Papers by Keyword: Model Updating

Abstract: This work shows the results of monitoring of Santa Maria del Suffragio (Anime Sante) church, L’Aquila, Italy. The historical building was stricken and damaged by mainshock of April 6, 2009; the dome is the structural element that has been seriously hit by seismic event. The ambient response analysis of global structure and dome element enable to improve the FE model by model updating methodology using modal data. The identification techniques furnish useful information concerning the structural and mechanical properties of dome’s structure, these parameters are needed to evaluate the appropriate design of rebuilding and structural rehabilitation of dome. The geometric configuration and the self-weight of lantern induce to an independent dynamic response of macro-element against the behaviour of dome generating the first mechanism of collapse and the failure of dome shape. Different retrofitting configurations for the dome have been proposed in this paper.

Abstract: Analytical models of the actual structure often differ greatly from their as-built counterparts. Model updating techniques improve the predictions of the behavior of the actual structure by identifying and correcting the uncertain parameters of the analytical model. This paper presents a new model updating technique to improve the finite element analysis model by updating design parameters using strain measurement based on affine scaling interior Algorithm. Static strain measurements are more reliable and realistic than acceleration data in practice. Numerical examples are presented to study the application of the method.

Abstract: with the development of finite element technology, finite element model is becoming to the main analysis tool. However, because some theoretic assumptions, unsuitable constraint and uncertain material property are applied, the simulation result of finite element model isn’t different from the testing data. In order to improve the design quality and safety of spacecraft, this paper deduced the formula of spacecraft finite element updating, developed the spacecraft finite element model updating system, the software mainly of five parts: the frequency response function calculation, the loading inverse solution, the finite element model updating, the data display, virtual experimentation. Software can complete exciting force inverse, parameter sensitivity analysis, parameters screening and finite element model updating. The calculation result of updated finite element model is in accordance with testing curve shape on the main vibration direction, first-order frequency error is ±5%, response error is ±10%. Software meet the need of finite element model updating, it provide a software base for spacecraft design.

Abstract: Based on the artificial neural network, the parameters of a steel truss are identified. And the finite element model of truss is corrected. In order to improve the efficiency of model updating by artificial neural networks, the momentum is introduced into the back propagation algorithm. Based on the theory of probability and mathematical statistics, the expectation confidence interval of the measured deflections and strains is obtained. In this way, the samples to train the neural network are optimized. The numerical results show that the back propagation neural network proposed on this paper is able to correct the finite element model of the truss effectively.

Abstract: To handle occlusion and accumulation error in tracking procedure, a novel method is proposed. Firstly, the object feature is modeled with kernel based color histogram. Then, mean shift is used to localizing the object with Kalman filter providing initial iteration location and scale. Object observation value is acquired by weighting the similarities of hue and saturation in x and y-directions. Finally, occlusion and scene disturbance are judged by maximal similarity and the matching deviation, so as to selectively update the object model. To suppress the accumulation error, the noise covariance is updated according to the iteration error in the latest N frames. Experimental results show that the proposed method is robust in tracking the occluded objects under complex scene.

Abstract: This study was of two phases, one aspect tailored towards matching of the natural frequencies between experimental and finite element results and the second, focused on the effect of damping on the frequency response functions. The experimental Modal Analysis was performed on the real structure to characterize the dynamic behavior in terms of modes, natural frequency and damping using Bruel and Kjaer software. The base of the enclosure was clamped and could be an area of energy dissipation and a source of damping. This boundary condition was model with imaginary joint elements. The dynamic analysis was realized using the Lanczos tool in ANSYS 12 finite element code to extract the modes and also harmonic response analysis was conducted to get the response functions. The linear and rotational stiffness of the boundaries and structural stiffness of the panels were used as updating parameters, tailored towards minimisation of the percentage error in the natural frequencies. The inclusion of damping reduced the amplitude of vibration.

Abstract: Dynamic behaviour of a welded structure made from thin metal sheets which has a large flat surface and has been assembled together by a number of scattered spot welds is investigated. An impact hammer and roving accelerometers are used in the modal tests to provide data to update the FE model. NASTRAN Solution 103 is used to compute natural frequencies and modes of interest. The large error of the initial FE model is largely reduced mainly by adjusting a crucial parameter of the bending moment of inertia ratio, 12I/T**3.

Abstract: Model updating based on Bayesian theory for the prediction of natural frequencies of full prestressed concrete beam has been developed. Morris screening method is employed to study the sensitivity of model parameters and elastic modulus and density of concrete are determined to be updated. Cooperative work between finite element analysis program and Markov chain generating program is realized, and multiple chains with different starting points are designed to obtain the posterior distribution of model parameters. It is found that standard deviations of posterior estimates decrease compared to those of prior distributions. In addition, different starting points are selected to discuss their influence on posterior estimates of model parameters. On reducing the uncertainty of posterior estimate, the difference of each natural frequency used as witness resource is compared.

Abstract: The discrete finite element (FE) model often cannot reflect structure characteristics accurately due to imply more idealistic assumptions and simplifications. Therefore, it is necessary to update FE model for structural damage identification, response calculation, safety evaluation, optimization design, and so on. This article will illustrate respectively three key steps of updating parameters selection, target function selection and optimization method in process of dynamic FE model updating of footbridge structures based on ambient excitation, and put forward a feasible updating method: combine empirical method with sensitivity analysis method to select updating parameters; joint natural frequencies, MAC and modal flexibility as target function; adopt optimization algorithm based on the optimization theory.

Abstract: It is difficult in finite element model(FEM) updating, because the essence is a mechanical anti-question solving. In the paper, the suppositional material method is utilized to model the FEM of a mirror frame system, and the required updating parameters are defined. The functions between the natural frequency and the updating parameters are established based on the response surface method. Based on the response surface model and the modal experiment results, the sum of absolute value of relative errors between the results of experiments and simulations is defined as the optimization objective, four required updating are identified automatically. The first three natural frequencies of updated mirror frame system are better accordant with the experiment results, which proves the method correct and reliable.