lintels and arches 2 (1).pptx
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Arches and Lintels
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Lintels and Arches
Lintels and arches are structural members
designed to support the load above
openings.
Transmit superimposed loads to walls
adjacent to the openings.
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Lintels
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Introduction
A lintel is defned as a horizontal structuralmember which is placed across the opening.
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lassifcation o! Lintels
Lintels are classifed according to thematerials o! their construction"
#1$ Timber lintels
#%$ &tone lintels
#3$ 'ric( lintels
#4$ )ein!orced 'ric( lintels
#*$ &teel lintels
#+$ )ein!orced cement concrete lintels
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Timber lintels Locall, available
)elativel, costl,- structurall, wea( andvulnerable to fre.
asil, deca,- i! not properl, ta(en care.
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&tone Lintels
/sed - where stonesare easil, available.
onsists o! a simplestone slab o! greaterthic(ness.
0igher cost
annot with standtensile loads.
&T2 LITL
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&tone Lintels
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'ric( Lintels
0ard- well burnt -
frst class bric(sare used.
&uitable !or small
span.
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)ein!orced 'ric( Lintels
6or large spans andheav, loads
The, are rein!orced with
mild steel bars. 7er, common due to
durabilit,- strength andfre resisting properties.
8oints are flled withcement concrete.
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)ein!orced 'ric( Lintels
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&teel Lintels :rovided at large
opening and where thesuper;imposed loadsare heav,.
)olled steel joists or Isections are used .
ither used singl, or in
combination o! two orthree units.
8oint with bolts.
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)2LL< &TL 82I&T
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)ein!orced ement oncreteLintel
ommon in use.
The, ma, be pre;cast.
6or smaller span- the
pre;cast concrete
lintels are used.
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Arches
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A)0& The structure
constructed o!wedge shaped bloc(o! stones or bric(s
-jointed togetherwith mortar andprovided across the
opening to carr, theweight o! thestructure above the
opening. 1*
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'asic concept; Arch action An arch is a pure compression member.
It can span a large area b, resolving !orces intocompressive stresses and- in turn eliminating tensilestresses. This is sometimes re!erred to as archaction.
As the !orces in the arch are carried to the ground-the arch will push outward at the base- called thrust.
As the rise- or height o! the arch decreases- theoutward thrust increases.
In order to maintain arch action and prevent thearch !rom collapsing- the thrust needs to berestrained- either with internal ties- or e=ternalbracing- such as abutments.
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L>T& 26 A)0& 1
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T0IAL T)>&
The various technical terms used in arches areas !ollows";
1?Abutment";This is the end support o! an arches.
%?:ier";This is support an intermediate o! an arch.
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3?Intrados";This is the inner curve or sur!ace o!an arch.
4?=trados";This is the outer curve or sur!ace o!the arches.
*?7oussoirs";The voussoirs or arch stones arethe wedge shaped units !orming the arch.
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+?& i i t Th i i t
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+?&pringing stone";The springing stone orspringer is the frst voussoir at springing levelon either side o! the arches.
?&pringing line";This is an imaginar, line joiningthe two springing points.
?rown";This is the highest point o! e=trados orit is the highest part o! an arches.
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5?@e,stone";This is the highest central wedgeshaped bloc( o! an arch.
19?&(ew bac(";This the sur!ace o! the abutmenton which the arch rests.
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11?&pan";This is the clear horizontal distancebetween the two supports.
1%?)ise";this is the vertical distance between
highest point on the intrados and the springingline.
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14?0aunch o! an arch";This is the portion o! arch
situated centrall, between the (e, and s(ew
bac(s.
1*?&pandril";This is the curved triangular
enclosed b, the e=trados o! the arch- ahorizontal line !rom the crown o! the arch and
perpendicular line !rom the springing o! the
outer curves.
1+? &ot"; It is the inner sur!ace o! an arch
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6ailure o! an Arch
ver, element o! arch remains in compression. An arches !ail due to";
1?rushing o! the masonr,.
%?&liding o! voussoirs.3?)otation o! some joints about an edge.
4?/neven settlement o! an abutment or pier.
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1. rushing o! the masonr,
I! the compressive stress e=ceeds the sa!e
crushing strength o! the masonr, unit and
mortar - the arch will !ail in crushing.
The material should be o! adeBuate
strength and size o! voussoirs and should
be properl, designed to bear the thrust
transmitted through them.
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%. &liding o! 7oussoirs
To sa!eguard against sliding o! voussoirs past each
other due to transverse shear -the voussoirs o!
greater height should be provided.
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3. )otation o! some joint about an edge )otation can be prevented -i! the line o! resistance is
(ept within intrados and e=trados. Also- the line o!
thrust should be made to cross the joint awa, !rom
the edge to prevent the crushing o! that edge.
