Bridge V-shaped pier top box girder formwork supporting construction method

Abstract

The invention discloses a bridge V-shaped pier top box girder formwork supporting construction method, and belongs to the technical field of bridge construction. According to the method, a three-dimensional BIM model covering a V-shaped pier top supporting system and a box girder structure is established, finite element analysis and intelligent algorithm presetting are combined, and collision detection and load simulation optimization before construction are achieved; an embedded part is accurately positioned through digital lofting, a composite supporting platform and an adjustable curved surface formwork system are built, data are collected in real time through a fiber grating sensor and a tilt angle sensor, deformation of a supporting system is corrected in combination with a dynamic regulation and control mechanism, and finally formwork dismantling and material recycling are completed. According to the method, the supporting problem of the V-shaped pier special-shaped space and the concrete anti-cracking control problem are effectively solved, the construction precision, efficiency and safety are improved, the cost is reduced, and the method is suitable for box girder formwork supporting construction under the special-shaped space structures such as V-shaped piers and Y-shaped piers.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bridge construction, in particular to a bridge V-shaped pier pier top box girder formwork support construction method, especially suitable for bridge engineering projects that perform box girder formwork support construction on the pier top of V-shaped piers, aiming to solve key problems such as precision control, structural stability, and construction safety during the construction process of box girder formwork support on the pier top of V-shaped piers, and improve construction quality and efficiency. BACKGROUND

[0002] In traditional bridge V-shaped pier pier top box girder formwork support construction, many difficult problems are faced. First, in the support system construction stage, due to the lack of effective pre-planning and simulation means, the spatial arrangement of triangular support frames, Bailey beam main beams, and steel distribution beams can only be arranged on site relying on the experience of construction personnel. This leads to frequent node conflicts between embedded parts and pier reinforcement, prestressed pipes, and makes it difficult to discover and solve them in time before construction. For example, in a certain bridge construction project, due to the conflict between the positions of embedded parts and pier reinforcement, the reinforcement had to be bent or repositioned during the construction process, which not only consumed a lot of manpower, material resources, and time, but also weakened the overall strength and stability of the structure, creating safety hazards for subsequent construction. Support system deformation control is also a big problem. The traditional construction method mainly relies on empirical formulas and simple preloading tests to estimate the deformation of the support system, which cannot accurately simulate the complex and variable load distribution of the box girder at different construction stages. In actual construction, as the box girder concrete is poured, the load increases and is unevenly distributed, making it difficult to accurately grasp the deformation of the support system. When the deformation exceeds expectations, it may cause size deviations and appearance quality defects of the box girder, and in severe cases, even cause formwork collapse accidents, endangering the safety of construction personnel. Like some large-span bridges, the support system deformed too much during construction, causing cracks in the box girder, which had to be repaired and reinforced at a great cost, delaying the construction period. Furthermore, the precision of the setting-out and installation stages in traditional construction is low. Using conventional measuring tools for setting-out cannot meet the high-precision construction requirements of modern bridges, resulting in large setting-out errors, which cause deviations in the installation positions of embedded parts, support platform contour lines, and key observation points. This not only affects the installation quality of the support system, but also has a chain reaction on the precision of subsequent box girder formwork installation and concrete pouring, reducing the overall quality and service life of the bridge. In terms of formwork installation, the traditional fixed square wood support method has poor flexibility and cannot be accurately adjusted according to the design requirements of the complex curved surface of the box girder bottom plate, resulting in poor box girder bottom plate forming quality and affecting the stress performance of the bridge.

