Non-grounded Bracket System and Construction Method for In-situ Box Girder on Small-radius Curve

Abstract

The present invention relates to a non-grounded support system and construction method for cast-in-situ box girders with small-radius curves, and is used for the non-grounded support system of the 1st - 3rd continuous cast-in-situ curves with a radius R = 60m on the H ramp bridge. The present invention adopts an upper and lower hoop structure, places three layers of I-beam main girders on the hoop ear plates, so that the three layers of main girders of the small-radius curve are guaranteed to be mutually connected with the nodes of the Bailey truss above them. The 321-type Bailey truss is placed on the upper main girder, the I14 distribution beam is erected at the upper end of the Bailey truss, the bottom support of the disk buckle support is placed on the distribution beam, the I12.6 I-beam is placed inside the top support of the disk buckle support to form a longitudinal distribution beam, 10×10 cm square timbers are laid on the longitudinal distribution beam, and 15 mm bamboo plywood is laid on the square timbers. The present invention forms a non-grounded support system for cast-in-situ box girders with small-radius curves, so as to solve the problems that it is impossible to erect in complex terrains, geologies and landforms such as soft geology, steep slopes, limited construction sites or crossing large rivers, and the support nodes of cast-in-situ box girders with small-radius curves cannot be corresponded.

Description

Technical Field

[0001] The present invention relates to a non-grounded support system and construction method for cast-in-situ box girders with small radius curves. Background Art

[0002] With the improvement of bridge technology in China, the quality requirements for bridges are also getting higher and higher. Cast-in-situ box girders play an important role in bridge construction due to their advantages such as simple appearance, large torsional stiffness, good integrity, and strong applicability. The construction of box girder supports is very important in the construction process of cast-in-situ box girders (or: cast-in-situ bridge decks). The stability of the connection of box girder supports affects the safety of construction and the construction process. However, existing box girder supports cannot be erected in complex terrains, geologies, and landforms such as soft geology, steep slopes, limited construction sites, or crossing large rivers, and there are also problems where the nodes of the cast-in-situ box girder supports with small radius curves cannot be corresponding.

[0003] For example, in the LJ-15 contract section of the southern section of the Xi'an Outer Ring Expressway, the total length of the route is 3.4 km. The main project within the section is the Lantian South Hub Interchange, which is a project control project, including 22 continuous cast-in-situ box girders. The structural form, interchange relationship, and geological and hydrological conditions in the bridge site area are complex. Among them, the curve radius of the cast-in-situ box girder on the first to third pier column groups of the H ramp bridge is R = 60 m, and the lower part is located on the Wanyu River channel and floodplain with poor geology. There is constant flowing water in the river channel, and the water flow is large during the flood season. If the construction uses a grounded support, the requirement for the bearing capacity of the foundation is relatively high. The ground at the bridge site needs to be extensively replaced for the foundation, and at the same time, it is necessary to build gabion protection. The comprehensive cost is relatively high and there are relatively large hidden dangers.

[0004] Existing Chinese patents have disclosed a box girder support with the authorization announcement number CN213709222U and the publication date of July 16, 2021. This patented technology includes vertical poles, horizontal bars, inclined bars, disc fittings, and pins; the disc fittings are fixed on the vertical poles, and the axis is perpendicular to the axis of the vertical poles; both ends of the horizontal bar are fixed with first plugs inserted into the disc fittings; both ends of the inclined bar are fixed with second plugs inserted into the disc fittings; the first plugs and the second plugs have the same thickness, and a slot with the same thickness as the disc fittings is opened at one end of the first plugs and the second plugs close to the disc fittings. A third slot is opened on the slot; a first slot matching the third slot on the first plug and a second slot matching the third slot on the second plug are opened on the disc fittings; the pin can simultaneously pass through the first slot and the third slot and the second slot and the third slot structure, solving the problem of the instability of the box girder support. However, there are still problems where it cannot be erected in complex terrains, geologies, and landforms such as soft geology, steep slopes, limited construction sites, or crossing large rivers, and the nodes of the cast-in-situ box girder supports with small radius curves cannot be corresponding. Summary of the Invention

[0005] The object of the present invention is to provide a non-grounded support system and construction method for cast-in-situ box girders with small-radius curves, so as to solve the problems that cannot be erected in complex terrains, geologies, and landforms such as soft geology, steep terrain, limited construction sites, or crossing large rivers, and the problem that the support nodes of cast-in-situ box girders with small-radius curves cannot be corresponded, which are proposed in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A non-grounded support system for cast-in-situ box girders with small-radius curves includes a first-connected pier column group and upper hoops. Upper hoops and lower hoops are successively arranged from top to bottom on the same surface of the upper parts of each pier column of the first to third-connected pier column groups distributed in a curve radius. There is a strengthening support structure between the lower end of each lower hoop and the upper end of the corresponding intermediate beam of the connected pier group. The hoop ear plates on both sides of each upper and lower hoop are distributed circumferentially;

[0008] Both sides of the two lower main beams are respectively placed on the hoop ear plates on both circumferential sides of the same connected pier column group, and the inner sides of the two lower main beams of the same connected pier column group are tightly attached to the corresponding pier columns;

[0009] Three middle main beams are arranged at the upper two sides and the middle of the two lower main beams at circumferentially spaced distances. The length of the middle main beam is greater than the width of the two lower main beams;

[0010] One upper main beam distributed radially is respectively arranged at the upper two sides of the middle main beam. The distance between adjacent upper main beams of adjacent connected pier column groups is the same;

[0011] A number of Bailey beams are arranged side by side between adjacent upper main beams of adjacent connected pier column groups. The two ends of each Bailey beam are welded to the upper main beam at the corresponding part with ∠7.5×5mm angle steel in a "door" shape;

[0012] A number of transverse distribution beams distributed radially are arranged at the upper ends of each Bailey beam. Each transverse distribution beam and the upper end of the corresponding Bailey beam are fixed by U-shaped clamps;

[0013] Scaffold with socket couplings is arranged at the upper ends of each transverse distribution beam. The outer diameter of the vertical pole of the scaffold with socket couplings is 48mm, the wall thickness is 3.2mm, the step distance of the vertical and horizontal horizontal bars is 1m. An adjustable base is arranged under each vertical pole of the scaffold with socket couplings. Each vertical pole is vertically arranged. A construction platform is erected at the outer edge part of the top wing plate of the scaffold with socket couplings, and a guardrail is arranged on the scaffold with socket couplings outside the construction platform;

[0014] Between the top wing plate of the cast-in-situ box girder to be constructed and the scaffold with socket couplings, bamboo plywood as a formwork, a number of transverse square timbers and longitudinal distribution beams are respectively arranged from top to bottom.

