The Wind-induced Interference Effects Study Of Flat Roof In The Normal Pattern

ABSTRACT:Wind load is one of the critical loads for long span buildings. With the development of urbanization, the distribution of long-span roof structures tends to be more dense. So the interference effect due to the surrounding buildings becomes one key issue in the engineering design. In order to study the interference effect of long-span flat roof, wind-induced interference on flat roofs are investigated with wind tunnel tests in this paper.At first, average and fluctuating wind loading characteristics of the isolated long span flat roof of different sizes are investigated. The results show that the extreme values of suction pressures on the corner of the flat roof are very large, and with the increase of the building height, the extreme suction pressures on the corner of the roof will increase gradually. Then the design of orthogonal experiment and corresponding experiments are conducted. The most dangerous case of the orthogonal experiment is found according to the comprehensive influence of rows, columns, diatances, length-width ratio and height-width ratio.The most dangerous case is determined by the drag coefficient along the wind, lift coefficient cross the wind, the lift coefficient on the roof and the unfavorable minimum pressure coefficients on the roof. The main conclusions are:30degrees or45degrees is the most unfavorable wind direction for the interference factors of the lift coefficient and the unfavorable minimum pressure coefficients on the roof; the interference factor of the corner on the roof significantly enlarged when the building locates at the corner in the arrangement. The most dangerous case of the orthogonal case is that there are3rows and3columns buildings in the arrangement with the building size of48cm X24cm X12cm. In this case, the interference factor of the unfavorable minimum pressure coefficients on the roof is1.2, the corresponding peak pressure coefficients is-11.5. The effect of the distance is studied for the most dangerous case. When the distance between buildings are small, the interference shows sheltering effects, when the distance increases and the interference shows amplification.The largest interference factor of the drag coefficient along the wind will reach1.2. For the unfavorable minimum pressure coefficients on the roof,the largest interference factor can reach1.3in some local regions. For the lift coefficient cross the wind, the amplification effect can be ignored.When the distance is enough large, the interference effect gradually disappear, and the distribution of wind pressure is close to that of one isolated building.