×
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

Analysis of two way slab

Analysis of two way slab

Analysis of two way slab

(OP)
I need help with a two way slab problem. For some reason I just can't get started with this. I don't have much design and analysis experience and I need a starting point.
Here's the problem. We have a two story building and there is a machine that weighs 5 kip currently in the basement, but they want it moved to the first floor. I need to see if the floor in that area can hold this weight. The floor has an 8" slab with colums spaced at 20' c/c both ways. The colums are 22" square. Should I do a finite element analysis? If so, are there any good free ones available for download? Any help getting started with this is greatly appreciated, I seem to be over thinking this and confusing myself! Thanks!

RE: Analysis of two way slab

I think you should look at a concrete textbook (my favorite is Wang and Salmon's Reinforced Concrete Design) and read the chapter on design of two way floor systems.  Basically, there are two methods for design.  The first is an approximate method known as the Direct Design Method, and the second (which I prefer) is the Equivalent Frame Method.  The Equivalent Frame Method requires computer analysis, but not finite element analysis.  You basically design the two way slab as strips in each direction.

DaveAtkins

RE: Analysis of two way slab

I don't think you can use the DD method for anything other than uniformly distributed loads.  I couldn't find a similar requirement for the EF method, but take a look to be sure.

You should check out some books and start reading, and ask yourself do you really want to check a floor slab for a 5 kip machine load with freeware.  

RE: Analysis of two way slab

(OP)
Thanks for the help. I'm starting to read up on the EF method.
fuatornarli - I tried to access the slab design spreadsheet but it's not letting me, I can access other ones.

Also, that was a good point about the freeware, I just have access or the means to get a good program right now!

RE: Analysis of two way slab

You most definitely want to use the equivalent frame method in Chapter 13 of ACI 318.  This allows you to place concentrated loads on the slab in addition to uniform loads and analyze the floor.  

A finite element analysis could be done, but takes special care and knowledge to interpret the results without getting in trouble. - You could do both and compare results which would be good too.

RE: Analysis of two way slab

For this specific calculation case, computer modeling (with shell elements for slab and beam elements for columns) may give results (bending moments, etc) faster. We tend to have better feeling about the results from Equivalent Frame Method. But it is a simplified approach especially for the point load case and you still rely on computer for calculation. I used to use a DOS procedure to calculate flat plate with EFM. There might be some widespread-used software using EFM?

RE: Analysis of two way slab

There's a good design example in Nilsson and Winter's concrete textbook.

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