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Design/Construction Guide: Concrete Forming

THE ENGINEEREDWOOD ASSOCIATIONAPACONCRETEFORMINGDESIGN/CONS TRUCTION GUIDEWood is the right choice for a host of construction applications. It is theearth s natural, energy efficient and renewable building wood is a better use of miracle in today s woodproducts is that they make more efficient use of the wood fiber resource to make stronger plywood, oriented strand board, I-joists, glued laminatedtimbers, and laminated veneer lumber. That s good for the environment, and good fordesigners seeking strong, efficient, and striking building few facts about wood. We re not running out of of the United States land base 731 million acres is covered by forests. About two-thirds of that 731million acres is suitable for repeated planting and harvesting of timber. Butonly about half of the land suitable for growing timber is open to of that harvestable acreage also is open to other uses, such ascamping, hiking, and hunting. Forests fully cover one-half of Canada s land mass.

SELECTING AND SPECIFYING CONCRETE FORM PANELS General Virtually any Exterior type APA panel can be used for concrete formwork

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Transcription of Design/Construction Guide: Concrete Forming

1 THE ENGINEEREDWOOD ASSOCIATIONAPACONCRETEFORMINGDESIGN/CONS TRUCTION GUIDEWood is the right choice for a host of construction applications. It is theearth s natural, energy efficient and renewable building wood is a better use of miracle in today s woodproducts is that they make more efficient use of the wood fiber resource to make stronger plywood, oriented strand board, I-joists, glued laminatedtimbers, and laminated veneer lumber. That s good for the environment, and good fordesigners seeking strong, efficient, and striking building few facts about wood. We re not running out of of the United States land base 731 million acres is covered by forests. About two-thirds of that 731million acres is suitable for repeated planting and harvesting of timber. Butonly about half of the land suitable for growing timber is open to of that harvestable acreage also is open to other uses, such ascamping, hiking, and hunting. Forests fully cover one-half of Canada s land mass.

2 Of this forestland, nearly half is considered productive, or capable of producing timber on asustained yield basis. Canada has the highest per capita accumulation of protected naturalareas in the world areas including national and provincial parks. We re growing more wood every landowners plant more than two billion trees every year. In addition, millions of trees seednaturally. The forest products industry, which comprises about 15 percentof forestland ownership, is responsible for 41 percent of replanted forestacreage. That works out to more than one billion trees a year, or aboutthree million trees planted every day. This high rate of replanting accounts for the fact thateach year, 27 percent more timber is grown than is harvested. Canada s replanting recordshows a fourfold increase in the number of trees planted between 1975 and 1990. Manufacturing wood is energy products made up 47 percent of allindustrial raw materials manufactured in theUnited States, yet consumed only 4 percentof the energy needed to manufacture allindustrial raw materials, according toa 1987 study.

3 Good news for a healthy every ton of wood grown, a young forest produces tons of oxygen and absorbs tons ofcarbon , the miracle material for the environment, for design , and for strong, lasting :The recommendations inthis guide apply only topanels that bear the APAtrademark. Only panelsbearing the APA trademarkare subject to theAssociation s qualityauditing SHEATHINGEXPOSURE 1 SIZED FOR SPACING32/16 15/32 INCH000PS 1-95 C-D PRP-108 THE ENGINEEREDWOOD ASSOCIATIONAPAWOODThe Miracle Material Percent ofPercent ofMaterialProductionEnergy UseWood474 Steel2348 Aluminum28 CONTENTSS electing and SpecifyingConcrete Form Panels .. 4 Form Maintenance .. 9 Form design .. 10 Engineering Data ..17 Case Studies ..21oncrete formwork represents close to half the cost of a Concrete structure. Formdevelopment, therefore, warrants seriousand detailed engineering realization of architectural intent, similarly, isrelated to formwork quality.

4 The form is to struc-ture what a mold is to sculpture, and it follows thata Concrete building or other structure will be asaesthetically true as the form that shapes APA publication is intended for use by archi-tects, engineers and contractors in their pursuit ofsuccessful, cost-effective Concrete structures. Itcontains APA panel grade information, form main-tenance recommendations, design data and severalproject case additional information on APA panel grades,applications or member manufacturers, contactAPA or visit the Association s web site at following books also are recommended for additional Concrete formwork information: formwork for Concrete , Hurd, copyright 1995 by the American Concrete InstituteFormwork for Concrete Structures, Peurifoy and Garold Oberlender, copyright 1995 by McGraw-HillCSELECTING ANDSPECIFYING CONCRETEFORM PANELSG eneralVirtually any Exterior type APA panelcan be used for Concrete formworkbecause all such panels are manufac-tured with waterproof glue.

5 For concreteforming the plywood industry producesa special product called Plyform, whichis recommended for most general form-ing uses. The term is proprietary andmay be applied only to specific productswhich bear the trademark of APA TheEngineered Wood Association. All Plyformpanels are Exterior type made with C orbetter veneer and waterproof and HDO are names the plywoodindustry uses to describe overlaid sur-faces. MDO means Medium DensityOverlay and HDO means HighDensity Overlay. During plywood pro-duction, these overlays are bonded tothe plywood under high heat and pres-sure in a press. The function of theoverlay is to add stability, repel foreignsubstances from the surface and providea smoother and more durable formingsurface. The thermo-set resins used inoverlay production are hard and resistwater, chemicals and abrasion. HDOis most often specified where thesmoothest possible Concrete finish andmaximum number of reuses is GradesPlyform is Exterior-type plywood limitedto certain wood species and veneergrades to assure high bearing this specific identifi-cation are available in three basic grades:Plyform Class I, Plyform Class II andHDO PlyformThis Plyform panel meets the samegeneral specifications as PlyformStructural I or Class I or Class II.

