Integral incremental launching construction method for multi-connected eccentric unequal-height steel box girders

Abstract

The invention provides an integral incremental launching construction method for multi-connected eccentric unequal-height steel box girders, and belongs to the technical field of incremental launching construction of steel box girders. The construction method specifically comprises the steps of temporary support erection, pushing equipment installation, D-ramp fifth joint assembly, top pushing guide beam and steel box beam unequal-height transition measure installation, D-ramp fifth joint pushing, D-ramp fourth joint assembly and D-ramp fifth joint assembly. The construction method comprises the following steps of: connecting a fourth link, integrally pushing a fifth link and the fourth link of a D ramp, removing a guide beam in sections in the pushing process, removing the fifth link and the fourth link, falling a beam of the fifth link of the D ramp, hoisting a cross beam of the fifth link of the D ramp, hoisting a cross beam of the fourth link of the D ramp, secondarily pushing the fourth link of the D ramp, and falling the beam of the fourth link of the D ramp. Overall pushing of the multi-linkage eccentric unequal-height steel box girder is achieved, deviation is avoided in the pushing process, and the construction efficiency is high.

Description

Technical Field

[0001] The invention relates to the technical field of steel box girder jacking construction, in particular to an integral jacking construction method for multi-joint eccentric and unequal-height steel box girders. Background Art

[0002] Steel bridges are increasingly being used in bridge design due to their short construction periods, minimal impact on major traffic flows, environmental friendliness, and ease of construction. However, due to site constraints and traffic flow requirements, jacking construction is often the preferred method. To maintain span requirements, the box girder cross-section is often increased at key load points, leading to the increasing prevalence of variable-section, unequal-height steel box girders. With the continuous development of urban bridge construction, bridge construction methods are becoming increasingly diverse, and jacking technology has become extremely widely used in bridge construction. However, as people's expectations for bridges increase, the need to maintain the safety of the bridge structure while also maintaining its unique alignment and material economy leads to significant changes in bridge cross-sections. Traditional jacking construction works well for bridges with minimal changes in the bottom of the girder. However, when the bottom of the bridge changes significantly, conventional jacking construction cannot meet the construction requirements. To adapt to the wider application of jacking, leveling measures are adopted to convert unequal heights into equal heights. However, existing leveling measures are complex and difficult to implement, causing numerous challenges in bridge construction.

[0003] The Hangzhou-Anhui Expressway Yuhang Interchange Reconstruction Project begins at the Yuhang Interchange exit of the Hangzhou-Anhui Expressway and connects to the existing Yuhang Interchange. The steel box girder project includes ramps A and D, with a standard cross-sectional width of 10m. The second through fifth ramps of the D ramp are steel box girders, totaling eight spans. The D ramp's steel box girder layout is (36+46+55+50)+4×30+(35+52+31)+(68+56)m.

[0004] The fifth bridge deck of the D ramp is 10m wide. The main girder utilizes a single-box, double-chamber structure with equal-height inclined webs, and a beam height of 3.2m. Each chamber is 3.0m wide, and the left and right flange cantilevers are both 2.0m wide. The girder is welded from Q355D steel plates. The top surface of the steel box girder has a 2% one-way transverse slope, which is achieved by rotating the box girder around the design elevation line. The bottom and top surfaces remain parallel, and the webs are plumb.

[0005] The fourth bridge deck of the D ramp is 10m wide. The main girder utilizes a single-box, double-chamber structure with equal-height inclined webs, and a beam height of 2.5m. Each chamber is 3.0m wide, and the left and right flange cantilevers are both 2.0m wide. The girder is welded from Q355D steel plates. The top surface of the steel box girder has a 2% one-way transverse slope, which is achieved by rotating the box girder around the design elevation line. The bottom and top surfaces remain parallel, and the webs are plumb.

[0006] The two-turn main girder bridge body standard segment is an equal-height single-box double-chamber structure (non-single-box double-chamber at the variable-width position), and cantilevers are arranged on both sides.

[0007] The D ramp No. IV joint steel box girder is divided into 4 girder segments in the transverse bridge direction and 9 girder segments in the longitudinal bridge direction, and the whole joint has 26 girder segments.

[0008] The fifth joint of the D ramp crosses Fengxin Road and an existing road with heavy traffic, cannot be closed for construction, and has a Fengxin Road subway exit on the right side of the fourth joint and a subway auxiliary structure below and on the right side of the fourth joint with low bearing capacity. Fengxin Road has heavy traffic and cannot be closed for construction. Therefore, a multi-joint eccentric unequal-height steel box girder overall incremental launching construction method needs to be designed. SUMMARY

[0009] The purpose of the present application is to provide a multi-joint eccentric unequal-height steel box girder overall incremental launching construction method to solve the technical problems mentioned in the prior art.

[0010] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0011] The multi-joint eccentric unequal-height steel box girder overall incremental launching construction method comprises the following steps: temporarily erecting a support, installing a launching device, assembling the fifth joint of the D ramp, installing unequal-height transition measures for the launching girder and the steel box girder, launching the fifth joint of the D ramp, assembling the fourth joint of the D ramp, connecting the fifth joint and the fourth joint of the D ramp, overall launching the fifth joint and the fourth joint of the D ramp, removing the connecting part of the fifth joint and the fourth joint during launching, removing the fifth joint, hoisting the cross beam of the fifth joint of the D ramp, hoisting the cross beam of the fourth joint of the D ramp, second launching of the fourth joint of the D ramp, and removing the cross beam of the fourth joint of the D ramp.

[0012] Unequal-height transition measures for the steel box girder need to be set before launching, a plurality of steel plates are welded into inverted T-shaped joists, which can ensure that the unequal-height steel box girder can be smoothly connected to the launching girder and eliminate the variable cross-section slope area of the steel girder, so that the jack can be supported on the flat floor.

[0013] Further, a launching support needs to be set before launching, the launching support comprises a support foundation and a support structure, the support foundation is a C25 concrete rectangular foundation, the width of the foundation is 4500-6000 mm, the height is 1000 mm, and the length is 7500-9000 mm, a steel mesh is arranged at a distance of 50 mm from the top, bottom and side of the foundation, and a steel plate is embedded on the top of the foundation to facilitate welding and fixation with a steel pipe.

[0014] The jacking support adopts steel pipe columns, and the columns are connected into a whole with steel pipes. The horizontal distribution beam adopts double-piece steel, and the longitudinal distribution beam adopts triple-piece steel. Walking jacks, front and rear steel piers, top caps, adjustment pads, and pads are arranged on the longitudinal distribution beam. The walking jacking equipment and pads are arranged front and back. The distribution beam evenly distributes the pressure on the pier top to the lower foundation concrete block. The pads are used for pier top elevation adjustment and beam dropping operations during the jacking process. The walking jacking device realizes the walking translation of the steel beam.

[0015] The fifth and fourth steel box girders are integrated using connecting blocks, enabling the integrated jacking of multiple steel box girders. Since the expansion joints of conventional steel box girders are relatively short, connecting and removing the two girders is difficult. This method achieves the required spacing between the expansion joints of the two steel box girders by removing the connecting blocks and then jacking the fourth girders a second time, facilitating operation and controlling the quality of the connection.

[0016] Furthermore, during the jacking construction, a walking jacking device is used. The walking jacking device includes a slide box structure, a slideway structure, a lifting jack structure, a translation jack structure, a deviation correction device structure, a hydraulic pump station system, a sub-control system and a master control system. The whole set of walking jacking equipment integrates the traditional jacking and deviation correction into one, and separates the vertical jacking. Each set of walking jacking devices is centrally controlled by a master control system.

[0017] The slide box of the walking-type jacking device is the load-bearing structure supporting the main beam. Two rubber plates or high-density wooden boards are placed on the upper part to balance the local force on the main beam. A stainless steel plate is welded to the lower part of the slide box, which constitutes a sliding surface with the polytetrafluoroethylene plate on the slide. The upper surface of the polytetrafluoroethylene plate is made into a mushroom head shape, and silicone oil is applied in between to reduce the friction resistance of the sliding surface. Two sets of correction devices with guide wheels are arranged on both sides of the slide, which can solve the guidance problem in the longitudinal direction of the bridge and the adjustment problem in the transverse direction of the bridge. The piston heads of the two lifting jacks are equipped with ball heads, which can adapt to the slope.

[0018] Furthermore, the D5 and D4 sections of the D ramp were installed by jacking. The steel box girders were lifted onto the assembly platform by a crane and assembled into a whole. After the assembly was completed, they were pushed into place by a three-dimensional jack. Before construction, temporary assembly brackets and jacking brackets were constructed. During the construction of the steel box girders, crawler cranes were used to lift and assemble individual components. The steel box girders were assembled on the temporary assembly brackets, lifted by crawler cranes, and pushed into place by a three-dimensional jack.

[0019] A total of 12 sets of assembly supports and 12 sets of jacking supports will be erected for the D4 and D5 steel box girders of the D ramp. Ten sets of crawler jacking equipment will be deployed, including 20 crawler jacking machines, 10 hydraulic pump stations, and 1 main control system.

[0020] After the steel box girder is pushed into place, it is necessary to drop the girder in order to install it to the designed elevation. Therefore, the entire construction process includes 9 stages: (1) assembling the fifth steel box girder and guide beam on the assembly bracket and the pushing bracket, (2) continuing the pushing construction of the fifth steel girder, (3) hoisting the fourth steel girder and connecting it with the fifth steel girder, (4) continuing the pushing construction of the fifth and fourth steel box girders, and removing the guide beam in sections during the process until all the steel box girders are pushed into place, (5) dismantling the fifth and fourth steel beams, installing the fifth cross beam and then switching to drop the beam, (6) installing the fourth cross beam, (7) pushing the fourth steel box girder a second time, (8) switching to drop the fourth steel box girder system, (9) removing equipment and brackets.

[0021] Furthermore, the role of the guide beam is to reduce the construction internal force of the steel box girder during the jacking process, increase the jacking span, and play a guiding role. The guide beam consists of two main beams and three cross braces. The two main beams of the guide beam are variable-section I-sections. The two main beams of the guide beam are connected by steel tube trusses. In order to make the guide beam better jacking the pier, the front end of the guide beam is made into an upturned structure. The guide beam and the steel beam are connected by full-melt welding. A single guide beam is used. When the guide beam and the steel beam are assembled and welded, the measurement and layout are accurate to ensure that the linearity of the guide beam meets the jacking linearity. To facilitate construction, the web of the guide beam is arranged in a plumb line. At the same time, to match the inclined web structure of the steel box girder, a double web transition section is set at the connection between the guide beam and the steel box girder. The guide beam is partially provided with an inclined web member + straight web. The force of the inclined web of the steel box girder is transmitted to the straight web of the guide beam through the transition section.

