Let's say you have part of frame contacting the ground, such as the feet on the base of the tripod. Assuming each leg is equally spaced around a center post, how would you go about analyzing this type of structure? I'm trying to teach myself how to use the stiffness method, but all the examples I find are simple 2D beam structures. Would I use polar coordinates instead of Cartesian to represent the legs being equally spaced? How would the transformation of the stiffness matrix to global coordinates work if polar coordinates were used?