i8o 



THE IMPROVEMENT OF RIVERS. 



surface, w the width of water supported by the beam, /?, and R t the reactions as shown. 



Then the pressure P - wH 62} Ibs. - - X 62 J Ibs. 



Taking moments about the base we find 



PH wH* X 62$ Ibs. 



3 (// + d) 6 (// + d) 



The bending moment at any point distant x from the surface is 



* x) II* (d + x) -x n (H + d) 



R t (d + x) - w*.-.62j--j X 12 a> X 62* - 6 (H + -'Xi2in.-lbs 



The section required may be determined by the formulas given on page 177. 



Strain on Anchor- bars, Diagonals, etc. The anchor-bars should always be propor- 

 tioned to carry the weight of the leaf when swinging in air, and in the case of small 

 gates an increase should be provided in the section found necessary as a precaution 



" -T 



T - " 





. 



FIG. u. 



> -w 



Fio. 13. 



against blows from craft. The use of rollers to support the toe of the gate, with the 

 object of relieving the pull on the anchors, has been discarded, since any deposit over 

 the track interferes with the wheels, and when they are a little worn their support becomes 

 practically valueless. 



If W (Fig. 13) represents the weight of a leaf swinging free, the pull on the anchor- 



W X FE 

 bars, taking moments about E, is P = -^p 



W X BD 

 The thrust R on the pintle E, taking moments about B, is R = ^u 



W BG 

 The strain on the diagonal BG is X -TT" 



With a diagonal on each side of the gate the load on each will of course be one-half 

 of this. 