[0015] As a further solution of the present invention: the strengthening support structure is composed of a strengthening support column, a telescopic column, a support ring, a transverse fixing column, a clamping plate, a clamping groove and a fixing bolt. The strengthening support column and the telescopic column are rectangular columns. The lower part of the strengthening support column is slidably fitted inside the upper part of the telescopic column. Fixed holes are correspondingly arranged at intervals on the two side edges of the lower part of the strengthening support column and the two side edges of the upper part of the telescopic column. The fixing bolt is simultaneously located in the horizontally corresponding fixed holes to fix the strengthening support column inside the telescopic column. A clamping plate capable of being horizontally clamped into the middle beam of the pier column is arranged at the lower end of the telescopic column. A support ring for supporting the lower end of one side of the lower hooping is arranged at the upper end of the strengthening support column. Clamping grooves are correspondingly arranged at intervals on the corresponding side edges of adjacent strengthening support columns and telescopic columns. The lower ends of both sides of the transverse fixing column are provided with clamping tongues. The two ends of the transverse fixing column are respectively clamped into the corresponding clamping grooves through the clamping tongues to fix the distance between adjacent strengthening support columns and telescopic columns, so that the outer side surfaces of the strengthening support column and the telescopic column are abutted against the corresponding side surfaces of the pier column.

[0016] As a further solution of the present invention: the lower end surface of the upper hooping abuts against the upper end surface of the lower hooping.

[0017] As a further solution of the present invention: the two lower main cross beams of the same group of pier columns are fixed by a tie rod or a U-shaped bolt.

[0018] As a further solution of the present invention: the height from the top surface of the upper hooping to the lower end of the cast-in-place box girder to be constructed is equal to the sum of the thickness of the bamboo plywood, the height of the wooden block, the height of the longitudinal distribution beam, the height of the disc buckle support, the height of the transverse distribution beam, the height of the Bailey beam, the height of the lower main cross beam, the height of the middle main cross beam and the height of the upper main cross beam at the corresponding part.

[0019] As a further solution of the present invention: the intersection surfaces between the lower main cross beam, the middle main cross beam and the upper main cross beam are all connected by spot welding.

[0020] A construction method for a non-grounded support system of a small-radius curve cast-in-place box girder includes the following steps:

[0021] (1) Preparation stage: Prepare the upper and lower hoopings, plywood, wooden blocks, longitudinal distribution beams, disc buckle support materials, transverse distribution beams, Bailey beams, lower main cross beams, middle main cross beams, upper main cross beams, U-shaped bolts, tie rods, strengthening support structure members, scaffolding members, combined climbing ladder members for building the non-grounded support system; welding machines, cranes and other related equipment.

[0022] (2) Measuring and lofting: Before constructing the non-grounded support system, carry out construction lofting on each pier column of the first to third groups of pier columns distributed in a curve radius R = 60m, measure the midpoint and column top elevation of the two pier columns in the same group, and at the same time calculate the total height of the non-grounded support system and the supporting height of each component during the construction of the cast-in-place beam, which is beneficial to adjusting the elevation according to the situation of each component during construction to meet the construction requirements.

[0023] (3)Installation of upper and lower hoops: The height of the upper hoop is 900 mm, the thickness is 16 mm, the length of the hoop ear plate is 350 mm, and the thickness is 20 mm. 24 M30 high-strength bolts are used to connect each side of the lower hoop. The height of the lower hoop is 350 mm, the thickness is 16 mm, the length of the hoop ear plate is 350 mm, and the thickness is 20 mm. 12 M30 high-strength bolts are used to connect each side of the hoop. The lower end face of the lower hoop is supported on the corresponding embedded steel bars of the pier column, and the embedded steel bars serve as the support components for the safety reserve of the non-grounded support system.

[0024] Calculate the construction height between the bottom surface of the cast-in-place box girder and the top surface of the upper hoop according to the total height of the non-grounded support system designed for construction. When positioning the hoops on each pier column, first subtract the construction height from the non-grounded support system to the top surface of the upper hoop from the designed elevation of the cast-in-place box girder on the road, which is the top surface elevation of the upper hoop. Use the method of hanging a ruler to lead the ground elevation to the pier column, and mark the top surface elevation line of the upper hoop on the pier column. Mark the horizontal position of the upper hoop and measure it with a spirit level to ensure that the upper hoop is vertically aligned with the pier column to ensure the stable installation of the upper hoop. Before installing the upper hoop, check the bearing capacity of the hoop and remove rust. When installing each hoop on the pipe column, use a high-altitude platform vehicle to install each hoop at the elevation position, and first preliminarily connect the two hoops with bolts on the ground. After connecting the hole positions of the hoop with bolts one by one, put on the nuts. The tightening degree of the nuts is only to screw the nuts until the outer rim of the nut is flush with the screw rod. Then, wedge the gap between the hoops temporarily with square wooden strips; then pass the steel wire rope through the bolt holes at the top of the bracket legs of each hoop for fixing the I-beam. After symmetrically passing through, hoist the hoop. The hoisting method is to put the hoop on the outside of the pier column from above the pipe column, and use manual labor to assist in positioning at the top of the column. The hoop ear plates on both sides of each upper and lower hoop are distributed circumferentially; when tightening each hoop, apply pre-tension to each high-strength bolt for tightening the hoop in parallel, that is, evenly screw each bolt on each side to a similar firmness level, and observe the joint surface between the hoop and the pier column to prevent the pier column from being subjected to eccentric pressure due to uneven tightening of the high-strength bolts, causing construction hazards.

[0025] (4)Setting of the strengthening support structure: After the construction of the upper and lower hoops is completed, strengthen the support columns and telescopic columns between the lower end face of the lower hoop on the inner side of the same-connected pier column group and the vertical upper end face of the middle beam of the pier column in the same-connected pier column group. The lower part of the strengthening support column is slidably fitted inside the upper part of the telescopic column. The clamping plate at the lower end of the telescopic column is transversely clamped into the corresponding middle beam of the pier column. The top surface of the support ring at the upper end of the strengthening support column is supported on the lower end of the corresponding side of the lower hoop. A number of fixing bolts are inserted into the corresponding fixing holes located horizontally to fix the strengthening support column inside the telescopic column. The two ends of the transverse fixing column are respectively clamped into the corresponding clamping grooves through the clamping tongues to fix the distance between the adjacent strengthening support column and the telescopic column, so that the outer sides of the strengthening support column and the telescopic column are abutted against the corresponding side of the pier column;

[0026] (5) Installation of each main cross beam: The lower main cross beam, middle main cross beam, and upper main cross beam are successively installed on the upper end face of the upper hoop. The two sides of the two lower main cross beams are respectively placed on the hoop ear plates on the circumferential two sides of the same group of pier columns. The inner sides of the two lower main cross beams of the same group of pier columns are closely attached to the corresponding pier columns. The lower main cross beam is composed of double-pinned I56a steel beams welded side by side into one body. The two lower main cross beams of the same group of pier columns are fixed by tie rods or U-shaped bolts.

