Wind Loads And Wind-induced Lateral-torsional Coupled Response Of Tall Bulidings

Recently, tall buildings have becoming taller and more flexible. As a result, wind loads have increasingly become the key loads in the design of tall buildings. Wind loads and wind-induced response are major concerns to the design of tall buildings. Although no super tall building collapsed by wind actions in the past, sometimes occupants feel uncomfortable because of excessive vibration and even damages of structural components during strong winds were reported. It is thus necessary to investigate the wind loads and wind-induced response of tall buildings.A series of rigid typical tall building models were used in wind tunnel tests for simultaneous pressure measurements. Characteristics of wind-induced pressures on the surfaces of the tall building models were studied based on the test results. The effects of incident wind direction and turbulence intensity, model shapes and configurations on the pressure distributions were investigated. The probability characteristics of the surface pressures were analyzed and the peak factors were calculated by the target probability method. For rectangular tall buildings, max peak factor is preferable to be2.7, min peak factor can be taken as3.3in the middle areas of the model facades and3.9in the edge regions, respectively.Characteristics of wind loads on rectangular tall buildings were studied based on the wind tunnel test results. Mathematical models of wind loads on typical tall buildings were proposed and closed-form formulas were presented by parameter fitting. The procedures of applying the mathematical models to calculate the equivalent static wind loads and acceleration response were presented. The comparison results show that the mathematical models can be used for the wind-resistant design of tall buildings at the preliminary design stage.Additional wind tunnel tests were conducted to investigate the effects of corner configurations on wind loads on tall buildings. Compared with square section, the max pressure coefficients were not significantly affected by the shape modifications such as recessed, beveled, rounded corners. Meanwhile, the minimum pressure coefficients were also not significantly affected by the shape modifications, except that the magnitude of minimum pressure coefficients increased approximately17.03%due to modification to the rounded corners. The overall wind loads on tall buildings were reduced significantly by the corner shape modifications. For0°wind direction, the along-wind mean base moment coefficients were reduced by15.5%,19.5%and62.4%, respectively. Accordingly RMS base moment coefficients were reduced by27.8%,25.6%and73.1%. Moreover, the same results were obtained for the across-wind RMS base moment coefficients and RMS base torque coefficients. Taking0°wind direction for an example, across-wind RMS base moment coefficients were reduced by54.6%,44.7%and60.4%, respectively, and RMS base torque coefficients were reduced by68.7%,77.1%and68.4%accordingly.The equations of motion of lateral-torsional coupled tall buildings were derived and parametric analyzes was conducted. For a case study, detailed analyses of the effects of the parameters were conducted to investigate the characteristics of wind-induced lateral-torsional coupled responses of tall buildings. Compared with the results of non-eccentricity, the maximum resultant acceleration response of rectangular tall buildings increased from5.4%to10.6%under mass two-way eccentric range of5%. On the other hand, the maximum resultant acceleration response of rectangular tall buildings increased from3.9%to16.5%under stiffness two-way eccentric range of5%.The wind speed amplification effects inside holes in tall buildings with different opening ratios were investigated based on wind tunnel tests. The maximum wind speed ratio in an upper hole, with value of1.28to1.35, was found when a lower hole was closed. The value of1.31to1.39in a lower hole was observed when the upper hole was closed. The wind speed amplification effects varied with the opening ratio, and there was an optimal opening ratio for a tall building. The mean and fluctuating wind pressures around the entrances of the holes were very large when the approaching wind flow was paralleled to the axis of a hole, but the existence of holes was beneficial to decrease the overall wind loads. And the influence coefficient as a function of opening ratio was thus proposed.Pearl River Tower (PRT), located in Guangzhou, China, created a precedent on power generation in tall buildings with installation of wind turbines in wind tunnels. The wind loads and possibility for wind power generation with wind turbines installed in the wind tunnels inside PRT were systematically studied based on wind tunnel tests. The results showed that the wind power obtained from the tunnels could be29.5times than that got at height of10m, and it is potential to get wind power from the tall building. It is necessary to consider the plane direction of the tall building to be consistent with the frequent wind speed directions based on the local wind climate analysis results and the optimal elevations of the tunnels’locations, to obtain more wind power from the tall building. Moreover, the use of the "urban canyon" effect is also a good way to get the wind power in the center of city. Meanwhile, the local wind pressures near the opening holes increase, but the overall wind loads reduce due to the opening of the holes.The formation of flow separation on the top of the facade of tall buildings with atrium plays a critical role in the wind pressure generations on atrium facade of tall buildings without open hole. Meanwhile, Wind pressure distribution on the atrium facades was in uniform. Moreover, the horizontal and vertical correlation of pressure coefficient appears that an overall higher correlation at most locations on atrium facade. The mean wind pressures first decreased and then stabilized, and the fluctuating wind pressures first decreased and then increased, with the increasing of the opening holes. A method for the wind-resistant design of Atrium facade was proposed, and the results predicted by the method was in good agreement with those obtained from the wind tunnel tests, indicating that the proposed method can be used in engineering applications.In this study, the combination of wind tunnel tests and theoretical analysis was adopted to investigate the wind effects and lateral-torsional couple responses of tall buildings. The results presented in this thesis are expected to provide valuable information and reference for the wind-resistant design of tall buildings and load code revision in the future.