Effects of tunnel-fire on load bearing capacity of tunnel-lining and surrounding rock mass. Part 2 (Sectional Calculation)

Dániel Csanády, Olivér Fenyvesi, Tamás Megyeri
2020 Építőanyag: Journal of Silicate Based and Composite Materials  
Vol. 72, No. 3  2020/3  építôanyag építôanyag  JSBCM JSBCM | 99 építôanyag építôanyag  Journal of Silicate Based and Composite Materials Alagúttüzek hatása az alagútfalazat és kôzetkörnyezet teherbírására 2. rész (vágatstatikai számítás) Effects of tunnel-fire on load bearing capacity of tunnel-lining and surrounding rock mass Part 2 (Sectional Calculation) cSanády Dániel  Budapesti Műszaki és Gazdaságtudományi Egyetem  csanady.daniel@epito.bme.hu fenyveSi Olivér  Budapesti Műszaki és
more » ... pesti Műszaki és Gazdaságtudományi Egyetem  Abstract The effect of tunnel-fire can cause significant changes in the strength of the tunnel-lining and its rock environment. This structural damage is a potential threat after fire load. The condition of the structure can be estimated if some concrete specimens exist from the mixture of the tunnel wall. These specimens should be loaded by the same temperature that affected the tunnel in fire during different heating and cooling treatments. According to the test results, the inner and outer part of the lining can be modelled under fire. The change of compressive strength and Young's modulus can be obtained from compressive strength tests. These processes were explained in details in our previous article, titled "Effects of tunnel-fire on load bearing capacity of tunnel-lining and surrounding rock mass". The ratios of the initial and instantaneous material properties give reduction factors. If the maximum temperature during a fire is known the overheating of the lining wall can be modelled by numerical methods, from which isothermal zones can be determined. From the thickness of these zones and the reduction factors (compressive-, tensile strength and Young's modulus) the present condition of the tunnel wall can be estimated by the model. The damaged wall can be modelled with a wall with equivalent stiffness to the damaged one with the use of the reduction factors. The created numerical model gives an opportunity for a fast structural evaluation of the tunnel after fire. This initial model was validated by comparison of model results from different software products tested with different boundary conditions. In present paper two software and three types of beamspring models (2D, 3D, node and surface support) were compared. All of these model types gave very close results, so it can be concluded, that they can be applied for tunnel modelling under increased temperatures without the further laboratory test of concrete specimens of the tunnel wall. Locations of partial failure (after fire) can be determined from the model which generates plastic hinges in the tunnel wall. In this step the model has to be recalculated to evaluate the final condition. From the different stresses and material properties of the wall the necessary provisional support system can be designed and constructed. This support system provides the required safety under the early stage of reconstruction. Besides this, the necessary thickness of reparation can also be estimated from the model results.
doi:10.14382/epitoanyag-jsbcm.2020.16 fatcat:2zuq6dtiafdkdpiuahwnsyy2sm