A prefabricated box girder high-precision installation construction method with adaptive pose adjustment and three-dimensional positioning

Abstract

This invention discloses a high-precision installation method for precast box girders using adaptive attitude adjustment and three-dimensional positioning. The method involves completing the quality acceptance of the precast box girder, debugging the hoisting equipment, adaptive attitude adjustment hoisting device, and three-dimensional positioning system, and completing measurement, positioning, and benchmark monitoring point layout on the pier cap beam. Through synchronous support and integrated bearing installation technology, this invention ensures that the permanent bearings are subjected to uniform stress, avoiding early damage caused by bearing detachment or uneven pressure. The standardized stress conversion process eliminates local stress concentration in the box girder, preventing the generation of micro-cracks in the structure. The high-precision installation quality ensures the smooth overall alignment of the bridge, making the structural stress meet design requirements, effectively reducing the occurrence of later bridge defects, extending the overall service life of the bridge, and lowering the total life-cycle maintenance cost.

Description

Technical Field

[0001] This invention relates to the field of precast box girder technology, and in particular to a high-precision installation and construction method for precast box girders with adaptive attitude adjustment and three-dimensional positioning. Background Technology

[0002] Precast box girders, with their advantages of factory prefabrication, controllable quality, and fast construction speed, have become the mainstream form of superstructure for highway, railway, and municipal bridges.

[0003] As a core process in bridge construction, the installation of precast box girders directly determines the overall alignment, load-bearing capacity, structural durability, and construction period of a bridge, in terms of its construction precision, efficiency, and safety. With the development of bridge engineering in my country towards larger spans, larger tonnages, and higher standards, the technical shortcomings of traditional precast box girder installation techniques have become increasingly apparent, making it difficult to meet the construction requirements of modern bridge engineering.

[0004] Traditional precast box girder installation and construction mainly suffers from the following five major technical challenges: Firstly, the ability to control the lifting posture is insufficient. During the lifting of box girders, they are easily affected by uneven force at the lifting points, eccentric loads, and construction wind loads, resulting in tilting and large swaying. This not only leads to large positioning deviations but also easily causes collision damage between the box girder and the piers and bridge erecting machines, and even poses a risk of falling.

[0005] Secondly, the positioning and adjustment process is cumbersome and inefficient. After the box girder is initially positioned, it is necessary to rely on manual labor to repeatedly adjust the axis, elevation, and transverse and longitudinal slopes using jacks. The adjustment of a single box girder usually takes more than 1 hour, and the adjustment accuracy depends entirely on the operator's experience, making it difficult to achieve the high standard requirement of within ±2mm. During the adjustment process, excessive local stress can easily cause damage to the bottom plate, supports, and pier structures of the box girder.

[0006] Third, the quality of bearing installation is difficult to guarantee. The installation of temporary supports and permanent bearings is not synchronized. When the box girder is lowered, single-point impact stress is likely to occur, resulting in local pressure, voiding, and misalignment of the permanent bearings. According to industry statistics, the voiding rate of bearings under traditional methods is as high as 15%-20%, which seriously affects the uniformity of stress on the bridge structure and is prone to defects such as bearing cracking and beam deformation in the later stage.

[0007] Fourth, the entire process lacks intelligent monitoring and control methods. During construction, key parameters such as posture, position, and stress rely on manual visual inspection and experience-based judgment, making it impossible to achieve real-time, accurate digital monitoring and closed-loop control. This results in significant variations in construction quality, making it difficult to meet the alignment design requirements of high-standard bridges such as high-speed railways and urban expressways.

[0008] Fifth, the stress transfer process is not standardized. Traditional processes often use a one-time rapid unloading method. The transition from the stress of hoisting to the stress of permanent supports in the box girder is drastic, which can easily lead to local stress concentration, resulting in micro-cracks in the web and bottom plate of the box girder and reducing the structural durability.

[0009] To address the aforementioned issues, existing technologies largely focus on improvements in single aspects: some technologies enhance lifting stability by optimizing the structure of lifting equipment, but fail to solve the problem of automatic attitude control; some technologies modify the permanent support structure to reduce the risk of support detachment, but cannot achieve synchronous stress distribution between temporary and permanent supports at the construction process level; and some technologies introduce simple positioning and monitoring equipment, but fail to form a comprehensive, systematic solution encompassing attitude control, precise positioning, support installation, and stress conversion. These individual improvements cannot simultaneously address installation accuracy, construction efficiency, structural safety, and project cost, and are insufficient to fundamentally solve the core technical challenges of traditional precast box girder installation.

