| Arch bridges have always been an important role in the development of highway transportation in China.In recent years,the demand for high-stiffness bridges in high-speed railways in mountainous regions are eagerly surging.Arch bridges become the top priority for mountain bridges due to its higher bearing capacity,higher rigidity and lower construction cost.However,the normal service state of arch bridges are threatened with the action of long-term load and complex mountain environment.In order to promptly apperceive the healthy condition and timely evaluate the safety status of arch bridges,it is particularly urgent and significant to carry out damage identification research of arch bridges.In this paper,the time series analysis method is introduced into the study of arch bridge damage identification,based on the domestic and foreign review of damage identification methods and research of damage identification based on time series model.Based on the theoretical basis of linear time series model and nonlinear time series model,the correlation between structural vibration system and time series model is studied by theoretical derivation.The damage identification method of arch bridge based on Kalman-GARCH model is proposed.At this basis,the experiment of a damage arch bridge is carried out.Finally,the validity and feasibility of the damage identification method are verified based on the experimental data.The main research content and results are as follows:1.Aiming at the method of damage identification based on time series model,the basic theory research of linear and nonlinear time series models is carried out.Under different coordinate systems,the natural vibration equation of the circular arch and parabolic arch are established to reveal the relationship between damage and structural vibration system.The intrinsic relationship between structural vibration system and time series model is revealed by theoretical derivation.The residual ratio based on residual sequence of time series model is extracted as structural damage feature factor.This paper proposes a new method which integrates Kalman filtering and generalized autoregressive conditional heteroskedasticity(GARCH)model.2.According to the natural state of the actual arch bridge,the experiment taking into account of the coupling factors of the loading arch model and environment is carried out,by the loading method of the counterweight arch model and the method of electrochemical corrosion accelerating test of bar.Acceleration time history data at different locations are obtained by loading the arch model at different working conditions.The test results show that the stress state and stress level of the arch model under the counterweight are closer to the actual service state of the arch bridge,and the rusting method of multi-layer wrapping in the segment can better simulate the damage state of the arch bridge in the natural environment.3.Based on the model arch test data,the damage identification of arch structure based on Kalman-GARCH model is carried out.The Kalman filter is used to de-noise the raw acceleration data.After that,a linear time series model is established and the nonlinear recursive GARCH model is introduced to further improve the identification accuracy.The relationship between damage characteristic factors and actual damage degree under different working conditions is constructed,and the calculation formulas for identifying different damages based on time series model are constructed.The validity and feasibility of the identification method are verified by analysis.Compared to Kalman-AR model,the damage recognition effect reveals the superiority of the nonlinear time series model applied to the damage identification of complex structures. |
