Abstract
In order to effectively simulate nonstationary stochastic turbulent wind fields, four separation hybrid (SEP-H)
models are proposed in the present study. Based on the assumption that the lateral turbulence component at one single-point is
uncorrelated with the longitudinal and vertical turbulence components, the fluctuating wind is separated into 2nV-1D and nV1D nonstationary stochastic vector processes. The first process can be expressed as double proper orthogonal decomposition
(DPOD) or proper orthogonal decomposition and spectral representation method (POD-SRM), and the second process can be
expressed as POD or SRM. On this basis, four SEP-H models of nonstationary stochastic turbulent wind fields are developed. In
addition, the orthogonal random variables in the SEP-H models are presented as random orthogonal functions of elementary
random variables. Meanwhile, the number theoretical method (NTM) is conveniently adopted to select representative points set
of the elementary random variables. The POD-FFT (Fast Fourier transform) technique is introduced in frequency to give full
play to the computational efficiency of the SEP-H models. Finally, taking a long-span bridge as the engineering background, the
SEP-H models are compared with the dimension-reduction DPOD (DR-DPOD) model to verify the effectiveness and
superiority of the proposed models.
Key Words
double proper orthogonal decomposition; nonstationary stochastic turbulent wind; POD-FFT technique; random
orthogonal function; Separation Hybrid (SEP-H) Models
Address
Long Yan, Zhangjun Liu, Xinxin Ruan and Bohang Xu:School of Civil Engineering and Architecture, Wuhan Institute of Technology, Wuhan 430074, P.R. China
Abstract
A flexible-base coupled-two-beam (CTB) discrete model with equivalent tuned mass dampers is used to assess the
effect of soil-structure interaction (SSI) and different types of lateral resisting systems on the design of passive dynamic
absorbers (PDAs) under the action of along-wind and across-wind loads due to vortex shedding. A total of five different PDAs
are considered in this study: (1) tuned mass damper (TMD), (2) circular tuned sloshing damper (C-TSD), (3) rectangular tuned
sloshing damper (R-TSD), (4) two-way liquid damper (TWLD) and (5) pendulum tuned mass damper (PTMD). By modifying
the non-dimensional lateral stiffness ratio, the CTB model can consider lateral deformations varying from those of a flexural
cantilever beam to those of a shear cantilever beam. The Monte Carlo simulation method was used to generate along-wind and
across-wind loads correlated along the height of a real shear wall-frame building, which has similar fundamental periods of
vibration and different modes of lateral deformation in the xz and yz planes, respectively. Ambient vibration tests were conducted
on the building to identify its real lateral behavior and thus choose the most suitable parameters for the CTB model. Both alongwind and across-wind responses of the 144-meter-tall building were computed considering four soil types (hard rock, dense soil,
stiff soil and soft soil) and a single PDA on its top, that is, 96 time-history analyses were carried out to assess the effect of SSI
and lateral resisting system on the PDAs design. Based on the parametric analyses, the response significantly increases as the
soil flexibility increases for both type of lateral wind loads, particularly for flexural-type deformations. The results show a great
effectiveness of PDAs in controlling across-wind peak displacements and both along-wind and across-wind RMS accelerations,
on the contrary, PDAs were ineffective in controlling along-wind peak displacements on all soil types and different kind of
lateral deformation. Generally speaking, the maximum possible value of the PDA mass efficiency index increases as the soil
flexibility increases, on the contrary, it decreases as the non-dimensional lateral stiffness ratio of the building increases;
therefore, there is a significant increase of the vibration control effectiveness of PDAs for lateral flexural-type deformations on
soft soils.
Key Words
across-wind loads; along-wind loads; pendulum tuned mass dampers; shear wall-frame buildings; soil-structure
interaction; tuned liquid dampers; tuned mass dampers
Address
Ivan F. Huergo:School of Engineering and Technologies, Universidad de Monterrey, San Pedro Garza Garcia, Mexico
Hugo Hernandez-Barrios:School of Engineering, Universidad Michoacana de San Nicolas de Hidalgo, Morelia, Mexico
Roberto Gomez-Martinez:Institute of Engineering, Universidad Nacional Autónoma de México, Mexico City, Mexico
Abstract
To ensure the flutter stability of three-tower suspension bridges under skew wind, by using the computational
procedure of 3D refined flutter analysis of long-span bridges under skew wind, in which structural nonlinearity, the static wind
action(also known as the aerostatic effect) and the full-mode coupling effect etc., are fully considered, the flutter stability of a
three-tower suspension bridge-the Taizhou Bridge over the Yangtze River in completion and during the deck erection is
numerically investigated under the constant uniform skew wind, and the influences of skew wind and aerostatic effects on the
flutter stability of the bridge under the service and construction conditions are assessed. The results show that the flutter critical
wind speeds of three-tower suspension bridge under service and construction conditions fluctuate with the increase of wind yaw
angle instead of a monotonous cosine rule as the decomposition method proposed, and reach the minimum mostly in the case of
skew wind. Both the skew wind and aerostatic effects significantly reduce the flutter stability of three-tower suspension bridge
under the service and construction conditions, and the combined skew wind and aerostatic effects further deteriorate the flutter
stability. Both the skew wind and aerostatic effects do not change the evolution of flutter stability of the bridge during the deck
erection, and compared to the service condition, they lead to a greater decrease of flutter critical wind speed of the bridge during
deck erection, and the influence of the combined skew wind and aerostatic effects is more prominent. Therefore, the skew wind
and aerostatic effects must be considered accurately in the flutter analysis of three-tower suspension bridges.
