Composite Beam/Deck

Question

Hi 
 
 I have the following technical question please could you help?

I wish to model a bridge deck, it is formed of:

longitudinal plate girders

transverse plate girders

with a uniform concrete deck which also over hangs the outer longitudinal beams

I am looking at building the deck as wide taper user members and plate elements, linking them over beam locations using the master slave function. 
 
 I undertook a simple sensitive to confirm this approach is ok, however the displacement I get is less than a comparable hand calculation. 
 
 Can you please advise on why there is this discrepancy? 
 
 Many thanks 
 170303 Comp Beam Test 4 - Plates TF.std

Sye · Answer

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.

Sye · Answer

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.

Sye · Answer

You can do a secure file upload following the process mentioned at the end of the following wiki 
 
 communities.bentley.com/.../28129.how-can-i-upload-files-in-the-bentley-communities-forum 
 
Please mention at which node you are checking the deflection and for which load case etc. and also attach your hand calculations if possible.