Concrete Crib Wall Repair

[ntstr]

I am working on a project that contains an open faced precast concrete crib wall that is need of repair. It is approximately 20 feet tall and was built about 30 years ago. The wall is backfilled with stone approximately 4 to 5 inches in size. The majority of the wall appears to be in good shape, however there are several precast members that have been damaged (possibly due to impact loads during floods?) that need to be repaired. I have attached photos of the wall and some of the damaged areas.

I have thought of replacing the end of the damaged headers with a new end cap set in place with drilled and epoxied concrete anchors. Would it be possible to replace the damaged stretchers with new members that span between the stretchers in good shape above and below the damaged stretchers?

Has anyone seen any crib walls with damages similar to this? Any suggestions on repair methods?

Thanks!

 

[bridgebuster]

I'm curious why the stretchers broke. what size are the wires? I haven't done much with crib walls but never seen any with less than No. 3 bars. If you're going to fix the caps why bother with epoxy anchors? Perhaps just anchor in some 3/8" diameter hook bars.

Is the wall stable? If so I wouldn't touch the stretchers. If there's a concern that the stone will fall out just put a rock fence over it.

 

[racookpe1978]

the verticals are under significant outward forces, and all (in this section) have successively failed. So, there's no reistance vertically = you have to restore that much original strength + additional area to resist the existing fores (because it did fail -> the old wall was understrength) PLUS some margin against future failure.

Seems to me that you could use a strengthened steel "form" to do three things:

(1) the steel ( the"u-shaped" form) would retain the wet concrete until it hardened,
(2) a u-form could be held onto the existing trashed old concrete by grouted or epoxied bolts to hold up the u-form and pull the old concrete and the new concrete together. You still need rebar inside the u-form, but not as many.
(3) a 3/8 thick or 1/4 thick u-shaped form that is not removed but left in place held on the epoxied bolts would increase the tension resistance of the new verticals.

 

[ntstr]

bridgebuster, the wall is stable. The reinforcing in the stretchers are #3 bars. If 3/8" diameter hook bars are anchored in would you have to drill in to the stretcher the full lap splice length of a #3 bar which would be about 18.5"?

 

[bridgebuster]

For repairs to concrete we use 3/8" diameter hooked bars inserted in anchors embedded to concrete. The attached file provides information on the anchors.

 

[dhengr]

Ntstr:
Expansion bolts could give you trouble on those thin (small cross section) members (headers?), in fact impact drilling might, on that old concrete. I think I would drill and epoxy any new anchor bolts in place, and test that to see that it works well. It would be helpful if you posted a couple sketches of the headers and stretchers, with dimensions, reinforcing, etc. so we could really see exactly what you are dealing with. It would also be of value to do a little testing to see if the rock backfill will pretty much stay in place when you remove a couple stretchers, or maybe only one at a time. Maybe you can consolidate the rock backfill a bit with a vibrating pneumatic compactor/tamper. The kind I am thinking of is 4-5" in dia. and 3' long at the body, and has a 4" dia. tamping foot, almost like a jack hammer in action. You will also have to come up with some clever jacking and wedging means or equipment to lift one level of headers, 2, 3 or 4 adjacent headers at a time so you can work on or insert new stretchers. That’ll take some testing too, what lifting forces req’rd. and how much movement (looks like it has to be 4-6" vert.) at each header/stretcher joint. The stretchers would be precast a few inches long and cut to length in the field. What to do with the heads of the headers, that’s a head scratcher. Does that make sense? Could you make a .5-.75" thk. x 6" sq. steel washer, drilled for an A.B. into the end of the header, and used as a drilling template. Set the A.B., apply some grout/mason’s mud to the end of the header, and apply the washer to squeeze out a little grout. Cover the washer with a precast conc. head piece (pretty fragile?), back side void to fit the washer and the A.B., sloped to drain on the bot. edge and epoxied to the stl. washer.