Box girder wet joint construction and system conversion method

Abstract

The box girder wet joint construction and system conversion method of the application processes the pier top wet joint and the bridge deck wet joint steel bars in the prefabrication yard, and the steel bar binding and model installation are carried out on the customized safety platform of the bridge deck hanging basket and the bent cap hanging basket operation platform, i.e. the sea area region; the pier top wet joint of one unit is poured at one time, the concrete is centrally mixed by the prefabrication yard mixing station, and the tank truck transportation directly pours the concrete on the bridge through the vertical lifting platform; after the wet joint concrete reaches the design strength, the closing restraint longitudinal and transverse prestress tensioning construction is carried out, and the vacuum auxiliary pressure grouting is carried out; finally, the temporary support in one unit is removed, the box girder is converted to the formal support, the simple support is changed into the continuous structure, and the system conversion is completed; compared with the traditional construction method, the method is more simple and safe, the labor intensity is reduced, the construction period is shortened, and the bridge construction speed is accelerated; the integrity is good, the structural rigidity is large, the deformation is small, the anti-seismic performance is good, and the subsequent maintenance cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of box girder wet joint, in particular to a box girder wet joint construction and system conversion method. BACKGROUND

[0002] Box girder is a kind of girder in bridge engineering, which is hollow inside, has flanges on both sides of the upper part, and is similar to a box, so it is named. It is divided into single box, multi-box and the like.

[0003] The box girder of reinforced concrete structure is divided into precast box girder and cast-in-place box girder. The box girder precast in an independent site can be erected after the completion of the lower part of the project, which can accelerate the progress of the project and save the construction period. The cast-in-place box girder is mostly used for large continuous bridges. Commonly, there are two kinds according to the materials, one is prestressed reinforced concrete box girder, and the other is steel box girder. Among them, the prestressed reinforced concrete box girder is constructed on site, and in addition to longitudinal prestress, some are also provided with transverse prestress; the steel box girder is generally processed in a factory and then transported to the site for installation, which has a full steel structure or a part of reinforced concrete pavement layer.

[0004] Among them, the steel box girder, also known as steel plate box girder, is a common structure form for large-span bridges. It is generally used in bridges with large span. It looks like a box, so it is called steel box girder.

[0005] The steel plate box girder is a common structure form in engineering. In order to study the influence of the spacing of transverse diaphragms on the distortion of simply supported steel box girders under concentrated loads, simply supported steel box girders with different numbers of transverse diaphragms are set up, the distortion effect and rigid torsion effect under concentrated loads are compared, and the curve of the maximum distortion effect with the number of transverse diaphragms is obtained. The concentrated load is applied at the top of the web of the box girder, and the load decomposition method is used to calculate under four working conditions of distortion, rigid torsion, symmetric bending and eccentric load.

[0006] From Duoduo Luo Bridge to Sutong Bridge, from Hangzhou Bay Sea-Crossing Bridge to Xihoumen Bridge, steel box girders have been more and more widely used;

[0007] Wet joint refers to the precast of prestressed concrete girder, the cantilever assembly into large-span continuous girder, and the joint of the girder blocks into a whole by cast-in-place concrete;

[0008] At present, the box girder wet joint construction method of the prior art has the defects of long construction period and complex operation.

[0009] Therefore, the skilled in the art is committed to developing a box girder wet joint construction and system conversion method, which can be poured once for wet joint construction, shorten the construction period, and reduce the idle work, so as to solve the above problems of the prior art. SUMMARY

[0010] In view of the above defects of the prior art, the technical problem to be solved by the present application is the defects of long construction period and complex operation of the existing public box girder wet joint construction method.

[0011] To achieve the above object, the present application provides a box girder wet joint construction and system conversion method,

[0012] Specifically includes the following steps:

[0013] Step 1, the erection of the inner box girder of a unit is completed;

[0014] Step 2, the working platform on both sides of the pier top is installed;

[0015] Step 3, the hanging basket on both sides of the pier top is installed;

[0016] Step 4, the reinforcement binding of the wet joint on the pier top and the wet joint on the bridge deck is carried out on the bridge deck hanging basket and the cap beam hanging basket working platform;

[0017] Step 5, the model installation of the wet joint on the pier top and the wet joint on the bridge deck is carried out on the bridge deck hanging basket and the cap beam hanging basket working platform;

