Displacement monitoring and multimodal frequency identification of long-span bridges utilizing PPP-RTK

Abstract Accurate displacement monitoring and precise identification of multimodal frequencies in large-span bridges are critical for ensuring structural safety and operational stability. Precise point positioning real-time kinematic (PPP-RTK), capable of delivering instantaneous centimeter-level positioning accuracy without reliance on nearby reference stations, has gained widespread application across various domains. This study investigates the feasibility and effectiveness of PPP-RTK for structural health monitoring (SHM) of long-span bridges in complex urban environments and proposes a robust approach for reliable multimodal frequency identification based on PPP-RTK-derived displacement time series. The performance of PPP-RTK was validated using three networks comprising 11 stations in Wuhan and its surrounding areas, where three representative models for generating local single-difference slant ionospheric and tropospheric delay products were systematically evaluated. The proposed methodology was subsequently applied to the Wuhan Yingwuzhou Yangtze River Bridge for SHM. Experimental results demonstrate that PPP-RTK achieves positioning accuracy and multimodal frequency identification capabilities comparable to those of RTK. Furthermore, the proposed frequency identification method exhibits exceptional performance in detecting the first six modal frequencies, showing remarkable consistency with reference values obtained from finite element method simulations and experimental calibration. Notably, the proposed method significantly outperforms conventional approaches in terms of accuracy and reliability. These findings underscore the potential of PPP-RTK as a viable alternative technology for SHM of long-span bridges, offering a promising solution for accurate displacement monitoring and structural frequency identification in complex urban settings.