Mechanical performance of historical wrought iron rods

Historical masonry buildings are often reinforced with ferrous tie rods. Before the late 18th century, such rods were hot formed by using wrought iron deriving from either the bloomery or the finery process; thereafter, the puddling process was introduced and gradually became prevalent. Several such tie rods are still in service in cultural-heritage buildings; their analysis can shed light on historical production processes and building techniques, and knowledge of their mechanical performance can be valuable for architectural conservation purposes. Four steel tie rods, which were retrieved from a 17th century masonry building in Turin, Italy, and are dated to the late 17th and early 19th centuries, are examined here, by means of chemical and microstructural analyses, tensile tests and fractographic examinations, and both the material fabrication procedure and its mechanical performance are discussed.