3 - Precast Concrete in Detail

 

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COLLEGE OF ARCHITECTURE AND PLANNING Department of Architecture and Building Sciences

ARCH 436 Contem Con tem por porary ary Buildi Building ng Cons Construction truction Met hods hods

3. PRE PRECAS CAST T CONCRE CONCRETE TE I N DET DETAIL AIL

Dr. Mohammed Ghonim

Lecture Objectives Upon completion of this lecture, the student will be able to: 1. Differentiate between architectural precast and structural precast concrete. 2. Compare between total precast and mixed Precast Construction. 3. Explain how to connect precast structural elements. 4. Draw sketches for the connections between precast structural elements. 5. Describe the installation process of precast concrete structural elements.

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Lecture Content •   Introduction. •   Architectural Preca Precast st & Struct Structural ural Precast Concrete. •   Total Precast Vs. Mixed Precast Construction. •   Precast Concrete Joints. •   Slab to Slab Slab Connections. •   Slab to Beam Beam Connect Connections. ions. •   Slab tto o Wall Connections. •   Beam to Column Connections. •   Panel tto o Panel Connections. •   Column to Column Column Connect Connections. ions. •   Column to Foundation Connections •   Precast Concrete Extra Details. •   Precast Concrete Construction Construction Process Process..

Introduction The The consi consider derati ation ons s for for desi design gn and det detaili ailing ng of stru struct ctur ural al and and nonnonstructurall precast elements includin structura including g  joi  joints nts and conne connecti ctions ons for buil building dings s and building building work works s are introduced introduced in this lecture. Also, Also, it is importa important nt to mention that precast concrete buildings should be designed wherever possible to utiliz utilize e stan standa dard rdiized zed pr prec ecas astt conc concre rette elements, while most buildings will be unique and site spec specific. ific. At the conceptual design stage, a basic layout plan should be developed which achieves a balance between architectural / aesthetic requirements and a high degree of standardisation . Therefore, close collaboration amongst different design parties is essential during conceptual design to achieve the optimum standardisation.

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Architectural Precast & Structural Precast Concrete Pre Precast cast concrete concrete mem members bers are classif classified ied as; 1- architec architectura turall pre precast cast concrete concrete and 2structural precast concrete. Architectural precast refers to concrete elements that are used as nonstructural cladding elements, and their most common use is in precast concrete curtain walls. Structural precast concrete, includes all elements Structural elements of a building’ building’s ss structural tructural frame floors, roofs slabs, columns, and walls. Although an entire room or assembly of rooms can be precast, most structural structural precast concrete is used in standard eleme elements nts that are assembl assembled ed on site to form spaces.

 Architectural precast precast wall panels.

Structural Precast Concrete Elements.

Total Precast Vs. Mixed Precast Construction A build building ing ca can n be con constr struct ucted ed of all precast concrete members in which all structural structur al component components; s; columns, walls, and floor and roof slabs are made of  prec precas astt co conc ncre rete te.. This This sy syst stem em is referred refe rred to as total total prec precast ast conc concrete rete construction. In mixed mixed precast precast cons constru tructio ction, n, some elemen elements ts of the buil building ding are made of  pre precast cast concret concrete e memb members, ers, while while the  A total precast concrete parking under construction. construction. othe others rs ar are e made made of ca cast st-i -inn-pl plac ace e concrete, steel, or masonry. It combines the be bene neffits its of bot both pr prec ecas astt and and conventional construction. In mix mixed ed precast precast,, prec precast ast concrete concrete is used only in floor and roof slabs. Using precast concrete floor/roof slabs yields signi signifi fica cant nt sav savin ings gs becau because se a large large percentage of the cost of materials and formwork in a concret concrete e structure is embedded embedded in floor and roof slab slabs. s.

Mixed precast precast concrete concrete construction construction consisting of a steelframe structure with with hollowcore hollowcore slabs.

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Precast Concrete Joints In precast concrete buildings, joint designs play a pivotal role in ensuring that concrete components componen ts act as one piece. In most cases, sealin sealing g the joint space is necessary to prevent infiltration infilt ration of groundwater and exfiltration exfiltration of liquids carried by the structure structure..

Well detail Well detailed ed and constru constructed cted joints play a vital vital part in maintai maintaining ning the integrity integrity of the externa externall enve envelope lope of the building, building, ens ensurin uring g it is weat weatherpr herproof oof and meet meeting ing any other  requirements such as fireresistance and acoustic performance. The function of the joint between precast elements is to provide physical separation between the units and prevent -in conjunction conjunction with joi joint nt sealants- the ingress of water and air into the building; and, if required, fire resistance.

Slab to Slab Connections Co Conne nnect ction ions s bet betwee ween n hollow hollow-co -core re slabs slabs and supporting members are made using site-cast concrete fill and reinforcing steel. In addition to the concrete fill used for connections, a site-cast concrete concret e topping is generally used over the slabs. The topping provides structural structural integrati integration on of slab units and increases the floor’s fire resistance and sound insulation. It also functions as a leveling bed, particularly with units with uneven camber. Topping, when used, is generally about 2 inches thi hic ck and rei reinfor orc ced wit with wel welded wir wire reinforcement (WWR).

Grout keys provide structural continuity between floor slab units.

