Advanced Materials Research Vols. 163-167

Abstract: This study focuses on test loading program and evaluation for pedestrian bridge. On the basis of the finite element analysis, numerical model of Lv River Bridge, which is a steel box pedestrian suspension bridge, is established. Moreover, field static load test is done and the results of tests are compared to the theoretical values. Results show that the measured result fits well with the theoretical result and bridge is in the situation of elastic deformation, and the strength and stiffness satisfy the need of design.

Abstract: Nowadays structure construction and monitoring, hazard forecasting depends more and more on scientific prediction methods. This paper focus on prediction method, which based on GM(1,1) model of Gary Theory. With a set of dynamic monitoring data from one structure, we introduce the modeling method of old information model, new information model and equal dimension new information model. An analysis of these prediction models reliability is performed to compare these models. The result of these models can predict the structure settlement proved that a suitable prediction method could provide help to structure safety and reduce unnecessary lost.

Abstract: Effect of computational patterns of principle component analysis (PCA) on moving force identification (MFI) is studied in this paper. The motion equation of bridge due to moving vehicles are formed, the relationship between moving axle loads and caused bridge responses are established for the PCA-based MFI method in time domain. The measured bridge responses are rearranged in a matrix form for easily performing PCA and are adopted for obtaining an acceptable solution to the MFI problem. A laboratory experimental study was conducted to assess effectiveness and robustness of the PCA-based MFI method. The illustrated results show that the PCA-based method is an easy executive and more effective method for the MFI problem. The PCA computational patterns should be appropriately considered due to its higher sensitivity on response catalogues.

Abstract: In this paper, a time domain structural damage detection approach based on Kalman filter and least square estimation is proposed for structures under limited input and output measurements. First of all, the dynamic parameters of the structure, such as stiffness and damping coefficients are identified by sequentially utilizing the extended Kalman estimator and the least squares estimation. Secondly, after the structural dynamic parameters are gained, the normal Kalman filter and least square estimation is used to identify the state vector and unknown input of the structure, and the changes of the structure such as reducing of the stiffness are regarded as ‘additional unknown input’. Then the changed parameters can be calculated by analyses the connection between ‘additional unknown input’ and changing parameters, Local structural damage in the structure can also be detected by tracking the changes in the identified values of structural dynamic parameters in time domain at element level, e.g., the degrading of stiffness parameters. Numerical example of detecting structural local damages in a four story share building illustrates the efficiency of the proposed approach.

Abstract: Large longitudinal displacement would be generated by vehicle braking force in the girder of self-anchored suspension bridge, just as the floating system of cable-stayed bridge. In this paper, taking Pingsheng bridge as an engineering example, the vehicle braking force models are established according to traffic survey, furthermore dynamic response and vibration reduction of the bridge under vehicle braking force are investigated by finite element analysis. The results show that the longitudinal displacement of the girder is relatively large, and it can effectively be controlled by viscous dampers with optimal parameters.

Abstract: The damage alarming analysis based on wavelet packet energy spectrum is performed with regard to the experimental data of Benchmark steel frame structure and online monitoring data of Runyang Suspension Bridge, on the basis of which the damage alarming effects using various wavelet functions are investigated in detail. Results reveal that the Daubechies wavelet functions and Coiflets wavelet functions are applicable to structural damage alarming.

Abstract: A time domain method on bidirectional moving vehicle load identification from plate bridge responses is proposed in this paper. The bridge deck is modeled as a plate based on the theory of plate and the vehicle loads are modeled as two groups of axle loads moving on top of the bridge deck in two opposite directions. The equation of motion of the bridge-vehicle system is formulated in state space and the bidirectional moving load identification problem is formulated as a damped least-squares problem and further solved using the dynamic programming method with regularization on the solution. Some numerical simulations show that the proposed method is correct and effective and can be used to identify the bidirectional moving vehicle loads from the bridge responses with an acceptable accuracy.

Abstract: A metamodel can be represented by the forms of mathematical equations (response surface models) or neural networks (black-box models) in the interest of correlating the inputs (parameters) with the outputs (responses) of a physical system. In view of little relevant research, this paper attempts to use response surface models as surrogates for FE models due to the provision of explicit equations and easy implementation in the aspect of modeling updating. Metamodeling is achieved by using the design of experiment involving the 2k factorial design and the central composite design for parameter screening and structural input-response modeling respectively. The feasibility of the proposed method has been demonstrated using a numerical beam example which proves the satisfactory performance of employing such metamodels in model updating based damage identification.

Abstract: Evaluation of slope stability in the hydropower project construction is extremely important. This Cloud Model will be introduced to the matter-element extension, the extension assessment is proposed based on the sutra field division of the slope stability assessment model. This method combines the Cloud Model theory and the advantages of the extension assessment .On the one hand, the division of the sutra field by means of Cloud Model can overcome the "hard" division of the evils. On the other hand,with different values of Cloud Drops as a sutra field, the statistical results of Cloud Drops can be used as last stable assessment results. Project case study shows that compared with the conventional method, results of the method of extension are more accurate, which fully accorded with the actual state, proving optimized based on Cloud Model extension assessment of slope stability feasible and effective.

Abstract: The construction of a modern long span rigid frame box girder bridge gives impetus to the development of structural analysis design theory and construction technology. Moreover, it makes construction monitoring of the rigid frame box bridge a significant research subject. Construction monitoring of the rigid frame box bridge signifies regulating the structure’s internal force and alignment in the construction process and completion state, and thence satisfies the designed expectation. Based on the construction monitoring of Liang-Ji Canal Bridge project, the construction process and the designed completion state have been simulated and analyzed at a certain precision level [1]. A plane bar finite element computational model is established, and the alignment and internal force of the bridge in each construction stage are analyzed. Then the simulation analysis of construction process is derived according to its construction characteristics [2]. Through systematical research on the form work elevation and the stress monitoring of the cantilevers during the cast-in-situ construction, the factors which influence deflection and stress are analyzed. The elevation is predicated by the Kalman's filter estimation, the modified grey model and the combination of these two methods. The stress monitoring error and corresponding reasons are analyzed. The measured results show that the combination of the two approaches can improve prediction accuracy. The presented analysis, processing and control methods accumulate many experiences for the design and construction of the long span box girder rigid frame bridge.