[0027] On the upper two sides and the middle of the two lower main cross beams, there are three middle main cross beams distributed circumferentially and at intervals. The length of the middle main cross beam is greater than the width of the two lower main cross beams.

[0028] On the upper two sides of the three middle main cross beams, there is one upper main cross beam distributed radially respectively. The distance between the adjacent upper main cross beams of the adjacent groups of pier columns is the same; the middle and upper main cross beams are both composed of double-pinned I56a steel beams welded side by side into one body.

[0029] Or the intersection part between the lower end of the lower main cross beam and the hoop ear plate and the intersection parts between the lower, middle, and upper main cross beams are connected by spot welding to ensure stability.

[0030] (6) Installation of each Bailey beam: A number of Bailey beams are arranged side by side between the adjacent upper main cross beams of the adjacent groups of pier columns. The Bailey beam is a truss steel beam composed of standard Bailey sheets. The spacing of each group of Bailey trusses is arranged according to the drawing requirements. During installation, first connect the Bailey sheets with 90 cm or 45 cm shaped windows under the bridge, longitudinally assemble to the specified length, and then use a truck-mounted crane to lift the assembled Bailey truss to the position of the upper main cross beam determined by measurement and lofting. After all the Bailey beams are installed on the upper main cross beams, the two ends of each Bailey beam are welded to the corresponding upper main cross beam with ∠7.5×5 mm angle steel in a "door" shape;

[0031] (7) Installation of transverse distribution beams: A number of transverse distribution beams are arranged radially and at intervals on the upper ends of each Bailey beam. The transverse distribution beams are made of I14 and I12.6 steel beams. Each transverse distribution beam is fixed to the upper end of the corresponding Bailey beam by a U-shaped clamp;

[0032] (8) Construction of the disc buckle support: The disc buckle support is provided on the upper end of each transverse distribution beam disc. The outer diameter of the vertical rod of the disc buckle support is 48 mm, and the wall thickness is 3.2 mm. The step distance of the longitudinal and horizontal horizontal rods is 1 m. An adjustable base is provided under each vertical rod of the disc buckle support. Each vertical rod is vertically arranged. A construction platform is erected on the outer edge part of the top wing plate of the disc buckle support, and a guardrail is provided on the disc buckle support outside the construction platform;

[0033] Adjustable supports are provided on the top surfaces of the vertical poles of the socket - and - spigot support. The cantilever length of the adjustable support extending from the top - layer horizontal pole is less than 650 mm, the exposed length of the screw rod of each adjustable support is less than 400 mm, and the length of the adjustable support inserted into the vertical pole is greater than 150 mm;

[0034] When the socket - and - spigot support approaches the designed elevation, surveyors provide a reference point every 5 m circumferentially at the edges of the bottom slab and wing slab of the box girder to be cast - in - place for stringing and leveling;

[0035] (9) Construction of longitudinal distribution beams: After the socket - and - spigot support passes the acceptance inspection, longitudinal distribution beams are laid on the adjustable supports on each vertical pole of the socket - and - spigot support. The longitudinal distribution beams are I12.6 steel I - beams, and the spacing between adjacent longitudinal distribution beams is the same as the spacing of the cross - bars on the vertical poles;

[0036] (10) Construction of transverse square timbers: 10×10 cm transverse square timbers are laid on the longitudinal distribution beams, and the spacing between adjacent transverse square timbers is 30 cm. After laying, the elevation of the transverse square timbers is re - checked. For individual low - lying areas, hand - held wooden wedges are used to level them, and for high areas, they are planed flat with an electric planer. After the elevation of the transverse square timbers meets the requirements, pre - loading operations can be carried out. After the pre - loading is qualified, bamboo plywood serving as the formwork for the box girder to be cast - in - place is set on the transverse square timbers.

[0037] As a further solution of the present invention: The longitudinal distribution beams and the transverse square timbers are fixed by wire binding, and the bamboo plywood and the transverse square timbers are fixed by steel nails.

[0038] As a further solution of the present invention: The support ring at the upper end of the strengthening support column is arc - shaped, the radian and thickness of the support ring are the same as those of the lower hoop, and a wedge block can be provided between the lower end of the clamping plate at the lower end of the telescopic column and the upper end of the corresponding pier intermediate beam.

[0039] As a further solution of the present invention: Combined ladders for personnel passage are provided on the upper and lower supports of the upper main cross - beam, Bailey beam, socket - and - spigot support, and construction platform.

[0040] The beneficial effects of the present invention are:

[0041] 1. Compared with the prior art, the present invention has a wide range of applications and can be applied to the construction of cast-in-situ box girders (or: cast-in-situ bridge slabs) with small radius curves where it is impossible to erect floor-standing support structures on the ground such as across rivers, lakes, seas, and existing roads. In a specific embodiment of the present invention, since the cast-in-situ curve radius of the 1st - 3rd continuous spans of the H ramp bridge is R = 60m, the present invention adopts an upper and lower hoop structure, places three layers of I-beam main girders on the hoop ear plates, so that the three layers of main girders of the small radius curve ensure mutual connection with the nodes of the Bailey beams above them. Place 321-type Bailey beams on the upper main girder, erect I14 distribution beams at the upper end of the Bailey plates, place the bottom supports of the disc buckle supports on the distribution beams, place I12.6 I-beams in the top supports of the disc buckle supports to form longitudinal distribution beams, lay 10×10cm square timbers on the longitudinal distribution beams, and lay 15mm bamboo plywood on the square timbers to form a non-floor support system for the cast-in-situ box girders with small radius curves. The present invention makes it possible to construct cast-in-situ box girders with small radius curves where it is impossible to erect floor-standing support structures on the ground such as across rivers, lakes, seas, and existing roads.

[0042] 2. Compared with the prior art, when constructing cast-in-situ box girders with small radius curves in areas where it is impossible to erect floor-standing support structures on the ground such as across rivers, lakes, seas, and existing roads, the present invention does not require the erection of full hall scaffolds from the ground upwards, avoiding the danger of river water scouring in the Wangyu River channel and circumventing the risk of workers falling from high places during the erection process, ensuring the safety of construction workers from the source. At the same time, compared with the floor-standing support method, it can save the steel consumption of the support, and there is no need for subgrade replacement and site hardening, accelerating the construction progress and shortening the construction period.

