The Soil Spring Generator is a convenient way to create soil-support under manually meshed Plate Elements or Auto-Meshed Areas. The generator will create compression-only springs with the stiffness based on the area of the plate elements and soil subgrade modulus.

Generating Soil Springs for Plates

Select the desired plate(s) and click the Structure | Generate Soil Springs command to create soil springs. Note: the plate elements do not need to be in the same plane as the spring supports are created perpendicular to each selected plate. In the soil Spring Generator dialog box, specify the subgrade modulus and the soil contact face. If the plates already have springs at the nodes, the Superposition Method (combine stiffness on existing springs or replace existing springs) and the Angle Tolerance will need to be set. The spring stiffness is calculated using the following formula: K_Spring = Subgrade Modulus * Plate Surface Area. The total spring stiffness, K_Spring, for the plate is distributed to the three or four plate element nodes based on tributary area. Note: Generated Soil Springs do not update automatically if the dimensions of a plate are changed.

Generating Soil Springs for Areas

Select the desired Area(s) and ensure that the Generate Plates feature is enabled in the Project Manager | Modify tab. Then, enable the Create Soil Springs option, specify the Subgrade Modulus, and adjust the Soil On Bottom parameter to define on which side (top or bottom) the springs should be created. The stiffness of each spring will be automatically adjusted if the area is modified or if the mesh is adjusted.