Research On The Construction Method Of Hanging Basket Suspension Casting Side Span Straight Section

For large span segmental construction continuous rigid bridge across complex terrain or river,the construction of straight section of side span is the key construction process before the bridge is closed,and its construction quality affects the internal force state and alignment of the bridge.In this paper,the feasibility of using hanging baskets to cast the straight section of the side span is studied in the context of the actual project of Ful River Bridge,and the study is carried out from the perspectives of structural optimization of the hanging baskets and analysis of the influence of bridge stress and deflection.The main work includes.(1)Exploring the simple optimization measures of the hanging basket structure from the perspective of the load-bearing capacity of the hanging basket and analyzing the applicable scope of using the hanging basket to cast the straight section of the side span.Taking the Ful River Bridge as an example,the cross-sectional information of the straight section of the side span was used to calculate the load on each member of the hanging basket,and the safety of the hanging basket was checked by adding the front boom and the rear anchor point and other simple optimization measures.(2)Finite element analysis was applied to compare the stress distribution patterns of the bridge structure for the three different construction methods,namely,casting straight sections with brackets first,then hanging baskets and hanging baskets at one time,and gradually casting straight sections with hanging baskets.The results of the study showed that the stresses of the main girders and piers were basically the same for the two construction schemes of using hanging baskets to cast straight sections of side spans,and the maximum increase of compressive stress in the most unfavorable section of the main girders at the time of construction was 15% for the hanging baskets compared with the traditional scheme.(3)The structural mechanics theory was applied to analyze the influence of the bracket cast-in-place solution and the hanging basket solution on the internal force and deflection of the structure at different stages,and the obtained law was in good agreement with the finite element analysis,and the theoretical analysis verified the reliability of the finite element numerical analysis.The numerical analysis shows that although the stress and displacement deflection of the bridge structure during the counterweight period are larger for the different schemes,the influence of the different schemes on the stress and displacement of the bridge structure is controlled within 15% after the bridge is fully assembled,and the straight section of the hanging basket suspension span has better applicability.(4)To study the influence of different side span straight section construction schemes on the bridge alignment in each stage of the bridge.This paper compares the influence of different construction schemes on the deflection of the main girder from each key construction process and each stage of the completion of the bridge covariance,the results show that: the use of hanging basket casting side span straight section on the side span side of the main girder displacement deflection is larger,the side span before the closure of the cantilever end displacement and the original scheme of the maximum difference value of 5.2cm,the mid-span side of the main girder deflection by different schemes is very small,so the use of hanging basket casting side span straight section should be from the side span L/2Therefore,the adjustment of the section prearch should be considered from the side span L/2.In the context of this project,the pre-arch of the bridge construction and the pre-arch of the completed bridge are calculated and compiled separately in this paper,and summarized into the pre-arch of the whole bridge.(5)For the special situation that the construction plan of straight section of side span is temporarily changed to straight section of side span by hanging basket during the construction,this paper combines the theory of "constant load zero moment method" and adjusts the main girder alignment by optimizing the prestressing beam arrangement to achieve the purpose of smooth bridge alignment and reasonable structural stress.