Chapter15 Precast

8/11/2019 Chapter15 Precast

1/25

Fundamentals of Building Construction, Materials & Methods,5thEdition

Plant-Cast Precast Concrete% Concrete elements, cast and cured in a manufacturing plant,

then transported to the construction site!

% lant casting allo's increased e(ciency and higher )ualitycontrol!% *ura+le, permanent steel forms are reused many times, reducing

form'or costs compared to sitecast concrete!% -se of .ype """, high early strength cement and steam curing

allo' concrete mem+ers to +e cast and cured in as little as 2/hours!

% Controlled casting conditions and high )uality forms allo' forgreater control of surface nishes!

5 PRECAST CONCRETE FRAMING SYSTEMS


2/25


lant1Cast recastConcrete

%tructural elementsare commonlyreinforced 'ithtightly stretchedpretensioned steelstrands, 'hich

pro$ide increasedstructural e(ciency!

% Con$entional steelreinforcing is addedfor resistance tothermal and othersecondary stresses!



3/25


lant1Cast recastConcrete

% 3n the constructionsite, precastconcrete elementsare lifted into placeand assem+led intostructural assem+lies

in a process similarto that used forstructural steel!

% Compared to sitecastconcrete, precast

concrete erection isfaster and lessa4ected +y ad$erse'eather conditions! # $acuum lifting de$ice is used to lift and place

precast concrete prans!



4/25


EC#.,

E.EE*C36CE.E

.-C.-#7

E7EME6.



5/25


recast Concrete la+s

% -sed for 8oor and roof decs!

% *eeper elements to'ard theright +elo': span further thanthose that are shallo'erto'ard the left:!

% Right: ;ollo' core sla+s

staced at the precasting plant!

PRECAST, PRESTRESSED CONCRETE STRUCTURAL ELEMENTS


6/25


recast Concrete Beams and


7/25


recast ConcreteColumns and >allanels

% ro$ide support for+eam and sla+elements!

% ince these elementscarry mainly a?ialloads 'ith little+ending force, theymay +econ$entionallyreinforced 'ithoutprestressing!

% 3r, long, slendermultistory elements

may +e prestressedto pro$ide resistanceto +ending forcesduring handling anderection (columns atright).



8/25


recast Concrete Columnsand >all anels

% recast concrete 'all

panels may +e solid (right:,hollo', or sand'iched'ith an insulating core:!

% >all panels can +e ri++ed,to increase their $erticalspan capacity 'hileminimi@ing 'eight, orformed into other specialshapes (below)!



9/25


3ther recast ConcreteElements

%recast concrete stairsbelow)

% -ni)uely shaped structuralelements for a sportsstadium (right)

% Etc!



10/25


#ssem+ly Concepts forrecast ConcreteBuildings

% Aertical support can +epro$ided +y precastcolumns and +eamsabove:, 'all panelsbelow:, or acom+ination of all

three!% .he choice of roof and8oor sla+ elementsdepends mainly onspan re)uirements!

% recast sla+ elements

are fre)uently alsoused 'ith other $erticalload+earing systemssuch as sitecastconcrete, reinforcedmasonry, or steel!



11/25


#ssem+ly Concepts forrecast ConcreteBuildings

% Above:recastconcrete structureconsisting of solid'all panels andhollo' core sla+s!

% Below: # single story'arehouse consistingof dou+le teessupported +yinsulated sand'ich

'all panels!



12/25


#ssem+ly Conceptsfor recastConcreteBuildings

% # paring garagestructureconsisting ofprecast dou+letees supported+y in$erted tee+eams onhaunchedcolumns!



13/25


14/25


Casting ;ollo' Corelans

% recast elements aremanufactured incasting beds, 00 ftor more in length!

% ;igh1strength steelstrands are strung

the length of the +edand tensioned!

% Con$entionalreinforcing, 'eldplates, +locouts,

lifting loops, andother em+eddeditems are added asneeded!

% Concrete is placed!

MANUFACTURING OF PRECAST CONCRETE STRUCTURAL ELEMENTS

-ntensioned prestressing strands can +e seen inthe left1most casting +ed! "n the +ed second fromthe right, lo'1slump concrete for hollo' coresla+s is +eing formed o$er tensioned strandsusing an e?trusion process! # completed hollo'core casting is $isi+le at the far right!


15/25


restressing andeinforcing teel

% Many precastelements contain+oth prestressingstrands andcon$entionalreinforcing!

% Right:.heprestressing strandsfor an ##;.3 girderare depressed into ashallo' $1shape tomost e(ciently resist

tensile forces in the+eam! hear stirrupsare formed fromcon$entional steelreinforcing!



16/25



% 3nce the concretehas cured to su(cientstrength, the castingsare cut into sectionsof desired length(above)!

% "n some cases,trans$erse +ulheadsare inserted to di$idethe casting +ed intosections +eforeconcrete is placed! "n

this case, only theprestressing strandsneed to +e cut toseparate the sections(below).



17/25



% "ndi$idual sectionsare lifted from thecasting +ed (right)and stocpiled toa'ait shipping tothe constructionsite!



18/25



% recast concreteelements areshipped to theconstruction site +ytruc and erectedon site +y crane!



19/25


Casting ;ollo'Core lans

% ample hollo'core sla+sections of$aryingdepths!

%#t +ottom left,note theinsulatedsand'ich 8oorpanel!



20/25


3"6"6< EC#.

C36CE.E E7ME6.



21/25


E?ample Column1to1Column Connection% Metal +earing plates and em+edded anchor +olts are cast into

the ends of the columns!

% #fter the columns are mechanically =oined, the connection isgrouted to pro$ide full +earing +et'een elements and protectthe metal components from re and corrosion!

JOINING PRECAST CONCRETE ELEMENTS


22/25


E?ample Beam1to1ColumnConnection

% Beams are seton +earingpads on thecolumncor+els!

% teel anglesare 'elded tometal platescast into the+eams and

columns andthe =oint isgrouted solid!



23/25


24/25


itecast Concrete.oppings o$errecast la+s

%


25/25

Fundamentals of Building Construction, Materials & Methods,

recast ConcreteConstruction andeismic *esign

% "n areas of highseismic ris,structures must +edesigned torespond safely tothe dynamic forcesimparted into thestructure!

% "nno$ations in =ointdesign areimpro$ing theconnectionsystems in precast

concrete structuresand maing themincreasinglysuita+le for use insuch areas!


# large scale test facility for simulating seismicforces on precast concrete structural systems!

Documents

Chapter15 Precast