How to model soil over concrete pier type supports (bell foot type) in order to report realistic supports loads/displacements in AutoPIPE?
There is no simple method to be able to model concrete pier type pile supports in AutoPIPE. Essentially, such types of foundation / supports are structural entities and a pipe stress program may not be the best option to model these. Here are 2 approximated approaches to consider implementing in an AutoPIPE model:
Use a general purpose finite element analysis program like ANSYS to model one such pile foundation with Winkler foundation / Soil supports applied. Determine the elastic translational and rotational stiffness values for the point at which the concrete pile gets connected to the structure / supported pipe. This can be done by applying a certain force value, determining the displacement value in that direction from the force and then calculating stiffness as K = F/X (or K = M/? for rotational stiffness). Once these stiffness values are determined, then a flexible joint (or a flexible anchor) can be inserted with these stiffness values. The other end of the flexible joint can then be connected to a rigid anchor.
Model your pier foundation in AutoPIPE similar to the one shown below. Apply equivalent soil stiffness values on each pipe member i.e. bearing capacity of the whole foundation base is distributed on to the pipe members. Apply soil properties for the vertical concrete pile. You can set the bell bottom members to rigid. For the concrete pile vertical member, you can supply equivalent stiffness values. This method is an approximation, and better the idealization and assignments of equivalent values, the closer the response would be to the actual structure response.
Different Types of Supports