THE STRESSES IN A STEEL WATER-TOWER. 139 



at the successive panel points are resolved into the planes of the 

 sides of the tower. 



Considering the side of the tower FAA'P ', the loads acting 

 thereon are as indicated (Fig. 37). The framing forms a canti- 

 lever truss anchored at F r and A'. The 



C A 



reactions resulting from the loads on this 

 cantilever can be computed readily from the 

 dimensions of the structure by the method of 

 moments and shears (2 Moments = o, I Hori- 

 zontal Comp. = o, and 2 Vert. Comp. = o). 

 Having determined the loads and reactions, 



the stresses in the truss members can be "~\F 



J,u u a 



solved by graphical analysis. Each post is 



common to two adjacent trusses of the tower, 



and its total stress is the algebraic sum of its stresses resulting 



from its membership in the two trusses. 



An inspection of the components of the shear at the top of 

 the tower (Fig. 36) will show in which sides of the tower the 

 maximum stresses occur for the assumed direction of the wind, 

 but the concurrent stresses in the adjacent sides or trusses must 

 be solved in order to determine the total stresses in posts. 



If the inclination of the sides of the tower changes at each 

 story, each story must be analyzed separately. The anti-reac- 

 tions at the base of one story become the loads at the top of the 

 next lower story. 



Loads on the Foundations. The reactions U and U 1 at 

 F r and A' in the above figure (Fig. 37) lie in the plane of the 

 side of the tower (i.e., the plane of the truss under consideration). 

 This plane being inclined p, the loads on the foundation resulting 

 are a vertical component, 



U cos p, or U 1 cos p, 

 and a horizontal component, 



U sin p, or U- L sin />. 



