The structural strengthening of early and mid 20th century reinforced concrete diaphragms

During the 20th century it was very common in Italy to substitute masonry buildings' timber floors and roofs, which were considered inadequate, by reinforced concrete or reinforced clay diaphragms. Such interventions, especially if belonging to the early stage of reinforced concrete spreading, emphasize new conservation problems. Whereas on the one hand such structural elements are testimony of the construction practice of one era, a practice frequently not in use anymore, on the other they are also commonly inadequate to carry the loads currently specified by the building codes. Two such examples are to be found at Villa Borghese's Casino dell'Orologio, in Rome (Italy). One consists of reinforced clay unit beams, and the other of a thin ribbed reinforced concrete slab. The two have been strengthened in different ways as follows: 1) the first by replacing a few of the clay beams with reinforced concrete beams, 2) the second by adding an elastic support at the ribs' midspans. However, the intervention attitude is the same: preserving historical examples of construction techniques. Such attitude, as well as the structural calculation formulation, the construction details, and the approach when the knowledge of the existing structure is not complete are useful for other similar cases. © 2008 Taylor& Francis Group, London.