LOCK GATES AND VALVES. 



177 



Water Pressure. Horizontal Framing. Let P (Fig. 8) be the pressure per lineal 

 foot on any beam K of a horizontally 

 framed lock gate AB, H the head of 

 water to the center of K, and w its 

 height in feet. If the beam supports 

 sheathing, w must of course include the 

 total depth of water pressure supported 

 by the beam, and if there be water 

 below, H will be the net head. 



Then P equals 



wXi'XHx62% Ibs. 



Ibs. 



per lineal foot. The bending moment 



M, if there are no concentrated loads from valves, etc., will be 



FIG. 8. 



P X (ABY 

 8 



X 12 inch-pounds = 



3 wH X 62% Ibs. X (AB) 2 



The section required for this bending can then be found by the usual formulas 

 M and / = , where 5 = the extreme fiber stress per square inch, c = distance 



C 12 



from neutral axis to extreme fiber, t = thickness of beam, / = the moment of inertia 

 of section, and M and w are as just stated. 



Where K has to support concentrated loads from valves, we have a combination 

 of distributed and concentrated loads, which may be calculated as follows : 



-6 * e- * b- 



:r 



Valve 



Valve 



I 



FIG. 9. 



Let CD (Figs. 9 and 10) be a beam supporting two valves which produce loads on 

 CD at their points of support, each equal to Q. The beam has then to carry the valve 

 loads, the proportion of water pressure on the lengths a and c between the valves, 

 and the proportion of uniform load from the water pressure in the panel ECD above. 





