Steel wire mesh-epoxy composite connecting structure for steel-UHPC (Ultra High Performance Concrete) interface and design method of steel wire mesh-epoxy composite connecting structure

Abstract

The invention provides a steel wire mesh-epoxy composite connection structure for a steel-UHPC interface and a design method thereof, the steel wire mesh-epoxy composite connection structure comprises an epoxy resin layer and a folding steel wire mesh; the epoxy resin layer is bonded between the UHPC board and the steel bridge deck; the folded steel wire meshes are parallel to the steel-UHPC combined bridge deck and are arranged in a waveform mode, wave crest sections of the folded steel wire meshes are pre-buried in the UHPC plates, wave trough horizontal sections of the folded steel wire meshes are embedded into the epoxy resin layers, a mechanical interlocking and drawing cooperative force transmission mechanism is formed, and during design, the shear bearing capacity of the interfaces of the epoxy resin layers and the steel bridge deck is larger than that of the interfaces of the UHPC plates and the epoxy resin layers. According to the obtained steel wire mesh-epoxy composite connecting structure, through cooperative work of mechanical anchoring of the folded steel wire fiber mesh and chemical bonding of the epoxy resin layer, optimal balance of rigidity and ductility can be achieved, and the steel wire mesh-epoxy composite connecting structure is excellent in bearing performance, wide in structural applicability and convenient to construct, has replaceability and sustainability and has both safety and economical efficiency.

Description

Technical Field

[0001] This invention relates to the field of bridge structure design technology, specifically to a steel wire mesh-epoxy composite connection structure for steel-UHPC interfaces and its design method. Background Technology

[0002] Prefabricated bridges, due to their advantages such as controllable quality, rapid construction, energy conservation, and environmental friendliness, have become an important development direction in modern bridge construction. Among these advancements, the shear-resistant connection technology between precast ultra-high performance concrete (UHPC) slabs and steel bridge decks is a key element in achieving efficient assembly. The shear-resistant connectors effectively anchor the steel plates and UHPC slabs, suppressing relative slippage under load and reliably transferring interfacial shear force. As UHPC slabs become thinner and lighter, their thickness decreases, limiting the structural space available for arranging connectors and imposing stricter restrictions on the height of the connectors themselves.

[0003] Currently, the common interface connection methods between precast UHPC panels and steel bridge decks are mainly divided into two categories: the first is stud connection, where studs are welded onto the steel bridge deck, and the connection is achieved through mechanical interlocking between the studs and the UHPC panel; the second is epoxy resin bonding, where the precast UHPC panel is bonded to the steel bridge deck as a whole through an epoxy resin layer. However, stud connection has certain requirements on the thickness of the UHPC panel, making it difficult to apply to ultra-thin panels; and during the service of the bridge, if the UHPC panel needs to be replaced due to tensile cracking or damage in the negative bending moment zone, the studs embedded in the UHPC will seriously hinder the dismantling operation—not only significantly reducing construction efficiency, but also easily causing secondary damage to the underlying steel bridge deck by forcibly chiseling it out, such as surface dents, damage to the anti-corrosion layer, or even local steel plate deformation. On the other hand, although epoxy resin bonding has high overall stiffness, its bonding layer is essentially a brittle material with poor ductility and weak energy dissipation capacity, and is prone to sudden debonding under overload or cyclic load, resulting in limited deformation adaptability and reliability of the connection system.

[0004] Given the limitations of existing connection methods in terms of performance and practicality, there is an urgent need to develop a steel wire mesh-epoxy composite connection structure for steel-UHPC composite bridge decks and its design method that combines high load-bearing capacity, high construction efficiency, repairability, and wide applicability. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a steel wire mesh-epoxy composite connection structure and its design method for steel-UHPC interfaces, which has high shear resistance, good ductility, low structural height and repairability, is suitable for thin UHPC boards, and is convenient for construction and subsequent maintenance.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a steel wire mesh-epoxy composite connection structure for a steel-UHPC interface, the steel wire mesh-epoxy composite connection structure comprising an epoxy resin layer and a folded steel wire mesh; the epoxy resin layer is bonded between the UHPC plate and the steel bridge deck; the folded steel wire mesh is arranged in a wave pattern parallel to the steel-UHPC composite bridge deck, with its crests embedded in the UHPC plate and its troughs embedded inside the epoxy resin layer, forming a mechanical interlocking and pull-out coordinated force transmission mechanism; the shear bearing capacity of the interface between the epoxy resin layer and the steel bridge deck is greater than the shear bearing capacity of the interface between the UHPC plate and the epoxy resin layer.

[0008] Secondly, the present invention provides a design method for a steel wire mesh-epoxy composite connection structure for a steel-UHPC interface, comprising the following steps:

[0009] Step 1: Determine the design value [V] of the shear bearing capacity of the steel-UHPC composite bridge deck connection interface;

[0010] Step 2: Determine the material and thickness of the epoxy resin so that V2≥γ[V], where V2 is the shear bearing capacity of the interface between the epoxy resin layer and the steel bridge deck, and γ is the importance level coefficient of the bridge structure.

[0011] Step 3: Select the material, type, folding shape and design parameters of the wire mesh so that V1≥γ[V], where V1 is the shear bearing capacity of the interface between the UHPC board and the epoxy resin layer, which is obtained through theoretical calculation or direct shear test;

[0012] Step 4: Determine whether V1 and V2 satisfy V2>V1; if not, adjust at least one of the following: material, type, folding shape, and design parameters of the wire mesh, and obtain V1 again according to Step 3 until V2>V1>γ[V].

[0013] It should be noted that in step two, the epoxy resin used is a special epoxy structural adhesive, preferably a Class A steel bonding adhesive that conforms to the "Code for Design of Strengthening Concrete Structures" GB 50367-2013; the thickness of the epoxy resin layer is 2-3mm.

