Concrete Cracking at External Corner
Concrete Cracking at External Corner
(OP)
I'm designing a circular cast-in-place reinf. concrete structure. Special steel doors are required
for safety reasons. The steel door attachment to concrete details must be followed exactly with embed plate as shown in attached detail. A concrete anchor is required near the outside corner as shown exacerbating the problem.
All dimensions in mm.
My concern is the concrete will crack where shown on attached sketch.
My plan is to "build-out" the concrete at the corner and add stirrup-like rebar (shown in blue on sketch) to reinforce the build-out and integrate it into the main structure.
I'm not a concrete detailing person since most of my experience is with steel structures.
Question: Does anyone see anything wrong with this approach? Is this build-out not necessary? Do you
know of a better approach?
Your feedback is appreciated.
for safety reasons. The steel door attachment to concrete details must be followed exactly with embed plate as shown in attached detail. A concrete anchor is required near the outside corner as shown exacerbating the problem.
All dimensions in mm.
My concern is the concrete will crack where shown on attached sketch.
My plan is to "build-out" the concrete at the corner and add stirrup-like rebar (shown in blue on sketch) to reinforce the build-out and integrate it into the main structure.
I'm not a concrete detailing person since most of my experience is with steel structures.
Question: Does anyone see anything wrong with this approach? Is this build-out not necessary? Do you
know of a better approach?
Your feedback is appreciated.






RE: Concrete Cracking at External Corner
Probably the more compelling reason to add the extension is difficulty in getting good concrete placement in the corner and probably less so for the spalling off at the plate. With that said I think your proposed configuration is reasonable but if you are implying a reinforcing "U" into the extension it might be a bit difficult to build with the wall at just 150mm. You might consider just a horizontal hooked bar with the tail oriented parallel to the door jamb and maybe a vertical jamb bar.
regards,
Michel
RE: Concrete Cracking at External Corner
RE: Concrete Cracking at External Corner
RE: Concrete Cracking at External Corner
I think that some neatly trimmed WWR extending into to the corners of the form might go a long way to reinforcing the brittle corners. If you can thicken the edge as shown that can only help I think.
RE: Concrete Cracking at External Corner
RE: Concrete Cracking at External Corner
RE: Concrete Cracking at External Corner
As far as cracking where you have it shown, the most likely culprit would be shrinkage of the concrete around the plate, if the anchorage is sufficient. I would never recommend relying upon the concrete bearing along the edge of a thin plate like this for shear resistance. If you expect much shear across the axis of the stud, you might want lugs on the back of the embedded plate to transfer the forces. But I don't imagine the loads are high enough to require much shear resistance.
I'm not sure what the smaller post-installed anchor near the top edge is doing.
RE: Concrete Cracking at External Corner
As one who has been in concrete construction for far too long, I would suggest extending your embedded plate to the corner and NOT do the concrete extension.
It is a troublesome forming condition that may never get built correctly, or, if it is built correctly, it may not stay that way when the concrete is placed.
JMHO
Ralph
Structures Consulting
Northeast USA
RE: Concrete Cracking at External Corner
The concrete anchors are specified by the door manufacturer. This is one of a limited number of approved doors for the specific protective requirements.
The door has been tested and must be installed under these specific and precise anchorage requirements. I'll also send the concrete details to the door manufacturer to see if they can concur this is consistent with their tested conditions.
Thanks to all, once again.