[0022] The guide beam is mainly composed of upper and lower flange plates, middle web plates, longitudinal stiffening ribs and vertical stiffening plates;

[0023] The welding sequence of steel guide beam and steel box beam is as follows: welding the straight web of steel guide beam to the end of steel box beam → welding the inclined web of steel guide beam to the side web of steel box beam → welding the upper flange plate of steel guide beam to the top plate of steel box beam → welding the lower flange plate of steel guide beam to the bottom plate of steel box beam → welding the stiffening plate to the top plate and web plate;

[0024] When the guide beam starts to be pushed from the first jacking platform, crosses the relevant lines, and reaches the jacking platform on the opposite side, it is necessary to prepare for the pier on the head end of the guide beam. When the guide beam cannot be smoothly put on the pier due to the downward deflection caused by its own weight, a vertical jack is set on the temporary pier to assist in the pier. When facing the pier, the jack of the facing pier is first retracted to the bottom, and the corresponding pad beam is set according to the height difference of the facing pier. Then, the steel beam is lifted up by the jack of the facing pier. After passing the walking jacking device, the slide box is returned to its original position, the load of the jack of the facing pier is unloaded and the load is transferred to the slide box. After the pier is faced, the pad is restored to the pushing state, and the walking jacking equipment of the pier is put into use.

[0025] The specific operation steps of the guide beam pier are as follows:

[0026] (1) Remove the steel pad at the front end of the jacking device to allow the front end of the guide beam to pass over the walking jacking device;

[0027] (2) Use the jack to push the front end of the guide beam upward to eliminate the deflection of the guide beam and push forward;

[0028] (3) Increase a steel pad at the front end of the walking device, vertically push back, and transfer the load of the guide beam to the steel pad at the front end;

[0029] (4) Horizontally push back the walking device, jack up the guide beam, and make the front end of the guide beam empty;

[0030] (5) Repeat (1)-(4), push the guide beam forward until the guide beam passes through the walking push box, and push the front end of the device vertically and replace the steel pad;

[0031] (6) The guide beam reaches the equipment sliding block, and the pier is completed;

[0032] When encountering a support that needs to be raised in design elevation, first make the guide beam pass through the pier and then use the jack to lift the guide beam. Place a steel pad on the fulcrum, lower the jack to make the guide beam rest on the steel pad again, lower the jack to the lowest position, and place a steel pad on the jack. Repeat this step to make the fulcrum reach the push elevation.

[0033] Further, the fifth and fourth joint of the D ramp push construction process includes the following steps:

[0034] Step 1: equipment access, construction of substructure, equipment installation and debugging;

[0035] Step 2: hoist D5-I to D5-A segment, a total of 124 meters of steel box girder, where the A section is divided into two sections, A2 segment is hoisted to the design position by crane after the push is completed, and the steel girder is hoisted after the steel girder is hoisted. After the welding is completed, prepare for pushing. Working condition analysis: use crawler crane to occupy the left and right sides of the steel beam, and hoist I→H→G→F→E→D→C→B→A beam segment→steel guide beam in turn. The main arm of the crane is 39m, the turning radius is 16m, the rated load under this working condition is 66.2t, which meets the hoisting requirements;

[0036] Step 3: push 123.940 meters in the direction of large mileage and stop pushing, adjust the bridge body line, and prepare to hoist D4-I~D4-C segment of D4 joint;

[0037] Step 4: Lift the 0.6m connecting block → lift the D4-I to D4-C segmental steel box girders. D4-G can be pushed with the crossbeam. The D4-I crossbeam is divided into sections I1 and I2, and the D4-D crossbeam is divided into sections D1 and D2. Sections I2 and D2 are not involved in the push. According to the working condition analysis, crawler cranes are used to occupy the left and right sides of the steel beam and lift the beam sections I→H→G→F→E→D→C in sequence. The maximum beam section weight G is 64.22t. A crawler crane is used to complete the lifting. The crane's main boom is 39m and the swing radius is 14m. The rated load capacity under this working condition is 78.1t, which meets the lifting requirements.

[0038] When hoisting the 4-section D4-I to D4-C segments, first install the connection block and temporarily consolidate it with the D5-A segment of the D5 segment. Then temporarily consolidate the D4-I segment of the D4 segment with the other end of the connection block. The beam segments of the other segments of the D4 segment are connected according to the designed assembly sequence. The connection block is made of steel plate with a box-shaped section. The thickness of the steel plate is the same as that of the top, web and bottom plates. The connection block is set at the connection seam between the D5 segment and the D4 segment. The jacking can be continued only after the connection block is consolidated and welded.

[0039] Step 5: After the D4-I to D4-C segments are welded, continue pushing 78.795 meters in the direction of the long mileage. After the guide beam reaches the D17# permanent pier, remove the 14m guide beam of the first segment;

[0040] Step 6: Continue jacking after adjusting the alignment; gradually remove the remaining second and third segment guide beams until the fifth steel box girder is jacked into place. After the fifth steel box girder reaches the designed position, remove the temporary connection blocks of D5 and D4, and use crawler jacks on jacking supports No. 10-12 to lower the beams. After the beams are lowered, hoist the A2 beam section of Pier D15 in situ. The beam section weighs 14.1 tons and is hoisted using a 260-ton crawler crane with a 39-meter main boom and a 14-meter slewing radius. Under this condition, the rated load capacity is 31.3 tons, which meets the hoisting requirements.

[0041] Step 7: The D4-I2 beam segment was hoisted in situ. The beam segment weighed 14.1t and was hoisted using a 260-ton crawler crane. The crane had a 39m main boom and a 14m swing radius. Under this working condition, the rated load capacity was 31.3t, meeting the hoisting requirements.

[0042] Step 8: After the I2 beam segment is installed, it is pushed forward 480mm to the designed position. A crawler jack is used on the No. 6-9 pushing brackets to lower the beam. The remaining D4-D2 segment, D4-B segment, and D4-A segment steel box beams are hoisted in situ. The hoisting order is D2 → B2 → B3 → B1 → B4 → A segment. The maximum beam segment weight is 45.7t. A 260t crawler crane is used for the hoisting. The crane has a main boom of 39m and a swing radius of 18m. The rated load capacity under this working condition is 56.8t, which meets the hoisting requirements.

[0043] Step 9: Dismantle equipment and temporary structures.

[0044] Furthermore, during jacking, it is necessary to monitor the deviation of the steel box girder, including geometric monitoring and physical monitoring. The specific process of geometric monitoring is as follows:

[0045] ① Displacement observation: Displacement observation mainly focuses on the centerline offset of the main bridge and the horizontal and vertical displacement of the jacking platform. During the jacking process, timely adjustments must be made using jacks. Observation of the jacking platform displacement is extremely important. The maximum displacement value is calculated based on the design allowable displacement. Coordinates are converted and continuous observation is conducted from the start of force application until the main beam begins to move. Once the displacement exceeds the design allowable value, force application is immediately stopped and the tension of each jack is readjusted.

[0046] ② When pushing to the end, pay special attention to whether the main beam has reached the designed position. It must be pushed to the final position at night when the temperature is stable, and the beam length must be carefully calculated and measured based on the temperature. When pushing for the last time, a small stroke should be used to facilitate deviation correction and longitudinal movement into place.

[0047] ③ In actual construction, there will be uncertainties and there may be deviations during the jacking process. Based on the feedback of linear coordinates and measurement data, the lateral deviation correction function of the walking jacking equipment is used to make timely corrections and adjustments. All walking jacks under the beam section and guide beam are lifted at the same time. The correction data of each walking jack is input on the main console, and then all jacks are started at the same time to complete the lateral deviation correction action synchronously. After verification, the jacking construction continues;

[0048] The specific process of physical monitoring is as follows:

[0049] During the jacking process, the jacking force needs to be monitored in real time. The friction force is calculated based on the fulcrum reaction force under various working conditions and verified with the oil pressure gauge. The fulcrum reaction force under each working condition is measured by the pier top monitoring element.

[0050] The magnitude of the jacking force is automatically adjusted according to the magnitude of the frictional resistance and is reflected by the oil gauge. The jack must be calibrated as required before use, and the oil gauge should be calibrated. When applying jacking force under each working condition, first gradually increase the force of the jacks on each pier to the calculated jacking force. During the jacking process, try to control the force balance of each jacking jack; the specific process is: ① Monitoring the deflection of the box girder during the jacking process, ② Monitoring the stress of the key sections of the main bridge and temporary supports and stress concentration points during the jacking process, ③ Monitoring the magnitude of the jacking force during the jacking process, ④ Monitoring the temperature during the jacking process, and ⑤ Monitoring the wind environment during the jacking process.

[0051] The present invention has the following beneficial effects due to the adoption of the above technical solution:

[0052] (1) The two-connection steel box girder is connected as a whole steel girder by a connecting system for integral jacking, and after the jacking is completed, the connecting system is removed for secondary jacking, the steel box girder is a variable cross-section height steel girder, the steel girder and the guide beam are connected by a transition tool, the local part is jacked with a cross beam, the inner side needs to be ballasted or the length of the steel girder is increased to balance the eccentric weight, the integral jacking of the multi-connection eccentric unequal height steel box girder is realized, the deviation is avoided during the jacking process, and the construction efficiency is high.

