THE IMPROVEMENT OF RIVERS. 



nek and a cover-plate, so that only the maximum bending moment, which occurs in 

 CD, need be found. One-fourth may be deducted from this moment, as AD acts as a 

 continuous beam, and the result used in the formula below. 

 The total area of section required will then be 



where A -total area required; S = total allowed strain per square inch; d amount 



PI _ A 



of direct compression or tension in the member; M = maximum bending moment in 

 inch-pounds; ;= distance in inches of extreme fiber from neutral axis; r = radius of 

 gyration of the section. 



The gates or curtains themselves have to sustain the pressure of the water, which 



equals for any gate 



lbs. =P, 



where w = horizontal length of gate, & = its height, and d = distance from surface of 

 water to center of gate, all in feet. 



P X iv SI 



The bending moment is g X 12 inch-pounds = M , and M = -^, where 5 = extreme 



fiber stress per square inch, C = half the thickness of the gate, and 7 = its moment of 

 inertia. 



DIMENSIONS OF TRESTLES FOR GATE AND CURTAIN DAMS. 



