You will need advice from someone who can see the problem. I'm
not doing real well converting weights and measures. It sounds
like your building is 45' wide - I really doubt that this is a
clear span condition even in steel or concrete. What are the
joists made of? Do they really clear span 15 meters?
The load bearing you reference has to do with uniform loading of
1100 lbs on about 9 square feet or about 100# per SF which is very
high loading. Joists are usually designed to deflect l/360 or
about 1.5 inches at mid span, another reason to wonder about the
length and deflection limits.
Joists seldom fail catastrophically, they usually deflect an
unacceptable amount. IF you want to measure deflection use a
laser, string, or accurate measurement from the floor below at mid
span. I don't think a bead rolling will be accurate enough to
give you any information. If the joists are 45 feet and you are
concentrating a load at about 7.5 feet, you are least throwing the
load in the outer third - a safer plan than mid span.
As has already been said, the best advice would be a structural
engineer that can see the issues. You've not given nearly enough
information for anyone to make an intelligent guess.
Keep the whole world singing . . . .
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