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PRESTRESSED CONCRETE INSTITUTE

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Number 353

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Housing

Precast prestressedCOVER STORY

concrete shelters peoplehandsomely, comfortably,economically

Whether your project is a luxury condominiumoverlooking Waikiki or federal housing for theneedy, precast prestressed concrete offers thequalities you and your tenants are looking for.

Long spans mean unobstructed flexibility ofinterior layout, maximum exploitation of aspectacular view, and the possibility of spaciouscanti levered balconies, walkways, or sunshadesfor intimate relation with the out-of-doors.Dense concrete and hollow-core voids in floorslabs combine for sound resistance. Precast wallunits are easily insulated for efficient, energy-saving temperature control. And one of precastprestressed concrete’s most remarkable benefitsis economy.

For one thing, prestressed concrete lendsitself easily to systems building, with itssimplicity and speed of construction. Repetitive modules permit economical mass productionof a few basic components. Plant fabricationpermits top quality control. And erection proceeds smoothly, on schedule.

With precast units a floor/ceiling/cantilevered balcony may go up in a single erectionoperation. An immediate work platform,clear of shoring, is ready for the finishing trades.Rapid and complete enclosure prevents costlyshutdown in cold weather.

Voids of hollow-core slabs, or the spacesbetween tee stems, provide chases for plumbing, HVAC, electrical, and telephone systems.Dense, smooth surfaces may be exposed insideand out; or carpeting, ceiling, and roofingmaterials may be applied directly.

Exposed structural units alone provide agraceful and dignified architectural expression.A variety of finishes, including fluted, raked,or exposed aggregate surfaces, are created withfactory precision.

All these factors add up to early occupancy.And that means reduced interim financing costs,savings on onsite labor, and earlier income.

Protection of life and property is vital forhousing. The fire resistance of precast prestressed concrete means that a fire starting inone apartment can often be contained there.It provides minimal need for structuralrepair in case of fire, and low insurance rates.The muscle of prestressed concrete gives itoutstanding resistance to hurricanes andtornadoes. Its durable surface protects againstsand and sea, as well.

Precast prestressed concrete shelters people,naturally.

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Architectural precastconcrete lends distinction

The Hotel Toronto, Ontario, was named a winner in the 1976PCI Awards Program. The 32-story tower is clad in warmlycolored architectural precast concrete. It rises from a podiumof the same material. The hotel acts as a focal point of interestat the city’s core.

In all, 2400 precast concrete elements grace the building,including window units, column covers, and panels for wallsand roof. The precast exterior wall panels were designed sothat each guest room is enclosed by a single piece, completewith glazing. In one quick operation, the room was protectedfrom weather and ready for the finishing trades. Verticaljoints between panels form the window working tracks.

The PCI Awards Program jury admired “the clean simplicity of this design, with its distinctive precast concrete cladding.”

Architect: Joint venture: Neish Owen Rowland 8 Roy,Toronto; and Reno Negrin & Associates, Vancouver,British Columbia

Structural Engineer: S WR Engineering Limited, TorontoProject Manager: Concord/a Management Co. Ltd., TorontoArchitectural Precast Concrete. Pre-Con Company,

Bramp ton, Ontario

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Precast prestressed concretesupplies vital fire safety

The protection of life and property is of the greatestimportance to housing owners and tenants. Low insurance rates and minimal need for structural repair in caseof fire are vital, too. This is one reason owners of theYorker Apartments, Edina, Minnesota, selected fire-resistant precast prestressed concrete. Prestressed unitscan provide two, three, or four-hour fire ratings. Theycan actually contain a fire in the room or apartmentwhere it starts.

The Yorker contains 138,900 sq. ft. of prestressedhollow-core slabs, 31,400 sq. ft of 24-in, deep doubletees, and precast concrete balconies and corridor lintels.

Architect: Frank Reese, Eden Prairie, MinnesotaStructural Engineer. Lloyd Darg, MinneapolisGeneral Contractor. Inland Construction Company,

EdinaPrestressed Concrete: Spancrete Midwest Co., Osseo,

Minnesota

Long spans of precastprestressed concreteprovide column-free spacefor custom interiorsThe 1010 Wilder Condominium in Honolulu takesadvantage of the 37-ft. spans easily achieved withprecast prestressed hollow-core floor slabs. Individualowners of the spacious apartments (up to 6000 sq. ft.)redesigned their units, with the architect’s assistance,before construction was finished. The absence ofunnecessary supports meant both greater flexibility oflayout and an unobstructed panorama of DiamondHead and Waikiki. In the parking structure, long spanseased the design of traffic patterns and assured maximum usable space.

The 8-in, hollow-core slabs, with topping, provided“more than adequate” soundproofing betweenapartments.

Architect. Architects Hawaii, HonoluluI Structural Engineer: Richard M Libbey & Associates,

HonoluluGeneral Contractor: Hawaiian Dredging & Construction

- .- Co., Honolulu-, - ‘- Prestressed Concrete: Hawaiian Dredging & Construction

-~~ ~• J~i Co., Precast Division, Honolulu

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The best of many good things about thisprestressed hollow-core system?

Economy!O

This simple way to build a house features only two basiccomponents: precast columns and prestressed hollow-coreslabs for walls and roof. But there’s plenty of designflexibility in both configuration and embellishment, thanksin part to load-bearing and clear-span capacities.

In one house, the low prestressed roof of the masterbedroom, with a 2-in, topping, became a sun deck accessiblefrom two loft bedrooms. In another, the living room has a16-ft. ceiling (photo). Smooth, warmly-colored surfacesblend companionably with other materials, such as wood,glass, or brick. Site preparation is minimal, normallyrequiring no fill or compaction, so natural surroundingsare almost untouched. This custom end-product soundsexpensive. But perhaps the best thing about the systemis economy.

