Typhoon-Induced Wind Pressure Characteristics on Large Terminal Roof Based on Mesoscale and Microscale Coupling

摘要

Local roof failure is the most typical form of wind-induced failure of large-span terminals, especially in southeast coastal regions with frequent occurrence of strong typhoons. Since existing theoretical systems of typhoon model in civil engineering are too simplified, the mesoscale weather research and forecasting (WRF) mode based on the non-static-equilibrium Eulerian equation model was introduced into for high temporal-spatial resolution simulation of the Typhoon Megi. Wind field characteristics in the landing process of Megi, including wind intensity, pressure intensity, rainfall intensity and temperature stratification, were analyzed by the multigrid nesting technology in mesoscale mode. Key attentions were paid to wind direction angles and wind intensity before, during, and after the landing of Megi. Results verified the validity of the mesoscale simulation of Megi. Later, the wind velocity profile in the boundary layer of the typhoon field was gained by combining the nonlinear least-squares method. The three-dimensional (3D) flow field information and the time history of surface fluctuating wind pressure of the roof system of the terminals in Xiamen International Airport were acquired from three-dimensional wind field simulation under typhoon and Type A monsoon (hereinafter referred to as monsoon) conditions. The three-dimensional wind field simulation was accomplished by the microscale computational fluid dynamics (CFD) large-eddy simulation technique. On this basis, the mechanisms of flow field action and spatial characteristics of mean wind pressures, fluctuating wind pressure and extreme wind pressure on roof surface under monsoon and typhoon conditions were compared. Moreover, correlation, coherence, power spectral characteristics, and non-Gaussian characteristics of fluctuating wind pressure were analyzed. Results demonstrate that the WRF/CFD coupling mode can simulate a typhoon field in terminals effectively. A mesoscale typhoon can increase the mean wind pressures, fluctuating wind pressure, and extreme wind pressure on roofs significantly, which all occur on the upper-eave areas. The non-Gaussian characteristics of wind pressures on a terminal roof under typhoon conditions are influenced greatly by wind direction angle, but the correlation of time-frequency domain of wind pressures is weak. Major research conclusions not only provide some references for prediction of wind loads on similar large-span spatial structures under typhoon conditions, but also deepen understanding on the nesting mechanism of mesoscale/microscale wind fields.