[0014] It should be noted that in step two, the shear bearing capacity of the interface between the epoxy resin layer and the steel bridge deck... It can be obtained through direct shear test or calculated according to formula (2.1):

[0015] (2.1);

[0016] In the formula: The shear bearing capacity (kN) at the interface between the epoxy resin layer and the steel bridge deck. The shear bond strength (MPa) between the epoxy resin and the steel bridge deck. The effective bonding area (mm²) between the epoxy resin layer and the steel bridge deck. 2 ).

[0017] It should be noted that in step two, γ is the importance level coefficient of the bridge structure, which is taken as 1.1.

[0018] It should be noted that in step three, the wire mesh is one of stainless steel wire mesh, aluminum alloy wire mesh, or galvanized wire mesh, with galvanized wire mesh being preferred.

[0019] It should be noted that in step three, the diameter D of the wire mesh is 0.5-0.8mm, and the diagonal length a of the mesh opening perpendicular to the shearing direction in the shearing plane is 4-10mm.

[0020] It should be noted that in step three, taking the horizontal section of the steel wire mesh trough in the epoxy resin as a reference, the folding shape of the steel wire mesh crest section can be one of the following: rectangle, right triangle (right trapezoid when the horizontal embedding width in UHPC is not 0), and isosceles triangle (isosceles trapezoid when the horizontal embedding width in UHPC is not 0), preferably rectangle;

[0021] Design parameters include H and B. c B e , φ, θ, where: H is the total height (vertical height) of the wire mesh, including the height of the embedded UHPC board and the epoxy resin layer, where the height of the embedded epoxy resin layer is determined based on the thickness of the epoxy resin layer; B c B is the width of the crest segment of a single folded unit of the wire mesh; e φ is the width of the horizontal trough section of a single folded unit of the wire mesh; φ and θ are the angles between the crest section and the adjacent horizontal trough section of the wire mesh; for a rectangle, φ=θ=90°; for a right triangle (or right trapezoid), θ=140°, φ=90°; for an isosceles triangle (or isosceles trapezoid), θ=120°, φ=120°.

[0022] It should be noted that in step three, the shear bearing capacity of the interface between the UHPC board and the epoxy resin layer... This includes the shear strength provided by the tension of the wire mesh between the interfaces, and the load-bearing capacity provided by the bonding between the epoxy resin layer and the UHPC board between the interfaces. The results are obtained through direct shear tests or by calculation using equations (3.1) to (3.3):

[0023] (3.1);

[0024] (3.2);

[0025] (3.3);

[0026] In the formula: The shear capacity (kN) at the interface between the UHPC board and the epoxy resin layer. The shear bearing capacity provided by the tension of the wire mesh between the interfaces is applicable to different folding shapes; This refers to the load-bearing capacity provided by the bonding between the epoxy resin layer and the UHPC board at the interface; The shear capacity reduction factor of the wire mesh is 0.94, taking into account the stress non-uniformity of the wire and the group reinforcement effect. This refers to the number of wire mesh folding units; The number of steel wires under tension on one side in each folded unit; This represents the ultimate tensile strength of a single steel wire. The effective contact area between the UHPC board and the epoxy resin layer (mm²) 2 ); The shear bond strength (MPa) at the interface between the UHPC board and the epoxy resin layer;

[0027] in, , , Calculated using equations (3.4) to (3.6):

[0028] (3.4);

[0029] (3.5);

[0030] (3.6);

[0031] In the formula: D is the diameter of the wire mesh fiber (mm); a is the diagonal length of the wire mesh opening perpendicular to the shearing direction in the shearing plane (mm); f y This represents the ultimate tensile strength (MPa) of the steel wire.

[0032] It should be noted that when V1 < γ[V] (i.e., the shear capacity provided by the wire mesh is insufficient), at least one of the following measures should be taken: increase the tensile strength of the wire, reduce the mesh size, increase the wire diameter, or reduce the width of the wire mesh folding unit; when V1 ≥ V2 (i.e., the shear capacity provided by the wire mesh is too large), at least one of the following measures should be taken: reduce the tensile strength of the wire, increase the mesh size, reduce the wire diameter, or increase the width of the wire mesh folding unit, while ensuring that V1 ≥ γ[V], or use epoxy resin with higher bonding strength.

[0033] It is important to note that this invention ensures that, under extreme conditions, failure first occurs at the UHPC-epoxy interface, rather than the steel-epoxy interface, by controlling V2 > V1 (i.e., the shear capacity of the epoxy resin layer at the interface with the steel bridge deck is greater than the shear capacity of the UHPC plate at the interface with the epoxy resin layer). This is because debonding at the steel-epoxy interface typically manifests as brittle failure without obvious warning; while the UHPC-epoxy interface, reinforced with steel wire mesh, exhibits quasi-ductile failure characteristics, with slow crack development and strong energy dissipation. Therefore, this invention explicitly excludes the design case where V1 ≥ V2, meaning failure is not allowed at the epoxy-steel plate interface.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] (1) The steel wire mesh-epoxy composite connection structure obtained by the present invention has excellent load-bearing performance and can achieve an optimized balance between rigidity and ductility. Through the synergistic work of "mechanical anchoring of folded steel wire mesh" and "chemical bonding of epoxy resin layer", the shear bearing capacity of epoxy resin layer-UHPC board interface is greatly improved. The pre-embedded flexible steel wire mesh gives the connection structure better ductility and deformation capacity, avoids the risk of brittle failure, and has higher structural safety;

[0036] (2) Wide applicability of the structure. The steel wire mesh-epoxy composite connection structure obtained by the present invention no longer depends on the minimum concrete protective layer thickness required by the studs, thus solving the technical problem that ultra-thin UHPC boards cannot be reliably connected by studs. By adjusting the folding shape and fiber diameter of the steel wire mesh, the shear stiffness and bearing capacity of the connection structure can be flexibly adjusted, thereby adapting to bridge designs with different requirements and having strong versatility;

