Cable force estimation of a long-span cable-stayed bridge with microwave interferometric radar

Since cables are the critical structural components for ensuring the overall structural integrity and safety of cable-stayed bridges, the portable and rapid cable force measurement has a very important practical significance in the bridge health monitoring. In this paper, a method of simultaneous and continuous estimation of the forces of multiple cables using a self-developed microwave interferometric radar was proposed. In the proposed approach, first, the time-varying modal frequencies are identified by the Hilbert transform algorithm from the displacements of multiple cables, which are monitored by the self-developed radar, and then, the time-varying cable forces are obtained by the vibration method. In addition, for the problem of multiple cables located in the same range bin when distance test or the test angle is nonideal, a single-channel blind source separation algorithm based on vibrational mode decomposition (VMD) and time-frequency analysis was proposed to separate the cable signals. Furthermore, a method based on the spectrum correlation coefficients was proposed to determine the number of decomposition layers in VMD. The "Nanjing Eye" cable-stayed footbridge was used to conduct field measurement to validate the proposed method. Field measurement results show a good agreement with reference measurements, which demonstrate that the proposed method can perform well in an actual project for portable and rapid cable force estimation.