[0043] 3. After measurement, when the present invention is applied to the construction of the 5th - 7th continuous spans of the cast-in-situ box girders of the H ramp bridge in the LJ-15 contract section of the southern section of the Xi'an Outer Ring Expressway, compared with the prior art non-floor box girder supports, it can save 28% of the steel consumption of the support, and there is no need for subgrade replacement and site hardening of the construction ground, reducing the construction cost by 76% and shortening the construction period by 67%. The economic benefit is increased by two times, providing a new idea for the construction of future cast-in-situ box girder projects.

[0044] The following further explains the present invention with reference to the accompanying drawings. Description of the Drawings

[0045] Figure 1 It is a structural schematic diagram of the non-floor support system of the present invention;

[0046] Figure 2 It is Figure 1 A three-dimensional schematic diagram of the sectional structure of part A - A in

[0047] Figure 3 It is a schematic diagram of the distribution structure of the main girders of the non-floor support system with small radius curves of the present invention;

[0048] Figure 4 It is a schematic diagram of the distribution structure of the Bailey beams on each main girder of the present invention;

[0049] Figure 5 Schematic diagram of the reinforcement support structure of the present invention;

[0050] Figure 6 Schematic diagram of the structure of the other side of the reinforcement support structure of the present invention;

[0051] Figure 7 Schematic diagram of the structure for fixing the Bailey beam and the transverse distribution beam of the present invention;

[0052] Figure 8 Schematic diagram of the structure of the U-shaped clamp of the present invention;

[0053] Figure 9 Schematic diagram of the structure of the upper hoop of the present invention;

[0054] Figure 10 Schematic diagram of the side structure of the upper hoop of the present invention;

[0055] Figure 11 Schematic diagram of the side structure of the lower hoop of the present invention. Detailed implementation manners

[0056] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments. However, the following embodiments are only the preferred embodiments of the present invention, not all. Based on the embodiments in the embodiments, other embodiments obtained by those skilled in the art without creative efforts all belong to the protection scope of the present invention. The methods in the following embodiments are all conventional methods unless otherwise specified, and the materials, devices, equipment, etc. used in the following embodiments can all be obtained from commercial channels unless otherwise specified.

[0057] Embodiment 1: Please refer to Figures 1 to 11 , a non-ground support system for a cast-in-place box girder (or: cast-in-place bridge slab) with a small radius curve. As Figures 1 to 4 shown, it includes the first set of pier columns 1 and the upper hoop 17. On the same surface of the upper parts of each pier column of the first set of pier columns 1, the second set of pier columns 22, and the third set of pier columns 23 distributed in a curve radius, the upper hoop 17 and the lower hoop 18 are successively arranged from top to bottom. Between the lower end of each lower hoop and the upper end of the corresponding intermediate beam 2 of the connected piers, there is a reinforcement support structure, and the two-side hoop ear plates 7 of each upper and lower hoop are distributed circumferentially.

[0058] The two sides of the two lower main cross beams 8 are respectively placed on the hoop ear plates 7 on the two circumferential sides of the same set of pier columns, and the inner sides of the two lower main cross beams 8 of the same set of pier columns are closely attached to the corresponding pier columns.

[0059] On both sides of the upper ends and the middle part of the two main crossbeams, there are three middle main crossbeams 9 that are circumferentially spaced apart. The length of the middle main crossbeam 9 is greater than the width of the two main crossbeams, and the lengths of both sides of the same middle main crossbeam 9 located outside the two main crossbeams are the same.

[0060] On the upper ends of both sides of the middle main crossbeam, there is a main upper crossbeam 10 that is radially distributed respectively. The distance between adjacent main upper crossbeams 10 of adjacent two-connected pier column groups is the same.

[0061] Between adjacent main upper crossbeams 10 of adjacent two-connected pier column groups, there are several Bailey beams 16 arranged side by side. The two ends of each Bailey beam are welded to the corresponding main upper crossbeam with ∠7.5×5mm angle steel in a "door" shape.

[0062] As Figure 7 and Figure 8 shown, on the upper ends of each Bailey beam, there are several transverse distribution beams 11 that are radially distributed. Between each transverse distribution beam 11 and the upper end of the corresponding Bailey beam, they are fixed by U-shaped clamps 28. The two ends of the U-shaped clamp 28 are respectively provided with external thread parts, and nuts 30 are respectively screwed on the external thread parts. A gasket 29 is arranged above the nut.

[0063] On the upper end of each transverse distribution beam plate, there is a disk-locked support 15. The outer diameter of the vertical rod of the disk-locked support is 48mm, the wall thickness is 3.2mm, the step distance of the vertical and horizontal horizontal rods is 1m. An adjustable base is provided under each vertical rod of the disk-locked support 15, and each vertical rod is vertically arranged. A construction platform 20 is built on the outer edge part of the top wing plate of the disk-locked support, and a guardrail 21 is arranged on the disk-locked support outside the construction platform; the construction platform is for construction personnel to stand on for construction.

[0064] Between the cast-in-place box girder 13 to be cast and the top wing plate of the disk-locked support, there are bamboo plywood as the formwork, several transverse square timbers 12 and longitudinal distribution beams 14 from top to bottom respectively.

[0065] As Figure 1 and Figure 5 and Figure 6As shown in the figure, the reinforcement support structure is composed of a reinforcement support column 4, a telescopic column 27, a support ring 6, a transverse fixing column 19, a clamping plate 3, a clamping groove 5 and a fixing bolt 25. The reinforcement support column 4 and the telescopic column 27 are rectangular columns. The lower part of the reinforcement support column is slidably fitted inside the upper part of the telescopic column. A plurality of fixing holes 26 are provided at intervals on the two side edges of the lower part of the reinforcement support column and the two side edges of the upper part of the telescopic column corresponding to each other. When the fixing bolt 25 can be located in the horizontally corresponding fixing holes at the same time, the reinforcement support column is fixed inside the telescopic column, which is used to adjust the lengths of the reinforcement support column and the telescopic column. The lower end of the telescopic column 27 is provided with a clamping plate 3 that can be transversely clamped into the middle beam 2 of the pier column, which is used to distribute force and fix the reinforcement support column and the telescopic column. The upper end of the reinforcement support column 4 is provided with a support ring 6 that supports the lower end of one side of the lower hooping band 18. Clamping grooves 5 are provided at intervals on the corresponding side edges of adjacent reinforcement support columns and telescopic columns. The lower ends of both sides of the transverse fixing column 19 are provided with clamping tongues 24. When the two ends of the transverse fixing column are respectively clamped into the corresponding clamping grooves through the clamping tongues 24, the distance between adjacent reinforcement support columns and telescopic columns can be fixed, so that the outer side surfaces of the reinforcement support columns and the telescopic columns are abutted against the corresponding side surfaces of the pier columns.