[0053] (2) After the D5 and D4 two-connection steel box girders are assembled, 16 jacking devices are synchronously jacked, and the 16 devices are synchronously pressure-regulated through a main control console; after the A1 connection steel box girder is assembled, 14 jacking devices are synchronously jacked, and the 14 devices are synchronously pressure-regulated through the main control console. The jacking pressure value of each point is adjusted according to the vertical load borne by the temporary pier, so as to reduce the horizontal force borne by the temporary pier. The computer control synchronously jacks, so as to avoid that the bridge pier bears a large concentrated load. The computer control synchronously lowers, so as to avoid that a single jacking cylinder bears eccentric load. The moving deviation is detected in real time, and the jacks are used in time for deviation correction. The horizontal displacement of the temporary pier is monitored in real time, combined with jacking pressure observation, so as to prevent the temporary pier from being damaged. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 It is a construction sequence schematic diagram of the present application;

[0055] Figure 2 It is an installation general flow chart of the present application;

[0056] Figure 3 It is a standard section size diagram of the steel box girder of the present application;

[0057] Figure 4 It is a D5 jacking support arrangement diagram of the present application;

[0058] Figure 5 It is a specific structure schematic diagram in the second jacking step of the present application;

[0059] Figure 6 It is a specific structure schematic diagram in the third jacking step of the present application;

[0060] Figure 7 It is a specific structure schematic diagram in the fourth jacking step of the present application;

[0061] Figure 8 It is a specific structure schematic diagram in the fifth jacking step of the present application;

[0062] Figure 9 It is a specific structure schematic diagram in the sixth jacking step of the present application;

[0063] Figure 10 It is a specific structure schematic diagram in the seventh jacking step of the present application;

[0064] Figure 11 It is a schematic diagram of the specific structure in the pushing step eight of the present invention. DETAILED DESCRIPTION

[0065] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and by way of preferred embodiments. However, it should be noted that many of the details listed in this specification are merely provided to help the reader gain a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be practiced even without these specific details.

[0066] This project is a reconstruction project for the Yuhang Interchange on the Hangzhou-Anhui Expressway. Starting at the Yuhang Interchange exit of the Hangzhou-Anhui Expressway, it connects directly to the existing Yuhang Interchange. The steel box girder project includes the D ramp bridge, with a standard cross-sectional width of 10m. The second through fifth ramps of the D ramp are steel box girders, totaling eight spans. The D ramp's steel box girder layout is (36+46+55+50)+4×30+(35+52+31)+(68+56)m. Based on the designed on-site construction environment, the fourth and fifth ramps of the D ramp are planned to be constructed using the jacking method, while the remaining two ramps will be constructed using hoisting.

[0067] The fifth bridge deck of the D ramp is 10m wide. The main girder utilizes a single-box, double-chamber structure with equal-height inclined webs, and a beam height of 3.2m. Each chamber is 3.0m wide, and the left and right flange cantilevers are both 2.0m wide. The girder is welded from Q355D steel plates. The top surface of the steel box girder has a 2% one-way transverse slope, which is achieved by rotating the box girder around the design elevation line. The bottom and top surfaces remain parallel, and the webs are plumb.

[0068] The fourth bridge deck of the D ramp is 10m wide. The main girder utilizes a single-box, double-chamber structure with equal-height inclined webs, and a beam height of 2.5m. Each chamber is 3.0m wide, and the left and right flange cantilevers are both 2.0m wide. The girder is welded from Q355D steel plates. The top surface of the steel box girder has a 2% one-way transverse slope, which is achieved by rotating the box girder around the design elevation line. The bottom and top surfaces remain parallel, and the webs are plumb.

[0069] The standard sections of the main beams of the two ramps are all single-box double-chamber structures with equal height inclined webs (not single-box double-chamber structures at widening points), with cantilevers set on both sides. The specific structural forms are as follows: Figure 3 shown.

[0070] The D-ramp's fourth section of steel box girders is divided into four sections in the transverse direction and nine sections in the longitudinal direction, for a total of 26 sections. The D-ramp's fifth section of steel box girders is divided into four sections in the transverse direction and nine sections in the longitudinal direction, for a total of 28 sections.

[0071] Construction Site of the D Ramp: The D ramp is being installed using a lifting and jacking method. The fifth section, spanning Fengxin Road, is planned to be installed using jacking to ensure traffic on Fengxin Road. The assembly area for the fifth section will be located between piers D8-D13. After the steel beams are assembled, they will be jacked to the bridge and lowered into place. To ensure the safety of the subway's auxiliary structures, the fourth section will also be installed using jacking. The second and third sections will be installed using 260-ton and 200-ton crawler cranes, respectively. As the FJ beam section of the second section is located directly above the subway, a 200-ton crawler crane was used to reduce local pressure.

[0072] According to the actual working conditions on site, the overall construction sequence is: erection of temporary scaffolding → installation of jacking equipment → assembly of the fifth section of D ramp → installation of jacking guide beams and unequal height transition measures for steel box beams → jacking of the fifth section of D ramp → assembly of the fourth section of D ramp → connection of the fifth and fourth sections of D ramp → jacking of the fifth and fourth sections of D ramp as a whole → dismantling of guide beams in sections during jacking → dismantling of the connection of the fifth and fourth sections → dropping of the fifth section of D ramp → hoisting of the fifth section cross beam of D ramp → hoisting of the fourth section cross beam of D ramp → secondary jacking of the fourth section of D ramp → dropping of the fourth section of D ramp

[0073] The overall installation process is as follows Figure 2 As shown, the push bracket

[0074] (1) Bracket foundation

[0075] The support foundation is a C25 concrete rectangular foundation with an expanded concrete foundation, ranging from 4500 to 6000mm in width, 1000mm in height, and 7500 to 9000mm in length. A steel mesh is installed within the foundation, 50mm from the top, bottom, and sides. An 800*800*20mm steel plate is embedded in the top surface of the foundation to facilitate welding and securing to the steel pipe.

[0076] (2) Bracket structure

[0077] Push bracket adopts Steel pipe columns, between columns The steel pipes are connected into a whole. The transverse distribution beam adopts double-piece HN700×300×13×24H steel, and the longitudinal distribution beam adopts triple-piece HN700×300×13×24H steel. The longitudinal distribution beam is arranged with a 300t walking jack, front and rear steel piers, top caps, adjustment pads, pads, etc. The walking jacking equipment and pads are arranged front and back. The distribution beam distributes the pressure on the pier top evenly to the lower foundation concrete block. The pads are used for adjusting the pier top elevation and dropping the beam during the jacking process. The walking jacking device can realize the walking translation of the steel beam. The jacking bracket layout is as shown in the figure. Figure 4Temporary piers for pushing up the fourth and fifth steel box girders of the D ramp are: DLSD-01 to DLSD-12. Brackets for assembling the fourth and fifth steel box girders of the D ramp are: DPZZJ-01 to DPZZJ-12.

[0078] Main structure of walking jacking equipment:

[0079] The walking jacking device consists of four major structures and three major systems: the sliding box structure, the slide structure, the lifting jack structure, the translation jack structure, the deviation correction device structure, the hydraulic pump station system, the sub-control system and the master control system. The entire walking jacking equipment integrates the traditional jacking and deviation correction into one, and separates the vertical jacking. Each set of walking jacking devices is centrally controlled by a master control system.

[0080] The sliding box of the walking jacking device is the load-bearing structure supporting the main beam. A 2cm rubber sheet or high-density wood board is placed on top to balance the load on the main beam. A stainless steel plate is welded to the bottom of the sliding box, forming a sliding surface with the polytetrafluoroethylene sheet on the slideway. The upper surface of the polytetrafluoroethylene sheet is shaped like a mushroom head, and silicone oil can be applied to the inside to reduce friction. Two sets of guide wheels are placed on both sides of the slideway to solve the problem of longitudinal guidance and transverse adjustment. The piston heads of the two jacking jacks are equipped with ball joints to adapt to a small range of slopes.

[0081] Equipment selection is shown in Figure 1.

[0082] Table 1 is the performance parameter table of the walking jacking equipment

[0083]

[0084] Hydraulic pump station

[0085] The hydraulic pump station is the power source for the walking jack, providing energy for the actuator jack. The hydraulic pump station uses an electric motor as its driving force, driving the plunger pump to provide pressurized oil to the system. Together with hydraulic components such as the relief valve and solenoid reversing valve, it forms a basic circuit for pressure and flow. The hydraulic power output by the pump station drives the jack, extending or retracting the jack cylinder, thereby achieving the walking jack's translation and lifting movements.

[0086] The system consists of six identical but independent circuits, each controlling a single jack. Each circuit has its own pump head port for hydraulic oil output, and independent hydraulic valves and related hydraulic components control the pressure and flow direction of the hydraulic oil. These circuits form a single path, independent of each other, simplifying the hydraulic circuit and facilitating control.

[0087] Working Principle: An electric motor drives a plunger pump to provide pressurized oil to the system. Hydraulic oil output from each port of the plunger pump passes through a check valve and then enters a solenoid reversing valve. The direction of the pressurized oil flow is controlled by switching the solenoid reversing valve's spool, thereby determining whether the jack extends or retracts. A hydraulically controlled check valve is installed between the reversing valve and the jack to maintain pressure. The maximum system pressure is set by a relief valve and displayed on a pressure gauge.

[0088] Walking push equipment control system

[0089] The control system utilizes a distributed computer network control system, consisting of a master console, several field controllers, sensors, data cables, and control lines. This project's control system is designed to utilize one master console to control five pumping stations and ten walking jacking units, along with their associated sensors. Each walking jacking unit consists of one or two vertical lifting jacks, one horizontal lifting jack, and two deflection-correcting jacks, along with corresponding displacement and pressure sensors. The master computer remotely controls each field controller, displaying the oil pressure and displacement of each jack and the distance lifted on either side of each pier. The system features data storage and fault alarms, automatically shutting down when preset travel or load limits are reached. The master console utilizes an industrial computer combined with configuration software. It remotely controls each field controller, displays the oil pressure and displacement of each jack, and allows users to set the maximum travel and pressure of each jack. The system also allows users to conveniently remotely start and stop the pumping stations, control pressure, and perform various other operations. When online, all operations are performed by the main control computer, with the field controller only performing emergency stops. When the field controller switches to "local" mode, the field wireless handles independently control each pier, while the main console monitors data from various on-site sensors. The system features data storage and fault alarms, automatically shutting down when pre-set travel or load limits are reached.

[0090] Because the software implements different levels of system management permissions, operators can select different operating modes, view trend curves and reports, etc. System engineers can modify the software according to actual conditions. Operators with permission can operate any jack and pump station individually or online in the central control room.

[0091] Synchronous control of the longitudinal horizontal thrust control system:

[0092] The longitudinal horizontal pushing control strategy is mainly displacement control with auxiliary pushing force. Displacement is monitored by displacement sensor. The longitudinal horizontal pushing of the same pier is synchronously controlled. The 1# jack is the main point and comparison reference (certain extension cylinder speed), and the 2# jack is the follower and compared with the 1# jack. When the stroke of the 2# jack is greater than that of the 1# jack (the longitudinal horizontal displacement difference is set to 3mm), the flow of the 2# jack is reduced. Conversely, the flow of the corresponding jack is increased. The longitudinal horizontal pushing displacement of the two sides of the same pier is required to be synchronized to ≤5mm.