6 Allclasses of HDO Plyform have a hard,semi-opaque surface of thermo-setresin-impregnated material that formsa durable, continuous bond with theplywood. The abrasion-resistant surfaceshould be treated with a release agentprior to its first use and between eachpour to preserve the surface and facili-tate easy Plyform is most often specifiedwhen the smoothest possible concretefinishes are desired, because the panelhas a hard, smooth surface. It canimpart a nearly polished Concrete sur-face. Both sides of HDO are moistureresistant but cannot always be used toform Concrete with equal effectivenessunless specifically made for that pur-pose. Scratches and dents in the backscaused by fastening the panels to thesupports may make the use of bothsides impractical. Various grades ofHDO Plyform may be available; checkwith your supplier. With reasonablecare, HDO Plyform will normally pro-duce 20 to 50 reuses or more. Someconcrete- Forming specialists achieve 200or more reuses with good Density OverlaySpecial proprietary grades of MDO areavailable for Concrete Forming .

7 RegularMDO is intended for use as a paint surfaceand should not be used for Concrete form-ing. Panels are typically overlaid on onlyone side, although they can be pro-duced with MDO on both MDO Concrete form ply-wood is normally factory-treated with arelease agent and edge-sealed to protectthe edges from water absorption. TheStructural I Plyform. Each may beordered with a High Density Overlaidsurface on one or both sides. PlyformClass I is also available as Structural IPlyform when additional strength Class IClass I Plyform has Group 1 faces forhigh strength and stiffness. See Tables 3and 4 for load I PlyformThis Concrete Forming panel is madewith Group 1 wood species throughout the strongest. All other factors beingequal, it will support the highest loadsboth along and across the panel. It isspecifically designed for engineeredapplications and is recommended whereface grain is parallel to supports. SeeTable 5 and 6 for load Class IIClass II Plyform may have Group 2 facesbut still provides adequate strength formost Forming applications.

8 Check withsupplier for PlyformNonoverlaid Plyform is usually madewith B grade veneer face and back andreferred to as B-B Plyform. It is avail-able as Structural I, Class I or Class panels are sanded on both sidesand treated with a release agent at themill (called mill oiled ) unless other-wise the mill treatment is reasonablyfresh when the panels are first used, theplywood may require another treatmentof release agent. It is also important toapply a top-quality edge sealer beforethe first pour. Plyform panels can beordered edge-sealed from the mill. Five to ten reuses of B-B Plyform are surface should betreated with a release agent prior to itsfirst use and between each pour topreserve the surface and facilitate easy stripping. MDO form panels create a matte or flat finish on the Concrete GradesAdditional plywood grades specificallydesigned for Concrete Forming includespecial overlay panels and proprietarypanels. These panels are designed toproduce a smooth, uniform concretesurface.

9 Some proprietary panels aremade of Group 1 wood species only,and have thicker face and back veneersthan those normally used. These pro-vide greater parallel-to-face grainstrength and stiffness for the may be specially treated or coated with a release agent. Checkwith the manufacturer for designspecifications and surface TexturesPlywood is manufactured in manysurface textures, ranging from the pol-ished High Density Overlaid plywoodto patterned board-and-batten sidingpanels. Working with these specialpanels, and with field-applied patterns,virtually any texture can be textured plywood usuallyis applied in two ways in formworkdesign: (1) as a liner requiring plywoodbacking so that the liner delivers tex-ture, but contributes little to the struc-ture of the formwork , or (2) as the basicforming panel. In the second case, thebest reports come from projects wherethe number of pours required is limited,because the textured surface canincrease necessary stripping forcesand, therefore, the possibility of panelcase, two 3/4-inch sanded panels, bothwithin manufacturing tolerances, couldform a joint with a 1/32-inch variationin surface level from panel to of panels and shimmingare quick, easy Surface CharacteristicsSurface dustingof Concrete has occa-sionally been observed in concretepoured against a variety of formingmaterials, including plywood.

10 Thereappears to be no single reason thesoft, chalky surface has been traced toa variety of possible causes, includingexcess oil, dirt, dew, smog, unusuallyhot, dry climactic conditions, andchemical reactions between the formsurface and the in the stripping process. Film-coatings, such as lacquer, polyurethaneor epoxy, can be used with a releaseagent to make stripping TolerancesPlywood is an engineered product,manufactured to exacting tolerancesunder Product Standard PS tolerance of plus inch and minus1/16 inch is allowed on the specifiedwidth and/or length. Sanded Plyformpanels are manufactured with athickness tolerance of plus or minus1/64 inch of the specified panelthickness for 3/4 inch and less, andplus or minus 3 percent of thespecified thickness for panelsthicker than 3/4 Plyform panels have a plus or minus tolerance of 1/32 inch for all thicknesses through 13/16 panels have a tolerance of 5 percent over or under the specified squareness, the Product Standardrequires panels to be square within1/64 inch per nominal foot of lengthwhen measured corner to corner alongthe diagonal, for panels 4 feet andgreater in edge straightness, panels must bemanufactured so that a straight linedrawn from one corner to an adjacentcorner shall fall within 1/16 inch of thepanel tolerances, and consistent levelsof quality required by APA TheEngineered Wood Association, help mini-mize the time and labor required inbuilding forms.


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