基于压电导纳的钢框架螺栓松动检测试验研究

介绍了基于压电导纳的结构健康监测技术基本原理;利用该技术对钢框架结构进行了螺栓松动检测试验研究。即将三个压电陶瓷片粘贴在钢框架节点处的不同构件表面,通过测量框架节点处各压电陶瓷片在螺栓松动前后电导纳的变化来识别损伤.试验结果发现,位于连接板处的压电陶瓷片对该节点处的螺栓松动最敏感,而与螺栓不直接相连的上斜撑上的压电陶瓷电导纳则几乎不受连接板螺栓松动的影响。分别定义了基于电导纳实部和虚部改变的均方根(RMSDR和RMSDI)作为损伤程度识别指标,对框架节点的螺栓松动损伤程度进行了定性识别研究。通过对得到的RMSDR和RMSDI两种损伤指标值对比发现,基于压电导纳实部信息定义的损伤程度识别指标RMSDR能较好地识别框架节点螺栓松动损伤程度,而基于电导纳虚部定义的识别指标RMSDI则不能正确识别。

EXPERIMENTAL STUDY ON DETECTING LOOSENED BOLTS OF A STEEL FRAME BASED ON PIEZOELECTRIC ADMITTANCE

The basic idea of piezoelectric admittance technique for structural health monitoring is presented. An experimental study on detecting loosened bolts of a steel frame is implemented based on the technique. In this experiment, three PZT sheets are bonded to surfaces of three different components around a joint of the frame separately, and looseness of bolts is identified by monitoring the variations of piezoelectric admittance measurements. From the experimental results it is found that the admittance of the PZT sheet located at the connection plate is quite sensitive to looseness of the bolt, that of the PZT one located at the upper bevel support indirectly linked to the connection plate is insensitive to looseness of the bolt. Subsequently, two damage indeces, the root-mean-square deviation of real part of admittance (RMSDR) and the root-mean-square deviation of imaginary part of admittance (RMSDI) are defined, respectively. The damage level of the steel frame is evaluated using these two indeces. By comparison, it is found that the RMSDR index can correctly reflect the damage level of the steel frame qualitatively, but the RMSDI one can not.