斜置方柱气动力特性试验研究

土木工程结构中有很多方形断面的细长结构,常常受到斜向风作用,其风荷载可以简化为斜置方柱的气动力,与垂直风向作用不同,目前尚没有明确的气动力估算方法。针对此问题,采用刚性节段模型测压风洞试验,分析了风偏角对方柱的静态气动力特性的影响规律。结果表明:采用传统风速分解法仅可以有效地估计在分离点之前的风压,并不适用于斜置方柱完整气动力的估算;由于背风面风压的减弱,斜置方柱的平均和脉动气动力系数小于垂直方柱的对应值;斜置方柱的旋涡脱落频率小,强度弱,频带宽。因此,采用垂直方柱的平均气动力作为方柱抗风设计的平均风荷载是偏于安全的,但是由于旋涡脱落频率及带宽的变化,斜置方柱的风致振动与垂直方柱会有明显的差别。

Experimental Study on Characteristics of Aerodynamic Force on Yawed Square Cylinder

Slender structures with square cross-section, which are widely used in civil engineering, expose in the oblique wind during its service. The wind loads on this structure can be simplified as the aerodynamic forces on a yawed square cylinder. Unlike cylinders under wind normal to its length, an estimation of aerodynamic forces for yawed square cylinders are still unclear. In the present study, the wind pressure distribution on the yawed cylinder is tested in the wind tunnel to illustrate the effects of the skew angels on aerodynamic characteristics. The results show that the conventional wind velocity decomposition can only estimate the pressure distribution before the separation points rather than estimate the whole aerodynamic forces on the yawed cylinders. The mean value and standard deviation of aerodynamic forces on the yawed cylinder are smaller than those on the normal cylinders due to the weak wind pressure on the leeward side. The yawed cylinders also have smaller vortex shedding frequency, weaker vortex and wider frequency band than the normal cylinders. Therefore, it is conservative wind load, which uses mean aerodynamic forces for the normal cylinder instead of the yawed cylinder, but the change of the vortex shedding frequency and band of frequency may induce the significant difference on wind-induced vibrations.