Prestressed uhpc flexural strengthening structure in negative moment region of concrete bridge deck and design and construction method thereof

Abstract

This invention provides a prestressed UHPC flexural reinforcement structure for the negative bending moment zone of a concrete bridge deck. It includes prestressed steel strands laid on the concrete bridge deck, a UHPC reinforcement layer cast into the concrete bridge deck and bonded to the prestressed steel strands to form an integral structure, a precast UHPC anchoring device, and a precast steel-UHPC turning device. The UHPC reinforcement layer is cast in place using quick-setting, shrinkage-reducing UHPC material and is reinforced with a toughening steel mesh. The precast steel-UHPC turning device redirects the prestressed steel strands from the upper edge to the lower edge of the concrete bridge deck. The prestressed steel strands are anchored to the lower edge of the concrete bridge deck by the precast UHPC anchoring device. The prestressed UHPC flexural reinforcement structure for the negative bending moment zone of a concrete bridge deck provided by this invention is convenient to construct, highly efficient in reinforcement, and has good durability. This invention also provides a design method and a construction method for the prestressed UHPC flexural reinforcement structure for the negative bending moment zone of a concrete bridge deck.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering technology, specifically to a prestressed UHPC flexural reinforcement structure for the negative bending moment zone of a concrete bridge deck, and its design and construction method. Background Technology

[0002] Due to environmental erosion, material aging, heavy / overloading, low concrete strength, and poor construction quality, many serious defects have appeared in my country's highway bridges. As a crucial component directly bearing wheel loads, the bridge deck is particularly vulnerable to these defects. On the one hand, under negative bending moments, the concrete bridge deck at the pier top is prone to cracking, water seepage, and joint damage. On the other hand, under complex external environmental factors, cracked bridge decks suffer from durability problems due to chloride ion penetration, concrete carbonation, and corrosion by harmful substances. Therefore, to ensure the normal and safe operation of bridge structures and extend their durability and service life, reinforcement and repair of bridge decks in the negative bending moment zone are essential.

[0003] Traditional methods for strengthening concrete bridges against bending include: ① Adhesive reinforcement (steel plates, FRP sheets) which are lightweight, high-strength, and have good crack resistance; however, they have poor high-temperature resistance and durability, and the organic adhesive at the interface is prone to aging, leading to peeling of the reinforcement layer. At the same time, stress lag results in a low utilization rate of the high-strength performance of the reinforcement material. ② Prestressed reinforcement can fully utilize the high strength of materials, significantly improve the bending resistance and stiffness of the structure, and has high reinforcement efficiency. However, stress concentration occurs at the external prestressing anchor points, and the tendons have durability and vibration fatigue problems. Although the prestressed wire rope + mortar method partially solves the problems of external prestressed reinforcement, the mortar layer has limited tensile strength and poor toughness, posing a risk of bending cracking. Moreover, the bonding interface agent (organic material) between mortar and concrete will age and fail under alternating environmental conditions, causing mortar layer peeling and affecting reinforcement durability. ③ The simply supported to continuous reinforcement method uses internal force redistribution (increasing the negative bending moment at the support and reducing the positive bending moment at the mid-span) to improve the stress on the bridge, which can effectively improve the bridge load rating. However, practice shows that simply supported to continuous bridges often develop transverse cracks in the negative bending moment zone at the pier top (wet joint interface) during operation, leading to corrosion or even damage of the beam top reinforcement and prestressing tendons, posing a durability risk.

[0004] It is evident that while commonly used methods for reinforcing concrete bridges with bending resistance are highly efficient, their durability is poor, and they cannot effectively protect against durability defects such as water leakage in concrete bridge decks and steel corrosion, making it difficult to meet the needs of durability reinforcement and renovation of deteriorated concrete bridges. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the shortcomings of existing concrete bridge deck reinforcement technologies and provide a prestressed UHPC (Ultra-High Performance Concrete) flexural reinforcement structure with convenient construction, high reinforcement efficiency, and good durability, as well as its design and construction method.

[0006] The technical solution of the present invention is as follows:

[0007] A prestressed UHPC flexural reinforcement structure for the negative bending moment zone of a concrete bridge deck includes prestressed steel strands laid on the concrete bridge deck, a UHPC reinforcement layer cast on the concrete bridge deck and bonded to the prestressed steel strands to form an integral structure, a precast UHPC anchoring device, and a precast steel-UHPC turning device. The UHPC reinforcement layer is cast in place using quick-setting, shrinkage-reducing UHPC material and is equipped with a toughened steel mesh. The precast steel-UHPC turning device enables the prestressed steel strands to turn from the upper edge to the lower edge of the concrete bridge deck. The prestressed steel strands are anchored to the lower edge of the concrete bridge deck by the precast UHPC anchoring device.

[0008] Furthermore, the concrete bridge deck is roughened, and bridge deck reinforcement is inserted into the roughened surface; prestressed steel strand groove channels for laying prestressed steel strands, steering device mounting grooves for installing precast steel-UHPC steering devices, and bridge deck prestressed steel strand holes for the prestressed steel strands to pass through the bridge deck are opened at the designed positions of the concrete bridge deck; steering device reinforcement holes are drilled at the steering device mounting grooves; and anchor bolt holes are drilled at the corresponding positions of the precast UHPC anchor devices.

[0009] Furthermore, the prestressed steel strands are configured according to the design load calculation, and the UHPC reinforcement layer is fixed to the concrete bridge deck through the bonding effect of new and old concrete and the rebar connection of the bridge deck.

[0010] Furthermore, the precast steel-UHPC steering device includes a precast UHPC steering block and a steering block stiffening steel plate covering the surface of the precast UHPC steering block; the precast UHPC steering block has pre-embedded steering device protruding reinforcing bars and has through holes for steering device prestressed steel strands, and the steering device protruding reinforcing bars are matched with the bridge deck steering device rebar anchoring holes; the steering block stiffening steel plate has a pre-reserved bevel.

[0011] Quick-setting anchoring adhesive is injected into the anchoring holes of the steering device in the concrete bridge deck. The protruding reinforcing bars of the steering device are then inserted into the anchoring holes. Finally, the stiffening steel plate of the steering block is welded to the reinforcing steel of the concrete bridge deck at the reserved bevel position to achieve the installation and fixation of the precast steel-UHPC steering device.

