On algebraic equations of elastic trusses, frames and grillages

The algebraic equations of elastic frames are obtained by imposing natural constraints on the trial displacement fields. The obtained set of equations describe deformations of trusses, frames made of both compressible and incompressible bars, grillages of rigid joints as well as pin-jointed grillages. A new form of the set of algebraic equations of frames with a diagonal constitutive matrix is put forward. The presented approach is well-suited for educational purposes.