RFEM - the effective length is not defined 1

[Pretty Girl]

Why these errors occur? This is a very basic structure to test the software. I did their steel hall tutorial as well before which it ran smoothly without any errors and at that the RFEM didn't ask to set effective lengths manually.

I just drew four legs, on top of the drew another four legs, connected those with beams and bracings and put hinged support. When I click the analyze button, it throws these errors.

Why don't it just automatically calculate the effective lengths etc. Or is it saying some other thing that I should have done?

Tension braces are also just steel beams (I just wanted to test it without wasting much time)

 

[strucbells]

I don't know this particular program (most of my modeling has been in RISA3D), but usually these types of errors are related to defining your member end releases (ie if the connections at the ends should be modeled as fixed or pinned) and the continuity of your members.

I would draw the columns in as continuous members rather than breaking them at the intermediate level, and put in the member end releases for all elements other than the columns as pinned, and re-run. Usually you will need one member at a joint that does not have end releases for stability (even if it is a pinned condition).

Also you may need to define your bracing members as braces and your column members as columns so that the program knows how to treat them correctly.

 

[KootK]

Why don't it just automatically calculate the effective lengths etc.

Because that's analytically impossible without getting into an advanced buckling analysis. Most FEM packages used in production structural engineering environments are the same way. It's a feature in the sense that it encourages designers to exercise their engineering judgement in one of the few meaningful ways that is left to them nowadays.

It sounds as though you are a pretty girl with rather limited patience.

If you are seeking FEM software that indiscriminately analyzes whatever chicken scratched thing you draw in thirty seconds or less then, truly, I hope that you don't find it.

 

[Just Some Nerd]

Perhaps a bit too discourteous for my liking, Koot. PG's posts typically give me the impression of lack of experience and the absence of someone who can provide meaningful guidance or a complete understanding of things, hence their presence here on the forum. In this case it seems they've done a tutorial and are playing around with the software to gain an understanding, so I wouldn't be so quick to judge. I think they're being quite literal when they are asking why the software can't calculate certain things on its own even for a very simple structure, it's not something I'd have figured out my first time using say Spacegass - I didn't know jack about the limitations vs capabilities of that variety of software, I was just a grad at the time trying to be productive.

 

[KootK]

so I wouldn't be so quick to judge.

Quick to judge? We've had a steady stream of day zero level questions from Pretty Girl for the better part of three years now. Three years. Even in a complete mentorship vacuum, it shouldn't take that long for a motivated self learner to find their feet with respect to the basics.

Moreover, I've always suspected that Pretty Girl's handle is a version of catfishing. Bait a bunch of pasty cubicle dorks into giving him more than his share of team resources and serving as his white knights when needed. I find it offensive and unprofessional, even for the internet.

Am I making some assumptions from afar here? You bet. Sue me. I call 'em like I see 'em.

 

[STpipe]

Without knowing the details of the model, it sounds like you inadvertently deactivated/deleted something that impacts the stability calculation. By default the program should be setting the effective length as the length of the member (which can be very wrong, but at least there is a starting point), and if it's attempting to calculate Mcr using a buckling analysis, by default the program should be setting boundary conditions at each end of the member, so it should give you a result, even if the result is inaccurate from a stability perspective.

 

[ThomasH]

Why don't it just automatically calculate the effective lengths etc. Or is it saying some other thing that I should have done?

If you are learning or evaluating a software, why don’t you ask the developer directly?

 

[Pretty Girl]

@Just Some Nerd @strucbells @STpipe

I got it solved today, it actually was the effective length not being set by default.
I didn't expect it to not to calculate the effective length when I have already connected the nodes.

I was not surprised by the empty values (it's actually good to leave it blank than assuming it self), but it's inability to calculate the effective length by it self even when I have already connected the nodes was surprising to see.

The steel connections at a common node means it transfers the loads. So the software already knows the effective length as it already knows the stiffness, member thickness, material it's made of etc, so inability to calculate it by it self is surprising.

@ThomasH
Yes using the trial version, but they don't respond actively in their forum. These types of questions can't be asked through email support.

But to be honest, the software is pretty cool though.

