5003 Lectures - Faculty of Engineering and Applied Science

E5003 - Ship Structures I 155
© C.G. Daley
The structural stiffness matrix is just the sum of
the global versions of the member stiffness
matrices. Where two terms share a dof, the two
values are added. This is again reflecting the
simple idea of superposition in linear systems that
Hooke first saw.
Stiffness matrices are symmetrical. This is a
curious property, especially when you think about
the off-diagonal terms. Some of the terms refer to
forces per unit rotation and moments per unit
translation.
With the whole stiffness matrix assembled, we
have a single equation that relates all actions
(forces and moments) with all movements
(translation and rotations):