基于声发射技术的钢桥面板疲劳损伤监测与评估

采用多种监测技术融合手段, 对正交异性钢桥面板开展了疲劳损伤监测与评估, 包括足尺正交异性钢桥面板节段模型疲劳试验与某公路斜拉桥正交异性钢桥面板运营阶段的疲劳损伤监测; 在正交异性钢桥面板疲劳试验中, 综合采用了美国物理声学(PAC)声发射(AE)传感器、智能锆钛酸铅压电漆(PZT)传感器和应变片进行了粘贴钢板冷加固前后的疲劳裂纹监测; 对处于运营阶段的斜拉桥钢桥面板疲劳开裂区域, 采用了粘贴角钢的冷加固方法进行加固, 并对加固前后的桥梁结构开展了AE监测和应变监测以研究疲劳裂纹状态与检验冷加固方法的效果。疲劳试验与监测结果表明: PAC的AE传感器和智能PZT传感器能有效捕捉具有突发峰值与快速衰减特征的疲劳扩展信号, 二者的协同应用实现了疲劳裂纹智能感知, PAC的AE传感器组能实时捕捉纵肋上的疲劳裂纹扩展长度和方向; 粘贴钢板冷加固后, 应力水平稳定在64.8 MPa, 直到继续循环加载至512万次仍无疲劳裂纹扩展, 验证了正交异性钢桥面板粘贴钢板疲劳冷加固措施的良好加固效果; 在疲劳试验过程中, PAC的AE传感器和智能PZT传感器监测疲劳裂纹扩展结果一致性良好, 与应变片相比可实时捕捉更丰富的疲劳裂纹动态信息。对运营阶段正交异性钢桥面板疲劳监测与评估结果表明: 加固前AE监测结果峰值能量是加固后峰值能量的5倍, AE累积信号由加固前的密集分布改变为加固后的稀散分布, 表明加固后的钢桥面板疲劳裂纹处于稳定状态; 随着加载车辆行驶通过, 冷加固后的疲劳裂纹尖端应力峰值降低40%至50%;对比加固前后的24 h疲劳应力连续监测结果, 疲劳细节附近应变片的应变水平从加固前的78 MPa下降至加固后的48 MPa; AE信号峰值能量、AE累积信号和应力水平的监测结果均证明了冷加固技术对正交异性钢桥面板疲劳开裂加固的有效性。 

Monitoringand evaluation of fatigue damage for orthotropic steel deck usingacoustic

Based on the integration of multiple monitoring technologies, the fatigue damage was analyzed and assessed for the orthotropic steel deck(OSD), including the fatigue test of a fullscale OSD segment in lab and the fatigue damage monitoring of a cable-stayed highway steel bridge with the OSD during service stage.For the fatigue test study of the OSD in lab, two kinds of acoustic emission(AE)sensors, including physical acoustics corporation(PAC)commercial AE sensors and smart piezoelectric paint sensors made of lead-zirconate-titanate(PZT), and supplementary strain gages were comprehensively used to detect and monitor the fatigue crack activities before and after the cold reinforcement of bonding steel plate.For the in-service highway steel bridges with detected fatigue cracks in the OSD, the cold reinforcement of bonding angel steel was proposed for the fatigue sensitive details in the OSD.Both AE monitoring and strain monitoring were conducted to study the fatigue crack activity and verify the effectiveness of the cold reinforcement.Learn from the fatigue test and monitoring results in lab, both PAC commercial AE sensors and smart PZT sensors are efficient ways to capture the fatigue propagation signals that have the characteristic of a peak amplitude and then fading gradually.The application of both PAC commercial AE sensors and smart PZT sensors achieve smart monitoring for the fatigue crack activity.The PAC commercial AE sensor group can locate the fatigue crack propagation length and direction in the rib accurately.After adopting bonding steel plate, the stress level keeps at 64.8 MPa stably, and no fatigue crack propagation is observed untill the cyclic loading accumulates to 5.12million times, testifying fine workability of the OSD model after the cold reinforcement.The PAC commercial AE sensor and smart PZT sensor have good agreement in detecting fatigue crack propagation during fatigue loading process, and can capture more fatigue crack activity information in-time than the strain gage.Learn from the monitoring and evaluation results for the in-service steel bridge with the OSD, the peak energy of AE monitoring result before the cold reinforcement is 5times as that after the cold reinforcement, and the accumulated AE signals decreasing from intensive to scatter indicate the stability of fatigue cracks.After the cold reinforcement, the peak stresses nearby the fatigue crack tips decrease by 40%to 50%when the loading vehicles pass, and the maximum stress near the fatigue detail declines from 78MPa before the cold reinforcement to 48MPa after the cold reinforcement during 24hmonitoring.The peak energy and accumulated number of AE signals and the stress level testify the effectiveness of cold reinforcement for the fatigue cracks in the OSD.14figs, 31refs.