Article
Engineering, Mechanical
Xin Li, Shaopeng Li, JingYang Li, Yi Su
Summary: This study conducted a pressure measurement test on a rigid segment model under a downburst-like wind to investigate the characteristics of downburst-like wind fields and wind loads. The results showed that the downburst-like wind, wind loads, and evolution power spectrum density (EPSD) exhibited time evolution features, transient effects, and nonstationary time-varying characteristics. The study also estimated the time-varying extreme values of nonstationary random processes and provided corresponding peak factors based on the generalized extreme value (GEV) distribution theory. The fitting accuracy of the GEV distribution was found to be good, and the calculated peak factors of wind pressure and aerodynamic lift were higher than those of wind speed.
PROBABILISTIC ENGINEERING MECHANICS
(2022)
Article
Engineering, Mechanical
Yi-Ming Zhang, Zifeng Huang, Yong Xia
Summary: Obtaining accurate evolutionary spectrum and time-varying coherence for multivariate nonstationary processes is important in engineering applications. However, estimating the time-varying coherence is challenging and has been rarely studied for a single realization of a nonstationary process. To address this issue, an improved multi-taper S-transform (MTST) method is proposed, which reduces the variance of the estimates with a sufficient time-frequency resolution. The technique uses different number of tapers at each frequency to achieve a trade-off between resolution and variance.
MECHANICAL SYSTEMS AND SIGNAL PROCESSING
(2023)
Article
Optics
Jyrki Laatikainen, Matias Koivurova, Jari Turunen, Tero Setaelae, Ari T. Friberg
Summary: In this study, a method for transforming scalar, pulsed, isodiffracting light beams into nonstationary secondary sources exhibiting cross-spectral purity or spectral invariance is presented. Additionally, hybrid refractive-diffractive imaging systems are introduced to accurately perform the desired transformation over a wide spectral range.
Article
Engineering, Mechanical
Changda Feng, Xinzhong Chen
Summary: This study investigated the uncoupled crosswind and alongwind responses of base-isolated tall buildings under nonstationary wind excitations, using the Bouc-Wen model and evolutionary power spectra for modeling, conducting response time-history analysis, and proposing a method to understand the nonstationary time-varying response statistics.
JOURNAL OF ENGINEERING MECHANICS
(2021)
Article
Engineering, Civil
Pengcheng Xu, Dong Wang, Yuankun Wang, Jianchun Qiu, Vijay P. Singh, Xiaopei Ju, Along Zhang, Jichun Wu, Changsheng Zhang
Summary: This study conducted multivariate nonstationary hazard assessment of annual extreme rainfall events in the Haihe River basin, China, revealing nonstationarity in some stations and showing that the nonstationarity of dependence structure has a smaller impact on the estimation of design quantiles based on reliability levels, but adds more uncertainty to the estimation of hydrologic design quantiles.
JOURNAL OF HYDROLOGY
(2021)
Article
Engineering, Civil
Zifeng Huang, You-Lin Xu, Sheng Zhan
Summary: The study proposes a conditional simulation method for multivariate nonstationary typhoon winds with time-varying coherences for long-span bridges. The square root decomposition is found to be appropriate for decomposing the spectrum matrix with time-varying coherences. The proposed conditional simulation method is validated by comparing the simulated typhoon wind time histories with the measured ones, showing that it can provide a better typhoon wind field than the unconditional simulation method.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2021)
Article
Construction & Building Technology
Liang Hu, Ahsan Kareem
Summary: This paper presents a method to estimate the evolutionary power spectral density of non-stationary winds, providing a unified formulation. The method allows for adjustable time and frequency resolution to reduce errors, and can be applied to different time-frequency analysis tools.
