Reinforcing a Composite Beam, that isn't quite Composite yet.

[trence76]

I have a project where the client is changing two bays of the structure from a typical office live load occupancy to an area being used for high density filing of 125psf. I'm not overly shocked by this. The problem is that the steel has already been fabricated and I now need to reinforce the steel girders. I can create extra capacity in the infill framing by adding a few extra beams to cut down their tributaries. However, for the girders, I am a little uncertain how to approach reinforcing the beams which (1) have already been fabricated and (2) how to account for the beams being of a composite nature.
In one case, I have a W30x90, composite beam, 3/4" camber, 40' span, and 30 studs. Would the process be determining the reinforced section properties and then going through the process of a composite design for the beam? Or is their a simpler method or spreadsheat for performing this type of analysis? Thanks for your help!

 

[delagina]

i have this excel for reinforced steel

 

[Lion06]

Is this a new structure that got changed late in the game?

 

[dcarr82775]

Have you looked at adding studs? Unless the girder is already erected it is easier to add studs or just use a different beam.

If you need to stick with what is there, just coverplate the bottom of the girder. Use the controlling element (stud, concrete, steel) to determine the amount of slab acting compositely with the girder, use the modular ratio to convert the concrete to steel then calculate the plastic neutral axis based on the concrete, steel beam, and bottom flange cover plate.