406 CAMBRIA STEEL. 



sfa of the length of the beam. Values above the line will give 

 less deflection than this, and those below will give greater, based 

 on a modulus of 1 200 000 pounds per square inch. Similarly, 

 the upper dotted line indicates the limit of deflection correspond- 

 ing to a modulus of elasticity of 600 000 pounds per square inch. 

 The full zig-zag line across the table indicates the limiting spans 

 and loads based on the allowable intensity of shearing stress along 

 the neutra) axis of the beam. The values above the full zig-zag 

 line correspond to shearing stresses greater than the allowable 

 stress in the direction of the grain for Short-leaf Yellow Pine, 

 while those below the line correspond to shearing stresses less 

 than that allowable, which, in this case, is assumed to be 100 

 pounds per square inch. 



Explanation of Tables of Safe Loads for Rectangular 

 Beams of White Oak and Long-leaf Yellow Pine. 



This table is computed for an allowable fibre stress of 1 200 

 pounds per square inch, for flexure, and the deflection coefficients 

 are calculated for a modulus of elasticity of 1 500 000 pounds per 

 square inch. 



The limit for a deflection of T 7 of the span is indicated by the 

 lower dotted zig-zag line on the tables, the values below which 

 correspond to deflections greater than, and those above to 

 deflections less than, the limiting deflections. The upper dotted 

 zig-zag line similarly indicates the limits of deflection for a 

 modulus of elasticity of 750 000 pounds per square inch. 



The lower full zig-zag line indicates the limit of allowable 

 shearing stress along the axis corresponding to the allowable 

 intensity, for Yellow Pine, of 150 pounds per square inch. 



Similarly, the upper full zig-zag line indicates the limits for 

 shearing along the axis for White Oak based on an allowable 

 intensity of 200 pounds per square inch. 



BEARING AT POINTS OP SUPPORT. 



Care should be taken in designing to provide sufficient bearing 

 at the points of support so that the allowable intensity of com- 

 pression across the grain, as given in the tables on pages 409 to 

 415, is not exceeded. 



This may be obtained, where necessary, by the use of corbels 

 or bearing plates of harder wood arranged so as to give a large 

 bearing area against the softer beam. 



