Research On Static And Dynamic Load Detection Of In-service Prestressed Concrete Bridge

This thesis takes a bridge in Hohhot as the research object,and carries out the bridge inspection and load test.By comparing the testing data and finite element calculation results of the dynamic and static load test of the bridge,and combining the requirements of the bridge related specifications,the bearing capacity and working status of the prestressed concrete bridge are judged.The main contents are as follows:1.The inspection contents of bridge appearance defects and defects,the detection of concrete carbonation depth,the detection of concrete strength and the detection of steel corrosion conditions were briefly studied,and the prestressed concrete bridges were also tested.This test shows that due to the long running time,the bridge deck system,superstructure and substructure of the bridge all have certain problems and need to be rectified.2.A generalized finite element analysis software of Midas/civil 2017 was used to establish the theoretical model of the prestressed concrete bridge,and the strain and deflection values of the bridge model under the action of the highway-II design load and the test load were calculated.3.Static load tests are conducted on prestressed concrete bridges to monitor and record the values of strain and deflection deformation under load and partial load loading conditions at the control section of the bridge,and to measure the static load under various operating conditions.Values and model theoretical values are compared and analyzed.The measured values of the deflection and strain under the condition of the maximum positive moment cross section of the south span are all smaller than the theoretical values of the model,and have met the specification requirements.In the case of the maximum positive bending moment in the middle span,the measured values of the deflection are all smaller than the theoretical values of the model,but the measured values of the strain are close to or even exceed the theoretical values of the model,indicating that the actual condition of the mid-span box girder is poor.The measured values of the maximum negative moment strain at the fulcrum of the middle-piers(2# pier)are all less than the theoretical values of the model and meet the specification requirements.The ratio of the residual strain and deflection of the concrete of the floor slab at the maximum positive moment cross-section of the spanbox girder in the south is lower than the permissible value of 20%,which meets the specification requirements.The ratio of the residual strain and deflection of the box girder at the maximum positive moment section of the midspan girder box girder to the total displacement after loading,and some measuring points exceed the specified value,indicating the actual condition of the midspan girder Poor.The ratio of the residual strain and the total displacement of the concrete at the maximum negative bending moment section of the box girder of the pier(2# pier)is less than the allowable value of 20%,which meets the specification requirements.4.Perform a sports car test on the prestressed concrete bridge,monitor and record the dynamic deflection time history curve at the control section,calculate the dynamic increment of deflection and compare it with the theoretical value of the model.The measured impact coefficients of the two test sections are all higher than the value of the specified impact coefficient,because there are more cracks on the bridge surface,which makes the deck flatness worse,and the vehicle load impact on the deck is too large.