GRAIN STORAGE 



its action. Assuming that this consideration is correct, it 

 is possible to obtain values which could be used in the de- 

 sign of extremely high cribs. 



It has been found by a number of experimenters that 

 the ratio of lateral to vertical pressure of grain varies from 

 0.3 to 0.6. The vertical pressure, or pressure on the bottom 

 of a bin, rarely exceeds 6 pounds per square inch, this value 

 being reached with a depth of about 50 feet, which is much 

 deeper than would be the granary on any ordinary farm. The 

 pressure for a depth of 20 feet, which would be the maximum 

 for the average granary, will not exceed 4 pounds per square 

 inch and at a depth of 10 feet one-half this value is a safe 

 assumption. 



Some rather interesting conclusions have been made as 

 a result of the experiments that have been conducted. It 

 was found that the lateral pressure of grain on bin walls 

 increases very little after a depth of 2,y 2 to 3 times the dia- 

 meter of the bin is reached. Moving grain also indicated 

 a somewhat greater pressure than that of grain at rest, the 

 variation under ordinary conditions never exceeding 10 per 

 cent. The maximum lateral pressures that were measured 

 occurred immediately after filling. Using the results of 

 experiments which have been made to determine the lateral 

 pressure of coal bins, and assuming that the weight of ear 

 corn is 60 per cent of that of coal, we will obtain for a total 

 lateral pressure on a section of crib wall I foot long and 

 20 feet deep approximately 1,500 pounds. In a depth 

 of 10 feet this value is about 400 pounds, showing that with 

 deep cribs, especial attention must be given to the framing 

 in order to make it sufficiently strong to resist the heavy 

 strain. It is doubtful if a crib deeper than 20 feet will be 

 used on the ordinary farm on account of the difficulty of 

 elevating the grain. When higher cribs than these are used, 

 it is advisable to consider them as coming under the head 

 of elevators, and their design should be left to the experi- 

 enced engineer. 



Foundations. Since the foundation of grain storage 

 buildings must support not only the weight of the super- 

 structure of the building, but that of the grain also, it fol- 

 lows that the foundation is an extremely important feature. 

 The best practice at the present time is to make use of con- 

 crete for the foundation. A good foundation can be made 

 of a i '.2,1/2. :$ mixture of concrete, the foundation wall ex- 



Four 



