Cracking at the Unheated Side of a Tunnel during the Heating and Cooling Phase of a Fire Literature Study

Documents Literature study Report Acknowledgement picture front cover (fire Gotthard-Tunnel): Bild: KAPO UR Cracking at the unheated side of a tunnel during a heating and cooling phase of a fire Literature studyt Final report ARCADIS 3 Summary Part of the master thesis " Cracking at the unheated side of a tunnel during a heating and cooling phase of a fire " is this literature study in which subjects related to fire in a tunnel. Due to fire in a tunnel strains will develop in the concrete which will lead to crack formation. Restrained deformations give rise to cracks on the cold side of the tunnel. In order to assess durability in relation to this crack formation a correct model of the heating and cooling phase should be made. Eventually the question remains if these cracks can also be assessed in a simple manner without FE calculations. A few reports are discussed and the report of Nieman is taken as starting point for this thesis. The cooling phase is not yet modelled in his report but suggestions on the implementation of cooling are being made. Obtaining the required convergence was a problem and only 41 minutes of the fire curve could be calculated. In order to obtain convergence a smooth stress-strain curve should be applied. Several fire curves are mentioned but only the RABT curve addresses a cooling phase. However it is not known how this curve pertains to reality. The test results of the Runehamar tunnel also inhabit a cooling phase which is deviant from the RABT cooling phase. During heating and cooling the material parameters of both reinforcing steel and concrete will change. Reinforcing steel will lose strength which is regained during the cooling phase. The reinforcement will probably be reloading and unloading during the cooling phase so both branches should be modelled. Almost all material properties of concrete will decrease during heating. The compressive strength will decrease even further (20%) during cooling. To assess the stress-strain relation of concrete two main models will be discussed, total strain and decomposed strain model. The main disadvantage of the total strain model (f. i. the Eurocode model) is the reversibility of all strains during the cooling phase which is not according to reality. Due to the decomposition of the strain in the decomposed model every strain component can be treated independently and can reverse or not accordingly. One part of the …