Axial-Only Trusses¶

Choose Type = truss in the member inspector, bulk inspector, or Model Tables for an explicitly axial-only member. Truss ends are implicitly pinned; saved frame hinge settings are retained but ignored until switched back to frame. Dashed member lines and end circles distinguish trusses on the editing canvas. Materials and section area determine EA stiffness; Iy/Iz/J remain stored for switching back to a frame but do not affect the planar truss response. The adapter uses PyNite rotational end releases with strict joint-only loading to enforce this behavior in the XY model. Member point/distributed forces and moments are rejected on trusses, including when changing a loaded frame to truss. Move loads to nodes explicitly; there is no silent conversion. Splitting a straight truss bar creates a new joint that must be properly restrained or braced: an unbraced intermediate joint generally introduces a transverse mechanism. Mixed frame/truss structures are supported; a rigid frame connection at a shared joint retains its rotational DOF.

When every connected member end at a node without an RZ restraint or spring is hinged, the shared rotation has no stiffness. Analysis removes that unused rotation from the unknowns without restraining translations or transferring connection moments. Results show RZ as n/a for those joints, not a physical zero rotation. Individual member end rotations and deformations remain governed by the released beam. A net nodal MZ on such a joint is rejected for each analyzed combination unless a moment-resisting connection, rotational support restraint, or RZ spring is provided. Real translational mechanisms are not hidden by adding translational restraints.

Source: GUIDE.md. This manual follows the current repository; the published rc1 wheel has a smaller feature set.