Eliminate tension from a subsoil
When modelling 2D members it is possible to define a surface elastic foundation – subsoils – as a support for these elements. However, these subsoils have by default tension capabilities which means it might occur the subsoil gets under tension. Negative contact stresses (sigma_z) indicate tension in the subsoil (Main menu > Results > 2D members > Contact stresses).
Since this behaviour is not realistic, it is necessary to eliminate these values. This can be done by performing a nonlinear calculation for which the functionality ‘Support nonlinearity/basic soil spring’ is needed. This functionality can be activated within the functionalities tab ‘Nonlinearity’.
In order to perform a nonlinear calculation, it is necessary to create one or multiple nonlinear calculations. These combinations can be defined within Main menu > Libraries > Load cases, Combinations. When generating the results for the nonlinear calculation, the tension in the subsoil will be eliminated and the contact stresses will have a positive value which represents pressure.