[0003] With the vigorous development of bridge construction, the scale and difficulty of bridges are rising. The number of large-span and high-pier bridges is increasing, which puts forward more stringent requirements on construction technology. The traditional construction method of V-shaped pier top box girder formwork support has been unable to meet the needs of current bridge construction in safety, quality and progress and other aspects. In terms of safety, the number of uncertain factors in the construction process increases, and once the support system fails, it will cause serious safety accidents and huge casualties and property losses. Therefore, a more reliable and stable support system construction technology is needed to ensure the safety of the construction process. In terms of quality, modern bridges have high requirements for the durability, carrying capacity and appearance quality of the structure, and the traditional construction method is difficult to guarantee high-precision construction and cannot meet the standards of high-quality bridge construction. In terms of progress, large-scale bridge construction has a long construction period and high cost, and any delay may cause huge economic losses. The traditional construction method has many problems, resulting in frequent rework and rectification during construction, which seriously affects the construction progress. Therefore, the industry urgently needs a more advanced, efficient and precise construction technology to solve the drawbacks of traditional construction methods using digital and intelligent means to improve construction safety, ensure construction quality and speed up construction progress. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the existing bridge V-shaped pier top box girder formwork support construction method, and to realize the digitization, intelligentization and high precision of the bridge V-shaped pier top box girder formwork support construction by introducing digital twinning and intelligent control technology. Using advanced digital modeling and intelligent algorithms, the problems of spatial arrangement conflict and deformation control difficulty in traditional construction are solved; with the help of digital precision lofting and precise embedded part installation, the construction precision is improved; the composite support platform is built and the adjustable curved formwork system is used to ensure the stability of the formwork support and the precise forming of the box girder curved surface; through intelligent monitoring and dynamic control, the construction state is mastered in real time, and the risks such as support subsidence are actively responded, so as to comprehensively improve the construction efficiency and quality, ensure the construction safety and reduce the construction cost.

[0005] In order to achieve the above purpose, the present application provides a bridge V-shaped pier top box girder formwork support construction method, comprising the following steps: S1, construction preparation: in the construction preparation stage, a three-dimensional BIM model covering the V-shaped pier top support system and the box girder structure is established; the spatial arrangement collision detection of the triangular support frame, the main beam of the Bailey beam and the profiled steel distribution beam is carried out by using the three-dimensional BIM model; the node conflicts of embedded parts and pier body reinforcement, prestressed pipe are identified and solved; the load distribution of the box girder pouring in different construction stages is simulated by finite element analysis, and the matrix arrangement density of the anchoring reinforcement and the welding node design of the triangular support frame are optimized based on the simulation results; combined with historical pretest data, a support system deformation prediction algorithm is established in the three-dimensional BIM model; S2, line positioning: the design coordinates in the three-dimensional BIM model are imported into the GPS-RTK measuring instrument and the total station, and the digital lofting is carried out on the V-shaped pier top, and the embedded part installation position, the support platform contour line and the key observation point position are marked; S3, embedded part installation: based on the lofting result of S2, high-strength connecting parts are embedded in the V-shaped pier; S4, support platform construction: the high-strength connecting part includes a pre-embedded steel plate, a triangular support frame designed by S1 is welded on the pre-embedded steel plate to form a cast-in-place support platform; the main beam of the Bailey beam is erected in the longitudinal direction on the cast-in-place support platform, and the distribution beam is erected in the transverse direction above the main beam of the Bailey beam; S5, support form construction: an adjustable height screw rod support system is arranged on the distribution beam, which is composed of matrix arranged adjusting screw rods; a shaped steel plate is laid on the top of the adjusting screw rod to form a box girder bottom mold bearing surface; according to the design elevation and curve data in the three-dimensional BIM model, the top height of the adjusting screw rod is adjusted to make the shaped steel plate form the complex curved surface of the box girder bottom plate; S6, monitoring: fiber bragg grating sensors and inclination sensors are arranged at the key observation points set in S2, the triangular support frame and the middle part of the main beam of the Bailey beam; based on the deformation prediction algorithm preset by S1, inverse analysis is carried out combined with real-time data acquisition to predict the deformation trend of the support system; according to the deformation trend, instructions are sent to the screw rod support system to adjust the top elevation of the adjusting screw rod in the specified area to correct the reserved camber of the formwork.

[0006] Further, in the step S3, the pre-embedded steel plate is configured with multiple ribbed steel bars arranged by S1 as anchoring reinforcement, the end of the anchoring reinforcement is connected through a mechanical threaded sleeve, and the epoxy interface agent is brushed before the implantation of concrete; the reserved fine rolled threaded steel bars are simultaneously positioned according to the three-dimensional BIM model, and the fine rolled threaded steel bars are penetrated.

[0007] Further, in the step S4, the main beam of the Bailey beam is arranged in a single layer and double row; the distribution beam is a profiled steel structure formed by double channel steel butt welding, and is hinged with the main beam of the Bailey beam through a steel pin to form an orthogonal grid support system.

[0008] Further, in step S6, the fiber grating sensor collects stress and strain data of the support platform, and the tilt angle sensor monitors the micro-tilt deformation of the triangular support frame; the collected data is sent to the background terminal through the wireless transmission module, and the background terminal sets a warning threshold and automatically alarms when the monitoring value approaches the threshold.

