×
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

RC slab deflection check EC2

RC slab deflection check EC2

RC slab deflection check EC2

(OP)
hello everyone,

I have calculated the required reinforcement at the mid-span of the slab and trying to do the deflection check. At EC2-1 @ 7.4.2, i need to find ρ which is the required tension reinforcement ratio at mid-span to resist the moment due to the design loads.     Is it  ρ= As/(b*d) ?

RE: RC slab deflection check EC2

You've already found it, now you just need to use it.

Yes, ρ = As/(b*d), where As is the tension reinf't area

RE: RC slab deflection check EC2

(OP)
Thank you very much for the reply. Now the problem is that when I am calculating the maximum allowable  length/depth according to the chosen reinforcement area, is extremely high(40m length) and it is increasing as I am reducing the reinforcement area which is absurd.

RE: RC slab deflection check EC2

(OP)
As required= 263

As provided= 523

length of the slab =5200mm

depth = 175mm

effective depth= 130mm

RE: RC slab deflection check EC2

There is a design chart for deflections here:
http://www.concretecentre.com/PDF/5%20%20Slabs.pdf

that might be useful.

I presume that the span/depth ratio goes up for reducing steel on the basis that less steel indicates less bending moment, but that doesn't make much sense to me either, since they seem to be working on the basis of a reference stress, and similar sections with different moments and steel percentages, but equal steel stress will have similar curvatures.

What makes even less sense is that it seems to allow an infinite span/depth ratio if p = p'.

It might be worth contacting the Concrete Centre for their comment, but I'd recommend doing a proper deflection calculation, taking account of creep and shrinkage, anyway.

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
 

RE: RC slab deflection check EC2

I attended a presentation on this by the person you wrote the CC documents on EC2 a few years ago. His example was completely wrong at that stage. The basic result of the way he approached the calculations was that long term deflection is directly related to the steel percentage. This is absolute rubbish. Doubling the area of tension reinforcement does not halve the deflection as it did in his example.

I do not know if they have improved this paper since then.

Doug, I agree. Do it properly. Simplified L/D methods are a good way to end up in court!

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