Document evQBjrb62OjQJr95jGnGZz5Ep

Safety Engineering Tables shear, and bearing, as specified by the NLM A, are given in Table 47-C Allowable unit stresses for timber columns are as follows 1 Short Columns The safe load, in pounds per square inch of net cross-sectional area, for columns and other members stressed in compression parallel to the gram, with a ratio of un supported length to least dimension (Hd) not exceeding eleven (short columns) shall not exceed the allowable unit compression stress (c) parallel to grain for short columns, t e , P A=c 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 by the following formula P 7T*E 0 274E A 36(1/dy (l/dy 4 Notation P = total load, m pounds A = area, m square inches of net cross section P/A = the working stress or maximum load per square inch c = allowable unit stress in compression parallel to grain for short columns 1 = unsupported length of column, m inches d = least dimension of column, m inches E = modulus of elasticity P 2c at which -- = -- A3 5 The safe load on a column of round cross section shall not exceed that permitted for a square column of the same cross-sectional area 6 Columns shall be limited m maximum length to 1/d = 50 1576