GRAIlsr PEESSTJRES IN STORAGE BINS. 5 



(a) In very shallow bins there is little difference in the vertical 



pressiires obtained for different values of Ic, while as the bins become 



V 

 deeper j^ for Ic = 0.3 rapidly approaches a value twice as great as for 



^ = 0.6. 



(b) In snallow bins the value obtained for the lateral pressures for 

 ]c = 0.3 are about one-third less than for Ic = 0.6, but as the bins become 



L 



deeper -^^ for Ic = 0.3 rapidly approaches the same value as for Tc = 0.6. 



(c) As most grain bins are deep bins, the best general value for 

 ^ is 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 waUs 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 Tc is taken 

 equal to 0.3. Most designers, however, work on the assumption that 

 0.6 is more nearly the correct value for Tc 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 hj^draulic radius. For round or 

 other regular bins 4:XR = D where i? = 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 Ic equals 0.6 and /x' equals 0.4167. The product 

 4 X ^ X /u' 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 Ic and /x^ by computing 

 a compensated value for D which may be designated by D\ 



Original formula for regular bins : 



DxW /, _ 1 X 



4x/^Xm\ ^ 4xfcyxg j 