[0018] Step 6, the one-time pouring of the concrete of the wet joint on the pier top and the wet joint on the bridge deck is completed;

[0019] Step 7, when the concrete reaches 90% of the design strength and the elastic modulus reaches 90% of the design value, the longitudinal closing steel beam tensioning is carried out;

[0020] Step 8, the bridge deck transverse steel beam tensioning is carried out;

[0021] Step 9, the grouting is carried out;

[0022] Step 10, the temporary support is removed, the box girder is converted to the formal support, the simple support is changed into the continuous structure, and the system conversion is completed;

[0023] Further, in the step 4, the reinforcement binding includes the binding preparation and the binding threading before the reinforcement binding;

[0024] Further, in the step 4, the wet joint and the wet joint reinforcement are centrally processed in the prefabrication field before the reinforcement binding;

[0025] Further, in the step 6, the form removal and the concrete curing are included after the concrete pouring;

[0026] Further, in the step 6, the concrete is centrally mixed by the prefabrication field mixing station, and the tank truck transportation directly pours the concrete on the bridge through the vertical lifting platform;

[0027] Further, in the step 9, the grouting includes the construction by using the intelligent vacuum grouting equipment;

[0028] Further, in the step 9, the pressure grouting is completed within 48 hours after the prestress tension of the box girder is completed.

[0029] Further, in the step 9, the pressure grouting specifically comprises the following steps:

[0030] Step 9-1, device setting and console setting;

[0031] Step 9-2, pipeline connection and cycle mode determination;

[0032] Step 9-3, slurry configuration;

[0033] Step 9-4, device debugging;

[0034] Step 9-5, pressure grouting construction;

[0035] Step 9-6, completion of pressure grouting operation;

[0036] Further, in the step 9, the pressure grouting is completed within 48 hours after the prestress tension of the box girder is completed.

[0037] With the above scheme, the box girder wet joint construction and system conversion method disclosed by the application has the following advantages:

[0038] (1) The box girder wet joint construction and system conversion method has only one-time pouring, is more convenient to operate, is safer in operation process, better plays the industrialized prefabrication production characteristics, reduces labor intensity, shortens construction period, and speeds up the bridge construction speed.

[0039] (2) The box girder wet joint construction and system conversion method converts a simple support into a continuous system, is more uniform and reasonable in stress of each part than an ordinary simple support beam, has good integrity, large structural rigidity, small deformation, good anti-seismic performance, and reduces subsequent maintenance cost.

[0040] (3) The box girder wet joint construction and system conversion method is not affected by the box girder prefabrication, box girder erection and wet joint construction through system conversion, reasonably constructs, reduces idle work, and simultaneously reduces construction period.

[0041] (4) The box girder wet joint construction and system conversion method uses a special construction platform during the wet joint construction and simple support to continuous conversion, can realize walking on the beam and is not affected by the pier, provides convenience for sea area construction, and simultaneously reduces construction and operation difficulty.

[0042] In summary, the box girder wet joint construction and system conversion method disclosed in this invention is simpler and safer than traditional construction methods. It better leverages the characteristics of industrialized prefabrication, reduces labor intensity, shortens the construction period, and accelerates bridge construction. The conversion from a simply supported to a continuous system results in more uniform and rational stress distribution across all parts compared to a simple supported beam, with better overall integrity, higher structural stiffness, smaller deformation, and better seismic performance, reducing subsequent maintenance costs. The system conversion ensures that box girder prefabrication, box girder erection, and wet joint construction do not interfere with each other. The system conversion also rationalizes construction, reduces downtime, and the use of a dedicated construction platform during wet joint construction and the conversion from simply supported to continuous systems allows for movement on the beam without being affected by bridge piers, facilitating construction in marine areas while reducing construction and operational difficulties.

[0043] The following will further explain the concept, specific technical solution and technical effects of the present invention in conjunction with specific embodiments, so as to fully understand the purpose, features and effects of the present invention. Attached Figure Description

[0044] Figure 1 This is a flowchart of a method for constructing and converting wet joints in box girders according to the present invention;

[0045] Figure 2 This is a schematic diagram of the formwork construction in Embodiment 1 of the present invention, which describes a method for constructing wet joints of box girders and converting systems.

[0046] Figure 3 This is a schematic diagram of the bottom formwork installation in Embodiment 1 of the present invention, which describes a method for constructing and converting wet joints in box girders.

