42 Concrete Silos 



of wood is such that it shrinks when dry and swells 

 when wet. The permanency of a wood stave silo 

 depends entirely upon its maintaining a constant 

 rigidity of structure. It consists of staves set on end, 

 held firmly in place 

 by hoops. As long 

 as the hoops remain 

 tight the structure 

 will be comparative- 

 ly rigid and stable. 

 As soon as the hoops 

 become loose, it be- 

 comes in the highest 

 degree unstable. In 

 the modern wood 

 stave silo the staves 

 are matched and fit- 

 ted together by 

 tongue and groove. 

 The tongue and 

 groove are from % 

 to % inch in depth. 



The extreme Circum- Effect of Shrinkage of Wood Staves 



ference of a silo 16 feet in diameter is about 50 feet. It 

 would take very little shrinking to reduce this 50 feet 

 sufficiently to separate a tongue from a groove. Then, 

 unless some method is adopted for holding the stave 

 in place, the stave will fall out and the silo be in 

 imminent danger of collapse. If the hoops become 

 loose so as to destroy the rigidity of the structure, it 

 may be worked in any direction by every light wind. 

 A single half day of hot weather is sometimes 

 sufficient to shrink the staves on such a silo to such 

 an extent that every hoop will need to be tightened 



