地貌类型和长宽比对平屋面建筑风荷载的影响分析

Effects of terrain and length-width ratio on wind loads of flat-roof building

通过风洞试验研究了地貌类型和建筑物平面长宽比对平屋面建筑平均风压系数、均方根风压系数、极值风压系数、屋面平均升力系数的影响规律,研究结果表明:地貌类型对平均风压系数影响较小,对均方根风压系数、极值风压系数影响显著,对于与模型短边正交的风向角下,C类地貌下典型断面迎风分离区均方根风压系数最大值约为A类地貌的1.5倍,A、B、C类地貌条件下典型断面的再附点距迎风前缘的距离分别为0.7H、0.4H、0.3H(H为模型高度);建筑平面长宽比对风压系数的影响较小,增大沿风向方向的建筑物长度,屋面更多区域处于气流再附后区域,平均升力系数幅值减小;地貌类型和长宽比对屋面角部区域全风向极值风压系数影响较大,对中间区域影响较小,对于角部区域,C类地貌下的极值风压系数较A类和B类地貌的明显偏大,长宽比为2.5模型的极值风压系数明显较长宽比为1.5和2.0模型的大,增幅均在20%左右。

With wind tunnel tests,the effects of terrain and building length-width ratio on wind loads of buildings with a flat roof were investigated,in terms of the mean,the RMS and the peak pressure coefficients,and the mean lift coefficients on the roof.The results demonstrate that the terrain has little effects on the mean coefficients on the roof, but has significant effects on the RMS and peak pressure coefficients.The RMS pressure coefficients on the windward separation area of the typical roof section in terrain C is about 1.5 times those in terrain A,and the distance from the windward edge to the flow reattachment is 0.7H,0.4H and 0.3H( H is height of the model),respectively,in terrain A,B and C when the wind direction is orthogonal to the short edge of the building.Increasing the building length along the wind direction has little effects on the pressure coefficients along the typical roof sections,makes more area of the roof be covered by the flow reattachment,and reduces the mean lift force coefficient on the roof.Both the terrain and the building length-width ratio have significant effects on the most unfavorable peak pressure coefficients for all wind directions at the roof corner area,but have little effects on those at the middle and center roof areas.For the roof corner area,the most unfavorable peak pressure coefficients in terrain C is larger than those in terrain A and B,and those for the roof with a length-width ratio of 2.5 is 20% larger than those with a length-width ratio of 1.5 and 2.0.