 

[Pretty Girl]

Quick to judge? We've had a steady stream of day zero level questions from Pretty Girl for the better part of three years now. Three years. Even in a complete mentorship vacuum, it shouldn't take that long for a motivated self learner to find their feet with respect to the basics.

I get your frustration but still I'm a slow learner. Who knows may be I have thousand more years to learn or infinity. So imagine you're measuring time in years.
However, it's interesting to see that you have noticed me for the past three years.

Moreover, I've always suspected that Pretty Girl's handle is a version of catfishing. Bait a bunch of pasty cubicle dorks into giving him more than his share of team resources and serving as his white knights when needed.

Catfishing? How come? I don't think anyone here providing answers just because my user name is "Pretty Girl". Did you?

 

[STpipe]

The steel connections at a common node means it transfers the loads. So the software already knows the effective length as it already knows the stiffness, member thickness, material it's made of etc, so inability to calculate it by it self is surprising.

Maybe there's a language barrier here or a difference in terminology, but that is not correct at all. Are you sure you're not referring to the buckling length?

 

[ThomasH]

The steel connections at a common node means it transfers the loads. So the software already knows the effective length as it already knows the stiffness, member thickness, material it's made of etc, so inability to calculate it by it self is surprising.

I think you need to take some time to understand buckling and effective length. My interpretation is that effective length and buckling length are the same in this context. A suggestion is that you start with a simple column with top and bottom pinned. Then a vertical force att the top and calculate the buckling load (Euler).

Then use something like the model in your first post. But instead of 2 levels use 10 levels or more and a horizontal support at the top. Then calculate the effective length for one of the vertical members (columns). It will probably be longer than the distance between the horizontal members.

Yes using the trial version, but they don't respond actively in their forum. These types of questions can't be asked through email support.

I have no idea regarding how active they are on their forum. But the statement that this type of questions are not suitable for email support, that is in my opinion just wrong. What is it that you can do in this forum that you can't do with email? The only possible limitation I can suspect is when you are using a trial version, that may not qualify you for support.

An email with the file and a short description of the question. I have used the approach several times and it usually works. The difference is that when you do it with the software support they hopefully know the software.

My impression here is that your understanding of "effective length" is not sufficient. And "teaching" or "learning" that on the Internet as not always the best approach.

 

[EngDM]

I have no idea regarding how active they are on their forum. But the statement that this type of questions are not suitable for email support, that is in my opinion just wrong. What is it that you can do in this forum that you can't do with email? The only possible limitation I can suspect is when you are using a trial version, that may not qualify you for support.

An email with the file and a short description of the question. I have used the approach several times and it usually works. The difference is that when you do it with the software support they hopefully know the software.

Some companies will not give help to non-licensed customers (ahem RISA). I am not sure how Dlubal treats trial subscriptions by way of technical support.

 

[KootK]

I don't think anyone here providing answers just because my user name is "Pretty Girl". Did you?

No, I didn't respond because of your handle. The opposite really. I generally try to avoid participating in your threads precisely because of my discomfort with your handle. But, alas, my self discipline has failed me on this one. Imagine that you are me, trying to help you out on a thread:

1) If I am on a corporate network of some kind, then even typing the contiguous words "Pretty" & "Girl" into my computer feels like organizational suicide. I might has well pick up an "I KIDDIE PORN" tee shirt to wear to meetings.

2) If I am on my home computer and my wife stops by to ask what I'm doing, I do not relish having to say "Oh, I'm just chatting with Pretty Girl about erection tolerances".

3) Helping you feels dirty to me precisely because I suspect that you are deliberately abusing the good will of this community. Feeding the animals and such.

That said, chauvinism still holds some sway despite society's best efforts to eradicate it. I am much less concerned with whether or not anyone here is motivated by chauvinism than I am with what I perceive as your attempts to exploit it.

 

[ThomasH]

Some companies will not give help to non-licensed customers (ahem RISA). I am not sure how Dlubal treats trial subscriptions by way of technical support.

I am well aware of that. But I have also received excellent technical support for a trial when I tested software with the intent to buy. But, like you, I don't know Dlubals policy for this .

