THE STRESSES IN A STEEL WATER-TOWER. 11$ 



mm (Fig. 19), is compression. Its amount equals the weight 

 of the portion of the structure above the plane in question. Or- 

 dinarily this is the weight of the tank plates and roof. In cold 

 climates it may be increased by ice adhering to the tank. There 

 is no appreciable direct stress on a horizontal joint resulting 

 from hydrostatic pressure. The compression per lineal inch 



W 



of circumference of the joint is , in which W is the weight 



in pounds supported on the whole circumference and r is the 

 radius in inches. 



The stress on a vertical joint of the cy Under is produced by the 

 hydrostatic pressure on the inside of the cylinder. This pres- 



lit r M Mft 



FIG. 19. 



FIG. 20. 



sure is normal to the surface, therefore radial, and its intensity 

 in pounds per square inch of surface is p = o.^^H. Assume 

 a ring one inch in height cut from the cylinder at a depth of H 

 feet from the top. The internal pressure will then be p pounds 

 per lineal inch of the ring (Fig. 20). 



Pass a diametral plane mn cutting the ring at m and n, 

 and consider the half to the right of mn. To maintain equilib- 

 rium of the half-ring the forces T m and T n must act at m and n 

 respectively. Then T m and T n equal the tension in the shell 

 at m and n. By symmetry T m =T n . 