[0093] The longitudinal horizontal pushing of different piers is synchronously controlled. The 1# jack is the main point and comparison reference, and the jacks of the other piers are compared with it. When the displacement difference of the jacks of each pier exceeds the set value (longitudinal horizontal pushing displacement 3mm), the flow of the corresponding jack is reduced or increased. The longitudinal horizontal pushing displacement of each pier is required to be synchronized to ≤5mm.

[0094] The vertical lifting control strategy is synchronous control mainly by pressure control and auxiliary by displacement control.

[0095] The vertical lifting keeps the main beam synchronized when the main beam is lifted off the cushion beam and lowered back to the cushion beam. Each lifting device has two sets of displacement sensors. One side of the same pier is taken as the reference, and the displacement sensors are installed between the slide and the cushion beam to detect the lifting height. The vertical lifting process is synchronized to within 5mm.

[0096] Four pressure transmitters are installed on each set of lifting device (two vertical lifting jacks). The computer can monitor the load change of each force point and accurately coordinate the load distribution of the entire system. The maximum pressure of each force point and the maximum pressure difference between the force points of the same pier can be set through the field controller and the main control console. When the load reaches the set value, the system will automatically stop and alarm.

[0097] The control core uses PLC to collect sensor data, perform logical operation and processing, and output control signals to realize coordinated control of the hydraulic jacks. The human-machine interaction uses industrial touch screen to monitor the actions of each jack, set control parameters and record data information in real time.

[0098] The main control console has automatic, manual and adjustment operation functions.

[0099] Working principle of walking jack:

[0100] Step one: After all the preparations are completed, the pre-lifting command is initiated from the central control room to make the sliding block of each point position jack adhere to the bottom of the steel beam web (automatically stopped by the pre-set zero pressure value).

[0101] Step 2: After the pre-jacking is completed, the jacking sensor value is cleared, and the central control room inputs a vertical jacking stroke value within the range of 0 to 130MM (this value is adjusted in real time according to the working conditions). One jacking stroke takes 10 to 15 minutes, and all the jacking machines at all points start to jack synchronously until the steel beam and the cushion beam are completely detached.

[0102] Step 3: Stop jacking after emptying, switch to the jacking knob, enter the longitudinal horizontal jacking stroke value within the range of 0 to 500MM (the value is adjusted in real time according to the working conditions), and one longitudinal horizontal jacking stroke takes 10 to 15 minutes. Start jacking at each point synchronously, and push the steel beam forward smoothly as a whole. Stop when the set jacking stroke limit is reached.

[0103] Step 4: After pushing into place, switch to the descending knob, enter a descending stroke value within the range of 0 to 130MM, and start descending at each point synchronously until the steel beam completely falls on the cushion beam and the slider of the jacking machine at each point is clear of the bottom of the steel beam.

[0104] Step 5: After the slider and the steel beam are cleared, switch to the pull-back knob, return the pushing stroke value to zero, and pull the slider back to the initial position. At this point, a complete pushing process is completed.

[0105] Main construction methods for steel box girder jacking:

[0106] There are 8 steel box girders in total, including D2~D5 of D ramp: among them, D5 and D4 of D ramp are installed by jacking.

[0107] The steel box girder was hoisted onto the assembly platform by a crane and assembled as a whole. Once assembled, it was pushed into place using a three-dimensional crawler jack. Before construction began, temporary assembly supports and jacking supports were constructed. During construction, a 260t crawler crane was used to lift and assemble individual components.

[0108] (1) Transport access road: A temporary access road will be built according to the actual situation on site to accommodate the parking of lifting machinery and the transportation of steel box girders during construction.

[0109] (2) The steel box girders were assembled on temporary assembly supports, hoisted by crawler cranes, and pushed into place by three-dimensional jacks. To reduce the on-site transportation of steel box girders, the transportation of steel box girders was based on the on-site hoisting capacity. The required beam sections were transported to the site every day. The steel box girders that arrived at the site were hoisted into place within 2 days, ensuring that the steel box girders did not need to be stored at the construction site for a long time.

[0110] The on-site jacking and installation of steel structures is a crucial step in the entire project, directly impacting the overall quality and progress of the project. Therefore, it is essential to develop and implement scientific construction methods tailored to the specific structural form, and rationally arrange the process to ensure high-quality and efficient completion of the entire project.

[0111] The plan for the jacking installation of the steel box girders of this bridge proposes to erect 12 sets of assembly brackets and 12 sets of jacking brackets for the D4 and D5 steel box girders of the D ramp; it is planned to invest 10 sets of walking jacking equipment (including 20 walking jacking machines, 10 hydraulic pump stations, and 1 main control system;

[0112] After the steel box girder is pushed into place, it is necessary to drop the girder in order to install it to the designed elevation. Therefore, the entire construction process includes four stages:

[0113] (1) Assemble the steel box beam and guide beam on the assembly bracket and the jacking bracket;

[0114] (2) Continue the jacking construction until all the steel box girders are pushed into place;

[0115] (3) System conversion and beam drop;

[0116] (4) Remove the equipment and brackets.

[0117] The pads are constructed from square steel tubes (200*200*10mm or 140*140*6mm) and a single-layer cover plate. The cover plate measures 500*500mm, with a thickness ranging from 8 to 12mm. Pad heights are available in 100mm and 500mm, and adjacent pads are connected using M18 bolts. To ensure the correct alignment of the steel box girder during the jacking process, the pad steel plate should be selected based on the pre-camber value of the steel box girder. Pads and plates already placed on the temporary piers are not included.

[0118] There are three sizes of pads: Pushing Equipment Pad 1: A 500mm high steel pier constructed with two 630*10mm diameter round steel tubes arranged side by side and top and bottom cover plates; Beam Drop Pad 2: A 500mm high pier constructed with four 200*200mm*10mm square steel tubes arranged in a square pattern and a single cover plate; Pad 3: A 100mm high steel pier constructed with four 200*200mm*10mm square steel tubes arranged in a square pattern and a single cover plate. The pad beam structure utilizes H-shaped steel H700*300*13*24 in double and triple configurations as distribution beams. Temporary steel structures are all made of Q235B.

[0119] Rubber pads: To prevent compression deformation and paint damage to the steel box girder bottom plate, protective measures are taken at the contact surface between the support points and the steel box girder. Rubber pads are placed above the support points, and transparent PVC pads are placed on top of the rubber pads. Both the rubber pads and the PVC pads are 800*500*10mm in size and can be purchased in quantities based on construction needs.

[0120] Guide beam structure: The guide beam reduces the internal construction forces of the steel box girder during the jacking process, increases the jacking span, and serves as a guide. This guide beam consists of two main beams and three cross braces. The guide beam is 33 meters long and features a variable I-shaped cross-section. The top and bottom plates are 24 to 16 mm thick, and the width of each plate tapers from 1200 mm to 600 mm. The webs are 16 to 12 mm thick and 3200 to 1250 mm high. The two main beams are connected by steel tubular trusses. To facilitate the jacking of the piers, the front end of the guide beam is designed with an upturned structure. The guide beam is made of Q235 steel and weighs approximately 46 tons. The guide beam is connected to the steel beam using full penetration welding. A single guide beam is used throughout the project. During assembly and welding, accurate measurement and layout were performed to ensure that the guide beam's linear alignment matched the jacking alignment.

[0121] The guide beam is primarily composed of upper and lower flange plates, an intermediate web, longitudinal stiffeners, and vertical stiffeners. The welding sequence for the steel guide beam and steel box beam is as follows: weld the straight web of the steel guide beam to the end of the steel box beam → weld the inclined web of the steel guide beam to the side web of the steel box beam → weld the upper flange of the steel guide beam to the top plate of the steel box beam → weld the lower flange of the steel guide beam to the bottom plate of the steel box beam → weld the stiffeners to the top plate and web (at the joint between the steel guide beam and the steel box beam).

[0122] Guide beam pier: When the guide beam starts to be pushed from the first jacking platform (DT marked platform), crosses the relevant lines, and reaches the jacking platform on the opposite side, it is necessary to prepare for the guide beam head end to be put on the pier. When the downward deflection caused by the guide beam's own weight cannot be smoothly put on the pier, the specific construction process of the pier can be assisted by setting a vertical jack on the temporary pier (similar to the pier of the previous guide beam). When meeting the pier, first retract the pier jack to the bottom, set the corresponding pad beam according to the height difference of the pier, and then use the pier jack to lift the steel beam. After passing the walking jacking device, return the slide box to its original position, unload the pier jack load and transfer the load to the slide box. After the pier is completed, restore the pad to the pushing state and put into the walking jacking equipment of the pier.

[0123] The specific operation steps for the guide beam to meet the pier are as follows: (1) Remove the steel pad at the front end of the jacking device to allow the front end of the guide beam to pass over the walking jacking device. (2) Use a 100t jack to lift the front end of the guide beam upward to eliminate the downward deflection of the guide beam and push it forward. (3) Add a steel pad at the front end of the walking device, and the 100-ton vertical jacking return stroke transfers the guide beam load to the front end steel pad. (4) The walking device performs a horizontal jacking return stroke, and the 100-ton jack lifts the guide beam to free the front end of the guide beam. (5) Repeat the above steps, pushing the guide beam forward until the guide beam passes over the walking jacking slide box, and use a 100-ton vertical jacking to lift the front end of the jacking device and replace the steel pad. (6) The guide beam reaches the device slider to complete the pier. When encountering a support that needs to increase the design elevation, first let the guide beam pass the pier top, then use a jack to lift the guide beam, place a steel pad on the fulcrum, and lower the jack so that the guide beam is re-supported on the steel pad; lower the jack to the lowest position, and place a steel pad on the jack, and repeat this step until the fulcrum reaches the jacking elevation.

[0124] After the D5 and D4 steel box girders were assembled, 16 jacking devices were simultaneously pushed forward, with pressure adjusted simultaneously by the main control console. After the A1 steel box girder was assembled, 14 jacking devices were simultaneously pushed forward, with pressure adjusted simultaneously by the main control console. The jacking pressure at each point was adjusted based on the vertical load on the temporary piers to reduce the horizontal forces acting on them. Computer-controlled synchronous jacking prevented large concentrated loads on the piers. Computer-controlled synchronous hydraulic descent prevented eccentric loading on individual jacking cylinders. Movement deviations were detected in real time, and jacks were used to correct them promptly. Real-time monitoring of the temporary pier's horizontal displacement, combined with observations of jacking pressure, prevented damage.

