Construction method for grading water preloading of rubber and plastic bag body of full-support cast-in-situ box girder with longitudinal and transverse large slope

Abstract

The application discloses a kind of longitudinal transverse large slope cast-in-place box girder full support rubber plastic capsule grading water preloading construction method, it is related to bridge engineering construction technical field.For the defects such as long traditional preloading period, high cost, poor adaptation of large slope, low precision, by load conversion design rubber plastic capsule, angle steel limiting is used in large slope working condition, fiber rope is tied and reinforced, "water pump-sensor-PLC" double closed loop system pressure control (±1.5%) and flow (±2%) are built, three-dimensional monitoring network is constructed, grading water filling (60%→80%→110% load), symmetric unloading and recycling water (utilization≥80%).The method shortens the preloading period to 27 days, reduces the cost by 62%, adapts to longitudinal slope≤5% / lateral slope≤3%, is safe, environmentally friendly and high-precision, and is suitable for large slope cast-in-place box girder support preloading.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering construction technology, specifically to a method for graded water-filled preloading construction of a full-span scaffold for cast-in-place box girders with large longitudinal and transverse slopes. Background Technology

[0002] In the construction of cast-in-place box girders, preloading of the full-span scaffolding is a crucial step in ensuring construction safety and that the girder alignment meets design requirements. Preloading eliminates inelastic deformation of the scaffolding and foundation, and obtains elastic deformation parameters, providing a basis for setting the scaffolding pre-camber. Currently, the mainstream preloading methods in the industry mainly include precast concrete block loading, soil / sandbag loading, and traditional water bag loading, but they have significant drawbacks in practical applications:

[0003] Currently, the construction process for precast concrete blocks / soil bags is cumbersome, requiring a large amount of manpower for high-altitude hoisting and stacking. Not only does the hoisting cycle take 30 to 60 days, but the risk of falling and collisions during the hoisting process is also high. At the same time, the stacked weight relies on manual counting and estimation, making it difficult to achieve precise control and prone to local overloading or uneven loading, resulting in uneven stress on the support and increasing the risk of instability. In addition, the rental cost of precast blocks is high, and the transportation costs for entering and leaving the site are also high, resulting in serious waste of resources.

[0004] Secondly, while traditional water bag stacking can reduce costs to some extent, it lacks a specific adaptation scheme for bridges with large longitudinal and transverse slopes. Water bags are prone to sliding along the slope and cannot simulate the actual stress state of the beam. Furthermore, it lacks graded loading control and precise monitoring methods, resulting in poor load uniformity and difficulty in meeting the preloading requirements of large-span, high-load box girders. At the same time, traditional water bags are mostly for single use, and water resources cannot be recycled, which does not conform to the concept of green construction.

[0005] In summary, existing prestressing technologies cannot simultaneously achieve high efficiency, safety, accuracy, and environmental friendliness. In particular, for cast-in-place box girder projects with large longitudinal and transverse slopes, there is an urgent need for a prestressing method that can achieve precise load control, adapt to complex slopes, shorten the construction cycle, and is green and economical. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for the graded water-filled preloading construction of a full-span scaffold for cast-in-place box girders with large longitudinal and transverse slopes, thus solving the problems mentioned in the background section.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for staged water-filled preloading construction of a full-span scaffolding system for cast-in-place box girders with large longitudinal and transverse slopes, comprising the following steps:

[0008] S1. Construction preparation, which consists of technical construction preparation and on-site construction preparation;

[0009] S2. Laying and reinforcement of the rubber-plastic capsule, as detailed below:

[0010] S201. According to the water bag layout plan, pop up the water bag placement edge line on the bottom mold, mark the position according to the number, and ensure that the distance deviation between adjacent water bags is ≤50mm.

[0011] S202. Water bags are placed sequentially from the low end to the high end along the longitudinal slope of the box girder, ensuring that the water bag outlet faces the low end (for easy drainage) and the water inlet faces the high end (for easy water filling); each water bag is connected to the water pump through an independent water supply pipeline, and the pipe fitting interface is sealed with a sealing ring, with ≥300mm of maintenance space reserved.

[0012] S203, Specialized reinforcement (for longitudinal slope > 5% or transverse slope > 3%).

[0013] S204. Perform graded pressure testing according to GB / T19624 standard. Inflate the water bag to 0.02MPa, maintain the pressure for 30 minutes, and apply soap solution to the seam. If there are no bubbles, the initial inspection is qualified. Continue to inflate to 0.15MPa, maintain the pressure for 1 hour, and use a laser diameter gauge to measure the diameter change of the water bag. If the diameter shrinkage rate is ≤1.5%, the seal is qualified.

