Noah's Ark Project: State of the Art in the field

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Effects on structures

Extensive severe damage, or even failures of historic structural elements, due to brittle materials can be explained only by fatigue due to repeated temperature and moisture action. This as yet uncompletely explained phenomenon has been uncovered by recent analyses on important historic buildings, and is theoretically based on variations in temperature and moisture gradients, and related uneven volumetric changes in historic structures. In this regard, the temperature and moisture differences and frequency of events are the decisive climate parameters, rather than the absolute values.

The extent of damage is deeply affected by current lack of knowledge on interrelated failure mechanisms, insufficient interdisciplinary and synergistic models, inadequate or even erroneous post-disaster measures concerning complex historic materials and structures. For example, the recent flood in the Czech Republic showed that many traditional solutions are ineffective, and are sometimes inadequately understood, lacking a proper scientific basis. The drying out of the historic fabric is far more complex than in modern buildings, as much of the fabric cannot and must not be replaced after water damage. The exact construction materials and the way they have been assembled is often not easy to identify, and the historic development of such buildings has meant that in the past the fabric interacted naturally with the environment, allowing moisture to be transported through the structure and evaporate from its surfaces. This phenomenon is sometimes referred to as a `breathing' construction.

The technology for drying buildings rapidly is now available. However, it requires evaluation for the built cultural heritage to determine the resulting stresses in the fabric: rapid drying could lead to irreversible distortion in materials, catastrophic failure, cryptocrystallisation within masonry and salt efflorescence [9-11]. Such effects should be compared with related damage when the fabric is dried slowly. Research is needed to identify the best methods of flood and damage management where flooding has occurred, and to establish the most appropriate drying strategy for the historic fabric. Cultural heritage materials are particularly vulnerable to accelerated decay when the environmental equilibrium is disturbed. Often, observed failures and damage can be interpreted wrongly by practitioners, because historic buildings exhibit unusual and unfamiliar features compared to typical design loads. The project aims to improve this situation through a deeper understanding of the behaviour and response of immovable cultural heritage and historic materials to the above mentioned effects, discovering possible endangering synergistic processes and providing cultural heritage managers, decision makers and legislators with scientifically sound data and models. However, some traditional materials and techniques may prove to be very efficient at mitigating disastrous events, and the project will also heed the lessons of traditional technologies, because of their great potential to improve employment and SMEs opportunities [12] .
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