Method for reinforcing concrete box girder structure and method for checking reinforced concrete box girder structure

Abstract

A concrete box girder structure reinforcing method and checking method, wherein the concrete box girder structure reinforcing method comprises the following steps: S1, roughening the original web of the original bridge box girder to obtain a roughened web, and entering S2; S2, arranging positioning lines on the roughened web according to intervals, drilling a plurality of anchoring holes according to the positioning lines, implanting a first shear connector into the corresponding anchoring hole through epoxy resin glue, and completing anchoring after the epoxy resin glue is solidified, and entering S3; S3, assembling a gold plate on the roughened side of the roughened web; S4, pouring UHPC in the pouring cavity to form a UHPC filling layer, and obtaining a reinforced concrete box girder structure. The reinforcing method can effectively improve the web bearing capacity and stiffness without increasing the total thickness of the web, and significantly reduce the reinforcement additional dead load. The checking method converts the reinforcement design process from experience judgment to quantitative analysis, solving the problem of relying on experience and repeated trial calculation in traditional reinforcement design.

Description

Technical Field

[0001] This invention relates to the field of bridge technology with spans greater than 100 meters, and particularly to a method for strengthening concrete box girder structures and a calculation method for strengthening concrete box girder structures. Background Technology

[0002] Currently, common reinforcement techniques for web cracking in long-span prestressed concrete box girder bridges mainly include cross-section enlargement, external steel plate reinforcement, and UHPC thin-layer reinforcement. However, these traditional reinforcement methods generally suffer from limitations in applicable span range and significant increases in additional dead load, and they are difficult to meet the performance requirements for crack width control and long-term stiffness maintenance under normal serviceability limits. Particularly for long-span or ultra-long-span concrete box girder bridges with spans exceeding 100m, the high principal tensile stress level in the cracked web and the extreme sensitivity of mid-span deflection to the added self-weight of the reinforcement system mean that existing reinforcement technologies often fall short in addressing these conditions, exhibiting a significant technological gap in balancing load-bearing capacity enhancement and additional dead load control. To overcome this technological bottleneck, effectively improve the structural load-bearing capacity and stiffness of the web of long-span box girder bridges, and ensure the long-term safe operation of bridge structures under complex conditions, it is urgent to develop a new, efficient reinforcement technology system that combines lightweight high strength, convenient construction, and reliable interface-based stress distribution.

[0003] In the prior art, Chinese patent CN104652294A discloses a technology for reinforcing box girders with ultra-high performance concrete bonded steel plates. This technology uses a combination of steel strips and UHPC to reinforce uniform cross-section box girder structures. However, this solution is only suitable for small-to-medium span uniform cross-section box girder bridges and cannot meet the reinforcement requirements of large-span or ultra-large-span bridges. Chinese patent CN114197338A discloses a reinforcement structure for large-span PC box girder bridges, which uses a combination of double-layer steel plates, bolts, and UHPC to reinforce large-span box girders. While this solution features good durability, high strength, and excellent overall stiffness, it suffers from complex procedures, high construction costs, and a significant increase in additional dead load on the structure. Furthermore, when dealing with mid-span deflection conditions in large-span rigid frame bridges, it may exacerbate the risk of exceeding the principal tensile stress limit. Chinese patent CN115434263B discloses a method for reinforcing damaged bridges using a composite application of thin steel plates and UHPC. This method mainly targets the repair of local impact damage to steel beams or composite beams. However, it does not provide an effective stiffness reinforcement method for the problem of excessive overall principal tensile stress and continuous mid-span deflection caused by long-term creep and prestress loss in the web of large-span concrete box girders. Furthermore, it involves a large amount of work and is not conducive to further reducing the thickness of the reinforcement layer.

[0004] Therefore, it is essential to provide a reinforcement method and verification method for concrete box girder structures to address the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for strengthening concrete box girder structures. This method can effectively improve the shear bearing capacity and bending stiffness of the web without increasing the total thickness of the web, and significantly reduce the additional dead load of the reinforcement. It is convenient to construct and suitable for web reinforcement of long-span concrete box girder bridges.

[0006] The above-mentioned objectives of the present invention are achieved through the following technical measures: A method for strengthening a concrete box girder structure is provided, comprising the following steps: S1. Roughen the original web of the original bridge box girder, remove the concrete protective layer on the surface of the original web until the internal inherent steel bars are exposed, and obtain the roughened web, proceed to S2. S2. After the web is roughened, positioning lines are set at intervals. Multiple anchoring holes are drilled according to the positions marked by the positioning lines. The first shear connector is implanted into the corresponding anchoring holes through epoxy resin adhesive. After the epoxy resin adhesive is cured, the anchoring is completed and proceeds to S3. S3. An alloy plate is assembled on the chiseled side of the chiseled web. The gap between the chiseled web and the alloy plate is defined as a casting cavity. Multiple second shear connectors are fixed on one side of the alloy plate. The second shear connectors are arranged in an array in the alloy plate. The ends of the second shear connectors extend toward the chiseled side of the chiseled web, and the second shear connectors and the first shear connectors are staggered. S4. UHPC is poured into the casting cavity to form a UHPC filling layer, resulting in a reinforced concrete box girder structure.

[0007] Preferably, both the first shear connector and the second shear connector are capped weld studs.

[0008] Preferably, the thickness of the UHPC filling layer is equal to the thickness of the original web concrete protective layer.

[0009] In the roughened web, the implantation interval of the first shear connector is 30cm to 45cm, and the exposed length of the first shear connector is less than 80% of the thickness of the UHPC filler layer.

[0010] In the alloy plate, the second shear connectors are spaced 30cm to 45cm apart, and the exposed length of the second shear connectors is less than 80% of the thickness of the UHPC filler layer.

[0011] Preferably, the density of the alloy plate is not greater than 5 g / cm³. 3 The yield strength is not less than 220 MPa and the tensile strength is not less than 250 MPa.

[0012] Preferably, the expansion of the casting mixture of the above-mentioned UHPC filling layer is not less than 700 mm, the compressive strength is not less than 120 MPa, and the casting mixture contains fibers with hooked ends.

[0013] Preferably, S1 specifically involves: roughening the original web of the original bridge box girder, removing the concrete protective layer on the surface of the original web until the inherent steel reinforcement inside is exposed, and obtaining a roughened web. At the same time, a grouting hole is opened at the corresponding position of the top plate of the original bridge box girder, and the casting cavity is connected to the grouting hole to proceed to S2.

[0014] Preferably, S3 is performed by the following steps: S3.1. Insert multiple positioning bolts into the chiseled side of the web after chiseling, and open through holes in the alloy plate corresponding to the positions of the positioning bolts. S3.2. Insert the positioning bolt into the through hole, and then adjust the nut to fix the alloy plate at the preset spacing position.

[0015] Preferably, the alloy plate is provided with multiple sub-plates. After all the sub-plates are fixed to the chiseled side of the chiseled web plate, all the sub-plates are spliced ​​together to form a whole.