[0010] Based on this, the present invention proposes a high-precision installation method for precast box girders with adaptive attitude adjustment and three-dimensional positioning. It systematically innovates from three aspects: construction technology, special equipment, and intelligent monitoring, and comprehensively overcomes the technical bottlenecks of existing technologies. Summary of the Invention

[0011] In order to overcome the shortcomings of the existing technology, one of the objectives of this invention is to provide a high-precision installation and construction method for prefabricated box girders with adaptive attitude adjustment and three-dimensional positioning.

[0012] One of the objectives of this invention is achieved through the following technical solution: A high-precision installation method for precast box girders with adaptive attitude adjustment and three-dimensional positioning includes the following steps: S1 Construction Preparations: Complete the quality acceptance of precast box girders, debug hoisting equipment, adaptive attitude adjustment hoisting device and three-dimensional positioning system, and complete the measurement, positioning and layout and benchmark monitoring point layout on the pier top cap beam; S2 Adaptive Attitude Adjustment Lifting Device Assembly: Four sets of lifting points are symmetrically set on the top plate of the precast box girder. Each set of lifting points is equipped with an adaptive attitude adjustment lifting device. The top of the device is rigidly connected to the overhead crane of the bridge erecting machine to form a closed-loop attitude control system. S3 box girder graded lifting and attitude adaptive control: After graded trial lifting of the precast box girder and inspection for no abnormalities, the lifting continues. The closed-loop attitude control system collects and automatically corrects the horizontal tilt angle of the box girder in real time, maintaining the box girder's horizontal attitude throughout the entire process, and smoothly transports it to the preset height above the pier to be installed. S4 Three-dimensional Precision Alignment and Synchronous Temporary Support: Activate the three-dimensional positioning system, and complete the precise alignment of the longitudinal and transverse axes of the box girder with the marking on the pier top. Start the synchronous hydraulic support system on the pier top to make the support structure and the box girder lowering speed run synchronously, and complete the initial positioning and lateral limit fixation of the box girder. S5 Permanent Bearing Installation and Precise Alignment Adjustment: The permanent bearing is precisely placed at the designed position on the pier top, and the temporary support system and bearing leveling components are linked and controlled to precisely adjust the box girder elevation, cross slope and longitudinal slope. The bridge alignment is monitored in real time, and after the standard is met, a reliable connection between the permanent bearing and the box girder and pier is completed. S6 Step-by-Step Unloading and Construction Acceptance: Gradually release the load on the hoisting device to complete the smooth transition of the box girder from temporary to permanent load, verify the installation accuracy and test the structural stress state, and carry out subsequent bridge superstructure construction after acceptance.

[0013] Furthermore, the adaptive attitude adjustment hoisting device mentioned in step 2 includes a load-bearing lifting beam, a hydraulic leveling cylinder, an inclination sensor, a universal hinged lifting device, and anchor bolts; the hydraulic leveling cylinder is vertically installed at both ends of the load-bearing lifting beam, and the lower end of the cylinder rod is hinged to the pre-embedded parts of the box girder lifting point through the universal hinged lifting device; the inclination sensor is fixed at the bottom of the load-bearing lifting beam and is used to collect the horizontal inclination data of the box girder in real time.

[0014] Furthermore, the stroke of the hydraulic leveling cylinder is not less than 150mm, and the leveling accuracy of a single cylinder is ±0.1mm; the monitoring accuracy of the tilt sensor is ±0.01°, and its output end is electrically connected to the control system of the hoisting equipment to realize automatic compensation for attitude deviation.

[0015] Furthermore, the graded trial lifting described in step 3 specifically involves: starting the lifting equipment and slowly lifting the box girder; stopping the lifting when the box girder is 30cm off the ground; checking the stress state of each lifting point, the reliability of the connection of the lifting device, and the integrity of the box girder's appearance; and continuing the lifting after confirming that there are no abnormalities; and stopping the box girder 50cm above the top of the pier to be installed, waiting for precise alignment.

