Wind Load Distribution Characteristics of Long-span Flat Roof Structure Under Downburst

Abstract:

Based on an experimental apparatus for downburst simulation， a 1∶300 downburst wind field suitable for the wind pressure distribution test of a long-span flat roof structure was simulated in the atmospheric boundary layer wind tunnel. On this basis， the wind pressure distribution characteristics of the long-span flat roof structure under downburst were studied， and were compared with the corresponding test results in exposure category B. The results show that in the model area， the relative position of downburst has little effect on the wind pressure coefficients； the average wind pressure distribution under downburst is basically the same as that in exposure category B， but the maximum absolute value of minimum wind pressure coefficient reaches 9.85， and is 77.8% higher than 5.54 in exposure category B； the corresponding power spectrum of fluctuating wind pressure is significantly higher than that in exposure category B； the maximum wind pressure coefficients of flat roof in exposure category B are close to or less than 0. However， in different wind directions under downburst， the ratios of the roof area with the maximum wind pressure coefficients over 0.15 are between 51% and 75%， and the local maximum wind pressure coefficient reaches 0.35； the high positive pressure in a large area will further affect the bearing capacity of the structure.

Key words:downburst;wind tunnel test;long-span flat roof;wind pressure distribution;wind field characteristics