Construction technology of large span multi arch a

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Construction technology of high pier, long-span, multiple arch and large tonnage hoisting box arch bridge

arch bridge is a bridge structure type widely used and has a long history on the highway in China. It has a magnificent appearance and is durable. In recent years, many bridge types have been built, such as girder bridges, cable-stayed bridges, suspension bridges, etc., but China has not been able to provide a large amount of steel to build highway bridges for a long time, while reinforced concrete arch bridges do not need high-strength steel, have large span capacity and low cost, which is in line with the current actual situation of China, especially in places with oil splashing or dust in mountainous areas The place with falling steam or corrosive gas shall be set outside the house, and the local highway subject to direct sunlight for a long time is still the first choice for designers

the xieyangxi bridge of Changfu Expressway on national highway 319 is a four span, five segment hoisting box arch bridge, designed by the highway planning, survey and Design Institute of Sichuan Provincial Department of communications and constructed by the Fifth Engineering Co., Ltd. of China Railway Erju. The bridge was started on November 30th, 1997, lasted three years, and was completed on October 30th, 2000

2 project profile

xieyangxi bridge is located at k115+473 of Chongqing Yufu expressway of national highway 319, where the line crosses xieyangxi and shuanghexi with a longitudinal slope of 2.7%. As the ground cross slope is large, the left and right lines are designed as two independent bridges. The left line bridge is arranged as 4 × 16mpc hollow slab + 4 × 132M reinforced concrete box slab arch + 2 × 16mpc hollow slab, 671.62m long; The right line bridge is arranged as 2 × 16mpc hollow slab + 4 × 132M reinforced concrete box slab arch + 2 × 16mpc hollow slab, with a total bridge length of 637.6m. Considering the beauty and construction convenience, the main pier and abutment are set at the same plane position

the arch ring of the main bridge is a constant section catenary non hinged arch, and the main arch is inclined. L0=132m, the force value of the load cell decreases sharply f0/l0=1/5, m=1.756, and the reserved camber is 12cm (distributed according to the thrust influence line). The left and right line arch rings are formed by prefabrication and assembly of five 1.5m wide arch boxes. The arch ring is 7.5m wide, the box is 2.2m high, the top and bottom plates are 0.2m thick, the middle ribs are 0.4m thick, the side ribs are 0.25m thick, the common diaphragm is 0.1M thick, and the diaphragm at the buckle point is 0.13M thick

double column bent pier and large cantilever bent cap are used on the arch; The column on the pier (abutment) is a double column hollow column with a wall thickness of 0.25m and an overall dimension of 2.5m × 1.5m, which can be used as pier buckle during arch box hoisting

the bridge deck on the arch is a 9.928mpc simply supported hollow slab, the bridge deck is continuous, and an expansion joint is set on the column of each pier (abutment)

it is strictly forbidden to cut off the power supply directly at the lower 5 of the main bridge 7; 4 8\abutment and 5pier adopt open cut enlarged foundation, and 67pier adopts bearing platform pile foundation

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the approach bridge is designed as a column pier, the abutment is a gravity U-shaped abutment, and the foundation is an open cut expanded foundation

design load of the bridge: Automobile - super grade 20, Trailer - grade 120; Net width of bridge deck: net -2 × 11m (carriageway) + 1.5m (median) + 2 × 0.5m (guardrail)

the characteristics of the bridge are: large span (net span 132M), long multi arch (4-span multi arch, large hoisting cable span, design hoisting cable middle span 655m), low pier and column stiffness (pier height and hollow thin-walled structure, the highest pier body is 64M (6pier)), large wind speed at the bridge site (design wind speed 27.9m/s), large hoisting weight (maximum hoisting weight up to 70t) The design requirements strictly control the structural stress and deformation indexes during the construction process. The bridge is an important and difficult project on Changfu expressway. Chongqing Transportation Bureau and Chongqing Expressway Construction Headquarters attach great importance to it. They have been to the site for many times to guide their work and have been used as a key scientific and technological project in Chongqing. Therefore, the construction of "high efficiency, high quality and safety" is of great significance

3 construction scheme design

the key and difficult point of the bridge construction is cable hoisting construction. According to the terrain, terrain and engineering characteristics of the bridge, combined with the construction technology level, machines and equipment of the unit, the overall construction scheme and control points of the project are determined as follows: ① the foundation is constructed by conventional methods, and the construction control of mass bearing platform concrete is emphasized; ② The hollow thin-walled high pier adopts the construction method of "construction of hollow high pier with steel pipe climbing frame and inverted formwork" developed by the unit in the construction of many hollow thin-walled high piers, with emphasis on model design; ③ The main arch box is constructed by cable hoisting, focusing on the design of cable hoisting system and hoisting process. The main pier can only bear the thrust of single arch box according to the design requirements, and the construction technology of double base box closure is adopted; ④ The bent on the pier (arch) shall be hoisted by cable, and the bent size and hoisting connection mode shall be paid attention to; ⑤ The bridge deck shall be prefabricated and hoisted, with emphasis on the quality of prefabricated components

4 construction method

4.1 foundation construction

the bridge foundation includes open cut enlarged foundation and dug pile foundation, and the construction adopts conventional methods. During excavation, first measure and set out, and recheck the ground elevation. During the construction of open cut foundation, the construction sequence shall be determined according to the base elevation of the left and right lines. Blasting shall be prohibited when excavating to the base to avoid damage to the integrity of the foundation, and the rock mass loosened by blasting shall be removed thoroughly. During the construction of dug pile foundation, the hole shall be excavated by jumping. During the construction, the hole opening shall be provided with retaining wall, the reinforcement cage shall be bound on site, and the concrete shall be poured after the pile foundation is inspected and accepted. After the pile foundation is completed, the bottom of the bearing platform foundation shall be inspected, the reinforcement shall be bound and the concrete shall be poured. The cushion cap concrete is a mass concrete. The key point of construction control is to reduce the hydration heat and prevent concrete cracking. The construction method is to add some fly ash to reduce the cement consumption, add high-efficiency and retarding water reducing agents to delay the high peak of hydration heat, set two layers of circulating water pipes to help dissipate heat, and water curing to control the internal and external temperature difference

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