Steel Plate Design

[teddyt11]

Hello

This is a pretty simple problem but just looking for some help.

I am designing a steel plate for a walkway. The plate is to be 3/8" thick A36 steel. The span is 27.5 inches by 32 inches.

I was wondering if someone could help me with finding the maximum deflection and then the load that the plate will be able to withstand?

Thanks so much!

 

[racookpe1978]

No.

Not with that little information. Is this a homework assignment?

What country?
What code of construction?
What safety factor, what loads, what environment? (Indoors, outdoors, walkway, gangway, ramp for a truck, grating in a power plant, sidewalk over a street, janitor access to a roof?)
What dead loads, live loads, construction or repair loads?
How big, how long, how wide? How is it supported on all sides? Is that a frame size or the plate size? Loose plates 27.5 x 32? Welded all around? How is it supported through the middle of the plate - or is it not to be supported at all?
Removeable walkway, welded, bolted, riveted to a frame or a long series of plates that are bolted down to a long frame? Laid down so they can be removed?

Think about what you are asking: It is equal to "I need to design a car. How big an engine do I need?"

 

[BadgerPE]

Depending on the level of analysis required you could look in Roark's Formulas for Stress and Strain or Blogett's Design of Welded Structures. Or if a simplified analysis is acceptable (and where I would probably start) is to just take an arbitrary strip width, 1" perhaps, in the short direction and back it into the strength and deflection calculations.

 

[teddyt11]

USA
AISC 360-10
Its indoors on a platform not sure the safety factor but i can apply that later

I am looking for the maximum deflection to be 0.1 inches.

With that I was looking to find the max allowable point load on the plate

The plate is supports on all 4 sides by a 4x4 angle with an opening between them being 27.5 inches wide and 32 inches long.
No supports for the middle of the plate

The plate will be welded. Sorry for being vague thought it would be ok with little information.

Hows that?

Thanks for helping

 

[KootK]

Got an AISC Manual? There's some handy tables in there for floor plate design.

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.

 

[jike]

I would use Roark to find a formula for a 2 way plate.

 

[ukbridge]

Look up "Pounder's plate theory" which gives simple methods for calculating deflections for one-way and two-way spanning plates. Again as said above be careful the connection actually provides continuity both ways if you assume it spans both directions!

Even more simply/conservatively calculate the Iy of the plate (ie treat it as a beam) and do a quick PL^3/48EI type analysis. For that type of plate more rigorous analysis is completely unnecessary apart from obviously developing your analytical skills.

I use mm, but I cant imagine anything over 6mm being required and even that will be absolutely fine for that deflection (i.e. L/275) under 5kPa pedestrian live load or whatever you're designing for. I wouldnt use anything thinner than 4mm as it'll warp when welded due to weld shrinkage. You need to be careful if maintenance vehicles etc can go over the plate which might affect your design somewhat!