Sustainable long-term use of timber structures - fire and post-fire deterministic and probabilistic solutions

In recent decades, environmental challenges have become increasingly important. In 2021, European Commission launched a European Green Deal strategy, with the main purpose to promote a circular economy with green technology, create a sustainable industry and transport, and reduce emissions and pollution. Among the industries that considerably contribute to degradation and climate change is undoubtedly civil engineering, which is still based on a heavy concrete and steel industry that causes many negative impacts (a large carbon footprint, large amounts of non-recyclable material, huge environmental degradation and other). Therefore, civil engineering needs a complete renovation, in line with the goals of the European Green Deal. The solution is offered in the more widespread and efficient use of wood as a building material which does not leave negative impacts typical of steel or concrete. When designing environmentally friendly and sustainable buildings, wood is almost indispensable material and often represents the whole or a large part of the load-bearing system. Thus, a challenge to better design timber buildings, in an efficient, economical, environmentally friendly, and sustainable way is always present and topical. A great challenge in ensuring sustainable timber structures represents the requirement for fire safety and fire resistance of the structure. In addition, for a sustainable and log-term use, it is also important to design a timber building so it can survive a fire event during its lifetime, while it can still be normally used after fire, without changing its load bearing elements. For this, the phenomena that take place during fire exposure as well as after fire exposure needs to be known. In terms of load-bearing capacity and stability, the moisture content has a significant impact on the long-term mechanical behaviour of timber elements. Particularly important can be the influence of high free water content, which can appear in wood as a result of extinguishing the fire. Since the problem of safety in fire and post-fire conditions is very complex, the key is merging experts of different disciplines and scientists with the introduction of innovative experimental methods and numerical models. The main objective of the project is to develop new advanced experimental methods for determining the physical, rheological and mechanical properties of structural timber and development of a new numerical models for predicting the long-term behaviour of timber structures in fire and post-fire conditions. For this purpose, to determine the fire resistance of timber structures, a new probabilistic heat-mass-pyrolysis model will be developed. This way, prediction of charring of structural timber exposed to natural fire will be possible, taking into account the random nature of fire and material properties. In addition, the heat-mass-pyrolysis model will be further developed to take into account the transfer of free water that may be present in wood due to the consequences of extinguishing process, and the temperature-dependent sorption hysteresis, which will be used to more accurately determine the drying of wood after a fire extinguishing event. To determine the rheological behaviour of timber structure in fire and post-fire conditions, a new mechanical model will be developed. Numerical modelling will be supported by advanced and innovative experimental methods to determine the necessary model parameters. Ambitiously, also new simplified design methods for long-term post-fire behaviour and for fire resistance of timber structures will be presented. This will make the project results directly and immediately applicable in practice. The results of the research will be relevant to several scientific fields and at the same time will represent a great socio-economic contribution, since newly developed numerical and experimental methods will enable the design of sustainable and environmentally friendly buildings.