[0014] S3. Water source connection and intelligent control system setup, details are as follows:

[0015] S301. The hierarchical pipe network is constructed using a three-level pipe network system of "water pump → water distribution valve → water distribution bag → water bag". 2~3kW submersible pumps (flow rate 5~200m³ / h) are preferred and are placed at stable water sources (such as foundation pits, wells, and ponds). The main pipe uses steel wire hose (pressure resistance ≥0.6MPa), and the branch pipes use PVC pipes. All joints are fastened with hose clamps to prevent leakage.

[0016] S302, Intelligent dual closed-loop control operation;

[0017] S303. Conduct a water flow test to verify that there is no leakage in the pipeline and that the inflation of each water bag is synchronized (inflation rate deviation ≤10%), and ensure that the pressure and flow control accuracy meets the set requirements.

[0018] S4. The layout of monitoring points and the determination of measurement methods are as follows:

[0019] S401, Construction of a three-dimensional monitoring network;

[0020] S402. Monitoring Content and Requirements;

[0021] S403. Calculate the total deformation of the support based on the monitoring data, and set the pre-camber according to the formula:

[0022]

[0023] in The precamber value (mm) for a certain cross section; This represents the total pre-camber value at mid-span (mm). ; The distance (m) from a certain cross section to the beam end; The span of the beam is (m).

[0024] S5. Staged water filling and preloading, with staged loading control and settlement observation operations performed respectively;

[0025] S6. Unloading and bottom mold adjustment, details are as follows:

[0026] S601. Following the principle of "last loading, first unloading, and layered symmetry", the unloading sequence adopts 110% total load, 80% total load, and 60% total load until the initial state; after each level of unloading is completed, the next level of unloading will be carried out only after the observation and recording are completed.

[0027] S602. After the pre-stressing is qualified, adjust the bottom formwork to the design elevation based on the pre-camber calculated from the monitoring data; after adjustment, re-measure the elevation. If the deviation is ≤3mm, it is qualified; otherwise, a second adjustment is required.

[0028] S7. Pre-pressurized water recovery, details are as follows:

[0029] S701. Excavate a temporary water pit (volume ≥ 1.2 times the total pre-pressurization water volume) at a distance of ≥ 5m outside the support red line, and lay a 0.5mm thick plastic film in the pit for seepage prevention;

[0030] S702. Open the water bag drain valve, pump water into the water pit, and then pump it to the project water storage tank (sealing ≥0.1MPa) for centralized storage. The water will be used for subsequent concrete curing or preloading of the next box girder, thus realizing the recycling of water resources.

[0031] Optionally, the technical construction preparation in step S1 includes:

[0032] (1) Based on the combined values ​​of the self-weight of the reinforced concrete beam, the load of the formwork system, and the self-weight of the support in the design drawings, determine the design load value per square meter of the support area through structural verification. (Unit: kN / m) 2 ); based on the specific gravity of water Based on the formula Calculate the water bag filling height corresponding to the equivalent water load. (Unit: m);

[0033] (2) Based on the converted filling height The dimensions of the rubber and plastic bladders were designed; at the same time, the maximum stacking height of the water bags was limited to ≤X meters (X is determined according to the load-bearing capacity of the support) to avoid local overpressure.

[0034] (3) Draw construction drawings, including a plan view of the water bag layout, detailed reinforcement drawings, a three-dimensional view of the water supply pipeline, and a loading sequence diagram:

[0035] Water bag layout plan:

[0036] Label each water bag with its number, positioning dimensions, and spacing, and reserve space for water pump installation;

[0037] Detailed reinforcement diagram:

[0038] Clarify the details of the anti-slip pad layer at the bottom of the water bag and the details of the lateral restraint components;

[0039] 3D diagram of water supply pipeline:

[0040] Distinguish between the elevations of main pipes and branch pipes, mark the pipe diameter specifications, and install elastic supports for vibration damping between the water pipes and the support structure;

[0041] Loading sequence diagram:

[0042] Use arrows of different colors to indicate the sequence of water injection and specify the adjustment parameters of the flow control valve.

[0043] Optionally, the on-site construction preparation in step S1 specifically includes:

[0044] (1) Check the step distance, row distance, diagonal bracing arrangement and top support tightness of the full-span scaffolding, and confirm that the bottom formwork is erected according to the pre-camber design; check the foundation compaction and drainage system to prevent foundation settlement caused by rain erosion.

