CHAPTER XI. 

 STEEL STAND-PIPES AND ELEVATED TANKS ON TOWERS. 



DATA FOR DESIGN. The following data will be of assistance in the design of steel 

 stand-pipes and rlrv.nnl tanks on towers. For definitions of stand-pipes and elevated tanks 

 on towers, see the specifications in the latter part of this chapter. 

 Notation: 



h = distance in ft. of any point below the top of the stand-pipe or elevated tank; 

 d = diameter of the stand-pipe or elevated tank in feet; 

 r = radius of the stand-pipe or elevated tank in feet; 

 / = thickness of the shell in inches at any given point; 

 P = hydrostatic pressure in Ib. per sq. in. at any point = 0.434/1; 

 S = stress per vertical lineal inch of stand-pipe; 

 s = unit stress in Ib. per sq. in. in vertical section of stand-pipe; 

 5' = stress per horizontal lineal inch of stand-pipe; 

 s' = unit stress in Ib. per sq. in. in horizontal section of stand-pipe; 

 S" = stress per lineal inch along a circumferential line, due to wind; 

 s" = unit stress in Ib. per sq. in. in circumferential line, due to wind. 

 Formulas for Stresses in Stand-Pipes. The stress per lineal vertical inch of stand-pipe is 



= 62^-d _ 



2 X 12 



The stress per sq. in. is 



s = 2.6h-dft (2) 



The stress per horizontal lineal inch of stand-pipe due to the weight of stand-pipe W, is 



S' = W/(i2ir'd) = o.026W/d (3) 



The stress per sq. in. is 



s' = o.026W/(d'f) (4) 



For ordinary conditions the wind pressure is taken at 30 Ib. per sq. ft. acting on two-thirds 

 of the surface, or 20 Ib. per sq. ft. on the entire surface; while for exposed positions the wind pressure 

 may need to be taken as high as 45 Ib. per sq. ft. acting on two-thirds of the surface, or 30 Ib. 

 per sq. ft. on the entire surface. Recent Prussian specifications require that circular chimneys 

 be designed for two-thirds of 25 Ib. per sq. ft. At 30 Ib. per sq. ft. acting on two-thirds of the 

 surface (20 Ib. per sq. ft.) the bending moment at any distance h below the top, due to wind is 



M = 20 X d-h X h X 12/2 = I2od-h* (5) 



where M is in in.-lb. 



The stress in the extreme fiber of the shell is 



s" = M-yfl (6) 



Now y I2r, I = \ir(r\* r* 4 ) = t-*-r* (approx. r is in ft. 1 and / in in.) = /T-r l -i2 t (in in. 4 ). 

 Substituting y and / in (6) 



i.o6ft*/('-<f) (7) 



365 



