long span in concrete

8/9/2019 Long Span in Concrete

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LONG SPAN INCONCRETE

Advanced Building Techniques


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What exactly is Long Spa

The minimum span required to classify any stru

long span has been a topic for debate. The enBritannica sets the minimum value to 30 metre.! "hings boo# its $% metres& while many oth'ust de(ne it as a large unobstructed space. )o presentation we are going to e*plain the commof constructing slabs in concrete and also e*plo?


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Types o Conc!etesla" syste#s

+lat ,late

+lat )lab

Beam - )lab )tructu

ibbed /a1e2 )lab

Band Beam )ystem

)lab and oist )ystem ,recast "oncrete )la

"omposite 4oor slab

)hell )tructures


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$lat Plate

5ne6way or two6wayusually supported dicolumns or load bea

5ne of the most comforms of construction

7asy to construct

8reat 4e*ibility for lohori9ontal services asuspended ceiling.


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,ros )imple formwor# and

suitable for direct (* orsprayed ceiling.

:o beams;simplifyingunder64oor services.


6/57)teps in


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Reino!ce% $lat Plate & P!e'st!ess$lat Plate

0

>0

$00

$>0

?00

?>0

300

3>0@00

@>0

einforced +lat,late

e,la7co

,restressed +lat

,late

,re

,la7co

)pan

Thic#nessof

slab


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$lat Sla"

)imilar to +lat ,late bu

panels provided at the rop ,anels increase t

capacity and the stin4oor system under ve

thus increasing the ec

span range The plan dimensions o

panels are a minimumthe span in the directiconsideration& usually

the nearest $00 mm.


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,ros )imple formwor#

:o beams simplifyingunder64oor services outsidethe drops


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Reino!ce% $lat Sla" & P!e'st!esseSla"

)pan

Thic#ness/mm

2

0>0

$00

$>0?00?>03003>0@00

@>0

einforced +lat)lab

e)la7co

,restressed +lat

)lab

,re

)la7co


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(ea# an% Sla

consists of beams fra

columns and supporspanning between th

The relatively deep bprovide a sti 4oor clong spans& and able

lateral loads 5ne of the most com

used systems


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,ros Traditional eective

solution

=ong spans.

"ons ,enetrations through

large ducts diEcult to

epth of 4oor

8reater 4oor6to64oor

Types of commonl )


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Ri""e%)Wa*eSla" ibbed 4oors consisting o

spaced ribs are usually sudirectly by columns.

They are either one6way ssystems #nown as ribbed way ribbed system #nownslab.

The formwor# costs and trating.

ibbed slabs are suitable to heavy loads

"an span reasonable dista

Are very sti and particula

where the soEt is e*pose


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,ros )avings on weight and

materials

=ong spans

Attractive soEt appearance if

e*posed 7conomical when reusable

formwor# pans used

Dertical penetrations betweenribs are easy.

"ons equires special or pro

formwor# 8reater 4oor6to64oor h =arge vertical penetrat

diEcult to handle.


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Reino!ce% Ri""e% Sla"

)pan

Thic#ness/mm

2

0

$00?00

300

@00

>00

F00G00

%00

)ing

)ing7con


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(an% "ea# asla"This system consists of a ser

parallel& wide& shallow beamsband beams or thic#ened slathe 4oor slab spanning transvbetween the bands.

The 4oor slab is designed as

slab& with the shallow band bcarrying all loads from the sla

Band beams or thic#ened slaa two6way slab system.


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(an% "ea# aSla"

Banded6beam sy

economically vialengths from 3>and beyond .

The overall thic#band6beam is tyin. to $% in.

The width can vto $0 ft.

epending on thloads& the slab iin. to H in. thic#.

.

% "


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(an% "ea# aSla"

The primary purpose of thic#ening the slab is t

increased drape for the tendons that are band

region.

Increasing the drape allows larger upward pres

forces to counteract the load eects in the lon

epending on the span lengths andor the magthe loads& either non6prestressed or post6tensi

reinforcement is used in the slab in the direction perpendicul

bands.

Banded6beam systems are economically viablelengths from 3> ft to >0 ft and beyond.


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P!os

elatively simple formwor#

)hallow beams to allow

services to run under the4oor


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Sla" an% +oist Syste#

Wi%e

-oist#ay %e.n

-oist/ith

spacRi"sexcein2

This system consists of a slab

spanning between beams /whichspan between columns2 andusually an intermediate 'oist in one

direction.

+requently& the slab thic#nessbetween the 'oists is controlled by

requirements for (re6resistance. +or e*ample& a ?6hour (re

resistance rating requires a $?06

mm slab thic#ness& which is

capable of spanningappro*imately @ m.


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7conomy in construction is achieved throughcombinations of commonly available& reusabstandard 'oist forms. )tandard forms dimensmodules of @60J & >60J and F60J

,


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,ros Thin slab panels possible

)uits industrial structures

=ong spans

Dertical penetrationsbetween beams easilyaccommodated.

