大尺度屋盖围护结构的风荷载作用机理与极值概率模型

The cladding and components of large-scale roofs is often damaged by the extreme wind loads; therefore the extreme values of wind loads are the important design load for claddings. Based on the synchronous measurements of wind pressure, flow visualization of conical or cylindrical vortices, the spatio-temporal evolvement of the vortices on the roof is investigated while the characteristics of the conical or cylindrical vortices in time and frequency domains are studied. Then the connections among the upstream, the vortices and wind pressure on the roof is established. Then the explicit expressions of the extreme value probability distribution and the joint probability distribution of wind pressure are presented using the Hermite moment model and the probability transform between the multiple variables. The Monte Carlo simulation is used to predict the extreme wind load of small failure probability and to validate the probability distribution of extreme wind load. Finally the design wind load and the reduction coefficient for cladding and components of the large-scale roofs are determined respectively on the basis of the probability distribution and the joint distribution of the wind load after the roof is divided into several pressure zones.

大尺度空间结构的风致破坏往往发生在屋盖围护构件部分，屋盖围护构件的风荷载极值成为围护结构设计的重要荷载之一。本课题采用风洞测压实验、流动显示方法探究屋盖上部锥形涡/柱状涡的时空演化运动，建立来流-涡运动特征-屋盖风压之间的关系。在此基础上，利用Hermite矩模型理论和多变量函数的概率变换，建立多样本情况下屋盖风压极值概率分布的显式表达式以及风压极值的联合分布。为了补充、验证风洞测压实验结果，采用Monte Carlo方法模拟屋盖风压极值的小概率事件，得到极值分布的数值模拟结果。在屋盖风压极值概率分布的研究基础上，划分大尺度屋盖风压分区，确定屋盖围护结构的分区设计风荷载以及大尺度屋面板风荷载的折减系数。

本项目在屋盖围护结构非高斯风压极值方面开展了研究，取得如下研究成果。基于Hermite矩模型变换理论，建立了单样本风压时程非高斯峰值因子的理论求解方法，为短时距风压时程样本估计风压极值提供了理论基础；提出的多样本非高斯峰值因子概率分布解析式的适用性，结果表明，提出的非高斯峰值因子的概率分布解析式适用于估计各种强、弱非高斯风压时程的峰值因子；提出了非高斯峰值因子的简化计算公式，其理论误差在工程应用的可接受范围之内；探讨了平屋盖围护构件的设计风荷载取值，指出了我国荷载规范中围护构件风荷载取值的不合理之处；进行了L形和T形低矮房屋围护构件风压系数极值的试验研究，填补了国内外研究空白；主持制订了行业标准《屋盖结构风荷载标准》（报批稿），突破了我国低矮建筑、大跨度建筑屋盖围护结构设计风荷载无据可依的困境。