Composite Beam/Deck

When master slave is defined between the slab and the beam nodes, the center of the slab and the center of the beam are connected by rigid links. The fixity between the rigid link and the slab/beam would cause hogging moments to develop at the ends of the slab/beam even if you define the supports as pinned. Due to this, the deflections and span moments in the slab/beam system are going to be lesser than what you would get, if you do a hand calculation assuming a simply supported end condition.

Many thanks for the response Sye, that’s very informative.

This unfortunately causes me problems, how would you recommend that the following problem is best modelled:

I have composite beams (plate girders) that are continuous over numerous supports. The concrete slabs is connected between beams but also cantilevers past the beam centreline (as shown in the cross-section image above). Therefore I don’t think the composite deck function within Staad will work for the cantilever sections, thus why I selected plates with master slave nodes.

I do have a first draft model of the above case, should that is help you to understand my problem, although I would like to keep that private.

I welcome your thoughts.

Thanks again.

Many thanks for the response Sye, that’s very informative.

This unfortunately causes me problems, how would you recommend that the following problem is best modelled:

I have composite beams (plate girders) that are continuous over numerous supports. The concrete slabs is connected between beams but also cantilevers past the beam centreline (as shown in the cross-section image above). Therefore I don’t think the composite deck function within Staad will work for the cantilever sections, thus why I selected plates with master slave nodes.

I do have a first draft model of the above case, should that is help you to understand my problem, although I would like to keep that private.

I welcome your thoughts.

Thanks again.

Modeling the slab with a plate mesh and using rigid links to connect the centers of the plate/beams is an acceptable approach. Instead of actually going in and defining the master slaves at all of the corresponding slab/beam nodes, which could be time consuming, one may instead offset the beams with respect to the plate nodes, which would automatically create the rigid links. The composite deck feature does not account for projections and also it does not model the deck as such but accounts for the stiffness due to the deck by assigning a certain effective slab width to the appropriate beams.