ADVANCES IN STRUCTURAL ENGINEERING
(2022)
Article
Optics
Jyrki Laatikainen, Meilan Luo, Atri Halder, Matias Koivurova, Tero Setala, Jari Turunen, Ari T. Friberg
Summary: This paper examines the cross-spectral purity of random and nonstationary scalar light fields with arbitrary spectral bandwidth. It introduces a reduction formula based on time-integrated coherence functions to ensure cross-spectral purity of interfering fields with identical normalized spectra. The analysis is conducted using all-reflective wavefront-shearing interferometers, which overcome problems associated with Young's interferometer commonly used to assess cross-spectral purity. The study demonstrates that any partially coherent beam can be transformed into a locally cross-spectrally pure beam with specular cross-spectral density, while lack of space-frequency coupling ensures cross-spectral purity in the global sense across an entire transverse plane, irrespective of spectral bandwidth or pulse shape.
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION
(2023)
Article
Construction & Building Technology
F. B. Chen, H. M. Liu, W. Chen, Z. R. Shu, Y. Li, Q. S. Li, Y. Han
Summary: In this study, wind tunnel tests were conducted on a scaled tall building to investigate the effect of facade appurtenances on wind pressure characteristics. The results showed that the change of facade appurtenances can significantly influence the fluctuating wind pressure on the windward and leeward surfaces. Adding vertical strips was found to reduce the horizontal coherence of surface wind pressure.
JOURNAL OF BUILDING ENGINEERING
(2022)
Article
Engineering, Civil
Daniel Gonzalez-Fernandez, Raffaele De Risi, Djamel Rezgui, John H. G. Macdonald, Alessandro Margnelli, Branislav Titurus
Summary: The dynamic behavior of tall buildings can change significantly during different construction phases, wind conditions, and aeroelastic phenomena. This study analyzes the acceleration measurements and wind conditions of a 150 m tall building in London over a year to understand the variations in the structural modal parameters. The results show that the response amplitude and observation time are the primary factors affecting the natural frequencies and damping ratios.
Article
Optics
Rajneesh Joshi, Bhaskar Kanseri
Summary: In this study, the concept of cross-spectral purity for nonstationary electromagnetic fields with any degree of coherence or polarization is established, and conditions for cross-spectral purity in all Stokes parameters are derived in both space-time and space-frequency domains. The research may provide interesting insights into the statistical properties of beams from various light sources.
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION
(2021)
Article
Plant Sciences
Johanna R. Jantzen, Etienne Laliberte, Alexis Carteron, Rosalie Beauchamp-Rioux, Florence Blanchard, Anna L. Crofts, Alizee Girard, Paul W. Hacker, Juliana Pardo, Anna K. Schweiger, Sabrina Demers-Thibeault, Nicholas C. Coops, Margaret Kalacska, Mark Vellend, Anne Bruneau
Summary: Leaf spectra are integrated phenotypes capturing various traits, providing insights into ecological processes. The relationship between leaf spectra and mycorrhizal associations is mixed, with few studies accounting for shared evolutionary history.
Article
Neurosciences
Antonis D. Savva, George K. Matsopoulos, Georgios D. Mitsis
Summary: This study utilized a wavelet-based method to analyze dynamic functional connectivity and identified dynamic connections within the default mode network, involving the medial prefrontal and posterior cingulate cortices, inferior parietal lobes, and hippocampal formation. The results showed that these dynamic connections were highly consistent in test-retest analysis.
BRAIN CONNECTIVITY
(2022)
Article
Computer Science, Interdisciplinary Applications
Joris Chau, Rainer Von Sachs
Summary: This paper introduces intrinsic wavelet transforms and denoising methods for time-varying Fourier spectral matrix estimation. The use of linear or nonlinear wavelet shrinkage allows for natural adherence to positive definiteness and equivariance. The algorithmic construction enables wavelet transformation in the space of Hermitian positive definite matrices and threshold convergence for intrinsically smooth surfaces. Additionally, practical nonlinear thresholding based on matrix-valued wavelet coefficients is investigated, leading to the estimation of time-varying spectral matrices in a nonstationary multivariate electroencephalography (EEG) time series recorded during an epileptic brain seizure.
