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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

http://www.worldoftest.com/images/ndt/WM250.jpg

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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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