[0016] A method for reinforcing a concrete box girder structure according to the present invention includes the following steps: S1, roughening the original web of the original bridge box girder, removing the concrete protective layer on the surface of the original web until the inherent steel reinforcement inside is exposed, obtaining a roughened web, proceeding to S2; S2, setting positioning lines at intervals on the roughened web, drilling multiple anchoring holes at the positions marked by the positioning lines, inserting a first shear connector into the corresponding anchoring holes using epoxy resin adhesive, and completing the anchoring after the epoxy resin adhesive has cured, proceeding to S3; S3, in the roughened... An alloy plate is assembled on the roughened side of the web after roughening. The gap between the roughened web and the alloy plate is defined as a casting cavity. Multiple second shear connectors are fixed on one side of the alloy plate. The second shear connectors are arranged in an array in the alloy plate, and the ends of the second shear connectors extend towards the roughened side of the web after roughening. The second shear connectors and the first shear connectors are staggered. S4. UHPC is poured into the casting cavity to form a UHPC filling layer, thereby obtaining a reinforced concrete box girder structure. The beneficial effects of this concrete box girder structure reinforcement method are as follows: 1. In view of the technical problem that the principal tensile stress of the web of large-span or ultra-large-span box girders exceeds the limit and the continuous mid-span deflection is highly sensitive to the self-weight of the structure, this invention effectively controls the additional dead load applied to the original structure by using ultra-high performance concrete (UHPC) combined with high-strength lightweight alloy plates to form a combined reinforcement layer. 2. Utilizing alloy plates as permanent formwork, along with adjusting bolts for precise positioning, simplifies the construction process to four steps: interface roughening, shear connector insertion, alloy plate positioning, and UHPC pouring. This eliminates the need for on-site rebar tying and the erection of traditional formwork systems, significantly reducing formwork costs and additional construction weight. 3. Reliable synergistic stress distribution between the old and new interfaces: Complete removal of the web concrete cover and insertion of shear connectors create a reliable mechanical interlock, ensuring reliable bonding and synergistic operation between the ultra-high performance concrete reinforcement layer and the existing concrete box girder structure. 4. Lightweight and efficient reinforcement structure: Based on the ultra-high mechanical properties and vibration-free self-compacting characteristics of UHPC, no ordinary steel mesh is required inside the reinforcement layer. While maintaining a relatively small cover thickness, it effectively strengthens the shear capacity and bending stiffness of the web. In summary, this invention has the advantages of lightweight structure, reliable interface bonding, simple construction procedures, short overall construction period, and low project cost. It is particularly suitable for concrete box girder reinforcement projects with limited construction space and spans exceeding 100m.

[0017] Another objective of this invention is to provide a verification method for reinforced concrete box girder structures, overcoming the shortcomings of existing technologies. This verification method transforms the reinforcement design process from experience-based judgment to verifiable quantitative analysis, solving the problems of traditional reinforcement design relying on experience and repeated trial calculations. It improves the scientific rigor and efficiency of reinforcement scheme design and provides a reusable design basis for the reinforcement of the web of box girders with large spans and varying degrees of damage.

[0018] The above-mentioned objectives of the present invention are achieved through the following technical measures: A calculation method for reinforcing concrete box girder structures is provided, including the following steps: A1. Calculate the geometric characteristics of the combined cross section after reinforcement in the reinforced concrete box girder structure. The combined cross section is composed of the cross section of the roughened web, the cross section of the UHPC filling layer, and the cross section of the alloy plate. A2. Verify the ultimate flexural capacity of the combined cross section. M u When the ultimate bending bearing capacity M u If the conditions are not met, increase the thickness of the UHPC filling layer and the thickness of the alloy plate in the above-mentioned concrete box girder structure reinforcement method, and then return to A1; when the ultimate flexural bearing capacity... M u When the conditions are met, proceed to A3; A3. Verify the total shear capacity of the box girder in the reinforced concrete box girder structure. V u and principal tensile stress s tp When the total shear bearing capacity V u and principal tensile stress s tp If the conditions are met, proceed to A4; otherwise, increase the thickness of the UHPC filling layer and the thickness of the alloy plate in the above-mentioned concrete box girder structure reinforcement method, and then return to A1. A4. Verify the interface shear resistance in the reinforced concrete box girder structure. If the interface shear resistance does not meet the requirements, reduce the spacing of the first shear connector in the above-mentioned concrete box girder structure reinforcement method, reduce the spacing of the second shear connector in the above-mentioned concrete box girder structure reinforcement method, increase the diameter of the first shear connector in the above-mentioned concrete box girder structure reinforcement method, or increase the diameter of the second shear connector in the above-mentioned concrete box girder structure reinforcement method by at least one of the following: then recalculate the interface shear resistance. If the interface shear resistance meets the requirements, proceed to A5. A5. Verify the peel stress in the reinforced concrete box girder structure. s When peel stress s If the conditions are not met, reduce the spacing of the first shear connector in the above-mentioned concrete box girder structure reinforcement method, reduce the spacing of the second shear connector in the above-mentioned concrete box girder structure reinforcement method, and increase at least one of the roughness of the roughened side of the web after roughening in the above-mentioned concrete box girder structure reinforcement method, and then return to A1; when the peel stress s If the conditions are met, the calculation is passed, and the original bridge box girder concrete is reinforced.

[0019] Preferably, A1 above is performed by the following steps: A1.1 Calculate the neutral axis position of the combined cross section according to equations (1)-(3). y , ...Equation (1); ...Equation (2); ...Equation (3); in, n u The stiffness ratio of the UHPC filling layer to the concrete stiffness in the original web is given. n l The ratio of the stiffness of the alloy plate to the stiffness of the concrete in the original web is given. E c Let be the elastic modulus of the concrete in the original web. E u The elastic modulus of the UHPC filler layer. E l Let be the elastic modulus of the alloy plate. b w The thickness of the web plate after roughening. h c The length of the web plate in the height direction of the combined cross section after chiseling is given. h u The thickness of the UHPC filler layer, h l The thickness of the alloy plate is given. A The cross-sectional area of ​​the original web. A c The cross-sectional area of ​​the UHPC filling layer A u and the cross-sectional area of ​​the alloy plate A l The sum of the cross-sectional areas of the original web. A c for b w h c Item, the cross-sectional area of ​​the UHPC filling layer A u for h u h c Item, the cross-sectional area of ​​the alloy plate A l for h l h citem; A1.2 Calculate the moment of inertia of the combined cross section according to equation (4). I , ...Equation (4); in, I c The moment of inertia after the web is roughened and moved parallel to the axis is considered. I u The moment of inertia of the UHPC filling layer after parallel axis shift. I l The moment of inertia of the alloy plate after it has been paralleled by the axis of displacement is given.

[0020] Preferably, A2 above is performed by the following steps: A2.1 Calculate the resultant force of the concrete compression zone in the original web using equation (5). C c , ...Equation (5); in, f c，c This represents the compressive strength of the concrete in the original web. x The height of the pressure zone; The resultant force of the compression zone of the UHPC filling layer is calculated using equation (6). C u , ...Equation (6); in, f c，u The compressive strength of the UHPC filler layer; A2.2 Calculate the total compressive strength using formula (7) C The specific expression is as follows: ...Equation (7); The inherent steel reinforcement in the reinforced concrete box girder structure is calculated using equation (8). T s The resultant force in the tensile zone of the alloy plate T l The resultant force of the tension zone of the prestressed tendons in the reinforced concrete box girder structure T p , ...Equation (8); in, f y，s The yield strength of the inherent reinforcing steel is given by [the specific value]. A s The cross-sectional area of ​​the inherent reinforcing steel is given. f y，lThe yield strength of the alloy plate is given by [the value of the alloy plate]. f py The yield strength of the prestressed tendon is... A p The cross-sectional area of ​​the prestressing tendon; The resultant force in the tensile zone of the UHPC filler layer is calculated using equation (9). T u , ...Equation (9); in, k The tensile flexural reduction factor of the UHPC filler layer is... k It is 0.6-0.8. f t，u The tensile strength of the UHPC filler layer; A2.3 Calculate the total tensile force of the reinforced concrete box girder structure using equation (10). T , ...Equation (10); A2.4 Calculate the height of the compression zone of the combined cross section using equation (11). x , ...Equation (11); A2.5 Calculate the ultimate flexural capacity using equation (12). M u When the ultimate bending bearing capacity M u Less than r 0 M 0 If the condition is not met, then it is considered that the condition is not satisfied. r 0 The structural importance coefficient and r 0 It is 1.1. M 0 Design the bending moment for the actual load, then increase the thickness of the UHPC filler layer and the alloy plate, then return to A1; when the ultimate bending bearing capacity... M u Greater than or equal to r 0 M 0 If the condition is met, proceed to A3; ...Equation (12); in, M u0 This refers to the ultimate flexural bearing capacity of the original bridge box girder. h 0Δ is the effective thickness of the cross-section of the original web. M The additional bending moment introduced by the reinforcement layer, which is composed of the UHPC filler layer and the alloy plate. H The height of the original box girder is given.