[0016] Furthermore, the three-dimensional positioning system in step 4 adopts a combined monitoring mode of total station and laser positioning instrument, and sets up monitoring points for the spatial position of the box girder and reference positioning points for the pier top respectively; the synchronous hydraulic support system for the pier top includes four sets of synchronous hydraulic support cylinders, symmetrically arranged on both sides of the permanent support installation point, and its synchronous jacking error is no more than 0.5mm.

[0017] Furthermore, the synchronous temporary support described in step 4 specifically involves: the lifting ends of the four sets of synchronous hydraulic support cylinders contacting the bottom of the box girder and lifting synchronously with the lowering speed of the box girder, so that the weight of the box girder is gradually transferred to the temporary support structure; after the box girder is lowered above the temporary support, the lateral limiting rods on the top of the pier hold the flanges on both sides of the box girder to lock the lateral position of the box girder.

[0018] Furthermore, in step 5, the permanent support is pre-selected according to the weight of the box girder and the design stress parameters, and the upper plate of the support is precisely aligned with the pre-embedded steel plate of the bottom plate of the box girder during installation; the precise fine adjustment of the alignment is achieved by linking and controlling the extension and retraction of four sets of synchronous hydraulic support cylinders and the thickness of the leveling shims at the bottom of the permanent support, and the axis and elevation errors of the box girder after adjustment are controlled within ±1mm.

[0019] Furthermore, the step-by-step unloading of the force described in step 6 is as follows: the hydraulic leveling cylinder of the adaptive attitude adjustment hoisting device is slowly retracted according to the diagonal synchronization principle, and the hoisting force is gradually released in 3-5 steps. After each unloading, the box girder is left to stand for 2-3 minutes to monitor the changes in the attitude of the box girder and the force on the support. After confirming that there are no abnormalities, the unloading is completed and the hoisting device is removed.

[0020] Furthermore, the pre-construction preparations mentioned in step 1 specifically include: verifying the concrete strength, appearance dimensions, embedded part positions, and lifting point setting quality of the precast box girder; cleaning debris from the bottom plate of the box girder and the cap beam of the pier; assembling and debugging the hydraulic system, attitude monitoring sensor, and data transmission module of the hoisting equipment; using a total station to lay out the longitudinal center line, transverse positioning line, and elevation control line of the box girder on the cap beam of the pier, marking the permanent support installation points, and laying out linear benchmark monitoring points along the longitudinal direction of the bridge.

[0021] Furthermore, the construction acceptance described in step 6 specifically includes: using a total station to verify the deviation of the box girder axis, the deviation of the elevation, and the gap between adjacent box girders; using a stress detector to test the uniformity of stress on each permanent support; and checking that the box girder body is free from damage and cracks. This construction method is suitable for the installation of large-tonnage precast box girders with spans of 20m-40m and can be applied to highway, railway, and municipal bridge projects.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. A closed-loop attitude control system composed of tilt sensors and hydraulic leveling cylinders is used to collect and automatically correct the horizontal tilt angle of the box girder in real time, keeping the horizontal tilt angle of the box girder ≤ ±0.03° throughout the process, effectively resisting the influence of wind load and eccentric load; combined with the three-dimensional joint monitoring technology of total station and laser positioning instrument, the spatial position of the box girder is digitally and accurately controlled, and the axis and elevation error of the box girder are controlled within ±1mm.

[0023] 2. This invention achieves automated control of posture adjustment, precise alignment, and fine-tuning of line shape, eliminating the tedious process of manually adjusting the position of the box girder repeatedly in traditional processes.

[0024] 3. A tiered trial lifting system was adopted, and a comprehensive safety inspection was carried out when the box girder was 30cm off the ground to eliminate potential lifting hazards in a timely manner; the adaptive attitude control system prevented the box girder from tilting, swaying and collision damage from the source; the synchronous hydraulic support system on the pier top realized the coordinated force of the box girder lowering and temporary support, avoiding single-point impact force.

