Study On Closure And Stability Of The Single Track Railway Continuous Rigid Frame Bridge With The High Multi-span Piers

The continuous rigid frame bridge with the high multi-span piers has been widely used in the construction of modern bridgesdue to its advantages of good structural stress performance,strong terrain adaptability,convenient construction and low maintenance cost.In the construction of this type of bridges,the closure construction is one of the most critical construction steps.Closuretop thrust,closureloading and closure sequence have different effects on the internal force of the structure and the line shape of the bridge deck;In addition,we should pay more attention to the stability in construction stage and finished stage.Therefore,it is of great practical significance to study the closure and stability of the continuous rigid frame bridge with the high multi-span piers.Aiming at the problems of closure and stability of the continuous rigid frame bridge with the high multi-span piers,we take a continuous rigid frame bridge with five-span piers on the single track railway as the engineering background.We firstly analyze the determining methods of closure top thrust,closure loading and closure sequence and study the effection the internal force and structural displacement of each main beam and main pier after construction stage and the bridge stage,even at the ten years later;Then,we respectively analyze the stability in the stage of single pier construction,the maximum cantilever construction and the operation.We also discussed the influences of different closure top thrust,closure loading and closure sequence on the structural stability;Finally,for the continuous rigid frame bridge with unequal height main pier,we analyzed the stability of different structural system in the process of construction.The specific contentsare as follows:(1)The method of determining the top thrust of the continuous rigid frame bridge and the influence of the internal force are analyzed,the influence of the top thrust results under pile foundation model and the pileless model are compared,the influence at each stage of the top thrust and displacementon the main beam and the main pier is obtained.(2)The method of determining the closing weight of continuous rigid frame bridge and the influence of internal forces analyzed,the calculation principle of three different basic weights and the calculation method of additional weight is respectively introduced,the influence of counterweight in each stage on the force and displacement of main girder and pier is obtained,and compare the effect of forced collapse on the structure under different closing errors.(3)The closure sequence of multi-span continuous rigid frame bridges is discussed and compared,and the effect of the closure sequence on the structural lines of the main girder and pier is obtained.Through the comparative analysis of conventional closing and unconventional closing,the effect of unconventional closure on structural forces and structural line types is studied.(4)The influence of multiple key technologies in the closing section on the force and line shape of the bridge structure under the most unfavorable load combination conditions in the operation stage is studied.(5)The stability of each structural system and bridge forming stage in the construction stage is analyzed,and the stability coefficient and buckling mode of each structural system under different working conditions is studied,the stability variation rule of continuous rigid frame bridge with multi-span high pier is analyzed,and some suggestions for reference are put forward.(6)The influence of the construction sequence,the closure top push construction,and the closure additional pressure construction on the structural stability is analyzed.(7)The stability of the structure system in the construction stage and the operation stage is analyzed under different height of the main piers.