[0021] Preferably, A3 above is performed by the following steps: A3.1 Calculate the shear contribution of the concrete in the original web according to formula (13). V c,c , ...Equation (13); in, f t，c The tensile strength of the concrete in the original web is given. f yv The yield strength of the inherent stirrups in the reinforced concrete box girder structure is given by [reference to a specific value]. A sv Let be the area of ​​the inherent stirrups. S v The spacing of the inherent stirrups; The shear contribution of the UHPC filling layer is calculated according to equation (14). V U , ...Equation (14); in, i The angle of the diagonal crack; The shear contribution of the alloy plate is calculated according to equation (15). V l , ...Equation (15); in, For the buckling reduction coefficient and It is 0.6-0.8; The shear contribution of the prestressing tendon is calculated according to equation (16). V p , ...Equation (16); Where, σ pe The effective prestress of the prestressing tendon; A3.2 Calculate the total shear capacity according to formula (17). V u Calculate the principal tensile stress according to equation (18) s tp ,when V u Greater than or equal to r 0V 0 ,and s tp Less than or equal to 0.4 f t，k Then the condition is met, where f t，k This refers to the limit value of the principal tensile stress in concrete. V 0 To design shear force, proceed to A4; otherwise, if the condition is not met, increase the thickness of the UHPC filler layer and the thickness of the alloy plate, then return to A1. ...Equation (17); ...Equation (18); in, s cx It is longitudinal normal stress. s cy τ is the vertical normal stress, and τ is the average shear stress at the interface.

[0022] Preferably, the above A4 is performed by the following steps: A4.1 Calculate the shear flow per unit length of the reinforced concrete box girder structure using equation (19). v , ...Equation (19); in, V max The maximum shear force design value of the cross section of the original web and V max = V 0 , S l The area moment of the alloy plate about the neutral axis of the combined cross section; A4.2 Calculate the shear bearing capacity of a single shear connector using equation (20). v sd Furthermore, the first shear connector and the second shear connector have the same dimensions, the same material, and the same shear bearing capacity; when the shear bearing capacity v sd Less than or equal to 0.7 A sd f u，sd If the condition is met, proceed to A4.3, where... A sd Let be the cross-sectional area of ​​the shear connector. f u，sdThe tensile strength of the first shear connector and the second shear connector is used; otherwise, the condition is not met. Then, the spacing between the first shear connector and the second shear connector is reduced, or the diameter of the first shear connector or the diameter of the second shear connector is increased, or at least one of these is increased, and then the process returns to A4.1. ...Equation (20); A4.3 Calculate the shear flow per unit length of the reinforced concrete box girder structure using equation (21). v rd When shear flow v rd Shear flow greater than or equal to v If the first shear connector is not in use, proceed to A5; otherwise, reduce the spacing of the first shear connector, reduce the spacing of the second shear connector, increase the diameter of the first shear connector, or increase the diameter of the second shear connector, and then return to A4.1. ...Equation (21); in, S 1 The spacing of the first shear connector is [specified]. S 2 The spacing of the second shear connector. v sd1 This represents the shear bearing capacity of the first shear connector. v sd2 This represents the shear bearing capacity of the second shear connector.

[0023] Preferably, the above A5 is performed by the following steps: A5.1 Calculate the peel stress in the reinforced concrete box girder structure according to formula (22). s , ...Equation (22); in, L t For stress transmission length, l For interfacial bonding stiffness; A5.2 Calculate the design value of the interfacial peel resistance bearing capacity according to formula (23). s 0 When peel stress s Less than or equal to s 0 If the conditions are met and the calculation is passed, the original bridge box girder concrete is reinforced; otherwise, the conditions are not met. Then, reduce the spacing of the first shear connector, reduce the spacing of the second shear connector, and increase the roughness of the roughened side of the roughened web plate by at least one of the following: then return to A1. ...Equation (23); in, c This is the interface roughness coefficient, when the roughening is done mechanically. c The value is 0.6-0.8, when the roughening is simple roughening. c It is 0.4-0.5. r s1 The reinforcement ratio of the first shear connector is given. or 1 The anchorage reduction factor for the first shear connector is... r s2 This refers to the reinforcement ratio of the second shear connector. or 2 This is the anchorage reduction factor for the second shear connector. m The coefficient of interfacial friction, N p This refers to the effective axial pressure generated by the prestressed tendons.

[0024] This invention discloses a verification method for a reinforced concrete box girder structure, wherein the reinforced concrete box girder structure is obtained by the aforementioned method for reinforcing concrete box girder structures. The verification method includes the following steps: A1, calculating the geometric properties of the composite cross-section in the reinforced concrete box girder structure; A2, verifying the ultimate flexural bearing capacity of the normal cross-section of the box girder in the reinforced concrete box girder structure. M u When the ultimate bending bearing capacity M u If the conditions are not met, increase the thickness of the UHPC filling layer and the thickness of the alloy plate in the concrete box girder structure reinforcement method, and then return to A1; when the ultimate flexural bearing capacity... M u If the conditions are met, proceed to A3; A3, verify the total shear capacity of the box girder in the reinforced concrete box girder structure. V u and principal tensile stress s tp When the total shear bearing capacity V u and principal tensile stress s tpIf the conditions are met, proceed to A4; otherwise, increase the thickness of the UHPC filling layer and the alloy plate in the concrete box girder structure reinforcement method, and then return to A1; A4, verify the interface shear resistance in the reinforced concrete box girder structure. If the interface shear resistance does not meet the conditions, reduce the spacing of the first shear connector, reduce the spacing of the second shear connector, increase the diameter of the first shear connector, or increase the diameter of the second shear connector, and then recalculate the interface shear resistance; if the interface shear resistance meets the conditions, proceed to A5; A5, verify the peel stress in the reinforced concrete box girder structure. s When peel stress s If the conditions are not met, reduce the spacing of the first shear connector in the reinforced concrete box girder structure, reduce the spacing of the second shear connector, and increase the roughness of the roughened side of the roughened web, then return to A1; when the peel stress s When the conditions are met, the calculation passes, and the original bridge box girder concrete is reinforced. This calculation method is a complementary method to the aforementioned concrete box girder structure reinforcement method. It obtains the existing bridge structural parameters and preset reinforcement targets, initially selects the UHPC reinforcement layer thickness and alloy plate specifications, and performs verification based on the plane section assumption and section deformation compatibility conditions. This calculation method transforms the reinforcement design process from experience-based judgment to verifiable quantitative analysis, solving the problems of traditional reinforcement design relying on experience and repeated trial calculations. It improves the scientific rigor and efficiency of reinforcement scheme design and provides a reusable design basis for the reinforcement of the web of box girders with large spans and varying degrees of damage. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the original bridge box girder.

[0026] Figure 2 This is a schematic diagram of the axle box girder after roughening and implantation of the first shear connector.

[0027] Figure 3 This is a structural schematic diagram of the alloy plate and the second shear connection.

[0028] Figure 4 A partial cross-sectional structural diagram for reinforcing a concrete box girder structure.

[0029] Figure 5 This is a schematic diagram of the cross-section of the original web.

[0030] Figure 6 This is a schematic diagram of the combined cross-section.

[0031] Figure 7 This is a flowchart of the verification method of the present invention.

[0032] Figure 8 This is a schematic diagram showing the position of the neutral axis and the height of the compression zone in the combined cross-section.

[0033] exist Figure 1 to Figure 8 This includes: Box girder 1 Web 11, Concrete cover 111, Inherent reinforcement 112, Inherent stirrups 113 Top plate 12, bottom plate 13 Alloy plate 14 UHPC filler layer 15 First shear connector 16, second shear connector 17, positioning bolt 18. Detailed Implementation

[0034] The technical solution of the present invention will be further described in conjunction with the following embodiments.

