Connection Problem

[dik]

I have a connection issue with attaching a plate to a 4" thick precast panel. The load is approx 7K shared by two fasteners. I'm planning to use the following. Can anyone see any issues with this? I can vary any of the values. Concrete tensile strength is about 100 psi; I assume the precast is in excess of 4ksi.\

 

[jhnblgr]

How is t=4 but l=8
Also isn’t there equations for groups of anchors which are reduced?
What’s the application and can it be through bolted? Has the precast been made already or can they cast inserts into the concrete?

 

[dik]

It's fabricated and installed. I design connections for metal fabricators, and this is one of my recent issues. Any concerns about the methodology? I've already reduced the angle to 30deg...

 

[PMR06]

Are you bolting into the edge of a 4" thick panel, i.e. the 4" thickness is in and out of your view there, and thats how you can get 8" embed?

If so, it doesn't pass the initial gut check and I would want to see one of the bolt manufacturers design tools show this works (Hilti, Simpson, etc).

 

[dik]

Are you bolting into the edge of a 4" thick panel, i.e. the 4" thickness is in and out of your view there, and thats how you can get 8" embed?

Correct... concrete cover to the insert is 2" top and bottom. The steel plate is 3" deep (1/2" chamfer on the precast) with the line of fasteners in the middle, and the tensile force is from a guard post welded to the plate. It will be up to the precaster to confirm the slab edge can accommodate the moment.

 

[ANE91]

I understand that you’re primarily concerned with the connection itself and not the substrate. However, 2 inches of edge distance for 8 inches of embedment is hamstringing the capacity of the anchorage. The connection doesn’t work if the concrete simply explodes at the edges. Edges should be at least 1.5*embedment away. I understand that you can vary the embedment as well as other parameters.

Agree that this needs a bit of pencil sharpening.

 

[Brad805]

What are the anchors? Hilti, HCA, Simpson? Hilti limits the bolt size to 3/8" for a this type of embedment, so two bolts would be trickey. Hilti Profis works well for this.

 

[dik]

Thanks...

I was planning to use Hilti HAS E-55 type of anchorage except using ASTM F1554 and Grade 55 S1 threaded rod. Why limit to 3/8"? BAR 1/2" easily fits within 4" thick. I'm relying on the epoxy to 'glue' the threaded rod to the concrete and the concrete mass to hold together the block to pull away from the concrete mass. I've looked into the rod not being pulled out by failure of either the epoxy or the concrete.

 

[dik]

However, 2 inches of edge distance for 8 inches of embedment

I'm looking at the trapezoidal block of concrete to resist the load with the epoxy securing the threaded rod.

 

[ANE91]

I'm looking at the trapezoidal block of concrete to resist the load with the epoxy securing the threaded rod.

Yep. Sound in principle, and it’s done this way all the time. Just be careful with the geometry. I gathered from your comments that, in 3D-space, there is a concrete edge that is way too close to the anchor. I could easily have misunderstood.

 

[dik]

that is way too close to the anchor. I could easily have misunderstood.

The total slab thickness is 4". I didn't cause the problem... It's the proximity of the top and the bottom of the slab that's the problem. I'd normally just 'punch' this out on my calculator. There were enough variables and uncertainties that I did a little SMath program so I could change the parameters, quickly. I was presented with the problem; I usually get one or two of these each month. I'd originally looked at using 1-1/2" to the top and 2-1/2" to the bottom. In Canada, for guards, we can use 1/2 the guard forces for loads 'inwards' so I tried to minimise the force. I thought better about it and felt it best to have more concrete cover and deal with the larger force.

 

[ANE91]

When space is tight like this, I look to PDFs. Little buggers can carry a ton of weight.

If you’re dead-set on the anchor approach, then I recommend giving Hilti a call. They can point you to a low-embedment option that relieves your edge-distance problem. It’s either that or come up with a new configuration.

 

[dik]

I look to PDFs.

??? My original approach was to use a plate top and bottom with a through bolt. I decided to look at it a little more closely to see if I could get the proposed detail to work.

I get a few odd connections... I like them; they make up for the boring stuff I do.

 

[ANE91]

https://productdata.hilti.com/APQ_HC_RAW/ASSET_DOC_LOC_1577746.pdf

 

[dik]

https://productdata.hilti.com/APQ_HC_RAW/ASSET_DOC_LOC_1577746.pdf

Powder actuated fasteners... Thanks

 

[ANE91]

Or, more broadly, power driven fasteners. These days, some are gas actuated or battery actuated instead of powder.

 

[XR250]

Can this panel even take 7k regardless of the connection?
I can't imagine using PAF's (PDF's) for a connection like this. Might want to have many extra holes in your plate for the ones that don't embed fully.
I would be looking at thru bolts.