On February 23, 2023, the inauguration ceremony of the equestrian monument to Giuseppe Garibaldi, located on Gianicolo Hill in Rome, took place following a delicate consolidation and restoration project designed by DELMAN Ingegneria.
The equestrian monument to Giuseppe Garibaldi, standing at the highest point of Gianicolo Hill, represents perhaps the most important commemorative site in Rome after the unification of Italy.
In 1849, the hill was the theater of the heroic defense of the short-lived Roman Republic against the French forces called by Pius IX to reconquer Rome. After the unification of Italy, Gianicolo Hill was transformed into a large public park and became a sort of memorial of the “Risorgimento.” The monument, whose design and construction were long and complex, was conceived in 1885 by Enrico Gallori and inaugurated on a highly symbolic date: September 20, 1895, marking the 25th anniversary of the liberation of Rome.
The consolidation became necessary following serious damage to the pedestal of the monument caused by a lightning strike during the night between September 6 and 7, 2018. The enormous energy released during the impact caused significant damage, mainly concentrated at the corner of the northwest side of the pedestal. In particular, several granite cladding slabs were displaced and rotated from their original positions. The slab on the west front, featuring the bas-relief of the lion, was partially expelled and crushed, while the bronze sculptural group on the west side of the base underwent slight displacement.
Damage to the granite cladding from the September 2018 lightning strike
Damage to the Baveno granite cladding slabs
The investigation using geo-radar (ground-penetrating radar) made it possible to identify the extent and location of the most damaged areas of the pedestal’s inner core. In particular, the most affected area was found to be the northwest corner and the west front of the pedestal, where the lightning caused the most evident damage.
The consolidation and safety project designed by DELMAN Ingegneria included:
– Removal of debris from the cracks.
– Repositioning of the granite cladding slabs that had shifted from their original positions.
– Consolidation through low-pressure injections of fluid cement mortar, aimed at restoring the original cohesion of the stone elements comprising the central core of the pedestal.
Outcome of the Geo-Radar Investigation: Survey of the internal core areas of the basement affected by lightning and identification of the injection points for fluid cement mortar.
The effectiveness of the consolidation intervention through cement mortar injections was subsequently verified by a second survey campaign using ground-penetrating radar. Comparison with a similar survey conducted prior to the commencement of the restoration works confirmed the high degree of consolidation achieved.
Slab with the bas-relief depicting the lion before and after the restoration
The monument, inaugurated in September 1895, had previously been affected by lightning strikes similar to the one in September 2018, occurring on two earlier occasions: in September 1944 and July 1963. Photographic documentation from those periods shows that the monument sustained damage very similar to that caused by the 2018 event, consistently concentrated on the west side of the pedestal.
Lightning strike 1963 – Detail of the upper edge of the Northwest corner and detail of the Southwest corner
Since it is not possible to rule out the recurrence of similar lightning events in the future, it was considered necessary to combine the consolidation and restoration work with safety measures against future strikes. For this reason, one of the tasks included in the assignment that DELMAN Ingegneria received from the Superintendence of Cultural Heritage of Rome was the design of a protection system for the monument against the risk of future lightning strikes.
The documentation underlying the tender issued by the contracting authority considered the installation of a steel tower over 35 meters high to support a lightning rod near the monument as a possible solution. However, when beginning the executive design phase of the lightning protection system, DELMAN Ingegneria concluded that a tower-supported lightning rod would have an excessive visual impact, inevitably altering the original and valuable landscape context of the surroundings.
Photo rendering of the lightning rod tower mentioned in the call for tenders
For this reason, DELMAN Ingegneria,after verifying its design feasibility,proposed an alternative system for protecting the monument: a Lightning Protection System (LPS) based on the principle of the Faraday cage. Named after its creator, the English physicist Michael Faraday, a Faraday cage consists of a metal enclosure that, when electrically charged, directs the charges to its external surface, thereby providing complete protection to the internal space, based on the principle of the Faraday cage, named after its creator, the English physicist Michael Faraday, a Faraday cage consists of a metal enclosure that, when electrically charged, directs the charges to its external surface, thereby providing complete protection to the internal space. After confirming that the thickness of the bronze monument was adequate, two stainless steel cables were connected vertically to the monument and fixed to the two base walls facing north and south. The vertical drops were then connected to the bronze sculptural groups located at a lower elevation of the base via two conducting rings placed at intermediate levels. Finally, the metal cable system was connected to a grounding ring positioned approximately 50 cm below the paved area surrounding the monument. Thanks to this solution, which was promptly approved by the Superintendence of Cultural Heritage, the monument and its pedestal are fully protected against future lightning events, without causing any visual impact on the monument or the surrounding landscape. It was an honor for DELMAN Ingegneria to be part of the team of professionals from the Superintendence of Cultural Heritage of Rome, who once again demonstrated an exceptional level of professionalism, as well as extensive historical-artistic and technical-scientific expertise.
Detail of the vertical drop of the new LPS system