[0035] Example 1

[0036] A method for strengthening a concrete box girder structure includes the following steps: S1, for the original bridge box girder 1 (such as...) Figure 1 The original web 11 is roughened by chiseling away the concrete protective layer 111 on the surface of the original web 11 until the internal inherent steel reinforcement 112 is exposed, resulting in a roughened web 11. Figure 5 Enter S2; S2. After chiseling, set positioning lines on the web 11 at intervals, drill holes at the positions marked by the positioning lines, and insert the first shear connector 16 into the holes using epoxy resin adhesive. After the epoxy resin adhesive cures, the anchoring is completed, and proceed to S3. Figure 2 ; S3. After chiseling, an alloy plate 14 is assembled on the chiseled side of the web 11. The gap between the chiseled web 11 and the alloy plate 14 is defined as the casting cavity. Multiple second shear connectors 17 are fixed to one side of the alloy plate 14. The second shear connectors 17 are distributed in an array within the alloy plate 14, such as... Figure 3 The second shear connector 17 extends toward the chiseled side of the web 11 after chiseling, and the second shear connector 17 and the first shear connector 16 are staggered. Figure 6 As shown; S4. UHPC is poured into the cavity to form a UHPC filling layer 15, resulting in the reinforced concrete box girder 1 structure, as shown below. Figure 4 .

[0037] It should be noted that during the UHPC casting process, the alloy plate 14 also serves as the outer formwork. The casting of the UHPC continues until the casting cavity is completely filled. In addition to the web plate 11, the original bridge box girder 1 in this invention also includes a top plate 12 and a bottom plate 13.

[0038] Both the first shear connector 16 and the second shear connector 17 are capped weld studs. These capped studs improve shear resistance.

[0039] The thickness of the UHPC infill layer 15 is equal to the thickness of the original web concrete protective layer 111.

[0040] In the roughened web 11, the implantation interval of the first shear connector 16 is 30cm to 45cm, and the exposed length of the first shear connector 16 is less than 80% of the thickness of the UHPC filling layer 15.

[0041] In the alloy plate 14, the second shear connectors 17 are spaced 30cm to 45cm apart, and the exposed length of the second shear connectors 17 is less than 80% of the thickness of the UHPC filler layer 15.

[0042] The density of alloy plate 14 is not greater than 5 g / cm³. 3 The yield strength is not less than 220 MPa, and the tensile strength is not less than 250 MPa. It should be noted that the aforementioned alloy plate 14 is characterized by high strength and lightweight.

[0043] The UHPC filler layer 15 has a casting spread of not less than 700 mm, a compressive strength of not less than 120 MPa, and contains fibers with hooked ends.

[0044] S1 specifically involves: roughening the original web 11 of the original bridge box girder 1, removing the concrete protective layer 111 on the surface of the original web 11 until the inherent steel reinforcement 112 inside is exposed, and obtaining the roughened web 11. At the same time, a grouting hole is opened at the corresponding position of the top plate 12 of the original bridge box girder 1, and the pouring cavity is connected to the grouting hole to enter S2.

[0045] S3 is performed by the following steps: S3.1. After chiseling, multiple positioning bolts 18 are inserted into the chiseled side of the web plate 11, and through holes corresponding to the positions of the positioning bolts 18 are opened in the alloy plate 14. S3.2 Insert the positioning bolt 18 into the through hole, and then adjust the nut to fix the alloy plate 14 at the preset spacing position.

[0046] The alloy plate 14 is provided with multiple sub-plates. After all the sub-plates are fixed to the chiseled side of the web plate 11, all the sub-plates are spliced ​​together to form a whole.

[0047] It should be noted that multiple sub-panels can be connected by installing connecting plates of the same material at the joints between adjacent sub-panels. These connecting plates span the joint and are fitted to the outer surfaces of the adjacent sub-panels, avoiding the opening at the location of the second shear connector 17. The connecting plates are then fixed to the adjacent sub-panels using fastening bolts. Alternatively, multiple sub-panels can be joined together to form a single unit through welding.

[0048] The beneficial effects of this concrete box girder structure reinforcement method are as follows: 1. Addressing the technical problems of excessive principal tensile stress in the web 11 of large-span or ultra-large-span box girders and the high sensitivity of the structure's self-weight to continuous mid-span deflection, this invention effectively controls the additional dead load applied to the original structure during reinforcement construction by using ultra-high performance concrete (UHPC) combined with high-strength lightweight alloy plates 14 to form a composite reinforcement layer. 2. Utilizing the alloy plate 14 as a permanent formwork, and using adjusting bolts for precise positioning, the construction process is simplified to four main steps: roughening treatment, insertion of shear-resistant short weld studs, installation of alloy plate 14, and UHPC pouring. This eliminates the need for on-site rebar tying and the erection of traditional formwork systems, significantly reducing formwork costs and additional self-weight during construction. 3. Reliable co-force distribution between the old and new interfaces. By completely removing the existing concrete protective layer 111 of the web 11 and combining it with the implanted shear-resistant shear connectors to form a mechanical interlock, reliable bonding and co-working between the ultra-high performance concrete reinforcement layer and the existing concrete box girder structure are ensured. 4. The reinforced structure is lightweight and efficient. Based on the ultra-high mechanical properties and vibration-free self-compacting characteristics of UHPC, no ordinary steel mesh is required inside the reinforced layer. While maintaining a relatively small protective layer thickness, it effectively strengthens the shear bearing capacity and flexural stiffness of the web 11. In summary, this invention has the advantages of light added structural weight, reliable interface bonding, simple construction procedures, short overall construction period, and low project cost. It is particularly suitable for the reinforcement of concrete box girders 1 with limited construction space and spans exceeding 100m.

[0049] Example 2

[0050] A calculation method for reinforcing concrete box girder structures, such as Figure 7 As shown, it includes the following steps: A1. Calculate the geometric characteristics of the composite cross section after reinforcement in the reinforced concrete box girder 1 structure. The composite cross section consists of the cross section of the roughened web 11, the cross section of the UHPC filling layer 15, and the cross section of the alloy plate 14. A2. Verify the ultimate flexural capacity of the combined cross-section. M u When the ultimate bending bearing capacity M u If the conditions are not met, increase the thickness of the UHPC filling layer 15 and the alloy plate 14 in the concrete box girder structure reinforcement method of Example 2, and then return to A1; when the ultimate flexural bearing capacity M u When the conditions are met, proceed to A3; A3. Verify the total shear capacity of box girder 1 in the reinforced concrete box girder 1 structure. V u and principal tensile stress s tp When the total shear bearing capacityV u and principal tensile stress s tp If the conditions are met, proceed to A4; otherwise, increase the thickness of the UHPC filling layer 15 and the alloy plate 14 in the concrete box girder structure reinforcement method of Example 2, and then return to A1. A4. Verify the interface shear resistance in the reinforced concrete box girder 1 structure. If the interface shear resistance does not meet the requirements, reduce the spacing of the first shear connector 16 in the reinforcement method of the concrete box girder structure in Example 2, reduce the spacing of the second shear connector 17 in the reinforcement method of the concrete box girder structure in Example 2, and increase at least one of the following: the diameter of the first shear connector 16 or the diameter of the second shear connector 17 in the reinforcement method of the concrete box girder structure in Example 2. Then recalculate the interface shear resistance. If the interface shear resistance meets the requirements, proceed to A5. A5. Verify the peel stress in the reinforced concrete box girder 1 structure. s When peel stress s If the conditions are not met, reduce the spacing of the first shear connector 16, reduce the spacing of the second shear connector 17, and increase the roughness of the roughened side of the web 11 after chiseling in the concrete box girder structure reinforcement method of Example 2, then return to A1; when the peel stress s If the conditions are met, the calculation is passed, and the concrete of the original bridge box girder 1 is reinforced.

[0051] A1 is performed through the following steps: A1.1 Calculate the neutral axis position of the combined cross section according to equations (1)-(3). y ,like Figure 8 As shown, ...Equation (1); ...Equation (2); ...Equation (3); in, n u The ratio of the stiffness of the UHPC infill layer 15 to the stiffness of the concrete in the original web 11. n l The ratio of the stiffness of the alloy plate 14 to the stiffness of the concrete in the original web plate 11. E c This represents the elastic modulus of the concrete in the original web 11. E u The elastic modulus of the UHPC filler layer 15 is given. E l The elastic modulus of alloy plate 14. b w To roughen the thickness of the web 11,h c The length of the web 11 in the height direction of the combined cross section after chiseling is given. h u The thickness of the UHPC filler layer 15 is... h l The thickness of alloy plate 14, A The cross-sectional area of ​​the original web 11 A c Cross-sectional area of ​​UHPC filler layer 15 A u The cross-sectional area of ​​alloy plate 14 A l The sum of the cross-sectional areas of the original web 11. A c for b w h c Item, cross-sectional area of ​​UHPC filler layer 15 A u for h u h c Item, cross-sectional area of ​​alloy plate 14 A l for h l h c item; A1.2 Calculate the moment of inertia of the combined cross section according to equation (4). I , ...Equation (4); in, I c The moment of inertia of the web 11 after it has been roughened and parallel to the axis of displacement. I u The moment of inertia of the UHPC fill layer 15 after parallel axis shift. I l The moment of inertia of alloy plate 14 after parallel axis shift is denoted as .