[0125] Temporary piers and other structures cannot bear more than 5% of the horizontal load:

[0126] Because the temporary structure cannot withstand horizontal loads exceeding 5%, we designed and manufactured a walking jacking device that converts horizontal thrust into internal forces within the device. During the jacking process, the hydraulic cylinders provide the entire device's horizontal thrust, both along and across the bridge. The resulting reaction force is equal in magnitude and opposite in direction to the friction between the upper and lower components. Computer control maintains the walking jacking device's pushing speed at no more than 3 meters per hour, ensuring a smooth jacking process and minimizing inertial loads. Previous project data indicates that inertial loads are negligible.

[0127] During construction breaks, the long length of the steel box girder structure makes it susceptible to temperature fluctuations, resulting in significant expansion and contraction due to thermal expansion and contraction. If the entire box girder falls on a temporary cushion beam, a large horizontal thrust will be exerted on the temporary structure. During extended periods of inactivity, all but the front-end fulcrum (to maintain linear stability) falls on the jacking equipment, utilizing the upper and lower sliding structures of the crawler-type jacking equipment to eliminate temperature-induced horizontal loads. The entire equipment utilizes an advanced electro-hydraulic proportional synchronous control system (see the equipment introduction section for details), which ensures synchronous movement of the steel box girder during lifting, lowering, and advancement.

[0128] Corrective measures

[0129] The walking jacking equipment integrates lifting, horizontal pushing, and lateral adjustment, enabling both horizontal and vertical adjustments. During the jacking process, the computer control system automatically corrects deviations by adjusting the travel of the longitudinal and transverse guide adjustment cylinders and the jacking support cylinders, ensuring the steel box girder centerline remains within the permitted range. During assembly and alignment, manual operation allows for fine-tuning and adjustment of various points to meet assembly precision requirements.

[0130] During the jacking of the steel box girder, surveyors use a total station to track and monitor the deviation of each pier and the position of the girder centerline. If the centerline shifts, adjustments are made promptly to ensure that the deviation of each pier top is within the design requirements. If lateral adjustment is required, the transverse correction cylinder is activated to adjust the horizontal position of the steel box girder to within the allowable range, thus achieving the correction function.

[0131] It is very important to observe the horizontal displacement of the temporary pier top. Continuous observation must be carried out from the start of force application to the beginning of movement of the beam. Once the displacement is too large or the steel box beam shows "creeping" phenomenon, it should be paused immediately and the load distribution of each jacking point should be readjusted.

[0132] During jacking construction:

[0133] (1) Before using the jacking system, the system should be debugged and rehearsed as a whole to ensure the normal operation of all cylinders, oil circuits and control systems during the jacking process.

[0134] (2) The welding of steel box girders must be carried out under conditions of stable temperature and low sunlight intensity to avoid the influence of factors such as temperature and sunlight on the deformation of the beam section and the length of the beam.

[0135] (3) The length of the steel pad beam of the jacking equipment along the bridge direction shall not be less than 1.6m, and the jacking force applied by the jacking equipment to the steel box beam must be transmitted to the web.

[0136] (4) When pushing, a special person should be assigned to check the guide beam and box beam. If the guide beam component is deformed, the screws are loose, the connection between the guide beam and the steel box beam is deformed, or the box beam is partially deformed, the pushing should be stopped immediately and analyzed and handled.

[0137] (5) Before jacking, communication should be conducted with the design, supervision and other units to determine the theoretical data such as the vertical force and horizontal jacking force at each point during the jacking process, set the allowable deviation range of force and displacement at each point, and input it into the central controller database as control parameters.

[0138] During jacking construction control:

[0139] (1) Estimate the friction force based on the fulcrum reaction force of the working condition and verify it with the oil pressure gauge.

[0140] (2) If a sudden increase in the pushing force is found during the pushing process, the pushing should be stopped immediately and the cause should be checked, especially the support frame and sliding surface on the pushing equipment.

[0141] (3) Displacement Observation: Displacement observation mainly focuses on the centerline offset of the beam and the horizontal and vertical displacement of the pier top. During the jacking process, timely adjustments need to be made using jacks. Pier top displacement observation is very important. The maximum displacement value is calculated based on the design allowable displacement. Coordinates are converted and continuous observation is made from the start of force application to the start of beam movement. Once the displacement exceeds the maximum value, force application is immediately stopped and the tension of each jack is readjusted.

[0142] (4) Applying jacking force: The magnitude of the jacking force is automatically adjusted by the main console according to the magnitude of the friction resistance, and is reflected by the oil gauge. The jack should be calibrated as required before use, and the oil gauge should be calibrated.

[0143] (5) When pushing to the last beam section, special attention should be paid to whether the beam section has reached the designed position. It must be pushed to the final position at night when the temperature is stable according to the monitoring instructions, and the beam length must be carefully calculated and measured based on the temperature.

[0144] (6) When pushing the last section of beam in each round and the last round, you should pay attention to slowing down the pushing speed so as to correct the deviation and move it longitudinally into place.

[0145] Synchronous control measures for jacking construction

[0146] (1) Synchronous jacking: 1) The jacking cylinder of each device on site is equipped with a stroke sensor to measure the jacking / lowering height of each device in real time; 2) Each device corresponds to a jacking proportional valve to adjust the hydraulic oil flow to the jacking cylinder of the device; 3) By manually adjusting the jacking system pressure of each device to 1MPa, all devices are jacked until they no longer rise, and the system remembers the initial stroke value of the current device, that is, zeroing; 4) The pressure at each point is adjusted to 3MPa greater than the calculated pressure; 5) During the automatic jacking / lowering process, the jacking stroke sensor transmits the current stroke value to the main control cabinet in real time. The main control cabinet compares the difference between the jacking / lowering stroke value of each point and point 1, and sends the voltage value of the jacking / lowering proportional valve of the device to adjust the hydraulic oil flow at the point, so as to achieve real-time adjustment of the jacking / lowering displacement of the point, realize synchronous jacking / lowering, and prepare for the next synchronous advance.

[0147] (2) Synchronous jacking: 1) The forward cylinder of each device on site is equipped with a stroke sensor to measure the forward stroke of each device in real time; 2) Each device corresponds to a forward lift proportional valve to adjust the hydraulic oil flow to the forward cylinder of the device; 3) All devices retreat to the limit position and adjust the initial value of the sensor to 10mm; 4) Adjust the pressure at each point to 3MPa greater than the calculated pressure; 5) During the automatic forward process, the stroke sensor transmits the current stroke value to the main control cabinet in real time. The main control cabinet compares the stroke value of each point with the difference between point 1 and the voltage value of the forward proportional valve of the device, adjusts the hydraulic oil flow at the point, and realizes real-time adjustment of the forward displacement of the point. The above actions are repeated to realize the overall jacking of the steel box girder to the predetermined position. The jacking speed can be achieved at a synchronous jacking speed of (2-3) meters per hour depending on the configuration of the pump station.

[0148] 7. Linear quality control: (1) Strict control of the linear shape of steel beams begins when the sections are manufactured in the factory. During the in-factory manufacturing, the steel beams are manufactured according to the design linear shape + pre-camber method to ensure the accuracy of the manufacturing linear shape. (2) The installation measurement of each section of the steel beam is comprehensively controlled by the three-dimensional coordinate position of each steel beam section, the conformity of the linear shape and the weld gap. After the temporary support is erected, the support elevation is calculated according to the design pre-camber linear shape. After measurement and verification, the tooth plate is trimmed to meet the linear shape of the bottom plate of the beam section. (3) Strengthen construction technology management and adhere to the technical briefing and measurement review system. The surveyors use high-precision total stations and levels to control the center line and elevation of the entire project. At the same time, a handover review system is adopted for each measurement process. (4) During the jacking process, the jacking speed of the steel beam and the elevation and displacement of the jacking monitoring point should be strictly tested, and any deviation should be corrected immediately. (5) When the D5 and D4 joints are pushed forward, they need to be assembled again. At this time, it is necessary to pay attention to the fact that the line shape of the D5 joint and the line shape of the D4 joint should be kept in line, and the line shape of the D4 beam section assembled later should be accurate.

[0149] The construction process of the fifth and fourth ramps of D:

[0150] Step 1: (1) Equipment is brought to the site, and three connections and one leveling are completed; (2) Substructure is constructed; (3) Equipment is installed and debugged.

[0151] Step 2: (1) Hoist the D5-I to D5-A sections, a total of 124 meters of steel box beams, of which the crossbeam at section A is divided into two sections. After the A2 section is pushed, it is hoisted to the designed position by crane. After the steel beam is hoisted, the 33-meter steel guide beam is hoisted. After the welding is completed, it is ready for pushing. Working condition analysis: A 260-ton crawler crane is used to occupy the left and right sides of the steel beam, and hoist I→H→G→F→E→D→C→B→A beam section→steel guide beam in sequence. The maximum beam section weight is 49.5t. A 260t crawler crane is used to complete the hoisting. The crane main arm is 39m and the rotation radius is 16m. The rated load capacity under this working condition is 66.2t, which meets the hoisting requirements. Figure 5 shown.

[0152] Step 3: (1) Push 123.940 meters in the direction of the long mileage and stop pushing. Adjust the bridge alignment and prepare to hoist the D4-I to D4-C segments. Figure 6 shown.

[0153] Step 4: (1) Hoist the 0.6m connecting block → hoist the D4-I to D4-C segment steel box beam, where D4-G can be pushed with the beam, where the D4-I beam is divided into I1 and I2 sections, and the D4-D beam is divided into D1 and D2 sections, and the I2 and D2 sections do not participate in the pushing; Working condition analysis: Use a 260-ton crawler crane to occupy the left and right sides of the steel beam, and hoist the I→H→G→F→E→D→C beam sections in sequence. The maximum beam section weight G is 64.22t. A 260t crawler crane is used to complete the hoisting. The crane main arm is 39m and the rotation radius is 14m. The rated load capacity under this working condition is 78.1t, which meets the hoisting requirements. Figure 7 As shown. (1) When hoisting the 4-link D4-I to D4-C segments, first install the connecting block (0.6 m) and temporarily consolidate it with the D5-A segment of the D5 link; (2) Subsequently, the D4-I segment of the D4 link is temporarily consolidated with the other end of the connecting block, and the beam sections of the other segments of the D4 link are connected according to the designed assembly sequence; (3) The connecting block (0.6 m) is made of steel plate with a box-shaped section. The thickness of the steel plate is the same as that of the top, web and bottom plates. The connecting block is set at the connection seam between the D5 link and the D4 link; (4) The jacking can only be continued after the connecting block (0.6 m) is consolidated and welded.

