elements

2D elements:

keyword	type	end node p	end node q	generalized deformation modes
`PLBEAM`	planar beam	x^p, Φ^p	x^q, Φ^q	ε₁,ε₂,ε₃
`PLTRUSS`	planar truss	x^p	x^q	ε₁

3D elements:

keyword	type	end node p	end node q	generalized deformation modes
`BEAM`	spatial beam	x^p, λ^p	x^q, λ^q	ε₁,ε₂,ε₃,ε₄,ε₅,ε₆
`TRUSS`	spatial truss	x^p	x^q	ε₁