×
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!
  • Students Click Here

*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

Jobs

calculating rho prime for long-term deflections

calculating rho prime for long-term deflections

calculating rho prime for long-term deflections

(OP)
This might sound like a silly question, but I have to ask.  The question is which b to use when calc'ing rho prime in order to get the long term multiplier for long term concrete deflections.
Let's say you have a concrete T-beam with a flange width of 120" and a stem width of 36".  You will get a significantly different rho prime depending which b you use for As/(bd).
I have always used the flange width, but have never had such a big disparity before and needed so much compression steel to cut down the long term deflections so this is the first time I've thought this much about it.

RE: calculating rho prime for long-term deflections

I would go with flange width as well.  b it typicaly defined as the width of the compression face, which will primarily be the flange of the T in this case.   

RE: calculating rho prime for long-term deflections

I have to think that if you used 120" to compute short term deflections, then you need to use 120" for ρ'.  However, if using b=36" for short and long term deflections results in a lower long term deflection, then I'd use 36" for both.  Are you considering the longitudinal slab steel in your As'?   

RE: calculating rho prime for long-term deflections

ρ' is based on bd where b is the compression flange and this is taken at the midspan (by definitions from ACI 318).

So you'd use the 120" and the area of compression steel at midspan.

 

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