Cable-stayed bridges have been widely used in high-speed railway infrastructure.The accurate determination of cable’s representative temperatures is vital during the intricate processes of design,construction,and mai...Cable-stayed bridges have been widely used in high-speed railway infrastructure.The accurate determination of cable’s representative temperatures is vital during the intricate processes of design,construction,and maintenance of cable-stayed bridges.However,the representative temperatures of stayed cables are not specified in the existing design codes.To address this issue,this study investigates the distribution of the cable temperature and determinates its representative temperature.First,an experimental investigation,spanning over a period of one year,was carried out near the bridge site to obtain the temperature data.According to the statistical analysis of the measured data,it reveals that the temperature distribution is generally uniform along the cable cross-section without significant temperature gradient.Then,based on the limited data,the Monte Carlo,the gradient boosted regression trees(GBRT),and univariate linear regression(ULR)methods are employed to predict the cable’s representative temperature throughout the service life.These methods effectively overcome the limitations of insufficient monitoring data and accurately predict the representative temperature of the cables.However,each method has its own advantages and limitations in terms of applicability and accuracy.A comprehensive evaluation of the performance of these methods is conducted,and practical recommendations are provided for their application.The proposed methods and representative temperatures provide a good basis for the operation and maintenance of in-service long-span cable-stayed bridges.展开更多
Aim To improve the efficiency of fatigue material tests and relevant statistical treatment of test data. Methods\ Least square approach and other special treatments were used. Results and Conclusion\ The concepts...Aim To improve the efficiency of fatigue material tests and relevant statistical treatment of test data. Methods\ Least square approach and other special treatments were used. Results and Conclusion\ The concepts of each phase in fatigue tests and statistical treatment are clarified. The method proposed leads to three important properties. Reduced number of specimens brings to the advantage of lowering test expenditures. The whole test procedure has more flexibility for there is no need to conduct many tests at the same stress level as in traditional cases.展开更多
In 2010, the debate over valuation of the Renminbi is again heating up and the Chinese currency has returned to appreciating against the dollar But is the Renminbi undervalued？ Drawing on the Balassa-Samuelson （B-S...In 2010, the debate over valuation of the Renminbi is again heating up and the Chinese currency has returned to appreciating against the dollar But is the Renminbi undervalued？ Drawing on the Balassa-Samuelson （B-S） effect on purchasing power parity, we conduct theoretical and empirical analyses of this issue. Theoretical analysis proves that a country＇s real exchange rate will appreciate with rising income, but the currencies of low-income countries tend to be undervalued. In order to avoid biased conclusions resulting from a single dataset or sampling method, we draw on three major publicly-available datasets to examine the B-S effect across 144 economies. Our results indicate that the degree of Renminbi misvaluation is highly dependent on the data source. Synthesizing analyses of diverse datasets, we estimate that the Renminbi was only undervalued by less than 8per cent in 2009. We conclude that China＇s external imbalance most probably results from deep-seated structural imbalances rather than Renminbi undervaluation.展开更多
A data processing method was proposed for eliminating the end restraint in triaxial tests of soil. A digital image processing method was used to calculate the local deformations and local stresses for any region on th...A data processing method was proposed for eliminating the end restraint in triaxial tests of soil. A digital image processing method was used to calculate the local deformations and local stresses for any region on the surface of triaxial soil specimens. The principle and implementation of this digital image processing method were introduced as well as the calculation method for local mechanical properties of soil specimens. Comparisons were made between the test results calculated by the data from both the entire specimen and local regions, and it was found that the deformations were more uniform in the middle region compared with the entire specimen. In order to quantify the nonuniform characteristic of deformation, the non-uniformity coefficients of strain were defined and calculated. Traditional and end-lubricated triaxial tests were conducted under the same condition to investigate the effects of using local region data for deformation calculation on eliminating the end restraint of specimens. After the statistical analysis of all test results, it was concluded that for the tested soil specimen with the size of 39.1 mm × 80 ram, the utilization of the middle 35 mm region of traditional specimens in data processing had a better effect on eliminating end restraint compared with end lubrication. Furthermore, the local data analysis in this paper was validated through the comparisons with the test results from other researchers.展开更多
For the purpose of improving the defects of the conventional friction welding method, the new friction welding technology has been examined. That is, the aim of the study is producing the joint of dissimilar materials...For the purpose of improving the defects of the conventional friction welding method, the new friction welding technology has been examined. That is, the aim of the study is producing the joint of dissimilar materials evaluated to be difficult for friction welding and non-round shape joints. In this process, after the intermediate material generates the independent friction heat on every side of the specimens, it is removed instantaneously and upset process begins to weld the specimens for a joint. In this study, similar joint of A2017 aluminum alloy and one of S45C steel were examined. On the other hand, thermal elastic-plastic stress analysis by the finite element method was carried out using ANSYS mechanical.展开更多
