A fatigue performance evaluation method for steel-UHPC composite bridge decks

Abstract

The present application relates to the technical field of ultra-high performance concrete, and particularly discloses a fatigue performance evaluation method for a steel-UHPC combined bridge deck, which is used to solve the problem that the existing evaluation method does not consider the influence of structural fatigue performance degradation, and it is difficult to accurately predict the fatigue damage evolution process of the steel-UHPC combined bridge deck in its service life, resulting in that the evaluation result may be unsafe; according to the structural parameters and material properties of the reinforced UHPC layer, the fatigue performance of the reinforced UHPC component under the action of axial tension fatigue load is evaluated, the fatigue performance of the super-thin UHPC bolted connection under the action of shear fatigue load is analyzed, the bending fatigue performance of the steel-UHPC-paving combined plate is analyzed based on the five-point bending test, and the time-varying fatigue analysis framework of the steel-UHPC combined bridge deck with the degradation of steel-concrete combined effect is established, so that the evaluation result is more reliable, and the risk of being unsafe is reduced.

Description

Technical Field

[0001] This invention relates to the field of ultra-high performance concrete technology, and more specifically, to a method for evaluating the fatigue performance of steel-UHPC composite bridge decks. Background Technology

[0002] To enhance the mechanical properties and durability of concrete materials, Ultra High Performance Concrete (UHPC) has been developed. UHPC materials are designed based on the maximum bulk density theory to achieve high density, high impermeability, high durability, and high compressive strength. Furthermore, the addition of appropriate amounts of high-strength fibers to the matrix results in high tensile and crack resistance. Applying UHPC materials to fatigue strengthening of existing steel bridge decks and new bridge deck structures creates an orthotropic steel-UHPC composite bridge deck system (hereinafter referred to as "steel-UHPC composite bridge deck"), comprising three key load-bearing components: steel bridge deck, reinforced UHPC layer, and stud connectors. This system can significantly reduce the self-weight of the bridge deck and improve the crack resistance and durability of the concrete structural layer. Engineering practice shows that this type of bridge deck system has excellent fatigue resistance and service performance. However, a few early-built steel-UHPC composite bridge decks have experienced localized stiffness degradation after more than ten years of service. Wang et al. conducted a 7-year on-site monitoring of the Mafang Bridge, my country's first bridge to use UHPC materials for fatigue strengthening. The monitoring results showed that: ① After adding reinforced UHPC layers, the mechanical properties and deformation of the longitudinal ribs and top plate were significantly improved; ② The strengthened steel-UHPC composite bridge deck did not experience significant mechanical property degradation. Compared to the Mafang Bridge, which used L-shaped open ribs, the Foshan-Chenzhou West Bridge is my country's first newly built bridge to use a steel-UHPC composite bridge deck structure with U-shaped closed ribs. Zhang Longwei et al. conducted dynamic performance tests on the bridge deck using a 35-ton standard vehicle and a 45-ton super-heavy vehicle, focusing on the stress response at the arc-shaped cut of the transverse diaphragm. The monitoring results showed that the stress amplitude of each fatigue-vulnerable detail was significantly reduced and within the fatigue cutoff limit, ensuring its fatigue performance within the design reference period. Zhu Zhiwen et al. conducted a study on the stress response characteristics and fatigue performance of various fatigue-vulnerable details of steel-UHPC composite bridge decks under random traffic flow on actual bridges. The monitoring results show that the bridge deck structure system adopted by the Foshan-Chenzhou West Bridge has sufficient fatigue strength and meets the service requirements within the design reference period.

