| The outline of the 14th Five Year Plan of the country proposes the requirement to accelerate the construction of a modern transportation system and create a comprehensive,efficient and practical modern infrastructure system.More and more large-span bridges are being built,and the application of top pushing construction method in bridge construction is becoming more and more widespread,with advantages such as reducing the occupation of space under the bridge,prefabricating the overall top pushing of the tire frame,simultaneous construction of the main tower and upper structure,and rapid construction of unified hanging cables in the later stage.However,the adoption of new design concepts poses higher requirements for the thrust of temporary piers,numerous monitoring parameters throughout the construction process,and local forces on steel box beams and concrete bridge decks,especially for the difficulty and accuracy of phased construction control.This article is based on the main bridge of the Zhanlin Yellow River Bridge,and establishes a simulation analysis model for the entire process of bridge launching construction and suspension cable construction.Based on the innovative design of auxiliary pier sinking to eliminate negative bending moments at the pier top,methods such as assembly elevation control and accurate calculation of stress free cable length are studied.The degree of influence of shrinkage and creep of the main tower material in the stress free state control method is compared and analyzed.According to the characteristics of the bridge structure,the entire process of construction control is carried out,And through the construction monitoring visualization monitoring platform,the entire process of bridge construction is controlled.The main research work completed is as follows:(1)Through the simulation and analysis of the whole process simulation of the steel-concrete composite girder bridge constructed by walking incremental launching,the change laws of the responses of the temporary pier reaction,the local stress of the main beam,the stress of the UHPC bridge deck,etc.under each working condition are calculated,and the most unfavorable working condition and the most unfavorable section position in the process of incremental launching are determined.(2)Based on the stress free state control method,after iteration and reaching convergence conditions,the bridge alignment and cable forces are calculated,and after formal iteration,the main beam state,cable force,support reaction force,main tower spatial state,as well as the main beam stress and cable-stayed cable stress during construction are verified,respectively,to verify whether the bridge alignment and reasonable bridge stress state have been reached.(3)Relying on the actual project of this bridge,a stress-free state control method considering the effect of concrete shrinkage and creep was developed,and the idea of iterative convergence was adopted to achieve phased control and closure of the target state of the completed bridge,guiding on-site construction,and achieving good results.(4)Based on the characteristics of the bridge structure,various control indicators such as the main beam alignment,abutment reaction,and main beam stress,cable force,and main tower stress during the launching stage are monitored.A visual control platform for construction monitoring is established to identify and handle anomalies in multi-source monitoring data,ensure the safe and smooth implementation of each construction stage,and provide a good reference for similar projects. |
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