Correlation analysis of the wind of a cable-stayed bridge based on field monitoring

Li, Hui,Laima, Shujin,Li, Na,Ou, Jinping,Duan, Zhondong Techno-Press 2010 Wind and Structures, An International Journal (WAS Vol.13 No.6

This paper investigates the correlation of wind characteristics monitored on a cable-stayed bridge. Total five anemoscopes are implemented into the bridge. Two out of 5 anemoscopes in inflow and two out of 5 anemoscopes in wake-flow along the longitudinal direction of the bridge are installed. Four anemoscopes are respectively distributed at two cross-sections. Another anemoscope is installed at the top of the tower. The correlation of mean wind speed and direction, power spectral density, the turbulent intensity and integral length of wind in flow at two cross-sections are investigated. In addition, considering the non-stationary characteristics of wind, the spatial correlation in time-frequency is analyzed using wavelet transform and different phenomenon from those obtained through FFT is observed. The time-frequency analysis further indicates that intermittence, coherence structures and self-similar structures are distinctly observed from fluctuant wind. The flow characteristics around the bridge deck at two positions are also investigated using the field measurement. The results indicate that the mean wind speed decrease when the flow passing through the deck, but the turbulence intensity become much larger and the turbulence integral lengths become much smaller compared with those of inflow. The relationship of RMS (root mean square) of wake-flow and the mean wind speed of inflow is approximately linear. The special structures of wake-flow in time-frequency domain are also analyzed using wavelet transform, which aids to reveal the forming process of wake-flow.

Correlation analysis of the wind of a cable-stayed bridge based on field monitoring

Hui Li,Shujin Laima,Na Li,Jinping Ou,Zhondong Duan 한국풍공학회 2010 Wind and Structures, An International Journal (WAS Vol.13 No.6

This paper investigates the correlation of wind characteristics monitored on a cable-stayed bridge. Total five anemoscopes are implemented into the bridge. Two out of 5 anemoscopes in inflow and two out of 5 anemoscopes in wake-flow along the longitudinal direction of the bridge are installed. Four anemoscopes are respectively distributed at two cross-sections. Another anemoscope is installed at the top of the tower. The correlation of mean wind speed and direction, power spectral density, the turbulent intensity and integral length of wind in flow at two cross-sections are investigated. In addition, considering the non-stationary characteristics of wind, the spatial correlation in time-frequency is analyzed using wavelet transform and different phenomenon from those obtained through FFT is observed. The time-frequency analysis further indicates that intermittence, coherence structures and self-similar structures are distinctly observed from fluctuant wind. The flow characteristics around the bridge deck at two positions are also investigated using the field measurement. The results indicate that the mean wind speed decrease when the flow passing through the deck, but the turbulence intensity become much larger and the turbulence integral lengths become much smaller compared with those of inflow. The relationship of RMS (root mean square) of wake-flow and the mean wind speed of inflow is approximately linear. The special structures of wake-flow in time-frequency domain are also analyzed using wavelet transform, which aids to reveal the forming process of wake-flow.

Numerical study on Reynolds number effects on the aerodynamic characteristics of a twin-box girder

Shujin Laima,Buchen Wu,Chao Jiang,Wenli Chen,Hui Li 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.28 No.5

For super long-span bridges, the aerodynamic forces induced by the flow passing the box girder should be considered carefully. And the Reynolds number sensitively of aerodynamic characteristics is one of considerable issue. In the study, a numerical study on the Reynolds number sensitivity of aerodynamic characteristic (flow pattern, pressure distribution and aerodynamic forces) of a twin-box girder were carried out using large eddy simulation (LES) with the dynamic Smagorinsky–Lilly subgrid model. The results show that the aerodynamic characteristics have strong correlation with the Reynolds number. At the leading edge, the flow experiences attachment, departure, and reattachment stages accompanying by the laminar transition into turbulence, causing pressure plateaus to form on the surface, and the pressure plateaus gradually shrinks. Around the gap, attributing that the flow experiences stages of laminar cavity flow, the wake with alternate shedding vortices, and turbulent cavity flow in sequence with an increase in the Reynolds number, the pressures around the gap vary greatly with the Reynold number. At the trailing edge, the pressure gradually recovers as the flow transits to turbulence (the flow undergoes wake instability, shear layer transition-reattachment station), In addition, at relative high Reynolds numbers, the drag force almost does not change, however, the lift force coefficient gradually decreases with an increase in Reynolds number.

Distortional buckling of I-steel concrete composite beams in negative moment area

Wangbao Zhou,Shujin Li,Zhi Huang,Lizhong Jiang 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.1

The predominant type of buckling that I-steel concrete composite beams experience in the negative moment area is distortional buckling. The key factors that affect distortional buckling are the torsional and lateral restraints by the bottom flange. This study thoroughly investigates the equivalent lateral and torsional restraint stiffnesses of the bottom flange of an I-steel concrete composite beam under negative moments. The results show a coupling effect between the applied forces and the lateral and torsional restraint stiffnesses of the bottom flange. A formula is proposed to calculate the critical buckling stress of the I-steel concrete composite beams under negative moments by considering the lateral and torsional restraint stiffnesses of the bottom flange. The proposed method is shown to better predict the critical bending moment of the I-steel composite beams. This article introduces an improved method to calculate the elastic foundation beams, which takes into account the lateral and torsional restraint stiffnesses of the bottom flange and considers the coupling effect between them. The results show a close match in results from the calculation method proposed in this paper and the ANSYS finite element method, which validates the proposed calculation method. The proposed calculation method provides a theoretical basis for further research on distortional buckling and the ultimate resistance of I-steel concrete composite beams under a variable axial force.

