Why Do We Need Corner Braces in Shoring Systems
Why Do We Need Corner Braces in Shoring Systems
(OP)
Local shoring contractors in my area always seem to use corner braces in conjunction with their tie-back shoring systems. Why are corner braces used instead of continuing the tie-backs right into the corner? Is it because the machine used for tie-back installation cannot get physically close to the corner? Are there systems available that do not require corner braces?
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.





RE: Why Do We Need Corner Braces in Shoring Systems
RE: Why Do We Need Corner Braces in Shoring Systems
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RE: Why Do We Need Corner Braces in Shoring Systems
RE: Why Do We Need Corner Braces in Shoring Systems
So, if one were willing to pay extra, is it possible to not have corner braces then? My current issue is that some corner braces need to be removed prior to the casting of a foundation wall and now the shoring engineer is asking me to assess my parkade diaphragm's ability to resist considerably more than a single story worth of earth pressure. Frankly, in retrospect, I surprised that this hasn't cropped up before.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Why Do We Need Corner Braces in Shoring Systems
Another consideration is that the walers should be long enough and welded enough to the sheeting wall to properly transfer the walers' axial loads to the soil behind the walls or to the waler and wall on the opposite side of the excavation. I have seen soldier beams and SSP push laterally along the wall because the walers were not long enough. The hard question to answer is, "How long is enough?"
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RE: Why Do We Need Corner Braces in Shoring Systems
If you need to have walers with your braces, then the sheeting needs to be offset from the proposed wall by about 3 to 4 feet to allow room for the waler, wall forms, waterproofing, and backfill. If the concrete wall needs to be poured directly against the sheeting wall, an alternative, SOMETIMES, is place the braced walers above the top of the proposed wall, if possible.
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RE: Why Do We Need Corner Braces in Shoring Systems
This is essentially placing the whalers on the exterior side of the foundation wall, right? Wouldn't that mean that, in plan, the shoring would look like a castle with "turrets" offset out at the corners? I'm having a hard time imagining that a contractor could be persuaded to do that.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Why Do We Need Corner Braces in Shoring Systems
www.PeirceEngineering.com
RE: Why Do We Need Corner Braces in Shoring Systems
www.PeirceEngineering.com
RE: Why Do We Need Corner Braces in Shoring Systems
Your initial sketch seems to indicate a secant pile wall with anchors. This type wall does not typically require walers.
RE: Why Do We Need Corner Braces in Shoring Systems
www.PeirceEngineering.com
RE: Why Do We Need Corner Braces in Shoring Systems
www.PeirceEngineering.com
RE: Why Do We Need Corner Braces in Shoring Systems
All the secant pile walls I have seen (and/or designed) have a waler unless lateral support is only provided at capping beam level.
RE: Why Do We Need Corner Braces in Shoring Systems
RE: Why Do We Need Corner Braces in Shoring Systems
I agree. I had not noticed there was an anchor every hard pile. I am used to seeing an anchor every third soft pile with a waler.
RE: Why Do We Need Corner Braces in Shoring Systems
RE: Why Do We Need Corner Braces in Shoring Systems
See the sketch below. It probably makes no sense. It was just my shot in the dark at trying to sort out this statement:
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Why Do We Need Corner Braces in Shoring Systems
RE: Why Do We Need Corner Braces in Shoring Systems
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Why Do We Need Corner Braces in Shoring Systems
useeliminate the corner braces if you install corner ties as shown on my sketch. If the drilled shafts are wide enough, you may be able to fit the tieback drill and drill the two tiebacks that are immediately next to the corner.www.PeirceEngineering.com
RE: Why Do We Need Corner Braces in Shoring Systems
Agreed but not my call.
Perhaps. It seems to me that the drilled shaft in the very corner should not need a tie back. It ought to be able to lean on the adjacent drilled shaft walls as shear walls/diaphragms.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Why Do We Need Corner Braces in Shoring Systems
www.PeirceEngineering.com
RE: Why Do We Need Corner Braces in Shoring Systems
Why not? With the scheme that I've crudely shown below, the corner pile should be every bit as restrained as a column with a tie-back. More so really.
I do realize that you're rather good a this. I simply want to understand the parts of this that are still confusing me.
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I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Why Do We Need Corner Braces in Shoring Systems
I would not trust three, adjacent, drilled shafts in a corner without tiebacks or a braced waler.
The crawler track width of a tieback drill could easily be 8 feet, therefore, maybe 4 feet on either side of the tieback being drilled off the end of the drill. However, many drills can also drill off to the side at up to 90 degrees from the end of the drill. Usually, the 90 degrees is to the left side of the drill. Therefore, in a rectangular sheeted excavation, two opposite corner tiebacks may be able to be drilled while the other two opposite tiebacks may have insufficient room for the drill mast and operator's controls. If you can keep the tiebacks a few feet from the corner or a perpendicular wall, the drilling may be easier.
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RE: Why Do We Need Corner Braces in Shoring Systems
1. Corner braces are much easier and cheaper to install that tiebacks.
2. There is also an equipment constraint, which will depend on the size of the rig. That is, the rig is unlikely to drill very close perpendicular to the corner walls.
3. I think the need for corner bracing is dependent on the loading and structural stiffness. If the corner is stiff enough for the given loading, I do not see the need for bracing. In the case of the secant wall, the corners will be more rigid than the other sections of the wall. In the case of sheet pile which while be essentially a pin connection, the walers will need to have a moment connection at the corner, or a brace will be required to maintain the stiffness. If no bracing, a heavier section is likely required for the waler using moment connection. For the typical excavation support system, I do not see design of moment connection a viable alternative.
RE: Why Do We Need Corner Braces in Shoring Systems
Second of all, in corners, it is harder to anchor. Also, "corner braces" are always better, since they simply cannot deform, we are certain that walls will not deflect. (They may break though, due to high shear, so check your reinforcements carefully.)
I have seen some of the contractors do not like the corner braces. This is due to mainly they do not have skilled welders. With a two good skilled welders and a crane, it is easiest job.
Considerations:
*Buckling of corner brace.
*Self weight deflection of brace.
*Capacity of welds should be greater than the shear that will carry. Take the weld thickness at most 1cm. If this is not enough you have to extend its ends with a bigger pipe to increase the weld area.
*Pile reinforcement.
*Capacity of small anchors that will hold the plate (that braces will push on) on the wall.
RE: Why Do We Need Corner Braces in Shoring Systems
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