[0025] 4. This invention, through synchronous support and integrated bearing installation technology, ensures that the permanent bearings are subjected to uniform stress, avoiding early damage caused by bearing detachment or eccentric pressure; the standardized stress conversion process eliminates local stress concentration in the box girder, preventing the generation of micro-cracks in the structure; the high-precision installation quality ensures the smooth overall alignment of the bridge, making the structural stress meet the design requirements, effectively reducing the occurrence of bridge defects in the later stage, extending the overall service life of the bridge, and reducing the total life cycle maintenance cost.

[0026] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0027] Figure 1 This is a framework diagram of the installation and construction method in this embodiment. Detailed Implementation

[0028] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0029] It should be noted that when a component is described as "fixed to" another component, it can be directly on the other component or may have a component in between. When a component is considered "connected to" another component, it can be directly connected to the other component or may have a component in between. When a component is considered "set on" another component, it can be directly set on the other component or may have a component in between. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] Example 1: Installation of 30m precast box girder for urban expressway viaduct 1.1 Project Overview The elevated expressway project in a certain city features a six-lane dual carriageway design for the main line. The superstructure consists of 30m span precast prestressed concrete box girders, each 1.6m high, with a top slab width of 2.4m and a bottom slab width of 1.0m. Each box girder has a design weight of 85t. The entire bridge comprises 120 box girders, erected span by span using a bridge-erecting machine. The design requirements are: box girder axis deviation ≤ ±2mm, elevation deviation ≤ ±2mm, and bearing stress unevenness coefficient ≤ 1.1.

[0032] 1.2 Pre-construction preparation 1. Quality acceptance of precast box girders: The concrete strength of the box girder reaches 100% of the design strength C50, and the elastic modulus meets the requirements; the appearance inspection shows no defects such as honeycomb, pitting, or cracks; the dimensional deviations of the box girder length, width, and height are all ≤±3mm; the embedded parts of the lifting points use Φ32mm precision rolled threaded steel, with an embedded depth of 30cm and a positional deviation of ≤±5mm; clean the debris and dust from the bottom plate of the box girder and the surface of the pier cap beam, and grind the contact parts of the supports until they are flat.

[0033] 2. Construction Equipment Commissioning: The JQ900A bridge erecting machine was used as the main hoisting equipment; four sets of adaptive attitude adjustment hoisting devices were assembled, each equipped with two YHG1-160 hydraulic leveling cylinders, with a rated lifting force of 40t per cylinder, a stroke of 200mm, and a leveling accuracy of ±0.1mm; the tilt sensor adopted a high-precision dual-axis MEMS tilt sensor with a monitoring accuracy of ±0.01° and a sampling frequency of 10Hz; the three-dimensional positioning system adopted a Leica TS60 total station (angle measurement accuracy 0.5″, distance measurement accuracy 1mm+1ppm) in conjunction with a RIEGLVZ-400 three-dimensional laser scanner; the hydraulic system pressure was adjusted to 16MPa, and no leakage was checked; the communication delay between the attitude monitoring system and the hydraulic control system was tested to be ≤50ms to ensure timely closed-loop control response.

[0034] 3. Measurement and positioning: The longitudinal center line, transverse positioning line and elevation control line of the box girder are laid out on the pier cap beam using a total station. The permanent support installation points are marked, and the point deviation is ≤ ±0.5mm. A linear benchmark monitoring point is set up every 10m along the longitudinal direction of the bridge, for a total of 12 benchmark points, forming a closed traverse network. The accuracy of the traverse measurement meets the requirements of second-order leveling.

[0035] 1.3 Assembly of Adaptive Attitude Adjustment Lifting Device Four sets of lifting points are symmetrically set at 1.5m from the top of the precast box girder, and each set of lifting points is equipped with an adaptive attitude adjustment lifting device. The load-bearing lifting girder is made of HM588×300×12×20 H-beam steel, with a length of 2.5m. The top is rigidly connected to the overhead crane of the bridge erecting machine by high-strength bolts. The hydraulic leveling cylinders are vertically installed at both ends of the load-bearing lifting girder. The lower end of the cylinder rod is hinged to the embedded parts of the box girder lifting point through a ball-joint universal hinge lifting device. The universal hinge lifting device allows a rotation angle of ±15°. The tilt sensor is fixed at the center of the bottom of the load-bearing lifting girder and is connected to the central control system of the bridge erecting machine through a shielded cable to form a closed-loop attitude control system.

