DETAILS OF STEEL TANKS. 



as in Fig. 3. Then the maximum vertical stress in column I will occur on the leeward side when 

 the wind is blowing in tin- dine (ion i-i. If M is tin- wind moment about the axis A-B, the 

 moment of the stresses in the column about axis A-B will be equal to M. In a tower with 8 

 .columns as in Fig. 3 we have (stress i) X 2r + (stress 2) X 4r-cos 45 - M. 



But Stress I is to Stress 2 as r is to r -cos 45; and Stress I (zr + 2r) M. Stress I JW/4r, 

 ami Sm-iss 2 = o.jM/^r. In a 6 column tower the stress in the most remote post is M/y and 

 in each of the others is J M/y. In a 4 column tower the stress in each column is M/2r. If the 

 columns are vertical the maximum stresses will occur at the foot of the columns; if the columns 

 are inclined the stress should be calculated at both the top and the bottom. The maximum 

 stresses will be the sum of the dead and wind load stresses. 



Having calculated the vertical components of the stresses in the columns, the stress in the 

 column will be equal to the vertical component multiplied by the secant of the angle between the 

 column and a vertical line. 



A 

 \5 



X 



\ 

 \ 

 \ 

 I 



Wmcf 



If the upward pull of the columns on the windward side is greater than the dead load when 

 the bin is empty the column must be anchored down. The masonry footing should have a 

 weight equal to at least one and one-half times the resultant upward pull. 



DETAILS OF STEEL TANKS. The standard plans in Fig. 10 and Fig. u and the Jack- 

 son, Minn., tank in Fig. 6, show the plates in alternate courses of different diameters, while the 

 standard details of the Chicago Bridge and Iron Co. in Fig. 8 shows the plates telescoped with 

 the edge of the plate for caulking on the inside so that it may be caulked from above. The stand- 

 ard specifications given in the last part of this chapter, also the specifications of the American 

 Railway Engineering Association in the last part of this chapter both require that the plates in 

 alternate courses be of different diameters as shown in Fig. 10, Fig. u, and Fig. 6. 



Hemispherical or segmental bottoms are now quite generally used, the conical bottom being 

 rarely used on account of the difficulty in making a satisfactory connection to the tank cylinder. 

 Spherical tank bottoms are used to a limited extent. 



The standard details of the Chicago Bridge and Iron Co. for circular water tanks and hemis- 

 pherical bottoms are given in Fig. 8, and the standard column details are shown in Fig. 9. 



The properties for water tight joints together with shearing and bearing values of rivets are 

 given in Table I la. Standard plans for a 95,000 gallon tank on a 100 ft. tower are given in Fig. 10; 

 while standard plans for a stand-pipe 20 ft. in diameter and 90 ft. high are given in Fig. 1 1. Table 

 Ha and Fig. 10 and Fig. II were prepared by Mr. C. W. Birch-Nord to accompany the standard 

 specifications printed in Trans. Am. Soc. C. E., VoL 64, and partially reprinted in this chapter. 



25 



