Fiber section modelling of a twin girder bridge deck

[enrico tubaldi]

Dear Silvia,
i am trying to model a twin girder bridge deck section using a fiber model.
Do i need to define the concrete slab and the steel beams with respect to the center of the mass (which i don't exactly know) or can i define them with respect to a arbitrary reference system?I suppose the second alternative is the true since i used to different systems and i got the same answers under a load...In this case the section axial deformation i get is referred to the origin of my sistem or to the center of the mass?
Thank you very much in advance for the answer,
Enrico Tubaldi

[silvia]

i believe the axial deformation is of the origin of your section.
you should check that, with a simple example, though.