Fatigue Analysis of Steel Plates due to AASHTO Live Loads

Hello,

I am currently working on a unique steel plate design to be used for a very minor lane widening on a bridge. This steel plate design is not an orthotropic steel bridge deck design.

However, AASHTO LRFD Bridge Specifications suggests for unique components and details that a refined analysis be used (but this complicates determination of force effects).

The model I have created is a Finite Element Model with fine plate element meshing around areas of concern (i.e. where plates and stiffeners meet).

I am currently doing a fatigue analysis due to live loads on the model, however I am having trouble understanding which stress outputs I should be using to calculate the fatigue stress range on my plate elements.

STAAD.Pro offers numerous stress type outputs: Max Absolute, Tresca, Von Mis, Membrane Stress (on local axises), Bending Stresses, and Shear Stresses (both in plane and out of plane).

Currently, based on the nominal stress approach, I am using the combined stress effects (membrane plus bending about local axises) to calculate the fatigue stress ranges. However, I wanted to make sure this was correct or if STAAD had a better way of determining fatigue evaluation.

Additionally, does STAAD.Pro treat connections between plates that are at an angle as welded joints? If so, does STAAD apply a stress concentration effect?

Thank you for your assistance.

Parents
  • Using the combined stress seems ok to me. Practicing engineers who are experts in fatigue analysis may have more inputs. In STAAD.Pro there are no options for evaluating fatigue. However based on the FE analysis you would be able to see if there are stress concentrations at certain locations. Stress concentrations happening due to geometric features like sharp corners, notches, openings, sharp edges etc are captured by the FE analysis.  



Reply
  • Using the combined stress seems ok to me. Practicing engineers who are experts in fatigue analysis may have more inputs. In STAAD.Pro there are no options for evaluating fatigue. However based on the FE analysis you would be able to see if there are stress concentrations at certain locations. Stress concentrations happening due to geometric features like sharp corners, notches, openings, sharp edges etc are captured by the FE analysis.  



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