[0047] Figure 4 This is a schematic diagram of the inner formwork installation in Embodiment 1 of the present invention, which describes a method for constructing and converting wet joints in box girders.

[0048] Figure 5 This is an elevation view of the outer formwork of the wet joint of a box girder, which is an embodiment 1 of the present invention of a method for construction and system conversion of wet joints of box girders.

[0049] Figure 6 This is a schematic diagram of steel strand threading in Embodiment 1 of the present invention, which describes a method for constructing and converting wet joints in box girders.

[0050] Figure 7 This is a schematic diagram of the intelligent tensioning system in Embodiment 1 of the present invention, which describes a method for constructing and converting wet joints in box girders.

[0051] Figure 8 This is a schematic diagram showing the tensioning process data of Embodiment 1 of the present invention, which is a method for constructing and converting wet joints of box girders.

[0052] Figure 9is the grouting process flow chart of embodiment 1 of the box girder wet joint construction and system conversion method of the present application;

[0053] Figure 10 is the channel grouting slurry flow schematic diagram of embodiment 1 of the box girder wet joint construction and system conversion method of the present application;

[0054] Figure 11 is the pier top moving platform schematic diagram of embodiment 1 of the box girder wet joint construction and system conversion method of the present application;

[0055] Figure 10 In the figure, (a) is the channel grouting slurry flow schematic diagram when starting grouting; (b) is the channel grouting slurry flow schematic diagram when the slurry flows from the lowest place to both sides; (c) is the channel grouting slurry flow schematic diagram when the slurry approaches full pipe; (d) is the channel grouting slurry flow schematic diagram when the slurry surface is flat with the grouting nozzle; (e) is the channel grouting slurry flow schematic diagram when circulating and dynamically holding pressure; the direction indicated by the arrow is the air flow direction; the left end air is discharged from the steel wire gap; the right end air is discharged from the slurry outlet; DETAILED DESCRIPTION

[0056] The following describes a plurality of preferred embodiments of the present application, so that the technical content is clearer and easier to understand. The present application can be embodied in many different forms of embodiments, which are described by way of example, and the protection scope of the present application is not limited to the embodiments mentioned in the text.

[0057] Embodiment 1, wet joint construction is carried out by using the box girder wet joint construction and system conversion method of the present application

[0058] Before construction, it includes construction preparation, specifically including measurement and line laying, chiseling and cleaning of concrete joint parts, timely correction of large position deviation of reserved steel bars;

[0059] Step 1, the box girder erection in one unit is completed;

[0060] Step 2, the working platform on both sides of the pier top is installed;

[0061] Step 3, the hanging basket on both sides of the pier top is installed;

[0062] Step 4, the pier top wet joint and bridge wet joint steel bar binding is carried out on the bridge surface hanging basket and bent cap hanging basket working platform; the steel bar binding before the steel bar binding includes binding, binding; the steel bar binding before the steel bar binding includes wet joint, wet joint steel bar concentrated processing in the prefabrication yard, specifically including that the oil stains, paint stains and loose skin, rust and the like on the surface of the steel bar which can be peeled off by hammering shall be cleaned up, the steel bar with granular or sheet old rust shall not be used, the shape and size must meet the design requirements, and the steel bar processing size shall meet the provisions of Table 1;

[0063] Table 1 Steel bar processing allowable deviation

[0064] Serial number Inspection item Allowable deviation (mm) 1 Full length of force-receiving steel bar after processing along the length direction ±10 2 Dimensions of each part of bent steel bar ±20 3 Dimensions of each part of stirrup and spiral steel bar ±5

[0065] Steel field installation using lap welding, lap welding length requirements as shown in Table 2,

[0066] Table 2

[0067] Welding form Welding length (mm) Double-sided welding ≥5d Single-sided welding ≥10d

[0068] Step 5, the wet joint at the top of the pier and the wet joint model installation on the bridge deck hanging basket and bent cap hanging basket operation platform;

[0069] Step 6, the wet joint at the top of the pier and the wet joint model installation on the bridge deck hanging basket and bent cap hanging basket operation platform; The concrete pouring of the wet joint is completed at one time; The concrete pouring includes form removal and concrete curing after the concrete pouring; The concrete is centrally mixed by a precast yard mixing station, and is directly poured into the bridge by tank truck transportation through a vertical lifting platform; The wet joint concrete adopts C50 marine concrete;

