grillage analysis of a composite beam of a bridge

[dada23]

Hey guys,

I would like to ask you how to model a concrete slab on two steel girders for a bridge in FEM software uaing grillage method ( i have GSA Oasys as software)? How to determine the section properties ( E, I, G and J) of the longitudinal elements representing the slabs and the steel girders? I think we need to calculate all section properties in ‘steel units’, using a transformed area for the concrete flange (divide by the modular ratio n) but i do not know how to calculate them. Can anyone help me please?

Daryl

 

[MotorCity]

You are correct that for composite design, you need to use the transformed area. Any reputable steel design book or google search will explain this. So if you only have 2 girders and a slab spanning between them, I would question the economics of using composite design since you don't have a slab on both sides of the beam. Also, I am not seeing how two girders provides any sort of grillage arrangement. FEM seems like overkill for this, use pencil and paper.

 

[dada23]

Thank you for your response.
I have found something on the grillage analysis

http://www.steelconstruction.info/Modelling_and_analysis_of_beam_bridges.

i need to define the modulus of elasticity and shear modulus of the longitudinal elements in FEM, so i need to find a way to calculate these properties for the composite action. While the transverse elements will only have the concrete properties.