Investigations Of Wind Loads On Low-Rise Buildings And The Applications Of Typhoon Wind Field In Surface Boundary Layer

Based on the field measured data recorded by a typhoon measured system on a low-rise building, wind characteristics in surface boundary layer during typhoon landfall were investigated in detail. In addition, the typhoon wind field was simulated in the wind tunnel tests, which was further utilized for the experimental measurements of wind pressures on a long-span structure. The wind pressure characteristics and peak negative wind pressures on a flat roof low-rise building were investigated with field measurements and wind tunnel tests. Several extreme values estimate methods were examined on the basis of full-scale data. In addition, the discrepancies of wind pressure characteristics between the field measurement and wind tunnel tests were expounded. On the basis of wind tunnel tests of a low-rise building with a sudden opening on its roof corner, the instantaneous wind pressure distribution, internal pressure spectra and wind-induced pressure transmit mechanism were investigated in detail. The outcomes of this study are of great use for the wind-resistant design in typhoon-prone areas. The main conclusions are as follows:The intensity of fluctuating wind direction enhanced the longitudinal and lateral turbulence intensity during the passage of typhoon Kalmaegi, and the lateral turbulence intensity had an approximate linear relationship with the rising of wind direction fluctuation. The study illustrated the field measured longitudinal wind spectra coincided quite well with empirical spectrum in low frequency.According to the experimental data of a long-span structure with a retractable roof under simulated typhoon and conventional wind fields, the results indicate that mean wind pressure distribution on the movable roof were similar in a same open form. The opening of the movable roof resulted in decreasing mean wind pressures. Under the influence of high turbulence level in typhoon wind field, the movable roof was prone to suffer extreme wind loads. Moreover, the entire opening of the movable roof had a significant impact on fluctuating wind pressure on the whole roof.The comparison between the field measurements and wind tunnel testing results of wind pressures on a low-rise building illustrated that the mean wind pressures on a roof corner were greater than the experimental values. For the middle zone of roof edge, the field measured values were about 40% larger than the experimental results when the incident flow was perpendicular to a surface of the building. In addition, the field measured wind pressure deviated significantly from the Gaussian distribution, while less non-Gaussianity was observed in the wind tunnel results. Among several statistical models, the three-parameter Gamma distribution proved valid to characterize the probability distribution of wind pressure on low-rise buildings.It is confirmed the best observed short time interval for full-scale peak negative pressure estimation was 30 seconds via the error analysis. On the basis of the available estimation methods, it is difficult to identify a stable and accurate method to determine peak wind pressure. It is found that the Sadek-Simiu method was conservative, which was recommended when the accurate peak pressures cannot be determined. The on-site peak pressures estimated by the Sadek-Simiu method were greater than those of experimental results by 20% to 40%.When a sudden opening occurred, the instantaneous negative pressures generated on a roof corner and internal wind pressure tended to be stable in 0.05 s. The internal fluctuating wind pressure was closely related with turbulence intensity in approaching winds. The correlation coefficients among the time histories of internal wind pressures were quite high, suggesting that it is feasible to represent the features of internal pressure in time domain with one pressure tap.Different quantity peaks appeared in the coherence function curves of internal wind pressure in both turbulent flow and uniform flow field. The analysis results suggested that they may be caused by building vibration, turbulent flow, and signature turbulence. Under oblique flows, the conical vortices that emerged on roof surface resulted in Helmholtz resonance phenomenon. For the governing equation of internal pressures with a single opening, the theoretical value of Helmholtz frequency and the experimental results were almost equal with inertial coefficient C_I of 1.6 and without the damping effects and. For an aperture ratio of about 4.8% of a square opening on a roof corner, the inertial coefficient is larger than that of the opening on windward wall.