[0070] Step 7, when the concrete reaches 90% of the design strength and the elastic modulus reaches 90% of the design value, longitudinal closing steel beam tensioning is performed;

[0071] Step 8, bridge deck transverse steel beam tensioning;

[0072] Step 9, vacuum-assisted pressure grouting;

[0073] Step 9-1, equipment setting and console setting;

[0074] Step 9-2, pipeline connection and determination of circulation mode;

[0075] Step 9-3, slurry configuration;

[0076] Step 9-4, equipment debugging;

[0077] Step 9-5, pressure grouting construction;

[0078] Step 9-6, completion of pressure grouting operation;

[0079] Step 10, removal of temporary supports, conversion of the box girder to the formal supports, change from simple support to continuous structure, and completion of system conversion;

[0080] In the step 4, before the steel bar binding, it is checked whether the reserved corrugated pipe at the beam end is damaged, if damaged, it is treated first, the corrugated pipe of the wet joint at the top of the pier is connected, and then the steel bar binding is performed;

[0081] In the step 5, the wet joint model installation at the top of the pier and the bridge deck includes longitudinal wet joint template and wet joint template installation at the top of the pier;

[0082] As Figure 2As shown, the longitudinal wet joint template includes longitudinal wet joints between the widened box girder and the main line box girder (including the main line turning area, the widened beam and the longitudinal wet joint of the widened beam); for the wet joint of the widened section flange, the widened box girder and its corresponding main line box girder are poured after the system conversion is completed; the wet joint of the widened section flange directly uses the flange plate of the box girder as the side form, and two end head plates are additionally erected at both ends as end forms, and the bottom form uses bamboo plywood; the bottom form uses a hanging form support mode, and the bottom form is hung on the cross beam laid on the bridge surface by a pull rod; the surface of the form is brushed with machine oil as a release agent, a round steel is used as a pull rod, the form is hung every 1m, the pull rod is sleeved with a PVC hard plastic pipe to facilitate the removal of the form; the gap between the form and the beam body is blocked in advance by double-sided adhesive plugs to prevent slurry leakage; before the wet joint is constructed, the contact surface needs to be chiseled and washed clean; the concrete is supplied by a bridge concrete tank truck;

[0083] The pier top wet joint template includes bottom form installation, inner form installation and outer side form installation.

[0084] The bottom form installation includes that the form surface plate uses bamboo plywood, and the back rib uses square wood and channel steel. First, the double-spliced 10# channel steel of the bottom form is installed in place, and fine sand is installed at an appropriate position under the channel steel; then 60×80mm square wood is placed on the channel steel at an interval of 60cm and fixed, and then the bamboo plywood form is placed on the square wood; for the lower groove area of the pier top, a jacking support + support + small steel plate is used, and the area requires firm support while ensuring convenient removal in the later period. After the bottom form is installed, the bottom form is required to be closely attached to the bottom of the box girder; the form arrangement is shown in Figure 3 ;

[0085] The inner form installation includes that the transverse partition wall uses a steel form, the surface plate is 4mm, and the back rib uses 60mm flat steel + pull rod; the form arrangement is shown in Figure 4 ;

[0086] The outer side form installation includes that the standard section outer side form uses a split small steel form, the surface plate is 6mm, the outer form is provided with channel steel stiffening ribs and vertical channel steel back ribs, the channel steel back ribs and the outer side angle steel are welded into a truss structure to ensure that the steel form has sufficient rigidity and prevents form deformation; the inner steel form is provided with through holes, the steel form surface plate is tightly attached to the outer surface of the box girder by a pull rod, and double-sided adhesive tape is adhered to the position where the form is attached to the beam body periphery to prevent slurry leakage on the side; the small curve radius steel form cannot meet the construction requirements, bamboo plywood is used, the back rib uses square wood and steel pipe + pull rod at an interval of 60cm; the bamboo plywood is prohibited from being used after 6 times of turnover; when the outer form is removed, it is removed from top to bottom, the pull rod at the wing plate and web is removed respectively, and the outer form surface plate is separated from the concrete surface by block removal; the form on both sides of the box girder is placed on a safe platform, and the form is pushed forward to slide to the next wet joint for installation; the form arrangement is shown in Figure 5 ;

