The Demo Example number 9. Flexibility & Stiffness Matrix has an example of how to group elements to represent their structural behavior.

   

In general, it is very useful for large projects to reduce the size of the model and therefore the computational time.

   

In this case, it is for a very simplified beam-bridge-like structure including the modeling of the deep foundations. It includes all the data and a .pdf document explaining it.

         

Three variants are demonstrated:

• Complete structural system: with the superstructure, columns, and pile foundations
• Flexibility: pile foundations are substituted by a Flexibility element
• Stiffness: pile foundations are substituted by a Stiffness element