engleski

Acoustic emission analysis and thermo-hygro-mechanical model for concrete exposed to fire

High performance concrete (HPC) is often used in tunnelling, for columns of high raise buildings and similar structures, which require high compressive strength. However, when exposed to high temperature (fire) there is a strong degradation of mechanical properties of HPC and it shows unfavourable behaviour i.e., explosive spalling of concrete cover. In the here described experiments the behaviour of normal strength concrete that was exposed to fire is monitored by acoustic emission (AE) technique. By the use of the AE technique damage processes in concrete can be observed during the entire fire history and therefore the detection of initialisation of explosive spalling can also be detected. The method makes possible to locate and characterize the micro-cracking before failure. The paper describes the proposed concept and preliminary results of fire experiments on concrete specimens made of normal strength concrete. To support experimental results it is also important to have a numerical model, which is able to realistically predict behaviour of concrete at high temperature. Therefore, in the paper is also briefly discussed fully coupled thermo-hygro-mechanical model for concrete that is implemented into a 3D finite element code. The application of the model is illustrated on one numerical example, which demonstrates that the pore pressure in combination with thermally induced stresses can lead to explosive spalling of concrete cover.

Acoustic emission; thermo-hygro-mechanical model; concrete; fire

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