brick (bond and pattern)

8/3/2019 Brick (Bond and Pattern)

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Masonry Movement& Bond Patterns

Durgesh C. RaiAssociate Professor

Department of Civil Engineering

Indian Institute of Technology Kanpur

Kanpur - 208 016


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Movementovement


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effects of Movementeffects of Movement

Building elements in state of constant motion Change in volume due to internal/external stimuli

Temperature

Moisture Elastic deformations due to loads

Creep

Cementitious materials shrink and creep Clay masonry expands

Consider differential movements relative to steel orconcrete frames


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Restraining these movements causes stresses Resulting in cracks

To avoid cracking

Minimize volume change

Prevent source of movement

Accommodate differential movement betweenmaterials

Design movement joints by estimating thesemovements

effects of Movementeffects of Movement


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Temperature MovementTemperature Movement

Surface temperature can be higher thanambient temperature

Governing factors

Orientation

Wall type

Colour

Dark south facing wall surface temperature can beas high as 60C for mean ambient temperature37.7C


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Unrestrained thermal movement is product of Temperature change

Coefficient of thermal expansion

Length of element

Thermal Coefficient

(2.5 to 3.6)10-6/F Clay Masonry

(4.3 to 5.2)10-6/F Concrete Masonry

(4.4 to 7.3)10-6/F Stone(4.5 to 6.0)10-6/F Concrete

(6.5 to 12.8)10-6/F Metals (Fe, Al)

Temperature MovementTemperature Movement


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Moisture MovementMoisture Movement

Bricks expand slowly over time uponexposure to moisture

Brick units is smallest when it is cooled after kiln

Expands quickly over first few weeks

Depends on

Raw Materials Firing Temperature (low temperature expands more)


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Moisture MovementMoisture Movement

Clay Brick Masonry Long-term moisture expansion strain is 0.02%

Moisture induced volume changes not alwaysreversible

Concrete Masonry Units

Susceptible to shrinkage Depends on

Shrinkage Potential

Humidity

Linear shrinkage % varies from 0.03-0.065 dependingon moisture content


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Expansion JointsExpansion Joints

Joints should be placedAbrupt change in wall height

Any change in thickness of wall

Movement joints in floors, roofsand foundation

One or both sides of window/dooropenings


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Control joints To control cracking from shrinkage of CMUs

Pressure relieving or expansion joints

To control expansion of masonry joints

ACI recommends the following joints spacing

Recommend control Vertical spacing of joint steel Joint spacing (in.) - 24 16 8

Panel length/height 2.0 2.5 3.0 4.0

Panel length 40 45 50 60



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In brick masonry Width and spacing of expansion joints

W=[0.0002 + 0.0000045(Tmax

-Tmin

)]L {inches}

S= 24000/(Tmax-Tmin)p {feet}p is ratio of opaque to gross wall area

Tmax

and Tmin

in F

L is length of wall (in.)


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Details


Copper Foam Rubber

Extruded PlasticNeoprene

Expansion Joint


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Expansion Problems Diagonal cracks often occur between window and

door openings if differential movement is not

accommodated



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Expansion Problems Diagonal cracks often

occur between window and

door openings ifdifferential movement isnot accommodated

Expansion or control jointsat openings



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Expansion Problems Opposing moisture

expansion of brick and

curing shrinkage ofconcrete slab(foundation) can causecracking at buildingcorners if differential

movement is notaccommodated.



