Prestressed concrete cast-in-situ steel box girder construction quality control method

Abstract

The application discloses a prestressed concrete cast-in-situ steel box girder construction quality control method, which comprises the following steps: distributing high-grade leveling base points on a pile foundation construction area and guiding secondary leveling base points to construct an elevation control network; then, a plane control network is constructed; pile foundation construction is completed according to the plane control network; according to the elevation control network and a reference axis of the pile foundation, a pile cap, a pier cap and a temporary support are successively poured above the pile foundation; a segmented steel box girder is hoisted onto the temporary support; and the segmented steel box girder is driven by synchronous linkage jacks to synchronously fall with a height difference and is supported on the support on the top surface of the pier cap. The pile foundation construction area is uniformly divided, the elevation and plane control networks are integrally constructed, and the pile foundation-pile cap-pier cap-steel box girder assembly girder falling process is implemented in succession. The method effectively improves the defects of insufficient component assembly precision and unbalanced stress conversion, reduces the construction quality risk of the joint part, and guarantees the overall structure forming quality and construction reliability of the interflow overpass.

Description

Technical Field

[0001] This invention relates to the field of steel box girder bridge construction technology, and in particular to a method for quality control in the construction of prestressed concrete cast-in-place steel box girders. Background Technology

[0002] Urban interchange bridges are key structural nodes in urban expressway networks, typically composed of multiple sections of cast-in-place prestressed box girders, steel box girders, multiple sets of piers and abutments, and numerous pile foundations. Constrained by site conditions in urban built-up areas, interchange structures are complex, with numerous spatial intersections, encompassing various structural forms such as underground pile foundations, above-ground piers and abutments, cast-in-place beam segments, and steel box girder segments. These projects are large-scale, with diverse structural types, and place high demands on spatial positioning accuracy, component assembly and matching effects, and the adaptability of connections between various structural parts, making them an important component of urban transportation infrastructure construction.

[0003] In existing technologies, different structural components of urban interchange bridges adopt independent operation modes during construction. The operations of various stages, such as surveying and layout, pile foundation, abutment, pier body, cast-in-place box girder and steel box girder assembly and placement, are scattered, which can easily lead to problems such as substandard assembly accuracy and uneven stress transfer, which is not conducive to ensuring the overall construction effect of the structure.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] To address the problems in existing technologies where different structural components operate independently during the construction of cast-in-place concrete box girders, resulting in fragmented operations across various stages such as surveying and layout, pile foundations, abutments, piers, cast-in-place box girders, and steel box girder assembly and placement, which can easily lead to substandard assembly accuracy and uneven stress transfer, this invention provides a method for quality control in the construction of prestressed concrete cast-in-place steel box girders.

[0006] This invention is achieved through the following technical solution: A method for quality control in the construction of prestressed concrete cast-in-place steel box girders, wherein the method includes: The pile foundation construction area was divided according to the on-site working conditions; A high-level leveling benchmark is selected in one of the construction areas, and secondary leveling benchmarks are established from the high-level leveling benchmark to the other construction areas to construct an elevation control network; plane coordinate control points are established at the locations of the high-level leveling benchmark to construct a plane control network; Based on the aforementioned plane control network and construction drawings, the pile positions are laid out and the pile foundation construction is completed; after the pile foundation is completed, the thickness of the sediment at the bottom of the pile, the strength of the concrete in the pile body, and the characteristics of the rock strata at the bottom of the pile are verified by core sampling. Based on the elevation control network and the reference axis of the pile foundation, the pile cap and pier are poured sequentially above the pile foundation, and temporary supports are erected at the joint positions of the segmental steel box girder segments. The segmental steel box girder is hoisted onto the temporary support; coarse matching of the interfaces of adjacent segmental steel box girders is carried out, including adjusting the slope of the girder segment, adjusting the height of the girder segment, and aligning the main web of the box girder opening of adjacent segmental steel box girders; fine matching of the interfaces of adjacent segmental steel box girders is carried out, adjusting the segment elevation, pre-camber, and cross slope in the order of hard constraints first and then weak constraints; after meeting the requirements, welding operations are carried out on adjacent segmental steel box girders; Synchronous linkage jacks are used to drive the segmental steel box girder to maintain synchronous height difference at each position, so that the segmental steel box girder falls and is supported on the support on the top surface of the pier; after the force conversion is completed, the temporary support is removed.

[0007] The aforementioned method for quality control of prestressed concrete cast-in-place steel box girder construction, wherein selecting a high-level leveling benchmark in one of the construction areas, and then extending secondary leveling benchmarks from the high-level leveling benchmark to the remaining construction areas to construct an elevation control network includes: The high-level leveling benchmarks are arranged in the central part of several construction areas. The secondary leveling benchmarks are evenly distributed along the steel box girder line in the remaining construction areas, with the distance between adjacent secondary leveling benchmarks not exceeding 100m.

[0008] The aforementioned method for quality control of prestressed concrete cast-in-place steel box girder construction, wherein the step of establishing a plane control network by setting up plane coordinate control points at the locations of the high-level benchmarks includes: A plane coordinate control point is set up every 50m along the location of the high-level leveling benchmark and the center line of the road. An additional plane coordinate control point is inserted at the intersection, and concrete protective piles are set at the plane coordinate control points. When the centerline of the road is curved, the tangent distance method is used to mark the points on the curved segment; the distance measurement accuracy is 1 / 2000, and the angle measurement is less than 20″.

