Axial Force Estimation in Historical Metal Tie-Rods: Methods, Influencing Parameters, and Laboratory Tests

This research focuses on estimating the axial force of historical metal tie-rods by means of non-destructive testing (NDT) which provides useful information for calibrating structural models. The first part of this work describes the behavior of tie-rods, emphasizing the key role played by cross-section stiffness, which is usually neglected in the case of cables. Particular attention is then given to common effective parameters and dynamic aspects in terms of acquiring the set-up and which modal parameters to examine. For new insights into methods for assessing historical tie-rods and evaluating the reliability of analytical and numerical predictions, laboratory tests on four samples with typical cross-sections were carried out on historical metal tie-rods. A set of 224 configurations, including various methods of excitation, boundary conditions, and stress states, were analyzed. In addition to laboratory parameters, this analysis also includes details of sensor positions and number of modes to be examined, and proposes a simplification for less time-consuming tests on-site.