The Across-wind Response Analysis And TMD Control Of Super-tall Buildings

Super-tall buildings are generally categorized as flexible structure, which exhibit extraordinary dynamic-sensitivity to wind loads. It is therefore imperative to accurately estimate wind-induced responses with respect to the serviceability of structures, as well as the occupant comfortability and economic efficiency. This dissertation presents investigations based on an abuilding super-tall-structure in Shenzhen, with emphasis on the analysis of across-wind responses and vibration control.1. On the basis of the results derived from the High Frequency Force Balance (HFFB) test, the wind-induced responses of a super-tall building are characterized through spectrum analysis, with the assistance of Moment Gust Loading Factor (MGLF) method. The results indicate that the across-wind loads and acceleration of the structure are considerably larger than that in the along-wind direction, which need to be taken care in the structural design. Additionally, the influence of torsional responses on the determination of equivalent static wind loads and the assessment of structural serviceability are insignificant, and wind-induced responses are dominated by resonant components in bending direction, while in torsional direction, resonant components are not essential part.2. A simplified Finite Element Model is developed in attempt to give time-history analysis of wind-induced responses of the super-tall building. It is noted that the dynamic responses of the structure in the across-wind direction are more pronounced than the along-wind responses, which demonstrate a good agreement with the results in the spectrum analysis. Hence, the capability of the simplified model for practical engineering is validated.3. The comfortability of the super-tall building is evaluated in accordance with several standards and regulations, both locally and internationally. It is shown that the occupant comfort level fails to meet the requirements stipulated in the GB50009and the North American Specification. Under such condition, the vibration control is introduced with the purpose to enhance the occupant comfort.4. In this dissertation, a comparative analysis of various methods for the determination of the optimal parameter of Tuned Mass Damper (TMD) is given. It is observed that the differences of results generated from various methods are indistinguishable under small mass ratio. The wind-induced responses of the tall building with the installation of TMD are analyzed through the simplified model. The results show that the employment of TMD could significantly diminish the vibration. Meanwhile, it is to be noted that the optimal damping ratio derived from theoretical analysis is slightly different from that generated analytically. Based on the integrated consideration of damping effect and the displacement of TMD, it is suggested to adopt a TMD system with non-linear damping ratios. At the end, the discussion on the locking mechanism of the TMD system when its displacement exceeds the space restrictions is presented.