Composite Steel Beam Design

[ofthesea]

What is the recommended percentage of partial composite action for beams. It appears as if 25% is a minimum however I've been told that you should be between 40 and 80%.
Is there a guideline in the ASD manual?

These beams are unshored.

Thanks

 

[JAE]

I've usually stayed between 25% and 50%. As you increase your composite percentage, you will tend to have less stiff beams that will give you deflection/vibration concerns.

The cost effective balance depends on how much the labor costs are for welding on the studs as compared to the costs of steel beam weight. I've never seen an adequate study of this - perhaps others out there know of a good reference.

 

[Taro]

Lou Geschwinder (Penn State professor and AISC VP) gives a Practical Steel Design seminar that says economy is achieved with 50%-75% composite action. Also, the cost of one stud can be equated to ten pounds of steel.

 

[Bootman]

Check out the "steel tools" section of AISC's web site. There you will find a free spreadsheet called "Parametric Bay Studies 4.1". For a given bay size, the spreadsheet allows you to study the relative costs associated with various amounts of composite action. It also helps determine if cambering is economical.