[0037] (3) Steel wire mesh can be pre-customized, making construction convenient and efficient, and improving the level of bridge assembly;

[0038] (4) When the bridge deck needs to be replaced, the UHPC board and the steel bridge deck can be separated without damage by heating to soften the epoxy resin layer or by using small tools. Since the connection system does not contain permanent connectors such as welds or studs, the separation process will not damage the steel bridge deck itself; after cleaning the interface, the adhesive can be directly reapplied and a new board can be installed, forming a reversible and non-destructive replacement process. This feature significantly reduces the maintenance cost throughout the structure's life cycle and reflects good replaceability and sustainability;

[0039] (5) The method of the present invention quantifies the composite contribution of steel wire mesh and epoxy resin. By distinguishing different failure modes and performing calculations, it provides designers with a clear and reliable design basis, overcomes the blindness of traditional experience-based design, reduces test costs and engineering costs, and ensures the safety and economy of the structure. Attached Figure Description

[0040] Figure 1 A schematic diagram of a steel wire mesh-epoxy composite connection structure used for steel-UHPC interfaces;

[0041] Figure 2 This is a cross-sectional schematic diagram of the steel wire mesh-epoxy composite connection interface;

[0042] Figure 3 A schematic diagram of the design parameters for wire mesh;

[0043] Figure 4 This is a schematic diagram of the structural types of wire mesh;

[0044] Figure 5 A schematic diagram of the connection interface between the steel-UHPC composite bridge deck;

[0045] Figure 6 Figure 1 shows a schematic diagram of the direct shear test loading; Figure (a) is a measured photograph, and Figure (b) is the test model.

[0046] Figure 7 Figure 1 shows a typical failure mode of a direct shear specimen; Figure 2 shows wire failure, Figure 3 shows epoxy debonding failure, and Figure 4 shows mixed failure.

[0047] Figure 8 The diagram shows the fracture modes of wire meshes of different shapes; T1 is a rectangle, T2 is a right triangle (failure of the right-angled side), T3 is a right triangle (failure of the hypotenuse), and T4 is an isosceles triangle; the failure modes of the right triangle and the right trapezoid are the same, because the horizontal embedded section does not affect the stress mechanism of the hypotenuse.

[0048] Figure 9 Figure 1 shows the effect of four different bending shapes of wire mesh on the shear resistance of the bonding interface.

[0049] Figure 10 B is the width of the horizontal section of the trough of a single folded unit of wire mesh. e The effect of the direct shear test on shear resistance is shown in the figure.

[0050] Figure 11 Comparison of interface shear resistance properties under direct shear tests at different wire mesh heights;

[0051] Figure 12 Comparison of interface shear resistance in direct shear tests for different numbers of wire mesh folding units N;

[0052] Figure 13 Comparison of interfacial shear resistance in direct shear tests for different wire diameters D;

[0053] Figure 14 The calculated value of the interfacial shear capacity V of the right-angled triangular wire mesh specimen (T3) u Compared with the experimental value P uThe comparison chart.

[0054] Explanation of reference numerals in the attached drawings: 1 is UHPC board; 2 is steel bridge deck; 3 is wire mesh; 4 is epoxy resin layer. Detailed Implementation

[0055] To provide a clearer understanding of the technical solutions of the present invention, further description is provided below in conjunction with the accompanying drawings and embodiments. It should be understood that, without technical conflict, the technical features of the various embodiments in this specification can be combined and substituted for each other. Furthermore, unless otherwise specified, the technical and scientific terms used in this invention should be understood by those skilled in the art. The terms "comprising" or "including" used in this specification should be understood as indicating that the listed content is not exhaustive and also includes other elements or equivalent alternatives not explicitly stated but belonging to the same or similar technical fields, and should not be construed as excluding other unlisted technical solutions.

[0056] Implementation method one;

[0057] Please see Figure 1-3 This embodiment provides a steel wire mesh-epoxy composite connection structure and its design method for a steel-UHPC interface. The steel wire mesh-epoxy composite connection structure includes a folded steel wire mesh and an epoxy resin layer. The epoxy resin layer is bonded between the UHPC board and the steel bridge deck. The steel wire mesh is arranged in a wave pattern parallel to the steel-UHPC composite bridge deck (i.e., the wave extension direction is the shear direction). The crests of the steel wire mesh are embedded in the UHPC board, and the horizontal troughs are bonded inside the epoxy resin layer, forming a mechanical interlocking and pull-out cooperative force transmission mechanism. The shear bearing capacity of the interface between the epoxy resin layer and the steel bridge deck is greater than the shear bearing capacity of the interface between the UHPC board and the epoxy resin layer.

[0058] Specific design methods include:

[0059] Step 1: Determine the design value of the shear bearing capacity of the steel-UHPC composite bridge deck connection interface. .

[0060] For reference, in the prior art, when the 13mm diameter studs in the UHPC board are arranged at 150mm intervals, the equivalent shear strength they provide (i.e., the design value of the shear bearing capacity of a single stud divided by the 150mm×150mm sharing area) is generally 3.5MPa, and the shear bearing capacity per unit area is 3500kN.

[0061] Step Two: Determine the material and thickness of the epoxy resin layer, so that... ≥γ ,in γ represents the shear bearing capacity of the interface between the epoxy resin layer and the steel bridge deck, and γ is the importance level coefficient of the bridge structure, which is taken as 1.1.

[0062] The epoxy resin is a special epoxy structural adhesive used for building structure reinforcement. To ensure sufficient interfacial bonding strength between the wire mesh and the epoxy resin layer, a Class A steel bonding structural adhesive that meets the requirements of GB 50367-2013 "Code for Design of Strengthening Concrete Structures" is preferred, such as high-temperature structural adhesives from brands like Carbon, Lanjian, or Niugu. Considering that the epoxy resin layer needs to completely cover the horizontal sections of the wire mesh troughs, its thickness should be controlled within the range of 2-3 mm to balance workability and adhesion performance.

