Experimental Research On Damage Detection Of High Strength Bolt Of Steel Bridge Based On PZT Impedance Method

In recent years,with the advantages of good seismic performance,simple processing,convenient transportation,easy connection and installation,the steel structure bridge has been greatly developed.High strength bolt as one of the main connection of steel structure bridge joints,it is often loose or corroded which caused by fatigue load,vibration impact,forced vibration,bad environment,etc.These phenomena have a very negative impact on the safe and reliable operation of the structure.Therefore,it is necessary to monitor the damage of high strength bolt in real time.In this paper,the piezoelectric impedance technique is applied to the monitoring of high strength bolt,and the main conclusions are as follow:First,on the basis of summarizing the damage detection technology of high strength bolt and the current research of structural health monitoring based on piezoelectric ceramics,the advantages of piezoelectric impedance method in structural health monitoring are described.The piezoelectric effect and the impedance characteristics of piezoelectric materials are introduced in detail,and the admittance damage index is introduced to analyze the test results,which provides the necessary theoretical basis for the experiment.Second,for the high strength bolt loose damage problem,test specimens were designed corresponding to two different types of bolts,and 4 PZT sensors attached to a predetermined position to obtain the electromechanical coupling admittance under different damage degree.The experimental results show that,the electromechanical coupling admittance curve under the condition of damage is obviously shifted to the left than that in the healthy condition,and the offset is positively correlated with the number of bolt looseness.The damage index also increases with the increase of the number of loose bolts,and the real part of the admittance is more sensitive to the near distance damage.Through the analysis of the admittance curve and damage index,The damage state of the structure bolt can be preliminarily identified by the change of the admittance curve,and the damage index can be used to make an accurate judgment on the number of the looseness of the high strength bolt.Third,for the high strength bolt corrosion damage problem,the high strength bolts were accelerated corrosion,and the electromechanical coupling admittance data and quality under different corrosion states are collected.The test results show that,compared with the electromechanical coupling admittance curve of healthy status,the curve of the corrosion damage state is downward,and with the increase of the number of loose bolts,the downward movement is more.The quality of the sample and the corrosion days are basically a function relationship.The damage index also increases with the increase of the number of days of corrosion,and the real part of the admittance has the sensitivity of the distance of damage,which verifies the feasibility and effectiveness of the piezoelectric impedance method in monitoring the corrosion damage of steel structure bridges.