[0045] (2) Clean the surface of the bottom formwork and remove sharp objects; wrap the protruding components that cannot be removed with a soft cloth and lay a bamboo plywood isolation layer; seal the gaps at the joints of the formwork to prevent water from seeping into the foundation of the support;

[0046] (3) Clear the traffic passage on the side of the support to ensure smooth transportation of water bags and water pump equipment.

[0047] Optionally, the specific reinforcement steps in step S203 are as follows:

[0048] (1) Set a ∠50×5 angle steel limit frame along the circumference of the water bag and anchor it to the bottom mold with M12 chemical anchor bolts. A 10mm thick EVA buffer pad is attached to the inside of the angle steel to prevent the water bag from being damaged by rigid friction with the angle steel.

[0049] (2) A cross-binding system is formed by using 10mm diameter synthetic fiber ropes, with pre-embedded lifting rings connected to both ends of the fiber ropes and tensioned;

[0050] (3) Vertical poles are fabricated using [10 channel steel at the flange plates on both sides of the box girder, and dense mesh netting is installed to create a 1m wide pedestrian passage.

[0051] Optionally, the intelligent dual closed-loop control in step 302 is as follows:

[0052] (1) Install an electronic pressure sensor on the main inlet pipe and an electromagnetic flow meter on the branch pipe. Connect the sensor signal to the PLC controller. The PLC is linked with the variable frequency water pump and the electric regulating valve respectively.

[0053] (2) Set the following through the HMI human-machine interface: initial water filling speed is 0.5 to 2 L / min; pressure threshold is 80% of the design pre-pressure value; stability judgment condition is pressure fluctuation ≤ ±1% and lasts for 5 min; safety pressure relief value is 110% of the design pressure.

[0054] Optionally, the construction of the three-dimensional monitoring network in step S401 includes longitudinal monitoring sections and transverse monitoring points;

[0055] Longitudinal monitoring section:

[0056] Five monitoring sections were arranged along the span of the box girder, namely:

[0057] Section 1: End support area of ​​the clear span (1m from the center of the support);

[0058] The bending moment transition zone at section 2 / 4:1 / 4L (L is the span, located 10m from section 1 / 5).

[0059] Section 3: Maximum deformation zone at mid-span (L / 2);

[0060] Horizontal monitoring points:

[0061] Monitoring points are set up along a 5m module for each cross section, with key coverage areas:

[0062] Left flange cantilever section (0.5m from the beam edge);

[0063] The abrupt change zone of the lateral stiffness of the base plate (0.3m from each edge of the left and right base plates);

[0064] Neutral axis region of the cross section (at the beam width centerline);

[0065] Five monitoring points are set up for each section, located on the foundation of the support (ground) under the bottom plate and on the bottom formwork of the web plate. The monitoring points are located using a total station with a deviation of ≤2mm.

[0066] Optionally, the monitoring content and requirements in step S402 include:

[0067] (1) Before loading, measure the initial elevation of all monitoring points and establish a benchmark file; after each loading stage, pause loading and monitor for 12 hours and record the settlement; during the load holding stage, monitor at regular intervals every day and record the settlement for 24 hours / 72 hours; 6 hours after unloading, remeasure the elevation of each monitoring point and calculate the elastic deformation.

[0068] (2) After each loading stage: the average settlement of the monitoring points within 12 hours is ≤2mm before the next loading stage can be started; during the holding stage: if the average settlement of the monitoring points is ≤1mm for 24 consecutive hours or ≤5mm for 72 consecutive hours, the preloading is deemed qualified; if the settlement exceeds the limit, the loading is stopped immediately, the foundation of the support or reinforcement measures are checked, and the preloading is restarted after rectification.

[0069] Optionally, in step S403 The elastic deformation due to the beam's own weight. This is the compression amount of the pad. For the deflection of the support, For inelastic deformation of the support, For the elastic deformation of the support, This is due to foundation deformation.

[0070] Optionally, the loading hierarchy control in step S5 specifically includes:

[0071] (1) Loading is performed in three stages to reach 110% of the total design load, with each stage of loading being 60%, 80%, and 110% of the total weight, respectively;

[0072] (2) The loading sequence is longitudinal first and then transverse, with the load distributed symmetrically from the mid-span of the box girder to both ends; and the load is distributed symmetrically from the center line of the box girder to both sides.

[0073] When loading, close the water bag drain valve, connect the water inlet valve through the fire pipe, start the submersible pump to inject water, and the PLC controller automatically controls the water inlet according to the set flow rate. A designated person inspects the pipeline sealing and the deformation of the water bag.

