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Due to the high speed, large impact load, high accuracy requirements of ballastless track system, and long design service life of bridge (100 years), high-speed railway puts forward higher requirements for the construction accuracy, post construction settlement and mid span creep deflection of Long-span continuous rigid frame bridge
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The Shawan waterway super large bridge of Guangzhou Shenzhen Hong Kong passenger dedicated line crossing Zini River waterway and Shawan waterway is designed as (104 + 168 × 2 + 112) m and (112 + 168 × 2 + 104) m prestressed concrete continuous rigid frame bridge, with concrete strength grade of C60, and cantilever pouring method is adopted for beam construction
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Figure 1.1 elevation diagram of Shawan waterway super large bridge crossing Zini River waterway (104 + 168 × 2 + 112) m continuous rigid frame bridge I
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construction method features 1
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Pier top bracket method is adopted for construction of Block 0, which is safe and reliable
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2
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This method uses a special self-propelled hanging basket without balance weight, which has large structural design rigidity, clear force, convenient operation and good reusability
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3
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This method optimizes the construction technology of steel bar binding, concrete pouring and prestressed tension, shortens the single section construction time of cantilever cast-in-place beam to an average of 8-10 days (5 days), improves the work efficiency and speeds up the construction progress
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4
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This method makes the construction of high-grade, high-performance and durable concrete procedural and standardized
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5
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The linear and stress monitoring method of cantilever beam is advanced and the effect is good
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6
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This method has good social and economic benefits
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2、 Scope of application 1
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It is suitable for high-speed railway high pier, long-span continuous rigid frame, continuous beam cantilever pouring construction
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2
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It is suitable for cantilever pouring construction with high safety risk and tight construction period
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3、 Combining with the characteristics of high altitude, cross channel, high design standard and tight construction period, the suspended bracket is used for the construction of large volume 0 # block, and the method of tensioning steel strand is used for preloading
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Lm-300 self-propelled triangle hanging basket without balance weight is used for hanging irrigation
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In order to ensure the quality and construction alignment of the completed bridge, in the process of cantilever grouting construction, the hanging basket assembly, formwork elevation, steel bar binding, concrete pumping, pouring and curing, prestressed tension, grouting and other links are controlled
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At the same time, SAP2000, Midas and other software are used to simulate the construction process and calculate the segment pre cast value, so as to make the internal force and alignment of the completed bridge meet the requirements
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Through the quality tracking and safety control of each link in the whole construction process, the closure of Shawan Waterway Bridge was successfully completed, which ensured the construction period
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4、 Construction process and operation points (1) overall construction technology the main pier of the bridge is located in the water, and the trestle is set up from the shore to the pier as the channel
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A tower crane is set at the pier as a vertical lifting machine
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The concrete is pumped to the construction site by delivery pump
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The 0 # block is constructed by the pier top bracket method, and the concrete is poured in two times
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Triangle hanging basket is used in cantilever casting construction
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The closure sequence is middle span first and then side span
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Water tank counterweight is set on both sides of closure section
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The main truss of hanging basket is used to form well shaped hanger in closure section
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Overall construction process flow chart (2) 0 block construction process and Technology 0 block adopts pier top bracket method for construction, single triangular bracket is welded with section steel on the ground, installed with tower crane, and connected with embedded steel plate on the top of pier body
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The structure checking calculation of 0 block bracket is shown in figure 5.2-1
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Calculation drawing of bracket structure of Block 0 construction drawing of Block 0 bracket is preloaded by steel strand tension method
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Steel strand is installed from the top of bracket and connected with embedded steel strand of bearing platform
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Jack is used at the top of bracket to tension according to design load
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The preloading load of 0 # block bracket is equal to 1.1 times of the maximum load
