Mechanical Analysis And Monitoring Of Segmental Support Cast-in-place Prestressed Concrete Continuous Box Beam

Segmental support cast-in-place prestressed concrete continuous beam bridge has been used more and more widely in bridge construction. However, some technical points during construction have not been analyzed and studied scrupulously. They are ignored, leading to the occurrence of some engineering quality and safety problems, such as cracking and linear distortion of beams, collapse of falsework system as the bearing capacity is not enough. Therefore, it is very necessary to conduct mechanical analysis and research of segmental support cast-in-place prestressed concrete continuous beam bridge to ensure construction quality and safety of falsework system.This dissertation firstly introduced the application of steel falsework in cast-in-site bridge recently, analyzed the reasons of collapse accidents of falsework at home and abroad; after that introduced the performance and erection requirements of common falsework in cast-in-site bridge. Besides, this dissertation summarized the present study at home and broad and normulization algorithm of falsework, indicated the shortage of current design and checking calulation method, proposed that it may be unsafe to use the average algorithm to determine design loads of falsework which was provided in related reference.This dissertation conducted mechanical monitoring of segmental support cast-in-place prestressed concrete continuous beam-Zhang Xiang Bridge, summarized the stress variation rules of box beam and falsework during construction, got the conlusion that it was esay to arise tension stress at the fulcrum section, the force of falsework at both ends of midspan beam will increase after tensioning the prestressed steel bar.Full bridge finite element model and three-dimensional solid model of Zhang Xiang Bridge were established by MIDAS/civil. The calculated results and monitoring data were compared, showing that the basic rules and values of them were consistent and the force of falsework at both ends of midspan beam will increased after tensioning the prestressed steel bar.Finite element model of fastener-style and bowl-buckle falsework were established by SAP2000 according to the common erection size of bridge construciton. The influence of some important factors on buckling loads of falsework was analyzed. These factors include vertical and horizontal distance, connection rigidity, horizontal strut, vertical strut, bar missing, overhang length, and step distance.The results in the dissertation give valuble reference to conduct design and erection of falsework and assure safety of segmental support cast-in-place prestressed concrete continuous beam bridge during construction.