Key Words
aerostatic effect; deck erection; flutter stability; service condition; skew wind; three-tower suspension bridges
Address
Xinjun Zhang:1)College of Civil Engineering, Zhejiang University of Technology, Hangzhou, 310023, P.R. China
2)Key Laboratory of Civil Engineering Structures & Disaster Prevention and Mitigation Technology of Zhejiang Province,
Hangzhou, 310023, P.R. China
Xuan-Rui Pan, Yuhan Leng and Bingze Chen:College of Civil Engineering, Zhejiang University of Technology, Hangzhou, 310023, P.R. China
Abstract
Large Eddy Simulation (LES) is used to explore the influence of vibration frequency and amplitude on the
aerodynamic performance of a rectangular cylinder with an aspect ratio of B/D=5 (B: breadth; D: depth of cylinder) at a
Reynolds number of 22,000 near resonance frequency. In smooth flow conditions, the research employs a sequence of
three-dimensional simulations under forced vibration with diverse frequency ratios fe / fo = 0.8-1.2 (fe : oscillation
frequency; fo : Strouhal frequency when the rectangular cylinder is stationary ) and oscillation amplitudes Ah/D = 0.05 -
0.3. The individual influences of fe / fo and Ah/D on the characteristics of integrated and distributed aerodynamic forces are
the focal points of discussion. For the integrated aerodynamic force, particular emphasis is placed on the analysis of the
dependence of velocity-proportional component C1 and displacement-proportional component C2 of unsteady
aerodynamic force on amplitude and frequency ratio. Near the resonance frequency, the dependencies of C1 and C2 on
amplitude are stronger than that of frequency ratio. For the distributed aerodynamic force, the increase in frequency and
amplitude promotes the position of the main vortex core and reattachment to the leading edge in the streamwise direction.
In the spanwise direction, vibration enhances the spanwise correlation of aerodynamic force to weaken the threedimensional effect of the flow field, and a lower frequency ratio and larger amplitude amplify this effect.
Key Words
forced vibration; large eddy simulation; phase angle; spanwise correlation; unsteady aerodynamic force
Address
Pengcheng Zou:State Key Lab of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China
Shuyang Cao and Jinxin Cao:1)State Key Lab of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China
2)Key Laboratory of Transport Industry of Wind Resistant Technology for Bridge Structures, Tongji University, Shanghai 200092, China
Abstract
Reliable wind signal reconstruction can be beneficial to the operational safety of long-span bridges. NonGaussian characteristics of wind signals make the reconstruction process challenging. In this paper, non-Gaussian wind signals
are converted into a combined prediction of two kinds of features, actual wind speeds and wind angles of attack. First, two
decomposition techniques, empirical mode decomposition (EMD) and variational mode decomposition (VMD), are introduced
to decompose wind signals into intrinsic mode functions (IMFs) to reduce the randomness of wind signals. Their principles and
applicability are also discussed. Then, four artificial intelligence (AI) algorithms are utilized for wind signal reconstruction by
combining the particle swarm optimization (PSO) algorithm with back propagation neural network (BPNN), support vector
regression (SVR), long short-term memory (LSTM) and bidirectional long short-term memory (Bi-LSTM), respectively.
Measured wind signals from a bridge site in a deep-cutting gorge are taken as experimental subjects. The results showed that the
reconstruction error of high-frequency components of EMD is too large. On the contrary, VMD fully extracts the multiscale
rules of the signal, reduces the component complexity. The combination of VMD-PSO-Bi-LSTM is demonstrated to be the most
effective among all hybrid models.
Address
Zhen Wang:School of Civil Engineering, Tianjin University, Tianjin, 300072, P.R. China
Jinsong Zhu:1)School of Civil Engineering, Tianjin University, Tianjin, 300072, P.R. China
2)Key Laboratory of Coast Civil Structure Safety of Ministry of Education, School of Civil Engineering, Tianjin University, Tianjin, 300072, P.R. China
Ziyue Lu:Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim, 7491, Norway
Zhitian Zhang:College of Civil Engineering and Architecture, Hainan University, Haikou, 570228, P.R. China
