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Article

GNSS (GPS) Monitoring of Dynamic Deflections of Bridges: Structural Constraints and Metrological Limitations

by
Stathis C. Stiros
Department of Civil Engineering, Patras University, 26500 Patras, Greece
Infrastructures 2021, 6(2), 23; https://doi.org/10.3390/infrastructures6020023
Submission received: 17 November 2020 / Revised: 15 January 2021 / Accepted: 19 January 2021 / Published: 3 February 2021

Abstract

The advent of modern geodetic satellite techniques (GNSS, including GPS) permitted to observe dynamic deflections of bridges, initially of long flexible ones, and more recently of short, essentially stiff bridges with modal frequencies > 1 Hz, and with small SNR (signal-to-noise ratio), even SNR < 1. This was an enormous progress, but not without problems. Apart from monitoring results consistent with structural models, experimental data and serviceability criteria, there exist some apparently unexplained cases of stiff bridges for which there have been claimed apparent dynamic deflections too large for common healthy structures. Summarizing previous experience, this article: (i) discusses structural constraints, experimental evidence, and serviceability limits of bridges as constraints to GNSS monitoring; (ii) examines a representative case of careful monitoring of a reinforced concrete road bridge with reported excessive dynamic deflections; and (iii) explains such deflections as a result of a double process generated by large reflective surfaces of passing vehicles near the antenna; first corruption/distortion of the satellite signal because of high-frequency dynamic multipath, and second, shadowing of some satellites; this last effect leads to a modified observations system and to instantaneously changed coordinates and deflections. In order to recognize and avoid such bias in GNSS monitoring, a strategy based on practical rules and structural constraints is presented.
Keywords: structural health monitoring; concrete bridge; GNSS/GPS; dynamic deflection/displacement; natural/modal frequency; serviceability limit; multipath; resonance structural health monitoring; concrete bridge; GNSS/GPS; dynamic deflection/displacement; natural/modal frequency; serviceability limit; multipath; resonance

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MDPI and ACS Style

Stiros, S.C. GNSS (GPS) Monitoring of Dynamic Deflections of Bridges: Structural Constraints and Metrological Limitations. Infrastructures 2021, 6, 23. https://doi.org/10.3390/infrastructures6020023

AMA Style

Stiros SC. GNSS (GPS) Monitoring of Dynamic Deflections of Bridges: Structural Constraints and Metrological Limitations. Infrastructures. 2021; 6(2):23. https://doi.org/10.3390/infrastructures6020023

Chicago/Turabian Style

Stiros, Stathis C. 2021. "GNSS (GPS) Monitoring of Dynamic Deflections of Bridges: Structural Constraints and Metrological Limitations" Infrastructures 6, no. 2: 23. https://doi.org/10.3390/infrastructures6020023

APA Style

Stiros, S. C. (2021). GNSS (GPS) Monitoring of Dynamic Deflections of Bridges: Structural Constraints and Metrological Limitations. Infrastructures, 6(2), 23. https://doi.org/10.3390/infrastructures6020023

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