Wind-induced Interference Effects On Long Span Flat Roof

Long span roof buildings are always built in densely urbanized areas and the wind load is one of the critical loads during their structural design. Wind-induced interference effects between the constructions will have significantly impact on the wind load distribution of long span roofs. Flat roofs, a typical kind of long span roof, are widely used in application. In this paper, wind-induced interference effects on flat roofs are investigated by wind tunnel tests.At first, average and fluctuating wind load distribution characteristics of single long span flat roof are carried out by wind tunnel tests and CFD numerical simulation. The results show that with the wind direction increase, the extreme values of suction pressures on the corner of the flat roof will increase gradually. Secondly, another same shape building is set around this flat roof, by altering the relative position between the two buildings and wind directions to research the variation of wind pressure distribution on the flat roof. These results are compared to the results with those of one single long span roof and a series of variation rules of wind pressure and interference factor distribution are obtained. Main conclusions:45degrees is the most unfavorable wind angle for the interference factors of the overall average pressure coefficient on the roof of the building, and local interference factors of the roof neighboring the interfering building are dramatically amplified. As to the interference factor for the minimum peak pressure coefficients on the roof, it could be seen that with the increase of the wind angle, the portion of the moderately and dramatically decreased areas become larger and larger, while that of the moderately and dramatically amplified areas become smaller and smaller; under all the wind angle possibilities, when the interfering building is located in the place (Sx,Sy)=(-0.5,-1.5), the minimum peak pressure coefficients on the roof of the principal building decreases dramatically, which demonstrates itself most patently under the wind angle of0degree. A comparison made between the calculated and tested data in terms of the interference factors for the average local pressure coefficients and the local minimum peak pressure coefficients indicates that the real control load still concentrates on the edges and corners of the windward side. The influence of the interfering building upon the first modes generalized force of the roof of the principal building is reflected mainly in the lower frequency parts, and the interference factor for the RMS of the first modes generalized force varies in the similar mode as the interference factor for the overall average pressure coefficient on the roof.