The Research Of Bridge Structure Damage Identiifcation Based On Structure Response Vector

With the large number of engineering structures being put into service, the structuraldamage accumulate with time, the issues of structural health monitoring (SHM) andevaluation in time and the measure to ensure safety of structure with damage are becomingan important project in engineering area. As one of the most important technologies of SHMand structural safety evaluation, structural damage identification researchs are of importanttheoretical significance and practical value.Lots of researchs have been carried out by scholars to develope various damage detectionmethods based on the dynamic and static response. No algorithm has yet been proposed,which can be applied universally to identify any type of structural damages, because of thecomplexity of the structure, the multiformity of the damage and the uncertainty of the servicesurrounding. With the application of the long term structural health monitoring system, it’savailable to evolute the status and the damage of the structure for different stage of the servicelife by selecting proper structure response. The relative mature methods in structural damageidentification area are classified and summarized in this thesis, a new type of damage index——Structure Response Vector (SRV) is defined, and a potention structural damageidentification theory based on SRV is proposed. Hence, the exploring research works in thefollowing have been carried out for the purpose:(1) A normalized vector is defined to characterize the states of the structure--structuralresponse vector (SRV). The elements of the vector are defined as some static and dynamicresponse of the structure to characterize the status of the structure, which make the vector besensitive to various damages.(2) Based on the definition of the structural response vector (SRV), the octonionstructural response vector (SRV) is proposed to reflect the structural status, which makes itconvenient to define the algebraic calculation rule of the SRV. Based on the octonion theory,the octonion structural response vector consists of eight elements: seven for independentstructural response and one for null, which makes it contains sufficient message of thestructural responses to characterize the status of the structure.(3) Based on the definition of the octonion structural response vector, a promisingmethod based on octonion structural response vector is proposed for the identification ofstructural damages. The octonion vector is a multiple dimension vector, and couldn’t beillustrated in Euclidian space. A reflect phase plane is defined with two important propertiesof the vector: the mode and the direction angle. An octonion structural response vector is a point in the phase plane. For a perfect structure the octonion structural response vector is apoint in the phase plane, whereas for developing damages in the structure the octonionstructural response vector manifests itself as a definite trajectory in the phase plane. Fordifferent damage locations and types, the trajectories in the phase plane are different. For aspecific structure, there are not many typical damages (type and location) exist, thetrajectories of various developing damages in the phase plane could be calculated with finiteelement analysis. Therefore, the development of damages in a structure could be investigatedby analyzing the trajectory of octonion structural response vector obtained from the data of along-term structural health monitoring or scheduled routine structural examinations. Themeasured trajectory could be compared with the analytical trajectories of various typicaldamages developing to detect the damage of the structure.(4) A2D finite element model (FEM) of a simple-supported beam with crack-likedamages of given location and depth was built to solve the SRV. The evolutions of the SRVwith damage developing are discussed. The result shows that the SRV trajectories in phaseplane are obviously different, and the feasibility to identify the structural damage basing onthe comparability of the SRV trajectories. The orientation angles of SRVs was redefined, theSRV trajectories with symmetric damages are symmetrical in the phase plane, so todistinguish symmetrical damage successfully.(5) The multi-damage of the simple-supported beam was considered and the trajectoriesof SRVs were studied according to different developing courses. The results show that SRV isa typical state quantity, there is a unique SRV which is corresponding to a specific damage,which imply that the SRV could reflect the structure status. On the other hand, there isdifferent trajectory for different developing course of damage, which illustrates that themulti-damage could be identified with the SRV based method proposed in the thesis.(6) The trajectories of SRVs in statically indeterminate structure were studied throughthe example of a rigid frame arch bridge. The effects of SRV elements on the trajectory arestudied, the principals to define the SRV element are concluded. The evolutions of the SRVtrajectory are studied for different damage developing courses with the damage located atboth vault and arch foot.