Steel Inspector
Structural
After fabrication steel workers roll the pile cage which causes the longitudinal rebars to get twisted. ( Pic attached)
will this effect the pile load capacity?
will this effect the pile load capacity?
Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations JStephen on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
Pile longitudinal rebar twisted during fabrication
- Thread starter Steel Inspector
- Start date
mfgenggear
Aerospace
An sop has to be written, and a proper structural analysis. Job has to be stopped until your satisfied with the correct answers.
No simple answer.
- Thread starter
- #3
Steel Inspector
Structural
Any more responses?
what is happening is that longitudinal bars will form a minor helical shape instead of being straight
what is happening is that longitudinal bars will form a minor helical shape instead of being straight
Shirley you can't be serious
- Thread starter
- #5
mfgenggear
Aerospace
Ya explain show your numbers, how does this effect structual integrity. Your statement is ridiculous
- Thread starter
- #7
Steel Inspector
Structural
i read in a study that fabricating the main longitudinal bars in a spiral/helical shape actually increases the Load carrying capacity of the column ( ie , pile ).
From the fabricator's point of view, can this not simply be a matter of comparing the inclination of those longitudinal bars to max allowable tolerances? I don't know where this project is based, but I think we can all agree that there is some daylight between "perfect to the molecular level" and "interfering with the intended structural performance". The shut-it-down approach for something that can be measured and compared seems like an obvious first step.
There would be relevant tolerances for steel placement as part of the basis of design, which I assume counting upon straight bars. Find those tolerances, compare to them to what you can measure, and go from there. The cages can be rejected or accepted on this basis.
Now, if you're shopping responses in this forum to find a second opinion to come back at an engineer who is saying something you don't like, then look somewhere else. This is meant to come off as direct and not rude. I apologize if it seems rude, and I should have included this with my initial reply.
There would be relevant tolerances for steel placement as part of the basis of design, which I assume counting upon straight bars. Find those tolerances, compare to them to what you can measure, and go from there. The cages can be rejected or accepted on this basis.
Now, if you're shopping responses in this forum to find a second opinion to come back at an engineer who is saying something you don't like, then look somewhere else. This is meant to come off as direct and not rude. I apologize if it seems rude, and I should have included this with my initial reply.
mfgenggear
Aerospace
Question Was for blockhead, this is not my specialty. How ever free body diagram should be drawn. What is the design intent, is acceptable to design drawings. It's above my pay scale..
I would want engineering to sign off as acceptable. This is not an internet question.
Most rod busters tie these cages by setting one bar on a number of stands and after tying each tie they slide successive bars in the cage. This results in a straight cage. After they are tied they pick up the cage and move it to a staging area with a crane. It likely twisted when it sat down. It will be picked up with a crane to lower into the hole. Usually it will straighten, but I am not familiar with the rebar wire they used here.
mfgenggear
Aerospace
This is cover your rear situation. Grab the chief engineer, have them redline the drawing if it is acceptable. Put the burden on the Engineer.
However It happen it may be common. But it has to be in writing. No verbal, no internet answers.
No guessing. This can be a safety issue. Like I said it's above my pay scale.
However It happen it may be common. But it has to be in writing. No verbal, no internet answers.
No guessing. This can be a safety issue. Like I said it's above my pay scale.
Lomarandil
Structural
It's absolutely a question of spec compliance, not safety or permanent capacity.
There's a slight effect on the capacity of the cage while it's being tripped to vertical, if the cages are long enough to require multiple rigging points.
I'd have no trouble signing off on it for my projects aside from that.
There's a slight effect on the capacity of the cage while it's being tripped to vertical, if the cages are long enough to require multiple rigging points.
I'd have no trouble signing off on it for my projects aside from that.
A couple of observations.
The cages have untwisted themselves in such a way that the helix diameter would now be bigger than intended, which might reduce the side cover (I don't have a clue if that would be 1 mm or 100 mm) - probably is worthwhile measuring. I've never seen this happen before, but then again every pile cage I have seen before has been fully welded up which prevents the relative rotation of the bars to the helix.
Capacity-wise, the bars look to be maybe ~10 degrees out of alignment, cos(10) = 98%. I probably wouldn't be too worried about it.
The cages have untwisted themselves in such a way that the helix diameter would now be bigger than intended, which might reduce the side cover (I don't have a clue if that would be 1 mm or 100 mm) - probably is worthwhile measuring. I've never seen this happen before, but then again every pile cage I have seen before has been fully welded up which prevents the relative rotation of the bars to the helix.
Capacity-wise, the bars look to be maybe ~10 degrees out of alignment, cos(10) = 98%. I probably wouldn't be too worried about it.
If the c.g. of cage is significantly off the center of pile, that would be cause for rejection. If all bars are curved in a uniform helix, but remain roughly centered in the pile, I would not be concerned.
It is a judgment call on site. Welding reinforcing steel could prevent the problem, but introduces another questionable practice.
It is a judgment call on site. Welding reinforcing steel could prevent the problem, but introduces another questionable practice.
Last edited:
Lomarandil
Structural
BA, I have bad news for you about construction tolerances…
mfgenggear
Aerospace
Well it's all mute, because none of you have design authority. Op has to get his engineer to approve it, it doesn't matter
Such long rebar cages are definitely outside my area of experience, but some of the photos suggest to me someone should be concerned. Some cages seem to be too eccentric. Looks like a problem which needs a remedy.
Similar threads
- Locked
- Question
- Question
