Investigation of a downburst loading event on a full-scale low-rise building

Abstract

This paper details a downburst event that occurred on June 19, 2003, where both wind and wind-induced pressure data were recorded at the Texas Tech University Wind Engineering Research Field Laboratory (WERFL). This event displayed rapid changes in wind speed (i.e. ramp-up and ramp-down) and wind direction over a period of approximately 30 s. The event also exhibited an atypical vertical wind profile with a peak measured wind speed occurring at 4 m and wind direction changes up to 30 deg over the 50 m anemometer tower height. Wind loading on the WERFL building also displayed ramp-up and ramp-down behavior. When converting these data to pressure coefficients (Cp,3), non-stationary pressures were normalized by a 3-s wind speed, which was shifted by a time lag to account for the spatial separation between building and tower. Differences were discovered in Cp,3 between ramp-up and ramp-down periods. To ascertain any differences between downburst loading and that induced by atmospheric boundary layer (ABL) wind fields, loading characteristics were compared in the same fashion with 128 ABL events at WERFL. Analysis of the comparisons concluded that downburst Cp,3 values mostly stayed within the bounds of the ABL, however fluctuate between extrema of ABL distributions. A significant difference between ramp-up and ramp-down periods was further solidified as ramp-up (ramp-down) Cp,3 values were lower (higher) than expected in the ABL. A physical explanation for these differences is unclear, and further study is needed to ascertain its validity.