MDX Bracing

[PhredCutter]

Designing skewed, steel bridges using MDX. The diaphragm connection loads seem absurdly high. MDX assumes the diaphragm connection to the girder is fully fixed. So, as loads travel transverse to the bridge, the diaphragms transfer the loads. The LRFD version of AASHTO requires this for cases where the diaphragms are primary members: curved, severe skew, ect. I understand that I can remove or reduce the section properties of the diaphragms, but this would effectively remove the ability of the diaphrams to transfer loads. Does anyone else have methods to design the primary member diaphragms?

 

[VoyageofDiscovery]

How did you model your deck?

 

[PhredCutter]

MDX has plate elements for regular concentric beam model. However, this model has flared girders. So....there is no method for modeling the deck in this model. I've been working on ways to account for deck stiffness but am getting hung up on the assumption for effective width of the deck in the transverse direction.

 

[VoyageofDiscovery]

Model it in CAD, export in dxf, import into your software, account for all the slab though as this still permitted for refined method analysis.