[0012] Furthermore, the prefabricated UHPC anchoring device includes a prefabricated UHPC anchoring block and a single-hole anchor. The prefabricated UHPC anchoring block has pre-drilled bolt holes, prestressed steel strand holes for the anchoring device, and a sealing groove. The single-hole anchor is used to anchor both ends of the prestressed steel strand to the steel pad of the prefabricated UHPC anchoring block. The prefabricated UHPC anchoring device is connected and fixed to the concrete bridge deck by high-strength bolts. The high-strength bolts are inserted into the bolt holes and extend to the anchoring device bolt holes in the bridge deck. The sealing groove is used to inject quick-setting UHPC grout after the prefabricated UHPC anchoring device is installed and fixed.

[0013] Furthermore, the rapid-setting, shrinkage-reducing UHPC material used in the UHPC reinforcement layer must have a compressive strength of more than 80% of the 28-day compressive strength at 3 days, and its self-shrinkage must be controlled within 300με; the toughening steel mesh uses HRB400 grade steel bars with a diameter range of Φ8~Φ12.

[0014] This invention also provides a design method for a prestressed UHPC flexural strengthening structure in the negative bending moment zone of a concrete bridge deck, comprising the following steps:

[0015] Step S1: Based on the original bridge structural design drawings and inspection reports, determine the cross-sectional dimensions, concrete strength, and reinforcement of the main beam support; calculate the design value of the bending moment at the main beam support section according to the specifications based on the proposed design load.

[0016] Step S2: Based on the original concrete bridge main beam support section dimensions, top slab thickness, and steel reinforcement protective layer thickness, preliminarily determine the thickness of the UHPC reinforcement layer and the quantity and area of ​​prestressed steel strands.

[0017] Step S3, internal force verification of the negative bending moment zone of prestressed UHPC flexural strengthening concrete bridge deck: internal force verification is performed according to the positive section bearing capacity of the flexural member to determine the cross-sectional area of ​​the prestressed steel strand;

[0018] Step S4: Based on the calculated area of ​​the prestressed steel strands, determine the size and quantity of the prestressed steel strands, and formulate a specific reinforcement scheme for the prestressed UHPC bending reinforcement structure in the negative bending moment zone of the concrete bridge deck.

[0019] Furthermore, in step S3, the flexural capacity of the prestressed UHPC flexural-strengthened concrete bridge deck flexural member is verified using the following formula:

[0020] Condition ①:

[0021] ;

[0022] If condition ① is met, the bearing capacity of the normal section shall be checked according to the following formula:

[0023] ;

[0024] Calculation of the height of the concrete compression zone:

[0025] ;

[0026] If condition ① is not met, the bearing capacity of the normal section shall be checked according to the following formula:

[0027] ;

[0028] Calculation of the height of the concrete compression zone:

[0029] ;

[0030] The height of the compression zone of concrete should meet the following conditions:

[0031] ;

[0032] In the formula:

[0033] —The importance factor of the bridge structure shall be adopted in accordance with the specifications;

[0034] —Design value of bending moment after component reinforcement;

[0035] —The strength utilization coefficient of the newly added prestressed steel strand is set at 0.9;

[0036] —Added design value for tensile strength of prestressed steel strand;

[0037] —Design value of axial tensile strength of UHPC;

[0038] —Design value of axial compressive strength of ordinary concrete in the original component;

[0039] —These are the design values ​​of the tensile strength of ordinary steel bars and prestressed steel bars in the tension zone of the original component, respectively;

[0040] —These are the design values ​​of the compressive strength of ordinary steel bars and prestressed steel bars in the compression zone of the original component, respectively;

[0041] —The stress of the prestressed steel bars when the normal stress of the concrete at the resultant point of the prestressed steel bars in the compression zone of the original component is equal to zero;

[0042] —Increased cross-sectional area of ​​prestressed steel strands;

[0043] —These represent the cross-sectional areas of the ordinary steel bars and prestressed steel bars in the tension zone of the original component, respectively;

[0044] —These represent the cross-sectional areas of the ordinary reinforcing bars and prestressed reinforcing bars in the compression zone of the original component, respectively;

[0045] —Height of the concrete compression zone;

[0046] —The relative height of the compression zone of the original component section;

[0047] —This refers to the width of a rectangular section or the thickness of the web in a T-shaped or I-shaped section;

[0048] —These represent the effective width and thickness of the compression flange for T-type or I-type cross-sections, respectively;

[0049] —These represent the width and thickness of the UHPC reinforcement layer section, respectively;

[0050] —These represent the total height of the reinforced section, the effective height of the reinforced section, and the effective height of the section before reinforcement, respectively.

[0051] —These are the distances from the resultant force points of ordinary steel bars and prestressed steel bars in the compression zone of the original member to the edge of the compression zone, respectively.

[0052] — The distance from the point of combined force of ordinary steel bars and prestressed steel bars in the compression zone of the original component to the edge of the compression zone.

[0053] This invention also provides a construction method for a prestressed UHPC flexural strengthening structure in the negative bending moment zone of a concrete bridge deck, comprising the following steps:

[0054] Step S1, concrete bridge deck interface treatment, is as follows:

[0055] The concrete bridge deck was roughened and reinforced with steel bars. Prestressed steel strand grooves and steering device installation grooves were opened, and prestressed steel strand ducts were drilled at the ends. The steering device installation grooves were roughened to expose the reinforcing steel bars in the concrete bridge deck, and rebar holes for the steering device were drilled. The concrete bridge deck anchorage device installation contact surface was treated, and prestressed steel strand ducts were opened at the designed locations and high-strength bolts were inserted.

[0056] Step S2, the installation and fixing of the precast steel-UHPC steering device and the precast UHPC anchoring device, are as follows:

[0057] Quick-setting anchoring adhesive is injected into the anchoring holes of the steering device in the concrete bridge deck, and the protruding reinforcing bars of the steering device are quickly inserted into the anchoring holes of the steering device. Then, the stiffening steel plate of the steering block is welded to the reinforcing steel of the concrete bridge deck at the reserved bevel position to realize the installation and fixation of the precast steel-UHPC steering device.

