Nonlinear joint model updating of strong column-weak beam type frames based on instantaneous characteristics of the responses under earthquake excitations

In this article, a novel method based on the instantaneous frequencies and amplitudes of the principal response components is presented for nonlinear joint model updating. The instantaneous frequencies and amplitudes are first extracted by a low-pass filter with Hilbert transform. Then, limited point values of the extracted instantaneous frequencies and amplitudes are applied to represent the response of the nonlinear structure. Finally, an objective function based on the residuals of instantaneous frequencies and amplitudes between experimental structure and finite element model is established using the response surface method. The optimal values of the nonlinear joint model parameters are obtained by minimizing the objective function using simulated annealing algorithm. To verify the effectiveness of the proposed method, a three-story frame with bilinear moment–rotation relationship at the beam-column joints under earthquake excitations is simulated as a numerical example. The accuracy of the proposed nonlinear joint model updating procedure is quantified using the defined error indices. The effects of the selected data point number and the weight factors in the objective function are also discussed in the article. The results indicate that the proposed method can effectively update the nonlinear joint model with high accuracy even with noise effect.