Abstract This paper presents a new approach for modelling the evolutionary power spectral density (EPSD) of thunderstorm outflows based on a database of 129 real-scale thunderstorm time-histories. Two equivalent methods of decomposition of the wind velocity are investigated, outlining the derivation of the EPSD. The analyses are based on the hypothesis that the residual turbulent fluctuations can be treated as a uniformly modulated process, whose reliability is verified studying the steadiness of its up-crossing rate. The assumption of considering a constant turbulence intensity is checked through the evaluation of the dynamic response of a set of SDOF systems in time-domain and through the response spectrum technique. Two models for the time-modulating function of the EPSD are proposed that include the parameters characteristic of both the thunderstorm event and the background wind. Finally, the steps for the derivation of the EPSD are outlined pointing out the limits of the representation of the PSD of the reduced turbulent fluctuations through spectral models commonly adopted in wind engineering. The final aim of this research is finalising a triad of complementary methods for evaluating the dynamic response of structures to thunderstorm outflows - EPSD, time-domain and response spectrum - consistent with real-scale time-history records.

中文翻译：

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与真实尺度时程记录一致的雷暴流出的演化功率谱密度模型

摘要 本文提出了一种基于 129 个真实尺度雷暴时间历史数据库的雷暴流出演化功率谱密度 (EPSD) 建模新方法。研究了两种等效的风速分解方法，概述了 EPSD 的推导。分析基于这样的假设，即残余湍流波动可以被视为一个均匀调制的过程，其可靠性通过研究其上交叉率的稳定性得到验证。通过在时域中评估一组单自由度系统的动态响应和通过响应谱技术，检查了考虑恒定湍流强度的假设。提出了两种 EPSD 时间调制函数模型，包括雷暴事件和背景风的参数特征。最后，概述了 EPSD 的推导步骤，指出了通过风工程中常用的谱模型来表示减少的湍流波动的 PSD 的限制。这项研究的最终目的是确定一种用于评估结构对雷暴流出的动态响应的补充方法——EPSD、时域和响应谱——与真实尺度的时间历史记录一致。概述了 EPSD 的推导步骤，指出了通过风工程中常用的谱模型来表示减少的湍流波动的 PSD 的限制。这项研究的最终目的是确定一种用于评估结构对雷暴流出的动态响应的补充方法——EPSD、时域和响应谱——与真实尺度的时间历史记录一致。概述了 EPSD 的推导步骤，指出了通过风工程中常用的谱模型来表示减少的湍流波动的 PSD 的限制。这项研究的最终目的是确定一种用于评估结构对雷暴流出的动态响应的补充方法——EPSD、时域和响应谱——与真实尺度的时间历史记录一致。