[0009] The aforementioned method for quality control of prestressed concrete cast-in-place steel box girder construction, wherein the step of setting out pile positions and completing pile foundation construction based on the plane control network and construction drawings includes: Steel casing installation, rebar cage hoisting, guide pipe installation, secondary hole cleaning, and concrete pouring; The steel casing is made of 10mm steel plate, the steel casing is 3.0m high, the opening of the casing is 200mm above the ground and embedded 20cm into the original soil, and the space between the steel casing and the pit wall is filled with clay. The steel cage was tied into shape in three stages and hoisted and welded together in three stages. After the reinforcing cage is lowered and fixed in place, one of the aforementioned conduits is immediately installed. Before use, the conduit undergoes a watertight pressure test and a joint tensile test. The test pressure is not less than 1.5 times the pressure at the bottom of the hole. The length of the conduit lowered is such that the distance between the bottom of the conduit and the bottom of the hole is sufficient to allow the water-stop plug and concrete to be discharged smoothly.

[0010] The aforementioned method for quality control of prestressed concrete cast-in-place steel box girder construction, wherein the cast-in-place foundation includes: Site clearing and surveying were carried out. After the steel sheet piles are driven and the walers and internal supports are installed, the foundation pit is excavated in layers. After the foundation pit is leveled, the foundation concrete is poured. After the foundation reaches the design strength, the pile head breaking operation is carried out, and the pre-embedded steel bars and pre-embedded parts of the pier body are simultaneously pre-embedded.

[0011] The aforementioned method for quality control of prestressed concrete cast-in-place steel box girder construction, wherein the cast-in-place piers include: Large, modular steel formwork is selected and installed on the support platform; Concrete is poured into the steel formwork to form the pier, and the steel formwork is removed after the concrete reaches the demolding condition.

[0012] The aforementioned method for quality control of prestressed concrete cast-in-place steel box girder construction, wherein the step of performing coarse matching of interfaces on adjacent steel box girder segments includes: Control the bridge axis deviation of the segmental steel box girder to within ±2mm, the plate misalignment to be no more than 15mm, and the weld width deviation to be no more than 2mm; after adjustment, re-measure the elevation and the bridge axis of the segmental steel box girder.

[0013] The aforementioned method for quality control of prestressed concrete cast-in-place steel box girder construction includes, in part, fine-matching of interfaces between adjacent steel box girder segments: The height difference between the interface panels of adjacent steel box girder segments is controlled to be no more than 0.5mm; following the adjustment sequence of first hard constraints and then weak constraints, the height difference at the junction of the web plate and the top and bottom plates is first limited, and then the interface of the bottom plate, top plate, and cantilever plate is adjusted in sequence; the interface is fixed by using jacks and jack plates.

[0014] The aforementioned method for quality control of prestressed concrete cast-in-place steel box girder construction includes, in which synchronous linkage jacks are used to drive the segmental steel box girder to maintain synchronous height differences at each position, so that the segmental steel box girder falls and is supported on the supports on the top surface of the pier, comprising: The single beam drop distance is controlled to 10mm by the synchronous linkage jack. When the bottom of the beam is 50mm away from the top surface of the support, the beam drop is paused and a steel plate is added. The synchronization rate of the synchronous linkage jack is controlled at 5mm; stainless steel pads are added at locations where the bottom of the beam and the support cannot be closely fitted.

[0015] The aforementioned method for quality control of prestressed concrete cast-in-place steel box girder construction includes the use of a level instrument combined with an optical fiber sensor to monitor the entire process of lowering the segmental steel box girder. The monitoring content includes the mid-span vertical displacement and lateral displacement of the segmental steel box girder, as well as the bottom stress of the support.

[0016] The beneficial effects of this invention are as follows: Addressing the problem of fragmented construction operations across various stages of urban interchange bridge construction, this invention unifies the division of pile foundation construction areas and integrates an elevation and horizontal control network, enabling seamless implementation of the pile foundation-pier-steel box girder assembly and placement process. Core drilling is used to verify the quality of pile foundation formation; coarse and fine matching is implemented for the steel box girder assembly precision control; and synchronous jacks are used to control the descent attitude during the girder placement stage, with full-process monitoring. This effectively improves upon defects such as insufficient component assembly precision and uneven stress transfer, reduces construction quality risks at key points, and ensures the overall structural quality and construction reliability of the interchange. Attached Figure Description

[0017] Figure 1 This is a flowchart of the construction quality control method for prestressed concrete cast-in-place steel box girders according to the present invention; Figure 2 This is a schematic diagram of the pile foundation construction area division in the construction quality control method for prestressed concrete cast-in-place steel box girders of the present invention; Figure 3 This is a schematic diagram of the segmental construction of the prestressed concrete cast-in-place steel box girder according to the construction quality control method of the present invention; Figure 4 This is a schematic diagram of the segmental steel box girder hoisting in the invention of the prestressed concrete cast-in-place steel box girder construction quality control method.

[0018] exist Figures 1 to 4 In the middle: 10, pile foundation; 20, pile cap; 30, pier; 40, segmental steel box girder. Detailed Implementation

[0019] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0020] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0021] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0022] In existing technologies, different structural components of urban interchange bridges adopt independent operation modes during construction. The operations of various stages, such as surveying and layout, pile foundation, abutment, pier body, cast-in-place box girder and steel box girder assembly and placement, are scattered, which can easily lead to problems such as substandard assembly accuracy and uneven stress transfer, which is not conducive to ensuring the overall construction effect of the structure.

