TIMBEE TESTING 299 



Compression Tests. These tests are usually 

 carried out upon short columns of wood, cut in 

 such a manner that compression takes place 

 parallel to the grain of the wood. The ends of 

 the column are planed exactly parallel to one 

 another and the grain of the wood under test 

 must be parallel to the sides of the column. 

 Should the grain and the sides not be parallel, 

 the short column, when under compression, will 

 merely bend sideways with a tendency to slip 

 from its support (Fig. 96). Load is appUed 

 to the short column up to the point of failure 

 which may take the form of bending, buckhng 

 (Fig. 90), sphtiting (Fig. 92), or shearing (Fig. 

 86), or a combination of one or more (Fig. 87). 

 The nature of the failure. depends on the struc- 

 ture of the wood under test and on its moisture 

 content. 



Tests in America have shown that " the 

 transverse strength of beams at elastic limit is 

 practically equal to the compressive strength 

 of the same material in short columns." 



It seems fruitless to describe in detail the 

 various forms of fracture, seeing that the 

 fractures are not in any way typical of definite 

 woods. Thus several short columns, of the 

 nature we have described, cut from different 

 parts of the same log of wood, will show different 

 forms of failure. " In any case the failure starts 



