Piled rafts under cyclic horizontal loading

在德国，桩筏的设计、尺寸、评估和施工是基于kpp - richlinie （DGGT 2001）。然而，在kpp - richline中并没有涉及循环荷载下桩筏的承载行为。总体而言，根据EA-Pfähle (DGGT 2012)，只有有限的知识可用于在循环荷载下的桩的承载行为。基于dfg资助的研究项目“循环水平荷载下的桩群”，下一步将研究循环水平荷载下的桩筏承载行为，例如在整体和半整体桥梁结构中由循环、温度相关约束引起的荷载。在项目范围内，将对基础进行小规模模型试验，以确定在循环水平荷载下影响桩筏承载性能的决定性参数。以下基于有限元法（FEM）的数值模型的研究，并通过选定模型试验的反分析进行验证，将用于量化这些影响参数，并开发估计循环加载堆筏承载行为的方法。具体要解决以下几个方面的问题：竖向荷载如何影响基础内水平桩阻力的分布？荷载循环次数、荷载类型（即单向或双向循环荷载）和荷载幅值的大小如何影响基础内桩的竖向和水平阻力分布、桩在竖向和水平荷载传递中的贡献以及竖向和水平位移的累积？最终目标是开发方法，允许从单调加载下的相应值、加载周期数和加载幅值估计上述参数。

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.