求翻译，急用。土木工程关于模板的

Materials used for forms for concrete structures include lumber,plywood,hard-board,fiberglass,plastic and rubber liners,steel,paper and cardboard,aluminum,fiber forms,and plaster of pair.Additional materials include nails,bolts,screws,form ties,form clamps,anchors,various types of inserts,and various types of form oils and compounds as well as their accessories.Forms frequently involve the use of two or more materials,such as plywood facing attached to steel frames for wall panels.
Form lumber generally consists of the softwoods with the species used being the type available in the local area.Various species are usually grouped together for grading and marketing purposes.Some of these groups and included species commomly used for formwork are

1  Douglas fir-larch (Douglas fir,western larch)
2  Douglas fir-South (only Douglas fir form southern growth areas)
3  Hem-fir (Westren hemlock,California red fir,grand fir,noble fir,white fir,Pacific silver fir)
4  Spruce-pine-fir (loblolly pine,longleaf pine,shortleaf pine,slash pine)

  Form lumber is made up of standard sizes,either rough or dressed,with the grading quality of construction grade or NO.2 grade usually specified.Shoring or flasework requiring greater capacity should be used because it has been found to be the most stable.green lumber will warp and crack,whereas kiln-dried lumber will swell excessively when the imprint of the board on the concrete surface is desired for architectural reasons.
  Plywood is available as flat panels (4 ft × 8 ft sheets) made of thin sheets of wood (called piles) with a total thickness ranging form 14 in.to118 in.It is com-monly used for sheathing or lining forms because the relatively large sheets are economical and easy to use.U.S.plywood is built up of an odd number of piles with the grain of adjacent layers perpendicular.The piles are dries and joined under pressure with glues that make the joints of adjoining layers equalizes strains and thus minimizes shrinkage and warping of the plywood panel.For maximum strength,the direction of the grain in the face layers should be placed paralled to the span.
  The plywood should be the exterior grade because of its waterproof glue.It should also be factory treated with a form oil or parting compound.With proper care,plywood can be reused many times. Coated plywood is occasionally used.Called overlaid or plastic coated,it is ordi-nary exterior plywood with a resin-impregnated fiber facing material fused to one or both sides of the plywood sheet.The overlay covers the grain of the wood,resulting in a smoother and more durable forming surface.The resins used in over-lay production are hard and resist water,chemicals,and adrasion.Two grades,high density and medium density,are available,and their difference is in the density of the surfacing material..Coated plywood is generally reused considerably more than the plain plywood form.

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