[0052] It should be noted that the neutral axis position y When a composite cross-section is subjected to bending, the boundary between the tension and compression zones is defined, and the normal stress is zero on this line. Figure 8 As shown.

[0053] A2 is performed through the following steps: A2.1 Calculate the resultant force of the concrete compression zone in the original web 11 using equation (5). C c , ...Equation (5); in, f c，c This represents the compressive strength of the concrete in the original web 11. x The height of the compression zone of the composite cross section, such as Figure 8 As shown; The resultant force of the compression zone of the UHPC filler layer 15 is calculated using equation (6). C u , ...Equation (6); in, f c，u The compressive strength of the UHPC filler layer 15; A2.2 Calculate the total compressive strength using formula (7) C The specific expression is as follows: ...Equation (7); The inherent steel reinforcement 112 in the reinforced concrete box girder 1 structure is calculated using equation (8). T s The resultant force in the tensile zone of alloy plate 14 T l The resultant force of the tension zone of the prestressed tendons in the reinforced concrete box girder 1 structure T p , ...Equation (8); in, f y，s The yield strength of the inherent steel reinforcement 112, A s The cross-sectional area of ​​the inherent reinforcing bar 112 is... f y，l The yield strength of alloy plate 14 f py The yield strength of the prestressing tendon. A p This represents the cross-sectional area of ​​the prestressing tendon; The resultant force in the tensile zone of the UHPC filler layer 15 is calculated using equation (9). T u , ...Equation (9); in, k The tensile flexural reduction factor of UHPC filler layer 15 is given. k It is 0.6-0.8. f t，u The tensile strength of the UHPC filler layer 15; A2.3 Calculate the total tensile force of the reinforced concrete box girder 1 structure using formula (10). T , ...Equation (10); A2.4 Calculate the height of the compression zone of the combined cross section using equation (11). x , ...Equation (11); A2.5 Calculate the ultimate flexural capacity using equation (12). M u When the ultimate bending bearing capacity M u Less than r 0 M 0 If the condition is not met, then it is considered that the condition is not satisfied. r 0 The structural importance coefficient and r 0 It is 1.1. M 0 Design the bending moment for the actual load, then increase the thickness of the UHPC infill layer 15 and the alloy plate 14, then return to A1; when the ultimate bending bearing capacity... M u Greater than or equal to r 0 M 0 If the condition is met, proceed to A3; ...Equation (12); in, M u0 This represents the ultimate bending capacity of the original bridge box girder 1. h 0 Δ is the effective thickness of the cross-section of the original web 11. M The additional bending moment introduced by the reinforcement layer, which consists of a UHPC filler layer 15 and an alloy plate 14, is due to the reinforcement layer. H This is the beam height of the original box girder 1.

[0054] It should be noted that in A2.4, the total compressive strength is used... C With total tensile force T The height of the compression zone in the cross section can be solved immediately. x And when the ultimate bending bearing capacity M u Greater than or equal to r 0 M 0 This indicates that the bending strength is sufficient. The prestressed tendons of this invention are the prestressed steel strands inside the original bridge box girder 1.

[0055] A3 is performed using the following steps: A3.1 Calculate the shear contribution of the concrete in the original web 11 according to formula (13). V c,c , ...Equation (13); in, f t，c This represents the tensile strength of the concrete in the original web 11. f yv To strengthen the yield strength of the inherent stirrups 113 in the concrete box girder 1 structure, A sv The area of ​​the inherent stirrup 113, S v The spacing of the inherent stirrups 113; The shear contribution of the UHPC filler layer 15 is calculated according to equation (14). V U , ...Equation (14); in, i The angle of the diagonal crack; The shear contribution of alloy plate 14 is calculated according to equation (15). V l , ...Equation (15); in, For the buckling reduction coefficient and It is 0.6-0.8; The shear contribution of the prestressing tendon is calculated according to equation (16). V p , ...Equation (16); Where, σ pe This refers to the effective prestress of the prestressing tendon; A3.2 Calculate the total shear capacity according to formula (17). V u Calculate the principal tensile stress according to equation (18) s tp ,when V u Greater than or equal to r 0 V 0 ,and s tp Less than or equal to 0.4 f t，k Then the condition is met, where f t，k This refers to the limit value of the principal tensile stress in concrete. V0 To design the shear force, proceed to A4; otherwise, if the condition is not met, increase the thickness of the UHPC filler layer 15 and the alloy plate 14, and then return to A1. ...Equation (17); ...Equation (18); in, s cx It is longitudinal normal stress. s cy τ is the vertical normal stress, and τ is the average shear stress at the interface.

[0056] It should be noted that when V u Greater than or equal to r 0 V 0 ,and s tp Less than or equal to 0.4 f t，k If the bending strength is sufficient, it indicates that the thickness of the UHPC filler layer 15 and the alloy plate 14 needs to be increased if either of them is not met.

[0057] A4 is produced by the following steps: A4.1 Calculate the shear flow per unit length of the reinforced concrete box girder 1 using equation (19). v , ...Equation (19); in, V max The maximum shear force design value of the original web 11 cross section and V max = V 0 , S l The area moment of alloy plate 14 relative to the neutral axis of the combined cross section; A4.2 Calculate the shear bearing capacity of a single shear connector using equation (20). v sd Furthermore, the first shear connector 16 and the second shear connector 17 have the same dimensions, the same material, and the same shear bearing capacity; when the shear bearing capacity v sd Less than or equal to 0.7 A sd f u，sd If the condition is met, proceed to A4.3, where... A sd Let be the cross-sectional area of ​​the shear connector. fu，sd The tensile strength of the first shear connector 16 and the second shear connector 17 is required; otherwise, the condition is not met. Then, the spacing of the first shear connector 16 is reduced, the spacing of the second shear connector 17 is reduced, the diameter of the first shear connector 16 is increased, or the diameter of the second shear connector 17 is increased, or at least one of these is increased, and then return to A4.1. ...Equation (20); A4.3 Calculate the shear flow per unit length of the reinforced concrete box girder 1 using equation (21). v rd When shear flow v rd Shear flow greater than or equal to v If the first shear connector 16 is not in use, proceed to A5; otherwise, reduce the spacing of the first shear connector 16, reduce the spacing of the second shear connector 17, increase the diameter of the first shear connector 16, or increase the diameter of the second shear connector 17, and then return to A4.1. ...Equation (21); in, S 1 The spacing of the first shear connector 16 S 2 The spacing of the second shear connector 17 v sd1 The shear bearing capacity of the first shear connector 16 v sd2 This refers to the shear bearing capacity of the second shear connector 17.

[0058] A5 is performed using the following steps: A5.1 Calculate the peel stress in the reinforced concrete box girder 1 structure according to formula (22). s , ...Equation (22); in, L t For stress transmission length, l For interfacial bonding stiffness; A5.2 Calculate the design value of the interfacial peel resistance bearing capacity according to formula (23). s 0 When peel stress s Less than or equal to s 0 If the conditions are met and the calculation is passed, the original bridge box girder concrete is reinforced; otherwise, the conditions are not met. Then, reduce the spacing of the first shear connector 16, reduce the spacing of the second shear connector 17, and increase the roughness of the roughened side of the web after chiseling at least one of the following: then return to A1. ...Equation (23); in, c This is the interface roughness coefficient, when the roughening is done mechanically. c The value is 0.6-0.8, when the roughening is simple roughening. c It is 0.4-0.5. r s1 The reinforcement ratio of the first shear connector 16 is... or 1 This is the anchorage reduction factor for the first shear connector 16. r s2 The reinforcement ratio of the second shear connector 17 is... or 2 This is the anchorage reduction factor for the second shear connector 17. m The coefficient of interfacial friction, N p This refers to the effective axial pressure generated by the prestressing tendons.