[0023] To address the aforementioned problems in the existing technology, this invention provides a method for quality control during the construction of prestressed concrete cast-in-place box girders, such as... Figure 1 As shown, the construction quality control method for this prestressed concrete cast-in-place box girder includes: S100. Divide the construction area of ​​pile foundation 10 according to the site conditions; S200. Select one of the construction areas and set up a high-level leveling benchmark. From the high-level leveling benchmark, transfer secondary leveling benchmarks to the other construction areas to construct an elevation control network. Set up plane coordinate control points at the locations of the high-level leveling benchmarks to construct a plane control network. S300. Based on the plane control network and construction drawings, the pile positions are laid out and the construction of pile foundation 10 is completed. After the pile foundation 10 is completed, the thickness of the sediment at the bottom of the pile, the strength of the concrete in the pile body, and the characteristics of the rock strata at the bottom of the pile are verified by core sampling. S400. Based on the elevation control network and the reference axis of the pile foundation 10, the pile cap 20 and the pier 30 are poured sequentially above the pile foundation 10, and temporary supports are erected at the segment interface of the segmental steel box girder 40. S500: Hoist the segmental steel box girder 40 onto the temporary support; perform coarse matching of the interfaces of adjacent segmental steel box girders 40, including adjusting the slope of the beam segment, adjusting the height of the beam segment, and aligning the main web plates of the box girder opening of adjacent segmental steel box girders 40; perform fine matching of the interfaces of adjacent segmental steel box girders 40, adjusting the segmental elevation, pre-camber, and cross slope in the order of first hard constraints and then weak constraints; after meeting the requirements, perform welding operations on adjacent segmental steel box girders 40; S600. Using synchronous linkage jacks, drive the segmental steel box girder 40 to maintain synchronous height difference at each position, so that the segmental steel box girder 40 falls and is supported on the support on the top surface of the pier 30; after the force conversion is completed, remove the temporary support.

[0024] In step S100 above, such as Figure 2 As shown, based on the overall layout of the urban interchange project and the distribution of existing buildings and underground pipelines around the site, the entire project is divided into several independent construction areas. Each area is reserved with operating space to meet the requirements of large hoisting equipment operation and material transfer and stacking, so as to avoid construction interference between different work surfaces.

[0025] In step S200 above, the unified establishment of a control network ensures consistency of measurement benchmarks across all construction areas at the overall project level, avoiding cumulative errors caused by independent benchmark establishment in each sub-project. During the actual establishment process, high-level leveling benchmarks are preferentially selected in the central part of the project site, in areas with stable geological conditions and unaffected by construction activities, to ensure the positional stability of the benchmarks themselves. Secondary leveling benchmarks are then established along the high-level leveling benchmarks to other construction areas, thus forming an elevation control network with the secondary leveling benchmarks. This elevation control network provides a unified elevation benchmark for all construction stages of the entire project. All elevation measurements for pile foundations 10, pile caps 20, piers 30, and steel box girder construction are based on the results of this elevation control network, avoiding deviations caused by multiple benchmarks.

[0026] The layout of the plane control network follows the same unified benchmark principle. Starting from the location of the high-level level benchmark, plane coordinate control points are laid out segment by segment along the center line of the road. All pile location layout and component positioning measurement are based on the coordinate parameters of this plane control network, which eliminates the systematic errors caused by independent measurements of different construction sub-sections from the source and ensures the spatial positioning accuracy of the overall structure.

[0027] Furthermore, the above-mentioned method of establishing an elevation control network by extending secondary leveling benchmarks from the high-level leveling benchmarks to the remaining construction areas includes: S210. Select the high-level leveling benchmarks located in the central part of several construction areas; S220. The secondary leveling benchmarks are evenly distributed along the steel box girder line in the remaining construction areas, and the distance between adjacent secondary leveling benchmarks is no more than 100m.

[0028] In this embodiment, placing high-level leveling benchmarks in the center of the construction area can shorten the transfer distance to secondary leveling benchmarks on both sides, further reducing the accumulation of errors during elevation transfer. The uniform distribution of secondary leveling benchmarks along the steel box girder line, with the spacing between adjacent secondary leveling benchmarks controlled to be no more than 100m, ensures that long-distance relocation is unnecessary when measuring elevations at each construction point. This improves the efficiency of on-site measurement operations and keeps the error of a single measurement within the allowable range, meeting the elevation accuracy requirements for urban interchange bridge construction.

[0029] Furthermore, the above-mentioned arrangement of plane coordinate control points at the locations of the high-level leveling benchmarks to construct a plane control network includes: S230. A plane coordinate control point is set up every 50m along the location of the high-level leveling benchmark and the center line of the road. The plane coordinate control point is added at the intersection and a concrete protective pile is set at the plane coordinate control point. S240. When the centerline of the road is a curve, the tangent distance method is used to mark the points on the curve segment; the distance measurement accuracy is 1 / 2000 and the angle measurement is less than 20″.

[0030] In this embodiment, a plane coordinate control point is set every 50m along the centerline of the road to ensure the accuracy requirements of the entire line construction positioning. The traffic flow at the level crossing is complex and there are many construction cross-operations. The additional plane coordinate control points can facilitate the measurement work of pile foundation 10, pier 30 and subsequent beam construction in the level crossing area, and avoid the conventional points being blocked by site piles or temporary facilities, which will affect the measurement. Setting concrete protective piles can avoid the disturbance of control points by construction activities, ensure the long-term stability of the control point position, and prevent the shift due to site rolling or mechanical collision, thus avoiding unnecessary errors in subsequent re-measurements from the root.

