| | Cr. str. at E.L. = Crushing strength at elastic limit. | | Cr. str. at max. ld. = Crushing strength at maximum load. | |-----------------------------------------------------------------------------------------------------------------------------------------------| |----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | TABLE XXII TABLE XXII | |----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | [b]WORKING UNIT-STRESSES FOR STRUCTURAL TIMBER[c] | | EXPRESSED IN POUNDS PER SQUARE INCH | | (From Manual of the American Railway Engineering Assn., 1911, p. 153) | |----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | NOTE.--The working unit-stresses given in the table are intended for railroad bridges and trestles. For highway bridges and trestles the unit-stresses may be increased | | twenty-five (25) per cent. For buildings and similar structures, in which the timber is protected from the weather and practically free from impact, the unit-stresses may be | | increased fifty (50) per cent. To compute the deflection of a beam under long-continued loading instead of that when the load is first applied, only fifty (50) per cent of the | | corresponding modulus of elasticity given in the table is to be employed. | |----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | | BENDING | SHEARING | COMPRESSION | |