Research On Urban Wind Environment Considering The Influence Of Underlying Surface And Its Influence On Wind Resistance Characteristics Of Low-rise Buildings

Studies on the prevention of wind damage in cities and the windresistant characteristic of buildings become more important as urban living areas are developed into that which are vulnerable to wind damage.With the purpose of studying the influence of urban wind environment affected by underlying surface on the windresistant characteristic of low-rise buildings,the following three aspects of work have been carried out.(1)The study on the simulation of multi-scale urban near-surface wind field.Urban near-surface meteorological conditions affected by "Meranti" were simulated on the basis of WRF-UCM Urban Canopy Scheme,and the result was compared and verified after combining the data from meteorological stations.Then,the NSRFG method was used to fit the average wind speed of WRF grid points so that a small scale large-eddy was generated to simulate boundary pulsating wind inlet,and the variation law of mountain terrain wind field under small scale was analyzed.(2)The study on wind tunnel experiment on small-scale urban wind environment.The buildings and terrain scale of simulated area were restored.The pedestrian comfort threshold probability of this area was obtained by taking advantage of the experimental data and meteorological observation data with the three-parameter Weibull distribution.And the comfort level of wind environment was evaluated in accordance with other national regulations.(3)The study on the influence of terrain on the wind-resistant characteristics of low-rise buildings.The values of terrain correction coefficient in load codes of different countries were compared with the acceleration ratio of horizontal wind direction obtained from the test.On the basis of the this study,the wind-resist characteristics of low-rise buildings under the influence of terrain was studied.The wind pressure model of low-rise buildings was placed in different locations of mountains,and the roof wind pressure characteristics and the change of probability characteristics were obtained by wind tunnel tests.The research results of this paper are mainly summarized as follows.The wind profile index of the mesoscale simulation of "Meranti" was 0.148.The near-surface meteorological data obtained by using the urban canopy scheme had a similar trend with the observation values of urban meteorological stations,and the simulation error became smaller.When carrying out downscaling simulation,the fluctuating wind speed spectrum obtained by the NSRFG method was closer to the theoretical wind spectrum than the traditional harmonic synthesis method.The wind tunnel experiment was further verified that the surface characteristics of city underlying surface changes the characteristics of incoming wind field,and the test fitting data was larger than the Ctype surface value specified in the Building Load Code.The variation law of terrain correction coefficient obtained from the test was same as that of American load code,while the value of Chinese load code was more conservative.The roof of low-rise houses at the top of the mountain was most affected by negative pressure,and the roof wind pressure at the top of the mountain has the most obvious non-gaussian feature at the same time.Relevant research results can provide references for urban wind environment assessment and wind load values.