[0031] For curved road sections, the tangent distance method is used for point placement. By controlling the corresponding distance measurement accuracy and angle measurement deviation, it can meet the stringent requirements for planar coordinate accuracy in the positioning of curved components. It is suitable for the alignment design characteristics of urban interchanges with multiple turns and multiple curves. Specifically, the tangent distance method for point placement refers to the method of first measuring a specified distance on the tangent to determine the intersection point according to the curve design parameters, and then calculating the coordinate position of the corresponding curve point. This method is simple to operate, requires less calculation during on-site measurement, and can improve the efficiency of curved section measurement operations while ensuring point placement accuracy, thus meeting the needs of rapid measurement and positioning on engineering sites.

[0032] In step S300 above, the construction of pile foundation 10 is carried out strictly in accordance with the approved pile location layout results. During the drilling process, the drilling parameters are dynamically adjusted according to the geological characteristics to avoid the collapse of the hole wall due to excessive drilling speed. After the hole is completed, the first cleaning is carried out to remove loose soil and sediment at the bottom of the hole. After the steel cage and guide pipe are lowered, the second cleaning is carried out. The thickness of sediment at the bottom of the hole is measured again. Only after confirming that the thickness of sediment meets the design and specification requirements can the subsequent concrete pouring operation be carried out.

[0033] After the 10 piles are completed and the concrete reaches the specified strength, the quality of the piles is verified by core sampling. The thickness of the sediment at the bottom of the pile, the continuity and strength of the concrete in the pile body, and the characteristics of the bearing stratum rock at the bottom of the pile are tested to confirm that all parameters meet the design requirements. If problems such as excessive sediment thickness, insufficient pile strength, or bearing stratum not meeting the survey requirements are found, reinforcement is carried out in a timely manner according to the preset treatment plan. The construction quality is controlled from the foundation stage to avoid quality hazards such as excessive settlement after the superstructure is completed.

[0034] Specifically, the above-mentioned pile location layout and pile foundation 10 construction based on the aforementioned plane control network and construction drawings includes: S310, steel casing installation, rebar cage hoisting, guide pipe installation, secondary hole cleaning, and concrete pouring; The steel casing is made of 10mm steel plate, the steel casing is 3.0m high, the opening of the casing is 200mm above the ground and embedded 20cm into the original soil, and the space between the steel casing and the pit wall is filled with clay. The steel cage was tied into shape in three stages and hoisted and welded together in three stages. After the reinforcing cage is lowered and fixed in place, one of the aforementioned conduits is immediately installed. Before use, the conduit undergoes a watertight pressure test and a joint tensile test. The test pressure is not less than 1.5 times the pressure at the bottom of the hole. The length of the conduit lowered is such that the distance between the bottom of the conduit and the bottom of the hole is sufficient to allow the water-stop plug and concrete to be discharged smoothly.

[0035] In this embodiment, the steel casing can stabilize the soil around the borehole opening and prevent the opening from collapsing. At the same time, it plays a calibrating role in the positioning of the pile. The diameter, burial depth and planar position deviation of the steel casing are strictly controlled to ensure that its parameters meet the requirements of the construction specifications.

[0036] To ensure the overall quality and safety of the reinforcing cage during hoisting, the cage was tied and assembled in three stages, hoisted into place in three stages, and then welded together. This segmented fabrication and hoisting scheme is well-suited to the limited space of urban construction sites, eliminating the need for extensive whole-cage tying. Furthermore, segmented hoisting requires lower lifting heights for hoisting equipment, making it suitable for the limited equipment operating conditions in urban construction sites. During fabrication and installation, the main reinforcement joints were staggered according to regulations, and the fabrication process ensured accurate positioning of the main reinforcement. After the entire reinforcing cage was fabricated and passed self-inspection, it was submitted to the supervising engineer for inspection and approval. Then, it was hoisted into the pile hole and installed using a crane at the fabrication yard. Before installation, any adhering mud and oil stains should be removed to ensure a tight bond between the reinforcement and the concrete. During welding, the weld fullness must be strictly guaranteed, and the main reinforcement joints should be staggered to avoid an excessive number of joints on the same cross-section, which could affect the overall mechanical properties of the reinforcing cage.

[0037] The watertight pressure test and joint tensile test before the installation of the duct are crucial to ensuring the smooth implementation of underwater concrete pouring. These tests prevent problems such as water leakage and joint breakage during the pouring process. After the reinforcing cage is lowered and fixed in place, one duct is immediately installed. The duct is made of steel pipe with quick-connect threaded joints. Before use, the duct undergoes a watertight pressure test and joint tensile test. The test pressure is no less than 1.5 times the pressure at the bottom of the borehole. Then, it is hoisted and extended section by section using a truck crane, and lowered down. The lower end of the duct is 500mm from the bottom of the borehole. The patency of the guide pipe was tested using a secondary cleaning method employing air-lift reverse circulation. Air-lift reverse circulation cleaning utilizes compressed air from an air compressor, delivered to the pile hole through a duct installed inside the guide pipe. The high-pressure air mixes with the mud, forming a slurry-air mixture with a density less than the mud within the guide pipe. Due to its lower specific gravity, the slurry-air mixture rises, creating a negative pressure at the bottom of the mixer within the guide pipe. The mud below rises under this negative pressure, and with the combined effect of air pressure and momentum, it is continuously replenished. Once it reaches the mixer, the mud and air form an air-slurry mixture, continuing to rise and creating flow. Because the inner cross-sectional area of ​​the guide pipe is smaller than the annular cross-sectional area between the outer wall of the guide pipe and the pile wall, a reverse circulation with extremely high velocity and flow rate is formed, carrying sediment back out of the guide pipe. Strict control of the test pressure allows for early verification of the guide pipe's pressure-bearing capacity, ensuring its suitability for pouring operations at different pile depths. Controlling the distance between the bottom of the pipe and the bottom of the hole prevents either excessive distance leading to failure of the first batch of concrete sealing or insufficient distance leading to blockage of the guide pipe, ensuring the successful completion of the first batch of concrete pouring.

