Study On The Pouring Sequence Of Long-span Concrete-filled Steel Tube Arch Rib And The Hydration Heat Of Concrete In The Tube

With the construction of long-span concrete-filled steel tube arch bridge,more and more attention has been paid to the pouring process of concrete-filled steel tube arch rib as a key stage in the construction.The stress,displacement and stability of arch rib and completed bridge are affected by different pouring sequence.With the increase of span,the universality of pouring sequence needs to be further explored;with the increase of pipe diameter,the hydration heat of concrete in the pipe is also highlighted.Therefore,according to the actual project,this paper discusses the pouring sequence of concretefilled steel tube arch rib and the hydration heat in the process of concrete pouring:(1)Taking the Zhao Longba River Bridge as the project background,based on the finite element software MIDAS Civil uses the double element method to simulate the concrete pouring process of arch rib,and discusses 8 typical concrete pouring sequences.The research shows that in this project,the pouring sequence can be evaluated by referring to the stress state of arch foot section and displacement state of arch crown section.The pouring sequence of pouring the lower chord first and then the upper chord is more reasonable,and the sequential pouring order of the inner and outer sides has little impact.The accuracy of the simulation of the double unit model is verified by comparing some of the actual construction monitoring values with the theoretical values.In the early stage,the influence of different grouting sequence on the different states of arch rib can be ignored in the stage of bridge completion.Generally speaking,for the project of Zhao Longba River Bridge,different concrete pouring sequence has little influence on the alignment and stress state.(2)In order to discuss the universality of the pouring sequence of concrete-filled steel tube arch ribs,the 300 m and 500 m concrete-filled steel tube arch ribs are established according to the modification of the actual project.In the long-span concrete-filled steel tube arch ribs,four pouring sequences are proposed without considering the difference brought by the pouring sequence of the inner and outer sides.According to these four pouring sequences,the stress,displacement and stability states are divided through analysis,it is found that the difference of stress value between arch foot and arch crown is consistent with the stress value of arch foot section,and considering the three evaluation indexes,the pouring order of pouring the lower chord first is the best,which can be used in the pouring order of concrete-filled steel tube arch rib with similar four limb truss.(3)Based on the hydration heat analysis of the concrete pouring process of the concrete-filled steel tube arch rib by Midas FEA software,aiming at the project of Zhao Longba River Bridge,the radial temperature of the concrete in the pipe is mainly analyzed and compared,and it is found that the core temperature of the concrete is the highest,and the temperature field presents the distribution law from inside to outside,from high to low.In view of this phenomenon,the sensitivity of concrete core temperature to ambient temperature,wall thickness and pipe diameter under the action of hydration heat and the sensitivity of radial measuring points to ambient temperature,wall thickness and pipe diameter are analyzed.The improvement measures to reduce the hydration heat of concrete-filled steel tube are put forward.In this paper,the pouring sequence of concrete-filled steel tubular arch ribs with different forms and spans and the heat of hydration in the process of concrete-filled steel tubular arch ribs are discussed,which provides a reference for the actual construction project of concrete-filled steel tubular arch ribs in the future and has certain theoretical and practical significance.