CAMBRIA STEEL. 405 



the upper dotted line indicates the limit of deflection for the kind 

 of wood for which the deflection coefficient is given, corresponding 

 to a modulus of elasticity of 500000 pounds per square inch, 

 which should be considered in cases where the deflection should 

 be more closely limited. 



The coefficients of deflection for Cedar corresponding to moduli 

 of 700 000 and 350 000 may be obtained by multiplying those 

 of the table by ty and ty respectively, and for Spruce and 

 Eastern Fir corresponding to moduli of 1 200 000 and 600 000 by 

 multiplying those of the table by and f respectively. 



The full zig-zag line in the table gives the limits of the safe loads 

 corresponding to the allowable shearing stress along the neutral 

 axis of the beam, The safe loads above the line, which are based 

 upon the extreme fibre strains, will produce shearing stresses 

 along the axis or with the grain in excess of that allowable, which, 

 in the case of White Pine and the other woods of this table, is 

 100 pounds per square inch. 



The position of this line, which indicates the limit of safe loads 

 for shearing along the neutral axis, was determined by the aid 

 of the following formula: 



in which 



W = safe load in pounds uniformly distributed. 

 d = depth of beam in inches. 

 b = breadth of beam in inches. 



s = allowable shear in the direction of the grain in pounds per 

 square inch. 



Explanation of the Table of Safe Loads for Rectangular 

 Beams of Short-leal Yellow Pine. 



The table is calculated for an allowable fibre stress, for flexure, 

 of 1 000 pounds per square inch. 



The deflection coefficients are figured for a modulus of elasticity 

 of 1 200 000 pounds per square inch, but may be used for other 

 moduli, after obtaining the corresponding coefficients by pro- 

 portion as heretofore explained. 



The lower dotted line across the table indicates the limits of 

 spans for which the safe load will produce deflections greater than 