[0038] In step S400, based on the elevation control network and the reference axis of the pile foundation 10, the pile cap 20 and the pier 30 are poured sequentially above the pile foundation 10.

[0039] Specifically, the aforementioned cast-in-place foundation 20 includes: S411. Conduct site clearing and surveying; S412. After driving steel sheet piles and installing walers and internal supports, excavate the foundation pit in layers after the support is completed. S413. After the foundation pit is leveled, the foundation concrete is poured. After the foundation reaches the design strength, the pile head breaking operation is carried out, and the pre-embedded steel bars and pre-embedded parts of the pier body are pre-embedded at the same time.

[0040] In this embodiment, after site clearing, the outline and elevation of the pier cap 20 are precisely laid out according to the plane control network and elevation control network to provide a benchmark for subsequent foundation pit excavation. The construction steps for the pier cap 20 are: driving steel sheet piles and installing walers and internal supports, ensuring that the walers and internal supports are installed before excavation of the pier cap 20. After the foundation concrete reaches a certain strength, pile head breaking is carried out. The reinforcing steel for the pier cap 20 is centrally processed in the backyard and transported to the site in batches via access roads. A 25t truck crane is used for hoisting, and manual installation is completed. During the installation process, pre-embedded reinforcing steel and other pre-embedded parts are embedded in the pier body. The formwork for the pier cap 20 uses large steel molds, with a height 20cm higher than the height of the pier cap 20, and is installed using a 25t truck crane. Concrete is transported to the pier location by concrete mixer truck via access roads and is hoisted by a truck crane or poured using a chute. The bridge abutment concrete is cured by covering it with geotextile fabric, and the curing time is no less than 7 days.

[0041] After the foundation is leveled and the cushion layer is poured, the construction base surface of the pile top can be adjusted to the design elevation. After breaking the loose and insufficient strength of the pile head concrete, it can be ensured that the pile body is firmly connected to the pile cap 20. The pre-embedded pier body steel bars and pre-embedded parts provide positioning and connection benchmarks for the subsequent construction of the pier cap 30, ensuring the accuracy and reliability of the connection between the upper and lower structures.

[0042] Furthermore, the aforementioned cast-in-place pier 30 includes: S421. Select large-block modular steel formwork and install the steel formwork on the foundation 20; S422. Pour concrete into the steel formwork to form the pier 30. Remove the steel formwork after the concrete reaches the demolding condition.

[0043] In this embodiment, the pier 30 formwork adopts large-block combined prefabricated steel formwork, with dimensions processed according to the design cross-section. Before processing, calculations are performed based on the concrete pouring speed and load to ensure the strength and rigidity of the formwork itself. The large-block combined prefabricated steel formwork has high overall rigidity and tight joints, resulting in a high degree of flatness and good appearance quality on the surface of the formed pier 30 concrete, meeting the appearance quality requirements of urban bridge piers 30 and conforming to the landscape effect requirements of municipal engineering. Before the formwork is installed, the construction base surface at the top of the pier 20 is cleaned and roughened, and the plane position and verticality of the pre-embedded steel bars in the pier body are corrected. Then, the formwork is installed according to the outline of the survey and layout. During the installation process, the overall verticality and top elevation of the formwork are strictly controlled. The position of the formwork is fixed by tie bolts and external diagonal braces to avoid problems such as formwork displacement and bulging during concrete pouring.

[0044] The concrete pouring adopts a layered vibration process, strictly controlling the thickness of each layer to ensure sufficient vibration and avoid appearance defects such as honeycomb and pitting caused by under-vibration or over-vibration. After the concrete reaches the demolding strength required by the design, the steel formwork is removed in the order of first supporting and then removing, and vice versa. During the removal process, avoid prying hard and damaging the concrete surface of the pier 30 to ensure that the dimensional accuracy and appearance quality of the formed pier 30 meet the design requirements.

[0045] Temporary supports provide temporary support for the interface matching and welding work of the segmental steel box girder 40, preventing positional displacement of the girder segments after hoisting and ensuring the accuracy of the interface matching work. Temporary supports are typically erected using standard steel pipe scaffolding. Before erection, the site is leveled and compacted, and steel pads are laid to distribute the stress on the bottom of the supports, preventing uneven settlement after erection and affecting the interface matching accuracy. After the supports are erected, adjustable top supports are installed at the top for adjusting the position during subsequent girder segment interface matching work, providing adjustment space for precision matching.

[0046] In step S500, as Figure 3 As shown, after the segmental steel box girder 40 is prefabricated and passes inspection at the prefabrication plant, it is transported to the construction site in batches by flatbed trucks. Then, a large truck crane is used to lift the segmental steel box girder 40 sequentially onto the adjustable top support of the temporary frame according to the preset lifting sequence. During the lifting process, the initial slope of the beam segment is controlled by adjusting the lifting point position to avoid the risk of the beam overturning during lifting and ensure the safety of the lifting operation. After the initial positioning of a single beam segment is completed, rough matching work is carried out on the interface of two adjacent segmental steel box girders 40 to be spliced. The overall slope and vertical height of the beam segments are adjusted sequentially, and then the main web plates of the box openings of the two segments are aligned so that the interface gap and misalignment initially meet the preset requirements for welding operations.

