Research On Method Of The Beam Bridge Structure Vibration Damage Identification

Identifying the damage of bridge, it is very necessary to build an accurate model ,the onlyknown bridge test data is not enough . However, while building a finite element model of thestructure, there is a little different from the state of actual structure frequently. Sometimes thedifference between creating error of initial finite element model and measured data is very large.Therefore, in order to avoid these errors, the paper use the methods of model updating based onoptimization theory for damage assessment of bridges .And it detects on damage of a simpleshort span bridge model and the service of the Luan River Bridge. This article is based onstructural dynamics theory, the use of dynamic modal testing technique, optimization theory andnumerical simulation methods.The main contents of the completion are:1. As an example of a short-span bridge model, creating initial finite element model is usedto ANSYS software . It modify the initial finite element model basing on the dynamic testingdata of undamaged the structure. So,there is a benchmark finite element model.2. The benchmark finite element model of short-span bridge is modified , the data of testingthe dynamic damaged structure as the basis.It can get the actual state of the short-spanbridge.The limited element model be revised is replace to the damaged structure. According tothe variation of parameters that it be modified before and after, to determine the bridge's damagedegree. The carrying capacity of short-span bridges is assessed with inertia, reinforcement ratioand the final moment the relationship.3. Through dynamic testing of the service of the Luan River bridge ,can obtain the dynamicresponse of the bridge's actual structure, and creat the initial finite element model. Because themeasured data of undamaged state of the bridge is unknown, so the initial finite element model isreplace to dynamic response the undamaged state of the bridge.4. To the actual dynamic response of Luan River Bridge as the basis, and the thought ofintroduction of "weak beam" element , the degradation unit of initial finite element model ismodified.Then, the damage stiffness of the bridge is assessed. Meanwhile the finite elementmodel updating technology based on optimization theory is feasible.