[0087] In step 6, the concrete pouring sequence for the wet joint is as follows: bottom web chamfer, bottom slab, web, and top slab. When pouring the bottom slab, because of the reinforcing steel mesh at the support location, a hole is made in the inner formwork for the concrete worker to enter the steel reinforcement cage for vibration. When pouring the web, the two webs are poured symmetrically. When pouring the top slab, pour from the middle of the top slab towards the web. The flange slab concrete is poured from the outside towards the web. Throughout the pouring process, the concrete is poured evenly and vibrated promptly. Concrete vibration is performed until the concrete surface no longer settles, no air bubbles overflow, and the surface begins to show a slurry sheen. Simultaneously, the old concrete surface is inspected and treated. The surface concrete within the area to be poured at the beam end is inspected; it should be roughened evenly to expose fresh aggregate and washed clean with high-pressure water. The surface is moistened during concrete pouring (ensuring no standing water) to ensure good bonding between the new and old concrete.

[0088] After the concrete is poured, it is cured. Mobile water storage tanks are installed on the bridge deck and in the box girder, and soft water pipes are laid along the bridge for the curing of wet joints and bridge deck railings.

[0089] Step 7 includes the centralized construction of steel strand fabrication within the prestressed concrete plant; the steel strands are then threaded together as follows: Figure 6 As shown, before threading the steel strands, debris in the ducts should be removed, and the steel strands threaded into the ducts should be neat and straight. After the steel strands are threaded into the beam, they should be tensioned as soon as possible, and the storage time should not be too long; otherwise, rust prevention measures should be taken. After the prestressing tendons are installed in the ducts, the openings at the ends of the ducts should be sealed. The steel strand bundles should be threaded strictly according to the construction drawings and tensioning stages, and the elongation at both ends of the steel strands should be basically the same. Each steel strand should be threaded through the anchor hole in a straight direction, so that the anchor is close to the support plate. The wedges should be tied with rubber rings, so that the wedges slide along the steel strands into the anchor holes. The limiting plate and extension sleeve should be installed, and the steel strands should be threaded into the hydraulic jack, so that the hydraulic jack, limiting plate, anchor, and extension sleeve are as close as possible and aligned. The tool anchor and wedges should be installed behind the hydraulic jack. Apply oil to the tool anchor hole or wax to the clamp; then use a steel pipe with an inner diameter slightly larger than the diameter of the steel strand to tamp and tighten the clamp to prevent slippage; adjust the top and anchor into a straight line using the chain hoist on the jack, and keep it as consistent as possible with the center line of the channel to achieve "three concentricities"; before threading the strand, press the steel strand according to... Figure 6 Number the strands and ensure the surface is clean before proceeding with the strand threading work; when the prestressing tendon consists of multiple strands, prestressing steel of equal strength should be used within the same bundle. During bundling, each strand should be straightened and securely tied to prevent tangling; the tied strands should form a rigid whole.

[0090] In step 8, the longitudinal prestressed tendons are tensioned using an intelligent tensioning method;

[0091] Tensioning sequence: The principle of tensioning the closure prestressed tendons is: first the middle pier, then the side piers; first the bottom slab, then the top slab; first the long tendons, then the short tendons; and tension in a balanced and symmetrical manner.

[0092] Tensioning condition: tensioning when the concrete reaches 90% of the design strength and the elastic modulus reaches 90% of the design value. The tensioning force and elongation shall be controlled simultaneously, and the stress under the anchorage shall be controlled according to the drawing. The elongation of the prestressed steel strand shall be measured after the initial tensioning force reaches 10% of the design tensioning force, and the actual elongation of the prestressed steel strand shall be the measured elongation plus the calculated elongation under the initial stress. The error between the actual elongation and the theoretical elongation shall be controlled within ± 6%. If the actual elongation exceeds the allowable error, stop tensioning and identify the cause. The number of broken wires per steel strand shall not exceed 1, and the broken wire rate at the same section shall not be greater than 1%, and the entire steel strand shall not be broken. The time requirement for initial tensioning shall be determined according to the construction of the first wet joint, the time control requirement for each tensioning shall be determined in communication with the design supervisor, and the tensioning prestress shall be controlled according to the different external temperatures;

[0093] Preparation before tensioning: the following data shall be measured before tensioning the first wet joint: anchor opening friction of the anchor, pipe friction, steel strand retraction after anchoring of the anchor, concrete strength and elastic modulus, and relaxation rate of the steel strand. If necessary, the design party shall adjust the tensioning control force;

[0094] As shown in Figure 7 , intelligent tensioning equipment is used for tensioning operation, the action line of the jack is coincident with the axis of the prestressed steel strand, and is perpendicular to the anchor pad. The tensioning procedure of the steel strand is: 0→ initial stress→ σcon (hold for 5 minutes)→ anchoring. The tensioning of all prestressed strands requires double control of elongation and tensioning force, with tensioning force control as the main control and tensioning elongation as the check. The error between the actual elongation and the design elongation shall be within ± 6%.

