Hooking through a embedded hole 2

[WARose]

I have embedded angle with a backing plate that has a hole in it that I am going to anchor by hooking a rebar [180 hook] through the hole and developing it in reinforced concrete. Only thing that worries me is the hook. Should it be tied differently? It's not hooking around other (developed) rebar. THanks.

 

[KootK]

I'm fairly certain that I've gotten this wrong but, hopefully, your explanation of how wrong will allow me to get it right with the next pass.

 

[WARose]

Doesn't look too bad to me Kootk. It's close to my situation and it appears you are saying for it to go through the hole a few times. Good idea, but I don't have enough hole diameter for that.

Maybe have the length of the hook be long enough to fully develop on the other side of the extension? (I.e. instead of a 10d_b hook length.......just go with l_d.)

Developed on both sides of the hole.....I wouldn't think it could pop out at that point. (Outside of shear failure in the rebar or some edge condition.)

EDIT: Like a hairpin.

[red]2nd edit[/red]: should have thought of that before hand. Sorry if I wasted your time kootk. I'm trying to do too much these days.

 

[dhengr]

WARose:
I’d worry that the angle and its backing pl. would have to move 1/8” before they really engaged the hooked rebar in the region of the hook. I’d weld the rebar to the backing pl.

 

[StrucDesignPE]

Agree with dhengr, why not just weld a deformed bar or two onto the angle?

 

[KootK]

It's close to my situation and it appears you are saying for it to go through the hole a few times.

I wasn't pitching multiple loops through (constructability). I was just trying to convey the 180 hook and was too lazy to show it properly.

Developed on both sides of the hole....

Yup, I like that much better. I share dhengr's concern about slip though, both from engagement of the hole and straitening out the bend en route to developing the full capacity. I think that you'd daylight the angle a bit prior to developing the capacity. Whether or not that's a problem will depend on your situation. If this thing has real serviceability loads, I'd go with a welded DBA or studs. On the other hand, if this is a connection of extreme last resort, I'd be willing to let it ride. There is precedent in the world of precast lifting for doing pretty much the same thing and I've not had issues with it in the past. I know that TheMightyEngineer has some expertise in this area. Perhaps he will chime in.

Sorry if I wasted your time kootk.

No worries. When your world's on fire, sometimes you just need a little bounce from the guy in the digi-cube next door to keep things humming along. Been there / am there.

 

[bones206]

I'm also in favor of welding. The placement of fluid concrete dislodging the bar slightly makes it hard to guarantee the hook is engaged tight on the edge of the hole. But hypothetically if you could detail such that engagement is guaranteed, I don't necessarily see any slippage problems. It could probably be accomplished with a few wire ties in the right places.

You definitely want a hairpin with both legs developed instead of a hook.

 

[WARose]

No worries. When your world's on fire, sometimes you just need a little bounce from the guy in the digi-cube next door to keep things humming along. Been there / am there.

 

[BridgeSmith]

For embedded angles like that, we typically just use automatically end-welded studs, alternating horizontal and vertical.

 

[TLHS]

For nominal loads I normally do this (photo from random google image search results)

https://branchironworks.com/site/wp-content/gallery/C:-Embedded-Items/CEmbedded-Angle-wStuds.jpg

For significant loads, I'd start to worry about the capacity of the weld on the bend. Realistically, though, the stud's weld capacity isn't what's going to govern in these sorts of situations.

 

[WARose]

Guys, can't do studs. It's a cast iron frame and the warranty is void if i weld, cut, put holes in, or do anything to it. I appreciate the suggestions though.

Movement is a concern....but embedded anchors move when engaged as well. (Especially as they approach their ultimate capacity.)

In reality, I think friction will do the job before that hairpin (or whatever) gets engaged.

 

[BridgeSmith]

If you're concerned with movement before engagement, you could call for a wedge or shim to be installed in the hole after the bar is in place, to hold it tight against the edge of the hole.

 

[WARose]

good idea HotRod

 

[TLHS]

I feel like there should be a way to run a bolt through the hole and have the bolt attached to a strand or rebar or something. They you'd likely have less potential slip at the hole. I can't think of a good way to do it though that doesn't take an unreasonable amount of fabrication.

I agree that a hairpin or a hook with a shim (if possible) is likely the best you're going to get.

 

[bones206]

So what's wrong with using tie wire? That's how virtually all rebar is held in place anyways...

 

[BridgeSmith]

For better anchorage, you could put a threaded rod through the hole, with nuts tightened on either side of the plate, and then put a hairpin around the threaded rod on each side.

 

[TLHS]

HotRod, I had been thinking about that too, but unless you've got a really small hole and rod in relation to the size of your angle, I feel like that would cause problems with getting the concrete fully into the interior corner of the angle, past the threaded rod.

 

[TehMightyEngineer]

Can't resist a KootK summons!

I second the tie wire Bones mentioned; cheap, easy, and the rod-busters are familiar with it and will have it on hand. A couple of loops of wire will hold it hard against the correct edge of the hole. As KootK pointed out this is a fairly common thing with precast and tilt-up walls with embedded lifting anchors that require V-shaped rebar for tension or shear reinforcement. Just bold or underline the requirement that it be tied to bear directly against the hole so they can't miss it on the plans.

As KootK's anchor detail shows; I'd make the bar be V-shaped with symmetrical legs. Doubles your anchorage capacity and helps make it obvious what the intent is vs when they see a random hooked bar laying around while they wonder where that goes. Also, keep the bend tight on the V-shape. Use the bend radius of the standard stirrup hook radius, as I recall a wider radius of the standard 180° hooks can tend to straighten out a bit under load from the embedded plate.

From a practical standpoint, I've used many embeds with details similar to this on very narrow precast panels. The added rebar definitely works and will put the load much deeper into the concrete than just the appendix D calcs on the anchor alone would show.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)