Midas Civil boundary supports and links are the restraint, spring, link, rigid-connection, offset, and prescribed-displacement mechanisms used to represent support behavior and member connectivity.
How It Works
The manual distinguishes node boundary conditions and element boundary conditions. Nodal restraints fix or prescribe selected DOFs. Surface spring supports convert tributary area and ground reaction coefficients into nodal spring stiffness. Winkler springs let beam, plate, or solid foundation interfaces be modeled as distributed soil support. Elastic links connect two nodes for bearings, ground springs, or rigid-like behavior.
General Links are two-node, six-spring elements for damping devices, isolators, compression-only or tension-only behavior, plastic hinges, and ground springs. Rigid End Offsets and panel zones modify beam/tapered-beam connectivity and affect element stiffness, load conversion, self-weight length, and force-output positions. Rigid Links constrain relative geometry across selected DOFs or geometric subspaces.
Solver Development Notes
Boundary objects should be represented as assembly contributions or constraint equations with explicit DOF ownership.
Compression-only and tension-only supports introduce active-set or nonlinear constraint behavior.
Rigid offsets affect both stiffness and load-vector conversion, so they cannot be treated as output cosmetics.
Prescribed displacement on an otherwise free DOF must define the solver's internal constraint semantics.
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