[0058] The pre-reserved bolt holes of the prefabricated UHPC anchor block are matched with the high-strength bolts inserted into the concrete bridge deck for positioning, and then the nuts are tightened to realize the installation and fixation of the prefabricated UHPC anchor device.

[0059] Step S3, tensioning and anchoring of prestressed steel strands, is as follows:

[0060] Prestressed steel strands are sequentially threaded into the groove channel of the prestressed steel strand, the prestressed steel strand duct of the steering device, the prestressed steel strand duct of the bridge deck, and the prestressed steel strand duct of the anchorage device.

[0061] Then, a small hydraulic jack is used to tension the prestressed steel strands to the control stress, which is 0.65 times the standard value of its tensile strength. The prestressed steel strands are tensioned symmetrically from the middle to both sides in the transverse direction of the concrete bridge deck. Single-hole anchorages are used to anchor both ends of the prestressed steel strands to the steel pads of the precast UHPC anchor blocks, and the exposed part of the prestressed steel strands is cut off.

[0062] After the tensioning and anchoring of the prestressed steel strands are completed, quick-setting UHPC grouting material is injected into the sealing groove to protect the anchor and prestressed steel strands from external environmental corrosion.

[0063] Step S4, UHPC reinforcement layer cast-in-place construction, details are as follows:

[0064] The contact surface between the concrete bridge deck and the UHPC reinforcement layer is moistened to make the ordinary concrete on the surface wet and saturated.

[0065] Erect the UHPC reinforcement layer formwork, arrange the toughening steel mesh, and then pour the UHPC reinforcement layer. The pouring sequence is as follows: first, inject UHPC mixture into the prestressed steel strand ducts of the anchoring device, the prestressed steel strand ducts of the steering device, and the prestressed steel strand ducts of the bridge deck, and then pour the UHPC reinforcement layer inside the formwork.

[0066] Step S5, UHPC reinforcement layer curing.

[0067] Furthermore, in step S5, after casting and molding, the UHPC reinforcement layer is sprayed with water and covered with a film for curing under natural curing conditions.

[0068] During the curing period, the surface of the UHPC reinforcement layer should be kept moist, and the temperature difference between it and the concrete bridge deck and the surrounding atmosphere should be less than or equal to 20℃ to avoid plastic shrinkage cracks in the UHPC reinforcement layer.

[0069] Once the UHPC reinforcement layer reaches the expected strength, the template is removed, and the UHPC reinforcement layer is bonded to the internal prestressed steel strands and toughened steel mesh to form a whole.

[0070] Compared with the prior art, the prestressed UHPC flexural strengthening structure for the negative bending moment zone of concrete bridge decks provided by this invention, as well as its design and construction method, have the following advantages:

[0071] I. Structural Stress: The prestressed UHPC flexural reinforcement structure for the negative bending moment zone of a concrete bridge deck, as described in this invention, organically combines prestressed reinforcement technology with UHPC reinforcement technology, leveraging their respective strengths. First, prestressed steel strands are tensioned and then anchored to the reinforced concrete bridge deck. Next, a UHPC reinforcement layer is poured, bonding the UHPC reinforcement layer to the prestressed steel strands to form a unified whole, sharing the load. Under the dual constraint of the prestressed steel strands and the UHPC reinforcement layer, the formation and propagation of cracks in the original damaged concrete bridge deck are significantly delayed. Simultaneously, thanks to the high strength of the prestressed steel strands and UHPC, the structural stiffness and load-bearing capacity are significantly enhanced, greatly improving the overall service performance and lifespan of the bridge.

[0072] II. Structural Durability: UHPC exhibits significantly superior durability compared to ordinary concrete, including resistance to water seepage, freeze-thaw cycles, and chemical corrosion. The UHPC reinforcement layer effectively protects itself (including the internal prestressed steel strands) and the original damaged concrete bridge deck from external environmental erosion, and addresses the common problem of cracking and water seepage in concrete bridge decks. Furthermore, UHPC demonstrates excellent adhesion to ordinary concrete; after roughening and rebar installation at the contact surface, its shear strength is further enhanced, preventing peeling failure of the reinforcement layer and ensuring reliable reinforcement durability.

[0073] III. Technical Applicability: The prestressed UHPC flexural reinforcement structure for the negative bending moment zone of concrete bridge decks of the present invention features convenient construction, high reinforcement efficiency, and good durability. Furthermore, the UHPC reinforcement layer has a small volume and light weight, minimizing its impact on the structure's self-weight. In addition, UHPC material has good workability and strong plasticity. Therefore, the prestressed UHPC flexural reinforcement structure is applicable to the reinforcement and renovation of the negative bending moment zone of concrete bridge decks with different degrees of deterioration, different external environments, and different structural forms, demonstrating strong applicability.

[0074] IV. Socioeconomic Benefits: Compared with bridge reconstruction, the use of prestressed UHPC flexural reinforcement structures for damaged concrete bridge decks can significantly reduce construction costs and carbon emissions, aligning with my country's dual-carbon policy and the concept of sustainable development in bridge engineering. Compared with other reinforcement technologies, prestressed UHPC flexural reinforcement structures can achieve integrated reinforcement of damaged concrete bridge deck structures and durability protection, eliminating the need for repeated reinforcement in the later stages, resulting in lower investment costs and maintenance expenses. Attached Figure Description

[0075] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0076] Figure 1 This is a schematic diagram of the prestressed UHPC flexural reinforcement structure for the negative bending moment zone of a concrete bridge deck according to the present invention.

[0077] Figure 2 for Figure 1 Schematic diagram of AA section in the middle;

[0078] Figure 3 Plan view of the interface treatment at the upper edge of the concrete bridge deck;

[0079] Figure 4 Plan view of the interface treatment at the lower edge of the concrete bridge deck;

[0080] Figure 5 This is a schematic diagram of the precast steel-UHPC steering device in this invention;

[0081] Figure 6 This is a schematic diagram of the installation of the precast steel-UHPC steering system;

[0082] Figure 7 This is a schematic diagram of the prefabricated UHPC anchoring device in this invention;

[0083] Figure 8 This is a schematic diagram of the installation of a prefabricated UHPC anchoring device.

