The external virtual work statement for an accelerating pipe element is given by:
(1)
where:
•
is the increment of external virtual work
•
is the distributed load vector in convected axes
•
is the mass per unit length of element
•
is the translational acceleration vector in convected axes, 
•
is the polar moment of inertia per unit length about element axis
•
is the angular acceleration about convected
axis
Substituting for displacements and accelerations in terms of nodal quantities and interpolation functions, in standard finite element fashion, gives the finite element form of
, namely:
where:
•
is the vector of equivalent nodal loads in convected axes
•
is the element mass matrix in convected axes
•
is the vector of nodal accelerations in convected axes