Structural Identification by Processing Dynamic Macro Strain Measurements

In contrast to traditional modal identification methods processing structural accelerations for modal parameter identification, a multiple reference impact testing method using long-gauge fiber optical sensors and the related data processing approach are proposed. First, macro strains of key structural elements during the impact testing are measured through long-gauge fiber optic sensors, which subsequently are used to estimate the strain frequency response functions (FRFs) of the structure. Second, an approach is proposed to estimate strain mode shapes from the strain FRFs, and corresponding displacement mode shapes are calculated by applying an improved conjugate beam method. Finally, the strain flexibility character of the structure is identified by using the identified strain and displacement mode shapes with normalization. The advantage of long-gauge fiber optic sensors measuring averaged strains in a long length (e.g., 1 meter) provides the opportunity for strain modal analysis. The output of the proposed method, strain flexibility, is meaningful for static strain prediction and structural capacity evaluation. Examples investigated successfully verified the effectiveness of the proposed method for structural strain flexibility identification.