174 TOWERS AND TANKS FOR WATER-WORKS. 



Method of Anchorage. Beside 'those above described, 

 suitable connections for the anchor rods must be designed and 

 the number and size of the rods determined. 



The method and formulae given at length on page 87 are of 

 general application. 



Analyzing the stresses of the 24 ft. by 120 ft. stand-pips 

 under consideration, we find from rough calculation that the 

 weight of the metal or the " dead " weight is some 85 tons, 

 hence M = 86,400x7 20 = 62, 2 08,000 pound-inches. 



The area A of the tank being 65,144, the maximum bending 



M 62,208,000 



stress per circumferential inch is.5-r or - , gives 



** 5> I 44 



955, which multiplied by the length of the arc included between 

 the anchor rods (assuming 10 to be sufficient, and spaced alorg 

 the outer circumference of the tank, but sufficiently removed to 

 allow for the connection and for the use of a tightening wrench) 

 and to an assumed radius of 12 ft. 3 inches, the circumferential 

 included arc would be 92.4 inches which, when multiplied by the 

 unit stress, 955, would produce a total maximum wind reaction 

 of 87,242 Ibs. acting on any one rod. The weight of the tank 

 being estimated at 170,000 Ibs., the net stress would be 87,272, 

 less 17,000 or 70,272 Ibs., which divided by the allowable work- 

 irg stress of 15,000 Ibs. gives a cross-section area of rod equal to 

 4.685, or selecting the nearest approximate size, the required rod 

 would be 2\ inches in diameter. 



Where the resultant of the forces passes too close to the base 

 it is frequently considered good practice to add stiffening braces 

 at intervals along the outer circumference of the tank. These 

 generally consist of a pair of angles bent to bracket form with a 

 web of steel plate riveted between. These braces give a greater 

 leverage against the overturning moment. 



