236 TOWERS AND TANKS FOR WATER-WORKS. 



the several building materials most generally used in stand- 

 pipe foundation-work and compiled from various recognized 

 authorities : 



WEIGHT OF MASONRY IN TONS PER. CUBIC YARD. 



Weight of granite or limestone, dressed throughout (ashlar). 2.2 tons. 



" " " " rough rubble 1.8 " 



" " sandstone, ashlar 1.9 " 



" " " rubble 1.6 " 



Brick masonry, medium work 1.6 " 



Ordinary concrete... 1.4 " 



Designing Foundations, Including Anchorage and Cap- 

 ping. To design a suitable foundation for a particular struc- 

 ture the normal weight must first be determined or assumed. 



Considering a proper design for a stand-pipe 24 ft. dia. X 

 1 20 ft. in height, and whose actual weight was considered as 

 80 tons, and whose dimensions would add 1696 tons as the 

 weight of the water, or a total of 1776, and which weight 

 should be first considered as acting over a base equal to the 

 area of the structure, or 452.4 sq. ft., or with a unit-stress 



W 1776 



equal to r- or- - = 3.9 tons per sq. ft. 

 A 45 2 -4 



Neglecting for the moment the weight of the foundations, 

 and which can only be obtained after a suitable design has 

 been determined upon, to secure the maximum pressures per 

 unit of bearing-surface, in addition to the normal weight di- 

 vided by the area, there must be added the forces due to 

 flexure or to the effect of the wind upon the cylindrical sides 

 of the stand-pipe and as applied through its leverage to the 

 base and over the area to be covered by the foundations. 



Ml 



Substituting the proper values in the formula j- , or for 



a cylindrical figure 24 ft. dia. X I2O ft. in height, and taking 

 30 Ibs. per sq. ft. of diametral surface, as has been ex- 

 plained, as the action of the wind upon the sides of the cylin- 

 der, the force exerted by this variable quantity is 



