Beam Loading Question
I agree with acroduster and cessna on this. Assuming the beam carries all the load over the 28 by 30 foot floor above and is shared by the end bearing walls, you are near the stress limit at the 9 foot span. No worry there, there is factor of safety of 1.5 againts yield and the 100 lb/sq ft is the code value and conservative. But at 15.5 feet deflection approaches 1 inch which is near code limits, but more importantly stress is amplified as the square of span, or three times higher. You should check with the building inspector on this.