Experimental Investigations on the Temperature Increase of Ultra-High Performance Concrete under Fatigue Loading

Abstract

Leaner, more filigree, and resource-saving constructions are the development goal of the in the building industry. In reinforced concrete construction, a ultra-high strength concrete was developed to achieve these goals. Due to its use and requirements, this very pressure-resistant material is no longer only exposed to static loads. In applications such as wide-span bridges, machine foundations and wind turbines, the susceptibility to vibration is also significant. Research into the fatigue behavior of the new building material is therefore very important. In this article we will discuss the effect of heating up of high performance concretes under fatigue stress. The thesis is that warming up, which was already observed by several research groups, has an influence on the fatigue strength. Changes in the strength of the concrete or residual stresses generated by heating can lead to early failure. The aim is to find the reasons for the heating and the grade of influence on the fatigue strength. A systematic test program was developed to investigate the influencing parameters maximum stress level, frequency, and maximum grain size of the concrete. Thirty fatigue tests were carried out; the results will be presented here. The influence on the temperature increase as well as on the heating rate for the individual parameters will be discussed. The results show that all three discussed parameters have a significant influence on the temperature rise. Whereas the maximum temperature reached depends strongly on the frequency, the other two parameters mainly influence the heating rate.

Energetic damage analysis regarding the fatigue of concrete

“…Another hypothesis from Teichen 16 indicates that a major part of the dissipated energy E δ is transformed into thermal energy. This hypothesis was already confirmed in a previous paper 17 and is in accordance with the observed warming of concrete specimens during fatigue tests 2–10 . Also, the explanation from Whaley 18 and Chen et al, 19 that the friction and sliding processes between cracks and around the grains are responsible for the hysteresis and therefore for the dissipation energy E δ , supports this hypothesis.…”

“…Besides the analysis of the strain development and the degradation of stiffness during fatigue tests, the warming of the specimens was being on focused more in the past 2–10 . It was shown that specimens were heated up dependent on the stress amplitude, the maximum stress level and the loading frequency.…”

Einfluss der Druckfestigkeitsstreuung auf den Ermüdungswiderstand von druckschwellbeanspruchtem Beton

“…B. im Verbundforschungsvorhaben „WinConFat“ zeigen, dass es bei Ermüdungsversuchen mit üblichen Belastungsfrequenzen zwischen 1 Hz ≤ f P ≤ 10 Hz insbesondere auf Oberspannungsniveaus 0,75 ≥ S max ≥ 0,60 ( S min = 0,05) zu deutlichen Temperaturerhöhungen der Probekörper kommt [25–27]. Die Temperaturerhöhungen sind von verschiedenen Faktoren abhängig und bei hochfesten Betonen besonders stark ausgeprägt [28–31]. Diese entstehen durch die im Probekörper umgewandelte Dissipationsenergie [32, 33].…”

Heating rate with regard to temperature release of UHPC under cyclic compressive loading

“…In order to be able to reproduce a significant number of load changes in a short time, the loading speed is usually set high. In the case of HPC and UHPC; however, this leads to heating of the specimen, sometimes to the point of failure 2–10 . Because the samples fail earlier than the calculated expected values according to fib Model Code 2010, 11 special attention must be paid to heating.…”

“…In the project “Influence of load‐induced temperature fields on the fatigue behaviour of UHPC subjected to high frequency compression loading,” a comprehensive parameter study was therefore being carried out to understand which parameters have an influence on temperature development. The concrete strength, 3 the maximum grain size, 9 as well as the frequency and the upper 2,3,9 and the lower stress 3 were varied. In Reference 9, the heating rate was introduced as a possibility for a detailed analysis of the temperature development.…”