Reinf. for circular openings in thick conc. walls. 2

[TRBPA]

For the principal spillway of a lake, I have a concrete riser structure (8'x32' inside dims)designed using the PCA Concrete Tanks Method. I need to place a slide gate in the lower portion of the base wall that will have a 48 inch dia. thimble cast in place with the wall pour. Wall thickness is 53 inches, and steel is basic vertical/horizontal in both faces of wall, proportioned for flexure, actually min. steel controlled due to large section area. Since the verical/horizontal bars will be stopped 3" short around the periphery of the thimble, are there any considerations I need to make such as diagonal bars at what would otherwise be four corners of the opening. If so, what criteria should be followed. Didn't find anything relative in ACI 318. Thanks in advance for any advice.

 

[twinnell]

Typically, you should add horizontal bars and vertical bars on each side and top and bottom of the opening. The quantity of bars should equal the number of bars that are disrupted. If the opening distrupts 6 bars vertical and 4 bars horizontal; place 3 additional bars on each side of the opening and 2 additional bars top and bottom. Also, add two diagonal bars at each corner of the opening. Extend all bars the full development length of the bar past each opening face. If you can't achieve full development length, terminate the bar in the adacent wall with a hook.

 

[miecz]

See thread507-170996.

 

[TRBPA]

Thanks guys, hit the nail on the head. I breezed over 13.4.2 too quickly.