Multiscale modeling and model updating of a cable-stayed bridge. I: Modeling and influence line analysis

Structural health monitoring (SHM) systems have been installed in many long-span bridges to assess bridge performance and safety. However, the number of sensors in a SHM system is always limited; therefore, not all of the bridge components can be directly monitored. To facilitate an effective assessment of stress-related bridge performance and safety, a multiscale finite-element (FE) model with detailed geometry and affordable computation time is needed. This paper presents the details of establishing a multiscale model for the Stonecutters Bridge in Hong Kong, which is a cable-stayed bridge with a 1,018-m main span. The twin-box deck of the bridge is modeled with shell elements in detailed geometry such that all stress responses in the bridge deck can be directly computed; other bridge components are modeled using either beam or truss elements. Each segment of the girder is then condensed into a superelement with the substructuring method in order to reduce the number of degrees of freedom. A sensitivity-based model updating is also performed to update the multiscale model with the measured modal frequencies. The comparison between the simulation and test results shows that updating with only modal frequencies can ensure consistency in the dynamic properties between the model and the bridge. Nevertheless, the accuracy in the static displacements and stress responses from the influence line analysis may not be improved by the standard updating process. This indicates a need for multiscale updating techniques that take into account both the dynamic properties and local responses of the multiscale model.