Post on 02-Mar-2018
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Chapter-09
Masonry Structures underlater loads
Siddharth shankar
Department of Civil(structure)
Engineering
ulcho!k Campus
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Earthquake
Earth"uake cause shaking of ground# so a $uilding resting onit !ill e%perience motion at its $ase&
'he roof has a tendency to stay in its original position and the
roof e%periences a force# called inertia force.
nertia force is the multiplication of the !eight and theacceleration# so larger the !eight of the $uilding more the
earth"uake shaking&
Engineering representation of
earth"uake force
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Masonry Structures
Masonry is $rittle and tensile and shear strength
is very lo!&
Due to arge mass of masonry structures# heavy
!eight attracts large amounts of seismic forces&
*all to !all connection and roof connection is
generally !eak&
Stress concentration occurs at the corners of
!indo!s and doors&
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+ut of plane failure
n plane failure
Diaphragm failure Connection ,ailure
,ailure due to opening of !all
ounding
on-structural component failure
Failure Modes of a Masonry buildings
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Out of Plane Failure
'he Earth"uake force isperpendicular to the plane&
'he !all tends to overturn or $end&
'his causes the partial or full
collapse of the !all&'his is due to nade"uate anchorage
of !all and roof # long and slender
!all# etc&
Characteri.ed $y vertical cracks atcorner# cracks at lintel# roof level and
ga$le !all# etc&
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In Plane Failure
'he Earth"uake force is parallel to the plane
'he !all is shear off or $end/- cracks occurs
Characteri.ed $y vertical cracks at !all intersection#
separation of corners of t!o !alls# spalling of
materials# etc
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Diaphragm Failure
ack of anchoring produce a push of diaphragm against the!all&
$sence of good shear transfer $et!een diaphragms and
reaction !all accounts for damage at corner of !all
1are phenomenon in the event of seismic motion
Separation of !all and diaphragm cause collapse of $uildings
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Connection failure
,or given direction of earth"uake# !all acts as a shear!all and 2 acts as fle%ure !all&
f the !alls are not tied together !all 2 overturn (out of
olane) and !all slides (in plane) and collapse occurs&
Masonry units should tied properly
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Failure due to opening in alls
+pening !ill o$struct the flo! of forces from one !all toanother&
arge opening in shear !all reduces the strength of !all
against the inertia forces&
1esults diagonal cracks in the areas of masonry $et!eenopening and cracks at the level of opening&
'hus# openings should small and a!ay from corners&
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Pounding
*hen the roofs of t!o ad3acent $uildings are at differentlevels# during earth"uake# t!o $uildings strike against each
other is called pounding&
ounding results into cracking of the !all&
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!on Structural components failure
,alling of plaster from !alls and ceiling&
Cracking and overturning of parapets#
chimneys# etc&
Cracking and overturning of partition !alls&
Cracking of glasses&
,alling of loosely placed o$3ects&
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Ductile beha"iour of reinforced # unreinforced masonry
t is the capacity of an element or structure to undergo largedeformation !ithout failure&
Masonry is $rittle in nature&
Ductility of masonry structure is governed $y the ductility
of masonry units 4 properties of mortar&5nreinforced masonry cannot !ithstand tension so cracks
develops&
n-plane 4 out-of-plane failure is also due to ductility of
masonry&
'o improve ductility reinforcing $ars are em$edded in the
masonry# called reinforced masonry !hich can resist the
seismic force more than unreinforced masonry&
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$rittle and Ductile force%deformation beha"ior
$rittle
Ductile
6y 6uDeformation
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7& *alls tend to tear apart&
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8& *alls tend to shear off diagonally in direction&
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& ,ailure at corners of !alls
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:& *alls tend to collapse
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;& ,ailure at corners of openings
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pounding $et!een t!o ad3acent
$uildings
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?& Separation of thick !all into t!o layers
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@&Separation on unconnected !all at 3unction
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9&Seperation of !all from roof
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on-integrity of !all floor and roof& Configuration A irregularity of $uilding causes
torsional effect&
arge opening of the $uilding&
nappropriate position of opening&
ack of cross !all in large length of !all&
ack of reinforcement make the masonry $uilding
$rittle& ounding effect&
ack of anchoring element $et!een t!o !alls&
Ma3or causes of failure of masonry $uildings
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Elements of ateral oad
1esisting MasonrySystem