[0063] Shear bearing capacity at the interface between the epoxy resin layer and the steel bridge deck It can be obtained through a direct shear test, or calculated according to formula (2.1):

[0064] (2.1);

[0065] In the formula: The shear bearing capacity (kN) at the interface between the epoxy resin layer and the steel bridge deck. The shear bond strength (MPa) between the epoxy resin and the steel bridge deck. The effective bonding area (mm²) between the epoxy resin layer and the steel bridge deck. 2 ).

[0066] Step 3: Initially select the material, type, folding shape, and design parameters of the wire mesh, and determine the shear bearing capacity of the interface between the UHPC board and the epoxy resin layer through theoretical calculations or direct shear tests. and ensure ≥γ .

[0067] The wire mesh can be any commonly used metal wire mesh in construction, including galvanized steel wire mesh, stainless steel wire mesh, or aluminum alloy wire mesh; among them, galvanized steel wire mesh is the preferred option in this embodiment due to its low cost, good bonding performance, and good plastic deformation capacity. The type of wire mesh includes the wire diameter and the mesh size. The wire diameter should preferably be 0.5-0.8 mm, with typical specifications including 0.5 mm, 0.6 mm, 0.7 mm, and 0.8 mm. The mesh is rhomboid, with the lengths of its two diagonals denoted as a (perpendicular to the shear direction) and b (along the shear direction), ranging from 5-10 mm. Common combinations include a×b=5×6 mm, 6×8 mm, 8×10 mm, etc.

[0068] The wire mesh is folded to form alternating peaks and troughs, with the troughs being horizontal sections. The peaks can be rectangular, right-angled triangles (or right-angled trapezoids), or isosceles triangles (or isosceles trapezoids). Based on the horizontal trough sections of the epoxy resin-insulated wire mesh, the design parameters include H and B. c B e, φ, θ, where: H is the total height (vertical height) of the wire mesh, including the height of the embedded UHPC board and the epoxy resin layer, where the height of the embedded epoxy resin layer is determined based on the thickness of the epoxy resin layer; B c Crest width in a single folded unit; B e φ is the width of the horizontal segment of the trough in a single folding unit; φ and θ are the angles between the crests and adjacent horizontal segments of the wire mesh; for a rectangle, φ = θ = 90°; for a right triangle (or right trapezoid), θ = 140°, φ = 90°; for an isosceles triangle (or isosceles trapezoid), θ = 120°, φ = 120°; other acute triangles can also be used. The initial folding of the wire mesh satisfies: B e ≥20mm, B c ≥5mm; H≥6mm.

[0069] Shear bearing capacity at the interface between the UHPC board and the epoxy resin layer This includes the shear strength provided by the tension of the wire mesh between the interfaces, and the load-bearing capacity provided by the bonding between the epoxy resin layer and the UHPC board between the interfaces. The results are obtained through direct shear tests or by calculation using equations (3.1) to (3.3):

[0070] (3.1);

[0071] (3.2);

[0072] (3.3);

[0073] In the formula: The shear capacity (kN) at the interface between the UHPC board and the epoxy resin layer. The formula represents the shear bearing capacity provided by the tension of the wire mesh between interfaces, and it is applicable to various types of wire mesh. The load-bearing capacity (kN) provided by the bonding between the epoxy resin layer and the UHPC board at the interface. The shear capacity reduction factor for the wire mesh is determined experimentally, taking into account the stress non-uniformity of the wires and the group reinforcement effect. This is the factor used in this embodiment. =0.94; This refers to the number of wire mesh folding units; The number of steel wires under tension on one side in each folded unit; The ultimate tensile strength of a single steel wire (kN). The effective contact area between the UHPC board and the epoxy resin layer (mm²) 2 ); The shear bond strength (MPa) at the interface between the UHPC board and the epoxy resin layer; where N and n sF fiber The calculation formula is as follows:

[0074] (3.4);

[0075] (3.5);

[0076] (3.6);

[0077] In the formula: D is the diameter of the wire mesh fiber (mm); a is the diagonal length of the wire mesh opening perpendicular to the shearing direction in the shearing plane (mm).

[0078] When the shear strength provided by the wire mesh is insufficient, the design parameters of the wire mesh need to be redefined, and at least one of the following measures should be taken: increase the tensile strength of the wire, reduce the mesh size, increase the wire diameter D, or reduce the width of the wire mesh folding unit. The wavelength of the wire mesh folding unit is B. c +B e Reducing the wavelength of the wire mesh folding unit increases the number of wire mesh folding units per unit area. A single folded unit refers to the wire mesh interval between any two adjacent points on the interface between the UHPC board and the epoxy resin layer, including a crest segment and a trough horizontal segment.

[0079] Step 4: Judgment , Does it meet the requirements? > If the requirements are not met, adjust at least one of the following: the material, type, folding shape, or design parameters of the wire mesh, and repeat step three to obtain the desired result. Continue until the condition is met, while ensuring that V1≥γ[V].

[0080] It is particularly important to emphasize that this invention, by controlling V2 > V1, ensures that structural failure under extreme conditions occurs first at the UHPC-epoxy interface, rather than the steel-epoxy interface. Debonding at the steel-epoxy interface typically manifests as brittle failure without obvious warning; while the UHPC-epoxy interface exhibits quasi-ductile failure characteristics under the reinforcement of the steel wire mesh. Therefore, this invention explicitly avoids the situation where V1 ≥ V2, i.e., failure is not allowed to occur at the epoxy-steel plate interface. If the calculation results show that V1 ≥ V2, the design parameters of the steel wire mesh also need to be re-determined, and at least one of the following measures should be taken: reducing the tensile strength of the steel wire, increasing the mesh size, decreasing the steel wire diameter, increasing the width of the steel wire mesh folding unit, so that V2 > V1 always holds true, while ensuring that V1 ≥ γ[V]; or using a higher-strength epoxy resin.