Spatial correlation-based WRF observation-nudging approach in simulating regional wind field

Hehe Ren,Shujin Laima,Wen-Li Chen,Anxin Guo,Hui Li 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.28 No.2

Accurately simulating the wind field of large-scale region, for instant urban areas, the locations of large span bridges, wind farms and so on, is very difficult, due to the complicated terrains or land surfaces. Currently, the regional wind field can be simulated through the combination of observation data and numerical model using observation-nudging in the Weather Research and Forecasting model (WRF). However, the main drawback of original observation-nudging method in WRF is the effects of observation on the surrounding field is fully mathematical express in terms of temporal and spatial, and it ignores the effects of terrain, wind direction and atmospheric circulation, while these are physically unreasonable for the turbulence. For these reasons, a spatial correlation-based observation-nudging method, which can take account the influence of complicated terrain, is proposed in the paper. The validation and comparation results show that proposed method can obtain more reasonable and accurate result than original observation-nudging method. Finally, the discussion of wind field along bridge span obtained from the simulation with spatial correlation-based observation-nudging method was carried out.

Distortional buckling calculation method of steel-concrete composite box beam in negative moment area

Wangbao Zhou,Shujin Li,Lizhong Jiang,Zhi Huang 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.5

'Distortional buckling&' is one of the predominant buckling types that may occur in a steel-concrete composite box beam (SCCBB) under a negative moment. The key factors, which affect the buckling modes, are the torsional and lateral restraints of the bottom plate of a SCCBB. Therefore, this article investigates the equivalent lateral and torsional restraint rigidity of the bottom plate of a SCCBB under a negative moment; the results of which show a linear coupling relationship between the applied forces and the lateral and/or torsional restraint stiffness, which are not depended on the cross-sectional properties of a SCCBB completely. The mathematical formulas for calculating the lateral and torsional restraint rigidity of the bottom plate can be used to estimate: (1) the critical distortional buckling stress of SCCBBs under a negative moment; and (2) the critical distortional moment of SCCBBs. This article develops an improved calculation method for SCCBBs on an elastic foundation, which takes into account the coupling effect between the applied forces and the lateral and/or torsional restraint rigidity of the bottom plate. This article analyzes the accuracy of the following calculation methods by using 24 examples of SCCBBs: (1) the conventional energy method; (2) the improved calculation method, as it has been derived in this article; and (3) the ANSYS finite element method. The results verify that the improved calculation method, as it has been proved in this article, is more accurate and reliable than that of the current energy method, which has been noted in the references.

Flexural natural vibration characteristics of composite beam considering shear deformation and interface slip

Wangbao Zhou,Lizhong Jiang,Zhi Huang,Shujin Li 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.5

Based on Hamilton's principle, the flexural vibration differential equations and boundary conditions of the steel-concrete composite beam (SCCB) with comprehensive consideration of the influences of the shear deformation, interface slip and longitudinal inertia of motion were derived. The analytical natural frequencies of flexural vibration were compared with available results previously observed by the experiments, the results calculated by the FE model and the other similar beam theories available in the open literatures. The comparison results showed that, the calculation results of the analytical and Timoshenko models had a good agreement with the results of the experimental test and FE model. Finally, the influences of shear deformation and interface slip on the flexural natural frequencies of the SCCB were discussed. The shear deformation effect increases with the increase of the mode orders of flexural natural vibration, and the flexural natural frequencies of the higher mode orders ignoring the influence of shear deformations effect would be overestimated. The interface slip effect decrease with the increase of the mode orders of flexural natural vibration, and the influence of the interface slip effect on flexural natural frequencies of the low mode orders is significant. The influence of the degree of shear connection on shear deformation effect is insignificant, and the low order modes of flexural natural vibration are mainly composed of the rotational displacement of cross sections.

Experimental Study on the Deformation of a Cut-Off Wall in a Landfill

Guozhong Dai,Jia Zhu,Yang Song,Shujin Li,Guicai Shi 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.5

To effectively solve the leakage problem of landfill leachate, it is necessary to establish a vertical cut-off wall around the landfill site for seepage control. To accurately analyze the deformation of the cut-off wall, a 1/8-scale landfill cut-off wall miniature model is designed and fabricated. The actual force of the cut-off wall is simulated by filling sand on the outer side of the model wall. Meanwhile, a nonlinear finite element model of the wall is established using the ANSYS to simulate the deformation of the seepage wall. The results show that the cut-off wall made from a polyvinyl alcohol-bentonite-fly ash-cement (PBFC) anti-seepage slurry has a high ultimate bearing capacity, and its ultimate strain is approximately 5%, which is much higher than the limit strain of the actual force conditions of the cut-off wall. The horizontal displacement of the cut-off wall is approximately linear and decreases gradually from the top to the bottom, and no reverse displacement is observed. The main stress of the wall is smaller than that of the slurry, and there is no tensile stress. The simulated results are similar to the measured values of the cut-off wall, which indicates the accuracy of the simulation analysis.