[0047] After the rough matching is completed and passes on-site inspection, the fine matching operation of the interface is carried out. Following the order of hard constraints first and then weak constraints, the vertical elevation, preset camber and cross slope of the segment are adjusted in sequence. During the adjustment process, the deviation of each parameter is checked simultaneously until all indicators meet the design and specification requirements. After the adjustment is in place, the adjacent interfaces are temporarily fixed by the clamping plate, and the web plate, top plate and bottom plate are welded in sequence according to the preset welding process. After the welding is completed, the weld is subjected to non-destructive testing to confirm that there are no defects such as pores and cracks inside the weld, and to ensure that the interface connection strength meets the design stress requirements.

[0048] Specifically, the above-mentioned coarse matching of interfaces between adjacent steel box girder segments 40 includes: Control the bridge axis deviation of the segmental steel box girder 40 to within ±2mm, the plate misalignment to be no more than 15mm, and the weld width deviation to be no more than 2mm; after adjustment, re-measure the elevation and the bridge axis of the segmental steel box girder 40.

[0049] In this embodiment, coarse matching mainly involves adjusting the box girder alignment to ensure the centerline. The adjustment procedure is as follows: adjust the slope and height of the beam segment to make the centerline area of ​​the top plate basically aligned, and connect the bolts of the matching parts on both sides of the centerline; adjust the height of the beam segment to make the U-shaped ribs of the top plate aligned, and at the same time measure the elevation of the front and rear points of the hoisted beam segment to meet the design requirements; check whether the gap of the bottom plate of the beam segment is close to the pre-assembly condition (the matching parts are tightly fitted or the welding gap is no more than 15mm; if there is a contradiction between the elevation of the main control point and the matching of the interface bottom plate, they are mutually matched while taking into account the alignment and welding gap); use jacks to make the main web of the box girder to be matched aligned; after the elevation is re-measured and found to be qualified, connect the other matching parts and measure the bridge axis.

[0050] Furthermore, the aforementioned fine-tuning of the interfaces of adjacent steel box girder segments 40 includes: The height difference between the interface panels of adjacent steel box girder segments 40 is controlled to be no more than 0.5mm. Following the adjustment sequence of hard constraints first, then weak constraints, the height difference at the junction of the web and the top and bottom plates is limited first, followed by the adjustment of the interfaces of the bottom plate, top plate, and cantilever plate. Jacks are used in conjunction with support plates to fix the interfaces. In this embodiment, the precision matching process, by controlling the height difference of the interface panels, ensures the smoothness of the overall alignment after the splicing of adjacent beam segments, avoiding step-like deviations at the splicing position that would affect the overall stress and appearance of the beam. Adjusting the height difference at the junction of the web and the top and bottom plates first, and then proceeding with the splicing of other parts, prioritizes locking the key constraint positions of the beam interfaces, preventing overall positional shifts after local adjustments, and improving the efficiency and accuracy of the matching adjustment. Using jacks in conjunction with support plates to fix the interfaces ensures that the adjusted interface positions will not shift, providing stable constraints for subsequent welding operations, preventing interface position misalignment due to stress release during welding, and ensuring that the final splicing accuracy meets design requirements.

[0051] In step S600 above, such as Figure 4 As shown, after all the steel box girder segments 40 are spliced ​​and pass the overall acceptance, the beam lowering operation begins. The beam lowering operation adopts a control method of synchronous lifting and lowering of multiple synchronous linkage jacks. The stroke of each jack is synchronously adjusted through the automatic control system to ensure that the steel box girder segments 40 maintain synchronous height difference at all positions, and to avoid the beam from twisting and deforming due to uneven stress during the lowering process.

[0052] The beam lowering process is controlled according to the principle of graded uniform descent. The elevation deviation of each support point of the beam and the stress on the top of the pier 30 are detected simultaneously. The descent continues only after all parameters are confirmed to be normal, until the segmental steel box girder 40 is accurately placed on the pre-set support on the top surface of the pier 30, completing the transformation of the entire stress system from temporary support to permanent support.

[0053] After the stress conversion is completed, the overall alignment of the beam, the elevation of each support point, and the support deviation are checked again. Once all parameters are confirmed to meet the design requirements, the adjustable top support, scaffolding pipe, base and other components of the temporary support can be removed in sequence. The removal process follows the principle of removing from top to bottom and layer by layer. The removed components are classified and transported to the designated stacking area to avoid occupying the construction site and affecting the subsequent operation.

[0054] This construction method effectively solves the problems of poor construction accuracy and difficulty in quality control caused by limited site, complex alignment, and multiple work surfaces in urban interchange projects through unified quality control throughout the entire process from the layout of the measurement control network to the pile foundation, substructure, and splicing and placement of the upper steel box girder. It can ensure the construction quality of steel box girder bridges under the condition of small construction sites in urban areas, with higher overall construction efficiency and more precise quality control.

[0055] Specifically, the above-mentioned method of using synchronous linkage jacks to drive the segmental steel box girder 40 to maintain synchronous height differences at each position, so that the segmental steel box girder 40 falls and is supported on the support on the top surface of the pier 30 includes: S610. The single beam drop distance of the synchronous linkage jack is controlled to be 10mm. When the bottom of the beam is 50mm away from the top surface of the support, the beam drop is paused and a steel plate is added. The synchronization rate of the synchronous linkage jack is controlled to be 5mm. Stainless steel pads are added at the positions where the bottom of the beam cannot be closely attached to the support.