[0066] The lower end surface of the upper hooping band abuts against the upper end surface of the lower hooping band, which is used to jointly bear the pressure of each support.

[0067] The two lower main cross beams of the same continuous pier column group are fixed by tie rods or U-bolts.

[0068] The height from the top surface of the upper hooping band to the lower end of the cast-in-place box girder to be constructed is equal to the sum of the thicknesses of the bamboo plywood, the heights of the wooden blocks, the longitudinal distribution beams, the disk buckle support materials, the transverse distribution beams, the Bailey beams, the lower main cross beam, the middle main cross beam and the upper main cross beam at the corresponding parts.

[0069] The lower main cross beam, the middle main cross beam and the intersection surfaces of the upper main cross beam can all be connected by spot welding.

[0070] A construction method for a non-grounded support system of a small-radius curve cast-in-place box girder includes the following steps:

[0071] (1) Preparation stage: Prepare the upper and lower hooping bands, plywood, wooden blocks, longitudinal distribution beams, disk buckle support materials, transverse distribution beams, Bailey beams, lower main cross beams, middle main cross beams, upper main cross beams, U-bolts, tie rods, reinforcement support structure members, scaffolding members, combined climbing ladder members for building the non-grounded support system; welding machines, cranes and related equipment.

[0072] (2) Measurement and lofting: Before constructing the non-grounded support system, the maximum height of the pier columns of the first to third continuous spans is 27m. Construction lofting is carried out on each pier column of the first to third continuous span pier column group distributed with a curve radius R = 60m. The midpoint and column top elevation of two pier columns in the same group are measured. At the same time, the total height of the non-grounded support system and the support heights of each component during the construction of the cast-in-place beam are calculated, which is conducive to adjusting the elevation according to the situation of each component during construction to meet the construction requirements.

[0073] (3) Construction of upper and lower hoops: The height of the upper hoop 17 is 900mm, the thickness is 16mm, the length of the hoop ear plate is 350mm, and the thickness is 20mm. Each side of the lower hoop is connected by 24 M30 high-strength bolts.

[0074] The height of the lower hoop is 350mm, the thickness is 16mm, the length of the hoop ear plate is 350mm, and the thickness is 20mm. Each side of the hoop is connected by 12 M30 high-strength bolts.

[0075] Hole positions 31 for high-strength bolts to pass through are provided on each hoop ear plate.

[0076] The lower end face of the lower hoop 18 is supported on the corresponding pier column embedded steel bars, and the embedded steel bars serve as safety reserve support members for the non-grounded support system;

[0077] According to the total height of the designed non-grounded support system, calculate the construction height between the bottom surface of the cast-in-place box girder and the top surface of the upper hoop. When positioning the hoops on each pier column, first subtract the construction height from the non-grounded support system to the top surface of the upper hoop from the designed elevation of the cast-in-place box girder 13 to be constructed, which is the top surface elevation of the upper hoop. Use the method of hanging a ruler to lead the ground elevation to the pier column, and mark the top surface elevation line of the upper hoop on the pier column. Mark the horizontal position of the upper hoop and measure it with a spirit level to ensure that the upper hoop is vertically aligned with the pier column to ensure the stable installation of the upper hoop. Before installing the upper hoop, check the bearing capacity of the hoop and remove rust.

[0078] When installing the pipe columns on each hoop, use a high-altitude platform vehicle to install each hoop at the elevation position. First, preliminarily connect the two hoops with bolts on the ground, that is, after connecting the hole positions 31 of the hoops with bolts one by one, put on the nuts. The tightening degree of the nuts is only to screw the nuts until the outer rim can be seen flush with the screw rod. Then, wedge the gap between the hoops tightly with square wooden strips temporarily; then pass the steel wire rope through the bolt holes at the top of the brackets of each hoop for fixing the I-beam. After symmetrically passing through, hoist the hoop. The hoisting method is to put the hoop on the outside of the pier column from above the pipe column, and use manual labor to assist in positioning at the column top to speed up the construction progress.

[0079] The ear plates on both sides of each upper and lower clamp are distributed in the circumferential direction; when tightening each clamp, pre-tension is applied in parallel to each high-strength bolt tightened by each clamp, that is, the bolts on each side are evenly tightened to a similar degree of firmness, and the joint surface between the clamp and the pier column is observed to prevent the pier column from being subjected to bias pressure due to uneven tightening of the high-strength bolts, which may cause construction hazards.

[0080] (4) Strengthening the support structure: The function of the strengthening support structure is to transmit the pressure of the upper and lower clamps to the middle beam 2 of the pier column to ensure the stability of the support.

[0081] After the construction of the upper and lower clamps is completed, a reinforcing support column 4 and a telescopic column 27 are arranged between the lower end surface of the lower clamp 18 on the inner side of the same connected pier column group and the vertical upper end surface of the pier column middle beam 2 of the same connected pier column group, the lower part of the reinforcing support column is slidably fitted in the upper part of the telescopic column, the clamping plate 3 at the lower end of the telescopic column is horizontally inserted into the corresponding pier column middle beam 2, the top surface of the supporting ring 6 at the upper end of the reinforcing support column is supported on the lower end of the corresponding side of the lower clamp 18, and three fixing bolts 25 are inserted into the corresponding fixing holes in the horizontal direction to fix the reinforcing support column in the telescopic column. The two ends of the transverse fixing column 19 are respectively inserted into the corresponding card grooves through the clamping tongues to fix the distance between the adjacent reinforcing support columns and the telescopic columns so that the outer side surfaces of the reinforcing support columns and the telescopic columns are supported on the corresponding pier column sides.

[0082] The support ring at the upper end of the reinforced support column is arc-shaped, and the curvature and thickness of the support ring are the same as those of the lower hoop. A wedge can be provided between the lower end of the clamping plate at the lower end of the telescopic column and the upper end of the corresponding pier middle beam to ensure that the reinforced support column 4 and the telescopic column 27 are tightly held between the lower end surface of the lower hoop 18 and the vertical upper end surface of the pier middle beam 2 of the same connected pier group.

