考虑低应力幅影响的钢吊车梁疲劳可靠度分析

Fatigue Reliability Analysis of Steel Crane Girders Considering Influence of Low Stress Range

摘要:

讨论了钢吊车梁疲劳可靠度分析方法.首先，建立了考虑低应力幅对变幅疲劳损伤程度减弱和疲劳荷载循环次数增长率这两个因素的钢吊车梁疲劳失效极限状态方程；其次，探讨了疲劳失效极限状态方程中各随机变量的统计特性，并按一次二阶矩方法和蒙特卡洛模拟方法计算了疲劳可靠度指标；然后，通过算例，研究了以上两个因素对疲劳可靠度指标的影响.研究结果表明：考虑低应力幅的疲劳损伤减弱后，钢吊车梁的疲劳可靠度指标显著增大，但随着疲劳荷载循环次数增长率的提高，疲劳可靠度指标降低.最后，提出了钢结构疲劳设计的几点建议.

Abstract:

Fatigue reliability analysis method for steel crane girders is discussed in the paper. Firstly, fatigue failure limit state equations are developed in which two factors are considered such as the variable amplitude fatigue damage reduction caused by low stress range and the growth in number of fatigue cyclic loading. Next, the statistical properties of random variables in the limit state equation are investigated. Both the first order second moment method and Monte Carlo simulation technique are employed to calculate the fatigue reliability index. Then, a case study is carried out to investigate the effect of the above tow factors on fatigue reliability index. The current research results reveal that fatigue reliability index of steel crane girders increases significantly after considering fatigue damage reduction of low stress range，but it decreases as the growth rate in number of fatigue cyclic loading increases. Finally, a few of suggestions are given for fatigue design of steel structures.