Anchor Bolt Tightening

[Canucks1010]

Hello,

I have a heavily loaded column with 8 anchor bolts. The foundation and anchor design was done by others (prior to me on the project) and is already IFC. I am tasked with finalizing the steel structure only. So regarding why the anchors were laid out a certain way - I am not able to comment nor do I agree how they were done - just need to try and work with it.

The issue I have is for the baseplate design, we have gussets for vertical bracing that will restrict access to the anchors. I am having trouble picturing how the interior 4 anchors will be tightened, since the exterior 4 are "in the way". Only snug tight is required, the anchors are 1-3/4" diameter.

Can someone please comment on experience as to how these nuts can be tightened?

Thanks!

 

[dik]

Just a bunch of questions:

I'm not sure why so many gussets? in particular the ones off the tip of the flanges? The bolts are not arranged to be a real resistance for moment, so mostly axial load? Could the BPL be 30x30? and do you really need the gussets? I forgot to answer the question... I'd tighten them from inside to out on either side about 1/3 of the torque value and then tighten them in the same pattern for 2/3 and for full torque.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[phamENG]

If those stiffener plates are absolutely required, could they be field welded after the anchors are tightened down? Other than that, they'd need a really long extension for their wrench...

 

[WinelandV]

I, too, am curious why you have so many stiffener plates. Would it not be easier and cleaner to thicken the baseplate to remove some of those stiffeners?

Please note that is a "v" (as in Violin) not a "y".

 

[dik]

Analysing those stiffeners/gussets is a real chore sometimes. I prefer not to use them if I can avoid them. They are expensive items to add. I would never field weld the gussets... and the anchor rods would likely be installed outside the column footprint if I were doing the project.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[JStephen]

For small stuff, you'd use a breakover bar, socket, and extension bar. That stuff should be available in 1" square drive. Would that not do it? If spacing allows an impact wrench, that'd speed it up.

 

[canwesteng]

With a wrench and an extension bar? I don't see an issue here as long as it sketched to scale. The bracing won't be there until the anchors are installed.

 

[BridgeSmith]

1-3/4" socket with a couple of long extensions and a breakover or ratchet, is the only way I can think of to get to them.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[Brad805]

Here is an image of the geometry. Seems like a solvable problem, but you will have to figure out what tools fit. The brace bolting seems it could be challenging as well.

Found model of impact gun for up to 42mm bolt. Might work, but 1.75" = 45mm. Did not find a model of the extension.

 

[dik]

We didn't say it wasn't solvable... as an aside, what is the purpose of the little stiffeners at the end of the flanges? I'd make the plate 30x30 and put all the anchor bolts outside the column footprint and remove all stiffeners except the gusset needed for bracing.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

Something like...

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Brad805]

Dik, its his job to figure it out. I asked Dr. Z a question like this before, and he posted a CAD view of the connection with the tool included in the dwg.

Dik, IFC and "...- just need to try and work with it."

 

[dik]

Even a 1/2" thicker base plate, this would be less costly... If it hasn't been fabricated, and won't mess with the schedule, I'd issue a change notice.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Ingenuity]

Another option may be to consider an external bolt/rod 'chair' (possibly a pipe sleeve and cap plate) like those used on vessels, crane bases etc. Also allows you to preload/pretension the anchor rods with substantial free length. Obviously the anchor rods would need to be extended (longer).

 

[Canucks1010]

Hi All,

Thank you all for the input. I am in complete agreement that the anchor arrangement is wrong (or not efficient let's say) - but again the foundations and anchor bolts are complete and I am unable to change this.
I was not part of the project when the foundations were designed as such.

Regarding the question of the stiffeners - These are provided to ensure equal distribution of the tension load to the further anchor bolts (anchor capacity for tension breakout is 125k) and to reduce the local bearing pressure on the base:

I will definitely look at reducing the length of the stiffeners required to allow more access. Regardless of the stiffeners, the confinement is mostly provided by the central brace gusset. With what you have said, I feel it is feasible to tighten the anchor bolts.

I have also looked at the option of using a hydraulic bolt tensioner (as is used both pipe and vesssel bolt-ups and wind turbine foundations) - and this feasible and can fit in the confined space as well.


Thanks again for all the input and help!

 

[dik]

Have you taken a look at eliminating the little stiffeners right angle and at the end of the flange of the W. I really don't think they are doing much...

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Canucks1010]

@dik

You bet! Again - I just got handed this and first thing I saw is "how are you going to access those bolts... ". I spent an hour on a quick analysis to get a feasible baseplate that met the anchorage design. Now that I agree we can tighten, I can burn a couple more hours sharpening the design.

Super tight budget on hours these days... thanks for the valuable input!

 

[dik]

...not hours, minutes... easy thing to check and difficult to analyse...

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[bugbus]

Canucks1010 - can I ask what software that is you have checked the baseplate with?

 

[dik]

I come from a different time... I'd simply have used my Excel or SMath program... just a couple of minutes and it's done...

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik