This paper describes a method to find accurate mass and stiffness matrices in system identification. A set of
simultaneous linear equations is solved to identify the mass and stiffness matrix of structures. An exact solution
cannot necessarily be found because the coefficientmatrix in the equation is sometimes ill-conditioned. The singular-
value decomposition is used to find an approximate solution. The proposedmethod introduces the projected normas
an indicator to determine howmany singular values should be considered for identifying accuratemass and stiffness
matrices.Anumerical example is given to demonstrate that the proposedmethod is effective for systemidentification.
The system identification method was previously developed by the author and the contribution of the paper is a
method to select singular values. It is found that the proposed method identifies mass and stiffness matrices that