Construction method of cast-in-place bridge deck formwork for closure section of hybrid beam single-tower cable-stayed bridge

Abstract

This invention relates to the field of bridge construction technology, and in particular to a method for constructing cast-in-place bridge deck panels for the closure section of a hybrid beam single-tower cable-stayed bridge using suspended formwork. The method includes: two steel support benches at different heights determined by the height difference; several upper crossbeams distributed, with lower crossbeams suspended parallel to each other at the bottom via two tie rod assemblies; several wooden back braces distributed along the extension direction of the lower crossbeams; a lower template laid on the wooden back braces, its upper surface flush with the upper surface of the lower steel crossbeam; rectangular and wedge-shaped back braces laid on one side of the lower template, followed by the upper template. This application achieves stable load-bearing of the lower crossbeams through the horizontal erection of the upper crossbeams; combined with the stepped paving of the horizontal lower template and the upper template with a sloping top, a continuous and smooth transition surface is constructed from the lower steel crossbeam to the higher steel crossbeam, effectively eliminating the problem of misaligned template joints caused by the height difference of the beams. Simultaneously, the uniform load transfer ensures the safety of the pouring process, ultimately achieving high-precision seamless forming of the bridge deck panels for the closure section.

Description

Technical Field

[0001] This invention relates to the field of bridge construction technology, and in particular to a method for constructing cast-in-place bridge deck panels for the closure section of a hybrid beam single-tower cable-stayed bridge using suspended formwork. Background Technology

[0002] In the construction of the closure section of a hybrid beam single-tower cable-stayed bridge, the erection of the cast-in-place formwork system for the bridge deck is a key technical challenge. Due to factors such as construction errors, temperature deformation, and load differences, there is an inevitable height difference between the steel crossbeams on both sides of the closure section.

[0003] Traditional methods primarily address the aforementioned elevation differences by directly laying inclined formwork that matches the elevation difference to the steel beams on both sides. However, due to the angle of inclination, the bottom surface of the inclined formwork cannot simultaneously adhere tightly to the steel beams on both sides, which are at different heights. This can easily lead to suspended grout leakage zones at lower levels and stepped misalignments at higher levels. Furthermore, the suspension support system of the inclined formwork in high-altitude environments carries a relatively higher risk of instability due to uneven load distribution. Additionally, the slope accuracy relies on repeated manual adjustments, which is inefficient and prone to causing concrete grout leakage. Subsequent repairs and chiseling are necessary to maintain the structural integrity. Summary of the Invention

[0004] This invention provides a method for constructing cast-in-place bridge deck panels for the closure section of a hybrid beam single-tower cable-stayed bridge using suspended formwork, which can effectively solve the problems pointed out in the background art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The construction method for the cast-in-place bridge deck of the closure section of a hybrid beam single-tower cable-stayed bridge includes:

[0007] S1: Determine the height difference of the steel crossbeams at the edges of the two bridge sections to be joined, and determine two steel support stools of different heights based on the height difference, so that the two steel support stools can obtain a top surface with the same height after being installed on the corresponding steel crossbeams;

[0008] S2: Several upper crossbeams are distributed along the length of the steel beam. Each upper crossbeam is horizontally supported at both ends by two steel support stools of different heights. Each upper crossbeam is suspended at the bottom by two tie rod assemblies located at both ends by parallel lower crossbeams.

[0009] S3: Several wooden back ribs are distributed along the length direction of the lower crossarm, and the length direction of the wooden back ribs is perpendicular to the length direction of the lower crossarm, and the weight is shared by each of the lower crossarms.

[0010] S4: Lay a lower template on the back rib of the timber, with the upper surface of the lower template flush with the upper surface of the lower steel beam;

[0011] S5: On the upper surface of the lower template located on the side where the high-position steel beam is located, rectangular back ribs and wedge-shaped back ribs are laid, and an upper template is laid on the rectangular back ribs and wedge-shaped back ribs. One end of the upper template is flush with the upper surface of the high-position steel beam under the support of the rectangular back ribs, and transitions to the upper surface of the lower template through a slope. The slope is supported by the wedge-shaped back ribs of different heights.

