Specimen heating as damage indicator for fatigue tests of concrete

试样加热作为混凝土疲劳试验的损伤指标

• 批准号: 284163400
• 负责人: Professor Dr.-Ing. Ludger Lohaus
• 金额: --
• 依托单位: Institut für Baustoffe
• 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 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/284163400?language=en
• 关键词: Specimen; heating; damage; indicator; fatigue

High-strength flowable fine-grain concretes are commonly used in the wind energy industry, where they are exposed to high cyclic stresses. However, there are considerable uncertainties regarding their fatigue behaviour. Preliminary tests show signs of a significantly inconvenient fatigue behaviour com-pared to common high-strength concrete. However, it is so far not clear to what extent the observed differences in the fatigue behaviour are caused by material-technological or primarily technical testing influences. As a part of the preliminary tests, the heating of the test specimen during the fatigue load-ing was identified as a possible indicator of different fatigue behaviour. Increased testing frequencies and increased stress levels, which are significantly influencing the heating, are imperatively required in fatigue tests in order to examine the building life cycle in time-lapse experiments. The research project has several objectives. The focus here is to carry out fatigue tests so that the actual material behaviour can be determined. Concerning this, it is necessary to eliminate technical testing disturbance impacts, which may particularly arise from the increase in temperature of the spec-imens during the experiment. At the same time the fatigue tests should be carried out with the highest possible testing frequency in order to ensure as effective as possible test times. The heating of the test specimen due to the fatigue loading should be used as an indicator for undesired additionally possible damage and therefore as a control parameter for the experimental procedure. Firstly, the consequences of the specimen heating should be captured, parameters influencing the increase in temperature should be identified and initial indications of possible relationships between the respective concrete structure and the temperature development should be determined. The new testing method should be generalizable derived based on these studies and with the help of complementary numerical simulations of the temperature development and possible resulting damage mechanics. Thus, the capacity and the conciseness of statements derived from elaborately fatigue tests can be significantly improved, since only this way the actual occurring material-specific influences on the fatigue behaviour could be identified and pursued scientifically. At the same time, this approach shall clarify if fine-grain concretes in fact have a deviating fatigue behaviour compared to common concrete or not and according to this, whether fine-grain concretes can be designed and applied to the same rules as common concrete or elaborately fatigue verification has to be performed for each material. The research work is also of fundamental importance for future fatigue investigations on both normal concrete as well as on the further increasing variety of special high-performance concretes. Furthermore, they can help clear up existing discrepancies between various literature results.

高强度可流动细粒混凝土通常用于风能行业，在风能行业中，它们暴露于高循环应力。然而，关于它们的疲劳行为存在相当大的不确定性。初步试验表明，与普通高强度混凝土相比，其疲劳性能明显不佳。然而，目前尚不清楚所观察到的疲劳性能差异在多大程度上是由材料技术或主要是技术测试影响造成的。作为初步试验的一部分，疲劳加载期间试样的加热被确定为不同疲劳行为的可能指标。增加测试频率和增加应力水平，这是显着影响加热，在疲劳测试中是必要的，以检查建筑物的寿命周期在延时实验。该研究项目有几个目标。这里的重点是进行疲劳测试，以便确定实际的材料性能。关于这一点，有必要消除技术测试干扰影响，特别是在实验过程中样品温度升高可能引起的干扰影响。同时，应尽可能以最高的测试频率进行疲劳测试，以确保尽可能有效的测试时间。由于疲劳载荷引起的试样加热应用作不希望的额外可能损坏的指标，因此作为实验程序的控制参数。首先，应捕获试样加热的后果，应确定影响温度升高的参数，并确定相应混凝土结构与温度发展之间可能关系的初始指示。新的测试方法应该是推广的基础上，这些研究和辅助的温度发展和可能产生的损伤力学的数值模拟。因此，从精心疲劳试验中得出的陈述的能力和简洁性可以得到显著提高，因为只有这样才能科学地识别和追求实际发生的材料对疲劳行为的影响。同时，该方法应阐明细颗粒混凝土与普通混凝土相比是否实际上具有偏离的疲劳性能，并根据这一点，细颗粒混凝土是否可以设计并应用于与普通混凝土相同的规则，或者必须对每种材料进行详细的疲劳验证。这项研究工作也是至关重要的未来疲劳调查正常混凝土以及进一步增加各种特殊的高性能混凝土。此外，它们可以帮助消除各种文献结果之间存在的差异。