Shear lag effect in shell element model

[HighPanda]

I am modelling a prestressed box girder bridge in a shell element model and believe the effect of shear lag should be automatically taken into account. However, as you may have expected, the longitudinal stress in the slab is not uniform and the stress in the deck around the webs is higher than that in the deck edges. Is there any simple rule or guidance I can follow to determine the width of slab where the stress is extracted to work out the force (and subsequently the amount of reinforcement) in the slab at SLS and ULS (if plastic redistribution considered)?

 

[graybeach]

I would use the AASHTO slab effective width criteria for composite design.