Abstract
This study proposed the mode shape correction formulae for the high frequency force balance technique. The presented formulae respectively give the mode shape for translational modes and torsional modes, meaning that there is no need to distinguish the traditionally concerned along wind case and cross-wind case anymore. This treatment makes the mode shape correction much simpler especially when wind blows to a building obliquely. Comparison with some experimental results of other researchers shows the reliability of the proposed formulae. The mode coupling effect is also analyzed and discussed through an actual super-tall building, the Guangzhou East Tower. The results show that the mode shape coupling effect is significant and cannot be ignored.
Highlights
The high-frequency force balance technique (HFFB) was firstly introduced by Tschanz and Davenport (1983) for the measurements of wind effects on tall buildings [1], and it has become one of the standard wind-tunnel methods by which overall wind loads and responses such as accelerations, displacements and velocities are determined for tall buildings at the design stage [2,3,4]
Researchers have noticed that the linear modal shape assumption in the classic HFFB technique has been facing a challenge: the structural systems of modern super-tall buildings are becoming more and more complex due to their innovative architectural and structural design; the mode shape of these modern super-tall buildings might not be approximately linear with the height anymore
It can be seen that the torsional mode shape correction factor given by this study is closer to the experimental results, which demonstrates the applicability of Eq (20)
Summary
The high-frequency force balance technique (HFFB) was firstly introduced by Tschanz and Davenport (1983) for the measurements of wind effects on tall buildings [1], and it has become one of the standard wind-tunnel methods by which overall wind loads and responses such as accelerations, displacements and velocities are determined for tall buildings at the design stage [2,3,4]. By assuming the fundamental mode shape of a super-tall building being linear with height, the HFFB technique allows users obtaining the modal force for the first three modes from the measured horizontal force, overturning moments and torsion at the base of building model. The linear mode shape assumption of the classic HFFB technique may not be suitable for these super-tall buildings, and the classic HFFB-based data analysis method needs the so-called mode shape correction. An iconic super-tall building, the Guangzhou East Tower (GZET), is taken as an example to show the effectiveness of the proposed mode shape correction factors and discuss the mode coupling effect. The GZET could endure wind effects induced by typhoons and can be regarded as ideal examples for investigating typhoon effects on super-tall buildings.
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