[0154] Step 5: (1) After the D4-I to D4-C segments are welded, continue to push 78.795 meters in the direction of the long mileage. (2) After the guide beam reaches the D17# permanent pier, remove the 14m guide beam of the first segment. Figure 8 shown.

[0155] Step 6: (1) Continue pushing after adjusting the line shape; gradually remove the remaining second and third segment guide beams until the fifth steel box beam is pushed into place. (2) After the fifth steel box beam reaches the designed position, remove the temporary connection blocks of D5 and D4, and use a walking jack on the No. 10-12 pushing bracket to carry out the beam drop construction. After the beam drop is completed, hoist the A2 beam section of Pier D15 in situ. The beam section weighs 14.1t and is hoisted using a 260-ton crawler crane. The crane main arm is 39m and the rotation radius is 14m. The rated load capacity under this working condition is 31.3t, which meets the hoisting requirements. Figure 9 shown.

[0156] Step 7: In-situ hoisting of the D4-I2 beam section, the beam section weighs 14.1t, and is hoisted using a 260-ton crawler crane. The crane's main boom is 39m, and its slewing radius is 14m. Under this working condition, the rated load capacity is 31.3t, which meets the hoisting requirements. Figure 10 shown.

[0157] Step 8:

[0158] (1) After the installation of the I2 beam segment is completed, it is pushed forward 480mm to reach the designed position, and a walking jack is used on the 6-9 pushing bracket to carry out the beam drop construction. (2) The remaining D4-D2 segment, D4-B segment, and D4-A segment steel box beams are hoisted in situ. The hoisting order is D2→B2→B3→B1→B4→A beam segment. The maximum beam segment weight is 45.7t. A 260t crawler crane is used to complete the hoisting. The crane main arm is 39m and the rotation radius is 18m. The rated load capacity under this working condition is 56.8t, which meets the hoisting requirements. The working conditions are as follows: Figure 11 shown.

[0159] Step 9: (1) Dismantle equipment and temporary structures.

[0160] Monitoring measures for steel box girder deviation

[0161] (1) Necessity of construction monitoring

[0162] The bridge deck system's jacking process involves a continuous transformation of the structural system, making alignment control particularly difficult and crucial. Due to the constant changes in the deck system's alignment during the jacking process, the stresses on the temporary supports are of particular concern.

[0163] (2) Purpose

[0164] 1) Ensure that the bridge alignment after jacking meets the design requirements;

[0165] 2) Ensure that the force on temporary supports during the jacking process does not exceed the warning range.

[0166] (3) Monitoring content

[0167] Monitoring is mainly divided into geometric monitoring and physical monitoring.

[0168] 1) Geometry monitoring

[0169] ① Displacement Observation: Displacement observation primarily focuses on the centerline offset of the main bridge and the horizontal and vertical displacement of the jacking platform. Jacks are used for timely adjustment during the jacking process. Observation of jacking platform displacement is crucial. The maximum displacement is calculated based on the design allowable displacement. Continuous observation is performed from the time force is applied until the main beam begins to move. If the displacement exceeds the design allowable value, force application is immediately stopped and the tension of each jack is readjusted.

[0170] ② When pushing to the final position, pay special attention to whether the main beam has reached the designed position. Push to the final position at night when the temperature is stable, and carefully calculate and measure the beam length based on the temperature. The last push should use a small stroke to correct the deviation and move the beam into place.

[0171] ③ There will be uncertainties in actual construction, and there may be offsets during the jacking process. According to the feedback of linear coordinates and measurement data, timely correction adjustments are made through the lateral correction function of the walking jacking equipment. All walking jacks under the beam section and guide beam are lifted at the same time, and the correction data of each walking jack is entered on the main console. Then all jacks are started at the same time to complete the lateral correction action synchronously. After verification, the jacking construction continues.

[0172] 2) Physical monitoring

[0173] During the jacking process, the jacking force needs to be monitored in real time. The friction force is calculated based on the fulcrum reaction force of various working conditions and verified with the oil pressure gauge. The fulcrum reaction force of each working condition is measured by the pier top monitoring element.

[0174] The thrust is automatically adjusted based on the amount of frictional resistance and is reflected by the oil gauge. The jacks must be calibrated as required before use, and the oil gauge should be calibrated. When applying the thrust under each working condition, gradually increase the force on each pier to the calculated thrust. During the thrusting process, try to ensure that the force applied to each jack is balanced.

[0175] The main physical monitoring of jacking construction includes the following: ① Monitoring of the deflection of the box girder during the jacking process; ② Monitoring of the stress of the key sections of the main bridge and temporary supports and stress concentration points during the jacking process; ③ Monitoring of the jacking force during the jacking process; ④ Monitoring of temperature during the jacking process; ⑤ Monitoring of the wind environment during the jacking process.

[0176] Steel box girder drop construction: (1) Preparation before drop: Lift the beam as a whole and calculate the reaction force of each support point through the oil pressure of each jacking machine. Under this premise, uniformly measure the elevation of each support point and arrange the height measurement scale to visually judge the synchronization error of each support point. 1) Check the jacking machine and oil pressure system to ensure that they are intact and reliable. Prepare the beam drop piers in place. 2) Verify whether the communication command system is intact, unify the communication signals, unify the operating instructions and practice them. 3) Hold an on-site briefing meeting to clarify the command system, beam drop steps and plans, the responsibilities and operating instructions of each position such as the person in charge of each pier, the operator of each pump station, the operator of the protection pier, the surveyor, the comprehensive observer, the emergency assistant, and safety precautions, so that you have a clear understanding and are in an orderly manner.

[0177] 4) Beam dropping organization and job responsibilities: One general commander: issue action orders, fully control the overall situation of beam dropping, and directly command the person in charge of each pier top. Except for abnormal situations, pause every 100mm of dropping to accept the situation report of the person in charge of each pier. After all are correct, issue the order to lower the protection by 100mm and open the return oil valve.

[0178] Pier Top Person in Charge: Responsible for controlling and directing the work of each workstation on the pier, including the pump station, protective pier, surveying, comprehensive observation, and emergency assistance. He / she directs and coordinates all work on the pier top according to the orders of the commander-in-chief, regularly reports on the execution of orders, and promptly reports any abnormalities.

[0179] Each protective pier is operated by a team of two, responsible for removing the pier and steel plates from the pier. When removing, the plates should be pushed out halfway using bent slats and then carried manually. Hands should not be placed on the supporting surface, and premature removal of the plates is strictly prohibited. The steel plates should be neatly stacked in the designated location on the pier top.

[0180] One comprehensive observer will coordinate with the pier commander to provide comprehensive monitoring of the work progress at the pier. One emergency assistant will be assigned by the pier commander to support the corresponding workstation. The order of beam drop will be determined by alternating adjacent piers.

[0181] (2) Precautions during the beam lowering process: 1) After the jacking is in place, use a wedge-shaped wooden block to tighten between the lateral limit device and the beam body to prevent the beam body from slipping during the beam lowering process. 2) Carry out a comprehensive inspection of the beam body according to the design centerline displacement. After passing the inspection, start the beam lowering process. 3) First, push the beam up evenly by 100mm and remove the temporary pads and padding steel plates. 4) Ensure the lifting and lowering speed of each jacking machine by controlling the flow of the pump station. The beam lowering speed must not be too fast and must fall evenly. 5) Test and adjust the linearity of the beam body to meet the design and specification requirements, and anchor the support. 6) Strictly abide by the technical rules of the jacking machine, do not exceed the lifting capacity during lifting, and the lifting height each time shall not exceed three-quarters of the piston height. Unified command and unified action during operation. 7) The beam lowering control adopts proportional beam lowering control.

[0182] (3) After the steel box girder is lowered and pushed to the designed plane position, linear adjustment and beam lowering construction begins. The main steps are as follows: 1) Use a walking jack and pads at the support to lower the beam. Each pad is 100mm high and the pushing stroke of the pushing equipment is 200mm. 2) First, remove one layer of steel pads on the pushing equipment. At this time, the steel box girder is supported on the steel pads at the support. The vertical jack of the pushing equipment is lifted upward until it is tightly pressed against the bottom of the steel box girder, so that the steel box girder is re-supported on the steel pads of the pushing equipment. 3) Remove one layer of steel pads at the support, and then return the oil to the vertical jack of the pushing equipment to clear the steel pads on the jack and the bottom of the beam; the steel box girder is re-supported on the steel pads at the support. Repeat steps 2) to 3), removing the steel pads at the support and above the jack layer by layer; until the steel box girder is completely lowered to the support. During the process of lifting the steel box girder and lowering it to the support, all preparatory work on the pier should be sufficient to shorten the working time as much as possible; and during the process of lowering the beam, everything should be under the command of the main control console to ensure that the steel box girder falls accurately at the designed position.

[0183] Steel box girder drop process, D5 and D4 steel box girder drop, (1) drop height

[0184] After the D5 and D4 steel box girders were jacked to their designed positions, the DLSD-06 to DLSD-12 temporary supports were lowered using jacking equipment. A jacking model was created in CAD based on the designed pier elevations and the temporary support elevations. After simulation, the height of the beam dropped by the jacking device on the left side of the DLSD-06 temporary support is 70mm, and the height of the beam dropped by the jacking device on the right side is 70mm; the height of the beam dropped by the jacking device on the left side of the DLSD-07 temporary support is 50mm, and the height of the beam dropped by the jacking device on the right side is 50mm; the height of the beam dropped by the jacking device on the left side of the DLSD-08 temporary support is 144mm, and the height of the beam dropped by the jacking device on the right side is 144mm; the height of the beam dropped by the jacking device on the left side of the DLSD-09 temporary support is 200mm, and the height of the beam dropped by the jacking device on the right side is 200mm; the height of the beam dropped by the jacking device on the left side of the DLSD-10 temporary support is 202mm, and the height of the beam dropped by the jacking device on the right side is 202mm; the height of the beam dropped by the jacking device on the left side of the DLSD-11 temporary support is 312mm, and the height of the beam dropped by the jacking device on the right side is 380mm; the height of the beam dropped by the jacking device on the left side of the DLSD-12 temporary support is 473mm, and the height of the beam dropped by the jacking device on the right side is 541mm.

