Abstract
Widespread damages from extreme winds have attracted lots of attentions of the resilience assessment of power
distribution systems. With many related environmental parameters as well as numerous power infrastructure components, such
as poles and wires, the increased challenge of power asset management before, during and after extreme events have to be
addressed to prevent possible cascading failures in the power distribution system. Many extreme winds from weather events,
such as hurricanes, generate widespread damages in multiple areas such as the economy, social security, and infrastructure
management. The livelihoods of residents in the impaired areas are devastated largely due to the paucity of vital utilities, such as
electricity. To address the challenge of power grid asset management, power system clustering is needed to partition a complex
power system into several stable clusters to prevent the cascading failure from happening. Traditionally, system clustering uses
the Binary Decision Diagram (BDD) to derive the clustering result, which is time-consuming and inefficient. Meanwhile, the
previous studies considering the weather hazards did not include any detailed weather-related meteorologic parameters which is
not appropriate as the heterogeneity of the parameters could largely affect the system performance. Therefore, a fragility-based
network hierarchical spectral clustering method is proposed. In the present paper, the fragility curve and surfaces for a power
distribution subsystem are obtained first. The fragility of the subsystem under typical failure mechanisms is calculated as a
function of wind speed and pole characteristic dimension (diameter or span length). Secondly, the proposed fragility-based
hierarchical spectral clustering method (F-HSC) integrates the physics-based fragility analysis into Hierarchical Spectral
Clustering (HSC) technique from graph theory to achieve the clustering result for the power distribution system under extreme
weather events. From the results of vulnerability analysis, it could be seen that the system performance after clustering is better
than before clustering. With the F-HSC method, the impact of the extreme weather events could be considered with topology to
cluster different power distribution systems to prevent the system from experiencing power blackouts.
Key Words
fragility curve; hierarchical spectral clustering; hurricane hazard; power distribution system; reliability model
Address
Jintao Zhang, Wei Zhang, William Hughes and Amvrossios C. Bagtzoglou: Department of Civil Engineering, University of Connecticut, Storrs, Connecticut 06269, U.S.A.
Abstract
In this paper, detailed wind field data of the full path of typhoon "Bailu" were obtained based on site measurements.
Typhoon "Bailu" made first landfall southeast of the Taiwan Strait with a wind speed of approximately 30 m/s near the center of
the typhoon eye and a second landfall in Dongshang County in Fujian Province. The moving process is classified into 3 regions
for analysis and comparison. Detailed analyses of wind characteristics including wind profile, turbulence intensity, gust factor,
turbulence integral scale and wind power spectral density function at the full process of the typhoon are conducted, and the
findings are presented in this paper. Wind speed shows significant dependence on both the direction of the moving path and the
distance between the typhoon center and measurement site. Wind characteristics significantly vary with the moving path of the
typhoon center. The relationship between turbulence intensity and gust factor at different regions is investigated. The integral
turbulence scales and wind speed are fitted by a Gaussian model. Such analysis and conclusions may provide guidance for future
bridge wind-resistant design in engineering applications.
Key Words
typhoon "Bailu"; wind-resistant engineering design; wind characteristics; wind field measurement
Address
Dandan Xia:Fujian Provincial Key Laboratory of Wind Disaster and Wind Engineering, Xiamen University of Technology,
No.600 Ligong Road, Jimei District, Xiamen, 361024, China
Li Lin:Fujian Provincial Key Laboratory of Wind Disaster and Wind Engineering, Xiamen University of Technology,
No.600 Ligong Road, Jimei District, Xiamen, 361024, China
Liming Dai:Department of Industrial Systems Engineering, University of Regina, 3737 Wascana Parkway, Regina, SK, S4S 0A2SK S4S0A2, Canada
Xiaobo Lin:Department of Civil Engineering, Fuzhou University, No.2 Wulongjiang North Road, Fuzhou, 350108, China
Abstract
This paper examines the flow characteristics around an inclined prism with a U-shaped cross-section ("U-profile")
and investigates the connection between the flow and flow-induced vibrations. The study employs a combined approach that
involves wind tunnel experiments and computational fluid dynamics (CFD) using an unsteady Reynolds-averaged NavierStokes (RANS) turbulence model. Distinct vortex formation patterns are observed in the flow field surrounding the stationary
inclined profile. When the cavity of the profile faces away from the incoming flow, large vortices develop behind the profile.
