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Pan Z.,Nanjing Southeast University | Pan Z.,University of Maryland University College | Fu C.C.,University of Maryland University College | Jiang Y.,China Zhongtie Major Bridge Engineering Group
Journal of Bridge Engineering | Year: 2011

The long-term behavior of long-span prestressed concrete continuous rigid-frame bridges is significantly sensitive to creep and shrinkage. Therefore, it is important to accurately estimate creep and shrinkage effects. This paper presents modified prediction models that are based on the creep and shrinkage models in the existing bridge code. These modified prediction models match well with the test results of the high-strength concrete used in the continuous rigid frame of the Sutong Bridge in China. Results indicate that the accuracy in predicting creep and shrinkage can be enhanced greatly by measuring short-term creep and shrinkage on the given concrete and by modifying the prediction model parameters accordingly. Subsequently, the probabilistic analysis method of structural creep and shrinkage effects was studied. Uncertainty analysis of time-dependent effects in the given bridge was performed using the modified model, and results were compared with field-test data. Two approaches for mitigating deflections that were used in the continuous rigid frame of the Sutong Bridge are introduced. Finally, the time-dependent deflection at the midspan attributable to creep and shrinkage was analyzed. © 2011 American Society of Civil Engineers.


Wang C.,Huazhong University of Science and Technology | Wang C.,China Zhongtie Major Bridge Engineering Group | Zhu H.,Huazhong University of Science and Technology | Wang B.,China Zhongtie Major Bridge Engineering Group
Huazhong Keji Daxue Xuebao (Ziran Kexue Ban)/Journal of Huazhong University of Science and Technology (Natural Science Edition) | Year: 2012

The free response signal of structure was processed using complex wavelet transform. It was deduced that wavelet ridge included the information of structural modal frequencies and damping ratios. The wavelet ridges were extracted by dynamic optimization method, and then the modal frequencies and damping ratios were identified through least square fitting method. A numerical example signal added with different noise was analyzed. By comparing with the identified result of the logarithmic decrement ratio method, the validity and anti-noise was confirmed. The numerical result shows that the proposed method can accurately estimate structural modal frequencies and damping ratios. Compared with the logarithmic decrement ratio method, the wavelet transforms method is more steadied and anti-noised. The addressed method was used in an experimental study on cable structure fixed with shock absorber, and the structural modal frequencies and damping ratios were well identified.


Wang C.,China Zhongtie Major Bridge Engineering Group | Wang C.,Huazhong University of Science and Technology | Zhong J.-W.,China Zhongtie Major Bridge Engineering Group | Zhu H.-P.,Huazhong University of Science and Technology
Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of Technology | Year: 2012

This paper presented a method of fatigue assessment of steel box girder based on measured stress of health monitoring system. First, the day stress spectrum was acquired through statistically analyzing the measured stress time-history data based rain-flow counting method, and then the standard day stress spectrum can be obtained by statistical average analysis of a by multiple day stress spectrum. Based on linear cumulative damage criterion and fatigue strength curves of all kinds of detail category of steel box girder, its fatigue assessment is analyzed, and the result is updated with the change of transport condition. The proposed method is used to one bridge. And the result shows that the fatigue damage will occur at connection part between U-rib and diaphragm, so it is necessary to strengthen maintenance in the place.


Wang C.,Huazhong University of Science and Technology | Wang C.,China Zhongtie Major Bridge Engineering Group | Zhu H.,Huazhong University of Science and Technology
Proceedings of the 12th International Symposium on Structural Engineering, ISSE 2012 | Year: 2012

A wavelet-based method is proposed for identifying and locating the free spans damage of submarine pipeline structures. The method uses the continuous wavelet transform of structure dynamic response to estimate the energy density functions over the time-scale domain. Then the energy density spectrum distribution is computed. A damage index based on the variance of the relative changes of normalized instantaneous energy density (NIEV) is proposed and a statistical pattern classification method is used to identify and locate the free span damage of the pipeline. A numerical simulation is performed to validate the proposed method. The anti-noise performance of the method is investigated by adding random Gauss white noise with zero mean. The numerical result shows that free spans of submarine pipeline can be accurately detected by the proposed method even when the signals are contaminated with 10% Gauss white noise. The proposed method can be used for damage detection of submarine pipelines with nonlinear and non-stationary response of the structure.

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