On some jobs yes. When the bolt is 2.5 inch diameter with 6 inches exposed I can't see it getting straight without destructive force. Lots of unanswered questions..
thebionicman, post: 333423, member: 8136 wrote: I've never seen a crew allow anchor bolts noticeably out of plumb. Guess I'm spoiled. Are these on pile caps for precast columns?
Yes they are.
Jhowes, post: 333417, member: 10180 wrote: Moe Shetty had previously replied to your post. He discusses measuring directly off your grid lines.
I liked "Moes Method" better than Moe's method. it seemed to have more of a scientific bent.
Here is a sample sheet of anchor bolt verification from reference to grid lines. This job was very easy. They were using steel level plates, which already had a center dipple punch in them.
If you must locate center of each bolt, there was a jig sold by www.loink.com (very expensive like $200å±). I just searched for it, but can't find it at there site. I have seen some surveyors make their own jig.
Thanks all. Just heard back from the Project Engineer and he has backtracked and will accept the center of the bolt pattern.
Hack
Hack, post: 333513, member: 708 wrote: Thanks all. Just heard back from the Project Engineer and he has backtracked and will accept the center of the bolt pattern.
Hack
I had a feeling that's where this was going to end up. I've seen this before: where they request each bolt and then realize how impractical it is and also how it doesn't help any more than having the centers.
I can remember shooting center of bolt pattern and then set bottom nut height, lol, now that is a dandy for the resume.
All that was after either the riggers or carpenters had set all the bolts vertical.
The last one of these I did was simple. The crew would dry fit the template and bolts, rough checking themselves. At pour time we would set up on the column line and align the center of template. We came back in the next day and marked the column lines on the concrete to check the bolts. We would turn in a sheet with the hand taped ties. I'm not what they would have done had things gone wrong. It wouldn't gave been cheap...
leegreen, post: 333466, member: 2332 wrote: Contractors can bend bolts, or drill and core new ones.
As I'm sure you are probably aware, it just depends on the application. Not all anchor bolts will bend, or even flex for that matter without massive amounts of force applied (which is not good for the concrete or the bolt). Try "adjusting" a 2-1/2" dia. A490 anchor bolt. Not going to happen.
Having a back-up plan of drilling and coring new bolts is also a very risky in many cases. Most anchor bolts I have seen are tied together with an anchor plate that is buried in the concrete. A good engineer has anticipated that there may be issues and has a larger safety factor that they dip into on rare cases, but sometimes it is just plain FUBAR.
Getting ahold of a couple of the templates used in the pour makes easy work of the survey. We often ask for a plywood template. Mark centers on the template, thread the nuts down and place the template over the bolts. If that isn't available, you can use a string and run a figure eight pattern around the bolts to find the center of the pattern.
Having done a lot of bolts. It pays to turn scavenger at the start of project and look around for plastic bottle tops and tin tops of varying sizes. Then drill or punch a hole for the mini prism to sit in. This will get you out of trouble up to around 50mm (2 inch). with regard to lean, if the contractor cant fix it, get a small spirit level and measure the lean to the south, and to the north and record it.
The center of a bolt pattern assumes that the pattern is correct. Measuring each bolt is a better method as is records the spread and rotation of the bolt pattern.
Measuring the center of a bolt pattern does not show which bolt is off.
Mike Falk, post: 333700, member: 442 wrote: The center of a bolt pattern assumes that the pattern is correct. Measuring each bolt is a better method as is records the spread and rotation of the bolt pattern.
Measuring the center of a bolt pattern does not show which bolt is off.
[sarcasm]If they used a template, the bolts have to be right....right?[/sarcasm]
Pattern center versus individual is an easy decision if you understand the work flow of the contractor and the purpose of the bolts.
When I see a crew orienting the template the same every time and double stringing the column lines before during and after pour, they will probably get a pattern center. If they are loosy goosy and it's 40 foot columns I'm checking every bolt.
Right method, right tool, right job. It's not that hard...
I should have clarified and agree
with all comments. We use the template to insure the "pattern"
Is in tolerance. There have been times when we've had a laborer go out ahead of us and test fit to ensure the templates fit. If OK by the client, the laborer will plumb the bolts that are out and causing a failure. Once these requirements are met, you can drop the template on, and shoot the centers. This should give you a very good idea as to where the true center of column will sit once placed. I used this method on large warehouses along with hi-rises and power plants. Years ago we used to shoot individual bolts but found that it often muddies the waters over nothing and isn't practical to the steel guys.
We now meet with the client. Have the ensure all bolts have been plumbed, templates verified and fit, then do the survey. If the template won't slide down, one will automatically know that the base plate won't either and needs a closer look to see if a singular bolt is causing the issue. We then enter the findings into a spreadsheet and generate a report as to were each pattern is in relationship to an "X" and "Y" axis.
The reality (in my experience) is that if a 3/4" bolt is out of tolerance by 3/4", it's virtually impossible to cut off the bad and drill another bolt next to it securely and accurately. At this juncture, the normal course of action is to slot the base plate and the concrete guys eat the T&M for the modifications.
Another issue coming in for third party verification is being able to buck-in to the contractors control. We've found it easier to setup independently, shoot the patterns from the least amount of setups as possible and allow everything to fall into place without any preconceived notions as to how it should be. Take the info, process it and see if we are able to successfully rotate everything into a best fit scenario. Being sure to tie into site controls and any other areas that are critical tie-in points.
