Damaged Large Pipe Column Repair
Damaged Large Pipe Column Repair
(OP)
I've got a large pipe column supporting a sign structure that was hit by a large vehicle (Semi Tractor) and damaged. Pipe is 36" dia x 0.375" wall thickness. Photos linked below.
The column is cantilevered from a block foundation using lateral bearing to resist lateral loads. Axial loads are minimal relative to bending. My first instinct was to provide a wrap/doubler plate over the damaged area. The 'dent' is pretty well aligned with the sign face so that it's in the area of maximum bending stress. I'm in the midst of figuring out how to get the stresses transferred into and back out of the plate. But before I get too deep with that, I was wondering if any of you might have any bright ideas for repair that I'm missing. Or issues I'm not considering with this approach.
I'm thinking that I'll need to extend the wrap above and below the damaged area enough that I can provide a series of plug/slot welds to achieve the required stress transfer. I'm not really comfortable with a big fillet weld across the top and bottom and brief numbers show the sizing wouldn't be practical anyway.
One of my concerns is that the section isn't simply dented, but overly deformed where a nicely rolled plate wouldn't fit over the dented area. I wonder if a series of adjacent channels spanning the dent would be more practical. At least with those the flanges could be trimmed to fit over any deformations...and then I could use all fillet welds. Hmmmm...
Foundation damage is going to require the removal and replacement of some concrete below grade.
http://files.engineering.com/getfile.aspx?folder=c...
http://files.engineering.com/getfile.aspx?folder=8...
Thoughts are appreciated.
The column is cantilevered from a block foundation using lateral bearing to resist lateral loads. Axial loads are minimal relative to bending. My first instinct was to provide a wrap/doubler plate over the damaged area. The 'dent' is pretty well aligned with the sign face so that it's in the area of maximum bending stress. I'm in the midst of figuring out how to get the stresses transferred into and back out of the plate. But before I get too deep with that, I was wondering if any of you might have any bright ideas for repair that I'm missing. Or issues I'm not considering with this approach.
I'm thinking that I'll need to extend the wrap above and below the damaged area enough that I can provide a series of plug/slot welds to achieve the required stress transfer. I'm not really comfortable with a big fillet weld across the top and bottom and brief numbers show the sizing wouldn't be practical anyway.
One of my concerns is that the section isn't simply dented, but overly deformed where a nicely rolled plate wouldn't fit over the dented area. I wonder if a series of adjacent channels spanning the dent would be more practical. At least with those the flanges could be trimmed to fit over any deformations...and then I could use all fillet welds. Hmmmm...
Foundation damage is going to require the removal and replacement of some concrete below grade.
http://files.engineering.com/getfile.aspx?folder=c...
http://files.engineering.com/getfile.aspx?folder=8...
Thoughts are appreciated.






RE: Damaged Large Pipe Column Repair
The new shell could be curved to the appropriate radius and would act in conjunction with the vertical plates and dented shell for a strong composite section.
BA
RE: Damaged Large Pipe Column Repair
RE: Damaged Large Pipe Column Repair
You still might be able to weld a curved plate to the outside after that, and/or frp wrap as mentioned too.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Damaged Large Pipe Column Repair
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Damaged Large Pipe Column Repair
Difficult to do. You need to "push in" at the points where the column is "bulged out" from nominal, and (somehow simultaneously) "pull-out" where the steel is bulged in from nominal. The steel now is "popped" inside nominal across one part of the arc, and bulged out at both ends of that arc. Once it is "rounded" inside nominal all the way across the dented area, then you can weld a new rounded (rolled) plate over the "bulged in" areas.
I don't think a chainfall wrapped around the column - no matter how cleverly applied - will work unless you can "focus" the net pressure on the specific area bulging, without further kinking the good parts..
What material? Painted carbon steel or aluminum? Galvanized?
Can you get into the inside of the column - even if that might be difficult?
I've got some ideas, but they might be unorthodox.