[0009] Further, in step S1, when optimizing the welding node design of the triangular support frame, the optimization basis includes an empirical formula based on the results of finite element analysis: the total length of the weld satisfies: .

[0010] is the maximum load of the welding node obtained by finite element analysis, with units of N; is the weld size, with units of mm, is the allowable shear stress of the weld, with units of MPa. The traditional method of relying on engineering experience or conservative estimation is abandoned, and a precise scientific calculation basis is provided for the welding node design. Through finite element analysis, the node load under the most unfavorable working condition is obtained, and then the weld size and the material strength are used to accurately calculate the required weld length , thereby eliminating the risk of node failure due to insufficient weld strength from the source. Potential safety hazards can be predicted and solved through simulation and calculation before construction, greatly reducing the probability of collapse accidents caused by support frame welding node damage during concrete pouring, and ensuring the safety of construction personnel and the structure itself. Traditional experience design often uses a large safety factor for safety considerations, resulting in material waste. This formula can determine the most economical weld size and length under the premise of safety, avoiding unnecessary material waste and welding time, and achieving cost reduction and efficiency improvement.

[0011] Further, in step S1, when optimizing the matrix arrangement density of the anchoring steel bar, the optimization basis includes an empirical formula based on the results of finite element analysis: the required number of anchoring steel bars satisfies: , is the maximum tensile stress (MPa) of the embedded steel plate obtained by finite element analysis, is the area of the embedded steel plate, with units of mm 2 ; is the diameter of the steel bar, with units of mm; is the anchoring length, with units of mm; is the bond strength between concrete and steel bar, with units of MPa; Safety factor. Traditional design relies on the construction requirements in the specification or the conservative experience of engineers, which may result in excessive or insufficient safety margin. The formula is based on the actual stress distribution obtained by finite element analysis, and the precise and stress-demand-oriented reinforcement design is carried out, so that the design decision is from fuzzy to precise. Through quantitative calculation, it is ensured that the bearing capacity (provided by the root reinforcement) of the anchoring system is sufficient to resist the maximum tension force transmitted from the box girder to the embedded steel plate. This eliminates the risk of catastrophic accidents such as embedded part pulling out and overall support system instability caused by insufficient anchoring reinforcement from the design source, greatly improving the structural safety during construction. The stress distribution on the embedded steel plate is extremely uneven due to the complex stress of V-shaped pier structure. The introduction of the formula enables the design to determine the total amount of reinforcement and guide the matrix arrangement based on the real and non-uniform stress field, effectively solving the core problem of anchoring design for special-shaped space structures. In projects with smaller stress, the amount of reinforcement required may be less than that of traditional experience allocation through precise calculation. This avoids unnecessary material waste and construction complexity, and achieves cost reduction and efficiency improvement. Precise design is completed through digital means during the construction preparation stage, avoiding huge economic losses and time delays caused by embedded part anchoring problems such as rework, reinforcement, and even demolition after concrete pouring, ensuring construction progress and improving project management level.

[0012] Further, the embedded steel plate is a rectangular steel plate with a size of 700mm×700mm and a thickness of 15mm, the four edges of the embedded steel plate are chamfered, the surface is sandblasted and rusted, and then an epoxy zinc-rich primer with a dry film thickness of 80μm is brushed; the fine rolled threaded steel is PSB930 type with a diameter of 25mm, and 3 fine rolled threaded steels are reserved on each side of a single span for pull-through hole, with a horizontal spacing of 4.5m; the fine rolled threaded steel penetrates into the corrugated pipe, the corrugated pipe is 10-20cm shorter than the fine rolled threaded steel at both ends, and the corrugated pipe is fixed with a spiral rib outside, and the spiral rib is screwed into a matching backing plate and nut at both ends.

[0013] Further, the triangular support frame in S4 is formed by double-sided welding of 4 rows of 10mm thick triangular steel plates and 400mm×700mm 10mm thick rectangular steel plates, and the triangular steel plates are welded and fixed with the embedded steel plate.

[0014] Further, the thickness of the shaped steel plate in S5 is not less than 10mm, the adjustment accuracy of the adjustment screw is controlled within ±0.5mm, and the layout spacing of the screw support system is encrypted to 0.15m in the box girder solid web area and 0.3m in the remaining area.

[0015] Further, the stress collection accuracy of the fiber Bragg grating sensor in S6 is not less than 0.1MPa, and the angle measurement accuracy of the inclination sensor is not less than 0.01°.

