Apeiron Truss 2D FEM

The application can become a useful aid on the one hand for engineering students during their studies in checking hand calculations, solving trusses of large element number, or even in getting familiar with the basic steps of the finite element method (FEM); and on the other for practicing engineers in quick on-site verification of simple problems fitting into the realm of this highly confined family of structures.

The Apeiron Truss 2D FEM code implements the linear finite element method with linear truss elements for calculating planar truss structures of arbitrary geometry, material properties and loading. As such, only nodal loads are allowed, while supports - also specified at nodes - may involve both fixed hinges and rollers, this latter type nclines from the horizontal line at an angle specified by the user. The straight truss elements are exposed only to axial loading, hence only the axial stiffness constituents (Young modulus (E) and cross sectional area (A)) are to be prescribed.

After creating the geometry, the user can easily modify every feature of the structure (move a specific node, add or delete elements, supports, and loads or change the cross section characteristics). The results are listed textually for precise analysis and visualized as well for easier understanding of structural behavior.

The modelling steps are the followings:
1. Specify cross-sectional properties (elastic Young modulus and cross sectional area).
2. Prescribe the nodes constituting the structure.
3. Connect the appropriate nodes by line elements.
4. Apply loads on nodes.
5. Decrease the degrees of freedom by nodal supports (rollers are inclined at a user specified angle from the horizontal, fixed hinges are two non parallel, possibly perpendicular, rollers at the same node).
6. View the structure to check for any statical indeterminacy.
7. Solve the linear system.
8. View the results summarized in a list: nodal displacements, nodal loads, reaction forces and element axial forces.
9. Visualize the results. Deformed configuration, elements under tension (red) and compression (blue).