column/plate sizing and verifying 2

[Pimech]

Hi!
I should verify (and eventually resize) the following column.
It is made by a bottom and a top plate with two squared steel tube 200x200x10mm (welded to the plates). Please see attached sketch.
The bottom plate will be fastened to the floor through bolts.
I should choice bolts number and position.
How could I proceed? Any advice is welcome.

Thank you

 

[klaus.]

How could I proceed? Any advice is welcome.

you should proceed by contacting a structural engineer around you

 

[Pimech]

I'm contacting (I suppose) structural engineers on this forum because I'd prefer to learn this calculation.

 

[klaus.]

on this forum because I'd prefer to learn this calculation.

but this forum is NOT a student forum.....

 

[Pimech]

I can't understand what you mean for "student forum". I read a lot of threads asking for advises and suggestions.

 

[r13]

Most people here are practicing engineers. We offer our advices/suggestions/opinions to one another knowing the receiver has the basic technical training and background, thus he can judge the weight/correctness of those offering, and won't result in critical mistakes and failures. But we are not teaching professionals, and this forum is not an education institution either. It is both unethical and dangerous for not knowing your intention and intended uses of this knowledge acquired through a non-conventional learning source.

 

[JAE]

Pimech,
Choosing the number, diameter, length and type of bolts to a floor to resist the overturning moment on the column depends on a lot of variables.
It is not simply teaching you a calculation.
In the US, we have code guidance from ACI (Appendix D of ACI 318). I'm not sure what your local standards or codes are.
You could research the governing codes and see what type of bolt-to-concrete systems are approved and how their capacity is calculated.
You didn't tell us what the floor was (Concrete, steel, wood, or something other).
So if you can find a local engineer who is familiar with your local codes, that would be the best way - then learn from them.

A good first step is the engineer.
Otherwise, look at HILTI Profis Anchor design software.

 

[JoshPlumSE]

Pimech -

This isn't a standard base plate type of connection. There aren't any "standard" design routines for this situation that you can just pick up and read through.

If you were a structural engineer, you would probably have come up with a connection detail and ask for comments / criticism on what you had provided or the methodology you had used.

We (the structural engineers on this forum) can be a little sensitive when non-structural engineers assume that they can learn structural engineering sufficient to complete a design by merely posting a couple of questions here.

Please don't take those comments by others as a personal attack against you. Rather they are an expression of frustration that you're asking a bit too much of this forum. And, that people who do this may not always respect the complexity of structural engineering work and the experience and knowledge required to do it well.

 

[Pimech]

Thank you for replies.
@JoshPlumSE I could underestand your comprehensible reply.
But.. but I didn't ask any design routines "pick up and read". I didn't ask for building/executive design. I didn't ask for a calculation report.
I just asked for some advices on a sketch. Yes it is not a standard baseplate, otherwise I would have found a lot of calculation (as example) based on neutral axis.
I'm a mechanical engineer, I'm not a student (even if we all know that you never stop learning) and I had experience in other engineering sectors. I am developing a preliminary design (for this reason I didn't specify the kind of floor, steel type, ecc.), I don't have many constraints in this phase and you know that engineering problems can be solved modelling and approximating. My engineering problem wasn't to get a certified report to start the construction, but to get advices on how to start sizing in a preliminary design.

I don't see "call a structural engineer around me" as an attack against me. But I didn't find helpful it in this design phase.

 

[r13]

Pimech,

Since P & M are given, and preliminary foot print of base plate has been selected, the tension in the anchor bolts can be determined by simple static - rotation about an assumed toe/rigid point, and obtain the compressive stress either through straight line method, or ultimate stress block method. The above sounds simple, but there are many other considerations may affect your design. For the start, I suggest to get a copy of AISC DG 1. It is free if you are a member.

 

[JoshPlumSE]

Pimech -

There isn't a single right answer to your question, it requires a good amount of engineering judgment. There are lots of possibilities. Use Yield Line theory. Check bolt prying, assume a rigid plate, analyze with FEA. Each one of these requires a good "history" of structural knowledge to understand. Hence the "call a structural engineer" comment.

 

[dik]

and go to a thicker base plate and eliminate the stiffener if you can.


Dik

 

[dik]

Is it laterally supported at the top and why are the HSS so large for such a small load and moment? Do you need two HSS?


Dik

 

[Pimech]

Is it laterally supported at the top and why are the HSS so large for such a small load and moment? Do you need two HSS?

Yes, I need two HSS for afunctional requirements.

and go to a thicker base plate and eliminate the stiffener if you can.

Why do you think is it better to remove the stiffener?

Thanks to all

 

[JAE]

dik is probably observing that welding and fit-up of plates sometimes is much more expensive than a simpler configuration with heavier plates and shapes.
(i.e. less labor)

 

[strucbells]

At least in my market (USA) labor cost >> material cost. All of the AISC guidelines for economical connections are to eliminate stiffeners and additional welding/fabrication by upsizing members and plates whenever possible. There are times when you can't avoid it, but it's a good rule of thumb to follow.

 

[dik]

Why do you think is it better to remove the stiffener?

it's generally less costly and nothing to trip over. Also designing an HSS face for a stiffener can be difficult.

Your loads and moments are so small that your base plate will be minimal and likely not very thick... even thicker base plates are generally less costly. For your load and moment, in particular if supported at the top, your columns are quite large.

If you need 2 columns, do they need to be connected? and, can they be a lot smaller. Your columns (as a rough mental guess) have a capacity of about 1000 kN, each.

Dik

 

[dik]

dik is probably observing that welding and fit-up of plates sometimes is much more expensive

much more than sometimes...

Dik

 

[sticksandtriangles]

Not to side track this conversation too much, but is there a thickness where the addition of stiffeners starts to make any monetary sense?
I just sized up a 7" thick baseplate under a fixed base high seismic moment frame.

I plan on doing a quick comparison study to see what the baseplate thickness would be if I added a few select stiffeners.
Hope to send these results off to a steel contractor and see what they say.

S&T

 

[dik]

That's why I said 'generally'... never seen a base plate that thick... wow.



Dik