[0056] In this embodiment, strict control over the single beam drop distance and synchronization rate ensures a smooth and controllable beam drop process, preventing additional stress and damage to the beam structure caused by inconsistent drop rates at different locations. Pausing the beam drop and adding shims when the bottom of the beam is 50mm from the top surface of the support facilitates final adjustments and checks of each support point, ensuring accurate beam positioning. Stainless steel shims are added to areas where close contact is impossible, eliminating gaps and ensuring uniform load distribution to the supports and piers, preventing uneven stress distribution and guaranteeing that the beam's long-term load-bearing performance meets design requirements.

[0057] In another embodiment of the present invention, the entire process of lowering the above-mentioned segmental steel box girder 40 is monitored using a level instrument combined with optical fiber sensors. Specifically, after each stage of lowering is completed, the elevation data of each support point is checked point by point using a level instrument, while the internal stress data of the girder collected by the optical fiber sensors is read. The main monitoring contents are: vertical displacement and lateral displacement of the box girder at mid-span, stress at mid-span and bottom of the support, etc. The purpose of monitoring is to control the uniformity of the displacement of the steel box girder during the lowering process, keep the stress at each support basically consistent with the design, and record the stress transformation process of the box girder. In real time, it is judged whether the stress on the girder is within the design allowable range during the lowering process. If the monitoring finds that the stress or elevation deviation exceeds the preset threshold, the lowering operation is immediately suspended, the cause of the deviation is investigated and the lifting parameters of the jacks are adjusted, and then the subsequent lowering operation is continued. This monitoring method combines the intuitiveness of traditional elevation measurement with the continuity of real-time monitoring via fiber optic sensing. It can comprehensively control the beam's condition during the beam lowering process, further improving the safety and accuracy of the beam lowering operation and avoiding quality problems such as beam damage caused by blind construction.

[0058] In summary, this invention provides a method for quality control during the construction of prestressed concrete cast-in-place steel box girders, which includes: S100. Divide the construction area of ​​pile foundation 10 according to the site conditions; S200. Select one of the construction areas and set up a high-level leveling benchmark. From the high-level leveling benchmark, transfer secondary leveling benchmarks to the other construction areas to construct an elevation control network. Set up plane coordinate control points at the locations of the high-level leveling benchmarks to construct a plane control network. S300. Based on the plane control network and construction drawings, the pile positions are laid out and the construction of pile foundation 10 is completed. After the pile foundation 10 is completed, the thickness of the sediment at the bottom of the pile, the strength of the concrete in the pile body, and the characteristics of the rock strata at the bottom of the pile are verified by core sampling. S400. Based on the elevation control network and the reference axis of the pile foundation 10, the pile cap 20 and the pier 30 are poured sequentially above the pile foundation 10, and temporary supports are erected at the segment interface of the segmental steel box girder 40. S500: Hoist the segmental steel box girder 40 onto the temporary support; perform coarse matching of the interfaces of adjacent segmental steel box girders 40, including adjusting the slope of the beam segment, adjusting the height of the beam segment, and aligning the main web plates of the box girder opening of adjacent segmental steel box girders 40; perform fine matching of the interfaces of adjacent segmental steel box girders 40, adjusting the segmental elevation, pre-camber, and cross slope in the order of first hard constraints and then weak constraints; after meeting the requirements, perform welding operations on adjacent segmental steel box girders 40; S600. Using synchronous linkage jacks, drive the segmental steel box girder 40 to maintain synchronous height difference at each position, so that the segmental steel box girder 40 falls and is supported on the support on the top surface of the pier 30; after the force conversion is completed, remove the temporary support.

[0059] This invention addresses the problem of fragmented construction operations in various stages of urban interchange bridge construction. It achieves seamless implementation of the pile foundation-pier-steel box girder assembly and placement process by uniformly dividing the pile foundation construction area and constructing an integrated elevation and horizontal control network. Core drilling is used to verify the quality of the pile foundation, and coarse and fine matching is implemented for the steel box girder assembly precision control. During the girder placement stage, synchronous jacks are used to control the descent attitude and the entire process is monitored. This effectively improves the defects of insufficient component assembly precision and uneven stress transfer, reduces construction quality risks at key points, and ensures the overall structural quality and construction reliability of the interchange.

[0060] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for quality control in the construction of prestressed concrete cast-in-place steel box girders, characterized in that, The construction quality control methods for prestressed concrete cast-in-place steel box girders include: The pile foundation construction area was divided according to the on-site working conditions; A high-level leveling benchmark is selected in one of the construction areas, and secondary leveling benchmarks are established from the high-level leveling benchmark to the other construction areas to construct an elevation control network; plane coordinate control points are established at the locations of the high-level leveling benchmark to construct a plane control network; Based on the aforementioned plane control network and construction drawings, the pile positions are laid out and the pile foundation construction is completed; after the pile foundation is completed, the thickness of the sediment at the bottom of the pile, the strength of the concrete in the pile body, and the characteristics of the rock strata at the bottom of the pile are verified by core sampling. Based on the elevation control network and the reference axis of the pile foundation, the pile cap and pier are poured sequentially above the pile foundation, and temporary supports are erected at the joint positions of the segmental steel box girder segments. The segmental steel box girder is hoisted onto the temporary support; coarse matching of the interfaces of adjacent segmental steel box girders is carried out, including adjusting the slope of the girder segment, adjusting the height of the girder segment, and aligning the main web of the box girder opening of adjacent segmental steel box girders; fine matching of the interfaces of adjacent segmental steel box girders is carried out, adjusting the segment elevation, pre-camber, and cross slope in the order of hard constraints first and then weak constraints; after meeting the requirements, welding operations are carried out on adjacent segmental steel box girders; Synchronous linkage jacks are used to drive the segmental steel box girder to maintain synchronous height difference at each position, so that the segmental steel box girder falls and is supported on the support on the top surface of the pier; after the force conversion is completed, the temporary support is removed.