[0016] Advantages of the present application: (1) Early simulation of conflict avoidance, reduce construction deviation: By establishing a three-dimensional BIM model covering the V-shaped pier top support system and the box girder structure, the spatial arrangement collision detection of the triangular support frame, the beam of the Bailey beam and the profiled steel distribution beam is carried out in advance, and the node conflict of the embedded part and the pier body reinforcement, the prestressed pipe is accurately identified and solved. Compared with the traditional method of relying on experience and on-site adjustment, the bending of the reinforcement and the rework of the embedded part caused by the conflict in the construction are avoided, the deviation is controlled from the source, and the spatial position precision of the support system and the box girder structure is ensured.

[0017] (2) Digital lofting and adjustable template, realize accurate forming of curved surface: The three-dimensional BIM model design coordinates are imported into the GPS-RTK measuring instrument and the total station, the lofting error is controlled within ±3mm, and the embedded part installation, the support platform contour and the key observation point positioning are accurately ensured; In the construction of the support template, through the adjustment screw rod arranged in matrix, combined with the elevation and curve data of the BIM model design, the height of the profiled steel plate is accurately adjusted, the complex curved surface of the box girder bottom plate is perfectly formed, the problem of traditional fixed square wood support cannot adapt to special-shaped curved surface and poor forming quality is solved, and the size precision and appearance quality of the box girder structure are ensured.

[0018] (3) The support system deformation prediction algorithm based on finite element analysis, combined with the real-time data of the fiber grating sensor and the inclination sensor, inversely analyzes the deformation trend and dynamically adjusts the elevation of the adjustment screw rod, corrects the reserved camber of the template, actively offsets the support sinking caused by the uneven tension on both sides of the V-shaped pier, avoids the size deviation and appearance defects caused by the support deformation after the concrete pouring (4) Through the finite element analysis simulation of the load distribution of the box girder at different stages of pouring, the matrix arrangement density of the anchoring steel and the welding node design of the triangular support frame are optimized, the overdesign or underdesign caused by the traditional experience design is avoided, the bearing safety of the support system under the conditions of concrete dead weight, vibrating load, prestressed tension and other working conditions is ensured, and the risk of support instability is eliminated. The anchoring steel is accurately calculated according to the stress distribution, and the length of the triangular support frame welding seam is accurately designed according to the formula, so as to avoid the waste of steel caused by excessive reinforcement and excessive welding; The adjustable screw rod and the profiled steel plate can be recycled and reused, reducing the material loss rate. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is the bridge V-shaped pier top box girder template support construction method construction process flow chart of the present application.

[0020] Figure 2 is the V-shaped pier box girder construction platform along the bridge arrangement drawing.

[0021] Figure 3 is the embedded steel plate installation schematic diagram.

[0022] Figure 4 is a large drawing of a V-shaped pier pre-buried high-strength connecting piece. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. In the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work are within the scope of protection of the present application.

[0024] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement condition, etc. between components in a certain posture, and if the certain posture changes, the directional indications also change accordingly.

[0025] In addition, if the embodiments of the present application involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first" and "second" can explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing throughout the text includes three parallel schemes. Taking "A and / or B" as an example, it includes A scheme, or B scheme, or A and B schemes. In addition, "multiple" means two or more. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person of ordinary skill in the art can realize it. When the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist, and is not within the scope of protection claimed by the present application.

[0026] Referring to Figures 1-4 As shown in the drawings, the present application discloses a bridge V-shaped pier top box girder formwork support construction method, comprising the following steps: Step 1, construction preparation stage In the construction preparation stage, a professional BIM modeling software such as Revit is used to establish a three-dimensional BIM model covering the V-shaped pier top support system and the box girder structure. The model not only contains the geometric shape, size, etc. of the support system and the box girder, but also integrates material properties, construction technology, etc. data, forming a complete digital information model. This model is used to perform collision detection. The software's collision detection function simulates and analyzes the spatial arrangement of the triangular support frame, Bailey bridge main beam, and steel distribution beam, identifying and resolving node conflicts between embedded parts and pier reinforcement and prestressed ducts in advance. When a conflict is detected, the software visually displays the location and type of the conflict, allowing construction personnel to adjust the layout of the support system promptly and avoid rework during actual construction. Finite element analysis software, such as ANSYS, was used to simulate the load distribution at different construction stages of the box girder casting. An accurate finite element model was established in the software, considering various factors such as the self-weight of the concrete during casting, vibration loads, and loads from construction personnel and equipment. The simulation yielded the stress and strain distribution of various parts of the support system at different construction stages. Based on the simulation results, the matrix arrangement density of the anchoring reinforcement was optimized. The number of anchoring reinforcement bars was increased or decreased appropriately according to the stress magnitude at different locations to ensure effective anchoring. Simultaneously, the design of the welded joints of the triangular support frame was optimized. By simulating the stress concentration at the welded joints under different stress conditions, the welding process and joint structure were improved to enhance the load-bearing capacity and reliability of the joints.

