Considering plastic properties when modeling with an Allowable Stress Design specifications. 1

[Mohamed Zied]

Hi,

I am conducting an analysis of a steel girder bridge. I have to check stresses to be smaller than the allowable value presented in the design code (JSHB 2012 Version). It is an Allowable Stress Design code which means that allowable stresses are a portion of the yield stress ( 50 to 60%).
I have some doubts about the results, and I am wondering if I should input the plastic properties of steel anyway.
If yes, what should I consider as plastic strains apart from the first one which is 0?

Thank you in advance

 

[FEA way]

Doesn’t the code specify which type of analysis should be performed ? Generally it is best to run nonlinear simulations in most cases (even when loads seem rather low) since they provide much more accurate results.

You can use bilinear elasto-plastic model, either with perfect plasticity (just one point in the table - yield stress vs 0 plastic strain) or with hardening (much better for convergence reasons, you specify two points / one like in previous case and then another one with UTS vs strain corresponding to this point).

 

[Mohamed Zied]

Thank you for your answer.

Do you recommend I input fail stresses for material?? If yes, does it mean the allowable stresses set by the code ??

 

[FEA way]

This option is meant specifically for fiber-reinforced composites modeled using plane stress formulation elements and linear elastic material. Check the documentation chapter "Plane stress orthotropic failure measures" for detailed description.