MKE-F capabilities
MKE-F is an educational program for linear finite element analysis of planar trusses and frames.
Elements, analyses, loads and supports
| Category | Capability | Truss element 112 | Frame element 113 |
|---|---|---|---|
| Elements | Structural model | Planar member: axial tension and compression. | Planar Euler–Bernoulli member: axial tension, compression and bending. |
| Elements | Nodal degrees of freedom | Two: translations ux, uy. | Three: translations ux, uy and rotation θz. |
| Elements | Element properties | Area A, Young’s modulus E, density ρ. | Area A, Young’s modulus E, density ρ, second moment of area I. |
| Analyses | Linear statics | Displacements, support reactions, axial forces, axial strains and stresses. | Displacements, rotations, support reactions, member end forces and N, V, M diagrams. |
| Analyses | Modal analysis | Undamped natural frequencies and mode shapes. | Undamped natural frequencies and mode shapes. |
| Analyses | Transient dynamics | Newmark method: displacement, velocity, acceleration and reaction histories; spectrum of a selected displacement. | Newmark method: displacement, velocity, acceleration and reaction histories; spectrum of a selected displacement. |
| Loads | Concentrated nodal forces | Global components Fx, Fy. | Global components Fx, Fy. |
| Loads | Concentrated nodal moment | Not supported: the node has no rotational degree of freedom. | Moment Mz about the axis perpendicular to the model plane. |
| Loads | Constant static load, type 10 | Nodal forces. | Nodal forces and moments. |
| Loads | Uniform distributed load, type 20 | Not supported. | Statics only: local or global components qx, qy; intensity per unit element length. |
| Loads | Harmonic load, type 11 | In dynamics: nodal forces following F(t) = F₀ sin(2πft). | In dynamics: sinusoidal nodal forces and moments. |
| Loads | One-step pulse, type 12 | In dynamics: nodal forces at the first time step t = Δt only. | In dynamics: nodal forces and moments at the first time step t = Δt only. |
| Loads | Step load, type 13 | In dynamics: constant nodal forces from t = 0. | In dynamics: constant nodal forces and moments from t = 0. |
| Loads | Combined loading | Loads are added if their types are supported by the selected analysis. | Loads are added; static analysis can combine nodal and distributed loads. |
| Supports | Type 1 — fully restrained node | ux = uy = 0. | Fixed support: ux = uy = θz = 0. |
| Supports | Type 2 — X translation allowed | uy = 0; ux is free. | uy = θz = 0; ux is free. |
| Supports | Type 3 — Y translation allowed | ux = 0; uy is free. | ux = θz = 0; uy is free. |
| Supports | Type 4 — both translations restrained | ux = uy = 0; equivalent to type 1. | Pinned support: ux = uy = 0; rotation θz is free. |
| Supports | Nonzero prescribed translations and rotations | Not supported. | Not supported. |
Notation and limitations
Notation: X and Y are the global in-plane axes; θz is nodal rotation; N is axial force; V is shear force; M is bending moment. A free degree of freedom means that the translation or rotation is not prescribed by a support and is determined by analysis; it does not imply motion without elastic resistance.
Load conventions: no loads are specified in modal analysis. In transient analysis, type 10 is also interpreted as a one-step pulse, not a constant load; use type 13 for a constant action. Self-weight is not added automatically.
Scope: types 112 and 113 cannot be mixed in one model. Analysis is linear, with small displacements and a linear elastic material. Plasticity, geometric nonlinearity and damping are not included; the frame element neglects shear deformation. Distributed loads must be uniform and are supported only on frame elements in static analysis. Frame supports of types 2 and 3 restrain rotation: they are not conventional roller supports.
See Input file format for input records and Boundary conditions and loads for sign and load conventions.
MPC
Seven frame support masks, three unique truss combinations and homogeneous linear MPCs are available in all three analyses. The editor, node-on-axis helper, separate SPC/MPC forces and v3 export are implemented. Mz end releases are available in all analyses with JSON v4. Nonzero prescribed displacements and the full NAFEMS investigation remain separate work.
Complete MPC guide · JSON v3 · CaseMPCFrame.txt · CaseMPCTruss.txt