基金Project(2017G006-N)supported by the Project of Science and Technology Research and Development Program of China Railway Corporation。
文摘Cable-stayed bridges have been widely used in high-speed railway infrastructure.The accurate determination of cable’s representative temperatures is vital during the intricate processes of design,construction,and maintenance of cable-stayed bridges.However,the representative temperatures of stayed cables are not specified in the existing design codes.To address this issue,this study investigates the distribution of the cable temperature and determinates its representative temperature.First,an experimental investigation,spanning over a period of one year,was carried out near the bridge site to obtain the temperature data.According to the statistical analysis of the measured data,it reveals that the temperature distribution is generally uniform along the cable cross-section without significant temperature gradient.Then,based on the limited data,the Monte Carlo,the gradient boosted regression trees(GBRT),and univariate linear regression(ULR)methods are employed to predict the cable’s representative temperature throughout the service life.These methods effectively overcome the limitations of insufficient monitoring data and accurately predict the representative temperature of the cables.However,each method has its own advantages and limitations in terms of applicability and accuracy.A comprehensive evaluation of the performance of these methods is conducted,and practical recommendations are provided for their application.The proposed methods and representative temperatures provide a good basis for the operation and maintenance of in-service long-span cable-stayed bridges.
文摘Aim To improve the efficiency of fatigue material tests and relevant statistical treatment of test data. Methods\ Least square approach and other special treatments were used. Results and Conclusion\ The concepts of each phase in fatigue tests and statistical treatment are clarified. The method proposed leads to three important properties. Reduced number of specimens brings to the advantage of lowering test expenditures. The whole test procedure has more flexibility for there is no need to conduct many tests at the same stress level as in traditional cases.
文摘In 2010, the debate over valuation of the Renminbi is again heating up and the Chinese currency has returned to appreciating against the dollar But is the Renminbi undervalued？ Drawing on the Balassa-Samuelson （B-S） effect on purchasing power parity, we conduct theoretical and empirical analyses of this issue. Theoretical analysis proves that a country＇s real exchange rate will appreciate with rising income, but the currencies of low-income countries tend to be undervalued. In order to avoid biased conclusions resulting from a single dataset or sampling method, we draw on three major publicly-available datasets to examine the B-S effect across 144 economies. Our results indicate that the degree of Renminbi misvaluation is highly dependent on the data source. Synthesizing analyses of diverse datasets, we estimate that the Renminbi was only undervalued by less than 8per cent in 2009. We conclude that China＇s external imbalance most probably results from deep-seated structural imbalances rather than Renminbi undervaluation.
基金Supported by Major State Basic Research Development Program of China("973" Program,No.2010CB731502)
文摘A data processing method was proposed for eliminating the end restraint in triaxial tests of soil. A digital image processing method was used to calculate the local deformations and local stresses for any region on the surface of triaxial soil specimens. The principle and implementation of this digital image processing method were introduced as well as the calculation method for local mechanical properties of soil specimens. Comparisons were made between the test results calculated by the data from both the entire specimen and local regions, and it was found that the deformations were more uniform in the middle region compared with the entire specimen. In order to quantify the nonuniform characteristic of deformation, the non-uniformity coefficients of strain were defined and calculated. Traditional and end-lubricated triaxial tests were conducted under the same condition to investigate the effects of using local region data for deformation calculation on eliminating the end restraint of specimens. After the statistical analysis of all test results, it was concluded that for the tested soil specimen with the size of 39.1 mm × 80 ram, the utilization of the middle 35 mm region of traditional specimens in data processing had a better effect on eliminating end restraint compared with end lubrication. Furthermore, the local data analysis in this paper was validated through the comparisons with the test results from other researchers.
文摘For the purpose of improving the defects of the conventional friction welding method, the new friction welding technology has been examined. That is, the aim of the study is producing the joint of dissimilar materials evaluated to be difficult for friction welding and non-round shape joints. In this process, after the intermediate material generates the independent friction heat on every side of the specimens, it is removed instantaneously and upset process begins to weld the specimens for a joint. In this study, similar joint of A2017 aluminum alloy and one of S45C steel were examined. On the other hand, thermal elastic-plastic stress analysis by the finite element method was carried out using ANSYS mechanical.
