Notation

Coordinates

- symbols for coordinate axes:
$\bar x \quad$ member coordinate along the member axis from end 1 to end 2
$\bar y \quad$ member coordinate in member axes at the right angle to the member
$x \quad$ member coordinate in structure axes, usually horizontal
$y \quad$ member coordinate in structure axes, usually vertical

Forces

- symbols for force vectors:
$\mathbf{P} \quad$ Force vector:
$\mathbf{\bar{P}} \quad$ Force vector in member axes (not global);
$\mathbf{P} \quad$ Force vector in ``global'' axes (member axes in the global direction);
$\mathbf{P_s} \quad$ Structure force vector.

Displacements

- symbols for displacement vectors:
$\mathbf{\bar{u}} \quad$ Member displacement vector in member axes;
$\mathbf{u} \quad$ displacement vector in ``global'' axes (member axes in global direction);
$\mathbf{u_s} \quad$ Structure displacement vector.

Matrices

- symbols for matrices.
$\mathbf{X} \quad$     Matrix X
$\mathbf{X}^{T} \quad$ Matrix X transposed.
$\mathbf{X}^{-1} \quad$ Inverse of Matrix X.
$\bar{\mathbf{k}} \quad$     Member stiffness matrix in member axes.
$\mathbf{k} \quad$     Member stiffness in ``global'' axes.
$\mathbf{K_s}$ or simply $\mathbf{K}\quad$ Structure Stiffness