Retaining wall bracing
Retaining wall bracing
(OP)
Hi, I'm a rookie structural engineer, and I'd really like some feedback on my shoring design.
There's a 19' high stone retaining wall next to a building that someone planted a tree on top of. The roots are now pushing through the wall and causing a 40' section to begin to topple. To prevent this, I'm designing a frame to brace the wall against the building while it's removed/repaired.
My structure consists of W-shape columns up against the wall every 5 feet (9 in total) With two W-beams connecting the columns horizontally (welded). There are 3 sets of 2 compression members at 45 degree angles (also W shaped) that connect the columns to the facade.
See the attached PDF for pictures.
I'm currently designing the members
I calculated the vertical effective pressure triangle for the soil behind the wall (120 PCF and friction angle = 30 degrees) and found that the resultant occurred 6'4" from the base of the wall at a magnitude of 7.2 kips/LF.
I assume I should treat the horizontal braces as compression members and the diagonal braces as tension members. The columns would actually be more like loaded beams with one fixed end, and the horizontal W beams would also be treated like a beam with opposing point loads creating bending moments. Is this how I should approach the design process, or am I not on the right track?
Also, what is the best way to resolve the lateral earth pressure?
Should I weld a plate to the spot where the braces are joined to cut down on punching shear? I'm not sure how much load the brick building facade can withstand.
Any help or advice would be greatly appreciated
There's a 19' high stone retaining wall next to a building that someone planted a tree on top of. The roots are now pushing through the wall and causing a 40' section to begin to topple. To prevent this, I'm designing a frame to brace the wall against the building while it's removed/repaired.
My structure consists of W-shape columns up against the wall every 5 feet (9 in total) With two W-beams connecting the columns horizontally (welded). There are 3 sets of 2 compression members at 45 degree angles (also W shaped) that connect the columns to the facade.
See the attached PDF for pictures.
I'm currently designing the members
I calculated the vertical effective pressure triangle for the soil behind the wall (120 PCF and friction angle = 30 degrees) and found that the resultant occurred 6'4" from the base of the wall at a magnitude of 7.2 kips/LF.
I assume I should treat the horizontal braces as compression members and the diagonal braces as tension members. The columns would actually be more like loaded beams with one fixed end, and the horizontal W beams would also be treated like a beam with opposing point loads creating bending moments. Is this how I should approach the design process, or am I not on the right track?
Also, what is the best way to resolve the lateral earth pressure?
Should I weld a plate to the spot where the braces are joined to cut down on punching shear? I'm not sure how much load the brick building facade can withstand.
Any help or advice would be greatly appreciated






RE: Retaining wall bracing
Also, your bracing system appears to be statically unstable where the diagonal brace meets the horizontal beam at the top of your sketch.
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RE: Retaining wall bracing
@Larsacious & dcarr82775: The bracing is to support the wall while it is being repaired. There are 9 piles with concrete footings that support the wall, and those are braces up against the building with 6 braces in 3 locations.
@IceNine & hokie66: I agree with you, I'm seriously considering starting from scratch (my boss gave me the concept, so I don't know how many liberties I can take with the design).
@shobroco: I'm fairly sure the wall has anchors, but they've rusted out and failed in several places, so I've assumed a worst case scenario. As far as I can tell, the reason this particular section is failing is because of a very large tree (which has recently been cut down) right up against the edge of the wall. The tree roots are poking through the stone in several places
Anyway, I'm going to do a complete redesign, and I'll post that once I'm done. I appreciate all the advice!
RE: Retaining wall bracing
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Retaining wall bracing
I doubt the tree is the cause of failure.
I advise do NOT brace with existing building.
I didn't see pictures, are there actual photos?
What is above the wall. There is a new method of stabilization, a variation on soil nailing where a track-hoe fires a large nail on a pattern, I would consider this.
I dont think you will be able to repair wall as proposed. Cant you take it down and rebuild properly?
In all cases make sure a geotech provides appropriate design lateral pressure and considers global stability.
Could you build a new wall in front of it? Maybe soldier piles in drilled shafts and tie backs above and precast facing elements with a clean drainable backfill between old and new walls.
Good luck