Study On Simultaneous Identification Of Structural Damage And Load Based On Incomplete Measurements

Damage detection and load identification of structures with unknown input and incomplete measured output information is an important problem in the area of identification of civil engineering structures. A method based on dynamic response sensitivity is therefore proposed to simultaneously identify structural physical parameters and input time-history from only several responses of structures. The identified structural physical parameters are used to detect structural local damages. Some key problems of the proposed method are studied in the dissertation. Main contents are as follows:(1) A method based on dynamic response sensitivity is proposed to simultaneously identify structural physical parameters and input. The input force on structure is represented by using orthogonal polynomial approximation. By representing the input force on structure using orthogonal polynomial approximation and perturbing structural physical parameters, the orthogonal expansion coefficients and the fractional stiffness of structural elements are adopted as the force parameters and the structural physical parameters respectively, which are need to be identified. The sensitivity of structural dynamic response with respect to orthogonal coefficients and structural physical parameters is derived. The identification equation is set up and is solved with the damped least-squares method in an iterative process. Numerical simulation results show that the proposed simultaneous identification algorithm can simultaneously identify structural physical parameters and input from only several responses of structure.(2) The proposed simultaneous identification algorithm is extended to identifying damage and load of structure under unknown support excitation. The support excitation on structure is represented by using orthogonal polynomial approximation. The simultaneous identification equation of structural local damages and unknown support excitation is derived based on dynamic response sensitivity. The regularization method is used to solve the identification equation in an iterative process. Numerical simulation and experimental results show that the proposed algorithm has higher identification accuracy when the level of measurement noise is lower. The regularization is helpful for improving the anti-noise ability of the algorithm. When the level of measurement noise is higher, the algorithm can not accurately identify structural damages, but the identified support excitation after removing the linear trend can reflect the true support excitation.(3) A method based on dynamic response sensitivity is proposed to simultaneously identify local damages in a selected substructure and the interface forces between substructures from the dynamic responses on the selected substructure. The motion equation of substructural system is deduced. These interfacing forces between substructures are represented by orthogonal functions, and the sensitivity of the dynamic responses on the selected substructure to the substructural physical parameters and the orthogonal expansion coefficients of the interface forces is derived. An identification equation is set up and is solved by using regularization method in an iterative process. Numerical simulation results show that the proposed method can identify local damages and interface forces of the selected substructure from only several responses of the substructure.(4) A method, which uses the measured responses of one substructure in a complex structural system to detect local damges in another substructure in the same structural system, is proposed. The identification equation of the coupling forces is formulated in state space. The sensitivity of interface forces to substructural physical parameters is derived. The equation of local damage identification in the selected substructure from the interface forces is set up and is solved with regularization method. Numerical simulation results show that the proposed damage detection method for substructure based on interface forces can accurately identify local damages of the substructure far from response measurements.(5) A probabilistic method is proposed to identify damages of structures with uncertainties under unknown input. The uncertain equation for simultaneously identifying structural damage and load is derived based dynamic response sensitivity. The effect of uncertainties caused by measurement noise on the identified parameters is investigated with data perturbation technique and Monte Carlo method. The formula of probability of identified damages is further derived using the probabilistic method. Numerical simulation and experimental results show that the simultaneous identification method based on probability can locate and quantify multi-damages on structure, and accurately identify structural support excitation.