"ons


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Co#posite 3oo!st!,ct,!es

"omposite slabs com

reinforced concrete cof pro(led steel dec#acts as formwor# duconstruction and e*treinforcement

A% i i


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A%4antages o ,sing co#posite sla"s5

"omposite 'oists have been used to ma#e 4oor slabs e*ceeding a feet.

Ability to route mechanical NDA"& plumbing and electrical lines through '

7ase of moving NDA" during life of building

Better ,lenum space utili9ation

+loor6to64oor height can be reduced by not having to run mechanical 'oi'oists


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P!ecast Sla"

These systems consist of p

elements spanning one wainsitu or precast beams orbeam shells or other suita

The precast 4oor elementssimply supported before aconcrete is placed to compsystem.

,re6casting oers the advasite manufacture under faconditions and fast erectio

hen combined with pre6sadditional bene(ts of longhigh load6capacity can be


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Types o P!ecast

A number of dierent systemsincludingK

Nollow6core plan#s& either a topping.

"omposite 4ooring using ppermanent formwor# pane

"omposite 4ooring using pand in(ll.

)olid slabs either reinforcestressed.

)ingle and double T6beams


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(,il%ing Type

Nousing

7ducational 5Eces - "ommercia

Industrial

arehouses

Nospitals

oofs

"ar par#s

)uspended ground sl/heaving clays2

Notels


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Shell st!,ct,!

A shell structure is a

curved membrane ousually of reinforcedthat functions both astructure and coveri

Single o! %o,"le c,!4at,!


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Single o! %o,"le c,!4at,!shells )ingle curvature shells K are curved on one

a*is and are part of a cylinder or cone in thbarrel vaults and conoid shells.

ouble curvature shells K they are either psphere or a hyperboloid of revolution.


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T6PES O$ S7ELL STR8CT8RE


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$ol%e% Plate St!,ct,!es

,rinciple componentsK

The inclined plates 7dge plates which must be used to stien the wide plates

)tiners to carry the loads to the supports and to hold the p

"olumns to support the structure in air.

A%4antage 5 a folded plate structure may be formed in thas a hori9ontal plate structure and use less much lesser consteel for the same span.

C li % i l " l lt


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Cylin%!ical "a!!el 4a,lts

Barrel vaults are perhaps the most useful shell structuthey can span upto $>0 feet with minimum material.

They are very eEcient structures because the archedreduces the stresses ad thic#ness in the transverse d

9 l ti


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9o#es o !e4ol,tion

A dome is structure covering more or less suare or a carea.

It is a double curvature structure and stier than any with a single curvature.

,ros "ons


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,ros Dery light form of

construction. To span30m a shell thic#ness

of only F0mm isrequired.

ead load can bereduced economi9ing

the construction offoundations and

supporting systems. Arched shapes can

span even longer.

+lat shapes can be

obtained too by usingcertain arched shapes.

"ons )huttering can be a

8reater accuracy inis required.

)#illed labour and sis required.

The rise in the heigmaybe a problem.

h


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Why Conc!ete ?

+or the construction of shells concrete is the most suitabecause its a highly plastic material that can ta#e up acentering or inside formwor#.

)mall sections of reinforcement bars can be bent to follcurvature of the shell.

5nce the concrete hardens into the shape of the shell itrigid member that acts both as the structure and the cobuilding.?

Cente!ing o shells


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Cente!ing o shells

"entering is the necessary temporary support that is on which the rcc concrete shell structure is to be cast

The centering of a barrel vault is less comple* than thdome or a conoid as it has the same curvature along


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h d h f


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The )ydney opera house spans upto $F@ feet.

The arches are supported by over

3>0#m of tensioned steel cable.

The shell thic#ness goes from 3 to @ inches.

All shells weigh about $>tonne.

Th h ll i d i f b l


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The shells were perceived as a series of parabolas suprecast ribs& the formwor# for using in6situ concrete prohibitively e*pensive but because there was no repthe roof forms& the construction of precast concrete findividual section would possibly have been more e*

The design team went through at least $? iterations the shells trying to (nd an economically acceptable fschemes with parabolas& circular ribs and ellipsoids2 wor#able solution was completed. In the mid $HF$& tfound a solution to the problem.

The shells all being created as sections from a spher

allows arches of varying length to be cast in a commnumber of arch segments of common length to be plone another to form a spherical section.


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+AIP8R INTERNATIONAL CON:ENTAN9 E;7I(ITION CENTRE

"ase )tudy

= ( l b f 30 @0


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=ong span roo(ng slab of 30 m * @0m span.

5ne ay Beam and "olumn structure

> beams and $0 columns

:etwor# of primary& secondary and tertiary beams.

,rimary Beam si9e K $.3 m wide and ?.>m deep.

"oncrete used in slab is


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CO


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0

>

$0$>

?0

)paninm

etres

)ourceK 8uide to =ong )pan "oncrete +loors& ""AA


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T7AN= 6O8

,ra#har Direndra /0@%2

2

:ites

evi#a /

Avinash "hauhan /03@2

long span in concrete

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