[0036] 1.4 Box Girder Stage Lifting and Adaptive Attitude Control 1. Staged trial lifting: Start the bridge erecting machine's lifting system and slowly lift the box girder at a speed of 0.2m / min. Stop lifting when the box girder is 30cm off the ground and let it stand for 5 minutes. Check that the force is even at each lifting point, the hydraulic system pressure is stable at 12MPa, and there are no abnormal noises. Check that the connecting bolts of the lifting device are not loose and that the box girder has no deformation or cracks. After confirming that there are no abnormalities, continue lifting.

[0037] 2. Automatic attitude adjustment: During the lifting of the box girder, the tilt sensor collects the horizontal tilt angle data of the box girder on the X and Y axes in real time and transmits it to the control system. When the tilt angle exceeds ±0.02°, the control system automatically drives the corresponding hydraulic leveling cylinder to extend and retract to compensate for the attitude deviation and keep the horizontal tilt angle of the box girder ≤±0.03° throughout the process. The maximum instantaneous wind speed measured during construction was 8m / s. The attitude control system effectively resisted the influence of wind load, and the box girder did not sway significantly.

[0038] 3. Smooth transport: Operate the bridge erecting machine to transport the box girder horizontally at a speed of 0.3m / s to the top of the pier to be installed, stop 50cm away from the design elevation, and adjust the position of the bridge erecting machine's main trolley and auxiliary trolley so that the box girder is roughly aligned with the positioning line on the top of the pier.

[0039] 1.5 Three-dimensional precise alignment and synchronous temporary support 1. Precise alignment: The three-dimensional laser positioning system is activated, and four positioning targets are set on the bottom plate of the box girder to match the reference point on the top of the pier in real time; the control system fine-tunes the position of the bridge erecting machine according to the positioning data, so that the deviation between the longitudinal centerline of the box girder and the design axis is ≤0.5mm and the deviation between the transverse centerline and ≤0.4mm.

[0040] 2. Synchronous support lowering: Activate 4 sets of YHG1-200 synchronous hydraulic support cylinders on the pier top. The rated lifting force of the cylinder is 50t, and the synchronous lifting error is ≤0.3mm. Temporary rubber supports are pre-placed at the lifting end of the support cylinder. After contacting the bottom of the box girder, they are lifted synchronously with the lowering speed of the box girder (0.1m / min) to gradually transfer the weight of the box girder to the temporary support structure and avoid single-point impact stress.

[0041] 3. Initial positioning and fixing: After the box girder is lowered above the temporary support, the lateral limiting top rods (100mm stroke) set on both sides of the pier top are used to hold the box girder flange plate, lock the lateral position of the box girder and prevent the box girder from shifting.

[0042] 1.6 Permanent Support Installation and Precise Linear Adjustment 1. Bearing placement: Use pre-selected GYZ250×56 type plate rubber bearings with a thickness deviation of ≤0.1mm and a hardness deviation of ≤±2 Shore degrees; accurately place the bearings at the design mark position on the top of the pier, so that the upper bearing plate of the bearing is precisely aligned with the 500×500×20mm pre-embedded steel plate of the bottom plate of the box girder, with an alignment deviation of ≤0.3mm.

[0043] 2. Alignment and Elevation Adjustment: The extension and retraction of four sets of synchronous hydraulic support cylinders are linked and controlled with the stainless steel leveling shims (thickness 0.1mm-5mm) at the bottom of the permanent supports to accurately adjust the elevation, cross slope and longitudinal slope of the box girder; the bridge alignment benchmark point is monitored in real time. After adjustment, the elevation deviation of the box girder is ≤±0.4mm, the cross slope is 0.5% (design value), and the longitudinal slope is 1.2% (design value), resulting in a smooth overall bridge alignment.

[0044] 3. Support fixing: After confirming the position, alignment, and elevation of the box girder, fill the gap between the support and the top of the pier and the bottom plate of the box girder with epoxy resin mortar. After the mortar strength reaches the design requirements, lock the support anchor bolts to complete the reliable connection between the permanent support and the box girder and pier.