[0084] Attached reference numerals: 1-Concrete bridge deck, 11-Roughened surface, 12-Bridge deck reinforcement, 13-Prestressed steel strand groove channel, 14-Boarding device mounting groove, 15-Bridge deck prestressed steel strand duct, 16-Reinforcing steel of concrete bridge deck, 17-Boarding device reinforcement hole, 18-Anchoring device bolt hole, 19-High-strength bolt.

[0085] 2-Reinforced structure;

[0086] 21-Prestressed steel strand;

[0087] 22-UHPC reinforcement layer;

[0088] 23-Precast UHPC anchoring device, 231-Precast UHPC anchoring block, 232-Single hole anchor, 233-Bolt duct, 234-Prestressed steel strand duct of anchoring device, 235-Sealing groove;

[0089] 24-Precast steel-UHPC steering device, 241-Precast UHPC steering block, 242-Steering block stiffening steel plate, 243-Extended reinforcing bar of steering device, 244-Through hole of prestressed steel strand of steering device, 245-Reserved bevel, 246-Bevel weld of steel plate-reinforcing bar;

[0090] 25-Toughened steel mesh. Detailed Implementation

[0091] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, and to make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described below.

[0092] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0093] The reinforcement structure of this invention is used to reinforce the negative bending moment zone of a concrete bridge deck. Please refer to the following references. Figures 1-8 The prestressed UHPC flexural reinforcement structure 2 for the negative bending moment zone of the concrete bridge deck of the present invention includes prestressed steel strands 21 laid on the bridge deck, a UHPC reinforcement layer 22 cast on the bridge deck and bonded to the prestressed steel strands to form an integral structure, a precast UHPC anchoring device 23, and a precast steel-UHPC turning device 24. The UHPC reinforcement layer 22 is cast in place using fast-setting and shrinkage-reducing UHPC material and is equipped with a toughening steel mesh 25. The precast steel-UHPC turning device 24 enables the prestressed steel strands to turn from the upper edge of the concrete bridge deck to the lower edge of the concrete bridge deck. The prestressed steel strands 21 are anchored to the lower edge of the concrete bridge deck by the precast UHPC anchoring device 23.

[0094] Before reinforcement, the upper edge of the concrete bridge deck 1 must undergo interface treatment. The treated concrete bridge deck includes a roughened surface 11 and bridge deck reinforcement 12 inserted into the roughened surface to improve the shear strength of the contact surface between the UHPC reinforcement layer 22 and the concrete bridge deck 1. At the same time, prestressed steel strand groove channels 13 for laying prestressed steel strands, steering device mounting grooves 14 for installing precast steel-UHPC steering devices, and bridge deck prestressed steel strand holes 15 for the prestressed steel strands to pass through the bridge deck must be opened at the designed locations on the concrete bridge deck 1.

[0095] The surface 11 is shallowly roughened to expose the ordinary concrete coarse aggregate of the concrete bridge deck 1. The mounting groove 14 of the steering device must be deeply roughened to expose the reinforcing steel bars 16 of the concrete bridge deck, and the anchoring holes 17 of the steering device are drilled to facilitate the welding, installation and fixing of the precast steel-UHPC steering device 24.

[0096] The lower edge of the concrete bridge deck 1 must be treated to remove broken concrete and debris from the contact surface of the precast UHPC anchoring device. Anchor bolt holes 18 are opened at the designed location. The precast UHPC anchoring device 23 is installed and fixed by inserting high-strength bolts 19 into the anchor bolt holes 18.

[0097] The prestressed steel strands 21 in the UHPC reinforcement layer 22 are configured according to the design load calculation. The UHPC reinforcement layer 22 is cast-in-place using quick-setting, shrinkage-reducing UHPC material and is reinforced with toughening steel mesh 25 to shorten the construction period, improve the tensile strength of the UHPC reinforcement layer 22, and avoid plastic shrinkage cracks in the UHPC reinforcement layer 22. Specifically, the compressive strength of the quick-setting, shrinkage-reducing UHPC at 3 days must reach more than 80% of the compressive strength at 28 days, and its autogenous shrinkage must be controlled within 300με. The toughening steel mesh 25 uses HRB400 grade steel bars with a diameter range of Φ8~Φ12. The UHPC reinforcement layer 22, prestressed steel strands 21, and toughening steel mesh 25 are bonded together to form a whole, and are connected and fixed to the concrete bridge deck 1 through the bonding effect of new and old concrete and the bridge deck reinforcement 12.

[0098] The prefabricated UHPC anchoring device 23 includes a prefabricated UHPC anchoring block 231 and a single-hole anchor 232. The prefabricated UHPC anchoring block 231 has reserved bolt holes 233, anchoring device prestressed steel strand holes 234 and anchor sealing grooves 235. The single-hole anchor 232 is used to anchor the two ends of the prestressed steel strand to the steel pad of the prefabricated UHPC anchoring block 231.

[0099] The precast UHPC anchoring device 23 is connected and fixed to the concrete bridge deck 1 by high-strength bolts 19, wherein the high-strength bolts 19 pass through the anchoring device bolt holes 18 in the concrete bridge deck and the bolt channels 233 reserved in the UHPC anchoring block 231. After the precast UHPC anchoring device 23 is installed and fixed, quick-setting UHPC grouting material is injected into the sealing groove.

[0100] The precast steel-UHPC steering device 24 includes a precast UHPC steering block 241 and a steering block stiffening steel plate 242 covering the surface of the precast UHPC steering block 241; wherein the precast UHPC steering block 241 has pre-embedded steering device protruding steel bars 243 and has through holes 244 for steering device prestressed steel strands, and the steering device protruding steel bars 243 are paired with steering device rebar anchoring holes 17 in the bridge deck; the steering block stiffening steel plate 242 has a pre-reserved bevel 245 to facilitate welding and fixing to the reinforcing steel bars 16 of the concrete bridge deck;

[0101] Quick-setting anchoring adhesive is injected into the anchoring holes of the steering device in the concrete bridge deck. The outward reinforcing bar 243 of the steering device is inserted into the anchoring hole 17 of the steering device. Then, the steering block stiffening steel plate 242 is welded to the reinforcing bar 16 of the concrete bridge deck at the reserved bevel position of the steering block stiffening steel plate to form a steel plate-reinforcing bar bevel weld, thereby realizing the installation and fixation of the precast steel-UHPC steering device.

