Determination of the size effect on the spalling of concrete in case of fire

火灾时混凝土剥落尺寸效应的测定

• 批准号: 280066173
• 负责人: Dr.-Ing. Andreas Rogge
• 金额: --
• 依托单位: Abteilung 7: Bauwerkssicherheit
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/280066173?language=en
• 关键词: Determination; size; effect; spalling; concrete

Concrete structures have a high fire resistance which provides them with a more durable load-bearing capacity in the event of a fire compared to structures composed of other building materials. However, their surfaces can suddenly and violently spall which leads to a reduction of the cross section and therefore, a reduction of their load-bearing capacity. The most dangerous type of this phenomenon is explosive spalling which takes place in the first 30 minutes of a fire. Until today the exact mechanism behind explosive spalling remains incompletely understood, despite intensive research (e.g.: RILEM TC SPF) and a number of recently developed theories. The difficulty in researching explosive spalling derives from the large amount of possible variables leading to combined effects due to varying concrete technological properties as well as environmental factors. One decisive environmental factor for spalling is the geometry of a structural element and of the specimen used during a fire test, respectively.The primary objective of this project is to analyse specimens of different sizes to find a possible size effect of spalling. Six different concrete mixtures will be analysed in order to cover concrete-technological parameters as well. In preliminary tests we were able to show a correlation of the specimen size on spalling depth as well as high-temperature-related damage to a high-strength concrete mixture.The project will be sub-divided in order to investigate five main areas of interest. The aim of the first sub-project is to verify concrete technological properties and to determine the equilibrium moisture content of the selected concrete mixtures. The following three sub-projects reflect three different size levels: small-scale, semi full-scale, and full-scale level. These sub-projects each consist of four work packages which comprise specimen preparation, specimen description, fire tests and damage analysis. Herein, the quantitative determination of spalling by parameters such as spalling depth or spalling volume, and further, temperature-related damages are of main interest. For this investigation, the internal and external structure of each specimen needs to be determined before, during and after a fire test by suitable methods, including e.g. photogrammetry, acoustic emission analysis and computer tomography. The aim of the last sup-project involves the data analysis, correlating specimen size and spalling parameters for each concrete mixture. These correlations are intended for the development of a general size effect law for concrete spalling, taking into account the main concrete properties. The size effect law can serve as a basis for the implementation and establishment of a standard test method for spalling of concrete structures in case of fire.

混凝土结构具有很高的耐火性，与其他建筑材料组成的结构相比，在发生火灾时，混凝土结构具有更持久的承载能力。然而，它们的表面会突然剧烈地剥落，这导致横截面减小，从而降低它们的承载能力。这种现象最危险的类型是爆炸性剥落，发生在火灾的前30分钟。直到今天，爆炸剥落背后的确切机制仍然不完全清楚，尽管进行了深入的研究（例如：RILEM TC SPF）和一些最近开发的理论。研究爆炸剥落的困难来自于大量的可能变量，由于不同的混凝土工艺性能以及环境因素，导致组合效应。剥落的一个决定性环境因素是结构元件的几何形状和火灾试验中使用的试样的几何形状。本项目的主要目标是分析不同尺寸的试样，以找到可能的剥落尺寸效应。将分析六种不同的混凝土混合物，以涵盖混凝土技术参数。在初步测试中，我们能够显示出试样尺寸与剥落深度的相关性，以及与高强混凝土混合物高温相关的损伤。该项目将被细分，以调查五个主要领域。第一个分项目的目的是验证混凝土的技术性能，并确定所选混凝土混合物的平衡含水量。以下三个分项目反映了三个不同规模的水平：小规模、半全面和全面水平。这些分项目各由四个工作包组成，包括样品制备、样品说明、防火试验和损坏分析。在此，剥落的定量测定参数，如剥落深度或剥落体积，并进一步，温度相关的损害是主要的兴趣。为了进行这项调查，需要在防火试验之前、期间和之后，通过适当的方法，包括摄影测量、声发射分析和计算机断层扫描，确定每个试样的内部和外部结构。最后一个子项目的目的涉及数据分析，相关的试样尺寸和每种混凝土混合料的剥落参数。这些相关性的目的是发展的一般尺寸效应法混凝土剥落，考虑到主要的混凝土性能。尺寸效应定律可作为实施和建立火灾下混凝土结构剥落标准试验方法的依据。