Bridges are indispensable components of the infrastructure of modern society and their assessment via techniques of structural dynamics is assuming greater importance. This assessment concerns performance of the as-built structure compared to the design and can also extend to assessment of structural deterioration or damage. Simple validation of numerical results by dynamic testing has met some success, but feedback from testing into analysis is usually crude, and only recently have systematic techniques been developed that can be applied to such structures. This paper investigates the application of sensitivity-based model updating technology to the dynamic assessment of the Safti Link Bridge, a curved cablestayed bridge in Singapore. Based on the measured modal data from prototype testing, the simulated dynamic properties obtained via finite element analysis have been significantly improved by modification of uncertain structural parameters such as Young's modulus of concrete and structural geometry.
SUMMARYA statistical method with combined uncertain frequency and mode shape data for structural damage identiÿcation is proposed. By comparing the measured vibration data before damage or analytical ÿnite element model of the intact structure with those measured after damage, the ÿnite element model is updated so that its vibration characteristic changes are equal to the changes in the measured data as closely as possible. The e ects of uncertainties in both the measured vibration data and ÿnite element model are considered as random variables in model updating. The statistical variations of the updated ÿnite element model are derived with perturbation method and Monte Carlo technique. The probabilities of damage existence in the structural members are then deÿned. The proposed method is applied to a laboratory tested steel cantilever beam and frame structure. The results show that all the damages are identiÿed correctly with high probabilities of damage existence. Discussions are also made on the applicability of the method when no measurement data of intact structure are available.
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