Const of Pre Fab

8/12/2019 Const of Pre Fab

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PAPER PRESENTATION ON

By

T.V.M.AKHILASH GUPTHA S.DEVI PRIYANKA

E-mail: akil143.akil!mail."#m P$iya%&ami1'3ya(##."#m

3)4 B.T*"( S+,*+&

SRI SUN/L0ER 20LLEGE 0/ ENGINEERING TE2HN0L0GY

LANKAPALLI KRISHNA .Di&+
mailto:[email protected]:[email protected]


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ABSTRACT:In todays world, where speed and convenience play a big part in influencing the use ofany product, the age of prefabricated housing products sees to have finally arrived!The usefulness of these products help significantly in speeding up construction byoffering ready"to"install building eleents such as bloc#s , $oist beas, roof bloc#s and

panels is being widely recognised in the industry! %re"fabricated coponents arebecoing iensely popular due to the several attractive advantages that they offer,such as off"site fabrication, which allows reduction in construction tie and this functionhelps greatly in anaging the schedule of the construction pro$ect! &ue to their lowdensity, the prefabricated coponents ipose a relatively lighter load on the structureand superior 'uality can also be achieved as these coponents are anufacturedunder a strictly controlled environent! In recent ties few innovations in thefield of aterials are e(pected to a#e these products even ore popular, userfriendly and eco friendly! The present paper discusses on the anufacturing of

prefabricated building coponents using fly ash, and e(plains regardingfabrication, centring, placing, applications and the advantages over the onolithic

construction!This paper aims to popularize the promotion of prefabrication building ethodologies

for low cost housing by highlighting the different prefabrication coponents and

techni'ues, and the econoical advantages achieved by its adoption!

)! I*TR+&CTI+*:)!) %refabrication: -%refabrication. is the anufacture of coponents cast in a factory oron site before being placed in position, assebling the structural units so that they canbe easily and rapidly erected! %refabricated buildings are pre"cut, pre"drilled, and pre"engineered before the actual building is constructed! %refabricated Structures/%0S1 are

useful for sites, which are not suitable for noral construction ethods such as hillyregions, and also when noral construction aterials are not easily available!Structures which are used repeatedly and can be standardi2ed such as ass housing,storage sheds, godowns, shelters, bus stands, security cabins, site offices, foot overbridges, road bridges, concrete building bloc#s etc!, are prefabricated structures! This

paper discussing about the i( proportions f the aterials to anufacture the prefabcoponents and the construction procedure for an ordinary single story residentialbuilding!

)!3 Criteria for selection of prefab in India:In India, the technology adopted for housing coponents should be of the order

that, the production and erection technology be ad$usted to suit the level of s#ills andhandling 0acilities available under etropolitan, urban and rural conditions! In otherwords, the structural systes and coponents selected should ensure iniuaterialtili2ation with a(iu structural advantage! 4owever, the coponent and systesso designed are to be anufactured and erected by anual eans in villages, seiechanical techni'ues in towns and ore or less fully echanical operations in theetropolitan cities! In urban areas, the concentration of construction activity does not


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$ustify prefabrication! A wide variety of roofing ethods to suit these re'uireentshave been developed and used on ass scale in any housing pro$ects such asfunicularshell, cored slabs, RCC channel units, precast cellular units, precast RC plan#s and

$oists, prefab bric# panels and $oists, RCC $oists and hollow concrete bloc#s!

)!5 6aterial used for %refabrication:%refabricated coponents can be anufactured using any aterials, dependsup on the type of structure! 7enerally aterials used are 8ood, Steel, concrete, plasticand coposite aterials !If the structure is wooden house then prefabricated wooden

panels, coluns, posts are used! If the structure is prefabricated steel truss bridge thensteel ebers li#e angles, I, 9"sections and rives, bolts are used! If the structure ishouses in developed countries then the prefabricated plastic internal partition walls,doors, panels and toilets are used! The an ade roc# concrete is also widely used forthe anufacturing of the prefabricated ebers! Instead of using coplete ceentconcrete we are replacing the soe 'uantity of ceent with an industrial waste product

li#e flyash! Because of adding the flyash we can get any benefits for the environentas well as prefabricated structure! Before going for the advantages of it, first #now the

properties of the flyash!

)! 0ly Ash:0ly Ash is a by"product of a theral power station, after cobustion of coal and

production of power! 0ly Ash is generated fro coal fired generation units! Coal has adoinating role for the power generation in India! %resently there are ;< coal basedtheral power plants operating in India! 6ost of the theral power plants in India useinferior 'uality coal, having low calorific value which after cobustion, leaves behindsa larger per cent of ash! As the power re'uired in industrial and agricultural sectors

increase, production of ash increases! 0ly ash contains any to(ic eleents! Abundant'uantities of fly ash are being produced by theral power plants situated all over theworld! At present )


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0ly ash consists of the large part of solid or hollow spherical particles ofsiliceous and aluinous gas with sall proportions of thin walled, ultifaceted

polyhedrousironcontent and are irregularly shaped, relatively porous carbon or carboncoated particles! The fineness of fly ash in any a case is to the sae e(tent as that of

%ortland ceent! The color varies fro light to dar# grey depending upon its carboncontents! The 'uality of fly ash varies fro source to source and is seldo uniforeven for the sae source because of the iportant factors li#e the nature and si2e ofcoal, the type of cobustion e'uipent, control of cobustion process, ode of fly ashcollection etc! the product fro a odern power plant when wor#ing on base"load isnorally 'uite consistent!