[0102] The design method for the prestressed UHPC flexural strengthening structure in the negative bending moment zone of a concrete bridge deck according to the present invention includes the following steps:

[0103] Step S1: Based on the original bridge structural design drawings and inspection reports, determine the cross-sectional dimensions, concrete strength, and reinforcement of the main beam support; calculate the design value of the bending moment at the main beam support section according to the specifications based on the proposed design load.

[0104] Step S2: Based on the original concrete bridge main beam support section dimensions, top slab thickness, and steel reinforcement protective layer thickness, preliminarily determine the thickness of the UHPC reinforcement layer and the quantity and area of ​​prestressed steel strands.

[0105] Step S3, internal force verification of the negative bending moment zone of prestressed UHPC flexural strengthening concrete bridge deck: internal force verification is performed according to the positive section bearing capacity of the flexural member to determine the cross-sectional area of ​​the prestressed steel strand;

[0106] Specifically, the flexural bearing capacity of the prestressed UHPC flexural-strengthened concrete bridge deck members is verified using the following formula:

[0107] Condition ①:

[0108] ;

[0109] If condition ① is met, the bearing capacity of the normal section shall be checked according to the following formula:

[0110] ;

[0111] Calculation of the height of the concrete compression zone:

[0112] ;

[0113] If condition ① is not met, the bearing capacity of the normal section shall be checked according to the following formula:

[0114] ;

[0115] Calculation of the height of the concrete compression zone:

[0116] ;

[0117] The height of the compression zone of concrete should meet the following conditions:

[0118] ;

[0119] In the formula:

[0120] —The importance factor of the bridge structure shall be adopted in accordance with the specifications;

[0121] —Design value of bending moment after component reinforcement;

[0122] —The strength utilization coefficient of the newly added prestressed steel strand is set at 0.9;

[0123] —Added design value for tensile strength of prestressed steel strand;

[0124] —Design value of axial tensile strength of UHPC;

[0125] —Design value of axial compressive strength of ordinary concrete in the original component;

[0126] —These are the design values ​​of the tensile strength of ordinary steel bars and prestressed steel bars in the tension zone of the original component, respectively;

[0127] —These are the design values ​​of the compressive strength of ordinary steel bars and prestressed steel bars in the compression zone of the original component, respectively;

[0128] —The stress of the prestressed steel bars when the normal stress of the concrete at the resultant point of the prestressed steel bars in the compression zone of the original component is equal to zero;

[0129] —Increased cross-sectional area of ​​prestressed steel strands;

[0130] —These represent the cross-sectional areas of the ordinary steel bars and prestressed steel bars in the tension zone of the original component, respectively;

[0131] —These represent the cross-sectional areas of the ordinary reinforcing bars and prestressed reinforcing bars in the compression zone of the original component, respectively;

[0132] —Height of the concrete compression zone;

[0133] —The relative height of the compression zone of the original component section;

[0134] —This refers to the width of a rectangular section or the thickness of the web in a T-shaped or I-shaped section;

[0135] —These represent the effective width and thickness of the compression flange for T-type or I-type cross-sections, respectively;

[0136] —These represent the width and thickness of the UHPC reinforcement layer section, respectively;

[0137] —These represent the total height of the reinforced section, the effective height of the reinforced section, and the effective height of the section before reinforcement, respectively.

[0138] —These are the distances from the resultant force points of ordinary steel bars and prestressed steel bars in the compression zone of the original member to the edge of the compression zone, respectively.

[0139] — The distance from the point of combined force of ordinary steel bars and prestressed steel bars in the compression zone of the original component to the edge of the compression zone.

[0140] Step S4: Based on the calculated area of ​​the prestressed steel strands, determine the size and quantity of the prestressed steel strands, and formulate a specific reinforcement scheme for the prestressed UHPC bending reinforcement structure in the negative bending moment zone of the concrete bridge deck.

[0141] In a specific embodiment, a variable cross-section prestressed concrete continuous box girder bridge requires reinforcement design to upgrade its load rating to Highway Class I. The original main girder uses C50 concrete, with a support section height of 4m, a top slab width of 16m and a thickness of 300mm, a web width of 900mm, a bottom slab width of 8m and a thickness of 500mm, an effective section height of approximately 3.75m, and an effective bottom slab width calculated according to specifications of approximately 5.5m. The outermost layer of reinforcing steel has a protective layer thickness of 40mm. The design tensile strength of the prestressed steel strands in the tension zone is 1260MPa, and the total cross-sectional area is 35840mm². 2Under the most unfavorable combination of ultimate limit state of bearing capacity, the design value of the bending moment at the support section of the main beam is 190862.3 kN·m;

[0142] The design method for prestressed UHPC flexural strengthening structures in the negative bending moment zone of concrete bridge decks includes the following steps:

[0143] Step S1: Based on the original bridge structural design drawings and inspection reports, determine the cross-sectional dimensions, concrete strength, and reinforcement of the main beam support; calculate the design value of the bending moment at the main beam support section according to the specifications based on the proposed design load.