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0 ᦇ block bracket preloading 0 ᦇ block bracket preloading applied load (3) cantilever pouring construction technology and technology the cantilever pouring beam construction process is as follows: hanging basket in place → adjusting the elevation of bottom formwork and outer formwork → binding bottom slab and web reinforcement → installing vertical prestressed reinforcement → internal formwork system sliding out in place → installing longitudinal and transverse prestressed pipes → binding top slab reinforcement → pouring concrete → curing → threading steel strand The construction process is as follows: tensioning, grouting, moving the hanging basket forward, and constructing the next section
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The average construction period of each section is 8-10 days
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1) Design and construction of hanging basket the continuous beam of this bridge is designed as a single box and single chamber, the heaviest cantilever casting segment is 286t, and the segment length is 3m-4m
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The hanging basket of large tonnage beam section generally adopts diamond or triangle special hanging basket, and lm-300 triangle hanging basket is adopted for this bridge
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(1) Hanging basket hanging basket is mainly composed of triangle main truss, front and rear transverse connection system, top crossbeam, front and rear lower crossbeam, bottom longitudinal beam, formwork system, sling anchorage system, running sliding system and tensioning platform
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After lm-300 triangle hanging basket is designed, the lower crossbeam and sling are hinged, which is conducive to adjusting the beam bottom alignment and ensuring the tight joint twice
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The self anchoring system without counterweight is adopted to reduce the weight of the hanging basket
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The weight of each hanging basket is 115t
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The design of the front inclined sling of the main truss of the hanging basket can adopt the pre tightening of the finishing steel and the jack, which greatly reduces the overall construction deflection of the hanging basket and ensures the construction safety and quality
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The inner formwork system of the hanging basket is connected with the inner sliding beam by roller, which is convenient for the sliding and drawing out of the inner formwork system
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SAP2000 modeling is used for the overall analysis of the hanging basket
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Through the calculation, the main truss structure is stable, with large stiffness and small deformation
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The maximum deflection of the hanging basket under full load is 16.7mm
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Hanging basket 3D model and deformation of the model after loading (2) hanging basket preloading hanging basket preloading is carried out on the ground
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First, three top beams are laid on the flat ground as leveling frame, and leveling is carried out with level
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Then, the main truss is assembled on the leveling frame, the two main trusses are opposite, the front support is installed at the fulcrum O, and the rear point a is anchored with 3 shoulder pole beams and 6 Φ 32 finish rolled deformed steel bars
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Two shoulder pole beams are placed at the front node B, four Φ 32 finish rolled deformed steel bars are used to connect through the shoulder pole beam, and two ycw80b-200 jacks are used to tension them step by step
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The maximum load is 1.20 times of the main truss of the hanging basket under the most unfavorable condition,
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The preloading is loaded according to the gradient of 10%, 25%, 50%, 75%, 100% and 120%
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After loading, it is observed every 6 hours
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After the stress and deflection values are stable, it is unloaded by 50%, 10% and 0%
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Before loading, strain gauges are attached to the two suspenders of ob, AC, OC and BC of the main truss respectively, and the stress values are read respectively during step loading and unloading
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Displacement meters are installed at points a, O and B respectively to measure the deflection values of main truss at each point during step loading and unloading
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Schematic diagram of preloading of hanging basket main beam preloading (3) after the construction of 0 ﹥ beam section of T-structure assembled by hanging basket is completed, first clean the top surface of beam section, level the sleeper part with 1:2 cement mortar, lift the rod to the top surface of 0 ﹥ block with tower crane, and then assemble the hanging basket symmetrically according to the following procedures: laying steel sleeper → installing track → installing front and rear supports → hoisting main truss → hoisting front upper beam → installing rear beam Sling → hoisting bottom formwork and bottom formwork → hoisting inner formwork walking beam → installing outer formwork → adjusting formwork elevation
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(4) Hanging basket movement (1) hanging basket movement process: box girder tensioning → loosening side formwork and bottom formwork → installing track → moving basket in place → installing anchor after installation → adjusting formwork → passing acceptance → next process
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When moving the hanging basket, first level the top surface of the beam section and measure the track position, lay the cushion and track, then demould, hang the bottom formwork on the walking beam of the outer formwork with the chain block, loosen the rear anchor of the main frame, and pull the front support with the chain block to move the hanging basket, the bottom formwork and the outer formwork forward to the predetermined position of the next section and re anchor them on the track
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Install the rear sling and lift the bottom formwork
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Secondly, install the outer formwork on the beam section to run the rear hanger of the beam, then remove the rear hanger on the previous beam section, move it to the reserved duct of the beam section for installation, and then remove the other one.
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