Study On The Structural Damage Identification Based On Acceleration Transmissibility Function

During the long servicing period, large civil engineering structure will be subject tothe problem of structural damage due to all kinds of load effect and the influence ofuncertain external factors. The destruction of the structure will lead to disastrousconsequence. Structural damage identification can quickly and accurately determine ifthe structure is damaged, the damage location and damage degree, so that the effectivemeasures can be timely taken to remedy, avoiding major engineering accidents. Theexcitation information which is difficult to measure accurately is usually needed by thestructural damage identification method, however, not only the excitation informationbut also the modal parameter are not necessary for the method of structural damageidentification based on acceleration transmissibility function. In this paper, a method ofstructural damage identification with the acceleration transmissibility function ispresented. The main contents are as follows:(1) The research background and significance of structural damage identificationare introduced. The recent progresses and research status of the structural damageidentification based on vibration are reviewed.(2) The concept of transmissibility function and the basic theory of principalcomponent analysis are introduced. The acceleration transmissibility function combinedwith principal component analysis is used to make damage alarming. First of all, theacceleration transmissibility functions between two adjacent points are calculatedthrough Fourier transform，and the transmissibility function matrix is constructed. Then,the principal component analysis is employed for the dimension reduction of thetransmissibility function matrix. The two dimensional PCA space scatter diagrams ofthe first two order of principal components between the healthy condition and theunknown condition are used to determine whether the structure is damaged. The resultsof the numerical simulation and shaking table model experiment of offshore platformshow that the method is effective.(3) The novel damage index which is used to determine the damage location isproposed with the transmissibility function. The damage location of brace damage ofoffshore platform is determined by comparing the damage index between two adjacentpoints. The results of the numerical simulation and shaking table model experiment ofoffshore platform show that the method is effective. (4) The concept of mahalanobis distance is intridued. The original data matricesare respectively constructed with the measured transmissibility function in healthysituation and damage situation. Principal component analysis is carried out on theoriginal data matrices, and the main components of the original data matrices in healthyand damage situation respectively, then the mahalanobis distance of the maincomponents between healthy and damage situation are calculated and used to assess thedamage extent. The results of the numerical simulation and shaking table modelexperiment of offshore platform show that the method is effective.