Abstract
Multiple studies conducted in the past evaluated the conductor response under one tornado wind field, while the
performance of transmission lines under different tornado wind fields still remains unknown. Thus, the objective of this paper is
to estimate the variation in the conductor'scritical longitudinal and transverse reactions under different tornado wind fields, as
well as providing the corresponding critical tornado configurations. The considered full-scale tornadoes are the Spencer, South
Dakota, 1998, the Stockton, Kansas, 2005 and the Goshen County, Wyoming, 2009. Computational Fluid Dynamics (CFD)
simulations were previously conducted to develop these wind fields. All tornadoes have been rescaled to have a common
velocity matching the upper limit of the F2 Fujita scale. Eight conductor systems, each including six spans, are considered in this
paper. For each conductor, parametric studies are conducted by varying the location of the three tornado wind fields relative to
the tower of interest, therefore the peak reactions associated with each tornado are determined. A semi-analytical closed-form
solution, previously developed and validated, is used to calculate the reactions. The study conducted in this paper can be divided
into two parts: In the first part, a parametric study considering a wide range of tornado locations is conducted. In the second part,
the parametric study focuses on the tornado location leading to the critical tangential velocity on the tower. Based on this
extensive parametric study, a critical tornado defined as the Design Tornado and its critical locations, tornado distance R = 125
m, tornado angle Θ=15° and 30°, are recommended for design purposes.
Key Words
conductor; critical tornado load cases; longitudinal force; tornado; transmission line system
Address
Dingyu Yao:Research Centre for Wind Engineering, Southwest Jiaotong University, Chengdu, China
Ashraf El Damatty:1)Research Centre for Wind Engineering, Southwest Jiaotong University, Chengdu, China
2)Key Laboratory for Wind Engineering of Sichuan Province, Chengdu, China
Nima Ezami:Research Centre for Wind Engineering, Southwest Jiaotong University, Chengdu, China
Abstract
This work investigates the subcritical free-shear prism wake at Re=22,000 by the Koopman analysis using the
Dynamic Mode Decomposition (DMD) algorithm. The Koopman model linearized nonlinearities in the stochastic,
homogeneous anisotropic turbulent wake, generating temporally orthogonal eigen tuples that carry meaningful, coherent
structures. Phenomenological analysis of dominant modes revealed their physical interpretations: Mode 1 renders the mean-field
dynamics, Modes 2 describes the roll-up of the Strouhal vortex, Mode 3 describes the Bloor-Gerrard vortex resulting from the
Kelvin-Helmholtz instability inside shear layers, its superposition onto the Strouhal vortex, and the concurrent flow entrainment,
Modes 6 and 10 describe the low-frequency shedding of turbulent separation bubbles (TSBs) and turbulence production,
respectively, which contribute to the beating phenomenon in the lift time history and the flapping motion of shear layers, Modes
4, 5, 7, 8, and 9 are the relatively trivial harmonic excitations. This work demonstrates the Koopman analysis' ability to provide
insights into free-shear flows. Its success in subcritical turbulence also serves as an excellent reference for applications in other
nonlinear, stochastic systems.
Key Words
dynamic mode decomposition; Koopman analysis; large eddy simulation; prism wake; reduced-order modelling
Address
Cruz Y. Li and Tim K.T. Tse:1)Department of Civil Engineering, Chongqing University, Chongqing, China
2)Department of Civil and Environmental Engineering, the Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong
SAR, China
Xisheng Lin, Lei Zhou and Yunfei Fu:Department of Civil and Environmental Engineering, the Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong
SAR, China
Gang Hu:School of Civil and Environmental Engineering, Harbin Institute of Technology, Shenzhen, 518055, China
Abstract
To investigate the non-Gaussian feature of fluctuating wind pressures on rectangular high-rise buildings, wind
tunnel tests were conducted on scale models with side ratios ranging from 1/9~9 in an open exposure for various wind
directions. The high-order statistical moments, time histories, probability density distributions, and peak factors of pressure
fluctuations are analyzed. The mixed normal-Weibull distribution, Gumbel-Weibull distribution, and lognormal-Weibull
distribution are adopted to fit the probability density distribution of different non-Gaussian wind pressures. Zones of Gaussian
and non-Gaussian are classified for rectangular buildings with various side ratios. The results indicate that on the side wall, the
non-Gaussian wind pressures are related to the distance from the leading edge. Apart from the non-Gaussianity in the separated
flow regions noted by some literature, wind pressures behind the area where reattachment happens present non-Gaussian nature
as well. There is a new probability density distribution type of non-Gaussian wind pressure which has both long positive and
negative tail found behind the reattachment regions. The correlation coefficient of wind pressures is proved to reflect the nonGaussianity and a new method to estimate the mean reattachment length of rectangular high-rise building side wall is proposed
by evaluating the correlation coefficient. For rectangular high-rise buildings, the mean reattachment length calculated by the
correlation coefficient method along the height changes in a parabolic shape. Distributions of Gaussian and non-Gaussian wind
pressures vary with side ratios. It is inappropriate to estimate the extreme loads of wind pressures using a fixed peak factor. The
trend of the peak factor with side ratios on different walls is given.