[0003] The mechanism of cracking in the reinforced UHPC layer and fatigue failure of stud connectors in steel-UHPC composite bridge deck is as follows: Figure 1As shown, under the coupled action of the first system main beam stress and the second system bridge deck structure local deflection, the reinforced UHPC layer near the diaphragm will bear high flexural tensile stress, resulting in transversely distributed cracks. Under local wheel load, the third system bridge deck structure undergoes local deflection, and longitudinal cracks appear in the reinforced UHPC layer near the longitudinal ribs. Furthermore, under local wheel load, the steel bridge deck and the reinforced UHPC layer undergo coordinated deformation through stud connections. The difference in curvature between the two causes the stud connections to bear significant shear force, leading to fatigue damage and degradation of their mechanical properties, resulting in a redistribution of internal forces within the stud connection group. Under cyclic wheel load, cracks in the reinforced UHPC layer steadily develop, and fatigue damage to the stud connection group continuously accumulates, thus weakening the steel-concrete composite effect, causing local mechanical property degradation, reducing the fatigue resistance of the steel-UHPC composite bridge deck, and ultimately leading to fatigue cracking of the steel bridge deck. Figure 2 As shown in the diagram comparing fatigue performance assessment methods, the current assessment methods do not consider the impact of structural fatigue performance degradation, making it difficult to accurately predict the fatigue damage evolution process of steel-UHPC composite bridge decks during their life cycle, which may lead to unsafe assessment results.

[0004] To address the aforementioned problems, a technical solution is provided. Summary of the Invention

[0005] To overcome the aforementioned deficiencies of the prior art, the present invention provides a fatigue performance evaluation method for steel-UHPC composite bridge decks. This method addresses the problem that existing evaluation methods do not consider the impact of structural fatigue performance degradation, making it difficult to accurately predict the fatigue damage evolution process of steel-UHPC composite bridge decks during their life cycle, which may lead to unsafe evaluation results. This invention solves the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for evaluating the fatigue performance of steel-UHPC composite bridge decks includes the following steps:

[0008] Step 1: Based on the structural parameters and material properties of the reinforced UHPC layer, conduct fatigue performance evaluation of the reinforced UHPC member under axial tensile fatigue load. Through axial tensile static tests of the reinforced UHPC member, determine the distribution characteristics of internal forces in the steel bars and UHPC during tensile cracking, as well as the crack spacing and crack width of the reinforced UHPC member. Through axial tensile fatigue tests of the reinforced UHPC member, determine the internal force transfer law and crack development law of the steel bars and UHPC material under fatigue load.

[0009] Step 2: The fatigue performance of a 16mm diameter stud connector in an ultra-thin UHPC under shear fatigue loading was analyzed by static performance test to obtain the evolution of the first mechanical performance index of the stud connector with the number of loading cycles; the first mechanical performance index is the regular shear stiffness and residual slip.

[0010] Step 3: Analyze the bending fatigue performance of the steel-UHPC-pavement composite plate through a five-point bending test;

[0011] Step 4: Establish a time-varying fatigue analysis framework for steel-UHPC composite bridge decks with steel-concrete composite effect degradation, and verify it based on full-scale model fatigue test data;

[0012] Step 5: Based on Step 3 and Step 4, conduct an integrated design of the steel-UHPC composite bridge deck and bridge deck pavement.

[0013] As a further aspect of the present invention, in step 1, based on the structural parameters and material properties of the reinforced UHPC layer, the fatigue performance of the reinforced UHPC member under axial tensile fatigue load is evaluated. Specifically, this involves constructing a surface crack width evolution model for the UHPC member, using the control crack width threshold (reaching the durability design requirements of the UHPC material) and the fracture failure of the reinforced UHPC member as fatigue failure criteria. The formula for the surface crack width evolution model of the UHPC member is as follows:

[0014] w c,f =w c,0 +k·log(N)=β·S c ·ε s +k·log(N);

[0015] In the formula: w c,f S represents the surface crack width of the UHPC component, β represents the surface crack width adjustment coefficient of the UHPC component, and S represents the surface crack width of the UHPC component. c ε represents the surface crack spacing of the UHPC component. s denoted as the strain of the reinforcing steel, k as the crack width growth coefficient, and N as the number of fatigue cycles;

[0016] The surface crack width of the UHPC component is extracted and compared with the control crack width threshold required by the durability design of the UHPC material. If the surface crack width of the UHPC component is greater than or equal to the control crack width threshold required by the durability design of the UHPC material, the fatigue performance of the UHPC component is unqualified; if the surface crack width of the UHPC component is less than the control crack width threshold required by the durability design of the UHPC material, the fatigue performance of the UHPC component is qualified; and if the reinforced UHPC component fractures, the fatigue performance of the UHPC component is unqualified.

