随机变幅疲劳荷载下CFL增强RC梁疲劳寿命的试验研究

基于321国道上1个月内通过某桥的随机车流量数据，经过一系列的转换得到试验用的随机变幅疲劳荷载谱，并通过MTS810疲劳试验机实现了随机变幅疲劳荷载下碳纤维薄板（CFL）增强RC梁三点弯曲疲劳试验。试验结果表明：与普通RC梁相比，CFL的加固显著提高了随机疲劳荷载作用下RC梁的疲劳寿命，改善了其疲劳性能；随机变幅荷载下增强梁的疲劳损伤演化和疲劳破坏模式与常幅疲劳荷载相同；但随着疲劳荷载水平和荷载幅值的增大，随机变幅疲劳荷载作用下构件的疲劳寿命低于常幅疲劳荷载作用下得到的寿命，因此结构设计中采用常幅疲劳试验结果估算实际服役构件的疲劳寿命和进行疲劳设计是不安全的。

EXPERIMENTAL STUDY ON FATIGUE LIFE OF RC BEAMS STRENGTHENED WITH CFL UNDER RANDOM-AMPLITUDE FATIGUE LOAD

Based on the data of classified vehicles passed by a bridge on 321 national highways for a month, established through a practical survey, a random-amplitude fatigue load spectrum for tests is obtained through a series of appropriate conversions. Fatigue tests of RC beams strengthened with carbon fiber laminate （CFL） under the random-amplitude fatigue load spectrum are conducted by using MTS810 fatigue systems. Experimental results show that CFL can improve the fatigue life and fatigue capability of strengthened beams under Random-amplitude fatigue load; the fatigue damage evolvement and failure mode of strengthened beams under Random-amplitude fatigue load are in common with beams under constant fatigue load; the fatigue lives obtained from the random-amplitude fatigue tests are far lower than those obtained from constant amplitude fatigue tests with the load level and amplitude increasing. Thus it is dangerous to use the experimental results from constant amplitude fatigue tests to estimate the fatigue life in service.