Effects of loading sequence on fatigue damage accumulation of asphalt mixture

Abstract

The accumulation process of fatigue damage of asphalt mixture under variable amplitude loading exhibits an obvious nonlinear characteristic. However, the traditional linear damage accumulation criterion fails to characterize the nonlinear fatigue damage accumulation (NLFDA) under different loading sequences. This study aims to investigate the effects of loading sequence on the fatigue damage accumulation of asphalt mixture. First, the fatigue tests with constant amplitude loading were carried out to investigate the fatigue damage accumulation under constant amplitude loading. Then, the SCB fatigue tests with variable amplitude loading were conducted to analyze the fatigue damage accumulation under variable amplitude loading. Finally, the NLFDA model considering the loading sequence was established to analyze the effects of loading sequence on the fatigue damage accumulation of asphalt mixture. It was found that the fatigue damage of asphalt mixture under constant amplitude loading evolved nonlinearly, however, it obeyed linear damage accumulation criterion and the cumulative life fractions are equal to one. The variable amplitude loading can lead to that the fatigue damage evolves nonlinearly and obeys nonlinear damage accumulation criterion, and the cumulative life fractions of the loading sequences of low-high and high-low are greater than one and less than one, respectively. The established NLFDA model can effectively characterize the dependence of the fatigue damage of asphalt mixture on the loading sequence. 沥青混合料在变幅加载下的疲劳损伤累积过程具有明显的非线性特征,然而传统的线性损伤累积准则无法表征不同加载次序下的非线性疲劳损伤累积(NLFDA)。为研究加载次序对沥青混合料疲劳损伤累积的影响,首先开展恒幅加载疲劳试验,分析恒幅加载下的疲劳损伤累积规律;其次借助变幅加载疲劳试验,分析变幅加载下的疲劳损伤累积规律;最后建立考虑加载次序的NLFDA模型,分析加载次序对沥青混合料疲劳损伤累积的影响。结果表明:恒幅加载下沥青混合料疲劳损伤发生非线性演化,但服从线性损伤累积准则,且累积寿命分数为1;变幅加载会导致疲劳损伤发生非线性演化,且服从非线性损伤累积准则,低-高和高-低加载次序的累积寿命分数分别大于1和小于1;建立的NLFDA模型可较为准确地表征沥青混合料疲劳损伤对加载次序的依赖性。