Rapid erection (5000 sq. ft. per day) and short dry-intime (one day) save on financing and labor costs. Shoring,forming, and pouring are eliminated, and factory-controlledtolerances are close and accurate. Cores in prestressed walland roof slabs provide built-in raceways. Fire and windstorm resistance mean low insurance rates. Durable surfacesrequire very little maintenance, and prestressed unitsensure against cracking. Lightweight construction allowsreduction in size of beams, columns, and footings, savingmaterials while enhancing design flexibility.

General Contractor: Delco, Inc., Orange City, FloridaPrecast Prestressed Concrete: H. D. W. Houdaille,

Jacksonville Florida

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Precast concrete columns andprestressed hollow-core slabs gotogether quickly in a variety ofways.

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Note attractively groovedhollow-core walls and ceiling in this handsomeinterior. The house shownin this photo was designedby John Delong, OrangeCity, Florida.

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The Alan Jackson house in Orange City, Florida, wasdesigned and engineered by architects Gross & Newton,Orlando, Florida.

Relying upon tongue and groove edgesfor continuous alignment and water-tightness, the hollow-core wall slabsslide into slots cast in the columnsides. Because of the unusual rigidityof these prestressed slabs when turnedon edge, continuous footings areeliminated Wall slabs may be projected through slots cast into columntops to form cantilever beams for thesupport of balconies or roof overhangs

After roof slabs have been erected,they are cored and anchored to thewall panels, using steel dowels set ingrout. A combination of momentconnections, shear walls, and reinforced jointing renders this systemfeasible for structures up to threestories high, having clear spans to38 ft.

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Precast prestressed concrete helps createhomey, sound-resistant quarters for young families

Newton Court at the University of Colorado,Boulder, is a development of 292 housing unitsand a child care center for married college students. The University specified a friendly, villageatmosphere, and sound control for the pursuit ofquiet study. The natural, warmly-colored exposedaggregate (1 1/2 - in. Colorado stone) of the

precast wall panels adds a homey, attractive touch.And the high-density concrete in walls and prestressed double-tee floors helps provide thenecessary sound resistance. Both requirementswere fulfilled within the budgetary restraints ofthe HUD college housing program. Futuremaintenance, too, will be most economical.

Architect.’ The A.B.R. Partnership (R. RussellSeacat and Jeffrey D. Francis, now of Barker,Rinker, Seacat Architects, Inc.), Denver

Structural Engineer: Jorgensen & Hendrickson,Inc., Denver

General Contractor.’ Weaver ConstructionCompany, Denver

Prestressed Concrete: Stresscon Corporation,Colorado Springs

Double tees are factory-castto close tolerances for trouble-free erection.

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Engineer: “Plantproduction of precastprestressed unitshelps assure topquality control”

The Hilton at Corporate Square, Baton Rouge,Louisiana, is 21 stories high and built entirely ofprecast concrete. Its exposed structural componentsconstitute the graceful and dignified architecturalexpression of the hotel. Plant quality controlassures the handsome appearance of each unit, aswell as close tolerances for smooth, on-timeconstruction progress.

The structural system consists of story-high,precast bearing walls; precast shear walls; and prestressed hollow-core floor slabs. Wall panels werecast in vertical T forms 32 ft. long. Repositioningof blockouts and bulkheads allowed production offlat, L-, or T-shaped walls as required. Groutedshear keys connect floor slabs to provide a diaphragmwhich distributes lateral loads (including hurricanewind) to the shear walls. Principal connections areaccomplished by vertical post-tensioned steelplaced in wall panel conduits. The stretched andanchored steel applies compression forces whichclamp the floor planks or compress the drypackjoint between bearing walls.

Other benefits of prestressed concrete includehigh sound resistance ratings, low fire insurancepremiums, and economy due to industrializationand rapid construction. The owner, having a stakein the area’s economy, was particularly pleasedwith the ready availability of local labor andmaterials.

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Architect: A DH Systems, Inc., Baton RougeStructural Engineer: Sepp Firnkas Engineering,

Inc., BostonGeneral Contractor.’ Milton Womack Construction

Corporation, Baton RougePrecast Prestressed Concrete: Louisiana Concrete

Products, Inc., Baton Rouge

Floor panel

Erection inprogress

Wall panel

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Architect cites “wide range of textures and finishesoffered by precast prestressed concrete’3This attractive building, Walter Salvo Housing for theElderly, is located in Northampton, Massachusetts. Sincethe building contains nearly 200 similar apartments, mass-produced prestressed concrete was a convenient andeconomical choice. Best of all, there was no sacrifice ofbeauty. The Architect notes that “the variety and contrastof fluted ribbing, exposed aggregate, and smooth surfaceswere produced with factory precision and regularity,without field-applied finishes.”

Exterior and bearing walls, beams, columns, spandrels,

PRESTRESSED CONCRETE INSTITUTE

20 NORTH WACKER DRIVE, CHICAGO, ILLINOIS 60606

shafts, stair wells, and balconies are composed of precastconcrete. Prestressed hollow-core slabs provide the floorsand roof.

Architect Engineer: Reinhardt Associates, mc,Springfield, Massachusetts

General Contractor: D. A. Sullivan and Sons, mc,Northampton

Precast Prestressed Concrete: San- Vel ConcreteCorporation, Little ton, Massachusetts

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PC Items Periodical Number 353 / Editor: Dorothy Jerome