Timber mechanics and 

 structural research 



Sixty percent or more of the Nation's 

 J^awed timber production is used in 

 building and housing. The foundation 

 of proper and efficient use of wood for 

 construction purposes is accurate knowl- 

 edge of its mechanical properties — its 

 strength in tension, bending, compres- 

 sion, and shear, its toughness, rigidity, 

 and other qualities that determine its 

 resistance to all kinds of stresses. In 

 these respects, as in others, wood was for 

 long the "unknown material." Vari- 

 able factors of species and growth were 

 not accurately accounted for in strength 



determinations, and the rough esti- 

 mates and traditional practices of the 

 past have led to wasteful and unsatis- 

 factory use of untold millions of feet of 

 timber. 



Strength tests 



To supply dependable data, it was 

 first necessary for the Laboratory to 

 devise proper mechanical and statistical 

 methods for evaluating strength prop- 

 erties and then to proceed with a long 

 and laborious testing program. The 



Data from, mechanical tests of wood set standards for selection, grading, 

 and engineering design. 



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