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.

Jobs

Using excessive compression reinforcement to control long term deflection in RAPT

Using excessive compression reinforcement to control long term deflection in RAPT

(OP)
Hi Everyone,

I was wondering if anyone knows how does RAPT calculate the compressive reinforcement effect in calculating the long term deflection.

For a simply supported beam, if my Asc is 5 times x Ast, I could almost eliminate all the long term deflection.

However, based on AS3600, kcs=2-1.2Asc/ASt>0.8, which means I could only utilise 100% of Asc.

it seems that RAPT does not have a limit on the amount of compression reinforcement to be used in reducing long term deflection.

I know it is simply wrong to have a lot of compression reinforcements that you dont even need for strength.

i have also tried a simply supported beam without any load on it in rapt, and specifying 2 times more Asc than Ast,my beam just warped to the opposite direction .

I just want to make sure that the result from RAPT is convincing.

Thank you.

RE: Using excessive compression reinforcement to control long term deflection in RAPT

I suppose everyone is waiting for me to answer this one!

If you study long term deflection theory (not the code simplifications, the actual theory), you would be able to answer this for yourself. Even if you read the RAPT manual you would be able to figure it out. If you think RAPT is using the AS3600 kcs logic, you should read the manual to see how the program works before using it.

Yes, it is illogical to use 5 times as much compression reinforcement as tension reinforcement. But that logic is common sense, not calculation. By calculation, using extremely large areas of compression reinforcement could actually cause upward deflection due to the shrinkage warping effects. That is what RAPT's calculations are showing. It is not suggesting that the solution is sensible. It does not comment on the common sense aspect of a design. It shows the effect of what the designer has asked it to do. It assumes that engineers provide the common sense part of the design and understand the design methods it is using.

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!


Resources


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