On the estimation of modal matrices with non-proportional damping

A method is presented for estimating the modal mass, stiffness and damping matrices of a linear non-proportionally damped structure. The method operates on the modal forcing and response time data of the structure following appropriated excitation. The system of equations can be constructed under the assumption of symmetric matrices which reduces the overall computation time, or with asymmetric matrices. The identified modal matrices are subsequently shown to reproduce time data with significantly less errors than if a 'modal damping model' is assumed.