36 SILOS: CONSTRUCTION AND SERVICE 



any other masonry material, the outward pressure must be 

 taken care of or resisted by steel placed in or around the wall, 

 preferably in the wall, as it is then protected from rust. In 

 the earlier forms of this silo, as in the concrete and stone 

 silos, wooden door frames were used. 



As already suggested, the choice between clay products 

 and concrete will usually depend upon the local conditions 

 and the supply of these materials. Therefore, it was only 

 natural, while collecting material for the publication of 

 Bulletin 100 of the Iowa Agricultural experiment station, 

 that the author put forth an effort to design a successful, 

 economical, and durable silo for localities in which materials 

 for concrete construction were scarce and expensive. From 

 this effort has resulted the Iowa silo, described in Bulletin 

 117, the distinguishing features of which are a reinforcing 

 system and a door-frame design for bricks or blocks, either 

 clay or cement. The fact that it was developed in portions 

 of the state where concrete material was scarce, resulted 

 in almost exclusive use of hollow clay blocks or building 

 tile. 



The door frame was built of reinforced concrete, molded in 

 the form of either individual or continuous doors. A 

 special and simple reinforcing system was designed. The 

 door jambs are reinforced vertically and are tied together 

 across the door opening by a half more steel than is used in 

 the same height of the wall. Heavy wire is used in the mor- 

 tar joints extending around the silo and secured to the ver- 

 tical steel in the door jambs. Considerable time and effort 

 were spent upon the development of a convenient scaffold, 

 modifications of which are used by most of the Iowa silo 

 builders. At present this silo has established itself as one of 

 the economical and practical types of silo in use. Like any 

 other silo the general precautions to be taken are to 



