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What are exact loads on column?

What are exact loads on column?

What are exact loads on column?

(OP)
Hi.

Cant seem to figure out exactly what loads are acting on steel column and how to design it.
Does the column have two loads acting on it? Axial load from top (which is used to check Compression and Buckling) but what happens with point load from diagonal bar?
Please help.


Thanks!
Ale

RE: What are exact loads on column?

the column takes like a beam, cantilevered at the base

another day in paradise, or is paradise one day closer ?

RE: What are exact loads on column?

The axial load on the lower column is 18*5.13 = 92.3 kN

If the diagonal intersects the beam at midpoint, the axial load on the upper column is zero, otherwise it could be in tension or compression.

The moment in the lower column is constant: M = 92.3*5.13/2 = 237 kN-m from top to bottom.

The moment in the upper column varies from 0 at the top to 237 kN-m at the bottom.

The horizontal force in the upper beam and diagonal strut is M/h where M is the moment in the lower column and h is the height of the upper column.

BA

RE: What are exact loads on column?

As a structural "engineer" you are calculating to two decimal plates the structural loads you cannot define in basic terms?

RE: What are exact loads on column?

Quote (racookpe1978)

As a structural "engineer" you are calculating to two decimal plates the structural loads you cannot define in basic terms?

What the heck does that mean?

BA

RE: What are exact loads on column?

Quote (BAretired)

What the heck does that mean?

That made laugh. I thought the same thing. Chastising an engineer for using too many significant digits? At least we know he is an engineer based on the poor grammar.

That aside, this looks like a homework problem. An engineer (even one just graduated) should know how to do a free body diagram.

The assumption was made above that the base is a fixed (momented) connection. Is that true or did the rest of the beam get cut for the sake of the upload? If it is fixed, the worst-case condition for the column occurs below the brace connection and you don't need to know anything about the beam or brace to design the column. Designing the connection of the brace and beam to column is a different story though. The amount of axial load the brace takes is a function of its stiffness which is probably outside your comfort zone based on the question. I'm not trying to sound mean, but part of being an engineer are the assumptions you make.

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

RE: What are exact loads on column?

P1ENG, not to mention that the use of significant digits above... wasn't even excessive!

RE: What are exact loads on column?

atrizzy,

My old boss used to have a picture from a magazine that he cut out. It was of a guy, back towards you, hands on head pulling hair, looking at a white board in a lecture hall filled with complex equations. My boss then decided this was him and added his own artwork of a thought bubble: "Juston, I just wanted a simple beam calculation". I have been accused of trying to be "too accurate" and too many significant digits was a staple of mine as a young engineer.

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

RE: What are exact loads on column?

Being a good young engineer also involves the ‘staple’ of having a reasonable grounding in engineering basics like Engineering Mechanics and Strength of Materials, and having the ability to adequately define your problem with sufficient engineering detail to generate a meaningful discussion. We shouldn’t be teaching the very basics of engineering to someone who has a CAD program (otherwise they couldn’t even draw a sketch) and wants to pretend to be an engineer, just to boost the member numbers for ad dollars. We have so many non-engineers on E-Tips these days, just becuase they can join without any real vetting, that some significant percentage of the OP’s aren’t even worth wasting your time trying to guess what they want and need, other than a lobotomy. But, even if they only think they are having a technical brain fart, they know they can come here and a bunch of pretty smart people will waste their time trying to figure out what the guy/gal needs, by playing 20 questions with them. We just shouldn’t bother to respond to many of the OP’s. and maybe they’ll go away. We certainly shouldn’t be doing their very basic tech./engineering thinking for them.

We should have a stock statement/answer for dumb questions like... “show your boss how much engineering you really know, ask him this same question, this same way.” Or, “provide a meaningful, well thought out, engineering question, with a well proportioned and dimensioned sketch, and sufficient engineering detail, or we won’t try to help you. This is E-Tips, not 20 questions or high school science class.” I fear that much of the/our discourse these days is doing serious damage to E-Tip’s reputation as the place to come to for serious engineering discussion and exchange of ideas.

