Concrete wall hinge

[dakota99]

I am looking for some fresh ideas on how to approach this design.

I have a wall that spans from top of footing in the basement to the roof deck at wood truss bearing. Currently there is a hinge point at grade elevation 18’ from the top of footing since there will be no floor diaphragm in this location. (see sketch) We have looked at running a monolithic concrete wall to the roof diaphragm but the roof diaphragm is nowhere close to being strong enough. We also looked at making it a retaining wall with a big footing. However I would anticipate quite a bit of movement at the time of back filling and the waterproofing would probably tear apart at the corners.
Any thoughts on how to eliminate the hinge?

 

[OHIOMatt]

You could consider a grade beam (rotated 90 degrees from what you would typically see) that would span from wall to wall (could be placed under the exterior grade). The beam would need to be very stiff, but if placed on the outside face, you may not have any depth limitations.

 

[BAretired]

OHIOMatt's idea is good.

Alternatively, you could use tiebacks spaced along the wall, each tied to a deadman located outside the wall.

BA

 

[msquared48]

Depending on the property line and possible easement constraints, the tieback solution is your best bet here.

I agree that an 18 foot high retaining wall would be monstrous and very expensive.

Another solution, although kinda crazy, would be horizontal beams spaced up the wall to distribute the lateral load to the endwalls - kinda like walers - and they could be either concrete or steel encased in concrete.. This is of course expensive to form and will not be possible if the wall is too long.

I still like the tiebacks best.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[vandede427]

is this just a portion of a wall that doesn't have a floor, like a stair condition, or is the entire wall this way? you said no floor "in this location" so it makes me think that there is floor somewhere down the line from this section cut.

if that's the case then theorize a beam in the top of the concrete wall that spans that distance. make sure the header framing the opening can handle the axial load from this "beam's" reaction.

 

[BAretired]

vandede,

The second page of the attachment shows the wall in plan. The opening extends 36' along the wall.

BA

 

[vandede427]

ah yes, the second page.

36' is a pretty long span. I like the tieback/deadman suggestion from the others. Maybe 3 of them in the middle @ 9' o.c.

 

[jheidt2543]

Sorry this is late but:

Could vertical pilasters @ say 12' o.c. on the outside of the wall? They wouldn't take up near the room of tiebacks and would stiffen the wall considerably like a counterfort wall; then the top of the wall could be designed as a beam spanning 12' between counterforts?

Just a thought.

 

[larsacious]

I have run into a situation similar to this at a stair well condition. My recommendation would be to increase the wall thickness (say 20" to 24") and reinforce the top of the wall as a beam to span to the perpendicular walls.

I do not recommend the tieback solution since these tie backs are likely to experience corrosion or be damaged by any future excavation that could take place in the future.

Good luck!