[0074] Optionally, in step S5, the settlement observation is performed by using an electronic level to measure the elevation of each monitoring point in sequence according to its number, and the data is recorded.

[0075] This invention provides a method for staged water-filled preloading construction of a full-span scaffolding system for cast-in-place box girders with steep longitudinal and transverse slopes, which has the following beneficial effects:

[0076] This method of using a graded water-filled preloading construction method for full-span scaffolding of cast-in-place box girders with large longitudinal and transverse slopes simplifies the construction process and significantly shortens the preloading cycle of a single box girder. The rubber-plastic bladders are reusable, greatly reducing equipment entry and exit time. Compared with precast concrete blocks, this method has significantly lower material costs. Furthermore, water resources are recycled, reducing water bills and drainage costs. Intelligent dual closed-loop control and a three-dimensional monitoring network ensure uniform load distribution and precise deformation capture, guaranteeing a high preloading pass rate. It also eliminates the need for high-altitude heavy object handling, mitigating the risks of falls and collisions. Damage to the flexible rubber-plastic bladders results in no hard objects falling, and combined with a lateral reinforcement system, it is suitable for complex working conditions with longitudinal slopes ≤5% and transverse slopes ≤3%. The rubber-plastic bladders use recyclable and environmentally friendly materials, reducing construction waste. Higher water resource recycling rates reduce construction dust and energy consumption. Attached Figure Description

[0077] Figure 1 This is a flowchart of the construction process for the invention;

[0078] Figure 2 This is a schematic diagram of the arrangement of the rubber and plastic capsules of the invention.

[0079] Figure 3 This is a schematic diagram of the synthetic fiber rope cross binding system of the invention;

[0080] Figure 4 This is a schematic diagram of the longitudinal section layout of the monitoring points for this invention;

[0081] Figure 5 This is a schematic diagram of the cross-sectional layout of the monitoring points for this invention;

[0082] Figure 6 This is a schematic diagram of the pre-camber calculation for the invention;

[0083] Figure 7 This is a schematic diagram of the settlement observation data recording for this invention. Detailed Implementation

[0084] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0085] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0086] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0087] Please see Figures 1 to 7This invention provides a technical solution: a method for staged water-filled preloading construction of a full-span scaffold for cast-in-place box girders with large longitudinal and transverse slopes, comprising the following steps:

[0088] S1. Construction preparation, which consists of technical construction preparation and on-site construction preparation;

[0089] Technical construction preparation includes:

[0090] (1) Based on the combined load values ​​of the beam's reinforced concrete self-weight, formwork system load, and support self-weight in the design drawings, determine the design load value per square meter of the support area through structural verification. (Unit: kN / m) 2 ); based on the specific gravity of water Based on the formula Calculate the water bag filling height corresponding to the equivalent water load. (Unit: m), ensuring that the preload is equivalent to the design load;

[0091] (2) Based on the converted filling height The dimensions of the rubber and plastic bladder are designed (preferably length × width × height = 10m × 5m × 2m, thickness 1.2mm, material is PVC / TPU mesh fabric, full load weight 150t); at the same time, the maximum stacking height of the water bags is limited to ≤X meters (X is determined according to the load-bearing capacity of the support, usually ≤2m) to avoid local overpressure;

[0092] (3) Draw construction drawings, including a plan view of the water bag layout, detailed reinforcement drawings, a three-dimensional view of the water supply pipeline, and a loading sequence diagram:

[0093] Water bag layout plan:

[0094] Label each water bag with its number, positioning dimensions (longitudinal along beam length, transverse along beam width) and spacing, and reserve space for water pump installation;

[0095] Detailed reinforcement diagram:

[0096] Clearly define the details of the anti-slip pad layer at the bottom of the water bag (such as bamboo plywood) and the lateral restraint components (∠50×5 angle steel limit frame);

[0097] 3D diagram of water supply pipeline:

[0098] Distinguish between the elevations of main pipes (diameter ≥ 100 mm) and branch pipes (diameter ≥ 50 mm), mark the pipe diameter specifications, and install elastic supports for vibration damping between the water pipes and the support structure;

[0099] Loading sequence diagram:

[0100] Use arrows of different colors to indicate the order of water injection (adjacent water bag groups are symmetrically and alternately injected), and indicate the adjustment parameters of the flow control valve (such as initial flow rate 0.5~2L / min).

[0101] On-site construction preparation specifically includes:

[0102] (1) Check the step distance, row distance, diagonal bracing arrangement and top support tightness of the full-span scaffolding, and confirm that the bottom formwork is erected according to the pre-camber design; check the foundation compaction and drainage system (such as drainage ditch slope ≥2%) to prevent foundation settlement caused by rain erosion.

