Abstract
Previous studies have shown that the integrated transfer function (ITF) is independent of turbulence characteristics
and can be effectively applied to predict the buffeting response of elongated structures, assuming that the strip hypothesis is
valid. However, existing research has not effectively identified the ITF through segment model vibration tests, and the influence
of the 3D effect on the accuracy of the strip hypothesis and the characteristics of the ITF in wind tunnel tests has not been
quantitatively studied. A segment model vibration measurement device that can change a test model's span-width ratio was
designed in this study. An airfoil section and a streamlined box girder section structure were taken as the background, and their
ITFs were effectively identified under different L/B (L denotes the turbulent integral scale and B denotes the structural width)
and model span-width ratios. The influence laws of the 3D effect on the accuracy of the strip hypothesis and ITF identification in
wind tunnel tests were systematically investigated. The results showed that L/B and the structural span-width ratio are two
significant controlling factors that affect the accuracy of the strip hypothesis and ITF identification. The research provides an
effective experimental method for accurately predicting the buffeting response of elongated structures based on ITFs identified
through segment model vibration tests.
Key Words
buffeting response; elongated structure; integrated transfer function; scale ratio; wind tunnel test
Address
Yi Su, Jin Di and Shaopeng Li:Key Laboratory of New Technology for Construction of Cities in Mountain Area, School of Civil Engineering,
Chongqing University, No. 83 Shabeijie, Shapingba, Chongqing 400045, China
Mingshui Li and Yang Yang:Research Centre for Wind Engineering, Southwest Jiaotong University, No. 111, Section 1, North 2nd Ring Road,
Chengdu 610031, Sichuan, China
Abstract
Wind turbines are usually steel hollow structures that can be vulnerable to dramatic failures due to high-intensity
wind (HIW) events, which are classified as a category of localized windstorms that includes tornadoes and downbursts.
Analyzing Wind Turbines (WT) under tornadoes is a challenging-to-achieve task because tornadoes are much more complicated
wind fields compared with the synoptic boundary layer wind fields, considering that the tornado's 3-D velocity components vary
largely in space. As a result, the supporting tower of the wind turbine and the blades will experience different velocities
depending on the location of the event. Wind farms also extend over a large area so that the probability of a localized windstorm
event impacting one or more towers is relatively high. Therefore, the built-in-house numerical code "HIW-WT" has been
developed to predict the straining actions on the blades considering the variability of the tornado's location and the blades' pitch
angle. The developed HIWWT numerical model incorporates different wind fields that were generated from developed CFD
models. The developed numerical model was applied on an actual wind turbine under three different tornadoes that have
different tornadic structure. It is found that F2 tornado wind fields present significant hazard for the wind turbine blades and
have to be taken into account if the hazardous impact of this type of unexpected load is to be avoided.
Address
Mohamed AbuGazia:1)State Key Laboratory for Disaster Mitigation in Civil Engineering, Tongji University, Shanghai, China 2)Department of Civil and Environmental Engineering, The University of Western Ontario, London, Ontario, Canada 3)5Structural Engineering Department, Faculty of Engineering, Ain Shams University, Cairo, Egypt
Ashraf El Damatty:1)Department of Civil and Environmental Engineering, The University of Western Ontario, London, Ontario, Canada
2)Department of Civil Engineering, Sichuan University, Chengdu, China
3)Wind Engineering, Energy and Environmental Research Institute (WindEEE), The University of Western Ontario, London, Ontario, Canada
Kaoshan Dai:Department of Civil Engineering, Sichuan University, Chengdu, China
Wensheng Lu:State Key Laboratory for Disaster Mitigation in Civil Engineering, Tongji University, Shanghai, China
Nima Ezami:Department of Civil and Environmental Engineering, The University of Western Ontario, London, Ontario, Canada
Abstract
This study is to investigate the effect of interference between two C-shaped high-rise buildings by computational
fluid dynamics (CFD), focusing on the variation of the local pressure coefficient (CP) and the mean pressure coefficient
(CPMEAN). Sixteen building position cases are considered for the present study. These cases were based on the position and height
of the interference building (IB). The pressure coefficient (CP) is calculated on the principal building (PB) and is compared with
an isolated building identical in shape and size. The interference effect on PB has also been presented in reference for the
interference factor (IF). According to the findings, the maximum force coefficient on the PB is 0.971 and it is 10.97% more than
the isolated PB when IB is located at position 2b (two times the width of the building), and the interfering height of 13H/15 mm.