[0095] The data display during tensioning is shown in Figure 8 . Two-stage symmetric tensioning is adopted according to the design tensioning sequence. During tensioning construction, the tensioning rate shall be controlled at 10%-15% of the tensioning control force per minute, and the pressure shall be increased uniformly. The tensioning equipment shall be closely monitored to control the synchronization during tensioning construction (synchronization of symmetric tensioning of steel strands, synchronization during tensioning, and synchronization of tensioning stop points). Markings shall be made on the surface of the steel strand to check whether there is wire slipping after tensioning. The steel strand shall be anchored after the tensioning control prestress reaches stability. During or after anchoring, the anchor shall not be struck or vibrated. After anchoring, the top surface of the clamping piece of the clamping piece type anchor shall be flush, the misalignment between the clamping pieces shall be controlled within 2 mm, and the length exposed outside the anchor shall not be greater than 4 mm. After anchoring is completed and passes the inspection, the excess steel strand at the end shall be cut off, the cutting shall be performed by a grinding wheel saw or a toothless saw, and the anchor shall not be damaged. The exposed length of the steel strand after cutting shall not be less than 30 mm, and shall not be less than 1.5 times the diameter of the steel strand.

[0096] The vacuum grouting of step 9 should be completed within 48 hours after tensioning, otherwise measures should be taken to ensure that the steel strand does not rust; the process flow is shown in Figure 9 ;

[0097] The step 9 grouting includes preparation work: after the steel strand bundle tensioning is completed, recheck to confirm that there is no wire slip and broken wire; use a grinding wheel to cut the steel strand, the length of the anchor head left outside the steel beam (steel bar) is not less than 3 cm, and not more than 5 cm; remove the floating grout and sundries on the anchor pad, check whether the anchor pad and bolt hole are blocked and sundries, and use a tap to clean the hole if there is a blockage;

[0098] The step 9 grouting material: after the optimal grouting mixing ratio is adopted, the intelligent mixing system is used for mixing. The grout body must not bleed water, and the grout body performance should meet the requirements of prestressed hole grouting slurry performance index table, which is shown in table 3:

[0099] Table 3 prestressed hole grouting slurry performance index table

[0100]

[0101]

[0102] The vacuum grouting process includes:

[0103] Step 9-5-1, check the performance of the construction machine, and seal the anchor of the prestressed end; clean the prestressed pipe to meet the grouting requirements;

[0104] Step 9-5-2, connect the sealing valve at the outlet and inlet of the grouting material. Connect the vacuum pump to the non-grouting end and the grouting pump to the grouting end. Connect the negative pressure container, three-way valve and anchor cap in series, wherein the anchor cap and the valve are connected by a transparent throat pipe;

[0105] Step 9-5-3, close all exhaust valves (except those connected to the vacuum pump) before grouting and start the vacuum pump for 10 minutes. After the pressure gauge shows the generation of vacuum negative pressure and reaches-0.08Mpa and is stable, grouting can be carried out. If the above data cannot be met, it means that the corrugated pipe is not completely sealed, which needs to be further checked and corrected before continuing;

[0106] Step 9-5-4, while connecting and sealing the pipe, the grouting material is mixed: the mixing of the grouting material must be strictly controlled according to the mixing ratio requirements to ensure that the grouting material meets the strength requirements and other indicators meet the construction requirements (including workability, fluidity and expansion rate requirements);

[0107] Step 9-5-5, while the vacuum pump is running, start to inject the grout into the grouting pipe. During this process, the vacuum pressure will decrease, and the grout filling in the corrugated pipe should be observed closely through the transparent throat. If the corrugated pipe is filled, continue until the grout reaches the three-way valve installed above the negative pressure container;

[0108] Step 9-5-6, operate the valve to isolate the vacuum pump and the grout, and guide the grout to the direction of the waste grout tank. Continue grouting until the overflowing grout forms a smooth and consistent flow without irregular swings, indicating that the pipe is fully grouted;