[0059] It should be noted that in A5.2, this is only beneficial when the prestress compresses the interface. If the prestress puts the interface in tension, this term should be negative. However, prestress usually puts the beam end in compression, so it is positive.

[0060] It should also be noted that some load parameters in the verification method of this invention are known. Based on these known load parameters, it can be determined whether the corresponding verification parameters meet the conditions. The known load parameters are as follows: Original bridge box girder section 1: Length of web 11 in the cross-sectional height direction after roughening h c Thickness of web 11 after chiseling b w The area of ​​the inherent stirrup 113 A sv Spacing of inherent stirrups 113 S v Angle of diagonal crack i The beam height of the original box girder 1 H Effective axial pressure generated by prestressed tendons N p Cross-sectional area of ​​the inherent reinforcing steel bar 112 A s Cross-sectional area of ​​prestressing tendons A p .

[0061] UHPC reinforcement layer: UHPC filler layer thickness 15 h u .

[0062] Alloy plate 14: Thickness of alloy plate 14 hl .

[0063] Shear parameters: Design shear force V 0 .

[0064] Bending parameters: Design bending moment under actual load M 0 Ultimate flexural bearing capacity of the original bridge box girder 1 M u0 .

[0065] Welding stud parameters: = The spacing of the first shear connector 16 S 1 The spacing of the second shear connector 17 S 2 The cross-sectional area of ​​the first shear connector 16 and the second shear connector 17 A sd .

[0066] Material strength parameters: compressive strength of concrete in the original web 11 f c，c The tensile strength of the concrete in the original web 11 f t，c Yield strength of inherent stirrups 113 in reinforced concrete box girder 1 structure f yv The tensile strength of the first shear connector 16 and the second shear connector 17 f u，sd Tensile strength of UHPC filler layer 15 f t，u Yield strength of prestressed tendons f py Yield strength of alloy plate 14 f y，l Yield strength of inherent steel reinforcement 112 f y，s The compressive strength of UHPC filler layer 15 f c，u The tensile flexural reduction factor of UHPC filler layer 15 k Structural importance coefficient r 0 .

[0067] Other parameters: Elastic modulus of concrete in the original web 11 E c Elastic modulus of UHPC filler layer 15 E u Elastic modulus of alloy plate 14 E l Buckling reduction coefficient Effective prestress σ of prestressing tendons pe Longitudinal normal stress s cx Vertical normal stress s cy Interfacial average shear stress τ, interfacial bond stiffness l Interface roughness coefficient c interfacial friction coefficient m The reinforcement ratio of the first shear connector 16 r s1 Anchorage reduction factor of the first shear connector 16 or 1 The reinforcement ratio of the second shear connector 17 r s2 Anchorage reduction factor of the second shear connector 17 or .

[0068] This verification method is a supporting verification method for the aforementioned reinforcement method of concrete box girder structures based on UHPC-high-strength lightweight alloy plate 14. By obtaining the existing bridge structure parameters and preset reinforcement targets, the thickness of the UHPC reinforcement layer and the specifications of the alloy plate 14 can be initially selected, and verification is performed based on the plane section assumption and the section deformation compatibility conditions. This verification method transforms the reinforcement design process from experience-based judgment to verifiable quantitative analysis, solving the problem of traditional reinforcement design relying on experience and repeated trial calculations, improving the scientific nature and efficiency of reinforcement scheme design, and providing a reusable design basis for the reinforcement of the web 11 of box girders with large spans and different degrees of damage.

[0069] Example 3

[0070] Application of the verification method for reinforced concrete box girder structure in Embodiment 2. In this embodiment, aluminum alloy plate 14 is selected as alloy plate 14, with a thickness of 10mm. The alloy plate 14 has a density of 2.7g / cm³, a yield strength of 270MPa, a tensile strength of 300MPa, an elastic modulus of 70GPa, and a thickness of 10mm.

[0071] The thickness of the UHPC filler layer 15 is 25 mm.

[0072] To verify the actual technical effect of the reinforcement structure and method provided in this embodiment, a 120m span PC variable cross-section continuous rigid frame bridge is used as an example for reinforcement calculation. The web 11 in the L / 8 region of the bridge has diagonal cracks, with the principal tensile stress exceeding the limit by approximately 20%, and the mid-span deflection continues to develop. Therefore, a section 8m long from the L / 4 cross-section at the mid-span to the end is selected for reinforcement. The transverse and longitudinal spacing of the weld studs is 400mm. It should be noted that the aforementioned thickness of 10mm is only an exemplary value for this embodiment. In other embodiments of the present invention, the thickness of the aluminum alloy plate 14 can be selected within the range of 8-15mm according to the actual reinforcement requirements, the thickness of the UHPC layer can be selected according to the protective layer thickness of the web 11 of the box girder 1, and the length of the reinforcement section can also be flexibly selected according to the actual extent of the damage, typically within the L / 8-L / 4 section. The transverse and longitudinal spacing between the first shear connector 16 and the second shear connector 17 is 400mm.

[0073] The actual values ​​obtained through A1 are listed in Table 1: Table 1. List of actual values ​​obtained by formulas (1) to (4) in A1

[0074] As shown in the calculation data of A1 in Table 1, the combined reinforcement system of the present invention achieves efficient synergy of the mechanical properties of each material: the original web after roughening provides 5.978 × 10 13 The basic flexural stiffness of the UHPC infill layer is 4.13 × 10⁻⁶. 13 The moment of inertia of the alloy plate becomes the core stiffness reinforcement component, while the alloy plate strengthens the interfacial bonding and structural integrity through rigid constraints; the synergy of these three components results in a total moment of inertia of 6.109 × 10⁻⁶ for the composite section. 13 This significantly improves the bending stiffness and load-bearing capacity of the web.

[0075] The actual values ​​obtained through A2 are listed in Table 2: Table 2. List of actual values ​​and finite element simulation values ​​obtained by formulas (5) to (12) in A2.

[0076] As can be seen from the comparison of the calculated and finite element simulation data in Table 2, the reinforcement effect of this invention is significant and the theoretical calculation method is accurate and reliable: the ultimate bending bearing capacity of the original bridge box girder is 3.73 × 10⁻⁶. 5 After reinforcement, the theoretical ultimate bending capacity increased to 4.6×10⁻⁶. 5 The increase was approximately 23.3%, and significantly greater than 3.5 × 10⁻⁶. 5 The actual load design bending moment has sufficient safety reserve; meanwhile, the theoretically calculated additional bending moment for reinforcement is 8.75 × 10⁻⁶. 4Compared with the finite element simulation value of 8.02×10 4 The relative error is approximately 8.3%, and the theoretical value of the total ultimate flexural bearing capacity differs from the finite element simulation value by 4.53 × 10⁻⁶. 5 The relative error is only about 1.5%, and the two are in good agreement, which verifies the accuracy of the theoretical calculation model of the present invention.

[0077] The actual values ​​obtained through A3 are listed in Tables 3 and 5, while the values ​​obtained through finite element simulation are listed in Tables 4 and 6. Table 3. List of actual values ​​obtained by formulas (13) to (17) in A3

[0078] Table 4. List of numerical values ​​obtained from finite element simulation

[0079] Table 5. List of actual values ​​obtained by formula (18) in A3

[0080] Table 6. List of numerical values ​​obtained from finite element simulation

[0081] As shown in Tables 3 to 6, the comparison between the calculated and finite element simulation data in A3 demonstrates that the reinforcement system of this invention exhibits excellent performance in both shear resistance and stress control. The theoretical total shear capacity of the reinforced composite section reaches 13815.8, which is 1.53 times the design shear force of 9000, providing ample safety reserves. The original web 11 and alloy plate 14 bear approximately 50.4% and 47.4% of the shear force, respectively, indicating that the UHPC filling layer 15 effectively ensures interface force transmission and structural integrity. Simultaneously, the theoretical principal tensile stress of the reinforced web 11 is 0.963 MPa, and the finite element simulation value is 1.043 MPa, both lower than the C50 concrete principal tensile stress limit of 1.06 MPa, effectively avoiding the risk of cracking in the oblique section. The theoretical calculation and finite element simulation results agree well, with a relative error of approximately 8.7% in the total shear capacity and errors in each stress component within 9%, fully verifying the accuracy of the theoretical calculation model and the reliability of the reinforcement effect.

