Effects Of Dynamic Pressure Measurement Of Tubing Systems On Wind Loads Characteristics Of Tall Buildings

With the rapid urbanization development and great advances in technology, new tall buildings are becoming higher, lighter and more flexible than those in the past, which has made the fundamental frequency of these structures to be close to the predominant frequency of wind actions. Furthermore, the lower damping of tall buildings has worsened their wind-resistant performances. Wind loads have gradually become a dominant factor for tall buildings in terms of safety, comfort and economy. Tubing systems of pressure measurements have a significant effect on fluctuating pressures, which may distort the fluctuating wind pressures. However, the research efforts on the influences of tubing systems on wind loads of tall buildings has rarely been reported. An in-depth study on wind loads characteristics of tall buildings measured with different tube lengths was carried out in this study. The main conclusions can be summarized as follows:The theory of tubing system was firstly introduced and the transfer function on the basis of the dissipative model for tubing systems were introduced and discussed. Amplitude and phase characteristics of transfer function variation with frequency were analyzed. Transfer functions determined by the test verified the accuracy of the theoretical model. The distortion effects of fluctuating wind pressure by tubing systems of pressure measurements were eliminated in time domain and frequency domain based on the transfer functions.Tall building rigid models with different tube lengths were tested in a wind tunnel for simultaneous pressure measurements. Mean and fluctuating wind pressure characteristics of the tall building models and the influences of tube length s on wind pressure characteristics were presented and discussed. The results showed that tube lengths had negligible effects on mean wind pressures, but imposed great influences on fluctuating wind pressures. The fluctuating wind pressures decayed faster with longer tube length. The correlation and coherence of fluctuating wind pressures in time domain and frequency domain were analyzed for models with lengths and the power spectra of fluctuating wind pressures were also studied. Peak factor was obtained by the target probability method and peak wind pressures were provided for models with different tube lengths.Amplitude and frequency characteristics of wind force coefficients and coherence function as well as the influences of tube lengths on wind loads characteristics were studied. Taking the tube length as the basic variable, the formulas of wind force coefficients for models with different tube lengths fitted by the nonlinear least-square method were proposed on the basis of the experimental measurements. Mathematic models of wind loads in the along-wind, across-wind and torsional directions for the cases of different tube lengths were proposed by quadratic fitting method. Meanwhile, mathematic models of the coherence function in along-wind, across-wind and torsional directions were als o presented. The fitting results were consistent with those wind tunnel test ing results.The influences of tube lengths on the equivalent static wind loads and wind-induced accelerations of tall buildings were investigated. Four methods including GLF method, GBJ method, MGLF method and analytical method were adopted to determine the wind-induced response of tall buildings in frequency domain. The equivalent static wind loads and wind-induced accelerations of tall building models with different tube lengths were determined by the analysis of wind tunnel test data according to random vibration theory and compared with those estimated from the design codes of China and Japan.