Fibermesh - Tension Capacity

[tjacorn]

Ok, I have an odd situation where I'm putting 6" by 6" steel bollards at 1' o.c. in a concrete trench (1'-4" wide by 4' to 6' deep). The bollards are rotated 45 degrees so they are diamond shape in plan.

I'm worried that a crack will occur between the bollards, propagate down into the foundation and compromise the integrity of the fence over time. The only reinforcing in the fence will be wire mesh at full depth on each face of the trench running longitudinally the length of the trench. There is presently nothing called out to tie the two faces together.

I proposed that a #3 rebar be added between bollards to tie each face together and keep the crack from occurring or spreading. The bar would tie to two #4's, one on each face of the trench running the length of the fence.

And this proposal has caused much pain and suffering. I'm now looking at every possible alternative.

One thought (not mine) was to replace the #3 with fibermesh in the concrete. I've only heard of fibermesh being used in slabs. To research this I need to know what the tension capacity is of the mesh to see if it is sufficient to replace the #3. My gut says it won't work but I need to look into it. Any thoughts?

 

[civilperson]

The bollard itself will connect the two faces if the mesh is attached to the bollard corner.

 

[tjacorn]

The mesh will not be attached to the bollard. It will only be tackwelded every 8' or so.

 

[druminman]

Structural fibers may be able to provide enough tensile capacity. Contact Fibermesh or another supplier and talk to their engineers. We saw a presentation in the office recently from Fibermesh. They have plastic fibers now that are capable of developing enough tensile capacity to be used structurally, even to replace shear reinforcement.

This will require careful mix proportioning to preserve workability, though, and may exceed the cost of placing the transverse bars.

Traditional fibrilated poly fibers will not prevent structural cracking.