Research On Cracking Mechanism Of Prestressed Rigid Frame Continuous Beam Bridge Based On Structural Health Monitoring

In the past ten years,it is the golden period of rapid development of road and bridge,and the level of bridge construction has been greatly improved.Prestressed concrete continuous box girder bridge stands out in many bridge types by virtue of its advantages such as span,adaptability,reasonable structure,rapid construction,high stress intensity and so on.However,with the increase of service time,all kinds of diseases will appear.In recent years,it has been found that many long-span concrete continuous box girder bridges appear,the deflection in the middle of the span is too large,the box cracks increase rapidly,and the cracks are common.The frequent occurrence of disease makes the bridge no longer safe in service,which will reduce the safe operation time and service life of the bridge,so it is urgent for us to study the law of crack propagation.In this paper,taking Dongying Yellow River Bridge as an example,the finite element analysis software is used to establish the model of the whole bridge,and the most typical disease cracks of the long-span prestressed box girder bridge are studied in detail.The longitudinal and vertical prestress and temperature effects of box girder,as well as the influence of concrete shrinkage and creep on the main tensile stress are analyzed.The main cause of Web inclined crack,which is one of the most common crack types in prestressed box girder,is analyzed.In this paper,the middle section of the Yellow River Bridge,which has the most cracks in the box girder,is selected as the key analysis object.The finite element software ABAQUS is used to build the solid model of the middle span of the main bridge,and the detailed stress distribution characteristics of the typical diseased beam segments are studied in detail.The local crack propagation law is discussed in detail,which proves that the formation of crack and its propagation law are closely related to the over stress,boundary condition,loading law and reinforcement distribution.At the same time,the strain,temperature and vehicle load information of nearly half a year are collected by using the built bridge health monitoring system.Combined with the actual survey of the bridge cracks,the paper uses MATLAB to analyze the health monitoring data of the bridge,and obtains the relationship between the bridge temperature,strain and the crack propagation law.Finally,we focus on the analysis of the relationship between the most typical diseases(excessive deflection)of concrete rigid frame continuous bridge and the cracking of box girder.In this paper,the influence of longitudinal prestressed tendons in different positions such as top plate,web plate and bottom plate of box girder and concrete shrinkage and creep in different years on midspan deflection is studied in detail.At the same time,the factors affecting the longterm functional degradation of the bridge are analyzed systematically,and the strengthening measures are given.