[0083] (5) Installation of each main crossbeam: The lower main crossbeam, the middle main crossbeam and the upper main crossbeam are installed on the upper end surface of the upper clamp in sequence. The two sides of the two lower main crossbeams are respectively placed on the clamp ear plates located on the circumferential sides of the same pier column group. The inner sides of the two lower main crossbeams of the same pier column group are set close to the corresponding piers. The lower main crossbeam is made of double-piece I-beams I56a welded side by side. The two lower main crossbeams of the same pier column group are fixed by tie rods or U-bolts.

[0084] Three middle main beams are arranged at intervals and on both sides of the upper ends of the two lower main beams, and the length of the middle main beam is greater than the width of the two lower main beams. The lengths of the two sides of the same middle main beam 9 located outside the two lower main beams are the same, that is, the lengths of the two sides are equal.

[0085] A radially distributed upper main beam is provided at the upper end of both sides of the three middle main beams, and the distances between adjacent upper main beams of two adjacent pier column groups are the same; the middle and upper main beams are made of double-jointed I-beams I56a welded side by side.

[0086] Or, the intersection part of the lower end of the lower main cross beam and the hoop ear plate and the intersection parts between the lower, middle and upper main cross beams are connected by spot welding to ensure stability.

[0087] (6) Installation of each Bailey beam 16: A number of Bailey beams are arranged side by side between the adjacent upper main cross beams of two adjacent pier column groups, that is, the two lower ends of the Bailey beam are respectively located on the adjacent upper main cross beams of two adjacent pier column groups.

[0088] The Bailey beam is a truss steel beam composed of standard Bailey plates. The 321-type Bailey beam is adopted. The spacing of each group of Bailey trusses is arranged according to the requirements of the drawing. During installation, first connect the Bailey plates with 90 cm or 45 cm shaped window flowers under the bridge, longitudinally assemble to the specified length, and then use a truck crane to lift the assembled Bailey truss to the position of the upper main cross beam determined by measurement and lofting. After all the Bailey beams are installed on the upper main cross beams, the two ends of each Bailey beam are welded to the corresponding upper main cross beam with ∠7.5×5 mm angle steel in a "door" shape.

[0089] (7) Installation of the transverse distribution beam 11: A number of transverse distribution beams are arranged at intervals in the radial direction on the upper ends of each Bailey beam. The I14 and I12.6 I-beams are adopted for the transverse distribution beams. Each transverse distribution beam and the upper end of the corresponding Bailey beam are fixed by U-shaped clamps.

[0090] (8) Construction of the disc buckle support 15: The disc buckle support is provided on the upper end of each transverse distribution beam disc. The outer diameter of the vertical pole of the disc buckle support is 48 mm, and the wall thickness is 3.2 mm. The step distance of the longitudinal and horizontal horizontal bars is 1 m. An adjustable base is provided under each vertical pole of the disc buckle support, and each base can be integrally welded to the upper end of the corresponding transverse distribution beam disc by spot welding. Each vertical pole is vertically arranged. A construction platform 20 is erected on the outer edge part of the top wing plate of the disc buckle support, and a guardrail 21 is provided on the disc buckle support outside the construction platform. The guardrail is used to protect the safety of the construction personnel on the construction platform.

[0091] An adjustable support is provided on the top surface of each vertical pole of the disc buckle support. The cantilever length of the adjustable support extending out of the top layer horizontal bar is less than 650 mm, and the exposed length of the screw rod of each adjustable support is less than 400 mm. The insertion length of the adjustable support into the vertical pole is greater than 150 mm.

[0092] When the disc buckle support is close to the elevation, the surveyors provide a reference point every 5 m circumferentially at the edges of the designed bottom plate and wing plate of the box girder to be cast-in-place for hanging line leveling.

[0093] (9) Construction of the longitudinal distribution beam 14: After the disc buckle support passes the acceptance, the longitudinal distribution beam is laid on the adjustable supports on each vertical pole of the disc buckle support. The I12.6 I-beam is used for the longitudinal distribution beam, and the two can be fixed by spot welding. The spacing between adjacent longitudinal distribution beams is the same as the spacing of the cross bars on the vertical poles.

[0094] (10) Construction of transverse square timber 12: 10×10 cm transverse square timber is laid on the longitudinal distribution beam, with a spacing of 30 cm between adjacent transverse square timbers. After laying, the elevation of the transverse square timber is checked. The low places are aligned with wooden wedges, and the high places are flattened with a flashlight planer. When the elevation of the transverse square timber meets the requirements, preloading can be carried out. After the preloading is qualified, 15 mm bamboo plywood is placed on the transverse square timber as the formwork for the cast-in-place box beam. The longitudinal distribution beam and the transverse square timber are fixed by wire tying, and the bamboo plywood and the transverse square timber are fixed by steel nails.

[0095] The upper main beam, Bailey beam, disc-type bracket, and upper and lower brackets of the construction platform are equipped with a combination ladder for personnel to pass through. The combination ladder is a traditional technology, so it will not be repeated.

[0096] The non-ground support system of the small-radius curved cast-in-place box beam formed by the present invention makes it possible to construct small-radius curved cast-in-place box beams across rivers, lakes, seas, existing roads and other places where ground-type support structures cannot be set up.

[0097] The present invention is applied to the construction of the 1st to 3rd cast-in-place box girders of the H ramp bridge of the LJ-15 contract section of the southern section of the Xi'an Outer Ring Expressway. The application of the present invention effectively solves the problem of difficult support erection in complex geological conditions, and improves the stability of the small-radius curve support through the design of the three-layer main crossbeam. There is no need to reinforce and protect the river channel or relocate it, which saves the cost of foundation replacement and site hardening, improves economic benefits, saves construction time, and successfully passes the once-in-a-century rainy season in Xi'an, and withstands the impact of multiple ultra-large flow floods in the Wangyu River, safely passes the flood season, avoids safety and quality accidents, provides a healthy and good construction environment for construction personnel, and enables the cast-in-place box girder of the bridge to be smoothly constructed.

[0098] Table 1 is a table showing the advantages and disadvantages of the present invention compared with the existing floor-standing bracket:

[0099] Table 1:

[0100]

[0101] Table 1 shows that compared with the prior art ground-based support, the present invention saves 28% of steel, reduces the construction cost (rental fee per joint) by 76%, shortens the construction period by 67%, and can be constructed in areas with small-radius curved cast-in-place box girders across rivers, lakes, and seas where the prior art ground-based support cannot be constructed and where the ground-based support cannot be set up on the ground. The construction conditions are safe and have good economic benefits.

