OVERLAPPING MEMBERS...NEED HELP 5

[engrbon]

Hi guys I've been trying to use a software to model a steel truss where the bottom chord is on top of a concrete beam along its full length. I was able to create the model but the program is issuing a warning message saying that the members are overlapping. Will this affect the analysis and design of the whole structure? Thank you.

 

[msquared48]

Glad to be of help. Good luck.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[engrbon]

@Sir Ron thanks!!!

 

[Ron]

No problem! Good Luck.

 

[hokie66]

Glad to see that Ron and Mike have helped with your problem, but I am still not convinced that they have addressed the right problem. When you said the bottom chord of the steel truss is restrained by "wrapped dowels", I took that to mean the dowels are for horizontal bracing only, not for vertical load sharing. A detail would help to show the intent.

 

[paddingtongreen]

I've been thinking that too, hokie. I'm trying to imagine a truss that cannot deflect because the bottom chord is in contact with a wall, continuously?or at intervals?

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[msquared48]

OK... I can see thaat scenario.

The dowels, at 4'-6" OC, if they slip up and down within the concrete beam, and being welded to the truss, may be solely for lateral support of the bottom flange of the truss...

If the vertical deflection of the truss, however, exceeds the vertical slip capacity of the concrete beam connection, whatever it is, then a vertical load could be imparted to the concrete beam.

In all likelihood, at the 4'-6" spacing, a measurable degree of composite action may be a pipe dream. As mentioned, a good detail of the connection would answer a lot of questions.

I had previously envisioned these dowels as embedded in the concrete beam and welded to the truss.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[apsix]

When I see a comment like;
'the truss is deflecting with the beam I can see from its behavior that it's acting as part of the beam. Well I think I just have to move it away...and revise their plans. Lots of work though',
it's obvious that you need the advice of an experienced supervisor.

Asking questions on a forum is not the best place to get that advice.

 

[engrbon]

@Sir Apsix, msquared48 envisioned it correctly.

I encountered some errors so I need to find a solution, that's why I'm hoping for some relevant technical answers so I can weigh, check and apply it to the problem accordingly. I'm very thankful to some members who shared their opinions relevant to the matter in hand.

Contrary to your opinion, I find forums very helpful, you can get lots of great ideas although, there are some irrelevant and unnecessary comments, but generally, seeking advice inside open forums is still one of the best way to find the answer/s that you're looking for.

One more thing, I don't think my experienced supervisor will be happy to help me with some part time jobs after my work in the office.

To the members who took some time to share their ideas addressing my queries, I'm very thankful to you guys. And to those who did otherwise, maybe next time you can at least just try to extend some help.

 

[apsix]

engrbon
I was just a bit concerned that you apparently contemplated changing the building plans because you couldn't model it in your analysis software. That's the tail wagging the dog.

I'm not trying to steer you away from using the forum, I've learnt a lot here and I'm sure you can too.
As for 'unnecessary comments'; they come with the territory, whether you appreciate them or not.

 

[TXStructural]

If you are modeling two members, which have different centers of gravity/inertia, you should be modeling them as separate members, connected at intervals. Model the connections using notional connecting members - in RISA 3D there is a way to specific way slave these together with infinitely stiff & strong connections. In other software, you would create a series of stiff connecting members.

Otherwise, determine the properties of the composite member and model it as a single member using these properties.

It sounds like you may be doing work outside of your expertise without supervision by a licensed structural engineer, which none of us here would recommend, and most place in the US prohibit.

 

[engrbon]

@Apsix, please accept my apologies. Thanks.

@TXStructural, Thanks. Just wanted to try the software, I want to learn more that's why I'm asking, if others are ashamed to ask because other people might think that they don't know anything, count me out. I will ask if something confuses me. I not only use all the brains that I have, but all that I can borrow. That is the reason why I'm here to learn from experts like you. Thanks again for the input I will look into it. As for now, I'll wait and see, all the documents and plans are with the building officials for approval. One more thing, nothing to worry, I have my own professional license and legally allowed by law to practice.

@Everyone, Thanks for all the valuable comments, you are my expert supervisors.