382 STEEL STAND-PIPES AND ELEVATED TANKS ON TOWERS. CHAP. XL 



2. Stand-pipes are economical only in special cases: where their capacity is more important 

 than pressure, or where local conditions are such that an elevated tank is not required. 



3. Stand-pipes for the storage of oil are an exception. These are generally of very large 

 diameter, while the height may not exceed 40 ft. ; they are usually referred to as tanks. 



4. Stand-pipes are filled and emptied through pipes connected with their sides or bottom, 

 and are provided with manholes for cleaning purposes. 



5. In cold climates roofs are generally omitted on stand-pipes used for water supply, on 

 account of the formation of ice. In warmer climates there may be roofs in order to prevent the 

 water from becoming a breeding place for mosquitos, flies, etc. Stand-pipes used for the storage 

 of oil or other fluids from which rain-water is to be excluded should always be roofed. 



Loads. 6. The.dead load shall consist of the weight of structural and ornamental steel work, 

 and the roof construction, if any. 



7. The live load shall be the contents of the stand-pipe, the movable load on the eventual 

 roof, and the wind pressure. 



8. The eventual live load on the roof shall be assumed at 30 Ib. per sq. ft., or a 200 Ib. con- 

 centrated load applied at any point. 



9. The wind pressure shall be assumed at 30 Ib. per sq. ft. acting in any direction. The 

 surfaces of cylindrical stand-pipes exposed to the wind shall be calculated at two-thirds of the 

 diameter multiplied by the height. 



10. The eventual live load on the roof, if the .stand-pipe is roofed, shall not be considered as 

 acting together with the wind pressure. 



Stresses. n. All parts of the structure shall be porportioned so that the sum of the dead 

 and live load stresses shall not exceed the stresses given in Table III. 



TABLE III. 



Tension in plates forming sides or bottom of stand-pipes 12,000 Ib. per sq. in. of net area. 



Tension in roof construction 16,000 Ib. per sq. in. of net area. 



Compression in roof construction 16,000 Ib. per sq. in. reduced. 



Shear on shop rivets in roof, etc 12,000 Ib. per sq. in. 



Shear on field rivets (in stand-pipe plates) and bolts 9,000 Ib. per sq. in. 



Shear in plates 10,000 Ib. per sq. in. 



Bearing pressure on shop rivets 24,000 Ib. per sq. in. 



Bearing pressure on field rivets (in stand-pipe plates) 18,000 Ib. per sq. in. 



12. For compression members in the roof construction, the permissible unit stress of 16,000 

 Ib. shall be reduced by the formula: 



p = 16,000 70 l/r, 



where p = permissible working stress in compression, in Ib. per sq. in.; 



/ = length of member, from center to center of connections, in inches; 



r least radius of gyration of section, in inches. The ratio, l/r, shall never exceed 180. 



13. Stresses due to wind may be neglected if they are less than 25 per cent of the combined 

 dead and live loads. 



14. The average permissible pressures on masonry shall be as given in Table II, Part I. 

 Details of Construction. 15. The plates forming the sides of the stand-pipe shall be of 



different diameters, so that the courses shall lap over each other, inside and outside, alternately. 



1 6. The joints for the horizontal seams in the sides, and for the bottom plates, shall pre- 

 ferably be lap joints. 



17. For further information regarding riveted joints, etc., see Part I, Sections 16, 17, 18, 

 and 19. 



1 8. The minimum thickness of the plates forming the sides shall be J in. and ^ in. for the 

 bottom plates, except for oil tanks on a sand foundation. The bottom plates for ordinary stand- 

 pipes shall be provided with tapped holes, if in. in diameter, with screw plugs, spaced at about 

 4 ft. centers, to permit of filling with cement grout on top of the foundation of the masonry while 

 the bottom part is being erected, in order to secure proper bearing. 



19. Oil tanks of large diameter are generally set directly on a sand foundation, and do not 

 need any holes in the bottom plates for filling beneath with cement grout. In such cases, J in. 

 bottom plates will be sufficient. 



20. The bottom plates shall be connected with the sides by an angle iron riveted inside the 

 stand-pipe. This angle iron shall be bevel sheared for caulking along both legs. For the caulking 

 of plates, see Part I, Sections 22 and 23. 



21. On the side and near the bottom there shall be a 12 by 18 in. manhole of elliptical shape. 

 In the same manner, or on the bottom plates, flanges shall be provided for the connection of 