[0027] By combining historical preloading test data, a predictive algorithm for forecasting the deformation of the support system is established within the model. During the preloading test, deformation data and corresponding load data are collected at different locations of the support system. Data analysis methods, such as multiple linear regression analysis and neural network algorithms, are used to establish a mathematical relationship model between load and deformation. This model is then embedded into a 3D BIM model to form a deformation prediction algorithm, providing a basis for deformation prediction during subsequent construction.

[0028] Step 2, Laying out and positioning lines The design coordinates from the 3D BIM model were directly imported into the GPS-RTK surveying instrument and total station. Before importing the coordinate data, the surveying instruments were calibrated and their accuracy checked to ensure their accuracy. When digitally laying out the top of the V-shaped pier, the surveyors accurately marked the installation positions of the embedded parts, the outline of the support platform, and the positions of key observation points on site according to the instrument prompts. The real-time dynamic positioning function of the GPS-RTK surveying instrument can quickly determine the approximate location. Then, a total station is used for precise measurement and positioning, improving the layout error control accuracy to within ±3mm. This high-precision layout ensures accurate installation of subsequent embedded parts and support system construction, avoiding problems such as unstable support system installation and insufficient accuracy of box girder formwork installation caused by positional deviations, thus ensuring the smooth progress of the entire construction process.

[0029] Step 3, Installation of embedded parts Based on the results of digital precision layout, high-strength connectors are pre-embedded inside the V-shaped pier. (See [reference]) Figure 3The embedded steel plate in the connecting piece uses multiple ribbed steel bars arranged optimally as anchoring steel bars. These anchoring steel bars are arranged in a matrix according to the stress conditions obtained through finite element analysis, and the steel bar density is increased in areas with greater stress to improve the anchoring force between the embedded steel plate and the concrete. The embedded steel plate is a 700mm x 700mm rectangular steel plate with chamfered edges (R5mm), and after sandblasting and rust removal on the surface, an 80μm thick epoxy zinc-rich primer is applied. 2 The steel bar model is HRB400, the steel bar diameter d = 25mm, the anchoring length = 400mm, for ribbed steel bars (HRB400) and C40 and above concrete, refer to the Code for Design of Concrete Structures, take = 2.5MPa, considering load uncertainty and long-term durability, take = 1.6, through finite element analysis to simulate box girder pouring construction, the maximum tensile stress of the embedded steel plate = 2.2MPa, this value is based on the typical V-pier load working condition, and in actual engineering, it needs to be determined according to the specific model, and the optimization basis includes the empirical formula based on the finite element analysis results: the number of anchoring steel bars required satisfies: , is the maximum tensile stress of the embedded steel plate (MPa) obtained through finite element analysis, is the area of the embedded steel plate, with the unit of mm 2 ; is the steel bar diameter, with the unit of mm; is the anchoring length, with the unit of mm; is the bond strength between concrete and steel bar, with the unit of MPa; is the safety factor.

[0030] Substitute the parameter values to calculate Since the number of steel bars must be an integer, and ≥ 8.57, take = 9 to meet the requirements.

