×
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

Wheel loads on one-way slab: Moment in direction perpendicular to slab span

Wheel loads on one-way slab: Moment in direction perpendicular to slab span

Wheel loads on one-way slab: Moment in direction perpendicular to slab span

(OP)


Is there any formula for determining the moment in the direction perpendicular to the span of a multispan one-way reinforced concrete suspended slab 300 mm thick and spanning 2.5 m onto supporting steel beams, due to heavy concentrated wheel load(s)?

Even a formula for a single wheel load would be a start. Or would we need to do a SAFE run? I want to determine if the normal temperature steel is sufficient or need more than that. (Can forget the steel beam deflection effect for initial analysis, I just included that for completeness of description).

RE: Wheel loads on one-way slab: Moment in direction perpendicular to slab span

No need to run a computer program since that most likely will not give you a average over a certain width but instead will give you hotspots (which are not practical for use in design). This problem was solved long ago (in the 1930's) by Westergard for concentrated wheel loads on highway bridge slabs. I recommend using his report for design. It also gives you a methodology for combining effects for overlapping effects from multiple loads. It will also give you the required distribution steel (perpendicular to the main steel).

RE: Wheel loads on one-way slab: Moment in direction perpendicular to slab span

I suggest you get a copy of Westergaard's "Computation of Stresses in Bridge Slabs due to Wheel Loads" from your local library. This should be a reference that every structural engineer should have. Also, Spangler did some very helpful research at the University of Iowa on shear distribution in slabs due to concentrated loads.

RE: Wheel loads on one-way slab: Moment in direction perpendicular to slab span

If you've got a model set up and access to someone familiar with SAFE, I feel that would be as fast and accurate as anything else. Maybe faster and more accurate.

When I do this by hand, I use the method shown below from British codes. Given how common the situation is, I've always been surprised that CSA/ACI don't have anything. I guess I can't just rely on codes to do all my engineering for me! Most hand methods will result in your determining an effective flexural width in the direction perpendicular to the span. I'll proportion the reinforcement in that direction assuming that the span needs to span across the assumed effective flexural width as a simple span beam/slab member.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Wheel loads on one-way slab: Moment in direction perpendicular to slab span

AASHTO uses a similar method to what KootK describes -- determining an effective width and treating the span as one-way bending. Presumptively, for spans that meet the prescriptive requirements of AASHTO any longitudinal reinforcement is then adequate.

Also, Bridgebuster posted a link to the Westergaard article a while back in thread http://www.eng-tips.com/viewthread.cfm?qid=259491

RE: Wheel loads on one-way slab: Moment in direction perpendicular to slab span

(OP)
Thank you all for the helpful responses. I will have to study them and may have some follow-up questions.

To Kootk - yes we have people who are adept at SAFE and as you note that may be the best way to do it. But it would still be nice to have a manual check, and the material you and Lomaradil sent should help with that.

To Lomarandil - Can you help me to understand why you say that "Presumptively, for spans that meet the prescriptive requirements of AASHTO any longitudinal reinforcement is then adequate." I will have to study the AASHTO prescriptive requirements ...hopefully they have something about relating the longitudinal reinforcement requirements to the wheel load...do they? Also, one of my primary goals is to minimize cracking (and leakage at cracks) so it would seem to me that aspect could possibly require more longitudinal reinforcement than strength considerations alone. Do you agree?

Again thanks to all. I have some studying up to do, but any further comment would be welcome too

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