RE: What are exact loads on column?

That is a Tekla screenshot, and the sig figs of the software is set to two decimal places. He has used the dimensioning tool within tekla to create the sketch posted. It is not uncommon when modelling to use two sig figs to avoid incorrect part numbering. I do not recall if Tekla offers a school edition, but if not, that is a $20k+ software package. It might not be a homework problem. As for the underlying question, yikes.

RE: What are exact loads on column?

"when modelling to use two sig figs to avoid incorrect part numbering" ... ? how are dimensions related to part numbers ?

and the upper vertical segment is 1854mm long (or 1854.15mm if you prefer) (assuming the diagonal is to the middle of the horizontal)
or it could be 2238mm if at 45deg
or ...

another day in paradise, or is paradise one day closer ?

RE: What are exact loads on column?

The software compares parts based on the numbering settings (length/orientation/holes...). Based on those settings the software automatically assigns part numbers. If one's model becomes sloppy then parts the modeller thinks should be identical to others can end up with unique numbers. It can be tiring to track down those errors, so many become quite fussy. I worked with a consultant in Austria that thought working with 16ths or 8ths was very odd and difficult to maintain accuracy. In a simple case like this it is unimportant, but when one starts dealing with complex structures it becomes much more important. Most have standard templates for different project types.

I don't prefer the accuracy, I was merely suggesting it could be a standard company setting and we could overlook that aspect of the post.

He snapped the overall lengths to whatever reference points he was using in the model. Yes, he did miss one dimension.

RE: What are exact loads on column?

"Based on those settings the software automatically assigns part numbers." ... how bizarre (IMHO), not to have control over part numbers ! why wouldn't you number the first part -001 (or -101) ?

another day in paradise, or is paradise one day closer ?

RE: What are exact loads on column?

Compared to feature based modeling software, the numbering and tracking of parts/assemblies is much better in Tekla for structural work. The advantage is the numbering is automated and the software compares parts to find common parts instead of the user having to keep track of what is or isn't common. You can edit the numbers and alter them if you choose, but that is time consuming when you have 1000's of parts and a team of modellers. We have detailed simple structures in solidworks and many in Tekla, and there is a reason the vast majority of steel fabricators still use tekla.

I suspect in your work you create standard parts that you build year in year out until it is taken out of production. In structural work part numbers are used to track the part thru the plant, and on site, but it is rare one would ever re-build that exact part in the future. Once a part is erected the part number has virtually zero importance after that.

RE: What are exact loads on column?

actually we create unique parts all the time (even reidentifying old parts, reused designs, with new numbers). Part numbers (drawings) were project dependent (ie the base of the part number was the project number), so unique numbers made some sense. Now parts are zonal (ie the base of the part number depends on where (or what) it's doing) so maybe re-using parts could make sense.

another day in paradise, or is paradise one day closer ?

RE: What are exact loads on column?

Quote (P1ENG)

I have been accused of trying to be "too accurate" and too many significant digits was a staple of mine as a young engineer.

Navigating different opinions on the correct number of significance has always been a frustration of mine. Some engineers have extremely precise opinions on just how precise answers have to be. You have to remember which boss likes which level of accuracy and under which circumstances...

I remember we had one lecturer who wouldn't even accept answers that weren't the correct number of significant digits.

RE: What are exact loads on column?

BART. ,maybe...

As a structural engineer, your loading is generally approximate and not precise. I generally think of the design as a guide to what is required realising that loading/forces are not correct to the nearest 2nd or 6th decimal poing...

Dik

RE: What are exact loads on column?

Quote (Wise Old Man or Woman)

Arguing with an engineer is like wrestling a pig in mud. After the first few hours, you realize they enjoy it.

-Mac

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