[0012] Further, step S2 includes:

[0013] S21: Under the bridge, temporary tie rods are used to pass through the middle of the upper and lower crossarms respectively to fix the upper and lower crossarms into a close-fitting and cross-shaped structural module. Two lifting points are selected on the upper and lower crossarms respectively to lift the structural module. The lifting is carried out by a tower crane.

[0014] S22: According to the height difference, temporary pads are laid on the local surface of the lower steel beam, and the upper surface of the temporary pads is flush with the upper surface of the higher steel beam.

[0015] S23: Place both ends of the upper crossarm of the structural module on the flush steel crossbeam and temporary pad respectively, and release the hoisting of the upper crossarm;

[0016] S24: Release the fixation of the temporary tie rod so that the lower crossarm is lowered to a set height by the movement of the temporary tie rod along the axial direction. After being lowered into place, the distance between the upper crossarm and the lower crossarm is locked by the temporary tie rod.

[0017] S25: Release the hoisting of the lower crossarm, rotate the lower crossarm to be parallel to the upper crossarm with the axis of the temporary tie rod as the pivot, fix the upper crossarm and the lower crossarm at both ends respectively through the two tie rod assemblies, and remove the temporary tie rod;

[0018] S26: The two ends of the upper crossbeam are hoisted onto the two steel support stools at different heights using a bridge crane.

[0019] Furthermore, the tie rod assembly is a hydraulic tie rod assembly, comprising:

[0020] The bracket is fixedly installed on the upper surface of the upper crossarm;

[0021] A hydraulic jack is fixedly installed on the upper surface of the bracket.

[0022] The threaded steel tie rod passes through the lower crossarm and the upper crossarm sequentially from bottom to top, and its end extends into the space enclosed by the bracket and the upper crossarm.

[0023] The power output end of the hydraulic jack and the end of the threaded steel rod are connected in the space by a sleeve.

[0024] A strain sensor is provided on the outer surface of the sleeve, and the detection result of the strain sensor is used to guide the power output of the hydraulic jack.

[0025] Furthermore, the power output control of the hydraulic jack includes:

[0026] A1: Construct a BIM model for the closure section construction, inputting the spatial coordinate data of the steel support bench, the layout parameters of the tie rod assembly, and the elastic modulus parameters of the concrete over time. The BIM model is used to predict the strain reference value, which characterizes the expected deformation of the concrete due to creep during the hardening process.

[0027] A2: The tension reference value of the hydraulic jack is set in stages according to the pouring progress, including setting the tension reference value to 1.02 to 1.07 times the design static load tension in the stage before initial setting, and setting the tension reference value to the sum of the design static load tension and the creep compensation tension in the stage from initial setting to final setting, wherein the creep compensation tension is generated according to the strain reference value.

[0028] A3: Control the hydraulic jack to work at the tension reference value, and collect the measured strain data of the strain sensor in real time, and calculate the percentage deviation between the measured strain data and the strain reference value at the corresponding time.

[0029] A4: When the deviation percentage is greater than 6% to 10%, the power output of the hydraulic jack is dynamically adjusted.

[0030] Furthermore, the BIM model calculates the strain reference value based on the spatial coordinate data of the steel support bench, the layout parameters of the tie rod assembly, and the elastic modulus parameters of the concrete over time using the finite element analysis method.

[0031] Furthermore, the predicted strain benchmark value is performed periodically at a preset time interval, which is 10 to 20 minutes.

[0032] Furthermore, the steel support stool is made of three I-beams of equal length welded side by side.

[0033] Furthermore, both the upper crossarm and the lower crossarm are formed by welding two I-beams of equal length side by side.

[0034] Furthermore, the cross-section of the back rib of the timber is I-shaped.

[0035] Furthermore, both the upper and lower templates are made of glued panels.