[0185] (2) Position of the beam dropping equipment: The beam dropping and pushing equipment is arranged on the temporary pushing supports DLSD-06 to DLSD-12.

[0186] (3) Beam dropping process

[0187] 1) During the beam drop, emergency protection is provided by removing steel pads piece by piece. 2) During the beam drop, the height difference between the steel box girder and each support is monitored. Once the steel box girder is jacked into position, the main bridge must be lowered onto the permanent stone bolster. This construction process is called unloading. After the steel box girder is jacked into position, beam drop jacks and pads are installed on temporary supports. This ensures that the weight of the steel box girder is borne by the beam drop jacks and pads, while the temporary bolster is unloaded. The temporary bolster is removed, and the vertical jacking support cylinders of the walking jack are simultaneously lowered, allowing the main bridge to fully drop onto the permanent stone bolster. The jacking support cylinders are then removed.

[0188] Beam dropping steps:

[0189] 1) When the front and rear pads of the jacking device are under force, remove the pad height of 100mm at the jacking device (the vertical lifting stroke of the jacking device is 200mm).

[0190] 2) Lift the jack until the jack is in full contact with the steel beam, and the front and rear pads of the jacking equipment are separated from the steel beam. At this time, remove the 100mm pads at the front and rear pads of the jacking equipment. Return the cylinder until the front and rear pads of the jacking equipment are in full contact with the steel beam. If the height of the dropped beam is less than 100mm, replace it with a steel plate of the same height, 450mm×450mm×10mm.

[0191] 3) Repeat the above steps until the steel beam contacts the support and the beam is lowered.

[0192] Beam drop construction control

[0193] (1) Preparation before beam dropping

[0194] The beam is lifted as a whole, and the reaction force at each fulcrum is calculated using the oil pressure of each jacking machine. Under this premise, the elevation of each fulcrum is uniformly measured, and a height measurement scale is arranged to intuitively determine the synchronization error of each fulcrum.

[0195] 1) Check the jacking machine and hydraulic system to ensure they are in good condition and reliable. Prepare the beam support piers.

[0196] 2) Verify whether the communication and command system is intact, unify the communication signals, unify the operating procedures and practice them to familiarize yourself with them.

[0197] 3) Hold an on-site briefing meeting to clarify the command system, beam lowering procedures and plans, responsibilities and operating instructions for each position including the person in charge of each pier, operators of each pump station, operators of protective piers, surveyors, comprehensive observers, emergency assistants, and safety precautions, so that everyone has a clear understanding and is organized.

[0198] 4) Organizational structure and job responsibilities of beam placement

[0199] One general commander: issues action orders, fully controls the overall situation of beam dropping, and directly commands the persons in charge of each pier top. Except for abnormal situations, he pauses every 100mm to receive situation reports from the persons in charge of each pier. After all are correct, he issues orders to lower the protection by 100mm and open the oil return valve.

[0200] Pier Top Person in Charge: Responsible for controlling and directing the work of each workstation on the pier, including the pump station, protective pier, surveying, comprehensive observation, and emergency assistance. He / she directs and coordinates all work on the pier top according to the orders of the commander-in-chief, regularly reports on the execution of orders, and promptly reports any abnormalities.

[0201] Each protective pier is operated by a team of two people, responsible for removing the pier and steel plates from the pier. When removing, the plates should be pushed out halfway using bent strips and then carried manually. Hands are not allowed to reach into the supporting surface, and premature removal of the plates is strictly prohibited. The steel plates should be neatly stacked in the designated location on the pier top.

[0202] Comprehensive observer: 1 person, to cooperate with the commander on the pier top to fully control the working situation of the pier.

[0203] Emergency assistant: 1 person, to accept the assignment from the pier top commander and support the corresponding work station.

[0204] The order of beam dropping is that adjacent piers start dropping beams alternately.

[0205] (2) Precautions during beam dropping

[0206] 1) After pushing into place, use a wedge-shaped wooden block to tighten between the lateral limit device and the beam body to prevent the beam body from slipping during the beam lowering process.

[0207] 2) Carry out a comprehensive inspection of the beam body according to the design centerline displacement, and start lowering the beam after passing the inspection.

[0208] 3) Push the beam up evenly by 100mm and remove the temporary pads and steel plates.

[0209] 4) Ensure the lifting and lowering speed of each jacking machine by controlling the flow of the pump station. The beam lowering speed must not be too fast and must fall evenly.

[0210] 5) Test and adjust the linearity of the beam to meet the design and specification requirements, and anchor the supports.

[0211] 6) Strictly follow the technical regulations of the jacking machine. When lifting, do not exceed the lifting capacity, and the lifting height at each time shall not exceed three-quarters of the piston height. During operation, unified command and unified action shall be followed.

[0212] 7) Beam dropping control adopts proportional beam dropping control.

[0213] (3) Steel box girder drop

[0214] When the steel box girder is pushed horizontally to the predetermined distance, the whole beam is dropped. Before dropping the beam, measurement work needs to be done to try to successfully drop the beam into place in one go.

[0215] Things to note when dropping beams are as follows:

[0216] 1) Emergency protection is provided by extracting steel plates piece by piece when the beam is dropped;

[0217] 2) Monitor the height difference between the steel box girder and each support during the beam dropping process;

[0218] After the pushing part is pushed into place and the hoisting part is hoisted into place, the main bridge must be lowered onto the permanent pad stone. This construction process is called unloading.

[0219] Matters not covered by the present invention are known technologies.

[0220] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. The integral jacking construction method for multiple eccentric and unequal-height steel box girders is characterized by: Erection of temporary scaffolding → Installation of jacking equipment → Assembly of the fifth section of D ramp → Installation of jacking guide beams and unequal height transition measures for steel box beams → Jacking of the fifth section of D ramp → Assembly of the fourth section of D ramp → Connection of the fifth and fourth sections of D ramp → Overall jacking of the fifth and fourth sections of D ramp → Sectional removal of guide beams during jacking → Dismantling of the connection of the fifth and fourth sections → Dropping of the fifth section of D ramp → Hoisting of the cross beams of the fifth section of D ramp → Hoisting of the cross beams of the fourth section of D ramp → Secondary jacking of the fourth section of D ramp → Dropping of the fourth section of D ramp 2. The method for integrally pushing multiple eccentric and unequal-height steel box girders according to claim 1 is characterized in that: Before the jacking construction, it is necessary to set up a transition measure for the uneven height of the steel box beam. Multiple sets of steel plates are welded into an inverted T-shaped joist to ensure that the uneven height steel box beam can be smoothly connected to the guide beam. At the same time, the slope area of ​​the steel beam with variable cross-section is eliminated, so that the jack can support the flat floor. Before the jacking construction, it is necessary to set up a jacking support. The jacking support includes a support foundation and a support structure. The support foundation adopts a concrete expanded foundation, which is a C25 concrete rectangular foundation with a foundation width range of 4500-6000mm, a height of 1000mm, and a length range of 7500-9000mm. A steel mesh is set inside the foundation at 50mm from the top, bottom and side surfaces, and a steel plate is embedded on the top surface of the foundation to facilitate welding and fixing with the steel pipe; The jacking support adopts steel pipe columns, which are connected into an integral whole by steel pipes. The horizontal distribution beam adopts double-piece steel, and the longitudinal distribution beam adopts triple-piece steel. The longitudinal distribution beam is equipped with walking jacks, front and rear steel piers, top caps, adjustment pads, and pads. The walking jacking equipment and pads are arranged in front and behind. The distribution beam evenly distributes the pressure on the pier top to the lower foundation concrete block. The pads are used for pier top elevation adjustment and beam dropping during the jacking process. The walking jacking device realizes the walking translation of the steel beam. The fifth and fourth steel box girders are formed into a whole by connecting blocks, realizing the overall jacking of multiple steel box girders. Since the expansion joints of steel box girders are generally short, it is not convenient to connect and dismantle the two steel box girders. This method achieves the expansion joint spacing requirements of the two steel box girders by removing the connecting blocks and then pushing the fourth girder twice, which is convenient for operation and control of connection quality.

3. The integral jacking construction method for multiple eccentric and unequal-height steel box girders according to claim 1 is characterized in that: During jacking construction, a walking jacking device is used. The walking jacking device includes a slide box structure, a slideway structure, a lifting jack structure, a translation jack structure, a deviation correction device structure, a hydraulic pump station system, a sub-control system and a master control system. The entire set of walking jacking equipment integrates traditional jacking and deviation correction into one, and separates the vertical jacking. Each set of walking jacking devices is centrally controlled by a master control system. The slide box of the walking-type jacking device is the load-bearing structure supporting the main beam. Two rubber plates or high-density wooden boards are placed on the upper part to balance the local force on the main beam. A stainless steel plate is welded to the lower part of the slide box, which constitutes a sliding surface with the polytetrafluoroethylene plate on the slide. The upper surface of the polytetrafluoroethylene plate is made into a mushroom head shape, and silicone oil is applied in between to reduce the friction resistance of the sliding surface. Two sets of correction devices with guide wheels are arranged on both sides of the slide, which can solve the guidance problem in the longitudinal direction of the bridge and the adjustment problem in the transverse direction of the bridge. The piston heads of the two lifting jacks are equipped with ball heads, which can adapt to the slope.

4. The integral jacking construction method for multiple eccentric and unequal-height steel box girders according to claim 1 is characterized in that: The D5 and D4 sections of the D ramp were installed using jacking. The steel box girders were lifted onto the assembly platform by a crane and assembled into a whole. After assembly, they were pushed into place using a three-dimensional jack. Before construction, temporary assembly supports and jacking supports were constructed. During the construction of the steel box girders, crawler cranes were used to lift and assemble individual components. The steel box girders were assembled on the temporary assembly supports, lifted using crawler cranes, and pushed into place using a three-dimensional jack. A total of 12 sets of assembly supports and 12 sets of jacking supports will be erected for the D4 and D5 steel box girders of the D ramp. Ten sets of crawler jacking equipment will be deployed, including 20 crawler jacking machines, 10 hydraulic pump stations, and 1 main control system. After the steel box girder is pushed into place, it is necessary to drop the girder in order to install it to the designed elevation. Therefore, the entire construction process includes 9 stages: (1) assembling the fifth steel box girder and guide beam on the assembly bracket and the pushing bracket, (2) continuing the pushing construction of the fifth steel girder, (3) hoisting the fourth steel girder and connecting it with the fifth steel girder, (4) continuing the pushing construction of the fifth and fourth steel box girders, and removing the guide beam in sections during the process until all the steel box girders are pushed into place, (5) dismantling the fifth and fourth steel beams, installing the fifth cross beam and then switching to drop the beam, (6) installing the fourth cross beam, (7) pushing the fourth steel box girder a second time, (8) switching to drop the fourth steel box girder system, (9) removing equipment and brackets.