[0103] (2) Clean the surface of the bottom formwork and remove sharp objects (such as steel bar ends and bolts); wrap the protruding components that cannot be removed with soft cloth and lay bamboo plywood isolation layer; seal the gaps at the joints of the formwork (fill with sandbags or soft cloth) to prevent water from seeping into the foundation of the support;

[0104] (3) Clear the traffic passage on the side of the support (width ≥ 1.2m) to ensure smooth transportation of equipment such as water bags and water pumps;

[0105] S2. Laying and reinforcement of the rubber-plastic capsule, as detailed below:

[0106] S201. According to the water bag layout plan, pop up the water bag placement edge line on the bottom mold, mark the position according to the number, and ensure that the distance deviation between adjacent water bags is ≤50mm.

[0107] S202. Water bags are placed sequentially from the low end to the high end along the longitudinal slope of the box girder, ensuring that the water bag outlet faces the low end (for easy drainage) and the water inlet faces the high end (for easy water filling); each water bag is connected to the water pump through an independent water supply pipeline, and the pipe fitting interface is sealed with a sealing ring, with ≥300mm of maintenance space reserved.

[0108] S203, Specialized reinforcement (for longitudinal slope > 5% or transverse slope > 3%), the steps are as follows:

[0109] (1) Set a ∠50×5 angle steel limit frame along the circumference of the water bag and anchor it to the bottom formwork with M12 chemical anchor bolts (anchor bolt depth ≥100mm). The inner side of the angle steel is lined with a 10mm thick EVA buffer pad to prevent the water bag from being damaged by rigid friction with the angle steel.

[0110] (2) A cross-binding system is formed by using 10mm diameter synthetic fiber rope (breaking tensile strength ≥5kN), and the two ends of the fiber rope are connected to pre-embedded lifting rings (spacing ≤2m) and tensioned;

[0111] (3) Vertical poles (spacing ≤ 1.5m) are fabricated using [10 channel steel at the flange plates on both sides of the box girder, and dense mesh netting (mesh size ≤ 50mm) is installed to block them, leaving a 1m wide pedestrian passage;

[0112] S204. Perform graded pressure testing according to GB / T19624 standard. Inflate the water bag to 0.02MPa, maintain the pressure for 30 minutes, and apply soap solution to the seam. If there are no bubbles, the initial inspection is qualified. Continue to inflate to 0.15MPa, maintain the pressure for 1 hour, and use a laser diameter gauge to measure the diameter change of the water bag. If the diameter shrinkage rate is ≤1.5%, the seal is qualified.

[0113] S3. Water source connection and intelligent control system setup, details are as follows:

[0114] S301. The hierarchical pipe network is constructed using a three-level pipe network system of "water pump → water distribution valve → water distribution bag → water bag". 2~3kW submersible pumps (flow rate 5~200m³ / h) are preferred and are placed at stable water sources (such as foundation pits, wells, and ponds). The main pipe uses steel wire hose (pressure resistance ≥0.6MPa), and the branch pipes use PVC pipes. All joints are fastened with hose clamps to prevent leakage.

[0115] S302, Intelligent Dual Closed-Loop Control Operation, details are as follows:

[0116] (1) Install an electronic pressure sensor (range 0~0.2MPa, accuracy ±0.5%FS) on the main inlet pipe and an electromagnetic flow meter (range 0~200m³ / h, accuracy ±2%) on the branch pipe. Connect the sensor signal to the PLC controller (with PID regulation function). The PLC is linked with the variable frequency water pump and electric regulating valve.

[0117] (2) Settings via HMI (Human Machine Interface):

[0118] Initial filling rate: 0.5~2L / min (adjust according to the water bag's impact resistance);

[0119] Pressure threshold: 80% of the design pre-pressure value (e.g., if the design pressure is 0.1 MPa, the threshold is set to 0.08 MPa).

[0120] Stability criteria: Pressure fluctuation ≤ ±1% and lasting for 5 minutes;

[0121] Safety pressure relief value: 110% of the design pressure (automatic valve shutdown and pump stop with audible and visual alarm in case of overpressure).

[0122] S303. Conduct a water flow test to verify that there is no leakage in the pipeline and that the inflation of each water bag is synchronized (inflation rate deviation ≤10%), and ensure that the pressure and flow control accuracy meets the set requirements.