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4. /neven settlement o! an abutment orpier
/neven settlement o! abutment -which causes
secondar, stresses in arch.
0ence- the abutment which has ultimatel, to bear all
the load trans!erred to the arch - should be strong
enough.
Also- the arch should be s,mmetrical - so thatuneBual settlements o! the two abutment is
minimised.
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lassifcation o! Arches
An arch ma, be classifed according totheir"
1?>aterial o! construction and wor(manship
%?&hape o! curve !ormed b, their sot or
intrados
3?umber o! centers.
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LA&&I6IATI2 'A&< 2 >AT)IAL AA&0I:
BRICK ARCHES
*Rough brick arches
*Axed brick arches*Gauged brick archesSTONE ARCHES
*Rubbe arches
*Ashar archesCONCRETE ARCHES
*!recas" co#cre"e bock arches
*$o#oi"hic co#cre"e arches 39
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')I@ A)0&
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)2/D0 ')I@ A)0&
These arches are built withordinar, bric(s- which are
not in wedge shape .
>ade up o! rectangular
bric( that are not cut into
wedge shape. urvature
are obtained b, mortar.
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AE< ')I@ A)0&
'ric(s are cut to wedge;
shape.
8oints o! arches are o!
uni!orm thic(ness.
ot dress fnel, so it
does not give muchattractive appearance.
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DA/D< ')I@ A)0& Accuratel, prepared to wedge shape.
&peciall, shaped bric(s (nown as F)/'')
')I@&G are used .
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&T2 A)0&
3*
)/''L A)0&
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)/''L A)0& >ade o! rubble stones- which are hammer
dressed- roughl, to the shape and size o!voussoirs o! the arch and f=ed in cementmortar.
These arches are used !or small span upto 1 m.
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A&0LA) A)0& &tones are cut to proper
shape o! voussoirs and
are !ull, dressed-
properl, joint with
cement or lime.
The voussoirs made o!
!ull thic(ness o! the
arch.
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2)T A)0&
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:)A&T 2)T 'L2@
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:)A&T 2)T 'L2@A)0&
/sed !or smallopenings inbuilding.
The voussoirs- in
the !orm o! cementconcrete bloc(sare prepared inspecial moulds .
Denerall, - theconcrete bloc(sare used without
rein!orcement.35
>22LIT0I 2)T
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>22LIT0I 2)TA)0&
onstructed !romcast;in;situconcrete -either plainor rein!orced -depending upon thespan and magnitudeo! loading.
Huit suitable !or largerspan 3.9 m?.
The curing is done %to 4 wee(s.
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lassifcation according toshape
6lat arch
&egmental arch
&emi;circular arch)elieving arch
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6LAT A)0
Acts li(e a lintel-when it providedover the opening .
8oints radiated tocenter.
/sed onl, !or lightloads onl,.
&pan up to 1.*9 m.
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6LAT A)0
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&D>TAL A)0
&egmental in shapeand provided over theopenings.
8oints radiate !rom acenter o! arch- whichlies below thespringing line.
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4*
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&>I;I)/LA) A)0 The shape o! the curve given to the arch
sot is semi;circular.
The center o! the arch lies on the springingline.
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&>I I)/LA) A)0
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&>I;I)/LA) A)0
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)LI7ID A)0
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)LI7ID A)0
Chen wooden lintel
is provided over the
wider opening- a
bric( relieving arch is
constructed above
the lintel.
)elieving the load o!
masonr, over lintel.
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02)& &02 A)0 0as a shape o! a horse shoe- incorporating
more than a semi circle
:rovided mainl, !rom architecturalconsiderations
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*1
: i t d A h
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:ointed Arch
Also (nown as Dothic arch
onsists o! two arcs o! circles meeting atthe ape=
Triangle !ormed ma, be eBuilateral or
isosceles
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LA&&I6IATI2 'A&< 2
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LA&&I6IATI2 'A&< 2/>') 26 T)&
O#e ce#"red arch.
T%o ce#"red arch. Three ce#"red arch.
&our ce#"red arch.
&i'e ce#"red arch.*4
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2 T)< A)0
&egmental- semi circular- Jat arches come under this categor,.
:er!ectl, circular arch (nown as bulls e,e arch provided !or
circular window.
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*+
TC2 T)< A)0
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TC2 T)< A)0
:ointed- semi;elliptical arches comeunder this categor,.
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T0) T)< A)0
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T0) T)< A)0
lliptical arches
come under this
categor,.
21-2% and 23
are the center.
*
21
2%23
62/) T)< A)0
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62/) T)< A)0
It has !our centers.
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6I7 T)< A)0
This t,pe o! arch -having fve centreMs-gives good semi;elliptical shape.