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TALL BUILDINGS: DESIGN ADVANCES FOR CONSTRUCTION
Edited by: J.W. Bull
Coupled Dynamic Wind Load Effects on Tall Buildings with Three-Dimensional Modes
X. Chen1 and A. Kareem2
1Wind Science and Engineering Research Center, Department of Civil and Environmental Engineering, Texas Tech University, Lubbock TX, United States of America
X. Chen, A. Kareem, "Coupled Dynamic Wind Load Effects on Tall Buildings with Three-Dimensional Modes", in J.W. Bull, (Editor), "Tall Buildings: Design Advances for Construction", Saxe-Coburg Publications, Stirlingshire, UK, Chapter 3, pp 55-86, 2014. doi:10.4203/csets.33.3
Keywords: wind loads, wind tunnel tests, tall buildings, building design, structural dynamics, dynamic analysis, random vibrations.
Tall buildings with either complex geometric shapes or structural systems with noncoincident centers of mass and resistance, or both, may undergo three-dimensional (3D) coupled motions when exposed to spatiotemporally varying dynamic wind loads. To capture these dynamic load effects, this chapter presents a framework for the analysis of 3D coupled dynamic response of tall buildings and modeling of the equivalent static wind loads (ESWLs) customarily used in design. This framework takes into account the correlation among wind loads in primary directions and the intermodal coupling of modal response components with closely spaced frequencies. The complete quadratic combination (CQC) rule is re-defined for the analysis of dynamic load effects under correlated multiple excitations, e.g. wind effects, as this differs from conventional uni-component earthquake excitations. The wind loading input for this scheme may be derived either from multiple point synchronous scanning of pressures on building models or through high-frequency force balance (HFFB) measurements. The ESWL for a given peak response is expressed as a linear combination of the background and resonant loads, which respectively reflect the fluctuating wind load characteristics and inertial loads in fundamental modes of vibration. The nuances of utilizing HFFB measurements for tall buildings with 3D coupled mode shapes are elucidated with a focus on the evaluation of the generalized forces including mode shape corrections, the background and resonant responses, and the associated ESWLs. Utilizing a representative tall building with 3D mode shapes and closely spaced frequencies, the framework for the analysis of coupled dynamic load effects and modeling of 3D ESWLs is demonstrated. The significance of cross correlation of wind loads and the intermodal coupling of modal responses on the accurate prediction of coupled response is highlighted.
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