[0045] 1.7 Step-by-step unloading of loads and construction acceptance 1. Step-by-step unloading: The hydraulic leveling cylinder of the adaptive attitude adjustment hoisting device is slowly retracted according to the diagonal synchronous principle. The hoisting force is gradually released in 4 steps, with the cylinder retracting 5mm each time and left to stand for 2 minutes. Stress sensors are used to monitor the stress change of the support in real time. After each unloading, the maximum stress deviation of the support is ≤5%. After all unloading is completed, it is left to stand for 10 minutes to confirm that the box girder is stable before removing the hoisting device.

[0046] 2. Quality Acceptance: The total station was used to verify that the box girder axis deviation was 0.6mm, the elevation deviation was 0.4mm, and the gap between adjacent box girders was 10mm (design value); the pressure sensor was used to detect the stress on the four permanent supports, and the stress unevenness coefficient was 1.03; the box girder body was checked to find no damage or cracks, and the supports were found to be free of voids or uneven pressure.

[0047] 3. Subsequent construction: After acceptance, the transverse connection of the box girder, the binding of the wet joint reinforcement and the pouring of C50 micro-expansion concrete will be carried out.

[0048] In this embodiment, the average installation time for a single box girder is 82 minutes, which is 45% shorter than the traditional process (about 150 minutes). The installation accuracy far exceeds the design requirements, and the construction process is safe and controllable.

[0049] Example 2: Installation and Construction of 40m Large-tonnage Precast Box Girder for Highway 2.1 Project Overview The main bridge of a certain expressway is a 40m span precast prestressed concrete box girder, 2.0m high, 3.2m wide at the top, and 1.2m wide at the bottom. The design weight of a single box girder is 135t. The entire bridge consists of 86 box girders, erected using a double-guide beam bridge erecting machine. The design requirements are that the axial deviation of the box girders be ≤±1.5mm, the elevation deviation be ≤±1.5mm, and there should be no gaps or uneven pressure on the supports.

[0050] 2.2 Construction Optimization and Implementation The construction steps in this embodiment are basically the same as in Embodiment 1, with the following optimizations made to address the characteristics of large-tonnage box girders: 1. Equipment parameter optimization: The hydraulic leveling cylinder of the adaptive attitude adjustment hoisting device was replaced with the YHG1-200 type, with a rated lifting force of 60t per cylinder and a stroke of 250mm; the synchronous hydraulic support cylinder on the pier top was replaced with the YHG1-250 type, with a rated lifting force of 80t per cylinder and a synchronous lifting error of ≤0.4mm; a wind load monitoring system was added, using an ultrasonic anemometer for real-time monitoring, and hoisting operations were stopped when the wind speed exceeded level 6 (10.8m / s).

[0051] 2. Attitude control optimization: A wind-resistant compensation algorithm is added to the closed-loop control system to adjust the pre-pressure of the hydraulic cylinder in advance based on real-time wind speed data, thereby improving the stability of box girder hoisting; two total stations are used to cross-monitor the attitude of the box girder, and the control signal is output after data fusion to further improve the monitoring accuracy.

[0052] 3. Optimization of bearing installation: The permanent bearing adopts GPZ(II)2.5DX type pot rubber bearing. The upper bearing plate of the bearing is welded to the pre-embedded steel plate of the box girder. The weld height is 10mm. The preheating temperature is 100℃ before welding to avoid welding deformation. When adjusting the alignment, the influence of the pre-camber of the box girder is taken into consideration. The pre-camber is set at 20mm. After adjustment, the deviation between the alignment of the box girder and the design pre-camber curve is ≤±1mm.

[0053] 2.3 Construction Results Post-installation inspection results: Box girder axis deviation 0.8mm, elevation deviation 0.6mm, and joint height difference between adjacent box girders 0.5mm; ultrasonic testing of bearing contact area showed a contact rate of over 98%, with no voids or uneven pressure; average installation time per box girder was 95 minutes, a 42% reduction compared to traditional methods (approximately 165 minutes). No box girder collisions, damage, or safety accidents occurred during construction, and the construction quality meets the requirements of the "Technical Specifications for Highway Bridge and Culvert Construction" (JTG / T3650-2020).

