Abstract
We propose a method to infer the Green's functions (impulse response) of torsionally coupled shear buildings from array microtremor recordings on the basement and on an individual floor for the identification of mechanical and modal parameters as well as computation of seismic responses. Vibration of n multistory torsionally coupled building is modeled as n 3-input-3-output linear systems. The Green's tensor (Green's functions) is obtained by solving a simultaneous linear equation, where the coefficient matrix is composed of the correlations between input motions, two translational and one rotational motions, and the coefficient vector is composed of the correlations between the input and the output motions. We also propose a simple method to remove low-frequency noises from the Green's functions associated with input rotational motion. Applying the method to an existing building, we examine the reliability of the inferred Green tensor in time domain and in frequency domain. It results in that the three diagonal Green's functions are reliable ones but same off-diagonal Green's functions are slightly worse. However, the Green's tensor reproduces the observed microtremor recordings, indicating that the Green's tensor is reliable. This also indicates that the inferred Green's tensor is usable to indentify the parameters.
