In the case you describe, I would say both are required to a certain degree.  The top flange channel addition would give you additional vertical stiffness and the channel/beam combination would allow greater spacing between lateral bracing (if needed) on the top flange.  This takes care of lateral torsional buckling.

You also have direct lateral forces to deal with for cranes.  With the crane suspended from the bottom flange, the lateral force required by AISC, for example, is 20% of the load, crane, trolley weights.  This comes in at the bottom flange and must be resolved through some kind of lateral bracing.  This is different, and in addition to, the lateral torsional buckling lateral forces.


The web of the wideflange cannot transfer this load from the bottom flange to the top flange as it has very little stiffness in that direction.

Okay, thanks for the input.  

From your question, I guess it is supposed to be a monorail which is unidirectional with lighter capacity. Since it is suspended from bottom flange of the beam at one location, it can be transferred through stiffners at that location and make a check for load transfer to its supports.
Cap channel will help you in case of top running cranes.

Kvram

1. Can anybody help in telling me how to design free standing Runway columns. What are the formulas used and what guidelines to follow?
We normally take 10% of the live load and the hoist wt and apply it to the top of runway column modeling it as a cantilever. Is this approach good. Any ideas?

2. Design of base plates for runway columns?
What if there is no pier or foundation and the floor is only 6" to 12" thick. How can i determine the size of the base plate for a runway column?

Thanks in advance