[0031] See Figure 4Nine HRB400 Φ25mm ribbed steel bars are arranged in a 3×3 matrix (center-to-center distance 200mm) for anchoring reinforcement. The anchoring length is 400mm, and the ends are connected with mechanical threaded sleeves (compliant with GB / T 1499.2 standard). Epoxy interface agent (model J-302) is applied before implantation into the concrete. Three PSB930 Φ25mm precision threaded steel bar tie rod insertion holes are reserved (lateral spacing 4.5m). The precision threaded steel bars are inserted into Φ50mm corrugated pipes (15cm shorter than the steel bars at both ends). Φ8mm spiral reinforcement (300mm in length) is fixed to the outside of the corrugated pipes, and 10mm thick washers and M25 nuts are screwed into both ends of the spiral reinforcement. The ends of the reinforcing bars are connected using mechanical threaded sleeves, a method that offers advantages such as reliable connection and ease of construction. Before connection, the ends of the reinforcing bars are ground and cleaned to ensure connection quality. Before embedding in concrete, an epoxy bonding agent is applied to the surface of the reinforcing bars. This agent enhances the bond between the reinforcing bars and concrete, prevents corrosion, and improves the durability of the structure. Simultaneously, pre-drill holes for inserting the precision-rolled threaded steel bars are positioned according to the model. When pre-drilling these holes, the position, diameter, and perpendicularity are strictly controlled to ensure smooth insertion of the threaded steel bars. After insertion, the threaded steel bars are tensioned and anchored, utilizing their high strength to enhance the stability of the support system.

[0032] Step 4, Construction of the support platform An optimized triangular support frame is welded onto the pre-embedded steel plate. The specifications of the triangular support frame are as follows: it uses four rows of 10mm thick triangular steel plates welded to 400mm×700mm rectangular steel plates on both sides. The design of the welding nodes is optimized based on finite element analysis results and empirical formulas. .

[0033] This represents the maximum load on the welded joint obtained from the finite element analysis, in N. Weld dimensions, in mm. This represents the allowable shear stress of the weld, expressed in MPa.

[0034] Finite element analysis simulation yielded a maximum load of 500 kN on the welded joint; the design adopted the weld size... =8 mm, allowable shear stress in weld Take 160 MPa. Calculate the required total weld length using empirical formulas. : = 500,000 / (1.414 × 8 × 160) ≈ 276 mm. In this embodiment, the triangular support frame is welded by 4 rows of steel plates on both sides, and the actual total weld length provided is much larger than this calculated value, ensuring the safety and reliability of the node. Before welding, the quality of the material of the triangular support frame is inspected to ensure that the material meets the design requirements. During welding, the welding process parameters such as welding current, voltage, and welding speed are strictly controlled to ensure the welding quality. The triangular support frame forms the basic structure of the cast-in-place support platform, providing stable support for subsequent erection.

[0035] The main girder is erected on the platform in the bridge direction, and the main girder adopts single-layer double-row arrangement of Bailey beams. Bailey beams have high strength characteristics and can effectively bear the self-weight and construction load of the box girder. When erecting the Bailey beams, they are installed according to the designed spacing and position, and each section of the Bailey beam is connected into a whole by using connecting pins to ensure firm connection. The distribution beam in the transverse direction of the bridge is erected above the Bailey beam, and the distribution beam adopts a type steel structure welded by double-channel steel butt joint. The steel pin is connected with the Bailey beam below to realize hinged connection, which not only ensures the relative rotation between the distribution beam and the Bailey beam, but also effectively transmits the load. The type steel structure welded by double-channel steel butt joint has high bending and shear capacity, and together with the Bailey beam, it forms a strong and high-capacity orthogonal grid support system, which can uniformly transmit the load of the box girder to the support platform.

[0036] Step 5, support form construction On the double-channel steel distribution beam, an adjustable height screw support system is set up to replace the traditional fixed square wood. The screw support system is composed of a matrix arrangement of adjustable screws, each of which can be independently adjusted in height. By laying a layer of thin and tough shaped steel plate on the top of the screw, a bearing surface for the box girder bottom form is formed. Before laying the shaped steel plate, the flatness is checked, and the flatness deviation is controlled within ±2mm to ensure that it can closely fit the screw. According to the design elevation and curve data in the three-dimensional BIM model, the initial height of each screw rod is accurately measured by using professional measuring instruments such as level, total station, etc. According to the design requirements, the top height of each screw rod is accurately adjusted by rotating the screw rod, so as to accurately shape the complex curved surface of the box girder bottom plate required by the design. During the adjustment process, the elevation of the top of the screw rod is monitored in real time by using the level to ensure the adjustment accuracy. For a certain curved part of the box girder bottom plate, according to the design requirements, the top height of several screw rods needs to be adjusted to different values respectively, and through the measurement by the level and the adjustment of the screw rod, the top of these screw rods forms a curve shape in accordance with the design requirements, which greatly improves the forming accuracy and quality of the box girder bottom plate.