[0081] There are various existing methods for bonding UHPC panels to steel bridge decks with epoxy resin. To ensure that the steel-UHPC panel connection has both strength and ductility, this invention incorporates steel wire mesh to meet the strength and ductility requirements of the structural system.

[0082] Steel wire mesh, with its mesh structure, can fully combine with epoxy resin and UHPC materials. Its porous nature provides the physical conditions for the penetration and interlocking of the two materials, thereby enhancing the interfacial adhesion. At the same time, steel wire mesh, with its flexible material, can be bent and folded as expected, so as to adapt to complex shapes and structures, ensuring that it can fully combine with epoxy resin and UHPC, further improving the overall performance and durability of the composite material system. Specific Implementation Example 1;

[0084] This example provides a specific implementation method for a steel wire mesh-epoxy composite connection structure for a steel-UHPC interface. The design objective is that the equivalent shear strength of the connection interface under the ultimate condition is not less than the design value [τ] = 3.5 MPa, and the design value of the shear bearing capacity per unit area [V] = 3500 kN.

[0085] Considering the importance level coefficient of the bridge structure, γ=1.1, the measured shear strength of the selected epoxy adhesive at the epoxy-steel plate interface should meet the following requirement: τ c,e ≥γ⋅[τ] =1.1×3.5=3.85MPa.

[0086] Using CBSR-A / B high-temperature steel bonding adhesive produced by Carbon Technology Group Co., Ltd., τ was measured through a direct shear test. c,e =4.37MPa>3.85MPa (satisfied) ≥γ[V]); while the epoxy-UHPC interfacial bond strength τ s,e =2.76MPa. The total mass of epoxy resin was determined using the mass method, based on an epoxy thickness of 3mm. The specific mass is shown in Table 1.

[0087]

[0088] This embodiment uses commercially available galvanized steel wire mesh as the reinforcing material for the connection interface. The wire mesh is formed by stamping and stretching DX51D+Z type galvanized steel sheet, resulting in a diamond-shaped mesh structure. The two diagonal lengths of the mesh are a=5mm (perpendicular to the shear direction) and b=6mm (along the shear direction), respectively. The equivalent diameter of the steel wire is 0.6mm, and the ultimate bearing capacity F of a single steel wire is... fiber =115N. The initial design parameters for the folded wire mesh are: B c =15mm, B e =30mm, H=12mm.

[0089] Based on the calculation method for the shear bearing capacity of the steel wire mesh-epoxy composite interface, the shear bearing capacity between the epoxy resin and UHPC board interface is calculated:

[0090] Where N, n s for:

[0091] N = 1000 / 45 = 22 (pieces / m);

[0092] n s =2×1000 / 5=400 (roots / m);

[0093] Based on the experimental data =0.94, therefore, the actual shear capacity that the wire mesh can ultimately provide is:

[0094] V 1-1 =0.94×22×400×115N=951kN;

[0095] The load-bearing capacity that the wire mesh should provide:

[0096] =3850-2760=1090kN>951kN

[0097] This indicates insufficient strength of the wire mesh, requiring a reassessment of its design parameters. Possible solutions include reducing the mesh size and increasing the number of folded units per unit area (i.e., reducing B). c +B e ) and increase the diameter D of the wire mesh.

[0098] 1) In this example, if we choose to increase the number of wire mesh folding units per unit area, then B e Reduced to 21mm, at this point:

[0099] N = 1000 / (15 + 21) = 28;

[0100] The shear capacity provided by the wire mesh is:

[0101] V 1-1 =0.94×28×400×115N=1210kN>1090kN;

[0102] At this point, the shear strength provided by the wire mesh meets the design requirements.

[0103] 2) In this example, if we choose to reduce the mesh size from 5mm×6mm to 4mm×8mm, then:

[0104] The number of single-sided steel wires n in each folding unit s for:

[0105] n s=2×1000 / 4=500 (roots / m);

[0106] The load-bearing capacity provided by the wire mesh is:

[0107] V 1-1 =0.94×22×500×115N=1189kN>1090kN;

[0108] At this point, the shear strength provided by the wire mesh also meets the design requirements.

[0109] In summary, in this embodiment, V2 = 4370 kN / m 2 V1=3970kN / m 2 >γ[V]=3850kN / m 2 This satisfies the V2>V1>γ[V] relationship required by the invention, ensuring that the structure preferentially undergoes quasi-ductile failure at the UHPC board-epoxy resin layer interface under overload, avoiding damage to the steel bridge deck, and achieving the design goal of being repairable and replaceable. Specific Implementation Example 2;

[0111] This embodiment uses wire meshes with different characteristics to test the shear mechanical properties of the wire mesh-epoxy composite connection structure, and fabricates direct shear specimens with different characteristics. The specific design features of the wire mesh are shown in Table 2. Where T represents the folded shape of the wire mesh, as shown in... Figure 3 As shown, T1 represents a rectangle, and T2 and T3 represent right-angled triangles in different directions (when the horizontal length B of the embedded UHPC is...). c When ≠0, it is actually a right trapezoid), T4 represents an isosceles triangle; B c H is the width of the crest segment of a single folded unit of the wire mesh, H is the depth of the wire mesh anchored to the UHPC board, i.e., the vertical height of the wire mesh, and B is the width of the crest segment of a single folded unit of the wire mesh. e Let D be the width of the horizontal segment of the trough of a single folded unit of the wire mesh, and N be the number of folded units. This value (B) c +B e ) × N = 180mm (interface size is 180 × 180mm) 2 ).

