×
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

Shear in Slab with Concentrated Load

Shear in Slab with Concentrated Load

Shear in Slab with Concentrated Load

(OP)
I have a situation where a two way slab supported by walls along each side is subject to a 16 kip vehicle load. When this load is close to the edge of the slab there is a high shear stress at the face of the support. Does the code address the width of the slab cross section that should be considered to resist shear? If I assume a 12-inch wide cross section I get a 20-inch  thick slab. 18-inch wide cross section I get a 14-inch thick slab, 24-inch wide cross section I get a 12-inch thick slab.

RE: Shear in Slab with Concentrated Load

Assuming a 12" square for punching shear, and depending on the strength of your concrete, it seems like something in the range of a 4" to 6" slab should be able to handle that.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Shear in Slab with Concentrated Load

(OP)
I would agree for punching shear.

I am checking the beam shear at the support wall.

Looking at it like a simply supported beam with a large concentrated load near the face of the support, would you not need to check the beam shear?

My question is what to assume for bw in 2XSQRT(f'c)XbwXd??
 

RE: Shear in Slab with Concentrated Load

Width for beam action shear (1-way) in a 2-way slab system should not be less than the column strip.  True for walls or columns.  However, for walls all 4 sides, beam shear will always be conservative.

RE: Shear in Slab with Concentrated Load

I would spread it out at a 45 degree line each side and check the shear on that width.

RE: Shear in Slab with Concentrated Load

(OP)
csd72,

"I would spread it out at a 45 degree line each side and check the shear on that width."

This is basically what I have done in the past. I was hoping someone could point me in the direction of a code requirement that backs it up.

ATSE,

I would not think the entire width of the wall could be considered. It would seem that the shear in the slab would be equal to the reaction that the slab is putting on the wall which would be much higher at the location of the load than 5 feet away.
 

RE: Shear in Slab with Concentrated Load

I did this problem using Westergaard's formula a while ago. The shear load as I recall was reduced by 55% close to the wall. If you have Ram Advanse you can model it as a shell or plate to verify this large reduction.  

RE: Shear in Slab with Concentrated Load


Check AASHTO design criteria.  This is similar to a bridge slab near the supports.  I believe the early criteria were 24"+some percentage of the span.

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