[0144] Original component concrete strength: C50, design value of axial compressive strength It is 22.4 MPa;

[0145] Original main beam support section dimensions: beam height 4m, top plate width 16m, thickness 300mm;

[0146] Original component reinforcement: Prestressed steel strand area in the tension zone is 35840 mm² 2 Tensile strength design value It is 1260 MPa;

[0147] Design value of bending moment at the support section: 244003.3 kN·m;

[0148] Step S2: Based on the original concrete bridge main beam support section dimensions, top slab thickness, and steel reinforcement protective layer thickness, preliminarily determine the UHPC reinforcement layer thickness and the number and area of ​​prestressed steel strands;

[0149] The top slab is 300mm thick, with an outermost steel reinforcement protective layer thickness of 40mm. The initial plan is for a 40mm groove depth for the prestressed steel strands. The UHPC reinforcement layer thickness is 20% of the top slab thickness, i.e., 60mm. Toughened UHPC with a steel fiber volume parameter of 3% is selected, with a design axial tensile strength of 6.7MPa. The top slab is 16m wide, with an internal box girder width of 6.2m and two side flanges totaling 8m. Four prestressed steel strands are arranged on average per meter of width, for a total of 56 prestressed steel strands. Low-relaxation prestressed steel strands with a nominal diameter of 15.2mm and a nominal area of ​​140mm² are selected. 2 The design value of tensile strength is It is 1260 MPa;

[0150] Step S3: Internal force verification in the negative bending moment zone of prestressed UHPC flexural strengthening concrete bridge deck: internal force verification is performed based on the positive section bearing capacity of the flexural member to determine the area of ​​the prestressed steel strands.

[0151] Verification of the bearing capacity of the normal section:

[0152] Condition ①:

[0153] ;

[0154] calculate:

[0155] ;

[0156] The calculation results meet condition ①, and the bearing capacity of the normal section is verified according to the following formula:

[0157] ;

[0158] calculate:

[0159] ;

[0160] The load-bearing capacity meets the requirements.

[0161] Calculation of the height of the concrete compression zone:

[0162] ;

[0163] get: The requirements are met.

[0164] S4. Based on the calculated area of ​​the prestressed steel strands, determine the size and quantity of the prestressed steel strands, and formulate a specific reinforcement plan for the prestressed UHPC bending reinforcement device in the negative bending moment zone of the concrete bridge deck.

[0165] The load-bearing capacity verification meets the design requirements. The thickness of the UHPC reinforcement layer in the prestressed UHPC bending reinforcement device in the negative bending moment zone of the concrete bridge deck can be designed as 60mm. The prestressed steel strands are 56 Φ15.2 low-relaxation prestressed steel strands, which are arranged in parallel inside the bridge deck. Among them, 24 strands can be arranged inside the box chamber and 32 strands can be arranged on both side flanges.

[0166] The construction method of the prestressed UHPC flexural strengthening structure for the negative bending moment zone of concrete bridge deck of the present invention includes the following steps:

[0167] Step S1, concrete bridge deck interface treatment, is as follows:

[0168] Interface treatment is performed on the contact surface between the concrete bridge deck 1 and the UHPC reinforcement layer 22, including roughening the concrete bridge deck and inserting bridge deck reinforcement bars, opening prestressed steel strand groove channels 13 and steering device installation grooves 14, and drilling bridge deck prestressed steel strand ducts 15 at the ends; the steering device installation groove 14 is deeply roughened to expose the concrete bridge deck reinforcing steel bars 16, and steering device reinforcement holes 17 are drilled; interface treatment is performed on the concrete bridge deck anchorage device installation contact surface, bridge deck prestressed steel strand ducts are opened at the designed positions, and high-strength bolts are inserted.

[0169] Step S2, the installation and fixing of the precast steel-UHPC steering device and the precast UHPC anchoring device, are as follows:

[0170] Quick-setting anchoring adhesive is injected into the anchoring hole 17 of the steering device in the concrete bridge deck, and the outward reinforcing bar 243 of the steering device is quickly inserted into the anchoring hole of the steering device. Then, the steering block stiffening steel plate is welded to the reinforcing bar of the concrete bridge deck at the reserved bevel position to form the steel plate-reinforcing bar bevel weld 246, thereby realizing the installation and fixation of the precast steel-UHPC steering device.

[0171] The pre-reserved bolt holes 233 of the prefabricated UHPC anchor block are matched with the high-strength bolts inserted into the concrete bridge deck for positioning, and then the nuts are tightened to realize the installation and fixation of the prefabricated UHPC anchor device.

[0172] Step S3, tensioning and anchoring of prestressed steel strands, is as follows:

[0173] Prestressed steel strands are sequentially threaded into the prestressed steel strand groove channel 13, the prestressed steel strand duct 244 of the steering device, the prestressed steel strand duct 15 of the bridge deck, and the prestressed steel strand duct 234 of the anchoring device.

[0174] Then, a small hydraulic jack is used to tension the prestressed steel strands to the control stress, which is 0.65 times the standard value of its tensile strength. The prestressed steel strands are tensioned symmetrically from the middle to both sides in the transverse direction of the concrete bridge deck. Single-hole anchorage 232 is used to anchor both ends of the prestressed steel strands to the steel pads of the precast UHPC anchorage blocks, and the exposed part of the prestressed steel strands is cut off.

[0175] After the tensioning and anchoring of the prestressed steel strands are completed, quick-setting UHPC grouting material is injected into the sealing groove to protect the anchor and prestressed steel strands from external environmental corrosion.

[0176] Step S4, UHPC reinforcement layer cast-in-place construction, details are as follows:

[0177] The contact surface between the concrete bridge deck and the UHPC reinforcement layer is moistened to make the ordinary concrete on the surface wet and saturated.

[0178] Erect the UHPC reinforcement layer formwork, arrange the toughening steel mesh, and then pour the UHPC reinforcement layer. The pouring sequence is as follows: first, inject UHPC mixture into the prestressed steel strand duct 234 of the anchoring device, the prestressed steel strand duct 244 of the steering device and the prestressed steel strand duct 15 of the bridge deck, and then pour the UHPC reinforcement layer inside the formwork.

[0179] Step S5, UHPC reinforcement layer curing, is detailed as follows:

[0180] After casting and molding, the UHPC reinforcement layer is cured by sprinkling water and covering it with a membrane under natural curing conditions;

[0181] During the curing period, the surface of the UHPC reinforcement layer should be kept moist, and the temperature difference between it and the concrete bridge deck and the surrounding atmosphere should be less than or equal to 20℃ to avoid plastic shrinkage cracks in the UHPC reinforcement layer.

[0182] After the UHPC reinforcement layer reaches the expected strength, the formwork is removed, and the UHPC reinforcement layer is bonded to the internal prestressed steel strands and toughened steel mesh to form a whole.

