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K. Savov, R. Lackner, H.A. Mang:
"Stability Assessment of Shallow Tunnels Subjected to Fire Load";
in: "CD-ROM Proceedings of the 7th International Conference on Computational Plasticity (COMPLAS 2003)", E. Onate, D.R.J. Owen (ed.); CIMNE, Barcelona, 2003, ISBN: 84-95999-22-6, 17 pages.

During recent fire accidents in European tunnels the concrete linings were damaged by spalling, leading to a reduction of the lining thickness of up to 50 %. In addition to spalling, thermal damage of the remaining part of the lining resulted in an increase of the compliance of the concrete lining. In tunnels with high overburden, the load-carrying capacity of the surrounding soil is activated by the increased compliance of the lining. In shallow tunnels, on the other hand, the soil as such may not be able to maintain the stability of the tunnel. In order to assess the stability of shallow tunnels when subjected to fire load, the "beam-spring" model is extended in this paper towards consideration of effects associated with high temperatures. At first, layered finite beam element are used for the discretization of the lining, allowing consideration of spalling by deactivation of layers. Secondly, the change of material properties in consequence of high temperatures is accounted for within elastoplastic material models employed for the description of the mechanical behavior of concrete and steel. Based on different spalling scenarios, an answer to the central question "whether or not spalling can cause collapse of shallow tunnels" is attempted by the application of the proposed analysis tool to a tunnel characterized by low overburden.

Keywords: tunnel, fire, fire accident, fire load, lining, concrete, reinforcement, spalling, safety, stability, collapse

http://aleph.ub.tuwien.ac.at/F?base=tuw01&func=find-c&ccl_term=AC04403095