This paper investigated the potential of using load cells installed on stay cables for the static and dynamic monitoring of cable-stayed bridges. This approach offers a promising alternative to traditional Structural Health Monitoring (SHM) strategies by reducing the number of sensors required on the deck, since load cells can effectively replace accelerometers in capturing the dynamic behaviour. The use of load cells measuring with a high sampling frequency serves a dual function: (i) monitoring axial forces in stay cables and (ii) enabling the identification of the deck modal properties through Operational Modal Analysis (OMA) techniques.

The conceptual basic of this strategy is firstly introduced, along with a discussion of the key issues related to the transformation of the identified modal forces in modal displacements. Then, a procedure for the optimal sensor placement (OSP) of load cells in stays is proposed, which allows obtaining the most effective sensor configuration minimizing the number of load cells.

The proposed methodology is validated by considering a real cable-stayed bridge located in Central Italy. The bridge has been equipped with a complete static and dynamic SHM system and data collected over a 2-year period are used to evaluate the effectiveness of the proposed strategy. The dynamics of the deck identified by using load cell recordings is compared with that identified through accelerometers installed over the deck, as well as with results of a comprehensive OMA performed during the proof load test of the bridge. Results are promising, demonstrating the potential of the proposed strategy.