Physics-Based Method for the Removal of Spurious Resonant Frequencies in High-Frequency Force Balance Tests
Publication: Journal of Structural Engineering
Volume 142, Issue 2
Abstract
The high-frequency force balance (HFFB) test is a widely used method for estimating lateral turbulent wind loads on tall buildings in a wind tunnel. The method relies on use of a highly accurate force sensor placed at the base of the tall building model to measure base forces and overturning moments. Because the turbulent wind load excitation is broadband, it is important to adequately design the connection detail between the model and the sensor. Accurate design is needed to avoid contaminating the measurement of the lateral wind loads by the potential spurious resonant effect, which is induced by flexibility in the connection detail. This design often relies on the experience of the wind tunnel modeler. On occasion, because of the limitations of test setup and environment, the connection detail between the building model and the HFFB force sensor may not be sufficiently stiff. Consequently, resonant response caused by the flexible connection may affect the power spectral density function of the measured wind loads. One of the methods to address this problem is to filter the HFFB output signal and to remove undesirable response within a specific frequency interval by conventional digital filter methods. However, this may cause the removal of important features of the wind loading. This paper presents a simple yet efficient method, based on classical dynamic theory, to eliminate the spurious effect. The method is applied to the “correction” of an experimental wind load spectrum.
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Acknowledgments
Mr. Kurt Braun, Department of Civil and Environmental Engineering of NEU, is gratefully acknowledged for fabrication of the wind tunnel setup and for assistance during experiments. Mr. Jonathan Doughty, Department of Mechanical and Industrial Engineering of NEU, is acknowledged for 3D printing and model fabrication. Messrs. David Abati and Darren Vokes of NEU’s Carpentry Department are gratefully acknowledged for the construction and assembly of the test chamber. Professor Jerome F. Hajjar and the Department of Civil and Environmental Engineering are gratefully acknowledged for their collaboration with the sensor equipment. Finally, the authors would like to thank the Department of Mechanical and Industrial Engineering of NEU for the shared use of wind tunnel facility. This paper is based on work supported by the National Science Foundation (NSF) of the United States under CAREER Award CMMI-0844977. Any opinions, findings and conclusions or recommendations are those of the authors and do not necessarily reflect the views of the NSF.
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© 2015 American Society of Civil Engineers.
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Received: Oct 18, 2014
Accepted: Aug 11, 2015
Published online: Sep 10, 2015
Published in print: Feb 1, 2016
Discussion open until: Feb 10, 2016
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