Monitoring Fatigue Damage Of Modular Bridge Expansion Joints And Detection Of Grout Fulfillment In Pre-stressed Tendon Duct Based On Piezoelectric Ceramics Transducers

With the rapid development of the national economy,a variety of large civil structures are constantly emerging,but the structure is affected by load and natural disasters for a long time,vulnerable to damage,erosion,resulting in structural damage,therefore,monitoring whether the structure is safe in the service period,has become a key research topic.Intelligent materials represented by piezoelectric ceramics have been widely used in the field of smart structure monitoring due to their advantages of economic and environmental protection,fast response,easy clipping and integration of driving and sensing functions.This paper make full use of the piezoelectric ceramic advantages in the field of structural smart monitoring,put forward the new structural damage monitoring technology based on piezoelectric ceramic,carried out the experimental study of bridge expansion joint fatigue damage monitoring and the density of grouting compactness detection based on wave-based method,verify new technology for the fatigue damage identification and the feasibility of grouting compactness detection,the specific research work are as follows:(1)The current research status of bridge expansion joint fatigue,uncompacted post-tensioning tendon duct grouting and the application of piezoelectric ceramics in civil structure damage monitoring are summarized,which lays a solid theoretical foundation for future experimental research.(2)The wave-based method was used to carry out an experimental studied on the fatigue damage of bridge expansion joints.The experimental results show that the signal amplitude and wavelet packet energy of the piezoelectric sensor decrease with the increase of fatigue damage.Since the stress on both sides of the beam is not uniform,the fatigue damage of the full-penetration weld on the south side of the specimen is far greater than that on the north side.Therefore,it can be seen from the time-domain signal and the wavelet packet energy that the signal amplitude and energy value received by the sensor on the south side are far less than that on the north side of the specimen.At the same time,in the process of the test,the stiffness of the specimen was observed with a dial indicator,and it was found that this method could only represent the overall damage performance of the structure,while the wave-based method could accurately identify the damage degree and location,which further demonstrated the effectiveness and feasibility of the piezoelectric wave-based method for the fatigue damage monitoring of bridge expansion joints.(3)To solve the problem of grouting uncompacted defects in post-tensioning tendon duct,a compacted defect detection method based on wave-based method was proposed.A group of the post-tensioning tendon duct specimens with large curvature were designed and used as test specimens.The experimental results show that with the increase of grouting amount,the signal amplitude value and the wavelet packet energy increases.When the grouting degree reaches the plane where a certain sensor is located,the time domain signal,frequency domain signal and wavelet packet energy received by the sensor will increase sharply,and as the grouting degree continues to increase,all parameters will further increase,which is caused by the reflection stress wave at the void boundary of the post-tensioning tendon duct.After that,the parameters will remain stable with the increase of grouting amount.The experimental results show that the wave-based method can detect the grouting compactness quality of the post-tensioning tendon duct effectively.