[0123] S4. The layout of monitoring points and the determination of measurement methods are as follows:

[0124] S401, Construction of a three-dimensional monitoring network, including longitudinal monitoring sections and transverse monitoring points;

[0125] Longitudinal monitoring section:

[0126] Five monitoring sections were arranged along the span of the box girder, namely:

[0127] Section 1: End support area of ​​the clear span (1m from the center of the support);

[0128] The bending moment transition zone at section 2 / 4:1 / 4L (L is the span, located 10m from section 1 / 5).

[0129] Section 3: Maximum deformation zone at mid-span (L / 2);

[0130] Horizontal monitoring points:

[0131] Monitoring points are set up along a 5m module for each cross section, with key coverage areas:

[0132] Left flange cantilever section (0.5m from the beam edge);

[0133] The abrupt change zone of the lateral stiffness of the base plate (0.3m from each edge of the left and right base plates);

[0134] Neutral axis region of the cross section (at the beam width centerline);

[0135] Five monitoring points are set up for each section, located on the support foundation (ground) under the bottom plate and on the bottom formwork of the web plate. The monitoring points are located using a total station with a deviation of ≤2mm.

[0136] S402. Monitoring content and requirements include:

[0137] (1) Before loading: Determine the initial elevation of all monitoring points and establish a benchmark file; After each loading stage: Pause loading and monitor for 12 hours, and record the settlement; During the holding stage (after loading to 110%): Monitor daily at regular intervals (e.g., 8:00, 16:00) and record the 24h / 72h settlement; After unloading: 6 hours after unloading is completed, remeasure the elevation of each monitoring point and calculate the elastic deformation.

[0138] (2) After each loading stage: the average settlement of the monitoring points within 12 hours is ≤2mm before the next loading stage can be carried out; during the holding stage: the average settlement of the monitoring points for 24 consecutive hours is ≤1mm, or the average settlement for 72 consecutive hours is ≤5mm, the preloading is deemed qualified; if the settlement exceeds the limit, the loading should be stopped immediately, the support foundation or reinforcement measures should be checked, and the preloading should be restarted after rectification.

[0139] S403. Calculate the total deformation of the support based on the monitoring data, and set the pre-camber according to the formula:

[0140]

[0141] in The precamber value (mm) for a certain cross section; This represents the total pre-camber value at mid-span (mm). ; The distance (m) from a certain cross section to the beam end; The span of the beam is (m).

[0142] The elastic deformation due to the beam's own weight. This is the compression amount of the pad. For the deflection of the support, For inelastic deformation of the support, For the elastic deformation of the support, For foundation deformation;

[0143] S5. Graded water filling and preloading: Loading graded control and settlement observation operations are carried out separately. Settlement observation is carried out using an electronic level (accuracy ±0.1mm) to measure the elevation of each monitoring point in sequence according to the number. The data is recorded and the "Support Preloading Settlement Monitoring Record Form" is filled in. The contents include: measuring point number, initial value, current change, cumulative change, and warning status (the warning is triggered when the cumulative change is >5mm).

[0144] S6. Unloading and bottom mold adjustment, details are as follows:

[0145] S601. Following the principle of "last loading, first unloading, and layered symmetry", the unloading sequence adopts 110% total load, 80% total load, and 60% total load until the initial state; after each level of unloading is completed, the next level of unloading will be carried out only after the observation and recording are completed.

[0146] S602. After the pre-stressing is qualified, adjust the bottom formwork to the design elevation based on the pre-camber calculated from the monitoring data; after adjustment, re-measure the elevation. If the deviation is ≤3mm, it is qualified; otherwise, a second adjustment is required.

[0147] S7. Pre-pressurized water recovery, details are as follows:

[0148] S701. Excavate a temporary water pit (volume ≥ 1.2 times the total pre-pressurization water volume) at a distance of ≥ 5m outside the support red line, and lay a 0.5mm thick plastic film in the pit for seepage prevention;

[0149] S702. Open the water bag drain valve, pump water into the water pit, and then pump it to the project water storage tank (sealing ≥0.1MPa) for centralized storage. The water will be used for subsequent concrete curing or preloading of the next box girder, thus realizing the recycling of water resources.

