Research On Monitoring And Control Of Deflection Construction Of Bridge Piers And Columns In Mountainous Areas

This paper investigates the problem of pier deflection in mountain bridges.Firstly,the longitudinal and longitudinal deflections occurring in the bridge during the construction stage and the operational use stage after completion of the bridge are categorized,and on this basis,the verification analysis of the causes of the disease is completed using numerical methods.Secondly,the simulation analysis of the whole process of bridge pier and column deflection construction is carried out with the relying project as an example,and the cross-sections that need to be monitored during the deflection construction are determined.Finally,a reasonable construction and monitoring plan for deflection correction is proposed,the monitoring network is improved,and the reasonableness of the research results is verified through the on-site deflection correction implementation.Through the above systematic research,the thesis draws the following conclusions:(1)The factors causing bridge deflection can be divided into two kinds of factors in the construction stage and factors in the operation and use stage,among which the factors in the construction stage include unleveled upper base plate of bearing installation,unleveled lower base plate,wedge-shaped block set for the bottom of the beam,bearing out of air,limit pin not removed after bearing installation,deviation of bridge pier construction,etc.;the factors in the operation and use stage include abnormal slip of bearing,stuck bearing,temperature action,etc.(2)Combined with the example of a bridge deflection project in the southwest mountainous area,the finite element platform of MIDAS/Civil software was used to establish the bridge model,and the results of the bridge pier deflection were analyzed by comparing the ideal state of installed bearing with the state of defective bearing installation when the conventional bridge load was applied,and the force analysis of the pier top of the bridge pier when the bearing was tilted,and the cause of the bridge deflection was initially determined to be the tilted bearing installation.In addition,the influence of the beam under the action of temperature on the pier deflection after the bearing damage was analyzed,and the residual deformation of the thermal expansion and contraction of the beam will exist when the bearing is stuck and the limit pins are not removed,and the beam will crawl after a long time accumulation,resulting in the pier deflection.It is considered that the installation defect of bearing is the main cause of beam deflection,and the self-weight of bridge and temperature change are the secondary causes of pier deflection.(3)Simulation analysis of pier and column deflection and construction process was carried out,and the deflection correction construction method with the main beam providing counterforce was established.It was clarified that the deflection correction pier and counterforce pier were the main components to be monitored,and the deformation at the top of the pier and the stress at the bottom of the pier were the main indicators to be monitored.The calculation results show that: the control threshold value of corrective displacement of 5#corrective pier is 42.250 mm,and the control threshold value of tensile strain at the bottom of pier is 112.7 με.The control threshold value of corrective displacement of 7# corrective pier is22.662 mm,and the control threshold value of tensile strain at the bottom of pier is 51.4 με.The control threshold value of strain at the bottom of pier of 10# counterforce pier is 56.6 με.(4)Combined with the construction process to improve the monitoring program and monitoring system network,the monitoring results of the control section and control indicators in the correction of deflection are analyzed: the effective displacement of the left side of pier5# is 24 mm,the effective displacement of the right side is 20 mm,and the maximum tensile strain at the bottom of pier 5# in the process of correction is 26.1 με;the effective displacement of the left side of pier 7# is 15.4 mm,and the effective displacement of the right side is 15.9mm;The strain control value is 51.4 με,and the maximum tensile strain in the process of correcting the deflection of pier 7# is 32.5 με.The displacement and tensile strain of pier 5#and pier 7# do not exceed the control threshold.The results of the bridge bearing capacity test after the construction showed that the bridge was in a safe state of structural stress after the completion of the construction,and no secondary damage was caused to the bridge during the correction of deflection.