[0112]

[0113] (1) Test materials;

[0114] UHPC material is made by mixing premixed aggregate, steel fibers, and water in a mass ratio of 100:6:9.5. The premixed aggregate includes cement, lime, gypsum powder, fly ash, quartz sand, and a water-reducing agent, with a specific mass ratio of 42.8:2.1:1.6:6.3:45.6:1.6 (total 100 parts). The diameter of the steel fibers used (d) f ) and length (l fThe thicknesses were 0.2 mm and 13 mm, respectively, with a volumetric admixture of 2%. The galvanized steel wire mesh was pressed from DX51D+Z type hot-dip galvanized steel sheet, and the specimen steel sheet material was Q235 steel. The mechanical properties of the steel and UHPC are shown in Table 3. The epoxy resin used was a high-temperature special steel adhesive, and its mechanical properties are shown in Table 4.

[0115]

[0116]

[0117] (2) Specimen design;

[0118] The specimen employs a sandwich structure, consisting of a 20mm thick steel plate (180mm×250mm), a 50mm thick UHPC board (180mm×250mm), and a 3mm thick epoxy resin adhesive layer (180mm×180mm). To reduce the bending effect at the adhesive interface during shearing, the end sections of the steel plate and UHPC board were locally thickened. For detailed structural information, please refer to [link to relevant documentation]. Figure 3 .

[0119] (3) Loading scheme;

[0120] The direct shear test was performed using an electro-hydraulic servo press with a range of 300 kN. During the test, the end of the specimen corresponding to the UHPC plate was placed on the bearing platform, and the shear load was applied directly to the end of the specimen corresponding to the steel bridge deck. To measure the relative slippage between the steel plate and the UHPC plate during loading, a vertical displacement gauge was placed on each side of the specimen, with its magnetic base fixed to the steel plate behind it, as detailed below. Figure 4 As shown. Before formal loading, a pre-load was applied at a rate of 0.2 mm / min to 10%~20% of the expected ultimate bearing capacity of the specimen to eliminate the initial gap between the testing machine and the specimen. The formal loading process adopted the displacement loading control mode, with an initial loading rate of 0.2 mm / min; when the load reached the ultimate load, the loading rate was adjusted to 0.5 mm / min, and loading continued until the specimen was completely destroyed.

[0121] Based on experimental observations and analysis of the failure morphology of the direct shear specimens, the specimens mainly exhibited three typical failure modes: wire fracture failure, epoxy debonding failure, and mixed failure. The results are as follows: Figure 7 As shown.

[0122] The influence of each parameter on the shear resistance of the connector can be measured by the shear strength τ. u Characteristic slip δ 0.6 and fracture energy G τ To characterize this, the relevant calculation formulas are as follows:

[0123]

[0124]

[0125] In the formula, τ u P is the interfacial shear strength. u Let A be the interfacial shear capacity, and A be the shear area, taken as 180mm × 180mm, δ 0.6 To reduce the load to 0.6P u The corresponding interfacial slip, δ is the interfacial slip (experimental shear displacement), G τ Characteristic slip δ 0.6 The area enclosed by the load-slip curve and the coordinate axis. The results for each specimen are shown in Table 5.

[0126]

[0127] Figure 9-13 The effects of wire mesh characteristics on interfacial strength and ductility (characteristic slip δ) are shown respectively. 0.6 and fracture energy G τ The impact of ).

[0128] Figure 9 The effects of four different bending shapes of wire mesh on the shear strength of the bond interface were demonstrated. The results show that the folding shape of the wire mesh affects the shear strength τ of the bond interface. u The impact is relatively small, but it affects the characteristic slip δ 0.6 and fracture energy G τ It has a significant impact.

[0129] Experimental observations show that under longitudinal shear force, the fracture of the wire mesh usually occurs first on the right side of the interface between the UHPC and the epoxy layer. This is because the right-side wire (the side where the steel plate slips at an obtuse angle to the wire) undergoes shearing first, resulting in greater deformation and bearing more load. The wire deformation of each specimen is shown in the figures below. Figure 8 As shown, the epoxy resin layer remained intact without significant damage, while the wire mesh broke and the bond between the UHPC board and the epoxy resin layer failed. Further analysis revealed that, for the same slip amount, the larger the angle φ, the greater the deformation of the right-side wire; the smaller the angle θ, the greater the deformation of the left-side wire, and correspondingly, the smaller the slip amount at fracture. Considering the angular parameters of each specimen, specimen T2 had the smallest φ and the largest θ, therefore, it exhibited the largest relative slip at the fracture of its two wires, demonstrating the highest δ. 0.6 and G τ Conversely, specimen T3 has the largest φ and the smallest θ, resulting in the smallest slip at the point of breakage of the wires on both sides, with a δ... 0.6 and G τ It is also the lowest; the φ and θ values ​​of specimens T1 and T4 are in the middle, and their δ values ​​are the lowest. 0.6 and G τ The difference is not significant.

[0130] Figure 10 This shows the width B of the horizontal segment of the trough of a single folded unit of the wire mesh. e The effect of B on the shear resistance of the direct shear test e The decrease in the interfacial shear strength τ u It shows a downward trend, with characteristic slip δ 0.6 The fracture energy G is on the rise. τ This shows a trend of first rising and then falling. The above changes are mainly due to the width B. e The change leads to a shift in the failure mode of the bond interface: B e The 30mm thick specimen experienced epoxy debonding failure, exhibiting high shear strength and brittle fracture characteristics, therefore its τ u Maximum and δ 0.6 G τ Minimum. When B e When the diameter is reduced to 20 mm, the embedding force of the epoxy resin in the wire mesh weakens, and the failure mode changes to a coexistence of wire breakage and epoxy failure. u Correspondingly reduced. During this process, the plastic deformation of the wire mesh absorbs and dissipates energy, significantly increasing δ. 0.6 and G τ When B e When the thickness is further reduced to 7mm, the embedding effect of the epoxy groups on the wire mesh is weakest. Some epoxy groups undergo brittle failure along the wire mesh under longitudinal shear force, exhibiting a cohesive failure mode, leading to τ u G τ and δ 0.6 All decreased.

