SU.908 Finite elements for plates, shells and solids (linear static and modal), the engine behind slabs, shear walls and a solid stress check

Asked (#908: Abaqus, Ansys, SAP2000, STAAD.Pro, ETABS and others; #890 RFEM; #1057 SPACE GASS; #1141 SAP2000): finite elements beyond beams.

Built (lib/fem, own code, Apache-2.0): four-node shell (MITC4 or DKQ), ten-node tetrahedron, modal analysis, sparse IC(0)-PCG solver, slabs and shear walls through the frame mesher; known-answer tests with cited derivations (Navier, Lame, Timoshenko, Leissa, Blevins; 60 + 10 + 15 checks).
Reachable: the Analysis panel of BimCraft and DetailCraft, block 'Finite elements: natural frequencies': modes, period, effective modal mass, mode drawn on the model, member end releases and rigid floors carried, settings saved with the model, the report carries the table, help written. Deflections, reactions and plate moments of slabs and walls are shown by the frame solver in the same panel (lib/frame plates; lib/fem agrees with it to 1 % in tests).
Solid FEM: lib/fem's tet10 solid is the PartCraft add-on 'Solid FEM' with its own panel (SU.908c); PartCraft keeps its own solver (owner 2026-11-06). DKQ is a panel choice; the static solve in the panel stays lib/frame's (one engine, no second copy). Not built: nonlinear, contact, damping, response spectrum, soil models. No claim of equality with any other program.
Hand check: SU.908-HAND (big meshes and a real building on a workstation or by the community; not a blocker).

fem-complete 2026-11-06: docs/0.9-sessions/fem-09.md