[0036] The technical solution of this invention can achieve the following technical effects:

[0037] This application employs highly differentiated steel support benches to adapt to the height difference between the two steel crossbeams, ensuring the horizontal erection of the upper crossbeam. A suspension system formed by tie rods then provides stable load-bearing for the lower crossbeam. Combined with the stepped installation of a horizontal lower formwork and a sloping upper formwork, a continuous and smooth transition surface from the lower to the upper steel crossbeam is constructed in one step without the need for additional leveling procedures. This application optimizes the formwork erection process for the closure section of the bridge deck, effectively eliminating the problem of misaligned formwork joints caused by the height difference of the beams. Simultaneously, it ensures the safety of the pouring process through uniform load distribution, ultimately achieving high-precision seamless forming of the closure section of the bridge deck. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a side view of the formwork for the cast-in-place bridge deck of the closure section of a hybrid beam single-tower cable-stayed bridge.

[0040] Figure 2 A top view of the formwork for the cast-in-place bridge deck of the closure section of a hybrid beam single-tower cable-stayed bridge;

[0041] Figure 3 This is a schematic diagram of the hoisting of the structural module;

[0042] Figure 4 This is a schematic diagram showing the transformation of the structural module from its hoisting state to its working state on the steel beams and temporary pads.

[0043] Figure 5 for Figure 4 Enlarged view of a portion of point A in the middle;

[0044] Figure 6 A schematic diagram showing the hoisting of the structural module from the temporary support block to the steel support bench;

[0045] Figure 7 for Figure 6 A magnified view of a section at point B in the middle;

[0046] Figure 8 This is a schematic diagram showing the state of the upper crossarm, lower crossarm, and tie rod assembly at the top of the steel support stool.

[0047] Attached reference numerals: 1. Upper crossbeam; 11. First lifting point; 2. Lower crossbeam; 21. Second lifting point; 3. Temporary tie rod; 4. Steel crossbeam; 5. Temporary pad; 6. First steel support stool; 7. Second steel support stool; 8. Tie rod assembly; 81. Support frame; 82. Hydraulic jack; 83. Threaded steel tie rod; 84. Space; 9. Timber back rib; 10. Lower formwork; 11a. Rectangular back rib; 11b. Wedge-shaped back rib; 12. Upper formwork. Detailed Implementation

[0048] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0049] like Figures 1 to 8 As shown, the construction method for the cast-in-place bridge deck of the closure section of a hybrid beam single-tower cable-stayed bridge includes:

[0050] S1: Determine the height difference of the steel crossbeams 4 at the edges of the two bridge sections to be joined, such as... Figure 1 The height difference H shown is used to determine the different heights of the two steel support stools, such as... Figure 1 The first steel support stool 6, which is lower in height, is shown on the left, and the second steel support stool 7, which is higher in height, is shown on the right, so that the two steel support stools have the same top surface height after being installed on the corresponding steel beams 4.

[0051] S2: As Figure 2 As shown, several upper crossbeams 1 are distributed along the length of the steel beam 4. Each upper crossbeam 1 is horizontally supported at both ends by two steel support stools of different heights. Each upper crossbeam 1 is suspended at the bottom by two tie rod assemblies 8 located at both ends by a lower crossbeam 2 that is set in parallel.

[0052] S3: Several wooden back ribs 9 are distributed along the length direction of the lower crossarm 2. The length direction of the wooden back ribs 9 is perpendicular to the length direction of the lower crossarm 2, and the weight is shared by each lower crossarm 2.

[0053] S4: Lay the lower template 10 on the back rib of the timber 9, as follows Figure 1 As shown, the lower template 10 is a flat plate structure, which fits the top of each timber back rib 9, and the upper surface of the lower template 10 is flush with the upper surface of the lower steel beam 4.