The moment coefficient on PB is 1.27, which is 27.36% less than the isolated case in which IB pushed 2b to 3b in the y direction
with 750 mm height. In most of the cases, because of the shielding effect of the IB, the value of force coefficient (CF) on PB has
been reduced. On the face of the PB, there are also considerable differences in the mean pressure coefficient CPMEAN. When IB
was positioned at a location of 2b in Y direction and an interfering height of 13H/15 mm, the maximum CPMEAN (1.58) was
observed on the leeward face of PB.
Key Words
Computational fluid dynamics (CFD); interference effect; pressure coefficient; tall structure; wind force
Address
Himanshoo Verma and R. S. Sonparote:Department of Applied Mechanics, Visvesvaraya National Institute of Technology (VNIT) Nagpur, Maharashtra- 440010, India
Abstract
Accurate estimation of modal parameters (i.e., natural frequency, damping ratio) of tall buildings is of great
importance to their structural design, structural health monitoring, vibration control, and state assessment. Based on the
combination of variational mode decomposition, smoothed discrete energy separation algorithm-1, and Half-cycle energy
operator (VMD-SH), this paper presents a method for structural modal parameter estimation. The variational mode
decomposition is proved to be effective and reliable for decomposing the mixed-signal with low frequencies and damping ratios,
and the validity of both smoothed discrete energy separation algorithm-1 and Half-cycle energy operator in the modal
identification of a single modal system is verified. By incorporating these techniques, the VMD-SH method is able to accurately
identify and extract the various modes present in a signal, providing improved insights into its underlying structure and behavior.
Subsequently, a numerical study of a four-story frame structure is conducted using the Newmark-β method, and it is found that
the relative errors of natural frequency and damping ratio estimated by the presented method are much smaller than those by
traditional methods, validating the effectiveness and accuracy of the combined method for the modal identification of the multimodal system. Furthermore, the presented method is employed to estimate modal parameters of a full-scale tall building utilizing
acceleration responses. The identified results verify the applicability and accuracy of the presented VMD-SH method in field
measurements. The study demonstrates the effectiveness and robustness of the proposed VMD-SH method in accurately
estimating modal parameters of tall buildings from acceleration response data.
Key Words
damping ratio; energy separation algorithm; modal parameter identification; natural frequency; variational mode
decomposition
Address
Kang Cai:Institute of Structural Engineering, College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058,
P.R. China Center for Balance Architecture, Zhejiang University, Hangzhou 310058, P.R. China
Mingfeng Huang:Institute of Structural Engineering, College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058,
P.R. China Center for Balance Architecture, Zhejiang University, Hangzhou 310058, P.R. China
Xiao Li:Department of Civil, Chemical and Environmental Engineering, Polytechnic School,
University of Genova, via Montallegro 1, 16145 Genova, Italy
Haiwei Xu:Institute of Structural Engineering, College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, P.R. China
Binbin Li:College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, P.R. China; ZJU-UIUC Institute, Zhejiang University, Haining 314400, China
Chen Yang:Institute of Structural Engineering, College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058,
P.R. China Center for Balance Architecture, Zhejiang University, Hangzhou 310058, P.R. China
Abstract
The main objective of this study was to establish design guidelines for three key design variables (spar thickness,
spar diameter, and total draft) by examining their impact on the stress distribution and resonant frequency of a 2.5-MW spar-type
floating offshore wind turbine substructure under extreme marine conditions, such as during Typhoon Bolaven. The current
findings revealed that the substructure experienced maximum stress at wave frequencies of either 0.199 Hz or 0.294 Hz,
consistent with previously reported experimental findings. These results indicated that the novel simulation method proposed in
this study, which simultaneously combines hydrodynamic diffraction analysis, computational dynamics analysis, and structural
analysis, was successfully validated. It also demonstrated that our proposed simulation method precisely quantified the stress
distribution of the substructure. The novel findings, which reveal that the maximum stress of the substructure increases with an
increase in total draft and a decrease in spar thickness and spar diameter, offer valuable insights for optimizing the design of
spar-type floating offshore wind turbine substructures operating in various harsh marine environments.