Table"): %4@SICA9 %R+%=RTI=S +0 09@AS4%roperty Saple of T%SIS 5)3 Re'uireent 7rade I 7rade II0ineness /Blaine C3g1

G Strength is ore and reduces the pereability!G Corrosive resistances, specific gravity, lie reactivity!G 8or#ability: Several reports suggest that fly ash decreases bleeding andsegregation, iproves plasticity and cohesiveness and perits easier placing andfinishing of concrete having no air"entraining agent! Soe fly ash reduce thewater re'uireents of test ortars, others /generally of high carbon content1showed increase water re'uireent above that of control ortars!G It is cheaply available and fulfills all the re'uireents!


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G 0ly Ash can be used for land fillings, soil stabili2ation!G Can be used as a partial replaceent of ceent, as fine aggregate and as coarseaggregates!G Iproves the 3 %recast RBcurved panels, precast concrete panels, and %recast RC channel units!


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3! Thin %recast RCC 9intel:*orally lintels are designed on the assuption that the load fro a triangular

portion of the asonry above, acts on the lintel! Bending oent will be 89 where8 is the load on the lintel and 9 is the span assued for the design purpose! By this

ethod, a thic#ness of )? c is re'uired! Thin precast RCC lintels are designed ta#inginto account the coposite action of the lintel with the bric#wor#! The thic#ness of thelintel is #ept e'ual to the thic#ness of bric# itself having a bearing of 35< on eithersupports! se of precast lintels speeds up the construction of walls besides eliinatingshuttering and centreing! Adoption of thin lintels results in up to ?/ii1 =volving restricted nuber of doors and window si2es> and/iii1 se of precast door and window fraes!%R=0ABRICAT=& BI9&I*7 C+6%+*=*TSC4+8H4ATS B9+CHS AS4 BRICHS R++0 TI9=SI*T=R9+CHI*7B9+CHS+IST B=A6S I*T=R9+CHI*7 8A99 B9+CHS%R=0ABRICAT=& BI9&I*7 C+6%+*=*TS

B9+CHS

5!6A*0ACTRI*7 %R+C=&R= +0 T4= C+6%+*=*TS:7enerally for the anufacturing of the coponents these proportions are used,7@%S6 3F9I6= F


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09@ AS4 ;5FB+TT+6AS4 Reaining%+*& AS4

5!) 6i(ing process:The above aterials are i(ed in a grinding i(er as per proportions and soewater /3"5Fof total wt1 for at least D inutes and then the i(er is puped in to the-4ydraulic bric# anufacture unit. and then solid bric#s can be anufacture! Insallscale

plants by using -6anual 9eg"line hydraulic achine. is used! But the solid bric#sanufactured using 6echanical unit will give sooth finish and ore productivity!Then hollow bric#s, colun bloc#s and bea bloc#s are anufactured usingoulds /the oulds are ade with cast iron1 are filled with the fly ash i(er which is

prepared previously and hollow bric#s are prepared! The roof bloc#s and $oist beas

are prepared by s#illed labour because these are used for the roof covering!

5!3 Roof bloc#:Roof bloc#s are the roof coving bloc#s, which are placed over the $oist beas!These are prepared based upon the diensions of the roos and the load coing overthe roof! Based up on loads the thic#ness is fi(ed! The shape of the roof bloc#s isshownin figure! It consists of central holes, which acts as a ventilator for the roo!

5!5 oist bea:oist bea is the prefab coponent, which is used as a support for the roofbloc#s! These $oist beas length and width are decided based on the clear span of theroos ! These $oist beas can be laid up to span of )?eters without any supportsscaffoldings! 0irst these are placed over copound walls then with a spacing of thewidth of the roof bloc#s another $oist bea is placed in bw these beas roof bloc#s are

placed one beside the another as shown then the entire roof is copleted!These figures show the roof bloc#s and $oist beas

! A&A*TA7=S +0 %R=CAST%R=0ABRICAT=& C+*STRCTI+*:G In prefabricated construction as the coponents is readyade, selfsupporting,shuttering and scaffolding is eliinated with a saving in


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shuttering cost!G In traditional construction, the repetitive use of shuttering is liited, as itgets daaged due to fre'uent cutting, nailing etc! +n the other hand, theould for the precast coponents can be used for large nuber ofrepetitions thereby reducing, the cost of the ould per unit!