[0054] S5: On the upper surface of the lower template 10 located on the side of the high-position steel beam 4, a rectangular back rib 11a and a wedge-shaped back rib 11b are laid. An upper template 12 is laid on the rectangular back rib 11a and the wedge-shaped back rib 11b. One end of the upper template 12 is flush with the upper surface of the high-position steel beam 4 under the support of the rectangular back rib 11a, and transitions to the upper surface of the lower template 10 through a slope. The slope is supported by wedge-shaped back ribs 11b of different heights. Specifically, the wedge-shaped back ribs 11b are fitted and supported by the upper template 12 through the inclined surface.

[0055] Based on the above suspended formwork structure, after the side formwork is installed, concrete can be poured in the area enclosed by the side formwork, the upper formwork 12 and the lower formwork 10. The installation of the side formwork is existing technology and will not be described in detail here.

[0056] This application employs highly differentiated steel support benches to accommodate the height difference between the two steel crossbeams 4, ensuring the horizontal erection of the upper crossbeam 1. A suspension system formed by tie rods then provides stable load-bearing for the lower crossbeam 2. Combined with the stepped installation of the horizontal lower formwork 10 and the sloping upper formwork 12, a continuous and smooth transition surface from the lower to the upper steel crossbeam 4 is constructed in one step without the need for additional leveling procedures. This application optimizes the formwork erection process for the closure section of the bridge deck, effectively eliminating the problem of misaligned formwork joints caused by the height difference of the beams. Simultaneously, it ensures the safety of the pouring process through uniform load distribution, ultimately achieving high-precision seamless forming of the closure section of the bridge deck.

[0057] During implementation, the lower formwork 10, which is fully laid on the upper surface of each timber back rib 9, forms a continuous supporting base, ensuring uniform load distribution at the bottom of the concrete. The wedge-shaped back ribs 11b set on top of it form a stepped transition system with the upper formwork 12, allowing the upper formwork 12 to naturally connect to the top surface of the higher steel beam 4 and form a precise slope, solving the formwork splicing problem caused by the height difference on both sides of the closure section in one go. The wedge-shaped back ribs 11b in the above structure can pre-form the slope without the need for on-site cutting and adjustment. The full laying of the timber back ribs 9 provides bending resistance. Combined with the shaping of the upper formwork 12 by the wedge-shaped back ribs 11b, it can effectively resist the impact of pouring. The upper formwork 12 and the lower formwork 10 are flush with the top surface of the steel beam 4, which can improve the problem of misalignment and grout leakage.

[0058] As a preferred embodiment of the above, step S2 includes:

[0059] S21: Under the bridge, temporary tie rods 3, passing through the middle of the upper crossarm 1 and the lower crossarm 2 respectively, are used to fix the upper crossarm 1 and the lower crossarm 2 into a fitted and cross-shaped structural module. Two lifting points are selected on the upper crossarm 1 and the lower crossarm 2 respectively for hoisting the structural module, such as... Figure 3 The first lifting point 11 and the second lifting point 21 shown in the figure are used for lifting in this step by a tower crane.

[0060] S22: Based on the height difference, temporary pads 5 are laid on the local surface of the lower steel beam 4. The upper surface of the temporary pads 5 is flush with the upper surface of the higher steel beam 4. In this step, the area where the temporary pads 5 are located forms a temporary working area.

[0061] Steps S21 and S22 above can be performed sequentially or simultaneously, both of which are within the protection scope of this invention;

[0062] S23: Place both ends of the upper crossbeam 1 of the structural module on the flush steel crossbeam 4 and temporary pad 5 respectively, and release the hoisting of the upper crossbeam 1.

[0063] S24: Release the temporary tie rod 3 to allow the lower crossarm 2 to be lowered to the set height by moving along the axial direction through the temporary tie rod 3. After being lowered into place, the distance between the upper crossarm 1 and the lower crossarm 2 is locked by the temporary tie rod 3. In this step, the upper crossarm 1 and the lower crossarm 2 are assembled in the working state in the formed temporary working area. The temporary tie rod 3 acts as a guide structure to ensure that the lower crossarm 2 in the hoisting state is safely and stably lowered relative to the upper crossarm 1 to the set height required for the work. During this process, construction personnel need to assist in releasing the vertical positioning relationship between the upper crossarm 1 and the lower crossarm 2. Specifically, the temporary tie rod 3 can be a precision threaded steel tie rod 83. A locking structure that can be locked in any position is set on the precision threaded steel tie rod 83 to achieve the vertical fixation of the upper crossarm 1 and the lower crossarm 2, as well as the suspension of the lower crossarm 2 relative to the upper crossarm 1 at the set height. In both states, the locking structure applies pressure to the top surface of the upper crossarm 1.