RE: Damaged Large Pipe Column Repair
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Damaged Large Pipe Column Repair
But, if the existing steel can be bent back into a shape where a properly rolled cover plate can be fitted over the dent, then welded all-around to the existing column, then you would not have to remove the dent. Its strength is replaced with the good plate now carrying the load.
my question was finding ways to straighten the column where "dented out" so as to allow the replacement cover plate to be fitted around the column. Hence, my question about material and my question about access into the center of the column. Both are intended to find ways of "moving" the crimped (popped out) corners of the dent.
As-is, if you can't straighten that dent, then you must cut out the bad steel and weld on the replacement cover plate - but carry the load for the sign while the guts of the sign's column are cut out and being welded.
RE: Damaged Large Pipe Column Repair
It is a steel pipe with no current or simple access inside. And at 36" dia, I'm not sure how practical it would be to work inside. The sign is in a rural area so I don't believe attempting a repair that's not a sure thing is a good idea.
The top of the structure could be fairly easily removed (bolts) if we decide to go with the removal (of the damaged section) and replacement route. But expense on that might be excessive with CJP welding and required inspection/testing. Plus a more significant crane that might not otherwise be needed.
Any thoughts on using T sections and nibbling/shaping the web to match the contour of the damage? Could weld stiffeners between the pipe/web/flange if required for flange bracing. Sort of a hybrid approach of BA's and ra's ideas.
Thanks again.
RE: Damaged Large Pipe Column Repair
If buckling of the pipe is a concern, drill holes thru the wall and pump in self-consolidating concrete to above the height of the damage.
Check the footing for the added weight of the concrete... if overturning moment controlled the size of the footing, the added dead load may not be an issue.
Good luck,
Brandon Rossetti
Rossetti Engineering, PLLC
http://www.rossetticonsulting.com
RE: Damaged Large Pipe Column Repair
Sketch of an idea that might work coming coming tomorrow.
RE: Damaged Large Pipe Column Repair
E.g. collapse pressure would not exceed 78 psid for a perfect tube, and 51 psi for one that was out of round by 10mm, assuming syp=36ksi and some other stuff.
I know it's not externally pressurized, but consider the possibility of pressurizing the interior in an attempt to de-dent the tube, at least partially. The sign may be tall enough that just filling the tube with water might be sufficient.
Mike Halloran
Pembroke Pines, FL, USA
RE: Damaged Large Pipe Column Repair
I also like the idea of filling the pipe with concrete to an elevation above the damage. Then, also cast a 6 or 8" thick concrete skirt all around the outside of the pipe, with a top sloped to drain. Tool a reglet all round the stl. pipe to be filled with caulking. Reinforce the skirt with vert. bars and with hoops just as you would a round conc. column.
RE: Damaged Large Pipe Column Repair
This will provide a four foot diameter pipe in the lower six or eight feet but who cares? Beauty is in the eye of the beholder and this would provide a solid resistance, a sort of bollard, to the next yahoo who drives into it.
BA
RE: Damaged Large Pipe Column Repair
RE: Damaged Large Pipe Column Repair
The strength member - the replacement steel - would first be rolled as a 36 inch diameter inside dia. Thickness would would 1/8 thick (or 1/4 inch) thicker than the current column steel. This would let a complete fillet weld be established all the way around the added belt.
Belt needs to be long enough to extend at least 3 to 6 inches longer than the dented area is tall.
belt should not be a complete circle, but, after rolling into a circle (or half circle) should be cut into 6 sextent parts. Leave approximately 1-1/2 to 2 inches between each segment for two vertical welds. A fillet weld around each segment provides vertical as well as horizontal support, and is easier to handle in the field and weld and build than a series of slot welds. The segments will cover up the 3x handholds.
the two handholds that cut out the kinks will allow the dent to move under the pressure of the internal threaded rod or hydraulic jack. Excess rolled steel plates inserted as stiffeners between the jack and column will prevent the threaded rod (or jack) from deforming the column steel at each end.
RE: Damaged Large Pipe Column Repair
Contact people that actually do this kind of work, and they can give you a good idea of what's practical for them.