How Cultural Divide can put Cultural Heritage at Risk

The seismic events that have damaged cities and towns in central Italy in recent years destroyed, or irreparably damaged, important examples of architecture. Behind several of these damages, it is known among experts in the sector that bad management of the safety interventions of the buildings must be recognized. Emblematic cases can be identified in the earthquakes that, between 1997 and 2017, struck the regions of Abruzzo and Umbria in Italy.

Image of the vault of the upper Basilica of St. Francis in Assisi, which collapsed after the 26th September 1997 earthquake. The use of reinforced concrete beams in the roof was suspected to be a possible cause of the collapse, in which four people died while carrying out an inspection to detect damage caused by the previous night’s shock. Image: Wikipedia

The replacement of wooden building elements or the execution of reinforcement interventions with reinforced concrete works, most of the times occurring to comply with the technical regulations, have created, during seismic stresses, disruptive effects on the ancient wall structures, leading to the disappearance of churches and buildings that had characterized urban or rural environments.

There are not many studies that have dealt with this issue, which is clearly related to the specific Italian context. Visions and approaches to the issue of building renovation are likely to collide.

On the one hand, the engineers who at the time had been asked to design the reinforcement interventions, can shift the responsibility onto the obligation to apply the building codes. On the other hand, the professionals who have the responsibility of conserving and protecting the historical heritage have not had the way or the competence to debate the validity of the technical choices in the field of anti-seismic reinforcement.

For example, the seismic repair and improvement interventions carried out in Italy in the periodi 1970-1980 on masonry buildings involved the construction, on the top of the load-bearing walls, of reinforced concrete curbs.

Many of these buildings, despite having been seismically adapted respecting the codes of those years on the seismic recovery of existing buildings, which provided for the replacement of wooden roofs and floors with reinforced concrete slabs, suffered partial collapses.

In fact, although the static function of the top curb is to absorb the vertical loads coming from the roof and distribute them evenly to the underlying walls, the weight and the excessive rigidity of the elements (beams and curbs) made between the floors or on the upper part of the walls transformed the curb into a beam that transmitted only on the end wall supports most of the weight of the roof weighing on it, and consequently leaving the central part of the underlying wall unloaded.

In this context, the interesting in-depth study “Architectural Heritage: A Discussion on Conservation and Safety” was published by Antonio Borri and Marco Corradi in the Journal of Cultural Heritage – February 2019.

Image taken from the the paper “Architectural Heritage: A Discussion on Conservation and Safety” describing the risk of unappropriate use of substitution of wooden beams with concrete beams in historic masonry buildings

The A. Borri – M. Corradi paper highlights the need to bridge the cultural divide between structural engineers, conservators, art historians, archeologists, and architects. In particular, engineers, in order to improve the seismic behaviour of masonry buildings, should be able to apply a conscious reinforcement based on the knowledge of the basic conservation notions.

To achieve this goal, however, engineers should be able to be relieved of the responsibility that the building code provides in case of incomplete application of its provisions. However, this aspect too is cultural in nature and must be addressed by involving the legislators as well.

Another important conclusion of the paper is related to the need of a consideration on the common approach adopted in the priorities on seismic interventions, which considers all cultural heritage buildings as equally important. Even if all cultural assets are equally important, the seismic risk to which they are exposed is not necessarily the same.

Therefore, the Authors suggest the opportunity to start an approach in which a preventive risk analysis following which the Authorities should establish the necessary funding according to an order of priority based on the actual risk.

This approach should allow us to overcome the common belief that “if a monument was constructed several hundred years ago, and it did not experience significant damage in the recent past, this does not imply that the risk is low: there is evidence of a large number of very old monuments having collapsed during the recent quakes.”

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