brick (bond and pattern)
TRANSCRIPT
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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
Expansion JointsExpansion Joints
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Expansion JointsExpansion Joints
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
Expansion JointsExpansion Joints
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
Expansion JointsExpansion Joints
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Expansion Problems Diagonal cracks often
occur between window and
door openings ifdifferential movement isnot accommodated
Expansion or control jointsat openings
Expansion JointsExpansion Joints
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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.
Expansion JointsExpansion Joints
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Expansion Problems Brick parapets are sensitive to temperature since they
are exposed to changing temperature on both sides
Expansion JointsExpansion Joints
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
Water IngressWater Ingress
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Reasons
Poor drainage around building
Water IngressWater Ingress
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Three Rules to Mitigate Water Ingress Good design
Provide barrier type wall
Provide weep holes and flashing Proper joint design
Water IngressWater Ingress
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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
Water IngressWater Ingress
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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
Water IngressWater Ingress
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Masonry Bondsasonry Bonds
Bonds and Patterns in MasonryBonds and Patterns in Masonry
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Bonds and Patterns in MasonryBonds and Patterns in Masonry
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
Bonds and Patterns in MasonryBonds and Patterns in Masonry
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
Bonds and Patterns in MasonryBonds and Patterns in Masonry
s tte s sBonds and Patterns in Masonry
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Structural bonds
Bonds and Patterns in MasonryBonds and Patterns in Masonry
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