G In prefabricated housing syste, there is saving of tie as the eleents canbe casted before hand during the course of foundations being laid and evenafter laying slab, the finishes and services can be done below the slabiediately! 8hile in the conventional in"situ RCC slabs, due to props andshuttering, the wor# cannot be done, till they are reoved! Saving of tieeans saving of oney!G In prefabricated construction, there is better 'uality control, shape and si2eof precast eleents! Therefore, in structural design, full advantage of

properties of ceent and steel can be e(ploited! There is disciplined use ofscarce aterials li#e ceent, steel and tiber!G In precast construction, the construction is not affected due to weather, rain,

wind etc!G 8e can save 9abour cost of i(ing, placing of concrete!G As the coponents are light weight they can be transport easily and placeand construct ever is needed especially during natural calaities li#e floods,earth 'ua#es, a$or accidents are ta#es place!G Because of easy of placing, these are ainly used for construction ofteporary bridges during wars!G 8e can construct structures which are located in congested places li#ewhere the lac# of place for storage of aterials and achinery!

?! 84@ S4+9& 8= %R=0=R %R=0ABRICATI+*J

In India, adoption of prefabrication building techni'ues has any erits, li#eavailability of aterials, labour, and technical s#ills! Advantages of prefabrication areultiple as the coponents are readyade and self"supporting, shuttering andscaffolding is eliinated, with a saving in shuttering cost! In traditional construction,the repetitive use of shuttering is liited, as it gets daaged due to fre'uent cutting,nailing, etc! +n the other hand, the ould for the precast coponents can be used for alarge nuber of repetitions, thereby reducing the cost of the ould per unit! In the

prefabricated housing syste, there is saving of tie, as the eleents can be castbeforehand during the course of the foundation being laid! =ven after laying slab, thefinishes and services can be done below the slab iediately! In the conventionalinsitu

RCC slabs, due to props and shuttering, the wor# cannot be done till these arereoved! Saving of tie eans saving of oney! In prefabricated construction, there isbetter 'uality control, shape and si2e of precast eleents! Therefore, in structuraldesign, full advantage of the properties of ceent and steel can be ta#en! There isdisciplined use of e(pensive aterials li#e ceent, steel and tiber!

D! C+*STRCTI+* %R+C=&R= SI*7 %R= 0AB C+6%+*=TS:0or case study we consider, single storied residential building consists of "


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roos constructed with prefab coponents and copared with onolithic construction!Steps for construction using prefabricated coponents:)! The foundation is constructed as usual onolithic construction procedure> herealso we can use fly ash bloc#s for supporting walls!3! 0or construction of coluns a specially ade colun bloc#s are available which

is having central gaps, which are useful for placing of the reinforceent!5! All the load bearing and internal walls are constructed with solid fly ash bric#sand hollow bric#s!! The corners $oints can be constructed using inter loc#ing wall bric#s!?! After copletion of the roo height bea bloc#s are laid over the walls, whichare acted as a beas for the building!D! Roof is constructed as e(plained in roof bloc#s and $oist beas!;! After placing all the roof bloc#s and $oist beas, a D wire esh is laid overthe entire roof then lean i( of ceent ortar is laid over it and the totalthic#ness of the roof should be restricted to inches only!! Being long spans of $oist beas are available we can lay the roof for all the

roos at a tie so that econoically we can save the anpower!E! After hardening of 5 days curing is to be done for two days! Then the finishingof walls and floors are to be done! Since the bric#s used are fly ash, the

plastering ceent can be inii2ed!Then the construction is copared with onolithic constructionG So by using prefab cop!, we can save the aterials up to


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=(tra reinforceent is re'uired to ta#e care of handling and erection stresses!Teporary props ay be re'uired in soe cases, before the in"situ concrete

$oints achieve strength!The crac#s ay develop at the $oints between the precast and in"situ concretedue to shrin#age and teperature stresses! To overcoe the, e(tra steel is

re'uired across the $oint!As there are chances of lea#ageseepage through the $oints between the precastcoponents, e(tra care is re'uired to a#e the lea# proof!The greater cost of transporting precasting units as copared with transportingaterials!The additional technical probles and cost of site connections of precasteleents, precast construction is used in all types of structures: Industrialbuildings, residential and office buildings, hall of si2able span, bridges, stadiusand prisons!

C+*C9SI+*S:

6ass housing targets can be achieved by replacing the conventional ethods ofplanning and e(ecuting building operation based on special and individual needs andaccepting coon denoinator based on surveys, population needs and rational useofaterials and resources! *o single approach and solution is available which can satisfythe counity at large! 4owever, what is ideal and desirable is to have a syste,whichcan provide choice for people and also appropriate techni'ues to eet the situation!Theessence lies in the syste approach in building ethodology and not necessarily

particular construction type or design! Adoption of any alternative technology on largescale needs a guaranteed ar#et to function and this cannot be established unless the

product is effective and econoical! %artial prefabrication is an approach towards theabove operation under controlled conditions!The ethodology for low cost housing has to be of interediate type lesssophisticated involving less capital investent! The 7ovt! of India has to populari2ethese coponents and the ipleent the at least for low cost 7ovt! houses! %eopleshould be ore aware about these products and save the environent by using thetheral waste in a better anner!

-se the Theral 8aste in proper way and gets the=conoical Construction.R=0=R=*C=S)! -%rafabricated structures Ka case study. by charl !h, $evan!pvol !D, 3

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Const of Pre Fab