Key Words
non-Gaussian feature; peak factor; probability density distribution; rectangular high-rise buildings; side ratio; wind
tunnel test
Address
Jia-hui Yuan, Shui-fu Chen and Yi Liu:Institute of Structural Engineering, Zhejiang University, Hangzhou, China
Abstract
This study analyzes the response of a tall building with an H-shaped cross-section when subjected to wind loading
generated by the same H-shape. As normative standards usually adopt regular geometries for determining the wind loading, this
paper shows unpublished results which compares results of the dynamic response of H-shaped buildings with the response of
simplified section buildings. Computational Fluid Dynamics (CFD) is employed to determine the steady wind load on the Hshaped building. The CFD models are validated by comparison with wind tunnel test data for the k-ε and k-ω models of
turbulence. Transient wind loading is determined using the Synthetic Wind Method. A new methodology is presented that
combines Stochastic and CFD methods. In addition, time-history dynamic structural analysis is performed using the HHT
method for a period of 60 seconds on finite element models. First, the along-wind response is studied for wind speed variations.
The wind speeds of 28, 36, 42, and 50 m/s at 0° case are considered. Subsequently, the dynamic response of the building is
studied for wind loads at 0°, 45°, and 90° with a wind speed of 42 m/s, which approximates the point of resonance between gusts
of wind and the structure. The response values associated with the first two directions for the H-shaped building are smaller than
those for the R-shaped (Equivalent Rectangular Shape) one. However, the displacements of the H-shaped building associated
with the latter wind load are larger.
Key Words
dynamic analysis of tall building; H-shaped cross-section building; synthetic wind method; wind loading
Address
Lucas Willian Aguiar Mattias:1)Graduate Program in Civil Engineering, Federal University of Technology of Parana, Curitiba, Brazil
2)Infrastructure Department, Federal Institute of Rondonia, Porto Velho, Brazil
Joao Elias Abdalla Filho:Graduate Program in Civil Engineering, Federal University of Technology of Parana, Curitiba, Brazil
Abstract
In this paper, the wind-induced response of Jiayuguan wooden building (world cultural heritage) in Northwest
China was studied. ANSYS finite element software was used to establish four kinds of building models under different working
conditions and carry out modal analysis. The simulation results were compared with the field dynamic test results, obtaining the
model which reflects the real vibration characteristics of the wooden tower. Time history data of fluctuating wind speed was
obtained by MATLAB programming. Time domain method and ANSYS were used to analyze the wind-induced vibration
response time history of Jiayuguan wooden building, obtaining the displacement time history curve of the structure. It was
suggested that the wind-induced vibration coefficient of Jiayuguan wooden building is 1.76. Through analysis of the
performance of the building under equivalent static wind load, the maximum displacement occurs in the three-story wall, gold
column and the whole roof area, and the maximum displacement of the building is 5.39 cm. The ratio of the maximum stress
value to the allowable value of wood tensile strength is 45 %. The research results can provide reference for the wind resistant
design and protection of ancient buildings with similar structure to Jiayuguan wooden tower.
Key Words
ancient wooden building; wind-induced response; finite element simulation; wind-induced vibration coefficient
Address
Teng Y. Xue:1)1School of Architecture, Tianjin University, Tianjin 300072, China 2)4School of Transportation Engineering, Hunan Institute of Traffic Engineering, Hunan 421001, China
Hong B. Liu:School of Civil Engineering, Hebei University of Engineering, Hebei 056038, China
Ting Zhou:School of Architecture, Tianjin University, Tianjin 300072, China
Xin C. Chen:Jiayuguan Silk Road Culture Research Institute (Great Wall), Gansu 735100, China
Xiang Zhang:Jiayuguan Silk Road Culture Research Institute (Great Wall), Gansu 735100, China
Zhi P. Zou:School of Transportation Engineering, Hunan Institute of Traffic Engineering, Hunan 421001, China