[0109] Step 9-5-7, turn off the vacuum pump and close the valve installed at the grout outlet of the vacuum pump side pipe;

[0110] Step 9-5-8, install the small cover on the grout cap exhaust hole, and continue grouting for half a minute while maintaining the pressure at 0.4 Mpa;

[0111] Step 9-5-9, close the valve installed at the grout outlet of the grouting pump, and turn off the grouting pump;

[0112] Step 9-5-10, during the grouting process, prepare the grout test piece as required;

[0113] The grout flow diagram during grouting is shown in Figure 10 ;

[0114] After grouting, the end sealing is performed using marine C50 non-shrinkage concrete, with a strength consistent with that of the wet joint concrete.

[0115] The end sealing construction includes the following steps: before end sealing, the end concrete is chiseled, the pipeline is checked and confirmed to have no leakage, the grout on the surface of the anchor pad and the grout outside the anchor are removed, the anchor is rust-proof treated, then the reinforcement mesh is set, and the end sealing concrete is poured and troweled; the end sealing concrete should use non-shrinkage concrete with a strength not less than the design requirement. The end sealing concrete is poured and troweled, and after the initial setting of the end sealing concrete, the geotextile is covered on it for curing, and watering is performed every 2 hours. After 3 days, watering is performed every 4 hours until 7 days;

[0116] In step 10, the temporary support removal includes that after the wet joint steel hinge line tensioning and grouting are completed, the grout strength reaches 40 MPa, the temporary support can be removed, and the system conversion is performed;

[0117] After the box girder wet joint is poured, before the temporary support is unloaded, the permanent support is not yet under load, and is under load by the temporary support. Since the bottom of the permanent support is grouted and dense, and the top is poured and dense without gaps, during the unloading process of the temporary support, the bridge load is gradually transferred from the temporary support to the permanent support, but the sum of the two remains constant. Therefore, during the unloading process of the temporary support, the elevations of each point of the bridge do not change, and the structure remains in a stable state.

[0118] To ensure that the temporary support during the process of falling, beam body uneven deformation is less than 4mm; arrange special person to measure monitoring with the pier top beam bottom surface falling amount. When the same pier top support position of the beam bottom falling height difference is greater than 2mm, immediately stop the faster side of the temporary support unloading, continue to unload the slower side of the temporary support. When the falling amount of both sides is consistent, continue to start the temporary support unloading work of the same pier top, until the temporary support top surface and the beam bottom are separated.

[0119] Each piece of box girder four temporary support is removed at the same time, the construction personnel from the specially designed construction channel from the box girder flange plate position to the pier top temporary platform, rotate the lower end nut of the steel sand top, so that the steel sand flows out, and the steel sand is recycled. With the flow of steel sand, the steel sand top center falls from top to bottom, and the temporary support is removed. The box girder is supported by the permanent support, and each link of 50m box girder becomes a continuous girder structure, and the system conversion is completed. The temporary support of each link of box girder is removed symmetrically from the middle beam to the side beam. Before lifting, fix the upper and lower structures of the temporary support to prevent the upper and lower structures of the temporary support from being separated during lifting, causing lifting risk. The temporary support cylinder is tied by lifting belt, and the temporary support is moved to the pier top platform by dragging system and is drawn to the side, is lifted to the bridge deck by the lifting device on the bridge, and is transported to the storage under the bridge;

[0120] The pier top moving platform is shown in Figure 11 The wet joint construction pier top adopts the moving platform on the bridge, and the moving platform mainly comprises mechanisms: power system, hydraulic system, lifting system and steel structure. It is mainly used for wet joint reinforcement binding, form erection, form removal and temporary support removal of the pier top; if an electric motor is used as power, after the wet joint of the pier top is constructed, the horizontal steel truss at the bottom of both sides slides outward, and the horizontal truss in the middle platform slides inward to shrink. The whole lifting frame is divided into three parts (left, right and middle), which are moved to the next hole respectively. The height is adjusted by the vertical hydraulic system of the trolley during the process of positioning or moving forward, so as to keep balance;

[0121] Comparative example 2: wet joint construction of box girder by using the existing technology

[0122] Step 1, preparation work;

[0123] Step 2, binding reinforcement;

[0124] Step 3, connecting corrugated pipe and passing steel beam;

[0125] Step 4, erecting formwork;

[0126] Step 5, wet joint pouring;