[0102] What is described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An in-situ cast box girder non-ground support system for a small-radius curve, comprising a first to third series of pier columns and upper hoops, characterized in that: Upper hoops and lower hoops are sequentially provided from top to bottom on the same surface of the upper parts of the pier columns of the first to third series of pier columns distributed in a curve radius. A strengthening support structure is provided between the lower ends of each lower hoop and the upper ends of the intermediate beams of the corresponding series of pier columns. The hoop ear plates on both sides of each upper and lower hoop are circumferentially distributed; Two lower main crossbeams are respectively placed on the hoop ear plates on both sides of the same series of pier columns, and the inner sides of the two lower main crossbeams of the same series of pier columns are closely attached to the corresponding pier columns; Three middle main crossbeams are provided on both upper sides and the middle of the upper ends of the two lower main crossbeams, and the middle main crossbeams are circumferentially spaced apart. The length of the middle main crossbeams is greater than the width of the two lower main crossbeams; One upper main crossbeam is provided on both upper sides of the middle main crossbeam in a radial distribution. The distance between the adjacent upper main crossbeams of adjacent series of pier columns is the same; A number of Bailey beams are arranged side by side between the adjacent upper main crossbeams of adjacent series of pier columns. The two ends of each Bailey beam are welded to the upper main crossbeam at the corresponding part with an ∠7.5×5mm angle steel "door"; A number of transverse distribution beams are provided on the upper ends of each Bailey beam in a radial distribution. Each transverse distribution beam and the upper end of the corresponding Bailey beam are fixed by U-shaped clamps; A disc buckle support is provided on the upper end of each transverse distribution beam disc. The outer diameter of the vertical pole of the disc buckle support is 48mm, the wall thickness is 3.2mm, the step distance of the longitudinal and horizontal horizontal bars is 1m. An adjustable base is provided under each vertical pole of the disc buckle support. Each vertical pole is vertically arranged. A construction platform is erected on the outer edge part of the top wing plate of the disc buckle support, and a guardrail is provided on the disc buckle support outside the construction platform; Between the in-situ cast box girder and the top wing plate of the disc buckle support, a bamboo plywood as a formwork, a number of transverse square timbers and longitudinal distribution beams are respectively provided from top to bottom; the strengthening support structure is composed of a strengthening support column, a telescopic column, a support ring, a transverse fixing column, a clamping plate, a clamping groove and a fixing bolt. The strengthening support column and the telescopic column are rectangular columns. The lower part of the strengthening support column is slidably fitted inside the upper part of the telescopic column. Fixed holes are correspondingly provided at intervals on the two side edges of the lower part of the strengthening support column and the two side edges of the upper part of the telescopic column. The fixing bolt is simultaneously located in the horizontally corresponding fixed holes to fix the strengthening support column inside the telescopic column. The lower end of the telescopic column is provided with a clamping plate that can be transversely clamped onto the intermediate beam of the pier column. The upper end of the strengthening support column is provided with a support ring that supports the lower end of one side of the lower hoop. Corresponding clamping grooves are provided at intervals on the corresponding side edges of the adjacent strengthening support columns and telescopic columns. The lower ends of both sides of the transverse fixing column are provided with clamping tongues. The two ends of the transverse fixing column are respectively clamped into the corresponding clamping grooves to fix the distance between the adjacent strengthening support columns and telescopic columns so that the outer sides of the strengthening support column and the telescopic column are abutted against the side surfaces of the corresponding pier columns; the lower end surface of the upper hoop abuts against the upper end surface of the lower hoop; the two lower main crossbeams of the same series of pier columns are fixed by tie rods or U-shaped bolts; the height from the top surface of the upper hoop to the lower end of the in-situ cast box girder is equal to the sum of the thickness of the bamboo plywood, the height of the wooden block, the height of the longitudinal distribution beam, the height of the disc buckle support, the height of the transverse distribution beam, the height of the Bailey beam, the height of the lower main crossbeam, the height of the middle main crossbeam and the height of the upper main crossbeam at the corresponding part.

2. The non-touching support system according to claim 1, characterized in that: The lower main cross beam, the middle main cross beam, and the intersection surface of the upper main cross beam are all connected by spot welding.

