×
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

Crane loads - Slab On Grade

Crane loads - Slab On Grade

Crane loads - Slab On Grade

(OP)
I have a 5" thick 3.5ksi concrete slab.  The contractor wishes to load the slab with a crane used for lifting and placing panels.  The maximum outrigger applied load is 115k!! The crane sub insists this is ok if using 6ft x 6ft steel plates to spread out the load.  I figure this reduces the stress to about 22 psi if I assume a rigid plate.  At first glance this looks as though it will work, am I missing anything, should I be concerned about sub-grade reaction?  Any tips or insite would help.
Thanks,

thread507-189207: Slab on Grade - Crane Loads  

RE: Crane loads - Slab On Grade

Not knowing what other details you do not have about the concrete slab which appears rather thin and what may lay underneath this concrete pad, I would lay pantoons of at least 18"x18" by 12'long bolted side by side on which I then would place the suggested steel plates for the crane outrigger pads.  Also suggest you read Shapiro's "Crane and Derricks"; there is good material on outrigger pad support.  

RE: Crane loads - Slab On Grade

The plate will bend with 22 psi.  Thicken the dunnage to spread the load out to the perimeter of the plate.

RE: Crane loads - Slab On Grade

You need to consider shear and bending in the slab on grade--this is not just an issue of bearing stress.  Can the plate punch through the slab?  Will the reverse curvature of the slab outside of the plate cause cracking in the top of the slab?

DaveAtkins

RE: Crane loads - Slab On Grade

Check for tunnels, raceways, basements, etc under the concrete.  I have seen lightly loaded cranes punch through these unknown "holes"

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