Document Gpq2760VNk78pNr6yOaRM6mY

TABLE 46-C ALLOWABLE UNIT STRESSES, STRUCTURAL TIMBER (Pounds per square inch) Material A* (col umns) Bending and tension Com pression0 Shearl Bear ing t Modulus of elasticity Douglas-fir Parallel to grain Across the grain Oak Parallel to grain Across the grain Spruce Parallel to grain Across the grain Long leaf yellow pine Parallel to grain Across the grain 23 4 23 7 21 2 234 1,500 1,300 1,200 1,400 1,200 1,100 1,100 1,200 100 110 100 120 1,500 350 1,500 500 1.200 250 1,400 300 1,600 000 1.500,000 1.200,000 1,600.000 From General Engineering Handbook, O Rtiurke (McCraw-Hill Book Co ) *On lengths not greater than eleven times the least dimension Otherwise, use column formulas (In timber-|Oint designs these values may be increased 50 per cent (These values are for joint design, and for bearings (ess than 10 in long See following notes Timber, Structural Grade (Dry) Allowable unit stresses in bending, compression, shear, and bearing, as specified by the NLM A, are given in Table 46-C Allowable unit stresses for timber columns are as follows 1 Short Columns The safe load, m pounds per square inch of net cross-sectional area, for columns and other members stressed in compression parallel to the grain, with a ratio ot un supported length to least dimension (lid) not exceeding eleven (short columns) shall not exceed the allowable unit compression stress (c) parallel to grain lor short columns, i e , P A=t 2 Intermediate Columns For columns with a ratio of unsupported length to least dimen sion greater than eleven but less than K (intermediate columns), the following formula shall be used until the reduction in allowable stress equals one-third the stress permitted for short columns 3 Long Columns For columns with a ratio of unsupported length to least dimension greater than K (long columns), the safe load shall be determined bv the following formula P w-'E 0 274 E A 36(1 W (1/dP (Continued on next page ) 1451