[0082] The actual values ​​obtained through A4 paper are listed in Table 7: Table 7. List of actual values ​​obtained by using equations (19) to (21) in A4

[0083] As shown in the calculation data in A4 of Table 7, the double shear connector structure adopted in this invention can effectively ensure the overall collaborative performance of the composite section: the shear bearing capacity of the first and second shear connectors designed in this invention is 37.156kN and 56.308kN respectively. With a reasonable spacing of 400mm, the shear flow per unit length provided by the reinforced structure connector reaches 233.7kN, which is 8.5 times the shear flow per unit length generated by the external load of 27.3kN, providing a large safety reserve. This proves that the shear connector design of this invention is precise and efficient, which not only makes full use of the mechanical properties of the material, but also fundamentally solves the technical problems of insufficient interface shear force transmission and easy delamination failure in traditional reinforcement methods. It ensures the collaborative stress of the original web plate 11, UHPC filling layer 15 and alloy plate 14 within the full load range, providing a reliable interface force transmission guarantee for the overall mechanical performance of the composite reinforcement system.

[0084] The actual values ​​obtained through A5 are listed in Table 8. Table 8. List of actual values ​​obtained by using equations (22) to (23) in A5

[0085] As shown in the calculation data in A5 of Table 8, the composite reinforcement system of this invention exhibits excellent interfacial bonding performance and outstanding anti-peeling ability: the actual peel stress of the reinforced structure is 0.96 MPa, which is only 45.8% of the design value of 2.095 MPa for interfacial peel bearing capacity, providing ample safety margin. This fully demonstrates that this invention, through the synergistic effect of the roughened web interface, the UHPC high-strength bonding layer, and the double shear connectors, completely solves the problem of easy delamination at the interface in traditional reinforcement methods, ensuring the integrity and long-term service stability of the composite section under load.

[0086] In summary, based on the actual numerical values ​​and finite element simulation data of this embodiment, it can be seen that the verification method of the present invention conforms to objective laws, can perform quantitative analysis and verification, solves the problem of traditional reinforcement design relying on experience and repeated trial calculations, improves the scientificity and efficiency of reinforcement scheme design, and provides a reusable design basis for the reinforcement project of the web 11 of box girder with large span and different degrees of damage.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for strengthening a concrete box girder structure, characterized in that, Includes the following steps: S1. Roughen the original web of the original bridge box girder, remove the concrete protective layer on the surface of the original web until the internal inherent steel bars are exposed, and obtain the roughened web, proceed to S2. S2. After the web is roughened, positioning lines are set at intervals. Multiple anchoring holes are drilled according to the positions marked by the positioning lines. The first shear connector is implanted into the corresponding anchoring holes through epoxy resin adhesive. After the epoxy resin adhesive is cured, the anchoring is completed and proceeds to S3. S3. An alloy plate is assembled on the chiseled side of the chiseled web. The gap between the chiseled web and the alloy plate is defined as a casting cavity. Multiple second shear connectors are fixed on one side of the alloy plate. The second shear connectors are arranged in an array in the alloy plate. The ends of the second shear connectors extend toward the chiseled side of the chiseled web, and the second shear connectors and the first shear connectors are staggered. S4. UHPC is poured into the casting cavity to form a UHPC filling layer, resulting in a reinforced concrete box girder structure.

2. The method for strengthening a concrete box girder structure according to claim 1, characterized in that: Both the first shear connector and the second shear connector are capped weld studs; The thickness of the UHPC filling layer is equal to the thickness of the original web concrete protective layer.

3. The method for strengthening a concrete box girder structure according to claim 2, characterized in that: In the roughened web, the implantation interval of the first shear connector is 30cm to 45cm, and the exposed length of the first shear connector is less than 80% of the thickness of the UHPC filler layer; In the alloy plate, the second shear connectors are spaced 30cm to 45cm apart, and the exposed length of the second shear connectors is less than 80% of the thickness of the UHPC filler layer; The density of the alloy plate is not greater than 5 g / cm³. 3 Yield strength not less than 220 MPa, tensile strength not less than 250 MPa; The expansion of the UHPC filling layer is not less than 700 mm, the compressive strength is not less than 120 MPa, and the casting mixture contains fibers with hooked ends.

4. The method for strengthening a concrete box girder structure according to claim 3, characterized in that, S1 specifically involves: roughening the original web of the original bridge box girder, removing the concrete protective layer on the surface of the original web until the inherent steel reinforcement inside is exposed, and obtaining the roughened web. At the same time, a grouting hole is opened at the corresponding position of the top plate of the original bridge box girder. The casting cavity is connected to the grouting hole and enters S2. S3 is performed by the following steps: S3.

1. Insert multiple positioning bolts into the chiseled side of the web after chiseling, and open through holes in the alloy plate corresponding to the positions of the positioning bolts. S3.

2. Insert the positioning bolt into the through hole, and then adjust the nut to fix the alloy plate at the preset spacing position; The alloy plate is provided with multiple sub-plates. After all the sub-plates are fixed to the chiseled side of the chiseled web plate, all the sub-plates are spliced ​​together to form a whole.

5. A calculation method for reinforcing concrete box girder structures, characterized in that: Includes the following steps: A1. Calculate the geometric characteristics of the combined cross section after reinforcement in the reinforced concrete box girder structure. The combined cross section is composed of the cross section of the roughened web, the cross section of the UHPC filling layer, and the cross section of the alloy plate. A2. Verify the ultimate flexural capacity of the combined cross section. M u When the ultimate bending bearing capacity M u If the conditions are not met, increase the thickness of the UHPC filling layer and the thickness of the alloy plate in the concrete box girder structure strengthening method according to any one of claims 1 to 4, and then return to A1; when the ultimate flexural bearing capacity M u When the conditions are met, proceed to A3; A3. Verify the total shear capacity of the box girder in the reinforced concrete box girder structure. V u and principal tensile stress σ tp When the total shear bearing capacity V u and principal tensile stress σ tp When the conditions are met, proceed to A4; Otherwise, increase the thickness of the UHPC filling layer and the thickness of the alloy plate in the concrete box girder structure reinforcement method according to any one of claims 1 to 4, and then return to A1; A4. Verify the interface shear resistance in the reinforced concrete box girder structure. If the interface shear resistance does not meet the conditions, reduce the spacing of the first shear connector, reduce the spacing of the second shear connector, increase the diameter of the first shear connector, or increase the diameter of the second shear connector, and then recalculate the interface shear resistance. If the interface shear resistance meets the conditions, proceed to A5. A5. Verify the peel stress in the reinforced concrete box girder structure. σ When peel stress σ If the conditions are not met, reduce the spacing of the first shear connector in the concrete box girder structure reinforcement method according to any one of claims 1 to 4, reduce the spacing of the second shear connector in the concrete box girder structure reinforcement method according to any one of claims 1 to 4, and increase at least one of the roughness of the roughened side of the web after roughening in the concrete box girder structure reinforcement method according to any one of claims 1 to 4, and then return to A1; when the peel stress σ If the conditions are met, the calculation is passed, and the original bridge box girder concrete is reinforced.

