Condition Assessment Of Concrete Box Girder Bridges Based On Crack Observation And Static Testing

After many years of construction and operation,long-span prestressed concrete box girder bridges often suffer from cracking and deflection,which seriously affects the service and safety performance of the bridges structure.At present,the condition evaluation of the damaged bridges is still a difficult problem.Based on the crack observation and static testing,this paper proposes a bridge condition assessment method with the stiffness and effective prestress as the indicators.The main research contents include:(1)Based on the displacement response under static load,the identification algorithm of flexural stiffness and shear stiffness of the damaged bridge after crack is given,and the numerical examples show that the algorithm can accurately identify the stiffness damage of the structure.The influence of displacement data error from static measurement on the result of stiffness identification is discussed.Based on the derived stiffness identification algorithm,a calculation program is compiled to provide a calculation tool for the identification of the post crack stiffness of the bridge in practical engineering(2)The crack height is defined as the characteristic parameter of bending crack.Based on the assumption of plane section,the identification theory of longitudinal effective prestressing force of existing bridge is proposed according to the equilibrium equation,constitutive equation and geometric equation of section.Through the tests of simply supported beam and continuous beam,it is verified that the calculation accuracy of the algorithm is better.At the same time,the algorithm is applied to the auxiliary shipping channel bridge of Humen Bridge,and the finite element model is modified according to the identification results of longitudinal effective prestress.The calculated deflection of the modified model in the middle of span is in good agreement with the measured deflection of the real bridge.(3)The angle of crack is defined as the characteristic parameter of inclined crack,and the vertical stress composition in the bridge web and the effect of vertical prestressed reinforcement are studied.Combined with the inclined crack detection of the web of the auxiliary channel bridge of Humen Bridge,the vertical effective prestressing force is identified,which can provide reference for the evaluation of the vertical effective prestressing force of the damaged bridge...