[0054] Example 3: Installation and Construction of 20m Small-Span Precast Box Girder for Municipal Bridges 3.1 Project Overview A municipal pedestrian overpass project has a superstructure consisting of 20m span precast reinforced concrete box girders, with a girder height of 1.0m, a top slab width of 2.0m, a bottom slab width of 0.8m, and a design weight of 35t per box girder. Due to the narrow construction site, a 50t truck crane was used for hoisting. The design requirement is that the box girder positioning accuracy be ≤±1mm.

[0055] 3.2 Key Points of Construction Implementation 1. Lifting equipment compatibility: A 50t truck crane is used as the main lifting equipment, and the adaptive attitude adjustment lifting device is rigidly connected to the truck crane hook; due to the small weight of the box girder, the hydraulic leveling cylinder adopts the YHG1-100 type, with a single cylinder rated lifting force of 20t and a stroke of 150mm.

[0056] 2. Simplified positioning system: A single total station is used in conjunction with prisms for three-dimensional positioning. Three positioning prisms are set at both ends and the center of the box girder to monitor the spatial position of the box girder in real time, and the positioning accuracy reaches ±0.5mm.

[0057] 3. Simplified temporary support: Two sets of synchronous hydraulic support cylinders are used on the top of the pier, symmetrically arranged on both sides of the permanent support to meet the temporary support requirements of the box girder; after the box girder is lowered, wooden wedges are used for lateral restraint.

[0058] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A high-precision installation method for precast box girders with adaptive attitude adjustment and three-dimensional positioning, characterized in that, Includes the following steps: S1 Construction Preparations: Complete the quality acceptance of precast box girders, debug hoisting equipment, adaptive attitude adjustment hoisting device and three-dimensional positioning system, and complete the measurement, positioning and layout and benchmark monitoring point layout on the pier top cap beam; S2 Adaptive Attitude Adjustment Lifting Device Assembly: Four sets of lifting points are symmetrically set on the top plate of the precast box girder. Each set of lifting points is equipped with an adaptive attitude adjustment lifting device. The top of the device is rigidly connected to the overhead crane of the bridge erecting machine to form a closed-loop attitude control system. S3 box girder graded lifting and attitude adaptive control: After graded trial lifting of the precast box girder and inspection for no abnormalities, the lifting continues. The closed-loop attitude control system collects and automatically corrects the horizontal tilt angle of the box girder in real time, maintaining the box girder's horizontal attitude throughout the entire process, and smoothly transports it to the preset height above the pier to be installed. S4 Three-dimensional Precision Alignment and Synchronous Temporary Support: Activate the three-dimensional positioning system, and complete the precise alignment of the longitudinal and transverse axes of the box girder with the marking on the pier top. Start the synchronous hydraulic support system on the pier top to make the support structure and the box girder lowering speed run synchronously, and complete the initial positioning and lateral limit fixation of the box girder. S5 Permanent Bearing Installation and Precise Alignment Adjustment: The permanent bearing is precisely placed at the designed position on the pier top, and the temporary support system and bearing leveling components are linked and controlled to precisely adjust the box girder elevation, cross slope and longitudinal slope. The bridge alignment is monitored in real time, and after the standard is met, a reliable connection between the permanent bearing and the box girder and pier is completed. S6 Step-by-Step Unloading and Construction Acceptance: Gradually release the load on the hoisting device to complete the smooth transition of the box girder from temporary to permanent load, verify the installation accuracy and test the structural stress state, and carry out subsequent bridge superstructure construction after acceptance.

2. The method for high-precision installation of precast box girders with adaptive attitude adjustment and three-dimensional positioning according to claim 1, characterized in that, The adaptive attitude adjustment hoisting device mentioned in step 2 includes a load-bearing lifting beam, a hydraulic leveling cylinder, an inclination sensor, a universal hinged lifting device, and anchor bolts. The hydraulic leveling cylinder is vertically installed at both ends of the load-bearing lifting beam, and the lower end of the cylinder rod is hinged to the pre-embedded parts of the box girder lifting point through the universal hinged lifting device. The inclination sensor is fixed to the bottom of the load-bearing lifting beam and is used to collect the horizontal inclination data of the box girder in real time.

3. The method for high-precision installation of precast box girders with adaptive attitude adjustment and three-dimensional positioning according to claim 2, characterized in that, The stroke of the hydraulic leveling cylinder is not less than 150mm, and the leveling accuracy of a single cylinder is ±0.1mm; the monitoring accuracy of the tilt sensor is ±0.01°, and its output end is electrically connected to the control system of the hoisting equipment to realize automatic compensation for attitude deviation.

