300 TIMBEES AND THEIE USES 



at the weakest points and follows the lines of 

 least resistance. The plane of failure, as visible 

 on radial surfaces, is horizontal, and on the 

 tangential surface it is diagonal." 



When end compression parallel to the grain 

 is applied to a longer column, the load tends to 

 shorten the column. Should the column be very 

 long in comparison with the diameter, failure 

 does not take place by buckling or splitting or 

 shearing, but by bending. The maximum stress 

 being at the point where the greatest bending 

 takes place and on the concave side. By 

 supporting the column so that bending cannot 

 occur, failure will take place by splitting or 

 buckling. Very frequently, when end compres- 

 sion parallel to the grain is appHed to a short 

 column, failure takes place by shearing (Fig. 

 85). 



This shearing stress may be calculated by 

 dividing the load in pounds necessary to cause 

 the shear, by the area of the cross section of 

 the short column in inches. Supposing, there- 

 fore, that the cross section is one inch square 

 the shearing stress will equal the load in pounds. 

 Thus should it require a load of 6,720 lbs. to 

 cause a short column 1 inch square to shear, the 

 shearing stress will be 6,720 lbs. per square 

 inch. 



" Tests to ascertain the relative strength of 



