GOALI/Collaborative Research: Enabling Advanced Wind Turbine Tower Manufacturing with Reliability-Based Design

可再生能源对国家的长期可持续发展至关重要。美国能源部将可再生能源的开发列为国家的迫切需要，并为美国设定了到2030年可再生能源发电量占美国总发电量20%的目标。为了实现这一目标，风能技术的变革性进步显然至关重要。具体地，风力涡轮机塔架必须制造得更高且更便宜。波士顿的一家初创公司开发了一种基于自动螺旋焊接的创新制造技术，该技术可以在现场高效生产锥形细长塔。这样做的好处有两个方面：首先，与传统实践相比，自动化大大降低了生产成本，其次，现场制造排除了目前限制塔高的运输限制。部署这项技术的一个关键障碍是缺乏对这种特殊结构的屈曲失效的基本认识，一般来说，对于细长壳，现有的方法来预测细长塔壳的能力是不令人满意的，依赖于过于保守的，经验得出的因素，没有一个坚实的概率基础，从来没有被应用到螺旋焊管弯曲加载。需要新的基于可靠性的分析方法，以充分利用焊接和制造的创新技术。本计画的目的是以机率的方式来描述细长管的控制极限状态，并在此基础上，发展出严格的可靠度分析与设计方法。该项目评估了细长壳体结构的强度、缺陷敏感性和可变性，并包括对以下现象的分析和实验研究：（1）局部屈曲的概率性质及其对随机缺陷的依赖性;（2）焊接连接的断裂/疲劳性能的可变性及其对板错位、焊缝微观结构和韧性空间相关性的依赖性。开发的分析和设计方法将与制造公差相结合，从而使制造商能够明确探索制造方法和公差与实际使用的最终容量之间的成本效益权衡。

Renewable energy is important to the long-term sustainability of the nation. In particular, wind energy, a vast domestic resource, has the potential to transform the energy economy of the U.S. The U.S. Department of Energy lists the development of renewable energy sources as an immediate national need, and has set a target for the U.S. to generate 20% of its electricity from renewable energy by 2030. To obtain this goal, it is clear that transformative advances in wind generated energy technology are crucial. Specifically, wind turbine towers must be manufactured taller and cheaper. A start-up company in Boston has developed an innovative manufacturing technology, based on automated spiral welding that enables conical, slender towers to be produced on-site in an efficient process. The benefits to this are two-fold: first, the automation reduces production costs dramatically compared to traditional practices and, second, the on-site fabrication precludes transport limits that currently inhibit tower height. A critical barrier to the deployment of this technology is a lack of fundamental understanding of the buckling failure for this particular structure and, generally, for slender shells.Existing methods to predict capacity of slender tower shells are unsatisfactory, relying on overly conservative, empirically derived factors, not having a firm probabilistic basis, and never having been applied to spiral welded pipe loaded in flexure. New reliability-based analysis approaches are needed to take full advantage of innovative technology of welding and manufacturing. This project aims to probabilistically characterize the controlling limit states of slender tubes and, based on this characterization, develop a rigorous reliability-based analysis and design approach. The project assesses the strength, imperfection sensitivity, and variability of slender shell structures and includes both analytical and experimental investigations of poorly understood phenomena of (1) the probabilistic nature of local buckling and its dependence on random imperfections and (2) the variability in fracture/fatigue performance of welded connections and its dependence on plate misalignment, weld microstructure and spatial correlation of toughness. The developed analysis and design method will be coupled with manufacturing tolerances, thus allowing manufacturers to explicitly explore the cost-benefit tradeoff between manufacturing methods and tolerances and the final capacities utilized in practice.