6. The calculation method for reinforced concrete box girder structures according to claim 5, characterized in that, A1 is performed by the following steps: A1.1 Calculate the neutral axis position of the combined cross section according to equations (1)-(3). y , ...Equation (1); ...Equation (2); ...Equation (3); in, n u The stiffness ratio of the UHPC filling layer to the concrete stiffness in the original web is given. n l The ratio of the stiffness of the alloy plate to the stiffness of the concrete in the original web is given. E c Let be the elastic modulus of the concrete in the original web. E u The elastic modulus of the UHPC filler layer is... E l Let be the elastic modulus of the alloy plate. b w The thickness of the web plate after roughening. h c The length of the web plate in the height direction of the combined cross section after chiseling is given. h u The thickness of the UHPC filler layer, h l The thickness of the alloy plate is given. A The cross-sectional area of ​​the original web. A c The cross-sectional area of ​​the UHPC filling layer A u and the cross-sectional area of ​​the alloy plate A l The sum of the cross-sectional areas of the original web. A c for b w h c Item, the cross-sectional area of ​​the UHPC filling layer A u for h u h c Item, the cross-sectional area of ​​the alloy plate A l for h l h c item; A1.2 Calculate the moment of inertia of the combined cross section according to equation (4). I , ...Equation (4); in, I c The moment of inertia after the web is roughened and moved parallel to the axis is considered. I u The moment of inertia of the UHPC filling layer after parallel axis shift. I l The moment of inertia of the alloy plate after parallel axis shift is given.

7. The calculation method for reinforced concrete box girder structures according to claim 6, characterized in that, A2 is performed by the following steps: A2.1 Calculate the resultant force of the concrete compression zone in the original web using equation (5). C c , ...Equation (5); in, f c，c This represents the compressive strength of the concrete in the original web. x The height of the compression zone of the combined cross section; The resultant force of the compression zone of the UHPC filling layer is calculated using equation (6). C u , ...Equation (6); in, f c，u The compressive strength of the UHPC filler layer; A2.2 Calculate the total compressive strength using formula (7) C The specific expression is as follows: ...Equation (7); The inherent steel reinforcement in the reinforced concrete box girder structure is calculated using equation (8). T s The resultant force in the tensile zone of the alloy plate T l The resultant force of the tension zone of the prestressed tendons in the reinforced concrete box girder structure T p , ...Equation (8); in, f y，s The yield strength of the inherent reinforcing steel is given by [the specific value]. A s The cross-sectional area of ​​the inherent reinforcing steel is given. f y，l The yield strength of the alloy plate is given by [the value of the alloy plate]. f py The yield strength of the prestressed tendon is... A p The cross-sectional area of ​​the prestressing tendon; The resultant force in the tensile zone of the UHPC filler layer is calculated using equation (9). T u , ...Equation (9); in, k The tensile flexural reduction factor of the UHPC filler layer is... k It is 0.6-0.

8. f t，u The tensile strength of the UHPC filler layer; A2.3 Calculate the total tensile force of the reinforced concrete box girder structure using equation (10). T , ...Equation (10); A2.4 Calculate the height of the compression zone of the combined cross section using equation (11). x , ...Equation (11); A2.5 Calculate the ultimate flexural capacity using equation (12). M u When the ultimate bending bearing capacity M u Less than r 0 M 0 If the condition is not met, then the condition is not satisfied. r 0 The structural importance coefficient and r 0 It is 1.

1. M 0 Design the bending moment for the actual load, then increase the thickness of the UHPC filler layer and the alloy plate, then return to A1; when the ultimate bending bearing capacity... M u Greater than or equal to r 0 M 0 If the condition is met, proceed to A3; ...Equation (12); in, M u0 This represents the ultimate flexural bearing capacity of the original bridge box girder. h 0 Δ is the effective thickness of the cross-section of the original web. M The additional bending moment introduced by the reinforcement layer, which is composed of the UHPC filler layer and the alloy plate. H The height of the original box girder is given.

8. The verification method for reinforced concrete box girder structures according to claim 7, characterized in that, A3 is performed by the following steps: A3.1 Calculate the shear contribution of the concrete in the original web according to formula (13). V c,c , ...Equation (13); in, f t，c The tensile strength of the concrete in the original web is given. f yv The yield strength of the inherent stirrups in the reinforced concrete box girder structure is given by [reference to a specific value]. A sv Let be the area of ​​the inherent stirrups. S v The spacing of the inherent stirrups; The shear contribution of the UHPC filling layer is calculated according to equation (14). V U , ...Equation (14); in, θ The angle of the diagonal crack; The shear contribution of the alloy plate is calculated according to equation (15). V l , ...Equation (15); in, For the buckling reduction coefficient and It is 0.6-0.8; The shear contribution of the prestressing tendon is calculated according to equation (16). V p , ...Equation (16); Where, σ pe The effective prestress of the prestressing tendon; A3.2 Calculate the total shear capacity according to formula (17). V u Calculate the principal tensile stress according to equation (18) σ tp ,when V u Greater than or equal to r 0 V 0 ,and σ tp Less than or equal to 0.4 f t，k Then the condition is met, where f t，k This refers to the limit value of the principal tensile stress in concrete. V 0 To design shear force, proceed to A4; otherwise, if the condition is not met, increase the thickness of the UHPC filler layer and the thickness of the alloy plate, then return to A1. ...Equation (17); ...Equation (18); in, σ cx It is longitudinal normal stress. σ cy τ is the vertical normal stress, and τ is the average shear stress at the interface.

9. The calculation method for reinforced concrete box girder structures according to claim 8, characterized in that, The A4 process is performed by the following steps: A4.1 Calculate the shear flow per unit length of the reinforced concrete box girder structure using equation (19). v , ...Equation (19); in, V max The maximum shear force design value of the cross section of the original web and V max = V 0 , S l The area moment of the alloy plate about the neutral axis of the combined cross section; A4.2 Calculate the shear bearing capacity of a single shear connector using equation (20). v sd Furthermore, the first shear connector and the second shear connector have the same dimensions, the same material, and the same shear bearing capacity; when the shear bearing capacity v sd Less than or equal to 0.7 A sd f u，sd If the condition is met, proceed to A4.3, where... A sd Let be the cross-sectional area of ​​the shear connector. f u，sd The tensile strength of the first shear connector and the second shear connector is used; otherwise, the condition is not met. Then, the spacing between the first shear connector and the second shear connector is reduced, or the diameter of the first shear connector or the diameter of the second shear connector is increased, or at least one of these is increased, and then the process returns to A4.

1. ...Equation (20); A4.3 Calculate the shear flow per unit length of the reinforced concrete box girder structure using equation (21). v rd When shear flow v rd Shear flow greater than or equal to v If the condition is met, proceed to A5; otherwise, reduce the spacing of the first shear connector in the reinforced concrete box girder structure, reduce the spacing of the second shear connector, increase the diameter of the first shear connector, or increase the diameter of the second shear connector, and then return to A4.

1. ...Equation (21); in, S 1 The spacing of the first shear connector is [specified]. S 2 The spacing of the second shear connector. v sd1 This represents the shear bearing capacity of the first shear connector. v sd2 This represents the shear bearing capacity of the second shear connector.

10. The calculation method for reinforced concrete box girder structures according to claim 9, characterized in that, The A5 process is performed by the following steps: A5.1 Calculate the peel stress in the reinforced concrete box girder structure according to formula (22). σ , ...Equation (22); in, L t For stress transfer length, λ For interfacial bonding stiffness; A5.2 Calculate the design value of the interfacial peel resistance bearing capacity according to formula (23). σ 0 When peel stress σ Less than or equal to σ 0 If the conditions are met and the calculation is passed, the original bridge box girder concrete is reinforced; otherwise, the conditions are not met. Then, at least one of the following is taken into account: reducing the spacing of the first shear connector, reducing the spacing of the second shear connector, and increasing the roughness of the roughened side of the roughened web in the reinforced concrete box girder structure; then return to A1. ...Equation (23); in, c This is the interface roughness coefficient, when the roughening is done mechanically. c The value is 0.6-0.8, when the roughening is simple roughening. c It is 0.4-0.

5. ρ s1 The reinforcement ratio of the first shear connector is given. η 1 The anchorage reduction factor for the first shear connector is... ρ s2 This refers to the reinforcement ratio of the second shear connector. η 2 This is the anchorage reduction factor for the second shear connector. μ The coefficient of interfacial friction, N p This refers to the effective axial pressure generated by the prestressed tendons.

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