[0127] Step 6, maintenance;

[0128] Step 7, tensioning negative camber steel beam;

[0129] Step 8, grouting;

[0130] Step 9, pouring the remaining part of the wet joint concrete;

[0131] Step 10, removing the temporary support in a unit, and completing the system conversion;

[0132] Test example 3, comparing the construction results obtained in example 1 and comparative example 2

[0133] It can be obtained that, after the conversion in example 1, the wet joint is poured at one time, and 4 days of construction period and 10 teams are saved for each wet joint, and compared with the traditional construction method in comparative example 2, the construction period is saved for 380 days in total, and the cost is saved for 912,000 yuan in total;

[0134] In summary, compared with the traditional construction method, the technical solution is more simple, the operation process is safer, the characteristics of industrialized prefabrication production are better played, the labor intensity is reduced, the construction period is shortened, and the bridge construction speed is accelerated; compared with the ordinary simply supported beam, the conversion from the simply supported beam to the continuous system is more uniform and reasonable, the overall performance is good, the structural rigidity is large, the deformation is small, the anti-seismic performance is good, the subsequent maintenance cost is reduced, the box girder prefabrication, the box girder erection and the wet joint construction are not affected by the system conversion; the construction is rationalized through the system conversion, the idleness is reduced, the special construction platform is used in the wet joint construction and the simply supported beam conversion, the walking on the beam can be realized and is not affected by the bridge pier, the sea area construction is facilitated, and the construction and operation difficulty is reduced;

[0135] The preferred embodiments of the application are described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and changes to the embodiments of the application without creative labor based on the concept of the application. Therefore, any technical solution obtained by logical analysis, reasoning or limited test based on the existing technology by those of ordinary skill in the art according to the concept of the application should be within the protection scope determined by the claims.

Claims

1. A method for box girder wet joint construction and system conversion, characterized in that, The method comprises the following steps: Step 1, a box girder erection is completed in a line; Step 2, a working platform is installed on both sides of a pier top; Step 3, a hanging basket is installed on both sides of the pier top; Step 4, reinforcement binding of a pier top wet joint and a bridge deck wet joint is performed on a bridge deck hanging basket and a bent cap hanging basket working platform; Step 5, a model installation of the pier top wet joint and the bridge deck wet joint is performed on the bridge deck hanging basket and the bent cap hanging basket working platform; Step 6, the pier top wet joint and the bridge deck wet joint concrete are poured once, the concrete is centrally mixed by a precast yard mixing station, and a tank truck transports the concrete to directly pour the concrete on the bridge through a vertical lifting platform; Step 7, longitudinal closing steel beam tensioning is performed when the concrete reaches 90% of a design strength and an elastic modulus reaches 90% of a design value; Step 8, bridge deck transverse steel beam tensioning is performed; Step 9, grouting is performed, the grouting comprises construction by using an intelligent vacuum grouting device, and the grouting needs to be completed within 48 hours after completion of the box girder prestress tensioning; Step 10, temporary supports are removed, the box girder is converted to formal supports, and a system conversion is completed from a simple support to a continuous structure; The grouting specifically comprises the following steps: Step 9-1, device setting and console setting; Step 9-2, pipeline connection and cycle mode determination; Step 9-3, slurry configuration; Step 9-4, device debugging; Step 9-5, grouting construction; Step 9-6, completion of the grouting operation; The pier top uses a bridge moving platform, the moving platform comprises a power system, a hydraulic system, a lifting system and a steel structure, is used for reinforcement binding of a pier top wet joint, form erection, form removal and temporary support removal, uses an electric motor as power, and after the pier top wet joint construction is completed, two bottom horizontal steel trusses automatically slide outward, a middle platform horizontal truss automatically slides inward and shrinks, slides to a position not colliding with a front of a pier in a longitudinal moving direction, and the whole hanging frame is divided into three parts and automatically moves to a next hole.

2. The box girder wet joint construction and system conversion method according to claim 1, in step 4, characterized in that, before the reinforcement binding, beam preparation and beam threading are included; before the reinforcement binding, wet joint and wet joint reinforcement are centrally processed in a precast yard.

3. The box girder wet joint construction and system conversion method according to claim 1, in step 6, characterized in that, after the concrete pouring, form removal and concrete curing are included.

4. The box girder wet joint construction and system conversion method according to claim 1, in step 9, characterized in that, after the grouting, end sealing is performed.

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