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Slab to Beam Connections

H.C. slabs Grout

Steel bars through the grout keys

Bearing pads

Precast hollow core slabs connected at their ends to a rectangul rectangular ar precast beam by steel ties.

Slab to Beam Connections

Setback

A double-tee double-tee floor unit unit being flown into posit position ion in a precas precastt building. The setbacks in double-tee stems stems reduces floor height.

Double tee slabs supported over a rectangular beam.

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Slab to Wall Connections

Projections in precast concrete walls to support suppo rt the inv inverte erted-tee d-tee beam beamss or the double-tee floor slabs.

Beam to Column Connections

Projecting Bracket

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Panel to Panel Connections Precast panels are connected to each others or to floor and roof elements by using metal plates and angels, they are fastened by welding or bolting. Connect Connections ions may be projected or  recessed recess ed to provide flush finishing finishing surface. surface.

Different cases of precast panel to panel connections.

Column to Column Connections Precast Prec ast conc concrete rete columns columns are conn connect ected ed toge together  ther  thr throug ough h bolti bolting, ng, the top top of a low lower er-f -floo loorr col colum umn n contains cont ains thr threade eaded d bolts project projecting ing out, while the bottom of an upper-floor column has an embedded base plate containing holes to engage the bolts. The block-outs in the column above the holes are filled with concrete after the connection has been made.

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Column to Foundation Connections The method method of co conne nnecti ction on to the the found foundat ation ion and to the the column abov column above e will vary with manufac manufacture turerr. Foun Foundati dation on connection may be via a base plate connected to the column or by reinforcing bars projecting from the end of the column passing into sleeves that are subsequently filled with grout. Alternatively,, a column may be set into a preformed hole in a Alternatively foundation foundati on block and grouted into position position.. Column to base connections may be by threaded rods joined with an appropriate connector; with concrete subsequently cast round to the dimens dimensions ions of the crosscross-sect section ion of the column.

Precast Concrete Extra Details

Lifting hooks hooks are very important component in precast concrete units.

Partial precast concrete hollow core slab over metal hanger to provide an opening.

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Precast Concrete Extra Details

Temporary Support

Total precast construction

Temporary Support

Precast double tee slab lifted by a crane to its position

Precast panels installation process require

over l-shaped precast beams.

temporary support.

Precast Concrete Extra Details

Precast beams contain grooves to hold double tee ribs to provide more neat beam to roof connection.

Double tee slabs does not require temporary support because they are stable.

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Precast Concrete Extra Details

Various solutions for beam to column connection.

Precast Concrete Construction The construction process of a total precast building has much in common with structural steel steel con construc structio tion; n; that is, memb members ers are brought brought into posi position tion using a crane, crane, and are connected connect ed together either through welds or bolts. Steel embeds are included in precast members to facilitate member bolting and/or welding.

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Summary •   Also, it is importan importantt to mentio mention n that precast concrete conc rete building buildings s shou should ld be des designe igned d wherever possible to utilize standardize standardized d preca precast st con concr crete ete ele eleme ments nts,, while while most most buildings building s will be unique and site specifi specific. c. •   Total precast concrete construction construction refers to th thos ose e case cases s wher where e all all stru struct ctur ural al components component s are made of precast concre concrete. te. •   In mixe mixed d pr prec ecas astt co const nstruc ructi tion on,, so some me elem elemen ents ts of th the e buil buildi ding ng ar are e made made of  prec precas astt co conc ncre rete te memb member ers, s, wh whil ile e th the e oth others ers are made made of anoth another er materi materials als.. •   In precast precast building buildings, s, joint design designs s play a pivot pivotal al role role in ens ensuri uring ng tha thatt con concre crete te co compo mpone nent nts s ac actt as one piece piece.. In mos mostt cases, sealing the joint space is necessary. •   The construction construction process of a total total precast bu buil ildi ding ng ha has s much much in comm common on with with struc structu tura rall stee steell co cons nstr truc ucti tion on;; th that at is members are brought into position using a crane, and are connected together either  thr through ough wel welds ds or bolts.

References •

  Allen, EA. (2 (2009) 009) Fundamentals Fundamentals of building co construction nstruction materials and methods, John Wiley & Sons.

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  Ching, Francis (2008) Building Construction Illustrated, John Wiley Wiley & Sons.

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  Emmitt, S.& G Gorse, orse, C. (2006) “Barry’s “Barry’s Ad Advanced vanced Constru Construction ction of Bu Buildings”, ildings”, Blackwell Pu Publishing. blishing.

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  Garrison, Ph Philip, ilip, (2005) “Basic “Basic Structures for Engineers Engineers and Architects”, Architects”, Wiley-Blackwell. Wiley-Blackwell.

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  http://en.wikipedia.org/wiki/Precast_concrete.

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  https://fp.auburn.edu/heinmic/ConcreteHistory/Pages/timeline.htm

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  http://www.concretenetwork.com/precast-concrete/advantages.html

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  http://youtube.com

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Lecture Activity Each student is required to prepare a brief but informative internet-based internet-based research about one of the topics related to this lecture (Precast Concrete in Detail); i.e., new developments, developments, successive and local case studies or important details. The research should be presented in only one A4 sheet.

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