3. A construction method of a non-grounded support system for a cast-in-situ box girder with a small-radius curve described in claim 1, characterized in that, It includes the following steps: (1) Preparation stage: Prepare the upper and lower hoop fasteners, bamboo plywood, wooden blocks, longitudinal distribution beams, disc buckle support materials, transverse distribution beams, Bailey beams, lower main cross beams, middle main cross beams, upper main cross beams, U-shaped bolts, tie rods, strengthening support structures, scaffolding components, and combined climbing ladder components for building the non-grounded support system; welding machines, cranes, and their related equipment; (2) Measurement and lofting: Before constructing the non-grounded support system, carry out construction lofting on each pier column of the first to third continuous pier column groups distributed with a small radius curve radius R = 60m, measure the midpoint and column top elevation of two pier columns in the same group, and at the same time calculate the total height of the non-grounded support system and the height supported by each component during the cast-in-place beam construction, which is conducive to adjusting the elevation according to the situation of each component during construction to meet the construction requirements; (3) Construction of upper and lower hoop fasteners: The height of the upper hoop fastener is 900mm, the thickness is 16mm, the length of the hoop ear plate is 350mm, and the thickness is 20mm. Each side of the lower hoop fastener is connected by 24 M30 high-strength bolts; The height of the lower hoop fastener is 350mm, the thickness is 16mm, the length of the hoop ear plate is 350mm, and the thickness is 20mm. Each side of the hoop fastener is connected by 12 M30 high-strength bolts; The lower end face of the lower hoop fastener is supported on the corresponding pier column embedded steel bars, and the embedded steel bars are used as the safety reserve support components of the non-grounded support system; Calculate the construction height between the bottom surface of the cast-in-place box girder and the top surface of the upper hoop fastener according to the total height of the designed non-grounded support system. When positioning the hoop fasteners on each pier column, first subtract the construction height from the non-grounded support system to the top surface of the upper hoop fastener from the designed elevation of the road cast-in-place box girder, which is the top surface elevation of the upper hoop fastener. Use the method of hanging a ruler to lead the ground elevation to the pier column, and mark the top surface elevation line of the upper hoop fastener on the pier column, mark the horizontal position of the upper hoop fastener, and measure it with a spirit level to ensure that the upper hoop fastener is vertically fitted with the pier column to ensure the stable installation of the upper hoop fastener. Before installing the upper hoop fastener, check the bearing capacity of the hoop fastener and remove rust; When installing the hoop fasteners on each pipe column, use a high-altitude platform vehicle to install each hoop fastener at the elevation position, and first preliminarily connect the two hoop fasteners with bolts on the ground. After connecting the hole positions of the hoop fasteners with bolts one by one, put on the nuts. The tightening degree of the nuts is only to screw the nuts until the outer edge of the nut is flush with the screw rod. Then, wedge the square wooden strips into the gaps between the hoop fasteners to temporarily wedge them tightly; then pass the steel wire rope through the bolt holes at the top of the brackets of each hoop fastener for fixing the I-beam, symmetrically pass it through and then hoist the hoop fastener. The hoisting method is to put the hoop fastener on the outside of the pier column from above the pipe column, and use manual labor to assist in positioning at the column top; The hoop ear plates on both sides of each upper and lower hoop fastener are distributed circumferentially. When tightening each hoop fastener, apply pre-tension to each high-strength bolt for tightening the hoop fastener in parallel, that is, evenly screw each bolt on each side to a similar firmness, and observe the joint surface between the hoop fastener and the pier column to prevent the pier column from being subjected to eccentric pressure due to uneven tightening of the high-strength bolts, causing construction hazards; (4)Setting of the strengthening support structure: After the upper and lower hoops are constructed, strengthening support columns and telescopic columns are arranged between the lower end face of the lower hoop on the inner side of the same-connected pier column group and the vertical upper end face of the pier column intermediate beam of the same-connected pier column group. The lower part of the strengthening support column is slidably fitted inside the upper part of the telescopic column. The clamping plate at the lower end of the telescopic column is transversely clamped into the corresponding pier column intermediate beam. The top surface of the support ring at the upper end of the strengthening support column supports against the lower end of the corresponding side of the lower hoop. A number of fixing bolts are inserted into the corresponding fixing holes located horizontally to fix the strengthening support column inside the telescopic column. The two ends of the transverse fixing column are respectively clamped into the corresponding clamping grooves through the clamping tongues to fix the distance between the adjacent strengthening support column and the telescopic column, so that the outer sides of the strengthening support column and the telescopic column are abutted against the corresponding pier column side surface; (5) Installation of each main cross beam: The lower main cross beam, the middle main cross beam and the upper main cross beam are successively installed on the upper end face of the upper hoop. The two lower main cross beams are respectively placed on the hoop ear plates on both sides of the same-connected pier column group. The inner sides of the two lower main cross beams of the same-connected pier column group are closely attached to the corresponding pier columns. The lower main cross beam is a double-spliced I-beam I56a welded together side by side. The two lower main cross beams of the same-connected pier column group are fixed by tie rods or U-bolts; On both sides and in the middle of the upper ends of the two lower main cross beams, there are three middle main cross beams distributed at circumferential intervals. The length of the middle main cross beam is greater than the width of the two lower main cross beams; On both upper ends of the three middle main cross beams, there is one upper main cross beam distributed radially respectively. The distance between the adjacent upper main cross beams of the adjacent two-connected pier column groups is the same; The middle and upper main cross beams are both double-spliced I-beam I56a welded together side by side; Or the intersection part of the lower end of the lower main cross beam and the hoop ear plate and the intersection parts between the lower, middle and upper main cross beams are connected by spot welding to ensure stability; (6) Installation of each Bailey beam: A number of Bailey beams are arranged side by side between the adjacent upper main cross beams of the adjacent two-connected pier column groups. The Bailey beam is a truss steel beam composed of standard Bailey sheets. The spacing of each group of Bailey trusses is arranged according to the drawing requirements. During installation, first connect the Bailey sheets with 90 cm or 45 cm shaped window sashes under the bridge. After longitudinally assembling to the specified length, use a truck-mounted crane to lift the assembled Bailey truss to the position of the upper main cross beam determined by surveying and setting out. After all the Bailey beams are installed on all the upper main cross beams and in place, the two ends of each Bailey beam are welded to the corresponding upper main cross beam with ∠7.5×5 mm angle steel in a "door" shape; (7) Installation of the transverse distribution beam: A number of transverse distribution beams are arranged at radial intervals on the upper ends of each Bailey beam. The transverse distribution beam uses I14 and I12.6 I-beams. Each transverse distribution beam and the upper end of the corresponding Bailey beam are fixed by U-clamps; (8) Construction of the disc buckle type support: The disc buckle type support is arranged on the upper end of each transverse distribution beam disc. The outer diameter of the vertical rod of the disc buckle type support is 48 mm and the wall thickness is 3.2 mm. The step distance of the longitudinal and horizontal horizontal rods is 1 m. An adjustable base is arranged under each vertical rod of the disc buckle type support. Each vertical rod is vertically arranged. A construction platform is erected on the outer edge part of the top wing plate of the disc buckle type support, and a guardrail is arranged on the disc buckle type support outside the construction platform; Adjustable supports are provided on the top surfaces of the vertical poles of the socket and spigot support. The cantilever length of the adjustable support extending out of the top-level horizontal pole is less than 650 mm, and the exposed length of the screw rod of each adjustable support is less than 400 mm. The length of the adjustable support inserted into the vertical pole is greater than 150 mm; When the socket and spigot support approaches the elevation, surveyors provide a reference point every 5 m circumferentially at the edges of the designed bottom plate and wing plate of the box girder to be cast-in-place for leveling by hanging a line; (9) Construction of longitudinal distribution beams: After the socket and spigot support passes the acceptance, longitudinal distribution beams are laid on the adjustable supports on each vertical pole of the socket and spigot support. The longitudinal distribution beams are I12.6 steel I-beams, and the spacing between adjacent longitudinal distribution beams is the same as the spacing of the cross bars on the vertical poles; (10) Construction of transverse square timbers: 10×10 cm transverse square timbers are laid on the longitudinal distribution beams, and the spacing between adjacent transverse square timbers is 30 cm. After laying, the elevation of the transverse square timbers is rechecked. For individual low-lying areas, they are leveled with hand-made wooden wedges, and the high areas are planed with an electric planer. After the elevation of the transverse square timbers meets the requirements, preloading operations can be carried out. After the preloading is qualified, bamboo plywood serving as the formwork for the box girder to be cast-in-place is set on the transverse square timbers.

4. The construction method according to claim 3, characterized in that: The longitudinal distribution beams and the transverse square timbers are fixed by wire binding, and the bamboo plywood and the transverse square timbers are fixed by steel nails.

5. The construction method according to claim 3, characterized in that: The support ring at the upper end of the strengthening support column is arc-shaped, and the radian and thickness of the support ring are the same as those of the lower hoop. A wedge block can be provided between the lower end of the clamping plate at the lower end of the telescopic column and the upper end of the corresponding middle beam of the pier column.

6. The construction method according to claim 3, characterized in that: Combined ladders for personnel passage are provided on the upper and lower supports of the upper main cross beam, Bailey beam, socket and spigot support, and construction platform.

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