Optimisation of Structures Excited by Wind under Consideration of Stochastic Actions and Various Limit States

由于大气边界层的影响，土木结构会暴露在复杂的风的作用下。细长的结构，如桥梁、塔楼和桅杆，可能容易因风引起的空气动力效应而引起显著的振动。与实际相关的现象是涡激振动、抖振和颤振。结构的气动性能主要受其几何形状的影响，这就提出了与计算流体力学模拟相联系的数学形状优化策略，作为改善其气动性能的一种手段。相关极限状态的选择以及效应和阻力参数的随机描述使基于可靠性的结构响应评估成为优化过程的目标。本项目旨在开发一种方法框架，用于在随机描述的各种极限状态的自然风场的影响下对结构响应进行稳健优化。为此，扩展了现有的基于准三维涡旋质点方法的数值模拟程序，扩展了湍流入流条件和流固耦合条件，以允许对相关影响进行高效的计算分析。具体地说，风场的随机参数将被重现，结构响应将根据极限状态进行分析，并行模拟将与优化策略相联系。此外，现有的基于现象的激励机制分析模型，如准静态气动力系数、涡脱落力幅值、斯特鲁哈尔数、斯堪兰导数和导纳函数，被用于提高优化的效率，并允许流体和结构的解耦。模拟和优化结果的验证和解释将通过风洞实验和包豪斯大学新的数字包豪斯实验室的可视化工具的使用来支持。总之，该项目将产生一种经过验证的方法，用于在基于极限状态的优化的背景下对暴露在自然风中的线状结构的风激励进行高效和并行的模拟。这也将与结构动力学中的类似问题相关。样本分析将被用来展示该方法在不同极限状态下改善气动性能的能力。

Civil structures are exposed to complex wind actions as a result of the effects in the atmospheric boundary layer. Slender structures such as bridges, towers and mastes may be prone to significant vibrations induced by the aerodynamic effects arising from the wind. Phenomena of practical relevance are vortex induced vibrations, buffeting and flutter.The aerodynamic behaviour of structures is influenced primarily by their geometry, which proposes mathematical shape optimisation strategies linked to computational fluid dynamics simulations as a means to improve their aerodynamic performance. The selection of relevant limit states and the stochastic description of effect and resistance parameters allow the reliability based assessment of the structural response as the target of the optimisation procedure.This project aims to develop a methodological framework for the robust optimisation of structural response under the effect of a stochastically described natural wind field in respect of various limit states. To this end, existing numerical simulation procedures based on the pseudo-threedimensional Vortex Particle Method with extensions for turbulent inflow conditions and fluid-structure coupling are extended to allow the computationally efficient analysis of the relevant effects. Specifically, the stochastic parameters of the wind field are to be reproduced, the structural response is to be analysed in respect of the limit states and the parallelised simulations are to be linked to the optimisation strategies.Additionally, existing models for a phenomena based analysis of the excitation mechanisms such as quasi-static aerodynamic force coefficients, force amplitudes of vortex shedding, Strouhal Number, Scanlan Derivatives and admittance functions are employed to increase the efficiency of the optimisation and to allow a de-coupling of the fluid and structural. The validation and interpretation of simulation and optimisation results will be supported by experiments in the wind tunnel and the use of visualisation tools in the new Digital Bauhaus Lab of Bauhaus University.In conclusion, the project will yield a validated method for the efficient and parallelised simulation of wind excitation of line-like structures exposed to natural wind in the context of a limit state based optimisation. This will also be relevant for similar problems in structural dynamics. Sample analyses will be used to showcase the ability of the method to improve aerodynamic performance in relation to various limit states.