stress on a span

huangyhg

stress on a span
what would be a formula for finding stress on a platform suspended by the ends. i want to find out the load capacity in the middle of the span. i realize there are many variables. the platform span is 130' long by 20' wide and needs to support up to a 15000 lbs load at it's center. how would the platform need to be constucted and with what materials, or can someone give me specs based on aluminum steel etc.  
abjohnson, you are scaring us asking how do i.....  this is not a trival problem.  get a professional on board to help you design it.
the design process for a steel beams can be summarised as follows:
a) determination of all forces and moments on critical
            section with appropriate safety factors included
b) selection of ub or uc
c) classification of section
d) check shear strength; if unsatisfactory return to (b)
e) check bending capacity; if unsatisfactory return to (b)
f) check deflection; vertical deflection and
   lateral, if unsatisfactory return to (b)
g) check web bearing,unbraced length, flange ratio and  
   buckling at supports or concentrated load; if
   unsatisfactory provide web stiffener
h) check lateral torsional buckling; if unsatisfactory
          return to (b) or provide lateral restraints
i) design platform, add dead wieght go back to d
j) perform dynamic analysis
summarise results