屋顶构造形式对传统民居风荷载特性的影响

Influence of roof members on wind load characteristics of traditional low-rise residence buildings

根据广东沿海传统民居的建筑特点,通过在屋面上增加不同样式的构筑件(厝头和屋脊),设计并制作了11种低矮双坡民居建筑模型(包括纯双坡屋面)并对其进行风洞试验,以研究不同构筑件组合对屋面结构风压分布的影响。研究表明:双坡屋面靠近屋脊和山墙侧位置由于流动强分离导致高负压区,极值负压系数达到-6.62,这也是风灾中双坡民房常遭局部破坏的原因;而在屋面增加6种不同样式的厝头(金、木、水、火、土、尖厝头)和屋脊都可降低双坡屋面结构的风荷载;增加不同构筑件对屋面风压分布影响不同,金厝头效果相对最好,可将最大平均负压系数绝对值减小32%,最大极值负压系数绝对值减小35%。此外,极值负压对屋脊高度变化相对不敏感,但镂空屋脊对降低风荷载有帮助。最后通过风洞试验数据的统计分析,对厝头和屋脊的气动机理进行了辨析:厝头的作用是消减屋面靠近山墙附近的极值负压,屋脊的作用在于降低屋面中间部分的极值负压绝对值。总结文中研究的几种样式的构筑件和参数组合工况,1 020 mm金厝头和800 mm镂空屋脊是一个较好的组合配置。

Based on the architectural features of traditional residence in Guangdong coastal area,totally 11 low-rise gable building models（ including the pure gable roof building itself） with different roof members（ house heads and roof ridges） were designed and the wind tunnel tests were carried out in order to explore the influences of different roof members on the roof wind load distributions. Results show that a high negative pressure zone on the roof close to the side wall and the ridge appears for the pure gable building due to strong flow separation,and the extreme negative pressure coefficient is reached- 6. 62,which is exactly the reason why the gable roof buildings are susceptible to local damage in strong wind. All six different combinations of the roof members can reduce the wind loads at different levels,which are the metal,wood,water,fire,earth and the pointed style house head respectively. Among them,the metal style has the relatively best effect. The absolute values of the maximum mean and extreme negative wind loads can be reduced by 32% and 35% respectively. Although increasing the height of the roof ridge has hardly any benefit for reducing the absolute value of the extreme negative wind load on roof,hollowing the roof ridge will do. Finally,the aerodynamic mechanisms of both the house head and the roof ridge were then analyzed based on the statistical analyses on wind tunnel test data. For the house head,it could reduce the high absolute value of the negative wind pressure close to the side wall,while for the roof ridge,it could reduce the high absolute value of the negative wind pressure in the middle roof area. It is concluded that a combination of‘1 020 mm metal roof ridge and 800 mm hollow house head＇is a relatively better scheme in current study.