Site scale

In case of fire hazard, investigations aim at the definition of possible fire sources in the neighbouring of the considered heritage facility (focus of the analysis), and that can affect the heritage facility in direct (e.g. fire spread) or indirect (e.g. damage to other facilities which are structurally connected with the heritage facility) ways. In this sense, two main cases are of interest:

• - presence in the neighbouring of a special facility which is particular relevant as hazard source: fireworks factory, gas/oil station, refuelling station, etc. In this case, accidental events on one of these facilities can involve the heritage structure of interest. Spreads should be considered both for fires (primary) that for smokes (secondary), causing hazards for structural or non-structural (cultural values) damages respectively;
• - belonging of the focused heritage facility to buildings aggregates where other fire hazard sources are present. Our heritage facility can be part of a structural aggregate (very common in historical cities) together with other facilities/buildings (named here “aggregate facility”) which have some internal fire hazard source. As well-known, building aggregates are very complex from the structural point of view, and structural damages in a unit of the aggregate can affect the structural integrity of other units. Then, if the fire hazard and fire-induced damages affect the aggregate facility, with a consequent loss of structural integrity or global stiffness for the aggregate facility, the considered heritage facility can be also affected.

In both of the above mentioned cases, conducting a heuristic or a probabilistic analysis is almost impossible due to lack of information about sites and due to the low probability assigned to such evets. Then at the site scale the hazard analysis can be conducted by deterministic approaches: expert judgement has to be involved in defining a reduced number of worst-case scenarios (no occurrence is assigned) that has to be used in design. For the first of the above mentioned case (neighbour facility accident) the data which are needed for defining these design scenarios are:

• - location of the hazardous material/combustible inside the neighbour facility;
• - maximum temperature that can be reached by a fire in the neighbour facility;
• - maximum indoor fire duration in the neighbour facility;
• - fire security systems of the neighbour facility (e.g. splinkers)
• - possible presence of fired-missiles/debris in the neighbour facility;
• - resistance of neighbour-to--heritage barriers (side walls and roof covering of the neighbour facility) to blast of impact;  
• - distance of the neighbour facility from the focused heritage;
• - proximity of firefighters to the neighbour facility;

In the second of the above-mentioned cases (aggregate facility under fire), what is needed is:

• - data on structural fire resistance of the aggregate facility, in particular temperature capacity;
• - data about the mutual structural influence between aggregate and focused heritage facilities (e.g. common structural walls).