[0064] S25: As Figure 4 and 5 As shown, the hoisting of the lower crossarm 2 is released, and the lower crossarm 2 is rotated around the axis of the temporary tie rod 3 until it is parallel to the upper crossarm 1. The upper crossarm 1 and the lower crossarm 2 are fixed at both ends by the two tie rod assemblies 8, and the temporary tie rod 3 is removed. In this step, the function of the temporary tie rod 3 is changed from the guide structure to a temporary rotating support. After the upper crossarm 1 and the lower crossarm 2 reach the parallel position and are fixed by the tie rod assembly 8, the change of working state is completed.

[0065] S26: Use a bridge crane to hoist both ends of the upper crossbeam 1 onto two steel support benches at different heights. For example... Figures 6 to 8 As shown, once the temporary pads 5 are no longer needed for support, they can be removed one by one.

[0066] In this preferred embodiment, the upper crossarm 1 and lower crossarm 2 are hoisted as a whole through pre-assembled structural modules, effectively reducing the amount of high-altitude assembly work. The cross-shaped structure can ensure the stability of the hoisting, and interference and collision between the lower crossarm 2 and the steel beam 4 can be avoided during the positioning and support of the upper crossarm 1. After the structural modules are hoisted by the tower crane, the bridge deck crane is switched to fine-tune the positioning, which can overcome the limitations of the tower crane's blind spot. The temporary tie rod 3 achieves multi-functionality, including a module fixing structure, a height adjustment guide structure, and a rotating support structure, ultimately achieving the technical effect of improving the construction efficiency and safety factor of the closure section formwork.

[0067] As a preferred embodiment of the above, such as Figure 7 As shown, the tie rod assembly 8 is a hydraulic tie rod assembly 8, including:

[0068] Bracket 81 is fixedly installed on the upper surface of the upper crossarm 1;

[0069] Hydraulic jack 82 is fixedly installed on the upper surface of bracket 81;

[0070] The threaded steel tie rod 83 passes through the lower crossarm 2 and the upper crossarm 1 from bottom to top, and its end extends into the space 84 enclosed by the bracket 81 and the upper crossarm 1.

[0071] The power output end of the hydraulic jack 82 is connected to the end of the threaded steel rod 83 in the space 84 through a sleeve; the lower crossbeam 2 is suspended by the hydraulic jack 82 pulling the threaded steel rod 83.

[0072] A strain sensor is installed on the outer surface of the sleeve, and the detection results of the strain sensor are used to guide the power output of the hydraulic jack 82.

[0073] In this preferred embodiment, the hydraulic jack 82 and the threaded steel tie rod 83 are connected through the space 84 formed by the bracket 81 and the upper crossbeam 1, and strain sensors are installed. The rigid connection between the sleeve and the threaded steel tie rod 83, combined with the strain sensors, provides real-time feedback of the tension value, forming a closed-loop control of detection and execution. The hydraulic jack 82 dynamically adjusts its output force based on the detection data, which can eliminate the overload and underload deviations of traditional manual tensioning and ensure that the formwork system bears a relatively accurate design load throughout the concrete pouring process.

[0074] In this preferred embodiment, the stress deformation of the sleeve can reduce the impact of minor coaxiality deviations on the hydraulic jack 82. The stress changes caused by the coaxiality deviation of the sleeve can be collected before tensioning, and the stress changes during subsequent tensioning are collected accordingly to guide the power output of the hydraulic jack 82. The structure of the sleeve facilitates the multi-directional deployment of strain sensors, thereby achieving omnidirectional balanced acquisition of tension.