[0017] As a further aspect of the present invention, in step 1, the axial tensile static test of the reinforced UHPC member includes axial tensile tests of reinforced UHPC members with two typical reinforcement ratios, each type of test includes 3 specimens, for a total of 6 specimens; the axial tensile fatigue test of the reinforced UHPC member includes axial tensile tests of reinforced UHPC members with two typical reinforcement ratios, each type of test includes 4 specimens, for a total of 8 specimens.

[0018] As a further aspect of the present invention, in step 2, the static performance test of the stud connector in the ultra-thin UHPC includes a static ejection test of a stud with a diameter of 16mm in the ultra-thin UHPC, which includes 3 specimens, for a total of 3 specimens; the fatigue performance test of the stud connector in the ultra-thin UHPC includes a fatigue ejection test of a stud with a diameter of 16mm in the ultra-thin UHPC, with each type of test including 5 specimens, for a total of 5 specimens.

[0019] As a further aspect of the present invention, in step 3, the five-point bending test of the steel-UHPC-pavement composite slab includes two types of composite bridge deck tests with different structural parameters. Each type of test uses three load amplitudes, for a total of six specimens. By conducting the five-point bending fatigue test of the steel-UHPC-pavement composite slab, the interlayer shear performance of the pavement layer in the steel-UHPC bridge deck is verified to meet the requirements, and the reasonable thickness of the pavement layer is confirmed. The three-point positive and negative bending tests of the steel-pavement composite slab consider three load amplitudes for each type of test, for a total of six specimens. By conducting the three-point positive and negative bending tests of the steel-pavement composite slab, the longitudinal tensile performance of the pavement layer is determined, and the deflection limit of the steel-pavement composite slab is determined.

[0020] As a further aspect of the present invention, in step 4, a time-varying fatigue analysis framework for steel-UHPC composite bridge decks with degraded steel-concrete composite effects is established and verified based on full-scale model fatigue test data. Specifically, this involves: establishing a time-varying fatigue analysis framework for steel-UHPC composite bridge decks by incorporating the mechanical property degradation model of reinforced UHPC components and studs into the finite element method; deriving a theoretical method applicable to the structural response calculation of steel-UHPC composite bridge decks and bridge deck pavement; deriving the calculation formulas for the section characteristic indices of the longitudinal and transverse standard sections of the key load-bearing components; determining the calculation formulas for the bending moment and shear force at both ends of the key load-bearing components; and establishing a load-slip deformation coordination mechanical model.

[0021] As a further aspect of the present invention, in step 5, the steel-UHPC composite bridge deck and bridge deck pavement are designed as an integrated system based on steps 3 and 4. Specifically, through a full-scale fatigue test of a steel-UHPC composite bridge deck model, the longitudinal and transverse fatigue performance is determined, and the key stress-bearing components that control the fatigue performance of the structure are identified.

[0022] The technical effects and advantages of this invention, a fatigue performance evaluation method for steel-UHPC composite bridge decks, are as follows: This invention evaluates the fatigue performance of reinforced UHPC components under axial tensile fatigue loads based on the structural parameters and material properties of the reinforced UHPC layer, and analyzes the fatigue performance of stud connectors in ultra-thin UHPC under shear fatigue loads. This determines reasonable fatigue strength and design requirements, which helps optimize structural design and extend the service life of steel-UHPC composite bridge decks. Based on five-point bending tests, the invention analyzes the bending fatigue performance of steel-UHPC-pavement composite panels, establishing a time-varying fatigue analysis framework for steel-UHPC composite bridge decks with degraded steel-concrete composite effects. Considering the impact of deteriorated steel-concrete composite effects on structural fatigue performance, this method helps design composite bridge decks with stronger fatigue resistance, adapting to more complex load conditions and harsher environmental influences, making the evaluation results more reliable and reducing the risk of safety hazards. Furthermore, this invention clarifies the thickness and deflection requirements of the pavement layer in steel-UHPC composite bridge decks and orthotropic steel bridge decks, helping to reduce material waste and ensure structural strength, avoiding performance problems caused by unreasonable pavement layer design. Attached Figure Description

