Numerical Simulation And Experimental Study On Diseases Non-destructive Test Techniques For Existing Bridge Piles Based On Guided-wave Theory

As support structures, piles are an important part of bridge structures, and are crucial for thebridge safe operation and its stability. Necking, fracture, expanding or hole defects may occur ina hidden bridge pile which was influenced by many factors. In recent years, some accidentsshow that existing bridge safety situation is seriousness. In order to ensure the safe operation ofthe bridge, detecting disease(s)(defect(s)) in a pile is widely concerned, and developing theeffective diseases (defects) nondestructive test method for existing bridge piles has become afocus.However, in the existing bridge pile nondestructive test conditions are much morecomplicated than free pile nondestructive test. In practice, for a larger diameter pile, theone-dimensional wave theory and vibration theory are not satisfy, and the piles are connectedwith the upper structures, such as a pier column, beam, slab, the stress wave reflection form isdisturbed strongly, to obtain the detection signal is more complex, the analyzing and judgmentare difficult. Thus the existing bridge pile disease nondestructive detection is still one oftechnical problems. This dissertation analyzes the existing bridge pile stress wavecharacteristics and propagation, the impact factors and its decreasing or overcoming wereanalyed through numerical simulation and experiment, a existing bridge piles diseases detectiontechnique and method were advanced with simple point excitation and multichannel receivingsystem arranged in same side of pier, and multiple excitation and data weighted fusion.Theexperiment results proved that this method is practice and has good application prospect.(1)The existing bridge piles and disease types were summarized. Based on guided wavetheory and the piles dynamic testing ideas, the problems faced in the existing bridge pilefoundation inspection were analyzed. By model tests, there is a clear difference betweenexisting bridge pile test and free top pile test. Larger diameter, the uperstructure, hidden buriedunderground (underwater),and difficult to directly verify the test results pose a challenge to theimplementation of the reflection method.(2)Pile stress wave field characteristics were known through numerical simulation. Due to itis difficult or impossible to excite and receive signal at the top of the pile, point excitation andmultichannel detection system were arranged along in side the pier, and it is helpful to signalrecognition and comparison for exsiting bridge pile stress wave nondestructive testing. Whileincident wave is propagating, upper structure and the lower part of the pile foundation pileinterface of internal defects and pile bottom boundary would become a new source whichradiating to the surrounding, the received signal contains waves from upper structures and thelower structures surface (containing defects interface).Although the obtained signal is morecomplex, but the law of wave propagation is obvious.(3)Through the previous simulation results and actual case comparison,3D dynamic effect inthe existing bridge pile reflected wave method was summarized andanalyzed, effective ways ofdecreasing or overcoming the3D effect were also presented accoording to experiment.Decreasing or overcoming the3D effect had important significance to enhance reliability of theexisting bridge pile diseases detection.Exciting and receiving element and observationconditions on detection were serious influence to the existing bridge piles nondestructivedetection signals by reflected wave method.(4)Through analysis of the existing bridge piles reflected wave method test signal characteristics, the weighted data fusion technique was initial led in processing of existingbridge piles detect signal by reflected wave method, the effects to recognite and judge effectivesignal is obvious.The experimental results show that diseases in the existing bridge pilenondestructive test can be achieved acoording to arranging excitation point and line layout forreceiving multi-channel detection system in one side of pier with multichannel contrast andmultiple excitation signal fusion processing method.The mehod presented in this paper is veryeasy to operate, and its promotion prospect is broad.