This study investigated a number of different damage detection algorithms for structural health monitoring of a typical cable-stayed bridge. The Bayview Bridge, a cable-stayed bridge in Quincy, Illinois, was selected for the study. The focus was in comparing the viability of simplified techniques for practical applications. Accordingly, the numerical analysis involved development of a precise linear elastic finite element model (FEM) to simulate various structural health monitoring test scenarios with accelerometers. The Effective Independence Method was employed to locate the best distribution of the accelerometers along the length of the bridge. The simulated accelerometer data based on the FEM analysis was employed for the evaluation of the four damage identification methods investigated here. These methods included the Enhanced Coordinate Modal Assurance Criterion, Damage Index Method, Mode Shape Curvature Method, and Modal Flexibility Index Method. Some of these methods had been previously applied only to a number of specific bridges. However, the investigation here provides the relative merits and shortcomings of the damage detection methods in long-span cable-stayed bridges.
Brick masonry vaults for the approach structures of the Brooklyn Bridge were instrumented for remote monitoring. The objective of the project was to monitor and quantify safety of the structure, because of the longitudinal cracks at the crown of the double span vaults. A fiber optic sensor system was installed in the Brooklyn Bridge to monitor the crack opening displacements, wall rotations, temperature fluctuations, and vibrations. To quantify safety, a scaled model of the masonry vault was also tested in the laboratory in order to determine the failure crack opening displacement limits of the vaulted structure. Fiber optic crack sensors were mounted on the test vault to record the crack opening displacements under a range of base movements. Correlation of the in-service and failure crack opening displacements from the field measurements and laboratory tests provided the basis for the quantification of safety. This article provides a synopsis of activities to achieve these goals in terms of monitoring plans, instrumentation, and analysis of remote field data, laboratory experimental results and formulation of the safety assessment strategies.
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