5. The integral jacking construction method for multiple eccentric and unequal-height steel box girders according to claim 4 is characterized in that: The role of the guide beam is to reduce the construction internal force of the steel box girder during the jacking process, increase the jacking span, and play a guiding role. The guide beam is composed of two main beams and 3 cross braces. The two main beams of the guide beam are variable-section I-shaped sections. The two main beams of the guide beam are connected by steel pipe trusses. In order to make the guide beam better jack-pushing the pier, the front end of the guide beam is made into an upturned structure. The guide beam and the steel beam are connected by full-melt welding. A single guide beam is used. When the guide beam and the steel beam are assembled and welded, the measurement and layout are accurate to ensure that the linearity of the guide beam meets the jacking linearity. In order to facilitate construction, the web of the guide beam is arranged in plumb. At the same time, in order to match the inclined web structure of the steel box girder, a double web transition section is set at the connection between the guide beam and the steel box girder. The guide beam is partially provided with an inclined web member + straight web. The force of the inclined web of the steel box girder is transmitted to the straight web of the guide beam through the transition section. The guide beam is mainly composed of upper and lower flange plates, middle web plates, longitudinal stiffening ribs and vertical stiffening plates; The welding sequence of steel guide beam and steel box beam is as follows: welding the straight web of steel guide beam to the end of steel box beam → welding the inclined web of steel guide beam to the side web of steel box beam → welding the upper flange plate of steel guide beam to the top plate of steel box beam → welding the lower flange plate of steel guide beam to the bottom plate of steel box beam → welding the stiffening plate to the top plate and web plate; When the guide beam starts to be pushed from the first jacking platform, crosses the relevant lines, and reaches the jacking platform on the opposite side, it is necessary to prepare for the pier on the head end of the guide beam. When the guide beam cannot be smoothly put on the pier due to the downward deflection caused by its own weight, a vertical jack is set on the temporary pier to assist in the pier. When facing the pier, the jack of the facing pier is first retracted to the bottom, and the corresponding pad beam is set according to the height difference of the facing pier. Then, the steel beam is lifted up by the jack of the facing pier. After passing the walking jacking device, the slide box is returned to its original position, the load of the jack of the facing pier is unloaded and the load is transferred to the slide box. After the pier is faced, the pad is restored to the pushing state, and the walking jacking equipment of the pier is put into use. The specific operation steps of the guide beam pier are as follows: (1) Remove the steel pad at the front end of the jacking device to allow the front end of the guide beam to pass over the walking jacking device; (2) Use a jack to lift the front end of the guide beam upwards to eliminate the downward deflection of the guide beam and push it forward; (3) Add steel pads at the front end of the walking device, and transfer the guide beam load to the front end steel pads during the vertical return stroke; (4) The walking device horizontally pushes back, and the jack lifts the guide beam to make the front guide beam empty; (5) Repeat (1)-(4), push the guide beam forward until it passes over the step push slide box, push the front end equipment with a vertical jack and replace the steel pad step; (6) The guide beam reaches the equipment slider and the pier is completed; When encountering a support that needs to increase the design elevation, first let the guide beam pass the pier top, then use a jack to lift the guide beam, place a steel pad on the fulcrum, lower the jack so that the guide beam is re-supported on the steel pad, lower the jack to the lowest position, and place a steel pad on the jack, repeat this step until the fulcrum reaches the jacking elevation.

6. The method for integrally pushing construction of multiple eccentric and unequal-height steel box girders according to claim 1 is characterized in that: The jacking construction process for the fifth and fourth sections of the D ramp includes the following steps: Step 1: Equipment arrival, substructure construction, equipment installation and commissioning; Step 2: Lift the D5-I to D5-A sections, a total of 124 meters of steel box girders. The crossbeam at section A is divided into two sections. After the A2 section is pushed, it is lifted to the designed position by crane. After the steel beam is lifted, the steel guide beam is lifted. After the welding is completed, it is ready for pushing. Working condition analysis: A crawler crane is used to occupy the left and right sides of the steel beam, lifting I→H→G→F→E→D→C→B→A beam section→steel guide beam in sequence. The crawler crane is used to complete the lifting. The crane has a main boom of 39m and a swing radius of 16m. The rated load capacity under this working condition is 66.2t, which meets the lifting requirements. Step 3: After pushing 123.940 meters in the direction of greater mileage, stop pushing, adjust the bridge alignment, and prepare to hoist the D4-I to D4-C segments of the D4 joint; Step 4: Lift the 0.6m connecting block → lift the D4-I to D4-C segmental steel box girders. D4-G can be pushed with the crossbeam. The D4-I crossbeam is divided into sections I1 and I2, and the D4-D crossbeam is divided into sections D1 and D2. Sections I2 and D2 are not involved in the push. According to the working condition analysis, crawler cranes are used to occupy the left and right sides of the steel beam and lift the beam sections I→H→G→F→E→D→C in sequence. The maximum beam section weight G is 64.22t. A crawler crane is used to complete the lifting. The crane's main boom is 39m and the swing radius is 14m. The rated load capacity under this working condition is 78.1t, which meets the lifting requirements. When hoisting the 4-section D4-I to D4-C segments, first install the connection block and temporarily consolidate it with the D5-A segment of the D5 segment. Then temporarily consolidate the D4-I segment of the D4 segment with the other end of the connection block. The beam segments of the other segments of the D4 segment are connected according to the designed assembly sequence. The connection block is made of steel plate with a box-shaped section. The thickness of the steel plate is the same as that of the top, web and bottom plates. The connection block is set at the connection seam between the D5 segment and the D4 segment. The jacking can be continued only after the connection block is consolidated and welded. Step 5: After the D4-I to D4-C segments are welded, continue pushing 78.795 meters in the direction of the long mileage. After the guide beam reaches the D17# permanent pier, remove the 14m guide beam of the first segment; Step 6: Continue jacking after adjusting the alignment; gradually remove the remaining second and third segment guide beams until the fifth steel box girder is jacked into place. After the fifth steel box girder reaches the designed position, remove the temporary connection blocks of D5 and D4, and use crawler jacks on jacking supports No. 10-12 to lower the beams. After the beams are lowered, hoist the A2 beam section of Pier D15 in situ. The beam section weighs 14.1 tons and is hoisted using a 260-ton crawler crane with a 39-meter main boom and a 14-meter slewing radius. Under this condition, the rated load capacity is 31.3 tons, which meets the hoisting requirements. Step 7: The D4-I2 beam segment was hoisted in situ. The beam segment weighed 14.1t and was hoisted using a 260-ton crawler crane. The crane had a 39m main boom and a 14m swing radius. Under this working condition, the rated load capacity was 31.3t, meeting the hoisting requirements. Step 8: After the I2 beam segment is installed, it is pushed forward 480mm to the designed position. A crawler jack is used on the No. 6-9 pushing brackets to lower the beam. The remaining D4-D2 segment, D4-B segment, and D4-A segment steel box beams are hoisted in situ. The hoisting order is D2 → B2 → B3 → B1 → B4 → A segment. The maximum beam segment weight is 45.7t. A 260t crawler crane is used for the hoisting. The crane has a main boom of 39m and a swing radius of 18m. The rated load capacity under this working condition is 56.8t, which meets the hoisting requirements. Step 9: Dismantle equipment and temporary structures.

7. The integral jacking construction method for multiple eccentric and unequal-height steel box girders according to claim 6 is characterized in that: During jacking, the steel box girder deviation monitoring is required, including geometric monitoring and physical monitoring. The specific process of geometric monitoring is as follows: ① Displacement observation: Displacement observation mainly focuses on the centerline offset of the main bridge and the horizontal and vertical displacement of the jacking platform. During the jacking process, timely adjustments must be made using jacks. Observation of the jacking platform displacement is extremely important. The maximum displacement value is calculated based on the design allowable displacement. Coordinates are converted and continuous observation is conducted from the start of force application until the main beam begins to move. Once the displacement exceeds the design allowable value, force application is immediately stopped and the tension of each jack is readjusted. ② When pushing to the end, pay special attention to whether the main beam has reached the designed position. It must be pushed to the final position at night when the temperature is stable, and the beam length must be carefully calculated and measured based on the temperature. When pushing for the last time, a small stroke should be used to facilitate deviation correction and longitudinal movement into place. ③ In actual construction, there will be uncertainties and there may be deviations during the jacking process. Based on the feedback of linear coordinates and measurement data, the lateral correction function of the walking jacking equipment is used to make timely corrections and adjustments. All walking jacks under the beam section and guide beam are lifted at the same time. The correction data of each walking jack is input on the main console, and then all jacks are started at the same time to complete the lateral correction action synchronously. After verification, the jacking construction continues; The specific process of physical monitoring is as follows: During the jacking process, the jacking force needs to be monitored in real time. The friction force is calculated based on the fulcrum reaction force under various working conditions and verified with the oil pressure gauge. The fulcrum reaction force under each working condition is measured by the pier top monitoring element. The magnitude of the jacking force is automatically adjusted according to the magnitude of the frictional resistance and is reflected by the oil gauge. The jack must be calibrated as required before use, and the oil gauge should be calibrated. When applying jacking force under each working condition, first gradually increase the force of the jacks on each pier to the calculated jacking force. During the jacking process, try to control the force balance of each jacking jack; the specific process is: ① Monitoring the deflection of the box girder during the jacking process, ② Monitoring the stress of the key sections of the main bridge and temporary supports and stress concentration points during the jacking process, ③ Monitoring the magnitude of the jacking force during the jacking process, ④ Monitoring the temperature during the jacking process, and ⑤ Monitoring the wind environment during the jacking process.

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