Conversely, when the cavity is oriented towards the oncoming flow, these vortices form within the cavity. Notably, due to the
slow movement of these large vortices through the cavity, the frequency at which vortices are shed in the negative inclination
case is lower compared to the positive inclination, where they form in the wake. Wind tunnel experiments reveal an intermittent
transition between the two vortex formation patterns at zero inclination. Large vortices sporadically emerge both in the cavity
and behind the profile. The simulation results demonstrate that when these large vortices occur at a frequency close to the
structure's natural frequency, they induce prominent pitch vibrations. This phenomenon is also sought after and presented in
coupled vibration experiments. Additionally, the simulations indicate that when the natural frequency of the structure is
considerably lower than the vortex shedding frequency, this type of vibration can be observed.
Key Words
bluff body; flow pattern; particle image velocimetry; U-profile; unsteady RANS; vortex shedding frequency
Address
Johannes Strecha:TU Wien, Inst Fluid Mech and Heat Transfer, Getreidemarkt 9, 1060 Vienna, Austria
Stanislav Pospíšil :Inst Theoret & Appl Mech of the Czech Acad Sci, Prosecka 76, 190 00 Prague, Czech Republic
Herbert Steinrück:TU Wien, Inst Fluid Mech and Heat Transfer, Getreidemarkt 9, 1060 Vienna, Austria
Abstract
Pounding of structures may result in considerable damages, to the extent of total failure during severe lateral loading
events (e.g., earthquakes and wind). With the new generation of tall buildings in densely occupied locations, wind-induced
pounding becomes of higher risk due to such structures's large deflections. This paper aims to develop mathematical formulations
to determine the maximum pounding force when two adjacent structures come into contact. The study will first investigate
wind-induced pounding forces of two equal-height structures with similar dynamic properties. The wind loads will be extracted
from the Large Eddy Simulation models and applied to a Finite Element Method model to determine deflections and pounding
forces. A Genetic Algorithm is lastly utilized to optimize fitting parameters used to correlate the maximum pounding force to the
governing structural parameters. The results of the wind-induced pounding show that structures with a higher natural frequency
will produce lower maximum pounding forces than those of the same structure with a lower natural frequency. In addition, taller
structures are more susceptible to stronger pounding forces at closer separation distances. It was also found that the complexity
of the mathematical formula from optimization depends on achieving a more accurate mapping for the trained database.
Key Words
Computational Fluid Dynamics (CFD); Finite Element Method (FEM); structural dynamics; structural pounding;
tall buildings; wind-induced deflection
Address
Tristen Brown:Department of Civil Engineering, Lakehead University, 955 Oliver Rd, Thunder Bay, ON P7B 5E1, Thunder Bay, Canada
Ahmed Elshaer:Department of Civil Engineering, Lakehead University, 955 Oliver Rd, Thunder Bay, ON P7B 5E1, Thunder Bay, Canada
Anas Issa:Department of Civil Engineering, United Arab Emirates University, United Arab Emirates, Abu Dhabi
Abstract
The wind-resistant performance of bridges is generally evaluated based on the strip assumption. For the arch rib of
arch bridges, the situation is different due to the curve axis and the variable cross-sectional size. In the construction stage, the
arch rib supported by a cable system exhibits flexible dynamic characteristics, and the wind-resistant performance attracts
specially attention. To evaluate the wind-induced vibration of an arch rib with the maximum cantilever state, the finite element
model was established to compute the structural dynamic characteristics. Then, a three-dimensional (3D) fluid-solid coupling
analysis method was realized. After verifying the reliability of the method based on a square column, the wind-induced vibration
of the arch rib was computed. The vortex-induced vibration (VIV) performance of the arch rib was focused and the flow field
characteristics were discussed to explain the VIV phenomenon. The results show that the arch rib with the maximum cantilever
state had the possibility of VIV at high wind speeds but the galloping was not observed. The lock-in wind speeds were larger
than the results based on the strip assumption. Due to the vibration of arch rib, the frequency of shedding vortices along the arch
axis trended to be uniform.
Key Words
arch rib; the maximum cantilever state; dynamic characteristics; flow field characteristics; vortex-induced
vibration
Address
Hang Zhang:1)Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, P. R. China
2)ChengDu Municipal Waterworks CO., LTD, Chengdu 610000, P. R. China
Zilong Gao:Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, P. R. China
Haojun Tang:1)Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, P. R. China
2)State Key Laboratory of Bridge Intelligent and Green Construction, Southwest Jiaotong University, Chengdu 611756, P. R. China
Yongle Li:1)Department of Bridge Engineering, Southwest Jiaotong University, Chengdu 610031, P. R. China
2)State Key Laboratory of Bridge Intelligent and Green Construction, Southwest Jiaotong University, Chengdu 611756, P. R. China
