TWELFTH ANNUAL YEAR BOOK— PART X 489 



Recommendations for vertical reinforcing have eminated from several 

 apparently reliable sources. Careful and extensive Investigation in silo 

 work In the past four years have failed to indicate to me that vertical 

 reinforcement in the wall is necessary except at the door frames. Such 

 reinforcement does no harm, but it does cost money and requires time to 

 prepare and place and so far as I have been able to learn no failure has 

 ever occurred on account of its absence. It is of course reasonable to 

 suppose that horiiionta] reinforcement could be far enough apart to make 

 this necessary, but where one-fourth to one-half inch steel is placed as 

 often as Is necessary there seems to be no reason for the vertical steel. 

 In the case of the continuous door frames in which the steel extending 

 across the doorway is several feet apart there should be vertical steel in 

 the dcor jams sufficient to transfer the stress of horizontal steel down 

 to the steel extending across the doorway. 



MAKING FOUXDATIONS. 



For walls six inches in thickness and 40 feet in height the weight upon 

 each foot of circumference will probably not be far from 3.000 pounds. 

 The weight of the roof and the friction of the silage settling add some- 

 what to the actual weight of the concrete itself. 



It is comm.on on good soils to allow 2.5 tons per square foot on soil 

 bearing surface. It is convenient to make the foundation from 18 to 24 

 inches wide; this reduces the pressure to one ton per square foot or less 

 and makes it very safe. This can be conveniently arranged by simply, 

 digging a wide trench around the outside of the pit. The pit should only 

 be deep enough to get the foundation below the frost line. In building 

 the foundation the excavation can be done neatly and only inside forms 

 are necessary. There really seems to be no reason why the wall below 

 the ground should be thicker than that above. 



THE WALLS. 



Concrete silo walls may be divided into two divisions, monolithic and 

 block. The block has the advantages already cited for clay blocks, but 

 more labor is required in the construction of block than monolithic 

 silcs on account of the extra labcr in manufacturing the blocks. 



It sometimes happens that a man wishing a silo is handy and can 

 spare time to work upon it, but can not spare any more cash than is 

 absolutely necessary. If in such a case the owner can get sand or gravel, 

 the cement block silo Is the one for him to build for he can build it for 

 less cash outlay than any other form of silo. In regard to blocks, both 

 hollov.r and solid kinds are used. In some cases extremely thin solid 

 blocks have been used. 



In mcst cases, however, where labor must be considered a very Im- 

 po'tant ccst factor the monolithic silo will be the cheaper. The mono- 

 lithic v/alls have been built both double and single, the first costing con- 

 ?IderaI)ly more for labor, material and forms. There are of course some 

 advantages in hollow wall construction, yet it is very qeustionable If the 



