| Based on the concept of bridge’s whole life, building bridge and using stage are two key periods of the whole bridge life.Knowing bridge structure state of these two periods will be of great importance in improving the service quality of bridge,ensuring the safety of bridge structure,achieving the bridge design goal,etc.In the past,the monitoring work of the building bridge and using stage were independent.The sensors used for health monitoring were usually installed after bridge had been constructed.There was no information sharing between the two.the initial state of the bridge structure was also unknow that was against the structure condition assessment.The monitoring of the building bridge and using stage are connected in turn over time.Although there are differences on service destination,they have a lot in common on monitoring content,monitoring method and technical route.Collecting all kinds of information of the two stages,we can complete tracing monitoring and master the true structure state of the bridge to forcast behavior of the structure in the future.So we can ascertain the structural damage as soon as possible and take measures to maintain in time to reduce bridge safety incident.No matter in terms of economic perspective, integrity of the monitoring information and system or the angle of information connecting,building an entire process of bridge health monitoring system(BHMS) is the most reasonable by linking up the the monitoring of the building bridge and using stage.In the engineering background of the Zhoushan Puxi Bridge,this thesis studied the structure status monitoring and assessing of long span prestressed concrete(P.C.) cable-stayed bridge.The main research contents are as following:(1)By sensitivity calculating,the impact of changing the deadweight of main girder upon the bridge structure state was analysised.It turned out that the line shape of the girder and cable forces were sensitive to the deadload of main girder.(2)Basing on the site data materials,used the model revision technology to update finite element model on the deadload of main girder and other parameters.Then applying the revised model to do the assessment analysis of internal forces,line shape and cable forces of the bridge,got the conclusion that the modified model was much closer to the real state of bridge structure.(3)Compared and analysised ideal bridge status with modified bridge status,there were big gaps between the actual completion state and the design bridge state.What’s more,the safety reserve of innerforces of the main girder and main tower reduced a lot.In the late health monitoring stage,taking the design completion state as reference state could’t reflect the real condition of the bridge any more,and were safety risks.(4)Taking the modified model as reference mechanical model,measuring point layout schemes of the health monitoring were optimized,the system of the operational observation and assessment based on construction monitoring was established, early-warning indicators like cable forces,structural stress and linetype changing of service state were set.So far,the early-warning indicators of bridge parameters were always selected in related values.Used the modified model which was more closely related to the real bridge structure to calculate the warning indicators of Puxi Bridge so that it could making comprehensive consideration for relative and absolute values of cable forces,structural stress and linetype changing.(5)Introducing the variable weight theory based on analytic hierarchy process(AHP),evaluation model of comprehensive technical condition and structural safety status was established.At last,introduced the steps and methods of structure condition evaluation of Puxi Bridge in the operation stage in detail.According to the research above,a strong reference and consulting is provided to perfect the theory of monitoring and evaluation of long span prestressed concrete(P.C.) cable-stayed bridge. |
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