loads on floor hatches

huangyhg

loads on floor hatches
hi all,
i think i have asked this before.  i am looking for a formula to calculate safe loading on aluminum plate floor hatches to arrive at the plate thickness and the bearing area required on each of the four sides.  these hatches are subject to vehicular traffic of varying weights.
i do not have access to references such as rourke's
thanks in advance for any help.
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in the case of plates supported along fouir edges, the proportionate load carried by the short span is approximately:
    p = b^4/(a^4 + b^4)
p = porportionate load carried by short span
a = length of short span
b = length of long span
when b/a > 1.5 design as one way
best