Papers by Keyword: Flexibility Matrix

Abstract: As structural health problems are becoming more and more important, a neural networks model is introduced to detect structural damage. The structural modal flexibility matrix can be accurately constructed by the natural frequency and modal information. All elements of changes in the modal flexibility matrix are looked on as inputs of the networks. Damage locations and extents are both considered with different outputs in the present study. A simply supported truss structure is studied with different damage cases. To localize damage, one case is chosen as location input/target pairs to train the present BP network model. But to identify damage extent, two cases are chosen as extent pairs to train. Although modals of BP neural networks with different outputs are presented for different damage detecting schemes, it is more difficult to ascertain damage extent than location. The results indicate that the present BP neural network modal can effectively detect damage of structures with changes in the flexibility matrix between the intact and the damaged cases.

Abstract: Applied to the structural damage identification, Modal Flexibility is better than the Modal Frequency and Modal Displacement, the indicators of Flexibility Curvature are effective and sensitive. This paper proposes a new detection indicator which is Flexibility Curvature Difference Rate (FCDR) that by using the change rate of diagonal elements of flexibility curvature difference when before and after damage. The numerical examples of a simple beam, a continuous beam and a frame with the damage conditions of the different positions and different degrees are used to verify FCDR. The result shows that FCDR can well identify the numerical examples damages, and sensitively diagnose the damage near the supports of beam and the nodes of framework.

Abstract: Based on the flexibility matrix method, the elastohydrodynamic lubrication performance of journal bearing are studied. Comparisons are made the effect of elastic deformation on the center orbit of connecting rod big end bearing. The results show that bearing eccentricity has far exceeded 1 near the maximum combustion pressure, considering the elastic deformation of connecting rod big end bearing, changing trend of bearing center orbit is the same at other times.

Abstract: A simple and robust methodology is presented to identify damages in a structure using changes in vibration data. A comparison is made among damage indicators such as natural frequencies, mode shape data, curvature damage factors and flexibility matrices to study their efficacy in damage assessment. Continuous ant colony optimization (ACO_R) technique is used to solve the inverse problem related to damage identification. The outcome of the simulated results demonstrates that the flexibility matrix as a damage indicator provides better damage identification.

Abstract: In accordance of the principles of stress continuousness and displacement coordination, the interactions model of pile and pile, pile and soil are set up;Accoring to the symmetry of the models,1/4 of the models are extracted to set up three-dimension multipile composite foundation models.The flexibility matrix of the three reinforcements are modified to build a global flexibility matrix with the consideration of cushion's compression; Interaction coefficients of the analytic calculation are lower than those of the finite element when pile lengthen is diversity.The comparison between the on-site measured data from the literature review and results of the analytic calculation shows the settlements in the analytic calculation are smaller than those in the measured data, and the model measurements are very close to the curves from the analytic calculation. All these prove that the analytic methods proposed by this research are accurate and may function as a reference to engineering.

Abstract: Vibration exists widely in people's life and production. Modal analysis for vibration system help to improve the running quality of the mechanical structure and prolong service life. This paper build a new discrete multi-freedom model to calculate the flexibility matrix of simple supported beam, and then use the flexibility matrix to calculate its modal parameters with matlab. In order to prove that the result is correct, this paper use classical continuous vibration theory to calculate the normal modal parameters, finding that the two results are basically the same and as the more discrete number, the result of discrete multi-freedom model more close to the result of continuous vibration theory. In view of this, the new discrete multi-freedom modeling method is proved to be true, and it also can provide the discrete modeling reference for modal analysis of complicated mechanisms.

Abstract: A new method called Grey Relation Modal Flexibility Curvature Difference (GRMFCD)is proposed and applied to the numerical experiment and experimental research of a substructure. The results show the ability of GMFCD to locate the inflicted damage and qualitatively evaluate its severity for single and multiple scenarios, with only a few lower order modal parameters. The effectiveness and advantages of GMFCD as compared to the flexibility indicators, such as the change in flexibility, the curvature of the flexibility difference, are demonstrated.

Abstract: Through the measured simply supported bridge's dynamic parameters, we can establish the finite element model of the structure.As the flexibility matrix can reflect the actual state of the bridge, making the actual measured flexibility matrix as a basis to inverse the bridge’s finite element model .Combined with the engineering practice static load test, we can assess the bearing capacity of the bridge according to inversion model bridge.

Abstract: In this study, damage localization of frame structures from seismic acceleration responses is explored using the DLV technique and ARX model for system identification. The concept of the DLV method is to identify the members with zero stress under some specific loading patterns derived by interrogating the changes in flexibility matrix of the structure before and after the damage state. Success of the DLV method for damage localization lies on the ability to identify the flexibility matrix. The ARX model, a discrete-time non-parametric auto-regressive system identification technique is adopted to identify the modal parameters (natural frequencies, transfer functions and mode shapes) from which the flexibility matrices of the intact and damaged structures are constructed. To explore the effectiveness of the DLV method, a five-storey steel model frame with diagonal bracings was considered for seismic shaking table tests. The damage conditions of the structure were simulated by partially removing some of the diagonals. With the flexibility matrices of both the intact and damaged structures synthesized on a truncated modal basis, the damage locations have been successfully identified by the DLV method for either single or multiple damage conditions, regardless of the damage locations. This study confirms the potential of the DLV method in the detection of local damages from global seismic response data for frame structures.

Abstract: The present study uses the Global Flexibility Index (GFI), which is the flexibility matrix’s norm. For cases of ambient vibration, in which excitations are unknown, the flexibility matrix is unavailable, and the GFI cannot make out. Using the ANSYS set up and fixes the modal of structure in the condition of Vibration model to a unit, and then put the modal in the condition of Vibration model to a quality. Get natural frequencies and mode shapes, make up flexibility matrix, and then calculate Global Flexibility Index. Measure the Index regularly. With the change of the Index, judge the damage degree of the bridge. A sharp increase in the index calls for further detailed investigation for appropriate actions, such as reinforcement or maintenance.