DESIGN OF STEEL GRAIN BINS. 



327 



supported by the bin walls above a horizontal joint 75 ft. below the top of the grain. From 

 filiation (13) the grain carried by the bin walls |x r liiu-.il foot of circumference of bin, where 

 w 50 Ib. per cu. ft.; M' 0.375; k - 0.40, also R 25/4 6.25, and 



50 X 6.25 

 10,415 Ib. 



75 - 



6.25 



0.4 X 0.375 



The weight of the steel bin above the joint may be taken as 1,250 Ib. per lineal foot of joint. 

 The horizontal riveting should then be designed for a shear of 11,665 Ib. per lineal foot of joint. 

 Assume that the plates are | in. thick and the rivets } in. in diameter. For allowable stresses of 

 16,000 Ib. per sq. in. in tension, 11,000 Ib. per sq. in. in shear, and 22,000 Ib. per sq. in. in com- 

 pression; then, Tablell4,Part II, the value of a j in. shop rivet in single shear = 4,860 Ib., and a 

 field rivet is f of 4,860 = 3,240 Ib., and in compression = 6,190 Ib. for shop rivets and = 4.127 

 Ib. for field rivets. For a lap joint therefore the spacing should not be greater than 3,240 X 12 

 -T- 11,665 = 3.25 in., requiring but one row of rivets. 



Stresses in a Steel Bin Due to Wind Moment. If M is the moment due to the wind acting 

 on the bin above the horizontal joint, then the stress per lineal foot of joint due to wind moment 



be 



** (approx.) and 5 = (15) 



2! 



but / = 



where all dimensions are in feet. For a wind load of 30 Ib. per sq. ft. on two-thirds of the tank 

 (20 Ib. per sq. ft. on the entire surface of the tank) the wind stress will be S = 2,865 Ib. per lineal 

 foot. The spacing therefore should not be greater than 3,240 X 12 -5- (11,665 -f- 2,865) = 2f in. 

 Stiffeners. In large circular steel bins the thin side walls are not sufficiently rigid to support 

 the weight of the grain and it is necessary to supply stiffeners. For this purpose angles or Z-bars 

 may be used. Experience has shown that bins' in which the height is equal to or greater than 

 about 2$ times the diameter do not need stiffeners. There is at present no rational method for 

 the design of these stiffeners or the stiffeners in plate girders. In Fig. 9 will be seen the details 

 of a steel bin of the Independent Steel Elevator with Z-bar stiffeners. Angle stiffeners were 

 used in the bins of the Electric Elevator, Minneapolis, Minn. 



c w'-e" -H<- w'-o'- *K M'-I'- -H 



FIG. 3. PLAN OF STEEL STORAGE BINS FOR A STEEL ELEVATOR. 



Circular steel bins are used for storage in large elevators and may be used for a complete 

 elevator as in Fig. 3. The space between the bins is sometimes used for auxiliary storage. The 

 circular bin walls are stiffened by means of vertical channels, and the auxiliary bins are cross-braced 

 with steel rods. Complete details of circular steel bins for the Independent Elevator, Omaha, 

 Neb., are shown in Fig. 9. 



