block Width=equal to wall width, Length = 1.5 to 2 bricks, Thick =1 or 2 bricks as per severity of cracks• Mortar For Repairs 1:1:6 (1 Cement :1 lime: 6

sand)

Structure Repairs & Rehabilitation load bearing walls(May be Brick or Stone) have inbuilt

deficiency.• Each Brick have different strength• Thickness of Mortar Joints are not also uniform.• Bricks are not perfectly laid horizontally & vertically • Opening in walls• Improper staggered joints• Use of unwanted Brick bats1. These resulted in cumulative effect & concentration

of stress in particular section of wall is more than other section.

Structure Repairs & RehabilitationCorrective Measures For Load Bearing Wall Building• Therefore Shifting of Window, Door ,Inbuilt

construction of Almirah should be carried out with due consideration to IS code 13828:1993

• Proper Bearing to lintel over brick work to avoid diagonal cracks & it can be done in retrofitting work.

• It is advisable to keep window width as less as feasible while height can be increased with fixed glass pans on top portion as per slide 41.

Structure Repairs & RehabilitationImportance Factor(I) Depend Upon• Functional Use Of Structures• 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

h2

b5b4

b7

b8

h2

b2

h1b5

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

Retrofitting Need

b1

b4

b4

b6

l1 l2

b3

b4

t

h3

1222 1

3


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

A,B,C D`b6 (Minimum) 230 mm 600 mm(b1+b2+b3)/l1 ; (b6+b7)/l2 = 0.46 ( For one Storeyed

Building )

0.42 ( For one Storeyed

Building )

`b4 450 mm 500 mm`h3

(minimum)600 mm 600 mm

`b8 900 mm 900 mm

0.37 ( 2 & 3 storeyed 0.33 (2 & 3 storeyed Building)

Building)

150

Structure Repairs & Rehabilitation• Strengthening Of Window When Its Position Is

Not As Per Table Above Slide No 42. X X

Two Nos HYSD Bars

Section X-X

Window

6030

6 Ø @ 150

75

10 Ø

Structure Repairs & RehabilitationStrengthening Arrangements Recommended For low

Strength Masonry Buildingb = Lintel BendC = Roof Bend, Gable bendd = Vertical steel at corners & junctions of wallf = Bracing in plan at tie level of Pitched Roofsg = Plinth bandFor Building of Category ‘B’ in two storey

constructed with stone masonry in weak mortar, provide vertical steel of 10 mm dia in both storey.

Structure Repairs & RehabilitationStrengthening Arrangements Recommended For

Elements of low Strength Masonry BuildingBuilding Category

Number Of Storey Allowed

Strengthening To Be Provided

A One, Two, Three storey

`b, c ,f ,g

B One & Two Storey `b, c ,f ,gThree Storey `b, c, d, f, g

C One storey `b, c ,f , gTwo & three storey `b, c, d, f, g

D One & Two Storey `b, c, d, f, g

Structure Repairs & Rehabilitation• Seismic wave propagation increases as height

of wall/structure increases. • Seismic wave expansion 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 in falling of component of the building.

Structure Repairs & RehabilitationPossibility For Old Masonry Structures Strength• Plinth Belt in lieu of plinth band• Lintel level belt in lieu of band• Roof level/ gable level band• Corner steel• Shape, Size & location of Window In Wall• Wall length to Height Ratio• Cross wall/ Brick Pillar/counter fort

Structure Repairs & Rehabilitation Reinforced band on top of gable wallIt will reduce bending of gable wall

Structure Repairs & Rehabilitation In long walls introduce buttress

to strengthen it.

Structure Repairs & RehabilitationLow Strength Masonry Building Retrofitting

For Brick Masonry Structure • Height of the building in B.W. shall be restricted to the

following.1. For retrofitting category of building A,B,C up to3 storey

with flat roof or 2 storey plus Attic for pitched roof.2. For category D up to 2 storey with flat roof or one storey

plus Attic for pitched roof. where each storey height shall not exceed 3.0 m. Cross wall

spacing should not be more than 16 times the wall thickness CONTD.

Structure Repairs & Rehabilitation 3. Minimum wall thickness in brick masonry shall be

one brick for one & two storey construction, while in case of three storey, the bottom storey wall thickness is one & half brick.

4. Use brick from kiln only after 2 weeks when work is in summer & 3 week when work in winter.

5. Use leaner mortar preferably also adding lime for repairing cracks in particular& in masonry in general. It can be 1:1:6,1:2:9,1:3:12 as per need.

Structure Repairs & Rehabilitation For Stone Masonry• Height of the building in Stone Masonry shall be restricted

to the following1. For retrofitting category of building A,B,—2 storey with flat

roof or 1 storey plus Attic for pitched roof .In case cement sand mortar 1:6, the building up to 2 storey plus Attic for pitched roof.

2. 2. For category C,D– 2 storey with flat roof or 2 storey plus Attic for pitched roof with Cement sand mortar or 1 storey plus Attic for pitched roof with lime- sand or mud mortar.

CONTD.


3. Maximum wall thickness in stone masonry shall be 450 mm & preferably 350 mm. ,• Each storey height shall not

exceed 3.0 m and span of walls between cross wall is limited to 5.0m

Structure Repairs & Rehabilitation• Cross wall connection In steps

600 mm

600 mm

FIRST LIFT

SECOND LIFT

Structure Repairs & Rehabilitation Wall to wall joints are to be madeby building wall ends in steps form

Structure Repairs & Rehabilitation Vertical reinforcement within the masonry in corners increases wall’s capacity to withstand

Horizontal cracks due to bending.

