A Multidisciplinary Strategy for the Inspection of Historical Metallic Tie-Rods: The Milan Cathedral Case Study

Abstract

A reliable assessment of historical metallic tie-rods requires both the estimation of actual tensile load and the identification of dominant defects. Despite of high defectiveness resulting from traditional metalworking techniques, so far the latter aspect has not been duly addressed in the literature. In this paper, several methodologies are discussed aimed at integrating the usual inspection practice. All studies were performed on the tie-rods of Milan Cathedral.Metallurgical analyses allowed to recognize the main features of the material. Mechanical characterization in the perspective of Elasto-Plastic Fracture Mechanics (EPFM) indicated the conditions for crack propagation. Several Non-Destructive Techniques (NDTs) commonly used in Mechanical Engineering (i.e. guided waves, eddy currents, pulsed active thermography) were examined and adapted to this unconventional application. Based on the combination of all the mentioned methods, a multidisciplinary procedure was defined, which allows the evaluation of the crack significance with reference to the estimated working stress.

Digital Modelling and Analysis of Masonry Vaults

“…In both models, the iron tie rods are not inserted explicitly with the aim of studying the structure only under clear self-weigh and settlement effects. Further details on the behaviour of structures with iron tie rods can be found on Bellanova and Felicetti, 2019). In the simulations, the masonry web, the stone arch and the Figure 9.…”

A feasibility analysis on the application of eddy current testing to the detection of the most detrimental defects in historical metallic tie-rods

“…The analysis of the cracks causing the recent tie-rods replacement highlighted that both of them failed at straight scarf forged welds [13]. As demonstrated by proper mechanical characterization testing [14], the fracture toughness at the locations of such welds resulted to be one order of magnitude lower than the one of the base material.…”

Stress Evaluation in Axially Loaded Members of Masonry Buildings and Space Structures: From Traditional Methods to Combinations with Artificial Intelligence Approaches

“…Nevertheless, they have also been installed in buildings in subsequent phases, if it has been necessary to modify a structure (building aggregations, super elevations, etc. ), increase the load, substitute elements subjected to a heavy decay, or repair a building after an earthquake [10]. Still today, the insertion of tie-rods is one of the most widespread methods utilized to reinforce historical masonry buildings in seismic-prone areas.…”