[0075] As a preferred embodiment of the above, the power output control of the hydraulic jack 82 includes:

[0076] A1: Construct a BIM model for the closure section construction, input the spatial coordinate data of the steel support bench, the layout parameters of the tie rod assembly, and the elastic modulus parameters of the concrete over time. The BIM model is used to predict the strain reference value, which represents the expected deformation of the concrete due to creep during the hardening process. In this step, a virtual control reference corresponding to the actual construction environment is constructed.

[0077] A2: The reference values ​​for the tension of the hydraulic jack 82 are set in stages according to the pouring progress. This includes setting the reference value for tension before initial setting to 1.02 to 1.07 times the design static load tension, and setting the reference value for tension from initial to final setting to the sum of the design static load tension and the creep compensation tension. The creep compensation tension is generated based on the strain reference value, thereby specifically counteracting long-term creep deformation during the concrete hardening process. Specifically, the creep compensation tension can be converted by multiplying the strain reference value by the concrete elastic modulus and the effective cross-sectional area of ​​the tie rod, and then performing dimensional conversion. Specifically, the strain reference value is a dimensionless strain value, the unit of elastic modulus is MPa, and the unit of tie rod cross-sectional area is mm. 2 After multiplying and converting the units, the creep compensation tensile force can be obtained, with the unit being N.

[0078] A3: Control the hydraulic jack 82 to work at the tension reference value, and collect the measured strain data of the strain sensor in real time, and calculate the percentage deviation between the measured strain data and the strain reference value at the corresponding time.

[0079] A4: When the deviation percentage is greater than 6% to 10%, the power output of the hydraulic jack 82 is dynamically adjusted. This process is controlled in a closed loop, and the output power of the hydraulic jack 82 can be precisely adjusted at different stages for specific working conditions.

[0080] This preferred scheme constructs a BIM model integrating the positioning of steel support benches, the layout of tie rods, and the time-varying characteristics of concrete. It generates strain benchmark values ​​characterizing creep deformation in real time according to the predicted frequency. Before initial setting, an over-tensioning strategy of 1.02 to 1.07 times the design static load is used to actively offset instantaneous settlement. After initial setting, the strain benchmark values ​​are automatically converted into creep compensation tension and superimposed on the design load to precisely combat concrete hardening creep. The output of the hydraulic jack is dynamically adjusted based on the percentage deviation between the strain sensor measured data and the corresponding strain benchmark values, forming a closed loop of prediction, monitoring, and execution. This upgrades the traditional passive response to active suppression during the creep deformation stage. Furthermore, it eliminates manual calculation errors through automatic conversion of physical parameters, improving load control accuracy. Ultimately, it adapts to different materials and working conditions, increasing response speed and ensuring that the closure section formwork system can withstand the precise design load throughout the entire pouring cycle.

[0081] As a preferred embodiment, the BIM model calculates the strain benchmark value based on the coordinate data of the steel support bench space 84, the layout parameters of the tie rod assembly 8, and the time-varying elastic modulus parameters of the concrete using the finite element analysis method. In this preferred embodiment, the finite element analysis method can accurately simulate the steel support bench structure, the layout of the tie rod space 84, and the time-varying characteristics of the concrete elastic modulus, transforming physical construction parameters into a digital prediction model. This ensures the engineering mechanics accuracy of the strain benchmark value calculation and improves the accuracy of creep deformation prediction. In a further preferred implementation, the predicted strain benchmark value is executed periodically at a preset time interval, which is 10 to 20 minutes. This matches the hardening rate change from the initial setting to the final setting stage of the concrete, achieving real-time synchronization between the hydraulic compensation system and the evolution of material properties, avoiding deformation control deviations caused by prediction lag. Preferably, a time interval of 13 to 17 minutes can be selected.

