×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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

Slab system vs Diaphragm
2

Slab system vs Diaphragm

Slab system vs Diaphragm

(OP)
Hello guys hope that you are doing well.

I have a question that might seem silly.

In concrete structures as I'm reading ACI we have two methods of designing for two way slabs:
Direct Design Method and Equivalent Frame Method. Now for example for the DDM it says that this is for gravity load design only. In what instance does this apply?

I am also approaching a chapter called Diaphragms.

What is the difference between a two way slab and a diaphragm? The entire chapter on two way slabs never mentions diaphragms.

Thank you very much in advance

RE: Slab system vs Diaphragm

Diaphragm is regarding the distribution of lateral forces to the resisting system (i.e. shear walls, moment frames, braced frames). The two way slab system will act as your diaphragm and you need to ensure it has the capacity to do so. Mostly that means ensuring the connections are capable of transferring the loads.

The reason the DDM example says it's for gravity load design only is because it's true. That method is only intended on the design of the slab for the gravity loading, it is not intended to be used to try and design the diaphragm actions of teh slab. Generally speaking, with two way slab designs, if it works for gravity, it will work for a diaphragm provided the appropriate attention to detailing is taken.

RE: Slab system vs Diaphragm

(OP)
Thank you very much Mr. Jayrod I really appreciate it. So just to clarify in the DDM or the equivalent frame method we come up with reinforcement in both North South and East and West directions. Based on what I understand this reinforcement is sufficient only for gravity loads. On the same slab that was designed based on the DDM method we must now add ASSIDTIONAL reinforcement so that it acts as a diaphragm and transfers that lateral forces.

Is my understanding from your comments correct?

Thank you soo much again.

RE: Slab system vs Diaphragm

Potentially you don't need to add additional reinforcement. Many times, the reinforcement required for gravity design can pull double duty for any requirements from the lateral design once you take into account the different load cases.

Sometimes you will need additional reinforcement to act as chord reinforcing or collectors. But often the standard bars that will be in your slab edge, and the typical connections from slab to lateral resisting system are enough.

RE: Slab system vs Diaphragm

(OP)
Thank you very much sir you are appreciated.

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

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. 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