4. The method for high-precision installation of precast box girders with adaptive attitude adjustment and three-dimensional positioning according to claim 1, characterized in that, The specific steps of the graded trial lifting in step 3 are as follows: start the lifting equipment and slowly lift the box girder. Stop lifting when the box girder is 30cm off the ground. Check the stress state of each lifting point, the reliability of the connection of the lifting device and the integrity of the box girder appearance. After confirming that there are no abnormalities, continue lifting. The box girder is transferred to a position 50cm above the top of the pier to be installed, and stops, waiting for precise alignment.

5. The method for high-precision installation of precast box girders with adaptive attitude adjustment and three-dimensional positioning according to claim 1, characterized in that, The three-dimensional positioning system described in step 4 adopts a combined monitoring mode of total station and laser positioning instrument, and sets up monitoring points for the spatial position of the box girder and reference positioning points for the pier top respectively; the synchronous hydraulic support system for the pier top includes four sets of synchronous hydraulic support cylinders, symmetrically arranged on both sides of the permanent support installation point, and the synchronous jacking error is no more than 0.5mm.

6. The method for high-precision installation of precast box girders with adaptive attitude adjustment and three-dimensional positioning according to claim 5, characterized in that, The synchronous temporary support described in step 4 is as follows: the lifting ends of the four sets of synchronous hydraulic support cylinders contact the bottom of the box girder and lift synchronously with the lowering speed of the box girder, so that the weight of the box girder is gradually transferred to the temporary support structure; after the box girder is lowered above the temporary support, the lateral limiting rods on the top of the pier hold the flanges on both sides of the box girder to lock the lateral position of the box girder.

7. The method for high-precision installation of precast box girders with adaptive attitude adjustment and three-dimensional positioning according to claim 1, characterized in that, In step 5, the permanent support is selected in advance according to the weight of the box girder and the design stress parameters. When it is installed, the upper plate of the support is precisely aligned with the pre-embedded steel plate of the bottom plate of the box girder. The precise fine adjustment of the line shape is achieved by linking and controlling the extension and retraction of four sets of synchronous hydraulic support cylinders and the thickness of the leveling shims at the bottom of the permanent support. After adjustment, the axis and elevation error of the box girder are controlled within ±1mm.

8. The method for high-precision installation of precast box girders with adaptive attitude adjustment and three-dimensional positioning according to claim 1, characterized in that, The step-by-step unloading of the load in step 6 is as follows: the hydraulic leveling cylinder of the adaptive attitude adjustment hoisting device is slowly retracted according to the diagonal synchronization principle, and the hoisting load is gradually released in 3-5 steps. After each unloading, the box girder is left to stand for 2-3 minutes to monitor the changes in the attitude of the box girder and the load on the support. After confirming that there are no abnormalities, the unloading is completed and the hoisting device is removed.

9. The method for high-precision installation of precast box girders with adaptive attitude adjustment and three-dimensional positioning according to claim 1, characterized in that, The pre-construction preparations described in Step 1 specifically include: verifying the concrete strength, appearance dimensions, embedded part positions, and lifting point setting quality of the precast box girder; cleaning debris from the bottom plate of the box girder and the pier cap beam; assembling and debugging the hydraulic system, attitude monitoring sensors, and data transmission modules of the hoisting equipment; using a total station to lay out the longitudinal centerline, transverse positioning line, and elevation control line of the box girder on the pier cap beam, marking the permanent support installation points, and setting up alignment benchmark monitoring points along the longitudinal direction of the bridge.

10. The method for high-precision installation of precast box girders with adaptive attitude adjustment and three-dimensional positioning according to claim 1, characterized in that, The construction acceptance process described in step 6 specifically includes: using a total station to verify the deviation of the box girder axis, elevation deviation, and gap between adjacent box girders; using a stress detector to check the uniformity of stress on each permanent support; and checking that the box girder body is free from damage and cracks. This construction method is suitable for the installation of large-tonnage precast box girders with spans of 20m-40m and can be applied to highway, railway, and municipal bridge projects.

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