COMPUTATIONAL STATISTICS & DATA ANALYSIS
(2022)
Article
Statistics & Probability
Mahnaz Khalafi, Ahmad Reza Soltani, Masoud Golalipour, Majid Azimmohseni, Farzad Najafiamiri
Summary: In this paper, a class of multivariate periodically correlated processes and their corresponding time-domain and spectral-domain characterizations are introduced. A spectral coherence measure based on the Hilbert-Schmidt inner product of the Fourier transforms is proposed to assess the dependence between two periodically correlated processes. An estimator for the spectral coherence is developed along with a hypothesis for significant dependence and a testing procedure. Numerical examples using simulated and real PC time series are presented to illustrate the performance of the spectral coherence and its estimator.
CANADIAN JOURNAL OF STATISTICS-REVUE CANADIENNE DE STATISTIQUE
(2022)
Article
Engineering, Mechanical
Ming Wang, Xiaozhen Li, Xinzhong Chen
Summary: This technical note focuses on the overturning risk assessment of high-speed trains over multi-span simply supported bridges under crosswind. The study reveals that crosswind is the primary cause of the loss of vertical wheel-rail contact force, while the influence of track irregularities and bridge vibration is secondary.
VEHICLE SYSTEM DYNAMICS
(2022)
Article
Engineering, Civil
Yanchi Wu, Xinzhong Chen, Yunfei Wang
Summary: This study proposes an unscented Kalman filter approach for identifying linear or nonlinear flutter derivatives of bridge decks, with a focus on torsional vibration amplitudes and polynomial representations. The method is capable of simultaneously estimating the augmented state variables of the two degrees of freedom bridge deck system. It also demonstrates the successful extraction of nonlinear FDs and reveals the limitations of linear models, while examining the identification of unknown buffeting force excitations.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2021)
Article
Engineering, Mechanical
Changda Feng, Xinzhong Chen
Summary: This study investigated the uncoupled crosswind and alongwind responses of base-isolated tall buildings under nonstationary wind excitations, using the Bouc-Wen model and evolutionary power spectra for modeling, conducting response time-history analysis, and proposing a method to understand the nonstationary time-varying response statistics.
JOURNAL OF ENGINEERING MECHANICS
(2021)
Article
Construction & Building Technology
Jinghui Huang, Xinzhong Chen
Summary: This study presents a comprehensive characterization of the inelastic response of tall buildings under simultaneous actions of both alongwind and crosswind loads. The results reveal the importance of considering both alongwind and crosswind loads for inelastic response analysis.
JOURNAL OF STRUCTURAL ENGINEERING
(2022)
Article
Engineering, Civil
Zhihao Li, Guoqing Huang, Xinzhong Chen, Xuhong Zhou
Summary: This study presents a comprehensive investigation on the reduced model and seismic response of inter-story isolated buildings. The results show that the reduced building model can accurately estimate important seismic responses, and different dimensionless parameters have an impact on structural responses.
INTERNATIONAL JOURNAL OF STRUCTURAL STABILITY AND DYNAMICS
(2022)
Article
Engineering, Civil
Yong Wang, Xinzhong Chen
Summary: This study presents a computational fluid dynamics simulation of forced vibration of a bridge deck and proposes a novel forced vibration technique with improved efficiency, extracting amplitude-dependent aerodynamic damping.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2022)
Article
Construction & Building Technology
Jingying Tian, Xinzhong Chen
Summary: This study investigates the impact of biaxial interaction of hysteretic restoring forces of base isolation system on the wind-induced response of base-isolated tall buildings. The results show that the biaxial interaction increases the low-frequency component and decreases the resonant component of lower inelastic base displacement. However, this increase in low-frequency component does not affect the upper building response relative to the base isolation system. Additionally, the biaxial interaction leads to a rapid growth of the time-varying mean alongwind base displacement. The increase in low-frequency component is significant when the yielding level of higher response is significant and the two translational base displacements are quite different in magnitude. The correlation of the two translational base displacements enhances the influence of biaxial interaction. For base-isolated buildings with eccentricity, the alongwind and crosswind base responses are less influenced by biaxial interaction.
ADVANCES IN STRUCTURAL ENGINEERING
(2022)
Article
Engineering, Civil
Yunfei Wang, Xinzhong Chen, Yongle Li
Summary: This study revisits the modeling of buffeting forces on bridge decks and investigates the relationship between turbulence and buffeting forces. By measuring and characterizing the pressure distributions on a streamlined bridge deck in a wind tunnel, the characteristics of static force coefficients and admittances are analyzed. The results highlight the importance of appropriate simulation of large-scale turbulence in wind tunnel and estimation of buffeting responses of long-span bridges.
