The fatigue of concrete structures will gradually appear after being subjected to alternating loads for a long time,and the accidents caused by fatigue failure of bridge structures also appear from time to time.Aiming...The fatigue of concrete structures will gradually appear after being subjected to alternating loads for a long time,and the accidents caused by fatigue failure of bridge structures also appear from time to time.Aiming at the problem of degradation of long-span continuous rigid frame bridges due to fatigue and environmental effects,this paper suggests a method to analyze the fatigue degradation mechanism of this type of bridge,which combines long-term in-site monitoring data collected by the health monitoring system(HMS)and fatigue theory.In the paper,the authors mainly carry out the research work in the following aspects:First of all,a long-span continuous rigid frame bridge installed with HMS is used as an example,and a large amount of health monitoring data have been acquired,which can provide efficient information for fatigue in terms of equivalent stress range and cumulative number of stress cycles;next,for calculating the cumulative fatigue damage of the bridge structure,fatigue stress spectrum got by rain flow counting method,S-N curves and damage criteria are used for fatigue damage analysis.Moreover,it was considered a linear accumulation damage through the Palmgren-Miner rule for the counting of stress cycles.The health monitoring data are adopted to obtain fatigue stress data and the rain flow counting method is used to count the amplitude varying fatigue stress.The proposed fatigue reliability approach in the paper can estimate the fatigue damage degree and its evolution law of bridge structures well,and also can help bridge engineers do the assessment of future service duration.展开更多
A filtering method of aero-engine load spectrum based on the rain flow counting is proposed in this paper.Firstly,the original load spectrum is counted through the rain flow method to get the peak and valley values.Th...A filtering method of aero-engine load spectrum based on the rain flow counting is proposed in this paper.Firstly,the original load spectrum is counted through the rain flow method to get the peak and valley values.Then,some data points in the original load spectrum are added between the peak and valley values.Finally,the filtering spectrum is obtained.The proposed method can reflect the path information of the original load spectrum.In addition,it can also eliminate the noise in the signal and improve the efficiency of signal processing,which is of practical significance for the research of aero-engine.展开更多
涡激振动是引发立管疲劳损伤的关键诱因之一。基于Van Der Pol尾流振子方程,研究了不同长度两端铰接的钢悬链线立管在相同来流流量不同剖面剪切来流作用下的涡激振动响应。采用二阶中心差分法对时域和空间域的耦合方程组进行了求解,并...涡激振动是引发立管疲劳损伤的关键诱因之一。基于Van Der Pol尾流振子方程,研究了不同长度两端铰接的钢悬链线立管在相同来流流量不同剖面剪切来流作用下的涡激振动响应。采用二阶中心差分法对时域和空间域的耦合方程组进行了求解,并采用雨流计数法对立管的疲劳寿命进行了预测。结果表明,立管振动沿轴向传播呈驻波和行波的混合模式,随立管长度的增加,振动响应由驻波主导转变为行波主导。受剪切来流剖面的影响,立管振动响应呈现多频特性,行波自立管的顶部向底部传播,且其传播速率随来流剪切程度及立管长度而变化。随剪切程度的增强,立管从流体中获得的能量减少,能耗增加,振动位移减少。相同来流剖面时,随着水深的增加,立管疲劳损伤增加;而水深相同时,随来流剪切程度的增加,疲劳损伤逐渐增大。展开更多
文摘The fatigue of concrete structures will gradually appear after being subjected to alternating loads for a long time,and the accidents caused by fatigue failure of bridge structures also appear from time to time.Aiming at the problem of degradation of long-span continuous rigid frame bridges due to fatigue and environmental effects,this paper suggests a method to analyze the fatigue degradation mechanism of this type of bridge,which combines long-term in-site monitoring data collected by the health monitoring system(HMS)and fatigue theory.In the paper,the authors mainly carry out the research work in the following aspects:First of all,a long-span continuous rigid frame bridge installed with HMS is used as an example,and a large amount of health monitoring data have been acquired,which can provide efficient information for fatigue in terms of equivalent stress range and cumulative number of stress cycles;next,for calculating the cumulative fatigue damage of the bridge structure,fatigue stress spectrum got by rain flow counting method,S-N curves and damage criteria are used for fatigue damage analysis.Moreover,it was considered a linear accumulation damage through the Palmgren-Miner rule for the counting of stress cycles.The health monitoring data are adopted to obtain fatigue stress data and the rain flow counting method is used to count the amplitude varying fatigue stress.The proposed fatigue reliability approach in the paper can estimate the fatigue damage degree and its evolution law of bridge structures well,and also can help bridge engineers do the assessment of future service duration.
基金This work was supported by the National Basic Research Program of China,National Nature Science Foundation of China(No.51675266)the Foundation Research Funds for the Center in NUAA(Nos.NJ20160038,NS2017011)Foundation of Graduate Innovation Center in NUAA(No.kfjj20170220)。
文摘A filtering method of aero-engine load spectrum based on the rain flow counting is proposed in this paper.Firstly,the original load spectrum is counted through the rain flow method to get the peak and valley values.Then,some data points in the original load spectrum are added between the peak and valley values.Finally,the filtering spectrum is obtained.The proposed method can reflect the path information of the original load spectrum.In addition,it can also eliminate the noise in the signal and improve the efficiency of signal processing,which is of practical significance for the research of aero-engine.
文摘涡激振动是引发立管疲劳损伤的关键诱因之一。基于Van Der Pol尾流振子方程,研究了不同长度两端铰接的钢悬链线立管在相同来流流量不同剖面剪切来流作用下的涡激振动响应。采用二阶中心差分法对时域和空间域的耦合方程组进行了求解,并采用雨流计数法对立管的疲劳寿命进行了预测。结果表明,立管振动沿轴向传播呈驻波和行波的混合模式,随立管长度的增加,振动响应由驻波主导转变为行波主导。受剪切来流剖面的影响,立管振动响应呈现多频特性,行波自立管的顶部向底部传播,且其传播速率随来流剪切程度及立管长度而变化。随剪切程度的增强,立管从流体中获得的能量减少,能耗增加,振动位移减少。相同来流剖面时,随着水深的增加,立管疲劳损伤增加;而水深相同时,随来流剪切程度的增加,疲劳损伤逐渐增大。
