Piled rafts under cyclic horizontal loading

在德国，桩筏的设计、尺寸确定、评估和施工均基于KPP-Richtlinie（DGGT 2001）。然而，KPP-Richtlinie中没有涉及循环荷载下桩筏的承载性能。总的来说，根据EA-Pfähle（DGGT 2012），关于承受循环荷载的桩的承载性能，只有有限的知识。基于DFG资助的研究项目“循环水平荷载下的桩群”，下一步将研究桩筏在循环水平荷载下的承载性能，例如在整体和半整体桥梁结构中由循环和温度相关约束引起的承载性能。在本项目范围内，将对地基进行小规模模型试验，以确定影响周期性水平荷载下桩筏承载性能的决定性参数。下面的调查与数值模型的基础上的有限元法（FEM）和验证的反分析选定的模型试验将被用来量化这些影响参数，并开发方法来估计承载性能的周期性加载桩筏。具体而言，应解决以下几个方面：垂直荷载如何影响水平桩阻力在基础内的分布？荷载循环次数、荷载类型（即单向或双向循环荷载）和荷载振幅的大小如何影响-基础内垂直和水平桩阻力的分布，-桩在垂直和水平荷载传递中的作用，以及-垂直和水平位移的累积？最终的目标是，然后开发的方法，允许从单调加载下的相应值，负载循环次数和负载幅度的上述参数的估计。

In Germany, the design, dimensioning, assessment and construction of piled rafts is based on the KPP-Richtlinie (DGGT 2001). However, the bearing behaviour of piled rafts under cyclic loading is not addressed in the KPP-Richtlinie. Overall, according to EA-Pfähle (DGGT 2012) there is only lim-ited knowledge available on the bearing behaviour of piles subjected to cyclic loading. Based on the DFG-funded research project "Pile groups under cyclic horizontal loading", the next step will therefore be to investigate the load-bearing behaviour of piled rafts under cyclic horizontal loading, such as those resulting from cyclic, temperature-related constraints in integral and semi-integral bridge structures. Within the scope of the project, small-scale model tests on foundations are to be carried out in order to identify the decisive parameters influencing the load-bearing behaviour of piled rafts under cyclic horizontal loading. The following investigations with a numerical model based on the finite element method (FEM) and verified by the back-analysis of selected model tests will be used to quantify these influencing parameters and to develop approaches for estimating the loadbearing behaviour of cyclically loaded piled rafts. In detail, the following aspects are to be addressed: How does the vertical load affect the distribution of the horizontal pile resistances within the foundation? How do the number of load cycles, the type of load, i.e. one-way- od two-way-cyclic loading, and the magnitude of the load amplitude affect - the distribution of vertical and horizontal pile resistances within the foundation, - the contribution of the piles in the vertical and horizontal load transfer, and - the accumulation of vertical and horizontal displacements? The ultimate goal is then to develop approaches that allow the estimation of the above-mentioned parameters from the corresponding value under monotonic loading, the number of load cycles and the load amplitude.