[0183] The prestressed UHPC flexural reinforcement structure for the negative bending moment zone of a concrete bridge deck of this invention organically combines prestressed active reinforcement technology and UHPC passive reinforcement technology. The use of prestressed steel strands significantly improves the stiffness and load-bearing capacity of the original structure and effectively restrains the further development of bridge deck damage cracks. The use of UHPC provides durable protection for the original concrete bridge deck structure, preventing further durability damage and deterioration. Simultaneously, UHPC protects the internal prestressed steel strands and reinforcement layer steel bars from external environmental corrosion, ensuring reliable and durable reinforcement. The use of prefabricated UHPC anchor blocks in this invention fully utilizes the ultra-high compressive strength of UHPC material, effectively mitigating stress concentration at the prestressed steel strand anchorage points. The prefabricated steel-UHPC turning blocks in this invention are small in size and easy to install, providing the necessary technical facilities for the prestressed steel strands anchored to the lower edge of the concrete bridge deck to change direction on the bridge deck.

[0184] This invention can overcome the technical bottlenecks of traditional bridge deck reinforcement methods in terms of reinforcement efficiency, durability and applicability. It can achieve efficient and durable integrated reinforcement of damaged bridge decks in the negative bending moment zone of concrete bridges, and can effectively solve problems such as bridge deck cracking and water seepage, steel corrosion and insufficient load-bearing capacity, thereby significantly improving the service performance and service life of dilapidated bridges.

[0185] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations made to these embodiments without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A prestressed UHPC flexural reinforcement structure for the negative bending moment zone of a concrete bridge deck, characterized in that, The bridge deck includes prestressed steel strands laid on the concrete bridge deck, a UHPC reinforcement layer cast on the concrete bridge deck and bonded to the prestressed steel strands to form an integral structure, a precast UHPC anchoring device, and a precast steel-UHPC turning device. The UHPC reinforcement layer is cast in place using fast-setting, shrinkage-reducing UHPC material and is equipped with a toughening steel mesh. The precast steel-UHPC turning device enables the prestressed steel strands to turn from the upper edge of the concrete bridge deck to the lower edge of the concrete bridge deck. The prestressed steel strands are anchored to the lower edge of the concrete bridge deck by the precast UHPC anchoring device. The concrete bridge deck is roughened, and bridge deck reinforcement is inserted into the roughened surface. A prestressed steel strand groove channel for laying prestressed steel strands, a steering device mounting groove for installing precast steel-UHPC steering devices, and a bridge deck prestressed steel strand hole for the prestressed steel strands to pass through the bridge deck are opened at the designed position of the concrete bridge deck. Steering device reinforcement holes are drilled at the steering device mounting groove, and anchor bolt holes are drilled at the corresponding position of the precast UHPC anchor device. The precast steel-UHPC steering device includes a precast UHPC steering block and a steering block stiffening steel plate covering the surface of the precast UHPC steering block; the precast UHPC steering block has pre-embedded steering device extension steel bars and has through holes for steering device prestressed steel strands, and the steering device extension steel bars are matched with the bridge deck steering device rebar anchoring holes; the steering block stiffening steel plate has a pre-reserved bevel. Quick-setting anchoring adhesive is injected into the anchoring holes of the steering device in the concrete bridge deck. The protruding reinforcing bars of the steering device are then inserted into the anchoring holes. Finally, the stiffening steel plate of the steering block is welded to the reinforcing steel of the concrete bridge deck at the reserved bevel position to achieve the installation and fixation of the precast steel-UHPC steering device.

2. The prestressed UHPC flexural strengthening structure for the negative bending moment zone of a concrete bridge deck according to claim 1, characterized in that, The prestressed steel strands are configured according to the design load calculation, and the UHPC reinforcement layer is fixed to the concrete bridge deck through the bonding effect of new and old concrete and the rebar connection of the bridge deck.

3. The prestressed UHPC flexural strengthening structure for the negative bending moment zone of a concrete bridge deck according to claim 1, characterized in that, The precast UHPC anchoring device includes a precast UHPC anchoring block and a single-hole anchor. The precast UHPC anchoring block has pre-drilled bolt holes, prestressed steel strand holes for the anchoring device, and a sealing groove. The single-hole anchor is used to anchor both ends of the prestressed steel strand to the steel pad of the precast UHPC anchoring block. The precast UHPC anchoring device is connected and fixed to the concrete bridge deck by high-strength bolts. The high-strength bolts are inserted into the bolt holes and extend to the anchoring device bolt holes on the bridge deck. The sealing groove is used to inject quick-setting UHPC grout after the precast UHPC anchoring device is installed and fixed.

4. The prestressed UHPC flexural strengthening structure for the negative bending moment zone of a concrete bridge deck according to claim 1, characterized in that, The rapid-setting, shrinkage-reducing UHPC material used in the UHPC reinforcement layer must have a compressive strength of at least 80% of the 28-day compressive strength at 3 days, and its self-shrinkage must be controlled within 300με; the toughening steel mesh uses HRB400 grade steel bars with a diameter range of Φ8~Φ12.

5. A design method for a prestressed UHPC flexural strengthening structure for the negative bending moment zone of a concrete bridge deck as described in any one of claims 1-4, characterized in that, Includes the following steps: Step S1: Based on the original bridge structural design drawings and inspection reports, determine the cross-sectional dimensions, concrete strength, and reinforcement of the main beam support; calculate the design value of the bending moment at the main beam support section according to the specifications based on the proposed design load. Step S2: Based on the original concrete bridge main beam support section dimensions, top slab thickness, and steel reinforcement protective layer thickness, preliminarily determine the thickness of the UHPC reinforcement layer and the quantity and area of ​​prestressed steel strands. Step S3, internal force verification of the negative bending moment zone of prestressed UHPC flexural strengthening concrete bridge deck: internal force verification is performed according to the positive section bearing capacity of the flexural member to determine the cross-sectional area of ​​the prestressed steel strand; Step S4: Based on the calculated area of ​​the prestressed steel strands, determine the size and quantity of the prestressed steel strands, and formulate a specific reinforcement scheme for the prestressed UHPC bending reinforcement structure in the negative bending moment zone of the concrete bridge deck.