[0150] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for staged water-filled preloading construction of a full-span scaffolding system for cast-in-place box girders with steep longitudinal and transverse slopes, characterized in that... Includes the following steps: S1. Construction preparation, which consists of technical construction preparation and on-site construction preparation; S2. Laying and reinforcement of the rubber-plastic capsule, as detailed below: S201. According to the water bag layout plan, pop up the water bag placement edge line on the bottom mold, mark the position according to the number, and ensure that the distance deviation between adjacent water bags is ≤50mm. S202. Water bags are placed sequentially from the low end to the high end along the longitudinal slope of the box girder, ensuring that the water bag outlet faces the low end and the water inlet faces the high end; each water bag is connected to the water pump through an independent water supply pipeline, and the pipe fitting interface is sealed with a sealing ring, with a maintenance space of ≥300mm reserved. S203, Specialized Reinforcement; S204. Perform graded pressure testing according to GB / T19624 standard. Inflate the water bag to 0.02MPa, maintain the pressure for 30 minutes, and apply soap solution to the seam. If there are no bubbles, the initial inspection is qualified. Continue to inflate to 0.15MPa, maintain the pressure for 1 hour, and use a laser diameter gauge to measure the diameter change of the water bag. If the diameter shrinkage rate is ≤1.5%, the seal is qualified. S3. Water source connection and intelligent control system setup, details are as follows: S301. The hierarchical pipe network is constructed using a three-level pipe network system of "water pump → water distribution valve → water distribution bag → water bag". A 2-3kW submersible pump is selected and placed at a stable water source. The main pipe uses steel wire hose and the branch pipes use PVC pipe. S302, Intelligent dual closed-loop control operation; S303. Conduct a water flow test to verify that there is no leakage in the pipeline and that the water bags are filled synchronously, ensuring that the pressure and flow control accuracy meets the set requirements. S4. The layout of monitoring points and the determination of measurement methods are as follows: S401, Construction of a three-dimensional monitoring network; S402. Monitoring Content and Requirements; S403. Calculate the total deformation of the support based on the monitoring data, and set the pre-camber according to the formula: in The precamber value (mm) for a certain cross section; This represents the total pre-camber value at mid-span (mm). ; The distance (m) from a certain cross section to the beam end; The span of the beam is (m). S5. Staged water filling and preloading, with staged loading control and settlement observation operations performed respectively; S6. Unloading and bottom mold adjustment, details are as follows: S601. Following the principle of "last loading, first unloading, and layered symmetry", the unloading sequence adopts 110% total load, 80% total load, and 60% total load until the initial state; after each level of unloading is completed, the next level of unloading will be carried out only after the observation and recording are completed. S602. After the pre-stressing is qualified, adjust the bottom formwork to the design elevation based on the pre-camber calculated from the monitoring data; after adjustment, re-measure the elevation. If the deviation is ≤3mm, it is qualified; otherwise, a second adjustment is required. S7. Pre-pressurized water recovery, details are as follows: S701. Excavate a temporary water pit at a distance of ≥5m outside the support red line, and lay a 0.5mm thick plastic film in the pit to prevent seepage. S702. Open the water bag drain valve, pump water into the water pit, and then pump it to the project water storage tank for centralized storage, which will be used for subsequent concrete curing or preloading of the next box girder.

2. The construction method according to claim 1, characterized in that, The technical construction preparation in step S1 includes: (1) Based on the combined values ​​of the self-weight of the reinforced concrete beam, the load of the formwork system, and the self-weight of the support in the design drawings, determine the design load value per square meter of the support area through structural verification. (Unit: kN / m) 2 ); based on the specific gravity of water Based on the formula Calculate the water bag filling height corresponding to the equivalent water load. (Unit: m); (2) Based on the converted filling height The dimensions of the rubber and plastic bladders were designed; at the same time, the maximum stacking height of the water bags was limited to ≤X meters (X is determined according to the load-bearing capacity of the support) to avoid local overpressure. (3) Draw construction drawings, including a plan view of the water bag layout, detailed reinforcement drawings, a three-dimensional view of the water supply pipeline, and a loading sequence diagram: Water bag layout plan: Label each water bag with its number, positioning dimensions, and spacing, and reserve space for water pump installation; Detailed reinforcement diagram: Clarify the details of the anti-slip pad layer at the bottom of the water bag and the details of the lateral restraint components; 3D diagram of water supply pipeline: Distinguish between the elevations of main pipes and branch pipes, mark the pipe diameter specifications, and install elastic supports for vibration damping between the water pipes and the support structure; Loading sequence diagram: Use arrows of different colors to indicate the sequence of water injection and specify the adjustment parameters of the flow control valve.

3. The construction method according to claim 1, characterized in that, The on-site construction preparation in step S1 specifically includes: (1) Check the step distance, row distance, diagonal bracing arrangement and top support tightness of the full-span scaffolding, and confirm that the bottom formwork is erected according to the pre-camber design; check the foundation compaction and drainage system to prevent foundation settlement caused by rain erosion. (2) Clean the surface of the bottom formwork and remove sharp objects; wrap the protruding components that cannot be removed with a soft cloth and lay a bamboo plywood isolation layer; seal the gaps at the joints of the formwork to prevent water from seeping into the foundation of the support; (3) Clear the traffic passage on the side of the support to ensure smooth transportation of water bags and water pump equipment.

