Composite Deck design

[Imagineer]

Has anyone designed Composite Decks with STAAD? It seems they have two features (bugs?) to deal with them. The first is to include the additional options of concrete thickness and strength when selecting the steel beam in the member properties command. The other is to use specific composite deck parameters when doing an ASD code check. As usual, the manual, being one notch above useless, only gives the input specification without telling you what it really does or how it works.
Imagineer

 

[Imagineer]

Additionally, does anyone know if the Selfweight load command calculates the weight of concrete and the steel deck in a composite member?
Imagineer

 

[FredH]

When you assign the member property of a section to be composite, STAAD
assumes the concrete slab width of that section to be the width of the
flange of the steel section plus 16 times the thickness of the slab. The
selfweight of the member is hence based upon the weight of the steel section
plus the weight of the concrete slab.

 

[QAQC]

What??? This is incorrect. Design procedures that make assumptions of "effective" slab width for simplified analysis and design of composite behavior are NOT procedures for calculating loads on a structure. Not surprisingly, STAAD is wrong.......again.

 

I prefer to stand by STAAD. Before checking the ASD code remember to enter the slab width. And the concrete thickness is calculated automatically, depending on your structural assessment. The member property should be no more than 12 x the slab thickness. Any more will risk the structural integrity.

 

[lippie]

Actually, fredh is wrong. STAAD.Pro allows the user to input the slab width. If no width is provided, then the thicknesss is assumed width of the flange of the steel section plus 16 times the thickness of the slab

 

[globalasim]

lippie is quite correct STAAD.Pro has the provision of providing slab width.

 

[gb156]

STAAD.Pro 2001 does not correctly calculate the selfweight regardless of what one inputs as the effective width or concrete density. In short, do not use STAAD.Pro for composite beam design. Try it for yourself by modeling a simple beam with various effective widths.

 

They can send you an example problem which compares their answers with an example from Structural Steel Design by Jack McCormack. Looks OK to me. Why don't you try contacting them? They are pretty helpful in my opinion.