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Expansion Problems Brick parapets are sensitive to temperature since they

are exposed to changing temperature on both sides


Elongation will belonger than for wall

below

Roof

Parapet


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Water Penetration in Brick Walls Reasons

Most single wythe walls leak

Water passes through head joints and intersections of headand bed joints

Water ingress through joint lamination (avoid high IRA)

Units do not leak until internally cracked

Water IngressWater Ingress


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Reasons

Joint profiles: concave vs. raked

Poor workmanship

Rough joints with voids



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Reasons

Poor drainage around building



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Three Rules to Mitigate Water Ingress Good design

Provide barrier type wall

Provide weep holes and flashing Proper joint design



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Three Rules to Mitigate Water Ingress Proper materials

Low IRA units

Non-corrosive flashing

High Quality Workmanship

Pre-wet bricks with high IRA

Lay units soon after laying mortar

Dont furrow bed joints deeply

Filled head joints and tight bed joints

Keep drainage space clear of mortar



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Remedies of Leaky Walls Ideal solution

Demolish, re-design and re-construct

Alternative Cost-effective solution Re-pointing of mortar joints and filling cracks

Colourless coatings

Use with caution

May not prevent leakage

Efflorescence problems

Units may spall or disintegrate

Subsequent re-pointing requires re-coating



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Masonry Bondsasonry Bonds

Bonds and Patterns in MasonryBonds and Patterns in Masonry


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Bond Structural Bond

Method by which individual

masonry units are interlocked ortied together to cause entireassembly to act as a singlestructural unit

Pattern Bond Pattern which bricks and mortars

joints make on face

It can be due to structural bond/or purelydecorative one

Mortar Bond

Adhesion of bricks to the mortar

Bed joints

Head joints

Collar joints


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Structural bonds Three methods

Overlapping (interlocking ) the masonry units

Metal ties embedded in connecting joints

Adhesion of grout to adjacent withes of masonry

Overlapped bonds

Variation of two traditional methods of bonding English Bond

Alternate courses for headers and stretchers

Flemish Bond

Alternate headers and stretchers in every course

Pattern so arranged appears as headers and stretcher arranged

in vertical lines


s tte s s


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Structural bonds Stretcher develop longitudinal bending strength

Header develop transverse bonding strength

Building code requires

4% of wall surface composed of headers and distance

between adjacent headers not exceeding 600 mmhorizontally and vertically

Common (American) bond has Header course every fifth course (sixth or seventh)

Header course is started with (three quarter brick)

Dutch bond is variation of English bond in which stretcher coursein alternate course do not align vertically


s tte s sBonds and Patterns in Masonry


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Structural bonds


English bondEnglish bond


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Odd Layer

Elevation

Brick arrangement in the alternativelayers

Even Layer

Odd LayerEven Layer

Odd Layer

Even Layer

Odd Layer

Even Layer

Credits: CVR Murty

English bondEnglish bond

Flemish bondFlemish bond


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Elevation

Brick arrangement in the alternativelayers

Odd Layer

Even Layer

Odd Layer

Even Layer

Odd Layer

Even Layer

Odd LayerEven Layer

Flemish bondFlemish bond

Credits: CVR Murty

ConnectorsConnectors


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Less nos. of

connectors

More nos.

of

connectors

Flemish

Bond

EnglishBond

-- IndicatingIndicating Connectors (Headers)Connectors (Headers)

ConnectorsConnectors

Credits: CVR Murty

Corner with English bondCorner with English bond


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Arrangementof bricks in theodd layers

Arrangement ofbricks in theeven layers

Credits: CVR Murty

Corner with English bondCorner with English bond


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Arrangement of bricks in

the odd layers

Arrangement of bricks inthe even layers

Credits: CVR Murty

cross with English bondcross with English bond


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Arrangementof bricks inthe odd layers

Arrangementof bricks in theeven layers

Credits: CVR Murty


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Indian Standardson MasonryIndian Standardson Masonry

Indian StandardsIndian Standards


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Masonry related IS:1905-1987 Code of Practice for Structural Use of Unreinforced Masonry

(3rd Revision 1961, 1969)

IS:1077-1986 Specifications for Common Burnt Clay Building Bricks

IS:2212-1962

Code of Practice for Brickwork IS:2185-141 & 142

Specifications for Concrete Masonry Units (Solid and Hollow)

IS:3952-1978 Specifications for Burnt Hollow Clay Blocks

IS:3316-1974 Specifications for Stones (in regular size)

IS:2250-1981 Code of Practice for Preparation and Use of Masonry Mortar

brick (bond and pattern)

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