Theoretical And Experimental Research On Combinational Damage Detection For Structure

It is a front subject in the fields of current civil engineering that structure dynamicdamage to identify. Combined with the high-efficiency and high-accuracy instrumentsthat using for collecting and analyzing signal, the system identification techniquebased on dynamic test is gradually becoming an importance means in theengineering structure health examination. Because of the testing instrument andtechnic, we can generally acquire the line acceleration of the structure floorperpendicularity or the level direction in the actual structure, while it is difficult toacquire the rotated information of the structure floor, which is a difficult problem forresolve currently. Shear structure model is the most common simplification model ofthe building, time domain parameter identification according to shear model havethe characteristics that needn't have the rotated displacement information, thismodel is applicable to the request of currently examine technic. In addition, theambient ground vibration random excitation is an easy realization way that theexpenses are low and the affects to the environment is small. But because of the lownoise ratio of this kind of signal, the information processing difficult, the result inactual structure parameter identification isn't ideal. According to the abovementioned, this paper mainly consider the shear structure model physics parameteridentification under the ambient ground vibration random excitation and carry onseveral research works as follows:1. The basic theories on structure parameter identification and the research onthe influence that noises cause to the structure parameter identification. This paperstudy the structure dynamic parameter identification with the ambient groundvibration excitation, compare parameter identification in frequency domain methodsand time domain methods. Discuss the influence that the noise and the structure hurtdegree to take to the parameter identification result in frequency domain method andtime domain method, write the structure physics parameter identification programby frequency domain method and physics parameter identification program by timedomain methods according to shear model, carry on a great deal of number imitatecalculation and analyze.2. The method and theories researches in signal eliminate noise. At the basis offull considering the line dynamic system time domain respond characteristic andwavelet analysis frequency domain space analysis characteristic, put forward a newde-noise method that obtained the structure characteristic information from thesignal. The structure characteristic responds include the information of structure system respond, deducing according to the theories, we can identify the structureparameters from the structure characteristic signal. In the views of the energy,frequency energy of characteristic respond is more concentrated near to the structureinstinct frequency; it raised the signal-noise ratio. Simulation express that waveletthreshold de-noising is incapable of the low signal noise ratio weak signal when theAmbient ground vibration respond signal frequency band overlaid the noisefrequency band mutually. While withdrawing the structure characteristic signal isactually a better method to de-noising, and has already got good results insimulation and experiment.3. Frequency domain method based on energy—damage. When the structureappears to be damaged or the system appears to be broken down, the transferfunction will be changed, the amplitude-frequency response characteristics andphase-frequency response characteristics will have different change among differentfrequency. Take amplitude-frequency response characteristic into consideration, ithas different roles in repress and strengthen to different frequency-band importedsignal. When ambient ground vibration as the importing signal excite, the structuresystem damage will take a different role in different frequency-band signals, usually,it will repress some frequency-band signals and strengthen some frequency-bandsignals. Therefore, compared to normal system output, there will be a biggerdifference inside the energy of the signal although in the same frequency, it makessome signal energy in some frequency-band lower, while makes signal energy inother frequency-band greater. Therefore, there involves abundant structure damageinformation in the energy of each frequency-band signal, the change of one or somefrequency-band energy represents a kind of damage. This paper carries on somesimulation research in the energy-damage method, inquiries into the possibility inthe structure damage identification application by this kind of frequency domainmethod. Appling small wavelet analysis to decompose the frequency, adopting therandom data processing method, identifying noise frequency energy and structurecharacteristic frequency energies effectively, building up the relation ofcharacteristic vector-damage.4. Time domain identification research on incomplete testing information. In anactual engineering, even for shear model time domain parameter identificationmethod, there usually can't get all the floors information such as accelerations,speeds and displacements, or there acquired the information that has a greatinstrumental error, or can only acquire the acceleration information, all of the abovebelong to the incomplete information. As the speed and displacement is unknown,this paper carries on the research in the problems such as numerical integrator error and integrated first guess etc. and puts forward the integral errors to be the conceptof the low frequency trend influence, raises the parameter identification accuracy.For those that one can't get all acceleration information for once, this paper adoptthe sub-structure method to process the data, the numerical calculation andexperiment analysis result express that the result the complete informationparameter identification agrees with that the sub-structure method.5. The experiment research on steel-concrete frame model physics parameteridentification. First carried on the static experiment to the model, acquired a moreaccurate parameter, use the D-value method and test modified, acquire each floorstiffness. Accord to ambient ground vibration acceleration respond, adopting thefrequency domain and time domain method respectively to carry on the layer rigidityidentifying. Although frequency domain method can acquire 3 natural frequency andmodes, it can't identify the structure physics parameter according to shear model.Apply the complete information and the sub-structure time domain methodparameter identification; verifying that the time domain theories and methods areeffective in engineering structure dynamic detection, also that time domain methodbased on shear model can identify general frame structure's physics parameter. Theambient ground vibration dynamic respond signal include a lot of frequencyinformation that have something to do with the excitation, this part of information isinterference signal for frequency domain method, but for time domain method it is akind of valid information in identifying the structure parameter.