Study On Cantilever Construction Technology Of Long-span Box Concrete Arch Bridge

With the continuous development of bridge construction technology in China,bridge construction technology has been in a higher level in the world,in the span,technical difficulties and other aspects of a new record.There are not many cases of cantilever casting method with cable-stayed buckle applied to box arch bridge in China.The cantilever construction method of reinforced concrete arch bridge can be divided into cantilever assembling method and cantilever casting method.The cantilever casting method mainly uses the hanging basket cantilever casting construction,according to the domestic and foreign present craft technology may divide into the tower inclined pulling buckle casting method and the cantilever truss casting method.There are not many cases of box-type Arch Bridges in China where Tower cable-stayed buckle cantilever casting method is used.Baishagou Bridge,which was built in 2007,is a reinforced concrete box-type arch bridge with a clear span of 150 m In 2012,the main span of Mupeng Bridge in Guizhou Province was 165 m box arch bridge,cable-stayed buckle hanging basket cantilever construction technology;in 2014,the main span of Tongren River Bridge in Guizhou Province was 180 m box arch bridge using hanging basket cantilever casting construction technology;In 2015,the new Midi Bridge in Panzhihua,Sichuan Province(main span is 189.9 m)was built.The bridge is a deck-type reinforced concrete box-type open-spandrel arch bridge.The construction technology of the bridge is cable-stayed buckle hanging basket cantilever Completed in 2018,the Fuling Arch Bridge is a 220 m box type concrete arch bridge with cable stayed buckle hanging basket cantilever construction technology.Up to now,the main span of 220 m box type concrete arch bridge of Chongqing Fuling Arch Bridge Double Track Bridge,which was completed in 2018,is the largest in the construction technology of cable stayed hanging basket cantilever casting in China.Although the arch ring has good integrity and the construction organization difficulty has been reduced,but because of the long cantilever section,the construction process of the arch bridge is complicated,the alignment is difficult to control,the construction risk is big,at the same time,the anchoring system has higher requirements,the structure span is limited to a certain extent,the technical difficulty increases greatly,in order to ensure structural safety and further develop the advantages of such techniques in bridge construction technology,and to meet the needs of larger span,it is necessary to further study and explore the construction technology of long-span cantilever cast box arch bridge,at the same time,it is of great significance to reduce the difference of the technology level between China and foreign countries.In this paper,the construction technology of long-span reinforced concrete box arch bridge with cable-stayed buckle cantilever is studied.The main contents and results are as follows:(1)the structural design and Construction Technology of the large-tonnage steel-concrete Pylon with cable-stayed buckle and cantilever casting method is an important part of the construction technology of the cable-stayed buckle-hanging method,at the same time,the tower must bear the light cable hoisting system and the hoisting load.Through the complex stress analysis,the tower and the anchor box system are selected.The selection of the tower is to use the inherent pier column,reduce the tower erection height,reduce the difficulty of construction.(2)the key problem in the design and construction of the large-tonnage cable system is that the tension of the single cable is larger,and it is more convenient to use the rock anchor according to the concrete conditions.The single-strand tensile force of the back cable is larger than that of the single-strand tensile force.Considering that the tension between the cable and the back cable is changing constantly during the cantilever construction,the reliability problem of the Anchorage under low stress is solved.The anchor box design of the pylon needs to be adapted to many angles because of the different tension angles of the buckle and back cable.(3)study on the construction of Section 0 # and hanging basket cantilever of curved box arch bridge with large slope,especially considering the convenience of construction.If the wedge-shaped support platform is poured twice,the minimum rigidity requirement of the first pouring should be fully considered to avoid cracking at the root of section 0 #.(4)the cantilever casting technology of the arch bridge with large slope is different from that of the ordinary continuous beam,which needs to consider climbing slope and stopping back,the structural design of the hanging basket is closely related to the convenience of construction,and the dynamic adjustment of the linear monitoring process,the process control is more difficult.(5)two-stage closure solution of long-span cantilever casting box arch bridge and safety analysis and control of structural stability.At present,the maximum span of this kind of technology is far less than that of foreign countries.Considering the safety of the structure,a stable arch state should be formed as soon as possible.Based on this,large span design can consider cantilever casting to a certain stage,the use of stiff skeleton early closure,and then continue to use hanging basket cantilever casting,to solve the safety of the hanging system,therefore,the safety of this kind of bridge will be developed to a larger span.