Verification of system identification utilizing shaking table tests of a full-scale 4-story steel building

Abstract

This paper verifies the feasibility of the proposed system identification methods by utilizing shaking table tests of a full-scale four-story steel building at E-Defense in Japan. The natural frequencies, damping ratios and modal shapes are evaluated by single-input-four-output ARX models. These modal parameters are prepared to identify the mass, damping and stiffness matrices when the objective structure is modelled as a four degrees of freedom (4DOF) linear shear building in each horizontal direction. The nonlinearity in stiffness is expressed as a Bouc-Wen hysteretic system when it is modelled as a 4DOF nonlinear shear building. The identified hysteretic curves of all stories are compared to the corresponding experimental results. The simple damage detection is implemented using single-input-single-output ARX models, which require only two measurements in each horizontal direction. The modal parameters are equivalent-linearly evaluated by the recursive Least Squares Method with a forgetting factor. When the structure is damaged, its natural frequencies decrease, and the corresponding damping ratios increase. The fluctuation of the identified modal properties is the indirect information for damage detection of the structure.