4. The construction method according to claim 1, characterized in that, The specific reinforcement steps in step S203 are as follows: (1) Set a ∠50×5 angle steel limit frame along the circumference of the water bag and anchor it to the bottom mold with M12 chemical anchor bolts. A 10mm thick EVA buffer pad is attached to the inside of the angle steel to prevent the water bag from being damaged by rigid friction with the angle steel. (2) A cross-binding system is formed by using 10mm diameter synthetic fiber ropes, with pre-embedded lifting rings connected to both ends of the fiber ropes and tensioned; (3) Vertical poles are fabricated using [10 channel steel at the flange plates on both sides of the box girder, and dense mesh netting is installed to create a 1m wide pedestrian passage.

5. The construction method according to claim 1, characterized in that, The intelligent dual closed-loop control in step 302 is as follows: (1) Install an electronic pressure sensor on the main inlet pipe and an electromagnetic flow meter on the branch pipe. Connect the sensor signal to the PLC controller. The PLC is linked with the variable frequency water pump and the electric regulating valve respectively. (2) Set the following through the HMI human-machine interface: initial water filling speed is 0.5 to 2 L / min; pressure threshold is 80% of the design pre-pressure value; stability judgment condition is pressure fluctuation ≤ ±1% and lasts for 5 min; safety pressure relief value is 110% of the design pressure.

6. The construction method according to claim 1, characterized in that, The construction of the three-dimensional monitoring network in step S401 includes longitudinal monitoring sections and transverse monitoring points; Longitudinal monitoring section: Five monitoring sections were arranged along the span of the box girder, namely: Section 1: End support area of ​​the clear span (1m from the center of the support); The bending moment transition zone at section 2 / 4:1 / 4L (L is the span, located 10m from section 1 / 5). Section 3: Maximum deformation zone at mid-span (L / 2); Horizontal monitoring points: Monitoring points are set up along a 5m module for each cross section, with key coverage areas: Left flange cantilever section (0.5m from the beam edge); The abrupt change zone of the lateral stiffness of the base plate (0.3m from each edge of the left and right base plates); Neutral axis region of the cross section (at the beam width centerline); Five monitoring points are set up for each section, located on the support foundation under the bottom plate and on the bottom formwork of the web plate. The monitoring points are located using a total station with a deviation of ≤2mm.

7. The construction method according to claim 1, characterized in that, The monitoring content and requirements in step S402 include: (1) Before loading, measure the initial elevation of all monitoring points and establish a benchmark file; after each loading stage, pause loading and monitor for 12 hours and record the settlement; during the load holding stage, monitor at regular intervals every day and record the settlement for 24 hours / 72 hours; 6 hours after unloading, remeasure the elevation of each monitoring point and calculate the elastic deformation. (2) After each loading stage: the average settlement of the monitoring points within 12 hours is ≤2mm before the next loading stage can be started; during the holding stage: if the average settlement of the monitoring points is ≤1mm for 24 consecutive hours or ≤5mm for 72 consecutive hours, the preloading is deemed qualified; if the settlement exceeds the limit, the loading is stopped immediately, the foundation of the support or reinforcement measures are checked, and the preloading is restarted after rectification.

8. The construction method according to claim 1, characterized in that, In step S403 The elastic deformation due to the beam's own weight. This is the compression amount of the pad block. For the deflection of the support, For inelastic deformation of the support, For the elastic deformation of the support, This is due to foundation deformation.

9. The construction method according to claim 1, characterized in that, The loading hierarchy control in step S5 is specifically as follows: (1) Loading is performed in three stages to reach 110% of the total design load, with each stage of loading being 60%, 80%, and 110% of the total weight, respectively; (2) The loading sequence is longitudinal first and then transverse, with the load distributed symmetrically from the mid-span of the box girder to both ends; and the load is distributed symmetrically from the center line of the box girder to both sides. When loading, close the water bag drain valve, connect the water inlet valve through the fire pipe, start the submersible pump to inject water, and the PLC controller automatically controls the water inlet according to the set flow rate. A designated person inspects the pipeline sealing and the deformation of the water bag.

10. The construction method according to claim 1, characterized in that, In step S5, the settlement observation is performed by using an electronic level to measure the elevation of each monitoring point in sequence according to its number, and the data is recorded.

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