8-15. A 
wide flange beam is used to support a
vertical force 
as shown in the figure. The
beam is 13-ft long and pinned connected at both of its ends. The modulus of
elasticity follows 
. Determine the distribution of
the critical buckling load. Also, determine the probability buckling. Assume
that E and P are independent.
(Ans. 
, 
)
