Numerical and experimental development of an “Accelerated Repeated Rolling Wheel Load Simulator” (ARROWS)

在考虑移动荷载的柔性路面的机械设计中，特别注意实现沥青层因拉应力引起的疲劳现象的真实描述。如果由此产生的外载荷超过了沥青的抗疲劳性，就会发生疲劳开裂。微观和宏观裂纹的萌生不仅与应力有关，而且与温度有关。然而，目前的实验装置显示应力状态和裂纹扩展机制与真实路面的存在有很大的不同。数值方法仅限于对潜在现象的单个组成部分的再现和描述，或者通常需要进一步发展才能得到适用的结果。因此，提出了一项研究项目，采用数值实验方法和真实再现沥青层在移动荷载作用下的加载条件。“加速重复滚动车轮载荷模拟器”（ARROWS）的数值和实验开发代表了研究项目的核心，旨在准确了解沥青层路面结构的使用寿命和疲劳敏感性。重点是在真实加载场景下实现裂纹形成和裂纹扩展的真实描述，包括大小，加载速度和加载级数。在联合研究项目的初始阶段，应提供数值验证（来自固定轮胎通道和开发的ARROWS测试设备的加载条件的模拟），并将各自的加载条件相互比较。同时，对试验装置进行了数值构想（设计细节、运行稳定性）。此外，该装置的实验概念将进一步发展。研究项目的重点是移动荷载作用下沥青混合料路面损伤和愈合现象的实验表征和数值表示。在此基础上，应开发一个数值模型，以便在大量加载周期和长测试持续时间的情况下进行长期预测。进行实验以确定模型参数，以精确描述沥青（材料和结构）的短期和长期行为。初步结构试验可对所选模拟方法对长期行为的预测质量进行评价；这是基于实时加速测试，通过构建一个缩放的ARROWS设备。最后，所获得的洞察力将被检查关于假设转移到一个未缩放的，全尺寸的箭头设备。

In the mechanistic design of flexible pavements under consideration of moving loads, particular attention is paid to achieving a realistic description of fatigue phenomena in asphalt layers due to tensile stresses. If the resulting external loading exceeds the fatigue resistance of the asphalt, fatigue cracking occurs. The initiation of micro and macro cracks is highly temperature dependant as well as stress dependant. However, current experimental setups exhibit stress states and mechanisms of crack propagation that differ strongly from those present in real pavements. Numerical approaches are limited to a reproduction and depiction of single components of the underlying phenomena or generally require further development to allow for applicable results. Therefore, the proposed research project a numerical-experimental approach and a realistic reproduction of loading conditions of asphalt layers under moving loads are pursued. The numerical and experimental development of an “Accelerated Repeated Rolling Wheel Load Simulator” (ARROWS) represents the core of the research project and aims to allow for accurate knowledge on the service life as well as the fatigue susceptibility of pavement structures with asphalt layers. The focus is on realising a realistic depiction of crack formation and crack propagation under real loading scenarios including magnitude, loading velocity and loading progressions.In the initial phase of the joint research project a numerical validation (simulation of the loading conditions from stationary tyre passes and due to the developed ARROWS testing device) shall be provided and the respective loading conditions are to be compared with one another. Simultaneously, the numerical conception of the testing device is carried out (design details, operative stability). Furthermore, the experimental conception of the device will be further developed. The focus of the research project is the experimental characterisation and the numerical representation of damage and healing phenomena of asphalt mixtures in pavements under moving loads. Based on this, a numerical model shall be developed to allow for long term predictions with a large number of loading cycles and long test durations. Experiments are conducted to identify the model parameters for a precise description of short-term and long-term behaviour of asphalt (material and structure). Initial structural tests allow for an evaluation of the prediction quality of the selected simulation approach for long-term behaviour; this is based on real-time accelerated testing by means of the construction of a scaled ARROWS device. Finally, the attained insight will be inspected with regard to transferability of assumptions to an unscaled, full-sized ARROWS device.