With increasing number of aging civil structures including bridges, the finite element (FE) analysis assumes key roles in the use of the maintenance and repair design, and structural health monitoring. Despite the cha...
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With increasing number of aging civil structures including bridges, the finite element (FE) analysis assumes key roles in the use of the maintenance and repair design, and structural health monitoring. Despite the changes in dynamic characteristics of the aging structures from the nominal condition due to deteriorations or possible damages, limited attention has generally been paid to the verification and validation (V&V) of the numerical models used in the dynamic analysis. In this paper, we describe some practical considerations on the systematic V&V especially for the modeling of existing and aging bridges by applying a series of V&V procedure to the bridge FE model. The applied V&V procedure includes: (1) experimental data acquisition by impact tests, (2) modelverification using grid convergence index, (3) sensitivity analysis to extract influential parameters to the comparative feature, namely the modal parameters, and (4) uncertainty quantification based on Bayesian inference. Posterior probability distributions of uncertain parameters in the FE model, especially material properties of the girders and slab, were then successfully derived in the uncertainty quantification procedure. The study also discusses some important considerations to improve implementation of V&V for the modeling of existing structures in terms of the verification procedure for complex FE models, the choice of comparative features, and the appropriate experimental data acquisition.
In this paper, we illustrate a formal calibration, validation, and verification process that includes uncertainty in an internal state variable plasticity-damage model that is implemented in a finite element code. The...
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In this paper, we illustrate a formal calibration, validation, and verification process that includes uncertainty in an internal state variable plasticity-damage model that is implemented in a finite element code. The physically motivated continuum model characterizes damage evolution by incorporating material uncertainty due to microstructural spatial clustering. The uncertainty analysis is performed by introducing material variation through modelvalidation and verification. The effect of variability in microstructural clustering and boundary conditions on the sensitivities and uncertainty of the plasticity-damage evolution for the 7075 aluminum alloy is characterized. The results show the potential of this methodology in the evaluation of material response uncertainty due to microstructure spatial clustering and its effect on damage evolution. For damage evolution, we have shown that the initial isotropic damage evolved into an anisotropic form as the deformation increased which is consistent with experimentally observed behavior for 7075 aluminum alloy in literature. Also, the sensitivities were found to be consistent with the physics of damage progression for this particular type of material. Through the sensitivity analysis, the initial defect size and number density of cracked particles are important at the beginning of deformation. As damage evolves, more voids are nucleated and grow and the sensitivity analysis illustrates this as well. Then, voids combine with each other and coalescence becomes the main driver, which is also confirmed by the sensitivity analysis. This work also shows that the microstructurally based damage evolution equations provide an accurate representation of the damage progression due to large inter-metallic particles. Finally, we illustrate that the initial variation in the microstructure clustering can lead to about +/- 7.0%. +/- 8.1%, and +/- 9.75% variation in the elongation to failure strain for torsion, tensile, and compressive
Daily 2009 surface winds from five model, remotely-sensed, and reanalysis wind products are compared with measurements from three fixed mooring buoys located in the west equatorial Pacific (0 degrees N, 165 degrees E)...
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ISBN:
(纸本)9781457710056
Daily 2009 surface winds from five model, remotely-sensed, and reanalysis wind products are compared with measurements from three fixed mooring buoys located in the west equatorial Pacific (0 degrees N, 165 degrees E), the central equatorial Pacific (0 degrees N, 170 degrees W), and the eastern-central equatorial Pacific Ocean (0 degrees N, 140 degrees W). The cross-correlation coefficients between these five wind products and the buoy winds are all statistically significant at the 95% confidence level, ranging from 0.77 to 0.97 for the zonal winds and 0.45 to 0.93 for the meridional winds. However, a systematic positive/negative bias was found in wind directions in all wind products at the central/eastern central Pacific Ocean, which could have an impact on local wind stress curl field in the region.
The complex interaction and the high costs of modern manufacturing systems make it necessary to evaluate their use performance. Production scheduling problem is one of the key problems of research of manufacturing sys...
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ISBN:
(纸本)9783037851333
The complex interaction and the high costs of modern manufacturing systems make it necessary to evaluate their use performance. Production scheduling problem is one of the key problems of research of manufacturing systems since with a proper scheduling, the utilization of resources is optimized and orders are produced on time which improves the shop performance and associated cost benefits. However the complexity of modern production systems makes the use of analytical tools more difficult. Thus a computer simulation model of the existing computer integrated manufacturing system based on the control logic that describes the operation of the system is developed to test the performance of different scheduling rules with respect to mean flow time, machine efficiency and total run time as performance measures. According to the results of experiments, the model agrees with the real system.
Two different implementations of Gaussian process (GP) models are proposed to estimate the vertical total electron content (TEC) from dual frequency Global Positioning System (GPS) measurements. The model falseness of...
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Two different implementations of Gaussian process (GP) models are proposed to estimate the vertical total electron content (TEC) from dual frequency Global Positioning System (GPS) measurements. The model falseness of GP and neural network models are compared using daily GPS TEC data from Sutherland, South Africa, and it is shown that the proposed GP models exhibit superior model falseness. The GP approach has several advantages over previously developed neural network approaches, which include seamless incorporation of prior knowledge, a theoretically principled method for determining the much smaller number of free model parameters, the provision of estimates of the model uncertainty, and a more intuitive interpretability of the model.
model calibration and modelvalidation are two important aspects for microscopic traffic simulation modeling theory. People often pay attention to the former one but ignore the latter one, or pay attention to the macr...
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ISBN:
(纸本)9789806560482
model calibration and modelvalidation are two important aspects for microscopic traffic simulation modeling theory. People often pay attention to the former one but ignore the latter one, or pay attention to the macroscopic validation procedure but ignore the microscopic validation procedure because of the difficulties of field data collection. This way often leads to failure in model applications. In this paper, the key technology for model verification and validation is studied with the field data collected by "Five-Wheel experiment system" and the establishing procedure of a new integrated cognitive car-following model. The results indicate that the straight comparison technique and the statistical inference technique are all effective method for model verification and validation.
An overview of system dynamics is given. It includes modelling, comparison with and correction of the mathematical model with the use of measurements, the treatment of uncertainties in modelling and testing, and probl...
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An overview of system dynamics is given. It includes modelling, comparison with and correction of the mathematical model with the use of measurements, the treatment of uncertainties in modelling and testing, and problems arising in experimental analysis. This overview examines structural analysis from the point of view of system engineering in order to state the latest results, to mention the available modern tools, and to present some future developments. Additionally, the connections and interactions with various disciplines are exhibited in order to counteract narrow specialization and to allow the reader a glance into other fields.
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