6. The design method for the prestressed UHPC flexural strengthening structure in the negative bending moment zone of a concrete bridge deck according to claim 5, characterized in that, In step S3, the flexural capacity of the prestressed UHPC flexural-strengthened concrete bridge deck flexural member is verified using the following formula: Condition ①: ； If condition ① is met, the bearing capacity of the normal section shall be checked according to the following formula: ； Calculation of the height of the concrete compression zone: ； If condition ① is not met, the bearing capacity of the normal section shall be checked according to the following formula: ； Calculation of the height of the concrete compression zone: ； The height of the compression zone of concrete should meet the following conditions: ； In the formula: —The importance factor of the bridge structure shall be adopted in accordance with the specifications; —Design value of bending moment after component reinforcement; —The strength utilization coefficient of the newly added prestressed steel strand is set at 0.9; —Added design value for tensile strength of prestressed steel strand; —Design value of axial tensile strength of UHPC; —Design value of axial compressive strength of ordinary concrete in the original component; —These are the design values ​​of the tensile strength of ordinary steel bars and prestressed steel bars in the tension zone of the original component, respectively; —These are the design values ​​of the compressive strength of ordinary steel bars and prestressed steel bars in the compression zone of the original component, respectively; —The stress of the prestressed steel bars when the normal stress of the concrete at the resultant point of the prestressed steel bars in the compression zone of the original component is equal to zero; —Increased cross-sectional area of ​​prestressed steel strands; —These represent the cross-sectional areas of the ordinary steel bars and prestressed steel bars in the tension zone of the original component, respectively; —These represent the cross-sectional areas of the ordinary reinforcing bars and prestressed reinforcing bars in the compression zone of the original component, respectively; —Height of the concrete compression zone; —The relative height of the compression zone of the original component section; —This refers to the width of a rectangular section or the thickness of the web in a T-shaped or I-shaped section; —These represent the effective width and thickness of the compression flange for T-type or I-type cross-sections, respectively; —These represent the width and thickness of the UHPC reinforcement layer section, respectively; —These represent the total height of the reinforced section, the effective height of the reinforced section, and the effective height of the section before reinforcement, respectively. —These are the distances from the resultant force points of ordinary steel bars and prestressed steel bars in the compression zone of the original member to the edge of the compression zone, respectively. — The distance from the point of combined force of ordinary steel bars and prestressed steel bars in the compression zone of the original component to the edge of the compression zone.

7. A construction method for a prestressed UHPC flexural strengthening structure for the negative bending moment zone of a concrete bridge deck as described in any one of claims 1-4, characterized in that, Includes the following steps: Step S1, concrete bridge deck interface treatment, is as follows: The concrete bridge deck was roughened and reinforced with steel bars. Grooves for prestressed steel strands and grooves for steering devices were opened, and prestressed steel strand ducts for the bridge deck were drilled at the ends. The grooves for steering devices were roughened to expose the reinforcing steel bars in the concrete bridge deck, and holes for reinforcing steel bars for steering devices were drilled. The contact surfaces for the anchoring devices in the concrete bridge deck were treated, and high-strength bolts were inserted. Step S2, the installation and fixing of the precast steel-UHPC steering device and the precast UHPC anchoring device, are as follows: Quick-setting anchoring adhesive is injected into the anchoring holes of the steering device in the concrete bridge deck, and the protruding reinforcing bars of the steering device are quickly inserted into the anchoring holes of the steering device. Then, the stiffening steel plate of the steering block is welded to the reinforcing steel of the concrete bridge deck at the reserved bevel position to realize the installation and fixation of the precast steel-UHPC steering device. The pre-reserved bolt holes of the prefabricated UHPC anchor block are matched with the high-strength bolts inserted into the concrete bridge deck for positioning, and then the nuts are tightened to realize the installation and fixation of the prefabricated UHPC anchor device. Step S3, tensioning and anchoring of prestressed steel strands, is as follows: Prestressed steel strands are sequentially threaded into the groove channel of the prestressed steel strand, the prestressed steel strand duct of the steering device, the prestressed steel strand duct of the bridge deck, and the prestressed steel strand duct of the anchorage device. Then, a small hydraulic jack is used to tension the prestressed steel strands to the control stress, which is 0.65 times the standard value of its tensile strength. The prestressed steel strands are tensioned symmetrically from the middle to both sides in the transverse direction of the concrete bridge deck. Single-hole anchorages are used to anchor both ends of the prestressed steel strands to the steel pads of the precast UHPC anchor blocks, and the exposed part of the prestressed steel strands is cut off. After the tensioning and anchoring of the prestressed steel strands are completed, quick-setting UHPC grouting material is injected into the sealing groove to protect the anchor and prestressed steel strands from external environmental corrosion. Step S4, UHPC reinforcement layer cast-in-place construction, details are as follows: The contact surface between the concrete bridge deck and the UHPC reinforcement layer is moistened to make the ordinary concrete on the surface wet and saturated. Erect the UHPC reinforcement layer formwork, arrange the toughening steel mesh, and then pour the UHPC reinforcement layer. The pouring sequence is as follows: first, inject UHPC mixture into the prestressed steel strand ducts of the anchoring device, the prestressed steel strand ducts of the steering device, and the prestressed steel strand ducts of the bridge deck, and then pour the UHPC reinforcement layer inside the formwork. Step S5, UHPC reinforcement layer curing.

8. The construction method of the prestressed UHPC flexural strengthening structure for the negative bending moment zone of a concrete bridge deck according to claim 7, characterized in that, In step S5, after the UHPC reinforcement layer is cast and molded, it is then sprayed with water and covered with a membrane for curing under natural curing conditions. During the curing period, the surface of the UHPC reinforcement layer should be kept moist, and the temperature difference between it and the concrete bridge deck and the surrounding atmosphere should be less than or equal to 20℃ to avoid plastic shrinkage cracks in the UHPC reinforcement layer. Once the UHPC reinforcement layer reaches the expected strength, the template is removed, and the UHPC reinforcement layer is bonded to the internal prestressed steel strands and toughened steel mesh to form a whole.

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