CSI software models bridge foundation systems by assigning foundation springs at the base of each column. Geotechnical analysis of soil conditions at the foundation yields stiffness and other spring attributes.
Users may model the foundation in greater detail by including piles, pile caps, and other components. This is done outside the bridge modeler using a mixed modeling approach. Some options for detailed foundation modeling include the following:
- Deep foundation system with pile group (option 1): Use frame elements to model piles and shell elements to model pile caps. For each pile, apply a fixed restraint at the point of fixity, and model only the portion between this point and the pile cap.
- Deep foundation system with pile group (option 2): Use frame elements to model piles and shell elements to model pile caps. Model the full length of each pile, assigning soil springs along pile length to simulate lateral soil support friction for vertical resistance. Nonlinear links, known as P-y springs, are available for modeling nonlinear soil resistance.
- Shallow spread footing: Use shell elements to model the footing. Apply linear or nonlinear links to simulate soil-structure interaction.
