Wind Loads And Wind-Induced Effects Of Oval-Shaped High-Rise Structure

High-rise structures such as air traffic control tower and television tower are especially sensitive to wind actions due to structural flexibility and slenderness.Therefore, these structures may suffer from structural fatigue and wind-induced damages. Recently, more research efforts have been focused on the wind effects on elliptical-shaped high-rise structures. In this study, the wind tunnel studies of wind effects on an oval-shaped air traffic control tower at Wuhan Tianhe International Airport were conducted. In order to further understand the wind effects on elliptical cylinders, six standard oval-shaped high-rise structure rigid models with different aspect ratios and side ratios were designed and tested in the wind tunnel. The experimental measurements including wind pressures, power spectral densities,coherence functions, force coefficients and 3-D wind loads spectra on each level of the standard oval-shaped high-rise structure were presented and discussed. The main findings are summarized as follows:The characteristics of wind loads on the oval-shaped high-rise structure were investigated based on the simultaneous pressure measurements of the rigid model of Wuhan Tianhe International Airport Phase III(expansion of ATC tower) project in a wind tunnel test. This thesis has discussed the distributions of mean and peak wind pressure coefficients on numerous test points under typical wind directions. The obtained spectra of 3-D wind loads on the oval-shaped structure when the approaching flow is normal to the structural axis(corresponding to the maximum windward area).The power spectra were then fitted using empirical formulas. The mean, background and resonant equivalent static wind loads were determined by the LRC method and the inertia wind loading method. A good agreement of the equivalent static wind loads between these two methods was found.Six oval-shaped high-rise structure models with different aspect ratios and side ratios were tested with the simultaneous pressure system in the wind tunnel. Based on the test results of a typical model( H/(?) =7.5, D/ B =0.75), the effects of wind direction, pressure tap locations and various building heights on the wind pressure coefficients, coherence functions and the power spectra of wind pressure were investigated. The frequency of vortex shedding along the long axis was provided.Meanwhile, the peripheries of windward, transition and leeward regions wereidentified and discussed. The coherence functions of typical test points were fitted with empirical models. The results indicate that the largest horizontal coherence occurred at the transition region and largest vertical coherence was observed at maximum curvature positions, but the values were lower than those of rectangular buildings.The effects of upstream terrain, side ratio and aspect ratio on the wind force coefficients and 3-D wind load spectra at each level of oval-shaped high-rise structures were investigated. Different wind load spectral models were used to fit the3-D wind loads spectra at each level. Taking the turbulence intensity and side ratio as variables, the wind load spectral models of 3-D wind loads spectra of oval-shaped high-rise structure were developed with the 2-parameter fitting method. The root-mean-square displacement responses of each floor of Wuhan ATC tower were calculated by these mathematical models. In order to further understand the relationship of oval-shaped high-rise structure between along-wind loads, across-wind loads and torsional wind loads, the coherence curves of along-torsion and cross-torsion with different side ratios were presented and discussed. The results indicate that the coherence of cross-torsion is generally higher than along-torsion, and high coherence of cross-torsion maintains over a wide frequency range with multiple spectral peaks. The coherence of along-torsion is generally low, but it becomes higher when the side ratio is close to 1, which proves that the torsional coefficients reach maximum when the side ratio is close to unity.