Structural Steel Deck Design Using STAAD

[mssimplicity]

Hello folks,

I am doing some verification of structural steel frames. The steel frame is part of a deck. The deck has a 6mm plate which is welded above angle bars spaced at 600mm. The angle bars are then welded to an HEB400 beam. The HEB400 beam is extended so that part of it goes out of the deck as cantilever and supports some pipes. The loads from the pipes are quite heavy that it gives a high utilization (greater than allowable) to the HE400B if I do a simple elastic check. The simple elastic check gives large moments about the weak axis.

My concern is that can I consider that a portion of the HE400B is considered as deck, so that I can say that capacity of the member against bending is higher because there is a diaphragm effect (please correct me if this assumption is wrong)? I was also thinking of modelling the deck in STAAD and using "equivalent sections" to represent the plates welded to HE400B.

I would appreciate it if someone can give their two cents about this.

 

[JoshPlumSE]

I'm guessing that the 6mm plate is really just some checkerplate used as a walking surface. Is that correct? If so, those are usually connected to supporting members via occasionial spot welds, just enough to keep it fixed down. But, not something you can really trust to transfer large amounts of shear force to establish true strain compatibility at the beam-plate interface.

If it is well braced, then you should probably look at the plastic capacity of the beam, rather than the elastic capacity.... especially for weak axis bending of the beam where buckling is not usually an issue. I would do this long before I try to rely on the checker plate as a structural element.