波纹状悬挑大跨屋盖的风荷载特性

Wind load on wavy-shaped long-span cantilevered roof

采用同步测压风洞试验技术,对相同尺寸的波纹状悬挑屋盖、光滑表面悬挑屋盖风荷载进行了研究,重点讨论了波纹形状对悬挑屋盖风荷载的影响。风压分布云图表明,波纹形状没有改变风荷载的主要作用机制,但加剧了来流在屋盖前缘的分离。通过积分得到了对屋盖主体结构抗风设计起控制作用的弯矩系数,相对于光滑表面悬挑屋盖,最不利风向角下波纹状悬挑屋盖的平均弯矩系数增加23%,脉动弯矩系数增加20%,但波纹形状减缓了脉动风荷载在折算频率0.1~0.2范围内的能量集中。波纹形状对风压极值影响较大,特别是对围护结构抗风设计起控制作用的负压极值,波纹状悬挑屋盖较光滑表面悬挑屋盖增加13%。进行波纹状悬挑屋盖抗风设计时,不考虑波纹形状的影响是不安全的。

High-frequency-pressure-integration tests were carried out in a wind tunnel to investigate wind load characteristics on smooth cantilevered roof and wavy-shaped cantilevered roof, both of which have the same size. The effects of wavy-shaped roof surface have been evaluated in wind tunnel test. Wind pressure distribution shows that, wavy shape does not change the main mechanism of wind load, but intensifies the separation on the front edge of the roof. Bending moment coefficient is a controlling factor for the wind-resistance design of the main roof structure, and can be derived from integration. Relative to the smooth surface cantilevered roof, the mean bending moment coefficient of the wavy-shaped cantilevered roof is increased by 23% and the RMS （root mean square） of bending moment coefficient of the wavy-shaped cantilevered roof is increased by 20% , under the most unfavorable wind direction angle. But wavy shape decreases the energy concentration of the fluctuating wind load when reduced frequency is between 0. 1 and 0.2. Wavy shape has strong influence on the extreme wind pressure, since wind uplift on wavy-shaped cantilevered roof is 13% larger than that on smooth surface cantilevered roof, which is the controlling factor of the wind-resistant design of cladding structures. The influence of wavy shapes should be considered for the wind-resistant design of the wavy-shaped cantilevered roof to ensure safety.