A method for deriving structural influence coefficients from ground vibration tests.

A method is presented for finding the structural influence coefficients of an arbitrarily restrained system from the experimental results of an effectively free-free ground vibration test. A theoretical example is presented to illustrate the general procedure and to demonstrate the manner of convergence of the method. A discussion of nonorthogonality of measured modes is given, and a practical application is made to a delta wing specimen for which influence coefficients, modes, and frequencies have been measured, and the degree of correlation is discussed. Finally, a method for finding a complex influence coefficient matrix that includes structural damping is suggested for use in oscillatory aeroelastic analyses. Nomenclature