[0082] As a preferred embodiment of the above, the steel support bench is made of three I-beams of equal length welded side by side, thereby forming a composite load-bearing structure with uniformly distributed force. This allows the local load to be distributed and transferred to the steel beam 4, eliminating the risk of stress concentration caused by a single I-beam bearing the load, improving the overall stability of the support system, and facilitating processing and use. The length of the I-beams in the steel support bench can be selected according to actual needs. In specific use, it is preferred to use the cross-section of the I-beam as the support surface.

[0083] As a preferred embodiment of the above implementation, both the upper crossbeam 1 and the lower crossbeam 2 are formed by welding two I-beams of equal length side by side, see [reference]. Figure 3 Similarly, the required structural form can be obtained using readily available I-beams, which also have sufficient structural strength.

[0084] Of course, the above method of obtaining structural units by welding I-beams is only a preferred embodiment, and other structural forms are also within the protection scope of this invention.

[0085] As a preferred embodiment, the cross-section of the timber back rib 9 is I-shaped. During use, it can preferably be fixed to the lower crossbeam 2 using wire. The cross-sectional characteristics of the I-shaped timber back rib 9 provide bidirectional bending resistance. Combined with the flexible wire fixing method, this ensures a tight fit between the back rib and the lower crossbeam 2 while allowing for slight temperature deformation, avoiding cracking of the glued panel caused by a rigid connection. During implementation, the rectangular back rib 11a and the wedge-shaped back rib 11b need to be specifically set according to the structural form of the upper template 12, including adjusting the number of ribs and adjusting the angle of the wedge-shaped back rib 11b relative to the supporting slope of the upper template 12, specifically to ensure stable support for the upper template 12.

[0086] As a preferred embodiment of the above, both the upper template 12 and the lower template 10 are made of plywood panels. The laminated structure of the plywood panels gives the templates high flatness and elastic recovery ability. Specifically, in this preferred embodiment, the lower template 10 mainly resists the impact of pouring, while the upper template 12 mainly adapts to the height difference shape. The two templates work together to achieve the required flatness of the concrete forming surface.

[0087] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for constructing cast-in-place bridge deck panels for the closure section of a hybrid beam single-tower cable-stayed bridge using suspended formwork, characterized in that... include: S1: Determine the height difference of the steel beams at the edges of the two bridge sections to be joined, and determine two steel support stools of different heights based on the height difference, so that the two steel support stools can obtain a top surface with the same height after being installed on the corresponding steel beams; S2: Several upper crossbeams are distributed along the length of the steel beam. Each upper crossbeam is horizontally supported at both ends by two steel support stools of different heights. Each upper crossbeam has a lower crossbeam suspended at the bottom by two tie rod assemblies located at both ends. S3: Several wooden back ribs are distributed along the length direction on the lower crossarm, the length direction of the wooden back ribs is perpendicular to the length direction of the lower crossarm, and the weight is shared by each of the lower crossarms. S4: Lay a lower template on the back rib of the timber, with the upper surface of the lower template flush with the upper surface of the lower steel beam; S5: On the upper surface of the lower template located on the side where the high-position steel beam is located, rectangular back ribs and wedge-shaped back ribs are laid, and an upper template is laid on the rectangular back ribs and wedge-shaped back ribs. One end of the upper template is flush with the upper surface of the high-position steel beam under the support of the rectangular back ribs, and transitions to the upper surface of the lower template through a slope. The slope is supported by the wedge-shaped back ribs of different heights.

2. The method for constructing the cast-in-place bridge deck of the closure section of a hybrid beam single-tower cable-stayed bridge according to claim 1, characterized in that, Step S2 includes: S21: Under the bridge, temporary tie rods are used to pass through the middle of the upper and lower crossarms respectively to fix the upper and lower crossarms into a close-fitting and cross-shaped structural module. Two lifting points are selected on the upper and lower crossarms respectively to lift the structural module. The lifting is carried out by a tower crane. S22: According to the height difference, temporary pads are laid on the local surface of the lower steel beam, and the upper surface of the temporary pads is flush with the upper surface of the higher steel beam. S23: Place both ends of the upper crossarm of the structural module on the flush steel crossbeam and temporary pad respectively, and release the hoisting of the upper crossarm; S24: Release the fixation of the temporary tie rod, and lower the lower crossarm to a set height along the axis of the temporary tie rod. After it is lowered into place, lock the distance between the upper and lower crossarms by the temporary tie rod. S25: Release the hoisting of the lower crossarm, rotate the lower crossarm to be parallel to the upper crossarm with the axis of the temporary tie rod as the pivot, fix the upper crossarm and the lower crossarm at both ends respectively through the two tie rod assemblies, and remove the temporary tie rod; S26: The two ends of the upper crossbeam are hoisted onto the two steel support stools at different heights using a bridge crane.

