Effects of turbulent wind on exposed flexible structures

当前的结构工程实践仍然广泛地依赖于静力分析方法进行设计。近年来引入的基于性能的设计方法仍然严重依赖于过去的方法，基本上接受传统的极限状态设计解决方案作为可接受的解决方案，而将安全和完整性问题留给设计人员来解释。大多数极端环境荷载对暴露的结构具有动力效应，在预测结构响应时，考虑失效或连续倒塌情景通常不能忽略这些动力效应。在结构抗震设计中得到广泛认可的是，真正的基于性能的设计是建立在可靠和相当准确的响应预测的基础上的，而简化的静力分析方法很难做到这一点。相当复杂形状的裸露结构上的风速分布和压力荷载很难预测，这解释了为什么直到最近，边界层风洞试验中的物理测试一直是评估复杂几何形状和部件结构上的风荷载的首选方法。现场风压监测也被用于重要的土木工程，世界上各种电力公司对架空线路导线进行了大量的试验研究，但可以说，在大多数现代规范和标准中，物理风洞试验结果是结构阻力计算的主要参考资料。本研究计划的目标是评估(并最终改进)各种实用规范和设计指南中描述的简化静载方法的准确性/充分性，以预测裸露结构对环境荷载效应的响应，如湍动风、大气结冰和风与冰的组合效应。加拿大的法规在这一过程中是有针对性的，例如加拿大国家建筑规范(NBC)-评论I风荷载和影响以及加拿大标准协会CSA S37中关于天线、塔架和天线支撑结构的法规，但其范围已扩大到包括国际OHL设计标准中使用的类似方法和裸露的交通标志结构。科学方法将结合对现有实验结果(来自风洞测试和/或监测，旧的和现代的)的批判性审查，以及使用结构动力学和流体动力学的先进计算力学技术。特别是，流体-结构的相互作用将被研究，在模拟真实的湍流风条件下，裸露的和结冰的柔性结构。该研究项目的影响和意义是深远的。研究的直接结果最终将导致NBC建议的更新(或确认)，这将对其他国家和国际设计实践产生影响。

Current structural engineering practice continues to rely extensively on static analysis methods for design. The performance-based design approach introduced in recent years still relies heavily on past methods, essentially accepting traditional limit-states design solutions as acceptable solutions, and leaving the issues of security and integrity to the interpretation of designers. Most extreme environmental loads have dynamic effects on exposed structures, and consideration of failure or progressive collapse scenarios cannot generally ignore those dynamic effects when predicting structural response. As widely acknowledged in seismic design of structures, true performance-based design is based on reliable and reasonably accurate response prediction that is rarely feasible with simplified static analysis methods. Wind velocity profiles and pressure loads on exposed structures of rather complex shapes are difficult to predict, which explains why until very recently physical testing in boundary-layer wind tunnel tests has been the preferred method to assess wind loads on structures of complex geometry and components. In situ wind pressure monitoring is also used on important civil projects and numerous experimental studies have been conducted on overhead line conductors by various electric utilities in the world, but it is fair to state that physical wind-tunnel testing results are the main reference material of drag force calculations on structures in most modern codes and standards. The goal of this research program is to assess the accuracy/adequacy of (and eventually improve) the simplified static load methods described in various codes of practice and design guidelines to predict the response of exposed structures to environmental load effects such as turbulent wind, atmospheric icing, and combined wind and ice effects. Canadian regulations are targeted in the process, such as those of the National Building Code of Canada (NBC) - Commentary I Wind Load and Effects and in Canadian Standards Association CSA S37 on Antennas, Towers and Antenna-supporting structures, but the scope is extended to encompass similar methods used in international OHL design standards and for exposed transportation signage structures. The scientific approach will combine a critical review of available experimental results (from wind-tunnel tests and/or monitoring, old and modern-era) and advanced computational mechanics techniques using structural dynamics and fluid dynamics. In particular, fluid-structure interactions will be examined, both for bare and iced flexible structures in simulated realistic turbulent wind conditions. The impact and significance of the research program are far reaching. The immediate results of the research will eventually lead to updating (or confirmation) of the NBC recommendations, which will impact on other national and international design practice.