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性很重要。尤其是风能，这是一种巨大的国内资源，具有改变美国能源经济的潜力。美国能源部将发展可再生能源列为国家的当务之急，并制定了到2030年美国20%的电力来自可再生能源的目标。要实现这一目标，风力发电技术的变革性进步显然至关重要。具体地说，风力涡轮机塔架必须制造得更高、更便宜。波士顿的一家初创公司开发了一种创新的制造技术，该技术基于自动螺旋焊接，使锥形细长的塔楼能够现场高效地生产。这样做的好处有两个：第一，与传统做法相比，自动化显著降低了生产成本，第二，现场制造排除了目前限制塔高的运输限制。这项技术应用的一个关键障碍是对这种特殊结构和细长壳体的屈曲失效缺乏基本的了解。现有的细长塔壳承载力预测方法不能令人满意，依赖过于保守的经验推导因素，没有可靠的概率基础，并且从未被应用于弯曲载荷下的螺旋焊管。为了充分利用焊接和制造的创新技术，需要新的基于可靠性的分析方法。本项目旨在对细长管的控制极限状态进行概率表征，并在此基础上发展一种严格的基于可靠性的分析和设计方法。该项目评估细长壳结构的强度、缺陷敏感性和可变性，并包括对以下鲜为人知的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；(2)焊接接头断裂/疲劳性能的可变性及其对板错位、焊接微观组织和韧性的空间相关性的依赖。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地探索制造方法和公差之间的成本效益权衡，以及在实践中利用的最终产能。

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.