×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Wrong Reactions ETABS

Wrong Reactions ETABS

Wrong Reactions ETABS

(OP)
Hi everyone!.

I have modeled a simple frames, and when I check the reactions due to self-weight, I am surprised that they are incorrect.
Reactions should be 972kgf, however ETABS gives a result of 939.6 kgf.

RE: Wrong Reactions ETABS

The weight per m is 0.3*0.3*2400 216kgf. The length they are using is 2*939.6/216 = 8.7m. They appear to be deducting 15cm from each column (or from each end of the beam) to account for the fact that your dimensions were centre to centre of member. Your calculation includes the overlap twice, so they are correct.

Edit: Oops, I nearly fell into the same trap. I think your figure is correct. The total length of two columns and one beam should be 9m, which makes your calculation correct.

BA

RE: Wrong Reactions ETABS

(OP)
Hi @BAretired!
thanks for taking the time to reply.

You're right, I hadn't seen from your perspective.

So, ETABS already considers a real model, as can be seen in the image, even ETABS applies an automatic rigid link, while SAP2000 does not do the same.

If I consider a beam length of 2.70m, I will get reactions of exactly 939.6 kg. I for a moment thought that there was a bug with the software neutral



My question is how much influence modeling and calculating buildings as it does in SAP2000? It would be dangerous?

RE: Wrong Reactions ETABS

Quote (TonnyCIV)

I for a moment thought that there was a bug with the software

There is a bug with the software! And you found it! Fortunately, in this case, it doesn't make much difference to the result. There may be situations where the result could be affected much more than this, which is why one should always do a sanity check on any results coming out of a computer, particularly when using a new piece of software.

BA

RE: Wrong Reactions ETABS

Agree with BA this looks like a bug.

If you consider the rigid link then the beam section effectively stops at the column face but there would need to be an extra 15cm of column self weight to account for the extension from the node to the top of the section to complete the frame which accounts for their missing reaction from your hand calc.

The overlap in your SAP sketch is equivalent to the missed open corner so the weight of the missed area is accounted for.

My Personal Open Source Structural Applications:
https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:
https://github.com/open-struct-engineer

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

eBook - Functional Prototyping Using Metal 3D Printing
Functional prototypes are a key step in product development – they give engineers a chance to test new ideas and designs while also revealing how the product will stand up to real-world use. And when it comes to functional prototypes, 3D printing is rewriting the rules of what’s possible. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close