低层四坡屋面房屋风载体型系数的分析与实用计算

Analysis and practical determination of wind-load shape factors for low-rise hip roofed buildings

利用数值模拟和风洞模型试验,获得了低层四坡屋面房屋在不同风向角下的屋面风载体型系数的实用计算公式。首先对缩尺比为1∶20的四坡屋面房屋模型(足尺为平面7.5 m×15 m,檐口高度9.6 m,挑檐长度1.5m)进行了风洞试验,再通过改变体型参数对5种屋面坡角、5种房屋高宽比和长宽比情况的屋面风压进行了数值模拟。通过对数值模拟和试验结果的分析发现,屋面坡角及房屋高宽比是影响屋面风荷载的主要因素。据此提出了屋面各分区风载体型系数的实用计算公式,并给出了计算实例,将计算结果与试验结果作了比较。结果表明,该实用公式简便准确,可直接供四坡屋面房屋抗风设计参考和应用。

Practical formulas for determination of wind-load shape factors on the roof of low-rise hip roofed buildings under different wind directions have been proposed by means of the numerical simulation and wind tunnel test investigation. The basic size of the building under consideration is 7. 5m×15 m in plan, 9.6 m of cave height and 1.5 m of overhang length. A boundary layer wind tunnel test was conducted for the building model at a geometric scale of 1 ： 20 and numerical simulations were carried out for the buildings with various roof pitches of 15^＊, 25°, 35°45°and 60°, various height-width ratios of 0.4, 1.0, 2.0, 3.0 and 4.0 and various length-width ratios of 2.0, 3.0, 4.0, 5.0 and 6.0. The obtained numerical results and the corresponding test data （if available） are presented in the paper and compared with each other. The results indicate that the roof pitch and height-width ratio are the main factors influencing the hip roof pressures. Practical formulas for determination of the hip roof shape factors are then proposed. A numerical example showing application of these formulas is finally given and good agreement is reached between the practical determination and wind tunnel test. It demonstrates that the proposed formulas are accurate and directly applicable to wind resistant design of hip roofed buildings.