A Method to Determine System Parameters of Sdof Structural Systems by Applying a Step Load

A novel method for identifying the physical parameters of structural systems has been proposed, unlike most existing methods are in terms of modal properties. Furthermore, the present method can be applied when structures are in services. The method is first theoretically derived by using single degree-of-freedom (sdof) systems, and will be generalized to multi-dof of lumped mass ones later. The present method requires a step external excitation, but the final expressions are independent of its input. Thus, it can be classified as an “output-only” method. In fact, it is the amplitudes of decaying spectrum, which is obtained by the so-called moving window Fourier transform (mwFT) from system signals is concerned, in addition to the steady-state deflection. Using the amplitude of this steady-state deflection, which can be obtained from the spectrum of the mwFT, as the quantity of calibration, the system parameters can be simultaneously estimated. The method is numerically verified by a model of bridge cranes.