Analysis Of Construction Sequence On The Structure Of Large Segmental Cast-in-place Continuous Beams

In cast-in-place construction of long-span continuous beams with segmental bracket,the large segmental bracket cast-in-place construction method,with larger segmental length,is generally adopted.Segmental construction sequence of this construction method is often different in different projects.However,there are few comparative studies on the influence of different construction sequences on the structure.It is very necessary to carry out in-depth analysis of it.This paper is based on the above background.This paper is based on the ballastless prestressed concrete continuous beam bridge-Chaihe extra-large bridge on Beijing-Shenyang railway passenger dedicated line.Firstly,three kinds of cast-in-place construction sequences of large segments,including the construction sequence of the Chaihe extra-large bridge,are designed.The calculation and arrangement of the prestressing tendons are also carried out.Secondly,a three-dimensional model is built by using the finite element software Midas/Civil.Structural analysis of the main girders with three construction sequences in the completed bridge state and construction process are carried out,and the displacement,internal force and stress of the main girders are also compared.It is found that there is little difference between the three construction sequences in bridge completion states,but the Z-direction displacement and combined stress values of the latter two construction sequences are larger at the closure section of the middle span in the construction process.So the conclusion is that Chaihe extra-large bridge has the best effect in linear control and stress control during construction.In addition,considering that the traditional large segmental bracket cast-in-place construction uses the construction form of full-erection and full-disassembly of the bracket,which occupies more equipments and costs more.This paper also carries out mobile layout of the bracket in the construction process of three different construction sequences.The influence of mobile mounting bracket arrangements on construction period and manufacturing cost are compared and analyzed respectively.Finally,it is found that the effect of cantilever construction sequence is the best.By summarizing the results of model analysis and the effect of three kinds of mobile mounting bracket arrangements on saving construction period and manufacturing cost,we can find out cast-in-place construction sequences of large segment which can meet different construction requirements,and provide reference for the design of similar projects in the future.