1 82 TOWERS AND TANKS FOR WATER-WORKS. 



FIG. 50. 



" In addition to the above critical stresses in the circular girder, 

 it should be observed that if this girder fulfils the purpose for 

 which it was intended, that of transferring 

 the weight of the tank to the posts, it will 

 be subjected to a large bending moment 

 immediately over the posts, of such nature 

 as to cause tension in the upper flange and 

 compression in the lower flange. This 

 compression in the lower flange has to be 

 added to the stresses already given, and in 

 addition it should be noted that each seg- 

 ment of the circular girder would have a 

 tendency to rotate inwards at the top of 

 the post connection owing to the fact that 

 it is not straight between posts. Cer- 

 tainly the circular girder should have been made continuous as 

 provided for in the original plans, and the fact that it was 

 built in segments renders the upper flange incapable of carrying 

 the tension over the posts, and this tension, so far as the friction 

 from the heavy load can do this, would be transferred to the 

 flanged portion of the conical bottom, tending to disrupt it along 

 a radial line. 



" The writer does not consider it necessary or even desirable 

 to use a circular girder under the sides of the tank. There is 

 no way of preventing the tank itself from acting as a girder to 

 carry the loads to the posts if we desired, and the writer considers 

 that it ought to be strengthened sufficiently to enable it to do 

 this with safety. The writer would not put any manhole in 

 the lower ring of plates of the tank. 



11 In the case of the Fairhavcn tank, the lowest side ring of 

 plates appears to have been made of just about the thickness 

 that good practice would require for a stand-pipe of diameter 

 and height equal to the tank above this point. Now, the conical 

 bottom at its junction with the sides of the tank is subjected to 



