MDX GroupJ Question

[fulbright]

Hey all, just found this website after 6 years of bridge design. If only...

Quick question for you MDX users in here:

I'm investigating bracing forces in a curved plate grid analysis. I'm aware that the grid analysis model only considers the stiffness of the slab in the direction of the girders, but I want to account for the stiffness of the slab transversly also. My bracing layout is too complex for a plate and eccentric beam model, so I modified the model with additional "braces" with section properties representative of transverse strips of slab.

Here's my problem...GroupI is simply bt^3/12 for the strips, but can anyone recommend a formula for GroupJ - the torsional moment of inertia of the strip? J is imperical and depends on the aspect ratio of the strip.

Thank you!!!

 

[edward1]

I suggest you use the finite element option with MDX to get a complete superstructure design including the bracing. If you have questions about this call MDX and talk with them. I modelled several bridges with MDX and it is, in my opinion, the best steel girder software available for the price. The results were very close to using STAADPRO to model the entire superstructure.