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Loading Pattern and Spatial Distribution of Wind Load and Comparison of Wind and Earthquake Effects along the Height of Tall Buildings

Nikbakht, Hamed | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40955 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Bakhshi, Ali
  7. Abstract:
  8. In the ongoing research project on tall buildings, the study of wind-induced demands is categorized as: along-wind and crosswind responses. These demands are caused by different mechanisms. Moving along the wind-induced is due to the effects of turbulence impact while the perpendicular component is related to the effects of windstorm. Along-wind response may be of special importance with respect to the comfort criteria. The loading condition on skyscrapers may differ from low-rise buildings due to the number of stories, on structures due to the high number of stories, and the importance of dynamic effects of current loading (wind). On the other hand the effect of wind load on tall structures not only distributed over the wider surface but also it has higher intensity. Furthermore, in high risk seismic zone the seismic performance of structures are considered as the primary importance which influence other hand in seismic zones, may be the effect of impact forces resulting from earth movement greater than the forces caused by wind loads and consequently, Seismic loading determines form and final design of the structure (with this assumption that with respect to the all international codes and standards, wind and earthquake loads never simultaneously apply on the structure). The purpose of this article is that with respect to the procedure and distribution of dynamic wind and earthquake load, to investigate the height beyond which the wind load would be dominant over the seismic loading condition. For the current study, several tall steel frame building with various lateral resisting system such as Moment frame system, Outrigger system , Truss tube system , …that are almost symmetrical in plan are investigated via three-Dimensional models. In this article, the effect of dynamic time history wind load is considered and when it’s applied along the height of tall buildings, the fluctuating wind speed is simulated as an ergodic multivariate stochastic process, and the fast Fourier transform is needed to estimate the fluctuating wind speed components acting on the structure. One group of analyses are performed by simulating fluctuation wind speed under Dynamic time history wind load and its counterpart, nonlinear dynamic earthquake load due to excitation from the ground motion earthquake accelerograms. This study has focused on four prominent structural demands such as the peak inter story drift (which is a failure index), maximum story displacement and peak story shear and moment was evaluated and was determined that the structure with lower height or number of stories in which parameters dominant in seismic loading and with increasing in height of buildings, rate of influence of wind load along the height in which parameters is larger than seismic loading and the results of wind and earthquake characteristics was compared in form of power spectral density (PSD). Finally, the effects and values of these structural parameters resulting from models were compared based on international standards and regulations related to earthquake and wind load.
  9. Keywords:
  10. High Structures ; Wind Effect on High-Rise Buildings ; Charge Efficiency ; Seismic Load ; Dynamic Loads

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