Research On Health Monitoring For Medium And Small Span Prestressed Concrete Bridge

Bridge structure will have certain accumulative damage caused by vehicles, wind, overloading and other natural and manufactured factors and its performance will continue to be degradation once it has been built and put into use, which will lead to security incidents, and then threat people's lives and property. Therefore, we should pay greater attention to bridges' the safety, reliability, durability and normal function in the operation period as well as focusing on building bridges. Bridge Health Monitoring technology comes in to use under such conditions. By use of bridge health monitoring technology, we can master the status of bridge structure continuously and real-timely. It can also warn the possible risk in time, which will make sure the safety of the bridge.The research on health monitoring technology focuses on large bridges in present. In fact, most of bridge accidents have occurred in the medium and small span bridges because of their huge base, therefore we should pay enough attention for the health status of these bridge. Study on theory and practice for health monitoring for small and medium span prestressed concrete continuous bridge is carried out in the paper combined with national high technology research and development plan (863 project) named'Research on large range road disaster parameter monitoring and identification and early warning system in seasonal frozen region'. The main research work is as follows:1. Study on practical health monitoring system for medium and small span prestressed concrete continuous bridgeResearch on the established criteria, methods and steps of health monitoring system for medium and small span prestressed concrete continuous bridge is carried out by taking example of an actual bridge. Parameter selection, sensor selection, determination of monitoring programs and design of data acquisition and transmission method are also discussed in this chapter.2. Study on the influence of shrinkage and creep in health monitoring dataShrinkage and creep of prestressed concrete is the basic problem of structural analysis of this kind of bridge, less estimated shrinkage and creep will directly relate to the analyze and determine the health status of the bridge, affect the normal life of the bridge and lead to premature bridge repairs.The characteristic and computational theory of shrinkage and creep of concrete shrinkage is introduced and prediction models of shrinkage and creep is compared. The influence of shrinkage and creep to bridge health monitoring data is discussed, and it is necessary to strip the creep and shrinkage data from monitoring data. The method of stripping shrinkage and creep effects of strain data in the health monitoring is described in detail by taking example of an actual bridge. An innovative design of test block for striping shrinkage strain is used to isolate load strain, shrinkage strain, and creep strain. Through the establishment of the finite element model, Chinese prediction model and the ACI predictive model were applied to predict shrinkage and creep of concrete, and the data of prediction is compared with the measured data. The calculating method of displacement of bridge caused by of creep bridges is also studied.3. Research on evaluation method for medium and small span bridge's health statusA practical method for health status evaluation is put forward for medium and small span prestressed concrete continuous bridge, which divide the process of the evaluation of bridge's health status into two stages:completion stage and operational stage. The assessment of the bearing capacity of the bridge during completion stage is by use of load test. The measured data is obtained by sensor system, which is compared with data calculating by the finite element model, and then the bearing capacity of the bridge can be analyzed. The threshold of monitoring data is set on the bridge's operational stage. Monitoring data is analyzed real timely in order to send alarm when abnormal data occurs, thus make sure the safety of the bridge.The study of the paper provides a method of the establishment of health monitoring system of medium and prestessed small concrete bridge and provide a reference for the reasonable choice of shrinkage and creep prediction models and also offers a methods of simulating shrinkage and creep effect of bridges during operational phase, provides a practical approach to assess the health status of the bridge structure. The work has strong practical value, and also has certain reference significance for the design of bridges.