Compression only Springs

[FM1]

I am trying to translate a long hand matrix analysis for a small portal frame , 2 columns , one beam across, into an excel/VBA. how could I model/include compression only spring for one of the column bases. that is if there is an upward load the spring wont be effective.

 

[kan123]

Can you use the =IF function in Excel? If this causes a self-referencing error, then you need 2 versions of the model -- one with the spring and one without. Then use the =IF at the end to select the correct answer based on the status of the force at that location.

 

[goncho]

If you want compression only springs you need to use an iterative process. And solve many consecutive matrixes.

You could set the springs as new members with a non-linear material with a normal young modulus in compression and a very small one for tension to avoid convergence problems.