 

[KootK]

Some companies will not give help to non-licensed customers (ahem RISA). I am not sure how Dlubal treats trial subscriptions by way of technical support.

There isn't a software company on the planet that would turn away a legitimate request of the form:

I am considering becoming a paying customer of yours if only I could sort out this minor technical issue. Can you help me?

This thread exists because @Pretty Girl is lazy. Too lazy to expend the effort to resolve his own, long standing incompetency. And too lazy to make the effort with RFEM's tech support.

Better to play the damsel in distress card and let the fine folks at Eng-Tips expend their effort instead.

Rapunzel, rapunzel... do let down your hair.

 

[KootK]

Catfishing? How come?

Probability I suppose.

Many of our number here are female structural engineers. And at least a dozen of them are women that I know personally, in real life. One of them is my wife.

Without exception, every female structural engineer that I know personally finds it a struggle, to some degree, to be taken seriously in what remains a male dominated profession.

How seriously do you think that you will be taken, operating in a work adjacent space such as this forum, with a handle such as Pretty Girl?

And how do think that it makes the other female engineers on this forum feel to see you setting women's rights back to the Cambrian with your choice of handle?

So which of these options best describes your handle choice here @Pretty Girl:

A) You are a male choosing to present yourself as a young female on this forum?

B) You are the most un-feminist female engineer to ever pick up a calculator?

C) Your recently deceased grandmother went by the nickname Pretty Girl and you chose your handle to honor her?

D) You somehow did not anticipate that your handle would be problematic. Perhaps, in addition to being new to structural engineering, you are also new to Earth? Or maybe you have a developmental condition that has rendered you devoid of empathy?

Speaking probabilities, I'll give that 95%, 1%, 0.5%, 3.5%.

That's how come.

So why choose Pretty Girl? Why not:

- PG?
- PGurl?
- PrettyG?
- ButterFace_AgeOfConsent?

 

[milkshakelake]

@KootK Devil's advocate;
E) Pretty Girl could be a transwoman.

They tend to use names like that. If that's true, I'd say it's a valid escape hatch rather than a nefarious ploy.

I've responded to Pretty Girl before, and I won't lie - a lot of what you said went through my mind as well. But I give people the benefit of the doubt and treat them like a random human. Colorblind, genderblind, and all that. It removes a lot of assumptions and accusations. Tangentially, I also give people benefit of doubt when they don't know something seemingly trivial, because I have no idea what their life is like. I know I got some coddling when I was but a fledgling on eng-tips and in my first few years of engineering. (Now hoshang threads - that's a whole other story.)

 

[KootK]

E) 0.5%

If you are right then I am helping OP to better understand how his choices are impacting others and how others perceive him.

Henceforth, I wish to be known as. Nookie4FEMAdvice.

I'm good for it and it's healthy to be sex positive, right?

 

[ChorasDen]

Since Pretty Girl's location comes up as Australia, perhaps the Gorgeous Mate! handle was already taken?

 

[JoshPlumSE]

I am well aware of that. But I have also received excellent technical support for a trial when I tested software with the intent to buy. But, like you, I don't know Dlubals policy for this .

Dlubal makes the RFEM software.... I'd forgotten that.

I've never used it personally, but one of my own colleagues who now lives in Philadelphia (I believe?) is their main US rep. Or, she was just a year or two ago. A friend of mine was looking for some structural software that could do something a little weird. He works on pools and does some weird curved shell geometry.

Anyway, I point him towards RFEM based on a conversation I had with my former colleague about something she had highlighted about that program. He contacted her and they provided a bunch of help. He didn't end up purchasing it at that time because the work (which was mostly side work, not his 9 to 5 job) dried up for personal reasons. But, if he jumps into a project like that again then I'm confident that he would probably start with RFEM before others.

That being said, if the OP is in Australia, I would not be surprised if the support available there is limited.

Caveat:
I worked or RISA for 16 years (which is where I met the Dlubal gal). And, I currently work for a different competitor of Dlublal. I can be considered a biased individual on all things related to Structural Engineering software. I'm a not intending to promote this software (or condemn it). Just telling relating my friends experience here in the US with Dlublal being willing to provide good support / customer service in pursuit of a sale.