Formwork - Design of Reinforced Concrete - page 624

Table 20.3 Suggested Working Stresses for Design of Wood Formwork

Class I formwork, single use or light construction Class II formwork, multiple use or heavy construction

Allowable unit stress, psi Allowable unit stress, psi

Species and Modulus Modulus

grade of Extreme of Extreme of

form framing fiber Compression Compression Horizontal elasticity, fiber Compression Compression Horizontal elasticity,

lumber bending ⊥ to grain ´ to grain shear psi bending ⊥ to grain ´ to grain shear psi

Douglas fir,
coastal
construction 1875 490 1500 180 1,760,000 1500 390 1200 145 1,760,000

Douglas fir,
inland
common
structural

1815 475 1565 180 1,760,000 1450 380 1250 145 1,760,000

Hemlock,
west coast
construction 1875 455 1380 150 1,540,000 1500 365 1100 120 1,540,000

Larch, common
structural

1815 490 1660 180 1,650,000 1450 390 1325 145 1,650,000

Pine, southern
No. 1 SR 1875 490 1625-1875 220 1,760,000 1500 390 1300-1500 175 1,760,000

Redwood,
heart
structural 1625 400 1380 135 1,320,000 1300 320 1100 110 1,320,000

Spruce, eastern,
1450 f
structural 1815 375 1310 160 1,320,000 1450 300 1050 130 1,320,000