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RISS 인기검색어
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- 저자 : Youliang Zhou (검색결과 4 건)
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Thermal Field Characteristic Analysis of Steel Box Girder Based on Long-term Measurement Data
Youliang Ding,Guangdong Zhou,Aiqun Li,Gaoxin Wang 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.2
Thermal loads are important factors that affect the serviceability of long-span bridges. In this paper, the distribution characteristics and statistical features of thermal field in flat steel box girder are presented based on long-term field measurement data collected by the structural health monitoring system (SHMS) permanently installed on the Runyang Suspension Bridge (RSB). Firstly, the daily variations as well as seasonal ones of measurement temperature and temperature differences in the box girder cross-section are summarized. Secondly, employing a combined probability distribution model defined by the weighted sum of one Weibull distribution and one normal distribution, the probability density function (PDF)of each temperature difference is formulated. Thirdly, making use of the extreme value analysis, the extreme temperature differences are predicted with a return period of bridge design working life and compared with the expected values in British standard (BS EN 1991-1-5, 2003). Finally, the critical temperature difference models in cross-section are proposed for thermal stresses calculation according to correlation analysis. The results provide a clear understanding of thermal field in flat steel box girder bridges and have reference values for structural design and evaluation.
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Youliang Ding,Guangdong Zhou,Yang Deng,Aiqun Li 한국풍공학회 2013 한국풍공학회지 Vol.17 No.1
The fluctuating wind induced vibration is one of the most important factors which has been taken into account in the design of long-span bridge due to the low stiffness and low natural frequency. Field measurement characteristics of sustained wind on structure site can provide accurate wind load parameters for wind field simulation and structural wind resistance design. As a suspension bridge with 1490 m main span, the Runyang Suspension Bridge (RSB) has high sensitivity to fluctuating wind. The simultaneous and continuously wind environment field measurement both in mid-span and on tower top is executed from 2005 up to now by the structural health monitoring system installed on this bridge. Based on the recorded data, the wind characteristic parameters, including mean wind speed, wind direction, the turbulence intensity, the gust factors, the turbulence integral length, power spectrum and spatial correlation, are analyzed in detail and the coherence functions of those parameters are evaluated using statistical method in this paper. The results indicate that, the turbulence component of sustain wind is larger than extremely strong winds although its mean wind speed is smaller; the correlation between turbulence parameters is obvious; the power spectrum is special and not accord with the Simiu spectrum and von Karman spectrum. Results obtained in this study can be used to evaluate the long term reliability of the Runyang Suspension Bridge and provide reference values for wind resistant design of other structures in this region.
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Ding, Youliang,Zhou, Guangdong,Li, Aiqun,Deng, Yang Techno-Press 2013 Wind and Structures, An International Journal (WAS Vol.17 No.1
The fluctuating wind induced vibration is one of the most important factors which has been taken into account in the design of long-span bridge due to the low stiffness and low natural frequency. Field measurement characteristics of sustained wind on structure site can provide accurate wind load parameters for wind field simulation and structural wind resistance design. As a suspension bridge with 1490 m main span, the Runyang Suspension Bridge (RSB) has high sensitivity to fluctuating wind. The simultaneous and continuously wind environment field measurement both in mid-span and on tower top is executed from 2005 up to now by the structural health monitoring system installed on this bridge. Based on the recorded data, the wind characteristic parameters, including mean wind speed, wind direction, the turbulence intensity, the gust factors, the turbulence integral length, power spectrum and spatial correlation, are analyzed in detail and the coherence functions of those parameters are evaluated using statistical method in this paper. The results indicate that, the turbulence component of sustain wind is larger than extremely strong winds although its mean wind speed is smaller; the correlation between turbulence parameters is obvious; the power spectrum is special and not accord with the Simiu spectrum and von Karman spectrum. Results obtained in this study can be used to evaluate the long term reliability of the Runyang Suspension Bridge and provide reference values for wind resistant design of other structures in this region.
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Microstructure of Gear Steels Treated by Shot Peening by X-Ray Line Profile Analysis Method
Pengfei Zhu,Hongzhi Yan,Jibo Zhou,Youliang Zhou,Yin Zhang,Zhi Chen 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10
Shot peening is a common surface strengthening process of gears. It can induce compressive residual stress, refine grain size and increase dislocation density. However, there are limited reports on the quantitative analysis of dislocation substructures (type, fraction and arrangement), crystallite size and micro-strain in different crystal planes. To further reveal the microstructure strengthening mechanism of gears during shot peening, X-ray diffraction line profile analysis (XRDLPA) method is applied to study the effect of coverage on the microstructure of the gear steels. The results show that with increasing coverage, the dislocation density is increased from 2.62 × 1016 to 3.37 × 1016 m−2 in the form of screw-edge-mixed type as determined from the dislocation characteristic parameter q. The fraction of edge dislocation increases, whereas the fraction of screw dislocation decreases. The dislocation arrangement parameter M is decreased from 7.1 to 5.6, indicating that the formation of dislocation dipoles or dislocation cells in the surface layer can be further enhanced by increasing coverage. Due to the different degrees of atomic slip, the (200) crystallographic plane exhibits the smallest crystallite size and highest micro-strain, whereas the (222) plane shows the smallest micro-strain and the largest crystallite size. In addition, during shot peening, the enhancement of surface hardness of the gear steels is attributed to the phase transformation strengthening, grain-boundary hardening and dislocation hardening. The surface compressive stress of the gear steels induced by shot peening is affected not only by phase transformation, but also by Bauschinger effect, surface topography, grain refinement and so on.
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