Research On The Damage Detection And Identification Techniques Of The Jib Of Tower Crane

Nowadays the tower crane is used widely in the engineering construction, but thenumber of accidents caused by the cranes is getting greater as well, the reasons to theaccidents are various, but one reason like the cracks caused by material defect,unreasonable welding procedure and long-term used, fatigue crack and corrosion forexample, may appear. And they lead to the accident is to some proportion. So the studyof detection and identification of damage cracks on the metal structure is extremelyurgent.By using the strain as an index to detect and identify the structure damage and itsconcrete implementing ways are discussed, and optimize the sampling position, then usethe FEA to verify this method. Take specific conditions into consideration for itsapplication to analysis the limitation and the remedial measure can be used when usingthis method in practice.Using the wavelet analysis of signal singularity theory to study the structuredamage detection and identification of beam with moving load is studied here.Stimulating and analysis the transient state of the cantilever beam and simple beam withcrack on with finite element softwares, then using wavelet multi-resolution analysis toanalyze the displacement of the whole beam, and the displacement of one samplingpoint. Through the wavelet coefficients in scale-space mutation, both the positions ofsingle and multiple cracks can be detected, and use the Lipschitz index to indicate thedamage severity. Also the detection affection of different speed of the moving load isstudied here, the result indicates that the load moves in lower speed is better than inhigh speed.Take the standard knot of the crane jib of flat top tower crane of Yong MaoSTT753as an example to study the detection of damage crack of structure with movingload on with wavelet detection identification. Using the software to analysis thetransient state of the jib with crack on, then take the displacement of one sampling pointduring the stimulation time, then detect the position of crack through the waveletcoefficients in scale-space mutation. Take the practical conditions of the jib intoconsideration, the number of sampling points using and its position optimization todetect single and multiple cracks are also studied here.Take the tower crane model which is scale-down into experiment, in order to verifythe damage detection of the jib with moving load on. If where is single of two cracks onthe cantilever beam jib model, gathering the acceleration and displacement time-historyof the free end sampling point, and using wavelet multi-resolution analysis to deal withthis data, the results indicate that this method can be used to detect the position of thecracks. The experiment shows that this technique in engineering practice has certain application prospect.The article is a preliminary attempt to study the damage detection andidentification of the jib of tower crane, and mainly deals with the damage position andseverity detection, the experience and data got here could be used as reference ofstructure damage crack detection of tower crane and other devices, may have certainpractical value as well.