[0131] Figure 11 The study compared the shear strength of the bond interface under direct shear tests at different wire mesh heights. When H increased from 6 mm (embedded in the UHPC board at a depth of 4-5 mm) to 12 mm (embedded in the UHPC board at a depth of 10-11 mm), the shear strength τ of the bond interface increased. u It shows a slight upward trend, with the change range remaining within 3%, and the characteristic slip δ 0.6 With fracture energy G τ The results remained essentially unchanged. This is because, when the wire mesh of all specimens broke, only the concrete and epoxy resin at the interface joint showed localized breakage, and the wire mesh was not pulled out of the UHPC. This indicates that when the anchoring depth of the wire mesh in the UHPC plate reaches 4-5mm (including the height of the wire mesh embedded in the epoxy resin layer, the total height H of the wire mesh reaches 6mm), a reliable wire-UHPC connection system can be formed.

[0132] Figure 12 This study compares the interfacial shear resistance under direct shear tests with different numbers of folded units (N) in the wire mesh. As N increases, the interfacial shear strength τ... uSignificant improvement, characteristic slip δ 0.6 and fracture energy G τ The trend shows an initial increase followed by a decrease. Increased N increases the shear cross-section of the wire mesh, improving its shear strength, thereby enhancing the shear strength between the UHPC board and the epoxy resin matrix, leading to δ... 0.6 and G τ Initially, the shear capacity increases with increasing nitrogen (N). However, when N increases to 6, the shear capacity of the wire mesh exceeds the shear bond capacity of the steel plate-epoxy interface, and the failure mode changes from wire fracture to epoxy debonding, resulting in a decrease in δ0.05. 0.6 and G τ Significant decrease.

[0133] Figure 13 This study compares the interfacial shear properties under direct shear tests with different wire diameters D. As D increases, the shear strength τ at the bond interface increases. u Significantly improved, while characteristic slip δ 0.6 and fracture energy G τ The trend is decreasing. Increasing the wire diameter not only increases the shear cross-sectional area of ​​the wire itself, thus enhancing its shear bearing capacity, but also alters the failure mode of the specimen. When D is small, the specimen mainly exhibits wire fracture failure; as D increases, the shear strength between UHPC and the epoxy matrix strengthens and exceeds the shear strength between the epoxy matrix and the steel plate, leading to a change in the failure mode to epoxy debonding failure, hence its δ... 0.6 and G τ Significantly reduced.

[0134] Experiments have verified that the optimization of wire mesh parameters is essentially based on the interfacial shear strength (τ). u ) and ductility / energy dissipation capability (in terms of characteristic slip δ) 0.6 and fracture energy G τ The optimal balance between the characteristics of the specimen and the epoxy resin layer is sought. When the failure mode of the specimen is characterized by debonding of the ultra-high performance concrete (UHPC) and the epoxy resin layer, accompanied by the fracture of the steel wire, the interfacial bonding system can simultaneously achieve high shear strength and good toughness.

[0135] In the comparative tests of the four waveforms conducted, the isosceles triangle (T4) exhibited relatively superior comprehensive mechanical properties, possessing both high shear strength and ductility. Further analysis showed that, under the premise of wire mesh breakage, although differences existed in the load-bearing capacity and ductility of the different waveform wire mesh specimens, they were not significant. Considering the complexity of the manufacturing process and engineering applicability, this invention preferably adopts a matrix as the basic configuration of the wire mesh.

[0136] Based on the above research findings, the recommended optimal parameter range for the system of this invention is as follows: 30mm ≥ B e≥15mm, H=6~12mm, D=0.5~0.6mm, 45mm≥B c +B e ≥35mm.

[0137] In specific embodiment two, the calculated value V of the interfacial shear bearing capacity of the right-angled triangular (T3) wire mesh specimen. u Compared with the experimental value P u See comparison Figure 14 The ratio of the calculated value to the experimental value (V) u / P u The mean value of the formula is 0.98, and the coefficient of variation is 3.9%, indicating that the calculated value and the experimental value have a high degree of consistency and the formula calculation has high reliability.

[0138] In this embodiment, the design value of the shear bearing capacity per unit square meter of the steel-UHPC connection interface is taken as [V] = 3500kN, and γ is the importance level coefficient of the bridge structure, which is taken as 1.1. Therefore, it is required that: V2>V1≥γ⋅[V]=3850kN (that is, the shear bearing capacity of a single shear interface of 180×180mm in this experiment is 3850kN). 2 The shear capacity of the specimen should not be less than 125 kN. Of all the test specimens, only one group (T3-D) was used. 0.6 -H 12 -B 15 -N5) simultaneously meets the following conditions: (1) V2>V1>γ[V]; (2) the failure mode is wire fracture, reflecting the characteristics of controllable ductile failure. The other 4 groups of specimens: T3-D 0.7 -H 12 -B 30 -N4、T3-D 0.7 -H 12 -B 20 -N4、T3-D 0.6 -H 12 -B 15 -N6、T3-D 0.6 -H 12 -B 10 -N7, although satisfying V1≥γ⋅[V] and V2≥γ⋅[V], the failure mode tends to be brittle due to excessively high V1, or like T3-D. 0.7 -H 12 -B 20 - The epoxy failure of the N4 specimen resulted in inaccurate theoretical calculations, which does not conform to the "controllable ductile failure" principle of this invention, and therefore is not recommended.

[0139] It should be noted that the specific wire mesh parameter range given in Specific Embodiment Two is based on specific test conditions. In actual engineering applications, the parameters can be adaptively adjusted according to the method described in this invention, combined with specific material properties, construction conditions and stress requirements.

[0140] The above embodiments are merely illustrative of the technical solutions of the present invention and do not constitute a limitation on the scope of protection of this application. For those skilled in the art, any equivalent substitutions, modifications, improvements, or alterations made based on the content disclosed in this invention without departing from the technical essence and spirit of this invention should be considered as falling within the scope of protection claimed by this invention.