3. The method for constructing the cast-in-place bridge deck of the closure section of a hybrid beam single-tower cable-stayed bridge according to claim 1 or 2, characterized in that, The tie rod assembly is a hydraulic tie rod assembly, comprising: The bracket is fixedly installed on the upper surface of the upper crossarm; A hydraulic jack is fixedly installed on the upper surface of the bracket. The threaded steel tie rod passes through the lower crossarm and the upper crossarm sequentially from bottom to top, and its end extends into the space enclosed by the bracket and the upper crossarm. The power output end of the hydraulic jack and the end of the threaded steel rod are connected in the space by a sleeve. A strain sensor is provided on the outer surface of the sleeve, and the detection result of the strain sensor is used to guide the power output of the hydraulic jack.

4. The method for constructing the cast-in-place bridge deck of the closure section of a hybrid beam single-tower cable-stayed bridge according to claim 3, characterized in that, The power output control of the hydraulic jack includes: A1: Construct a BIM model for the closure section construction, inputting the spatial coordinate data of the steel support bench, the layout parameters of the tie rod assembly, and the elastic modulus parameters of the concrete over time. The BIM model is used to predict the strain reference value, which characterizes the expected deformation of the concrete due to creep during the hardening process. A2: The tension reference value of the hydraulic jack is set in stages according to the pouring progress, including setting the tension reference value to 1.02 to 1.07 times the design static load tension in the stage before initial setting, and setting the tension reference value to the sum of the design static load tension and the creep compensation tension in the stage from initial setting to final setting, wherein the creep compensation tension is generated according to the strain reference value. A3: Control the hydraulic jack to work at the tension reference value, and collect the measured strain data of the strain sensor in real time, and calculate the percentage deviation between the measured strain data and the strain reference value at the corresponding time. A4: When the deviation percentage is greater than the set value, the power output of the hydraulic jack is dynamically adjusted. The set value is selected from 6% to 10%.

5. The method for constructing the cast-in-place bridge deck of the closure section of a hybrid beam single-tower cable-stayed bridge according to claim 4, characterized in that, The BIM model calculates the strain reference value based on the spatial coordinate data of the steel support bench, the layout parameters of the tie rod assembly, and the elastic modulus parameters of the concrete over time using the finite element analysis method.

6. The method for constructing the cast-in-place bridge deck of the closure section of a hybrid beam single-tower cable-stayed bridge according to claim 4 or 5, characterized in that, The strain benchmark value is predicted periodically at a preset time interval, which is 10 to 20 minutes.

7. The method for constructing the cast-in-place bridge deck of the closure section of a hybrid beam single-tower cable-stayed bridge according to claim 1, characterized in that, The steel support stool is made of three I-beams of equal length welded side by side.

8. The method for constructing the cast-in-place bridge deck of the closure section of a hybrid beam single-tower cable-stayed bridge according to claim 1, characterized in that, Both the upper crossarm and the lower crossarm are made of two I-beams of equal length welded side by side.

9. The method for constructing the cast-in-place bridge deck of the closure section of a hybrid beam single-tower cable-stayed bridge according to claim 1, characterized in that, The cross-section of the back rib of the timber is I-shaped.

10. The method for constructing the cast-in-place bridge deck of the closure section of a hybrid beam single-tower cable-stayed bridge according to claim 1, characterized in that, Both the upper and lower templates are made of plywood.

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