Research On Construction Monitoring Technology For The Demolition Of Prestressed Concrete Continuous Beam Bridge By Hanging Basket Method

With the progress of society and the increase in traffic demand,some bridges built many years ago can no longer meet the current traffic demand and need to be demolished and rebuilt.However,due to long-term operation,coupled with the impact of concrete shrinkage and creep,its own diseases and construction problems during the early bridge construction,the structural state of the bridge itself will be quite different from the design drawings,and the demolition cannot rely solely on the construction at that time.Drawings for construction.At this time,it is necessary to adopt the means of construction monitoring and refer to the site conditions to monitor and control the overall safety of the structure.Based on the main bridge demolition of the Longxi Port Bridge in the second bid section of the Hangzhou-Nanjing Expressway Reconstruction and Expansion Project,this paper studies the demolition construction monitoring technology of the prestressed concrete continuous box girder bridge.On this basis,combined with the finite element software,the bridge The whole,the hanging basket and the lower support are used for the simulation calculation of each dismantling process to ensure the safety of the dismantling of the Longxi Port Bridge.The main research contents are as follows:(1)By consulting domestic and foreign technical literature on old bridge demolition and construction monitoring,understand the current cutting-edge technology of old bridge demolition and construction monitoring,and analyze and summarize the causes of accidents that occurred in the past demolition process and other technical problems in this field;(2)Establish a spatial finite element model including beam body,hanging basket and supporting system,and conduct simulation analysis of the whole process of demolition construction.Based on the results of the simulation analysis,a construction monitoring plan is formulated,and the monitoring content,method,frequency and detailed early warning indicators are clarified;(3)During the demolition construction process,according to the proposed monitoring plan,monitor the stress and deformation of the key section indicators.When the monitoring indicators reach the warning limit,immediately stop the construction,investigate the reasons,improve the construction plan,and ensure the bridge demolition construction Safe and smooth progress;(4)Research on the prediction method of the bridge deflection state in the process of bridge dismantling,and propose a feasible prediction method.On the basis of the traditional grey theory model,the optimization comparison and selection,combined with the Markov residual correction model,are applied to the construction process control to optimize the construction control.