Papers by Keyword: Model Updating

Abstract: Because of the critical role that bridges play in land transport networks and broader economy, the assessment of existing bridges is gradually becoming a global concern. Structural health monitoring (SHM) systems have been installed on many bridges to provide data for the evaluation of bridge performance and safety. The challenge for bridge engineers is now to make use of the data and convert them into usable information and knowledge. Integrating SHM data with reliability analysis procedures offers a useful and practical methodology for bridge assessment since reliability is an important performance index and reliability-based procedures have the capability of accommodating uncertainties in structural models, responses, loads and monitoring data. In this paper, an approach for integrating SHM data in a reliability assessment framework is proposed. The reliability of the bridge is quantified by incorporating SHM information in the resistance, load and structural models. Advanced modeling tools and techniques, such as finite element analysis, finite model updating and Bayesian updating, are used for the reliability computations. Data from the SHM system installed on the Newmarket Viaduct, a newly constructed, 12-span, post-tensioned box girder bridge erected by the balanced cantilever method in Auckland, New Zealand, are also presented in this paper and used to explain the proposed framework.

Abstract: This paper presents a new method to study the impact factor of an old bridge strengthened with high strength materials based on the model updating technique. Using the genetic algorithm (GA) by minimizing an objective function of the residuals between the measured and predicted responses, the bridge and vehicle coupled vibration models were updated. Based on the displacement relationship and the interaction force relationship at the contact patches, the vehicle-bridge coupled system can be established by combining the equations of motion of both the bridge and vehicles. The simulated results show that the present method can simulate precisely the response of the tested bridge.

Abstract: Model updating techniques are used to modify structural model for more accurate predictions of dynamics behavior. A simple survey on the model updating methods and correlation criteria is presented. Based on the inverse eigensensitivity method (IESM) and modal assurance criterion (MAC), a scheme of model updating for structures is presented and realized by user defined subroutine combined with APDL in commercial software ANSYS®. A four-DOF spring-mass system is assumed and updated, from which the predicted frequencies and MAC values are satisfied compared to the actual dynamics characteristics. This gives evidence that the presented model updating scheme is feasible and efficient. Furthermore, a cylindrical shell structure containing global and local modal information is established to research the updating ability of the scheme on some focused local modal information. The results due to the updated model of cylindrical shell structure show that not only the global modal data but also the local modal data have a good agreement with that of the actual structure.

Abstract: Aiming at the result of Mean-Shift tracking method is not satisfactory when color of the target is similar to the back ground or another similar object is close to the target, a real- time target tracking method combined with Mean shift and color co-occurrence histograms (CCH) was proposed in this paper. The method used CCH to represent target model of the Mean-Shift. And then the Mean-Shift was used to locate the target position. Moreover, the studied model updating strategy based on multi-scale CCH and the similarity measure of Bhattacharyya value is constructed in the method. Experiments in the complex environment were done. The results show that the proposed method has more accurate target locating and better robustness than the traditional Mean-Shift.

Abstract: The establishment of an effective finite element model for bridge structure is essential in the health monitoring system for Bridge. A new updating method for static model using response surface method is proposed in this paper, and the main procedures are given with an example of a special-shaped bridge. Firstly, the bridge deflection and strain data in designed load case are obtained. Several groups of combined parameters which are chosen based on the principle of uniform design method are selected to conduct calculation through finite element software. Finally through response surface fitting and optimization, the updated bridge finite element model is obtained. The results show that the updated model is approximate to the real bridge and this updating method is rational and practical.

Abstract: In this paper, the finite element model of a steel jacket scale model is updated using modal parameters identified by modal test. Updating parameters are selected based on sensitivity analysis by solving modal energies. And then, a two-steps updating process is carried out using different parameters and the Cross-Model Cross-Mode (CMCM) model updating method is applied in each step. Results indicate that with selection of updating parameters and sensitivity analysis, CMCM method can update the finite element model with physical meanings.

Abstract: Finite element model updating using incomplete complex modal data for unsymmetrical damping system with genetic algorithm is presented. The genetic algorithm method and finite element model updating based on optimization method using complex modal eigenvalue are introduced. The updating for simulation example about a flexible rotor system which is a typical unsymmetrical damping system is performed using bearing stiffness, bearing damping and diameter moment of inertia parameters. The results show that the maximum error of updated parameters is 0.15% and the objective function of genetic algorithm is 0.0081. The study demonstrates that the finite element model updating method using incomplete complex modal data with genetic algorithm is feasible and effective for unsymmetrical damping system.

Abstract: In view of open-pit mine complex special terrain, to improved method of constructing triangulated irregular net and combined with the extended boundary, that can remission the phenomenon that steps were flattened and the problem of inefficiency mining area model update. Using constrained triangulated irregular net once generation algorithm, through extraction of spatial data, establish topological relationships and spatial indexing, eventually build a constraints of triangulated irregular net within the boundary constraint line. Combining extended boundary with the triangulated irregular net generated algorithm, can realize the establishment partial model as well as partial and overall model splicing. Thus enhanced the efficiency of the mining area overall model updating.

Abstract: The frequencies and vibration modes of a launch platform are acquired through finite element simulation, and their actual values are obtained through modal test. On this basis, constructing objective function for the structure modal parameter relative residual error to be minimum, can transform model updating problem into optimization problem. Then the trust region algorithm is adopted to solve this optimization problem. This algorithm bears better robustness and computing efficiency. Through model updating, the frequency and vibration mode errors are reduced, supplying a basis for further simulation.

Abstract: Model updating techniques are used to update the finite element model of a structure, so that updated model can be predicted the dynamic behavior of an actual assembly structure more accurately. Most of the model updating techniques neglects damping and so amplitudes of vibration at resonance and antiresonance frequencies cannot be predicted by using of these updated models. In dynamic design of structures predicting of these properties is necessary. This paper presents a new technique to create an accurate finite element (FE) updated model of complex assembly structures consisting of substructures and real joint by considering damping of them. Given the fact that modal testing of real joints (such as bolt with some washers) are almost impossible. The updated model of assembly structure is obtained in four steps. In the first step, mass and stiffness matrix of substructures, joint and assembly structure are updated using modal data and Eigen-sensitivity approach. In the second step, damping of assembly structure is identified using complex modal data and updated mass and stiffness matrices which are obtained in first step. In the third step, the effect of damping of joint on frequency response functions (FRFs) extracted from updated model was shown. In the forth step, damping matrix of joint is updated by using FRF-based model updating method and finally damped updated model of assembly structure compared with measured data.