“…According to this technique, the M th term approximate solution of (2), (8) is sought in the form (9) where ( ) i Q t are coordinates in modal space and ( ) i P x are the normal modes of vibration written as (10) No difficulty arises at all to show that for a beam with simply supported end conditions, taking into account equation (10), equation (9) can be written as (11) Substituting equation (11) into the governing equation (8), one obtains (12 ) which after some simplifications and rearrangements yields (13) To determine the expression for ( ) i Q t , the expression on the LHS of equation (13) is required to be orthogonal to the function . Thus, multiplying equation (13) by and integrating with respect to x from x=0 to x=L, leads to (14) where , , (16) and considering only the i th particle of the system, equation (14) can then be written as (17) where , and (18) To obtain the solution of the equation (17), it is subjected to a Laplace transform defined as (19) where s is the Laplace parameter. Applying the initial conditions (3), one obtains the simple algebraic equation given as In what follows, we seek to find the Laplace inversion of equation (21).…”