Study of localized thermal damage of pressurized concrete in fire

Le résumé fourni par la source

Fire can cause thermal stresses within concrete, causing irreversible damage to structure, which in turn reduces load-bearing capacity of concrete. To better protect concrete, high-temperature simulation tests on various parts of axially loaded concrete specimens are required to assess their performance and degree of damage in a fire, allowing for development of more effective protective measures. This study experimentally gets real time high temperature stress–strain curves of concrete and then uses a particle flow code to build a model that matches macro and microstructural features of concrete. The software was used to simulate damage to each part of pressurized concrete specimen when it was fired on 1 or 4 sides. The results reveal that number of cracks created by both heating modes rises with rising temperature, as well as with decreasing simulation position. This number is 137 and 915 at the down part of concrete specimen (DC). The 4 sides heating mode reduces pressure-bearing capacity of specimens and subjects the substructure to greater stresses, with a stress difference of 25.54 MPa at DC. The 1 side heating mode, despite its low heat transfer, subjected the substructure to unequal stresses, resulting in a broad low-stress zone with a stress difference of 25.18 MPa at DC. The 1 side heating method causes concrete specimen to tilt towards heating surface, compromising overall safety of structure. So, DC location should be carefully shielded by thermal insulation, and prevented from forming specimens that could catch fire on one side. This study contributes to a better understanding of fire damage to concrete specimens and provides more precise theoretical guidance for concrete specimen protection, hence better protecting building safety.

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