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&ori'ontal bands for integrity
Connecting peripheral alls forstructural robustness and integrity
Plinth band
(intel band
)oof band
*able band
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)oof structure
(ight and strong roof is
desirable+
Secure tiles,slates or use *I
sheets+
*ood -ointing in trusses
Concrete floors in ./0/1
concrete ith reinforcement
in both directions and bend
up near supports+
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Overall arrangement of masonrystructure
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Chapter-70
'esting of masonry
elementssiddharth shankar
ulcho!k CampusDepartment of Civil Engineering
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Compressive Strength of 2ricks and !all
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2esting of 3all in compression
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Diagonal Shear 2est
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!ormally carried out/7& eriodically to evaluate the performance of$uilding
8&'o gather information on old $uilding in
order to ascertain the methods of repair orto demolish
& 'o ascertain the strength of concrete ifcu$e tests failed&
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!O! DES2)4C2I5E 2ES2 6!D27 Elastic !ave tomography
1e$ound =ammer > Schmidt =ammer
5ltrasonic ulse Belocity
mpact Echo 'est
/-1ays
,lat ack 'est
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Elastic a"e tomography 'echni"ue used for locating shallo! delaminations#
cracks# and voids&
Elastic !ave tomography is $ased on t!o $asicprinciples from heat transfer conduction andradiation& Sound materials !ith no voids# gaps# orcracks are more thermally conductive than materialsthat are delaminated or contain moisture&
'his allo!s rapid areal mapping of internalconditions& t should $e noted that the ' method ismost useful for the detection of shallo! defects andfla!s&
2ests For/Boids# Cracks# Moisture&
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)ebound Method
Can $e used to determine the in-place compressivestrength of concrete !ithin a range of 7;00 A @000 psi
(70-;;Ma)
"uick and simple mean of checking concrete
uniformity&
Measure the distance of re$ound of a spring-loaded
plunger after it struck a smooth concrete surface&
1esults of the test can $e affected $y factors such assmoothness of concrete surface# si.e# shape# rigidity of
specimen# age 4 moisture condition&
'ype of coarse aggregate 4 the car$onation of the
surface&
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!ondestructi"e 2est
)e%bound hammer Method
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!ondestructi"e 2est Methods
1e$ound =ammer 'ests Schmidt =ammer
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1e$ound Method 5sing 1e$ound =ammer
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4ltrasonic Pulse 5elocity
t uses measurement of the speed of ultrasonic
pulses through the concrete to correlate concrete
strength to standard strength&
llo!s the determination of compressive concrete
strength and location of cracks&
t !ill identify non homogenous condition in the
structure such as honeycom$# voids and cracks&
Si.e of cracks can also $e determined&
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5ltrasonic ulse Belocity
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Flat 8ack 2est ,lat 3ack testing is a nondestructive test of
evaluating e%isting masonry structure& t does
not re"uire removal of masonry units - only
the removal of small portions of mortar isenough& 'he flat 3ack test uses small# thin#
hydraulic 3acks to apply a force to a section of
an e%isting masonry !all# and the methoduses measuring devices to determine the
resulting displacement of the masonry&
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,lat 3ack testing has many useful applications
t can $e used to determine masonry compressive
modulus# !hich is the stress>strain relationship of
the masonry# or a%ial stress $y applying a%ial load
and measuring resulting a%ial deformation& t can $e used to estimate compressive strength and
measure the shear strength&
f the destruction of the masonry units is accepta$le#it can $e used to directly measure the compressive
strength $y testing the masonry to failure&
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Flat%8ack 2est
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Push Shear 2est
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repare the test location $y removing the $rick#including the mortar# on one side of the $rick to $etested& 'he head 3oint on the opposite side of the
$rick to $e tested is also removed& Care must $ee%ercised so that the mortar 3oint a$ove or $elo! the
$rick to $e tested is not damaged&
'he hydraulic ram is inserted in the space !here the$rick !as removed& steel loading $lock is placed$et!een the ram and the $rick to $e tested so that theram !ill distri$ute its load over the end face of the
$rick& 'he dial gauge can also $e inserted in thespace&
Push Shear 2est
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'he $rick is then loaded !ith the ram until the
first indication of cracking or movement of
the $rick&
'he ram force and associated deflection on
the dial gauge are recorded to develop a
force-deflection plot on !hich the first
cracking or movement should $e indicated& dial gauge can $e used to calculate a rough
estimate of shear stiffness
Push Shear 2est
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