In Each Layer Staggered Toothed Joint Y A B X PLAN

450 mm


230 mm

115 mm

230 mm

A B

View-X At A-A View- Y At B-B

Elevation Showing Vertical Joints In Staggered Layer

Structure Repairs & RehabilitationRecommended Longitudinal steel in Reinforcement

Concrete BendsSpan of Band Between Cross Wall

Building Category

“B”

Building Category

“C”

Building Category

“D”

Building Category

“E”

In MM No. Of Bars

Dia. Φ MM

No. Of Bars

Dia. Φ MM

No. Of Bars

Dia. Φ MM

No. Of Bars

Dia. Φ MM

5 or Less 2 8 2 8 2 8 2 106 2 8 2 8 2 10 2 127 2 8 2 10 2 12 4 108 2 10 2 12 4 10 4 12

Spacing Of Tor Ring/Links 6 mm @ 150 mm Or 8 mm @ 200 mm

Bands Thickness vary 75 mm for 2 bars & 150 mm for 4 bars

Structure Repairs & Rehabilitation• Steel Profile In Band At Corner & Junction

Lap= 50 ф Staggered

900 mm For Second Height

600 mm For First Height

Structure Repairs & Rehabilitation Bonding Elements A. Wood Plank ( 38x38x450 mm) B. R.C.C. Block (50x50x450 & 8 mm) C. 8 or 10 mm Hook or “S” shape bent Bar

Plan showing Through StoneThrough stone = Bonding Element

≤ 1200 ≤ 1200

≤ 1200

≤ 450Pair of stone with length= ¾ of wall thickness

Structure Repairs & Rehabilitation“S” shaped steel rod placed in a through hole in random

rubble wall and fullyencased in concrete


Plan showing Center bar in CasingCasing in every 0.6 m is lifted & M15 or

Mortar 1:3 is Compacted around bar.

≤ 1200 ≤ 1200

≤ 1200

≤ 450Pair of stone with length= ¾ of wall thickness

CL

•

• 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 drilled in member made by splitting bamboo in two part

B

Cross bracings at ends of room

Structure Repairs & Rehabilitation Diagonal tying on the upper or underside of the

roof Prevents roof from getting distorted and damaged

Structure Repairs & Rehabilitation Installing multiple strands of galvanized iron wires pulled and

twisted to pretension

Structure Repairs & RehabilitationVertical steel at corners and junction of walls up to 350 mm thick should be embedded in plinth masonry of foundations, bands, roof slab as per table

Nos Of Storey Storey Diameter Of H & D Single HYSD Bar in mm at each critical Section (for above 350 mm, increase bar dia proportionally

Category C Category D One -------- Nil 10

TwoTop 10 10

Bottom 10 12

Three

Top 10 10

Middle 10 12

Bottom 12 12


One Brick Thick One & Half Brick Thick -------- Contain One Bar At Centre

3/4B

Structure Repairs & Rehabilitation Seismic Belts & closing a opining with pockets made

in jams of masonry.

Pockets

Structure Repairs & RehabilitationEncasing masonry column in cage of steel rods

and encased in micro concrete.

Structure Repairs & Rehabilitation Anchoring the roof rafters and trusses with steel angles or other means

Structure Repairs & Rehabilitation Weld mesh belt approximately 220mm wide allaround the openings and anchored to masonry wall and encased in cement mortar

Structure Repairs & Rehabilitation Vertical deformed steel encased in concrete bar

from foundation to roof, anchored to both masonry walls at wall junctions with special connectors.

Structure Repairs & Rehabilitation Seismic belt in lieu of Seismic Band is made of weld mesh approximately 220mm wide anchored to masonry wall and

encased in cement mortar.

Structure Repairs & Rehabilitation Use smaller glass panes for windows Prevents the

shattering of glass in earthquake and cyclone

Structure Repairs & Rehabilitation Anchoring roof to wall &, reducing roof

overhangs,prevent the roof from getting blown off

Structure Repairs & Rehabilitation Prolonged flooding can weaken the mortar,

especially if it is mud mortar, and hence,the wall, causing cracking in walls or collapse.

Structure Repairs & Rehabilitation If the ground is sandy in which the foundation is sitting, then high speed flood/surge water can scour the land

around and under the foundation of your school, leading to settlement and/or cracking of the wall.

Structure Repairs & Rehabilitation Simple erosion of wall near its bottom, or cracking,

plaster peeling off and settlementin floor.


Lack Of foundation & plinth

Wall to high & too Long

Openings to closer to corner

Door & Window Opening to large

Deficient bearing length of lintels

Too small Projection

More Than One Story Building

Leaking Roof

Exposed walls without plaster or Pointing

Vertical Joint Without Mortar

Unbroken joint at corner

Structure Repairs & RehabilitationExtensive cracking of walls caused by differential settlement due to flood

Structure Repairs & Rehabilitation High plinth level to avoid entering flood


Foundation & plinth

Use band below roof truss/rafter

Damp proof at Plinth

Buttress in long wall

Low height wall Maximum 8 times thickness

If thatch is used, cover with waterproof mud plaster

Projected Roof Maxm 0.5 m

Opening 1.2 m From Corner

Good bonding Mortar

Waterproof mud plaster or cement plaster

Use of pilasters strengthens walls against flowing water


• This Presentation was focused on Low Strength Masonry Buildings therefore for framed structures & rich cement mortar building ,certain slides are in-valid. In next Presentation this balance portion will be highlighted.

• This Presentation was aiming to provide some technical input to site peoples so that we could point out any doubtful detailing in drawings to Structural/Architectural Designer.

• It is possible that features of Flood, Heavy Rain fall, Cyclone, earth quack may collide but We have to look priority of our geographical requirement.

Thank You

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Ann vii -structure repairs bihar