Research On Damage Identification Of The Steel Truss Arch Best On Wavelet Analysis

Due to the design, construction and operating environment, civil engineering structures should always have some degree of damage or destroy. For instance, along with environmental corrosion, vehicle traffic raise, collision from the ships beneath as well as the initial defects of construction, many bridges are facing increasing functional degradation. Even concrete bridge which has a good durability also has a reduction for the endurance. Therefore,it is necessary to detect healthy state of the structure in the period of its serving or after its load condition changing so that the structural local damage,which may induce sudden destruction,is avoided in time.Once structure has been injured, the functionality of such structure will be changed accordingly. For example, the changes with the performance of material, geometrical properties, internal structure will cause decreases of structure stiffness and increases of damping. With the reduction of natural frequency stiffness and transformation of modal shape structure, the corresponding of the structure can also be changed. In this paper we will regard changes of modal parameters and structural response as a mark of structural damage. If we know the relations among modal parameters, structural response changes and structural damages in advance, thus we can use the changes of modal parameters before and after structural damage as a reflection of structural damage characteristics. In this paper, structural response which have transformed by wavelet packet establish damage index of the structure, then damage detection.Wavelet analysis is a new mathematical analysis and signals processing tool which has an outstanding contribution to the structural damage identification and health monitoring. It can effectively extracting damage characteristic, accurately positioning damage cracks by detailed analysis to time-frequency of the unsteady signal. This paper is focusing on extraction of damage characteristic, identification and positioning of damage cracks, quantitative damage analysis, by wavelet packet analysis, including a noise interference test. The test result indicates that wavelet packet change not only can detect the right position of damage but also work under mild noise interference. Wavelet packet energy feature can detect the degree of damage in a comparatively accurate way.Main content as follows:â‘ Simulating the response of steel arch bridges in impack load, measure the displacement and acceleration response before and after the damage. Using wavelet packet transform response before and after damage, injury compared before and after wavelet packet energy changes in the frequency band. Finally, through optimizing wavelet function and wavelet packet transformation level to identify the extreme of energy changes, that is to say the possible position of damage.â‘¡Verify the practicability of above method under noisy conditions by adding white noise into analog signals. The implement of signal de-noise is based on wavelet decomposition and reconstruction.Based on wavelet signal de-noise method ,the application of damage detection is researched.â‘¢Through the previous step, we can roughly detect the position of structure damage. Since measurement errors and noise may cause mis-judgment, this step, we need to pick out some points which have big energy changes, adopting wavelet analysis for further positioning and calculating the energy gradient for degree of structural damage.