Structural measurements for model updating are limited, and the global responses are usually not sensitive to the local and small damages. Therefore, it is full of challenge to identify small and local damages using global responses of structure. The updated parameters have different effects on the structural response. In the model updating, the large sensitivity parameters converge quickly and relatively small sensitivity parameters cannot be effectively corrected. In this study, the effects of structural measurements on the model updating results are investigated. The method to update the parameters with large difference in sensitivity based on response surface method is proposed. Firstly, the samples of small sensitivity parameter are adjusted to generate new samples according to the difference of sensitivities. Then, response surface models are constructed using the new samples and the original characteristic information. At last, model updating is carried out based on the new response surface models and the updated results inversely computed to get the final results. The numerical simulation of a space truss structure is adopted to verify the efficiency and feasibility of the method.
The main cables are key complements of the suspension bridge. The temperature properties of main cables have significant effects on the structural responses of entire bridge. This paper presents a numerical method for temperature analysis of main cable for suspension bridge. The finite element (FE) model of main cable section is developed as homogeneous material using Plan elements. The material parameters for thermal analysis are determined based on equivalent principle. The third type thermal boundary conditions of a sunny day are calculated and then applied on the FE model for transient thermal analysis. The numerical results are compared with the experimental measurements of a full scale main cable for validation of the thermal analysis method. The results present good agreement with respect to the measurements. The temperature variations exactly explicate the changes of environmental conditions such as solar radiation and ambient temperature of daily. This FE model-based thermal analysis can provide a high effective and precision method for analysis of temperature and induced structural responses of main cables and suspension bridge.
Harsh service environment degenerates the performance of bridges even leads to catastrophic collapse. Structural temperature has been widely recognized as one of the most negative environmental effects on bridges. The structural responses are deeply affected by the variation and distribution of temperatures on bridges. Therefore, identifying the correlations between them is a significant issue for structural safety assessment. In this study, the relationships between the temperature induced static response and the surrounding weather factors are investigated based on the long-term field measurements of a long-span suspension bridge. The correlations of the meteorological parameters between the bridge filed and the nearby weather station, and the relations of structural static responses to the air temperature, are investigated. The results indicate that relationships of meteorological parameters between nearby weather station and the bridge field can be predicted. The correlation between the static responses and the air temperature and is remarkable with high correlation coefficient. The conclusions are expected to provide reference for the design and evaluation of longspan suspension bridges.
Structural temperatures and their uneven distributions have significantly negative effects on bridges. It is very important to accurately calculate the structural temperatures. Structural temperatures are deeply affected by the surrounding weather conditions, and the environmental wind is a critical factor. In this study, the wind effects on the thermal analysis of bridges are investigated using numerical simulation. Frist, the traditional theory and method are briefly introduced to show the important effects of wind on structural heat transfer analysis. Then, a new approach is proposed to take account of the wind effects for temperature analysis of bridges. At last, numerical study based on the finite element transient heat transfer analysis of a box-girder bridge is carried out and discussed to verify the proposed method. The results indicate that the proposed method is more reasonable than the traditional methods. This method can be easily implemented in practice for temperature analysis of bridges.
Structural temperature has been widely recognized as one of the most negative environmental effect on bridge. In this study, the temperature distribution of a large rigid-continuous concrete box girder bridge is investigated combining the numerical simulation and the field measurements. A temperature sensor system has be installed on the bridge for field monitoring the structural temperature. For simulation study, the fine tow-dimensional finite element (FE) model of box girder section is first constructed. Then, the time-dependent thermal boundary conditions are determined to extensively take account of environmental factors resulting of thermal effects on bridge. At last, transient heat transfer analysis is implemented on FE model and corresponding time-dependent temperature distribution is obtained. The analytical results are compared with the measurements for validation of the thermal analysis method. The results have very good agreements with the measurements, and the temperature variations exactly explicate the changes of environmental conditions such as solar radiation and ambient temperature of daily. The temperature simulation provides a foundation for the structural analysis of temperature induced effects.
The field measurements of structures are very important to the structural finite element (FE) model updating because the
errors and uncertainties of a FE model are corrected directly through closing the discrepancies between the analytical
responses from FE model and the measurements from field testing of a structure. Usually, the accurate and reliable field
measurements are very limited. Therefore, it is very important to make full use of the limited and valuable field
measurements in structural model updating to achieve a best result with the lowest cost. In this paper, structural FE
model updating is investigated in the point of view of solving a mathematical problem, and different amount and
category of structural dynamic responses and static responses are considered as constraints to explore their effects on the
updated results of different degree and types of structural damages. The numerical studies are carried out on a space
truss. Accounting for the numerical results, some inherent phenomena and connections taking account of the updating
parameters, output responses and the updated results are revealed and discussed. Some useful and practicable
suggestions about using the field measurements for FE model updating are provided to achieve efficient and reliable