Claims

1. A steel wire mesh-epoxy composite connection structure for steel-UHPC interfaces, characterized in that: The steel wire mesh-epoxy composite connection structure includes an epoxy resin layer and a folded steel wire mesh; the epoxy resin layer is bonded between the UHPC board and the steel bridge deck; the folded steel wire mesh is arranged in a wave pattern parallel to the steel-UHPC interface, with its crests embedded in the UHPC board and its troughs embedded inside the epoxy resin layer; the shear bearing capacity of the interface between the epoxy resin layer and the steel bridge deck is greater than the shear bearing capacity of the interface between the UHPC board and the epoxy resin layer.

2. A design method for a steel wire mesh-epoxy composite connection structure for a steel-UHPC interface, characterized in that: Includes the following steps: Step 1: Determine the design value [V] of the shear bearing capacity of the steel-UHPC composite bridge deck connection interface; Step 2: Determine the material and thickness of the epoxy resin so that V2≥γ[V], where V2 is the shear bearing capacity of the interface between the epoxy resin layer and the steel bridge deck, and γ is the importance level coefficient of the bridge structure. Step 3: Select the material, type, folding shape and design parameters of the wire mesh so that V1≥γ[V], where V1 is the shear bearing capacity of the interface between the UHPC board and the epoxy resin layer, which is obtained through theoretical calculation or direct shear test; Step 4: Determine whether V1 and V2 satisfy V2>V1; if not, adjust at least one of the following: material, type, folding shape, and design parameters of the wire mesh, and obtain V1 again according to Step 3 until the condition is met.

3. The design method for the steel wire mesh-epoxy composite connection structure for the steel-UHPC interface according to claim 2, characterized in that: In step two, the epoxy resin used is a special epoxy structural adhesive; the thickness of the epoxy resin layer is 2-3 mm.

4. The design method for a steel wire mesh-epoxy composite connection structure for a steel-UHPC interface according to claim 2, characterized in that: In step two, the shear bearing capacity of the interface between the epoxy resin layer and the steel bridge deck is... It can be obtained through direct shear test or calculated according to formula (2.1): （2.1）； In the formula: This refers to the shear bearing capacity of the interface between the epoxy resin layer and the steel bridge deck. The shear bond strength at the interface between the epoxy resin and the steel bridge deck; This refers to the effective bonding area between the epoxy resin layer and the steel bridge deck.

5. The design method for a steel wire mesh-epoxy composite connection structure for a steel-UHPC interface according to claim 2, characterized in that: In step two, γ is the importance level coefficient of the bridge structure, which is set to 1.

1.

6. The design method for a steel wire mesh-epoxy composite connection structure for a steel-UHPC interface according to claim 2, characterized in that: In step three, the wire mesh is one of stainless steel wire mesh, aluminum alloy wire mesh, or galvanized wire mesh.

7. The design method for a steel wire mesh-epoxy composite connection structure for a steel-UHPC interface according to claim 2, characterized in that: In step three, the diameter D of the wire mesh is 0.5-0.8 mm, and the diagonal length a of the mesh opening perpendicular to the shearing direction in the shearing plane is 4-10 mm.

8. The design method for a steel wire mesh-epoxy composite connection structure for a steel-UHPC interface according to claim 2, characterized in that: In step three, taking the horizontal section of the steel wire mesh trough in the epoxy resin as a reference, the folding shape of the steel wire mesh crest section can be one of rectangle, trapezoid, or triangle. Design parameters include H and B. c B e , φ, θ, where: H represents the total height of the wire mesh; B c The width of the crest segment of a single folded unit of the wire mesh; B e The width of the horizontal section of the trough of a single folded unit of wire mesh; φ and θ are the angles between the crests and adjacent horizontal troughs of the wire mesh.

9. The design method for a steel wire mesh-epoxy composite connection structure for a steel-UHPC interface according to claim 2, characterized in that: In step three, the shear bearing capacity of the interface between the UHPC board and the epoxy resin layer... The results are obtained through direct shear tests or by calculation using equations (3.1) to (3.3): （3.1）； （3.2）； （3.3）； In the formula: The shear bearing capacity of the interface between the UHPC board and the epoxy resin layer; The shear bearing capacity provided by the tension of the wire mesh between the interfaces; This refers to the load-bearing capacity provided by the bonding between the epoxy resin layer and the UHPC board at the interface; This is the reduction factor for the shear capacity of the wire mesh; This refers to the number of wire mesh folding units; The effective number of steel wires arranged along the interface shear direction is used to calculate the shear bearing capacity provided by the wire mesh; This represents the ultimate tensile strength of a single steel wire. This represents the effective contact area between the UHPC board and the epoxy resin layer. The shear bond strength at the interface between the UHPC board and the epoxy resin layer; in, , , Calculated using equations (3.4) to (3.6): （3.4）； （3.5）； （3.6）； In the formula: D is the diameter of the wire mesh fiber; a is the diagonal length of the wire mesh opening perpendicular to the shear direction in the shear plane; f y B represents the ultimate tensile strength of the steel wire. c B is the width of the crest segment of a single folded unit of the wire mesh; e This refers to the width of the horizontal segment of the trough of a single folded unit of the wire mesh.

10. The design method for a steel wire mesh-epoxy composite connection structure for a steel-UHPC interface according to claim 2, characterized in that: When V1 < γ[V], take at least one of the following measures: increase the strength grade of the wire mesh, reduce the mesh size, increase the wire diameter, or reduce the width of the wire mesh folding unit; when V1 ≥ V2, take at least one of the following measures: reduce the strength grade of the wire mesh, increase the mesh size, reduce the wire diameter, or increase the width of the wire mesh folding unit, while ensuring that V1 ≥ γ[V], or use epoxy resin with higher bonding strength.

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