GRAIN PRESSURES IN STORAGE BINS. 5 
(a) In very shallow bins there is little difference in the vertical 
pressures obtained for different values of k, while as the bins become 
deeper . for k=0.3 rapidly approaches a value twice as great as for 
k=0.6. 
(b) In snallow bins the value obtained for the lateral pressures for 
k=0.3 are about one-third less than for k = 0.6, but as the bins become 
deeper Zz for k=0.3 rapidly approaches the same value as for k=0.6. 
(c) As most grain bins are deep bins, the best general value for 
kis 0.6. This gives the maximum value for the lateral pressure and 
also gives the maximum value for the vertical load carried by the 
bin walls. It is very essential that the determination of the bearing 
area of the walls and in some cases the design of the foundation, be 
based on maximum values for the vertical wall loads. 
Possibly it would seem best in designing the bin bottom to use the 
maximum values for the vertical pressure obtained when k is taken 
equal to 0.3. Most designers, however, work on the assumption that 
0.6 is more nearly the correct value for & than 0.3 and use the lesser 
values for the vertical pressures. 
DETERMINATION OF UNIT PRESSURES IN RECTANGULAR OR OTHER 
IRREGULAR BINS. 
Accepting Janssen’s formula as a general one applying to all forms 
of bins, we can conclude that the unit pressures in any bin are equal 
to those in any other bin of the same hydraulic radius. For round or 
other regular bins 4x R=D where &=hydraulic radius. Then the 
hydraulic radius of any bin multiplied by 4 will give a value equal to 
the diameter of the equivalent round bin and the pressure factors may 
be obtained from Table 1. : 
DETERMINATION OF UNIT PRESSURE FOR VARIOUS GRAINS IN BINS 
OF DIFFERENT MATERIALS. 
Tables 1 and 2 were developed on the assumption that for wheat in 
concrete bins k equals 0.6 and yp’ equals 0.4167. The product 
4k Xp’ thus becomes equal to 1 and Wwas taken equal to 50 pounds. 
These tables may be readily used to figure the unit pressures and 
reinforcing in any bin for any assumed value of k and y’, by computing 
a compensated value for D which may be designated by D’. 
Original formula for regular bins: 
Dx W 1 
= yes! ED) 
D 