2. The method for quality control of prestressed concrete cast-in-place steel box girder construction according to claim 1, characterized in that, The step of selecting one of the construction areas to establish a high-level leveling benchmark, and then using this high-level leveling benchmark to establish secondary leveling benchmarks in the remaining construction areas to construct an elevation control network includes: The high-level leveling benchmarks are arranged in the central part of several construction areas. The secondary leveling benchmarks are evenly distributed along the steel box girder line in the remaining construction areas, with the distance between adjacent secondary leveling benchmarks not exceeding 100m.

3. The method for quality control of prestressed concrete cast-in-place steel box girder construction according to claim 1, characterized in that, The step of establishing a plane control network by setting up plane coordinate control points based on the locations of the high-level leveling benchmarks includes: A plane coordinate control point is set up every 50m along the location of the high-level leveling benchmark and the center line of the road. An additional plane coordinate control point is inserted at the intersection, and concrete protective piles are set at the plane coordinate control points. When the centerline of the road is curved, the tangent distance method is used to mark the points on the curved segment; the distance measurement accuracy is 1 / 2000, and the angle measurement is less than 20″.

4. The method for quality control of prestressed concrete cast-in-place steel box girder construction according to claim 1, characterized in that, The step of setting out pile locations and completing pile foundation construction based on the plane control network and construction drawings includes: Steel casing installation, rebar cage hoisting, guide pipe installation, secondary hole cleaning, and concrete pouring; The steel casing is made of 10mm steel plate, the steel casing is 3.0m high, the opening of the casing is 200mm above the ground and embedded 20cm into the original soil, and the space between the steel casing and the pit wall is filled with clay. The steel cage was tied into shape in three stages and hoisted and welded together in three stages. After the reinforcing cage is lowered and fixed in place, one of the aforementioned conduits is immediately installed. Before use, the conduit undergoes a watertight pressure test and a joint tensile test. The test pressure is not less than 1.5 times the pressure at the bottom of the hole. The length of the conduit lowered is such that the distance between the bottom of the conduit and the bottom of the hole is sufficient to allow the water-stop plug and concrete to be discharged smoothly.

5. The method for quality control of prestressed concrete cast-in-place steel box girder construction according to claim 1, characterized in that, The foundation to be cast includes: Site clearing and surveying were carried out. After the steel sheet piles are driven and the walers and internal supports are installed, the foundation pit is excavated in layers. After the foundation pit is leveled, the foundation concrete is poured. After the foundation reaches the design strength, the pile head breaking operation is carried out, and the pre-embedded steel bars and pre-embedded parts of the pier body are simultaneously pre-embedded.

6. The method for quality control of prestressed concrete cast-in-place steel box girder construction according to claim 5, characterized in that, The piers to be poured include: Large, modular steel formwork is selected and installed on the support platform; Concrete is poured into the steel formwork to form the pier, and the steel formwork is removed after the concrete reaches the demolding condition.

7. The method for quality control of prestressed concrete cast-in-place steel box girder construction according to claim 1, characterized in that, The coarse matching of interfaces for adjacent steel box girder segments includes: Control the bridge axis deviation of the segmental steel box girder to within ±2mm, the plate misalignment to be no more than 15mm, and the weld width deviation to be no more than 2mm; after adjustment, re-measure the elevation and the bridge axis of the segmental steel box girder.

8. The method for quality control of prestressed concrete cast-in-place steel box girder construction according to claim 7, characterized in that, The fine matching of interfaces for adjacent steel box girder segments includes: The height difference between the interface panels of adjacent steel box girder segments is controlled to be no more than 0.5mm; following the adjustment sequence of first hard constraints and then weak constraints, the height difference at the junction of the web plate and the top and bottom plates is first limited, and then the interface of the bottom plate, top plate, and cantilever plate is adjusted in sequence; the interface is fixed by using jacks and jack plates.

9. The method for quality control of prestressed concrete cast-in-place steel box girder construction according to claim 1, characterized in that, Using synchronous linkage jacks to drive the segmental steel box girder to maintain synchronous height differences at each position, so that the segmental steel box girder falls and is supported on the supports on the top surface of the pier, includes: The single beam drop distance is controlled to 10mm by the synchronous linkage jack. When the bottom of the beam is 50mm away from the top surface of the support, the beam drop is paused and a steel plate is added. The synchronization rate of the synchronous linkage jack is controlled at 5mm; stainless steel pads are added at locations where the bottom of the beam and the support cannot be closely fitted.

10. The method for quality control of prestressed concrete cast-in-place steel box girder construction according to claim 1, characterized in that, The entire process of lowering the segmental steel box girder was monitored using a level instrument combined with a fiber optic sensor. The monitoring content includes the mid-span vertical displacement and lateral displacement of the segmental steel box girder, as well as the bottom stress of the support.

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