Need Rational Explanation for Plate Design
Need Rational Explanation for Plate Design
(OP)
On an existing structure, one of the levels has a framing which divides it into rectangles (beam center lines) 3'-0" by 12' 0". The framing is covered with a 3/8" deck plate (50 ksi steel) which is welded continuously to the beam flanges. The resulting plate is then divided into rectangles 2'-0" by 11'-0". On this deck a cart with 4 casters (8" diameter by 4" wide) carries a peice of equipment. Total weight of cart and equipment is 28 kips. Each caster carries 7 kips.
Analyzing this plate using Roak and also using Finite Elements gives bending stresses far in excess of yield and ultimate for the plate. Inspection of the existing plate does not give any appearance of distress, yielding or deflections.
I am designing a very similar structure and am unable to justify the 3/8" plate. Can any one give a rational explanation?
Thanks in advance.
Analyzing this plate using Roak and also using Finite Elements gives bending stresses far in excess of yield and ultimate for the plate. Inspection of the existing plate does not give any appearance of distress, yielding or deflections.
I am designing a very similar structure and am unable to justify the 3/8" plate. Can any one give a rational explanation?
Thanks in advance.






RE: Need Rational Explanation for Plate Design
Nigel Waterhouse
n_a_waterhouse@hotmail.com
A licensed aircraft mechanic and graduate engineer. Attended university in England and graduated in 1996. Currenty,living in British Columbia,Canada, working as a design engineer responsible for aircraft mods and STC's.
RE: Need Rational Explanation for Plate Design
Thanks for the suggestion. I did consider the plate fully fixed on all four sides. However, I did not consider the deflection of the supporting beams. I will try it.
Thanks again.
RE: Need Rational Explanation for Plate Design
RE: Need Rational Explanation for Plate Design
In the finite element analysis the loads were placed at several joints to simulate a line load of 4" (the width of the caster).
RE: Need Rational Explanation for Plate Design
Thin plates seem to act as though they were a series of interconnected cables, rather than a solid mass. The resulting catenary places more of a tension load on the end constraints than bending, as would be predicted by FEA, particularly if rotation of the top flange occurs in the direction of the load application.
RE: Need Rational Explanation for Plate Design
With the stress & deflection controlled the major condition we want to avoid is the "oil canning" of the deck. If the deck weight is not a concern, look to be concervative in deck design. The type of equipment loading the deck (dynamic loads) can become a problem.
Good Luck.