SILOS OF REINFORCED CONCRETE 219 



(3) The vertical reinforcing bars in the wall may remain of the same 



size, the bars being spaced the same distance apart, in all silos. 



(4) If the diameter of the silo be changed, the cross-sectional area of 



iron in the horizontal reinforcement, per foot of height of the 

 silo, must be changed proportionately. 



(5) In all silos of the same diameter, the same amount of horizontal 



reinforcement per foot of height of the silo is always necessary 

 for sections of wall of equal distance from the top of the silo, 

 regardless of total height. 



If the silo shown be built over 30 feet in height, the horizontal rein- 

 forcing bars in the lower part of the wall (considered to be added to the 

 silo illustrated) should be of ^-inch round iron bars spaced 6 inches 

 apart. This will suffice for silos up to 40 feet in height. 



Experience gained in the United States of America seems to indicate 

 that, if silos are built higher than 40 feet, it is necessary to lead away 

 the silage juices, expressed by the great superincumbent weight, from 

 the bottom of the silo by means of a drain pipe. It is therefore probably 

 inadvisable to build silos higher than 40 feet. 



Emptying Doors. — These are constructed, as shown in Fig. 168, of 

 hardwood. 



The loss of strength, due to the openings for the emptying doors 

 interrupting both the horizontal and vertical reinforcing bars, must be 

 made up. This is effected by imbedding a 1-inch diameter bar, having 

 the shape of an oblong frame, in the concrete surrounding each doorway, 

 in order to strongly reinforce all four sides of the latter. To the oblong 

 frame so imbedded, the horizontal and vertical reinforcing bars are 

 attached by looping back, tying with wire, and bending over the end to 

 form an anchor as shown in Fig. 168 (plan). 



In order to make it possible to insert the door (as a mould) while the 

 silo is being built, this oblong frame is not in one piece, but the top side 

 consists of a separate bar AA with eyelets, at the ends, which slip over 

 the vertical sides of the frame. 



Ladder to Filling Door. — An iron ladder, which is detailed in Fig. 169, 

 is provided. 



It is supported on a concrete base, and is also held by lugs which are 

 built into the wall of the silo. 



In order to insert these lugs, the outer form or mould for the silo wall 

 will have to be provided with slot holes to receive them. 