[0023] Figure 1 A schematic diagram illustrating the cracking mechanism of the reinforced UHPC layer and fatigue failure mechanism of the stud connectors in the steel-UHPC composite bridge deck provided by the present invention.

[0024] Figure 2 A comparative schematic diagram of the fatigue performance evaluation methods provided by the present invention;

[0025] Figure 3 This invention provides a technical roadmap for a fatigue performance evaluation method for steel-UHPC composite bridge decks.

[0026] Figure 4 A front view of the reinforced UHPC member provided by the present invention;

[0027] Figure 5 A side view of the reinforced UHPC member provided by the present invention;

[0028] In the diagram: 1. Clamping screw; 2. Force transmission ring; 3. UHPC; 4. Reinforcing bar; 5. Reinforcing screw; 6. Anchoring steel plate; 7. Hanging lug. Detailed Implementation

[0029] The technical solutions of this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described technical solutions are only a part of this invention, and not all of it. All other technical solutions obtained by those skilled in the art based on the technical solutions of this invention without inventive effort are within the scope of protection of this invention.

[0030] Figure 1 This is a schematic diagram of a fatigue performance evaluation method for steel-UHPC composite bridge decks provided by the present invention. Figure 1 As shown, a fatigue performance evaluation method for steel-UHPC composite bridge decks includes the following steps:

[0031] Step 1: Based on the structural parameters and material properties of the reinforced UHPC layer, conduct fatigue performance evaluation of the reinforced UHPC member under axial tensile fatigue load. Through axial tensile static tests of the reinforced UHPC member, determine the distribution characteristics of internal forces in the steel bars and UHPC during tensile cracking, as well as the crack spacing and crack width of the reinforced UHPC member. Through axial tensile fatigue tests of the reinforced UHPC member, determine the internal force transfer law and crack development law of the steel bars and UHPC material under fatigue load.

[0032] Step 2: The fatigue performance of a 16mm diameter stud connector in an ultra-thin UHPC under shear fatigue loading was analyzed by static performance test to obtain the evolution of the first mechanical performance index of the stud connector with the number of loading cycles; the first mechanical performance index is the regular shear stiffness and residual slip.

[0033] Step 3: Analyze the bending fatigue performance of the steel-UHPC-pavement composite plate through a five-point bending test;

[0034] Step 4: Establish a time-varying fatigue analysis framework for steel-UHPC composite bridge decks with steel-concrete composite effect degradation, and verify it based on full-scale model fatigue test data;

[0035] Step 5: Based on Step 3 and Step 4, conduct an integrated design of the steel-UHPC composite bridge deck and bridge deck pavement.

[0036] Specifically, in step 1, based on the structural parameters and material properties of the reinforced UHPC layer, the fatigue performance of the reinforced UHPC member under axial tensile fatigue load is evaluated. Specifically, a surface crack width evolution model for the UHPC member is constructed, using the control crack width threshold (reaching the durability design requirements of the UHPC material) and the fracture failure of the reinforced UHPC member as fatigue failure criteria. The formula for the surface crack width evolution model of the UHPC member is:

[0037] w c,f =w c,0 +k·log(N)=β·S c ·ε s +k·log(N);

[0038] In the formula: w c,fS represents the surface crack width of the UHPC component, β represents the surface crack width adjustment coefficient of the UHPC component, and S represents the surface crack width of the UHPC component. c ε represents the surface crack spacing of the UHPC component. s denoted as the strain of the reinforcing steel, k as the crack width growth coefficient, and N as the number of fatigue cycles;

[0039] The surface crack width of the UHPC component is extracted and compared with the control crack width threshold required by the durability design of the UHPC material. If the surface crack width of the UHPC component is greater than or equal to the control crack width threshold required by the durability design of the UHPC material, the fatigue performance of the UHPC component is unqualified; if the surface crack width of the UHPC component is less than the control crack width threshold required by the durability design of the UHPC material, the fatigue performance of the UHPC component is qualified; and if the reinforced UHPC component fractures, the fatigue performance of the UHPC component is unqualified.

