A dispersion-based methodology for the in situ assessment of bending stiffness in bridge cables

• Type: Article in International Conference Proceedings Book
• Date: 2020

Authors

Rodrigues, J (Author) Other; Caetano, E. (Author) FEUP; Santos, J (Author) Other

Conference proceedings International

Title: Proceedings of the International Conference on Structural Dynamic , EURODYN

Pages: 981-988

11th International Conference on Structural Dynamics, EURODYN 2020

23 November 2020 through 26 November 2020

Indexing

Scopus - 0 Citations

Other information

Authenticus ID: P-00T-CZ3

DOI: 10.47964/1120.9078.20084

Abstract (EN): The assessment of the structural integrity of bridge cables through the identification of axial force has a long tradition in engineering practice. Vibration-based methodologies usually involve fitting a set of measured natural frequencies to a force-frequency relationship, which may take into account the effects of sag-extensibility and non-negligible bending stiffness. However, the accuracy of the results is largely dependent on an adequate characterization of the boundary conditions, namely the effective length of vibration and the rotational restraints at the supports. Moreover, the identification of high-order modes (essential for attaining good estimates of the bending stiffness) may be hampered by the attenuation of small wavelength disturbances before reaching the cable ends, preventing the definition of standing waves. This paper presents a novel methodology for the identification of mechanical properties in bridge cables, which does not require any assumption about boundary conditions. Assuming that cables behave as Euler-Bernoulli or Timoshenko beams with a tensile force, analytical expressions for the dispersion relation of transverse waves are derived. As for experimental dispersion relations, they can be obtained by the computation of time-frequency distributions of the response at two different sections of the cable, permitting the identification of arrival times for each frequency component, and of the respective propagation velocities. The validation of this methodology is conducted on a stay cable from a footbridge, recording the response to an impact hammer excitation with two accelerometers. Mechanical properties are then identified through the fitting of the analytical expressions derived to the experimental dispersion curves. The obtained results for bending stiffness are consistent within a large diversity of experimental setups, regarding the location and type of the external excitation, and the distance between the sensors. This approach can thus provide in situ estimates of the flexural rigidity in bridge cables, unaffected by errors in the characterization of boundary conditions, which will prove useful in the local assessment of damage.

Language: English

Type (Professor's evaluation): Scientific