92 



DAMS AND HEADWORKS 



2. Sliding gates. 



3. Tilting gates. 



4. Tainter gates. 



5. Rolling gates. 



All cf these with the exception of the first class require that piers 

 be provided on the crest of the dam, between which they may be 

 supported. The number of these piers and spillway sections 

 depends then on the maximum length to which the gates can be 

 successfully built. 



Stationary Flashboards. This arrangement simply consists 

 in placing a row of wooden panels on top of the dam crest, and 

 supporting them by iron pins which are set vertically in holes 



Up-stream side 



FIG. 43. Stationary Flash-board Design. 



previously provided in the concrete structure, as shown in Fig. 43. 

 These pins are so dimensioned that when the water reaches a 

 certain elevation they will give way and readily release the boards. 



R. Muller (" Engineering Record," August 22, 1908), gives the 

 following formula for calculating the head of water that will 

 cause the iron pins to bend. It is based on Wayne iron pins: 



2 



in which 



X = height of water in feet above the dam crest when pins 



begin to bend; 



d = diameter of pins in inches; 

 jS = spacing of pins in feet; 

 h = height of flashboard in feet. 



