Study On Damage Box Beam Performance Evaluation Based On Quantitative Analysis Of Detection Elements

In the recent two decades,large-span prestressed concrete box girder bridges have been widely used in large and medium-span bridges because of its good stress characteristics,mature construction techniques,and relatively low cost.However,in the operation stage,this kind of bridges have many problems such as cracking,excessive deformation,corrosion of steel bars,etc.,which seriously affect the normal and even the safety of bridges.There have been many studies on the properties of damaged box girders.However,due to the heterogeneity and time-variation of concrete,the complex mechanical properties of box sections,and complex response of long-span continuous bridges and continuous rigid bridges under non-load factors,the analysis of the damaged box girder is still very difficult,and performance evaluation method of the damaged box girder also has some defects.Therefore,the study of choosing appropriate damage parameters and evaluating the performance of damaged box girder has a great significance.In this context,this paper systematically summarizes and evaluates the research status of the performance of damaged box girder and bridge evaluation methods.Considering the defects of the research status,this paper takes the superstructure of long-span prestressed concrete box girder bridges as the research object,combined with the common diseases in the detection process,analyzes the damage parameters and evaluates the safety of the box girders.Firstly,this paper summarizes the common damage and its impact on the box girder and selects independent evaluation indicators which can reflect the damage characteristics,based on the relationship between the damages.Then it studied the effect of the selected damage parameters to the stiffness and carrying capacity at the basis of the research status quantitatively and studied the value range of each evaluation grade is determined on this basis,which is used as the basis of quantitative evaluation.Then,the performance evaluation model of box girder is established according to the analytic hierarchy process,and the initial value of each index is obtained by the expert scoring method.Constructing correlation function to calculate the correlation degree between the measured value of the damage index and damage level,and use it as the basic parameter of bridge quantitative evaluation;using the liftoff method to modify the weight,highlight the weight of the low-level index to the damage state of the upper element.The evaluation of a certain bridge proves that the evaluation method proposed in this paper has certain feasibility.In the research process of this paper,the indexes that affect the stiffness and carrying capacity of box girders are selected.The evaluation system can accurately evaluate the performance of box girders based on the detective damage parameters,and have a great significance on bridges maintenance and carrying capacity evaluation.