**4.2 Sinusoidal Response**

Finding the response of a system to a harmonically fluctuating force usually involves finding the eigenvectors (see 4.1) and then using these to find a response.

It should be noted that the simple procedure in 4.1 is only applicable to systems of 4 or fewer degrees of freedon (d.o.f.). Solutions to systems with 5 or more d.o.f. require iterative methods.

It must be noteds that however the eigenvectors are found, their magnitudes are arbitary.

It is assumed that for a dynamic response the vector of displacements is a linear combination of the
eigenvectors.

David Grieve, 24th September 2012