THE STRESSES IN A STEEL WATER-TOWEK. 137 

 U M 



Thus it appears that the maximum vertical load due to wind 

 pressure, at the top of any post, results when the wind is assumed 

 in the direction of the diagonal passing through that post. 



The stress in each post resulting from a given direction of 

 the wind can be determined readily from the above relations. 

 The method of analysis is applicable to a tower having any number 

 of posts. 



The vertical load (either tension or compression) at the top 

 of a post being determined, the stress in the post is the product of 

 the vertical load and the secant of the angle of inclination as 

 shown under gravity stresses, and, as in the case of gravity stresses, 

 there is a horizontal component at the top of the post. As these 

 horizontal components at the tops of the several posts are not 

 in equilibrium, they must be transmitted through the tower to 

 the foundations. 



Considering the case in the adjoining figure (Fig. 36), these 

 horizontal components are about as represented by the arrows 

 marked c, the dotted arrow, P, indicating the direction of the 

 wind. The value of each must be determined from the vertical 

 load on its post resulting from the assumed direction of the wind. 

 The horizontal components will be combined with the direct 

 horizontal shears at the tops of the posts and the resulting stresses 

 in the tower determined. 



The set of horizontal forces previously referred to consists 

 of the direct shears at the tops of the posts. It will be assumed 

 that the tank, circular girder, and horizontal curved girder are 

 capable of distributing the shear equally among the posts, and 

 that the segments of the girders from post to post are capable 

 of acting as struts of the tower bracing. Then the shear at each 



