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风荷载是结构设计中的主要荷载之一。它的值是风压的函数。我国荷载规范中的基本风压规定应由五十年内可能出现的最大基本风压的概率分布来确定。实际上,这种概率分布很难直接求得。通常,它可按年基本风压的分布推出。利用历史数据,可以证明我国的年基本风压和北京地区的月基本风压的分布都可描述成极值——Ⅰ型分布。同时可以证明基准期的风压可以用月风分布推求,且可描述成极值——Ⅰ型分布。基准期风分布的数学期望是一个重要的参数,我国现行荷载规范中基本风压的标准值,就是考虑了风向因素后的设计基准期风压分布的数学期望。本文列出了八种不同基准期的风压分布理论上的数学期望。同时将数学期望与实际记录数据的平均值作了对比。分析结果表明,估计的风速平均值的精度相当高。
Wind load is one of the main loads in structural design. Its value is a function of wind pressure. The basic wind pressure regulations in the load regulations in China should be determined by the probability distribution of the maximum basic wind pressure that may occur within fifty years. In fact, this kind of probability distribution is difficult to find directly. In general, it can be introduced according to the distribution of the basic wind pressure of the year. Using historical data, it can be proved that the annual basic wind pressure in China and the distribution of basic wind pressure in the month in Beijing can be described as extreme values—I-type distribution. At the same time, it can be proved that the wind pressure during the reference period can be estimated by using the monthly wind distribution, and can be described as an extreme value, type I distribution. The mathematical expectation of the reference period wind distribution is an important parameter. The standard value of the basic wind pressure in the current load regulations in China is the mathematical expectation of the distribution of wind pressure in the design reference period after considering the wind direction factors. This paper lists the theoretical mathematical expectations of wind pressure distribution for eight different reference periods. At the same time, the mathematical expectation was compared with the average of the actual recorded data. The analysis results show that the accuracy of the estimated average wind speed is quite high.