Learning Forum

[Omobolaji Lawal]

Hi all,

I'm trying to match results from impacts on an experimental railroad bridge model. Currently the natural frequency of my ansys model (after replicating the dimensional properties of the bridge) is around 12 hz while the experimental model is 9 hz. I currently reduced the stiffness (through changing the young's modulus to 180 gpa). But also my displacement magnitude is like two times smaller than the experimental result. I need to reduce natural frequency - one way is to reduce stiffness but I don't know that I can realistically have a young's modulus lower than 180 gpa for steel. The other way will be to add mass but I think doing this will reduce the displacement magnitude. Also for some reason damping lower than 7% gives an error. But from their experimental result the damping seems high anyway. 

My question is how can I reduce the natural frequency and increase displacement at the same time (or how can I reduce stiffness knowing I can't probably reduce the young's modulus further).

[Sai Deogekar]

Hello, you might find the following video helpful: Simulation to Change the Frequencies | Ansys Courses