随机变幅疲劳荷载下预应力混凝土梁疲劳寿命的试验研究

基于实测的钢筋混凝土吊车梁疲劳荷载谱,经过适当的简化得到试验用随机变幅疲劳荷载谱,并通过MTS疲劳试验机实现了该随机变幅疲劳荷载谱作用下部分预应力混凝土梁的疲劳试验。试验结果表明,由随机变幅疲劳试验得出的构件疲劳寿命远低于由疲劳荷载上限值取为荷载谱均值的等幅疲劳试验得出的疲劳寿命,因此如果采用后者的试验结果去估算实际服役中的预应力混凝土构件的疲劳寿命是非常危险的。然后分别利用Miner准则、相对Miner准则和Corten-Dolan累积损伤准则对承受随机变幅疲劳荷载作用的试件疲劳寿命进行了估算。计算结果表明,改进的Corten-Dolan累积损伤准则精度最高,相对Miner准则也具有较高的精度,Miner准则的精度最低且偏于不安全。建议对预应力混凝土受弯构件进行随机变幅疲劳分析时采用改进的Corten-Dolan累积损伤准则或相对Miner准则。

An experimental study on the fatigue life of prestressed concrete beams under random-amplitude fatigue loading

Based on the fatigue loading spectrum of R.C.crane beams,established through a practical survey,a random-amplitude fatigue loading spectrum for conducting tests is obtained through appropriate simplifications.Fatigue tests of prestressed concrete beams under the random-amplitude fatigue loading spectrum are conducted by using MTS fatigue machines.The experimental results suggest that the fatigue lives obtained from the random-amplitude fatigue tests are far lower than those obtained from constant-amplitude fatigue tests with the upper values of fatigue loading assumes the mean value of the loading spectrum.Thus it is dangerous to use the experimental results from the latter to estimate the fatigue life of prestressed concrete beams in service.The Miner rule,the relative Miner rule,and the Corten-Dolan cumulative damage rule are applied to calculate the fatigue lives of specimens under random-amplitude fatigue loading.Comparisons between the calculated and the experimental results show that the modified Corten-Dolan cumulative damage rule can accurately predict the fatigue lives of specimens.The relative Miner rule can also provide certain accuracy,whereas the results from the Miner rule are considerably unsafe.It is suggested that the modified Corten-Dolan cumulative damage rule or the relative Miner rule be used in estimating the fatigue life of prestressed concrete beams under random-amplitude fatigue loading.