关于水利工程风速统计方法的讨论和建议

Discussion on wind speed statistical method in hydro-engineering

由于风和波浪在与建筑物正向夹角45°范围内变化时,其作用效应变化不大,现行《海堤工程设计规范》中规定的用8个方位角统计风速的方法,使各方位角的均值偏小,导致设计风速偏小,以此设计的工程安全度严重不足.建议在未能提供可靠的、新的统计分析成果前,为安全起见,工程设计宜仍采用不分方向、全方位统计风速的分析成果.此外,《海堤工程设计规范》推荐用极Ⅰ型频率分布曲线统计风速,不能对工程设计关注的髙风速段进行调整和保证关注段的理论频率曲线与经验频率点最大限度地吻合,亦无法考虑系列的代表性,故不宜用于工程设计.因强风和波浪与暴雨是成因类似的随机变量,建议规范中的频率曲线统一采用皮尔逊Ⅲ型曲线.

Little difference exists in the impact of strong wind and water wave on constructions when their positive angle varies within the range of ±45°.The method for analyzing wind speed with statistics from 8 azimuth angles,as specified in Code for Design of Sea Dike,could result in safety hazard in engineering designs since the amount of average wind speed for each azimuth will be inevitably smaller,which will lead to design wind speed in the low side.For a safer design,employment of all-directional statistics for wind speed is recommended until new and more reliable statistics are available.Besides,the Gumbel distribution as the frequency distribution curve for compiling wind speed statistics,which the Code for Design of Sea Dike recommends,seems unsuitable for engineering designs,due to the fact that it can not be adjusted in the high-wind-speed section,a key engineering concern,and thus it is unable to ensure the maximum consistency between the theoretical frequency curve and the practical frequency points of that section,and it is unable to consider about their representation of the series.As strong wind,water wave and rainstorm are all random variables with the similar cause,this paper proposes that the code employ Pearson type Ⅲ curves for all frequency curves.