Study On Damage Identification Of Arch Bridge

Arch Bridge is very popular to engineers in our country. It is the main bridge style for long-span bridge and the application is also further expanded. However, as the natural aging, the increase of vehicle load, lack of maintenance and repair, bridge structure will inevitably face a variety of structural damage, and these factors threat the bridge safety in serve life. Therefore, how to find an effective, rapid real-time monitoring method to identify the state of bridge damage is very necessary. The structural health monitoring (SHM) system is becoming one of the most effective techniques for ensuring the health and safety of long-span bridge and damage identification is a key technology in SHM. It has become a hot issue of civil engineering field in recent years.In this thesis, we take concrete-filled steel tube arch bridge as the main object of study, and focus on on damage identification method of the arch structure and cable tension identification of the suspender. A new damage identification method based on Generalized Strain Energy Density (GSED) is proposed for the arch structure. This dissertation analyze the change of GSED under different damage states. Then a judgment index of short cable is also proposed to develop a more simplified internal force identification method of the suspender. The main research contents of this dissertation are described as follow: Firstly, current methods of bridge damage identification are discussed and the background and development trend in this field are surveyed.Secondly, the methods of damage identification which are based on displacement mode and strain mode are also summarized. The relationship between displacement mode and strain mode is analyzed. The relationship between radial displacement in the mid plane and tangent strain in the exterior plane of circular arch is also driven.Thirdly, the concept of GSED based on the idea of strain mode is used in damage identification method of the arch structure for the first time. The GSED can identify damage existence as well as damage location, even damage level with sufficient data. The circular arches with different damage locations and degree are simulated by using ANSYS code. The natural frequencies, displacement mode, curvature mode, strain mode and GSED are obtained. The GSED is better than the methods of displacement mode and strain mode in bridges damage identification.Finally, considering the stiffness'influence and simply supported boundary condition based on vibration method, a judgment index of short cable is also proposed to develop a more simplified cable tension identification method of the suspender. Through the practical application, this method can reduce the error of traditional methods.