[0037] Step 6, monitoring At the key observation points, triangular support frames and key stress parts of the Bailey beam span, fiber Bragg grating sensors and inclination sensors are laid. Fiber Bragg grating sensors use the optical properties of optical fibers to collect stress and strain data of the support platform in real time. By measuring the wavelength change of the reflected light of the fiber Bragg grating, the stress and strain size can be accurately calculated. When laying the fiber Bragg grating sensors, it is necessary to ensure that they are closely attached to the support structure to avoid loosening or falling off. Inclination sensors are used to monitor the micro-inclination deformation of triangular support frames. By measuring the component of gravitational acceleration on the sensitive axis of the sensor, the inclination angle of the triangular support frame can be calculated. The installation of the inclination sensor should ensure its levelness and perpendicularity to ensure the accuracy of the measurement data.

[0038] The collected data is transmitted in real time to the background terminal through wireless transmission modules such as Bluetooth, Wi-Fi, etc. In the background terminal, professional data processing software is used to analyze and process the collected data. The system sets a warning threshold, and when the monitoring value approaches the threshold, the software will automatically send an alarm message to remind the construction personnel to pay attention to safety. When the stress of the support platform reaches 80% of the design stress, the system sends a warning signal; when the stress reaches 90% of the design stress, the system sends an alarm to require the construction personnel to stop construction immediately and take appropriate measures.

[0039] Based on the preset deformation prediction algorithm, inverse analysis is carried out combined with the real-time data feedback in the construction process. By inputting the real-time monitoring data into the deformation prediction algorithm model, the model is corrected and optimized, and the deformation trend of the support system is dynamically predicted. According to the trend, instructions are sent to the adjustable curved surface formwork system, and the top elevation of the screw rod in the specified area is automatically adjusted by the control system, so as to correct the reserved camber of the formwork, actively offset the support sinking problem caused by the uneven tension on both sides of the V-shaped pier, and ensure the accuracy and quality of the box girder construction.

[0040] Finally, the formwork system dismantling step is also included After the concrete of the box girder reaches the design strength, the screw support system is lowered in reverse order to remove the load. First, the height of the screw is slowly lowered by adjusting the screw, so that the formwork and the concrete of the box girder are gradually separated. During the lowering process, the surface condition of the concrete of the box girder is closely observed to prevent cracks or damage on the surface of the concrete caused by improper formwork removal. Then, the shaped steel plate, the screw system, the shaped steel distribution beam, the main beam of the Bailey beam, and the triangular support frame are removed. During the removal process, the operation is strictly performed according to the removal sequence, and appropriate removal tools and equipment are used to ensure the safety of the removal process. Recyclable materials such as the Bailey beam, the shaped steel distribution beam, and the screw are recovered, cleaned, repaired, and inspected, and then can be used in other engineering projects to reduce construction costs.

[0041] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but as long as the combinations of the technical features do not contradict, they should be considered within the scope of the present disclosure.

[0042] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for constructing formwork support for the top box girder of a bridge V-shaped pier, characterized in that, Includes the following steps: S1. Construction Preparation: During the construction preparation phase, a 3D BIM model covering the V-shaped pier top support system and box girder structure is established. The 3D BIM model is used to perform spatial arrangement collision detection of the triangular support frame, Bailey beam main beam, and steel distribution beam, identifying and resolving node conflicts between embedded parts and pier reinforcement and prestressed ducts. Finite element analysis is used to simulate the load distribution at different construction stages of box girder casting, and the matrix arrangement density of anchor reinforcement and the welding node design of the triangular support frame are optimized based on the simulation results. Combined with historical prestressing test data, a deformation prediction algorithm for the support system is established in the 3D BIM model. S2. Laying out and positioning: Import the design coordinates from the three-dimensional BIM model into the GPS-RTK measuring instrument and total station, and digitally lay out the top of the V-shaped pier, marking the installation position of the embedded parts, the outline of the support platform and the position of key observation points. S3. Installation of embedded parts: Based on the layout results of S2, high-strength connectors are embedded inside the V-shaped pier; S4. Construction of the support platform: The high-strength connector includes a pre-embedded steel plate. A triangular support frame optimized in step S1 is welded onto the pre-embedded steel plate to form a cast-in-place support platform. A Bailey beam main beam in the longitudinal direction is erected on the cast-in-place support platform, and a transverse distribution beam is erected above the Bailey beam main beam. S5. Support Formwork Construction: An adjustable height screw support system is installed on the distribution beam. The screw support system consists of adjustable screws arranged in a matrix. A shaped steel plate is laid on top of the adjustable screws to form the support surface of the box girder bottom formwork. According to the design elevation and curve data in the three-dimensional BIM model, the top height of the adjustable screws is adjusted so that the shaped steel plate forms the complex curved surface of the box girder bottom plate. S6. Monitoring and control: Fiber optic grating sensors and tilt sensors are installed at the key observation points, triangular support frame and mid-span of Bailey beam main beam set in step S2; based on the deformation prediction algorithm preset in step S1, inversion analysis is performed in combination with real-time collected data to predict the deformation trend of the support system. According to the deformation trend, instructions are sent to the screw support system to adjust the top surface elevation of the adjusting screw in the designated area and correct the reserved upper camber of the template.

