Research on Nondestructive Testing and Evaluation of Stiffness of Stone Arch Bridges Based on Modal Testing

In order to investigate the feasibility of a non-destructive testing method based on modal testing to assess the structural stiffness of ancient architectural bridges under environmental excitation, a 29 m span stone arch bridge was used as the research object, a virtual load test was designed based on the finite element model to determine the minimum modal order that meet the engineering accuracy requirements under symmetrical and eccentric load conditions; the vertical vibration information of the main girders of the stone arch bridge was collected under environmental excitation and the modal parameters were identified, and then the modal displacement flexibility matrix of the structure was identified; the modal deflection of the stone arch bridge under equivalent test load was predicted, compared with the design deflection of the finite element model, the deflection check factor was calculated, and the bridge stiffness condition was evaluated in conjunction with the current code. The results showed that the modal parameters of the stone arch bridge could be accurately identified based on the environmental excitation; the modal deflection predicted by the first two mode parameters could meet the engineering accuracy requirements under the symmetrical load condition and the first three mode parameters under the eccentric condition; the calculated mid-span deflection check coefficient was less than 1 under both conditions, which indicated that the actual condition of the bridge was better; modal testing, as a non-destructive testing method to replace load testing in evaluating the stiffness of ancient stone arch bridge structures, showed good engineering feasibility.