JOURNAL OF BRIDGE ENGINEERING
(2022)
Article
Engineering, Civil
Yong Wang, Xinzhong Chen
Summary: This study validates the accuracy of large-eddy simulation of wind pressures and loads on high-rise buildings at various angles of attack, and proposes local octree mesh refinement as an efficient strategy to improve simulation accuracy.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2022)
Article
Construction & Building Technology
Jinghui Huang, Xinzhong Chen
Summary: This study examined the accuracy of a reduced-order building model approach for inelastic response analysis of tall buildings under simultaneous actions of both alongwind and crosswind loadings. The results demonstrate the accuracy of the reduced-order building model and highlight the challenges faced in the estimation of time-varying mean component of inelastic response.
JOURNAL OF STRUCTURAL ENGINEERING
(2023)
Article
Engineering, Civil
Jingying Tian, Xinzhong Chen
Summary: This study presents an analysis framework for studying the coupled inelastic response of base-isolated tall buildings with eccentricities of mass and resistance and coupled hysteretic restoring forces of base isolation system. The influence of eccentricity on the responses of the building is investigated through response history analysis. The results show that eccentricity amplifies the alongwind response but has less effect on the larger crosswind and torsional responses.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2023)
Article
Engineering, Civil
Jinghui Huang, Xinzhong Chen
Summary: Three reduced-order building models were developed based on a nonlinear finite element model of a 60 -story steel building, with different biaxial hysteretic generalized restoring force and displacement relations. These models accurately estimated fluctuating responses but overestimated time-varying mean alongwind displacement. An improved estimation method for time-varying mean alongwind displacement was presented. The study also investigated the influence of biaxial interaction on inelastic responses, showing that it leads to faster growth of time-varying mean displacement but does not affect its steady-state value.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2023)
Article
Engineering, Civil
Zhihao Li, Xinzhong Chen, Guoqing Huang, Qingshan Yang, Xuhong Zhou, Huawei Pang
Summary: This study establishes an analysis framework for the coupled dynamic response of tall buildings isolated with multiple friction pendulum bearings (FPBs) under three-dimensional wind loads. The study quantifies the building's displacement, acceleration, and the displacements of the base slab and bearings under different wind load conditions. The research also examines the distribution of friction-induced dissipation energy and evaluates the dynamic response of a fixed-base building for comparison. Additionally, it investigates the influences of stiffness eccentricity and torsional frequency on corner acceleration to reveal torsional coupling effects.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2023)
Article
Engineering, Civil
Zhihao Li, Xinzhong Chen, Guoqing Huang, Ahsan Kareem, Xuhong Zhou
Summary: This paper investigates the dynamic response characteristics of base-isolated high-rise buildings with frictional pendulum bearings (FPB) under uncoupled alongwind and crosswind loads. Two statistical linearization methods are used to estimate the standard deviation of the structural response and obtain the equivalent parameters of the linearized system. Additionally, the time-varying mean of the base displacement under alongwind load with a non-zero mean is discussed. Parameter analysis is performed to examine the effects of sliding plate radius and friction coefficient on wind-induced vibration. This study highlights the nonlinear response characteristics of base-isolated high-rise buildings with FPB and provides design guidelines for strong winds.
ENGINEERING STRUCTURES
(2023)
Article
Engineering, Civil
Jinghui Huang, Xinzhong Chen
Summary: The influence of uncertainties on wind-induced inelastic building response is quantified using a reduced-order building model. The basic uncertain parameters include modal mass, stiffness, damping ratio, yielding displacement, and loading power spectra. The results showed that the uncertainty in response standard deviation is mainly caused by the uncertainty of modal damping ratio for elastic response, while it is further contributed by the uncertainty of the yielding displacement for inelastic response. The influence of randomness, sampling uncertainty, and parameter uncertainty on extreme response is also determined.
ENGINEERING STRUCTURES
(2023)