2. The construction method according to claim 1, characterized in that, In step S3, the pre-embedded steel plate is configured with multiple ribbed steel bars arranged in an optimized manner as anchoring steel bars. The ends of the anchoring steel bars are connected by mechanical threaded sleeves and an epoxy interface agent is applied before implantation into the concrete. Simultaneously, the pre-reserved threaded steel bar insertion holes are positioned according to the three-dimensional BIM model, and the threaded steel bars are inserted.

3. The construction method according to claim 1, characterized in that, In step S4, the main Bailey beam is arranged in a single layer with two rows; the distribution beam is a steel structure formed by welding double channel steel together, and is hinged to the main Bailey beam by steel pins to form an orthogonal grid support system.

4. The construction method according to claim 1, characterized in that, In step S6, the fiber optic grating sensor collects stress and strain data of the support platform, and the tilt sensor monitors the slight tilt deformation of the triangular support frame. The collected data is sent to the back-end terminal through the wireless transmission module. The back-end terminal sets a warning threshold, and automatically alarms when the monitored value approaches the threshold.

5. The construction method according to claim 2, characterized in that, In step S1, when optimizing the welding node design of the triangular support frame, the optimization basis includes empirical formulas based on finite element analysis results, and the total weld length satisfies: ； This represents the maximum load on the welded joint obtained from the finite element analysis, in N. Weld dimensions, in mm. This represents the allowable shear stress of the weld, expressed in MPa.

6. The construction method according to claim 1, characterized in that, In step S1, when optimizing the matrix arrangement density of the anchoring reinforcement, the optimization basis includes empirical formulas based on finite element analysis results and the required number of anchoring reinforcements. satisfy: ， This represents the maximum tensile stress (MPa) of the embedded steel plate obtained from finite element analysis. The area of ​​the embedded steel plate is in mm. 2 ; The diameter of the reinforcing bar is in mm. This refers to the anchorage length, in mm. This represents the bond strength between concrete and steel reinforcement, expressed in MPa. This is for the safety factor.

7. The construction method according to claim 2, characterized in that, The embedded steel plate is a 700mm×700mm rectangular steel plate with a thickness of 15mm. The four sides of the embedded steel plate are chamfered, and the surface is sandblasted to remove rust and then coated with an epoxy zinc-rich primer with a dry film thickness of 80μm. The precision-rolled threaded steel is PSB930 model with a diameter of 25mm. Three threaded steel through holes are reserved on each side of the single width, with a lateral spacing of 4.5m. The precision-rolled threaded steel is inserted into the corrugated pipe. The two ends of the corrugated pipe are 10-20cm shorter than the precision-rolled threaded steel, and the corrugated pipe is fixed with spiral ribs. Matching washers and nuts are screwed into the two ends of the spiral ribs.

8. The construction method according to claim 1, characterized in that, The triangular support frame described in S4 is made of four rows of 10mm thick triangular steel plates and 10mm thick rectangular steel plates of 400mm×700mm welded on both sides. The triangular steel plates are welded and fixed to the embedded steel plates.

9. The construction method according to claim 1, characterized in that, The thickness of the shaped steel plate mentioned in S5 is not less than 10mm, the adjustment accuracy of the adjusting screw is controlled within ±0.5mm, and the spacing of the screw support system is increased to 0.15m in the solid web area of ​​the box girder and 0.3m in other areas.

10. The construction method according to claim 4, characterized in that, The stress acquisition accuracy of the fiber optic grating sensor in S6 is not less than 0.1 MPa, and the angle measurement accuracy of the tilt sensor is not less than 0.01°.

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