[0040] like Figure 4 The front view of the reinforced UHPC member shown and Figure 5 The side view of the reinforced UHPC member shown is shown. In step 1, the axial tensile static test of the reinforced UHPC member includes axial tensile tests of reinforced UHPC members with two types of typical reinforcement ratios. Each type of test includes 3 specimens, for a total of 6 specimens. The axial tensile fatigue test of the reinforced UHPC member includes axial tensile tests of reinforced UHPC members with two types of typical reinforcement ratios. Each type of test includes 4 specimens, for a total of 8 specimens.

[0041] The reinforced UHPC layer is a crucial component of the steel-UHPC composite bridge deck. In the negative bending moment zone, the reinforced UHPC layer is prone to fatigue cracking under localized wheel loads, thus affecting the durability of the bridge deck structure. The reinforced UHPC layer is essentially a reinforced UHPC member. Based on the structural parameters and material properties of the reinforced UHPC layer, axial tensile static tests and axial tensile fatigue tests were conducted on the reinforced UHPC members. Through the axial tensile static tests, the distribution characteristics of internal forces in the steel reinforcement and UHPC during tensile cracking were determined, and the influence of crack spacing, crack width, and parameters on the reinforced UHPC members was identified. Axial tensile fatigue tests were conducted on reinforced UHPC members to determine the internal force transfer and crack propagation patterns of the steel reinforcement and UHPC material under fatigue loads. This led to the determination of the fatigue damage evolution mechanism of reinforced UHPC members. Fatigue failure criteria were established based on two types of fatigue strength characteristic curves: the maximum crack width on the surface of the reinforced UHPC member reaching the durability design requirements of the UHPC material and the occurrence of fracture failure in the reinforced UHPC member. The fatigue strength characteristic curves of the reinforced UHPC members were determined. Based on these two types of fatigue strength characteristic curves, a method for evaluating the tensile fatigue performance of reinforced UHPC members was developed, providing methodological support for the fatigue resistance design of reinforced UHPC layers in steel-UHPC composite bridge decks.

[0042] Specifically, fatigue performance analysis of 16mm diameter stud connectors in ultra-thin UHPCs under shear fatigue loading was conducted through fatigue push-out tests to obtain the evolution of the first mechanical performance index of the stud connectors with the number of loading cycles; the first mechanical performance index is the regular shear stiffness and residual slip; the static performance test of stud connectors in ultra-thin UHPCs includes static push-out tests of 16mm diameter studs in ultra-thin UHPCs, including 3 specimens, for a total of 3 specimens; the fatigue performance test of stud connectors in ultra-thin UHPCs includes fatigue push-out tests of 16mm diameter studs in ultra-thin UHPCs, with each type of test including 5 specimens, for a total of 5 specimens.

[0043] In steel-UHPC composite bridge decks of conventional thickness, 16mm diameter studs are commonly used. While research on their shear fatigue resistance has been conducted, studies on the fatigue performance of 16mm diameter studs in ultra-thin UHPC are limited. This study investigates the fatigue performance of 16mm diameter studs in ultra-thin UHPC based on fatigue pull-out tests, elucidating the evolution of mechanical properties such as shear stiffness and residual slip with the number of loading cycles. Combined with existing data, the fatigue strength curve of 16mm diameter studs in UHPC is further refined. By combining the fatigue strength curve and the evolution of key mechanical properties, the quantitative relationship between the mechanical properties of studs and their fatigue damage degree under different damage states is clarified, leading to the development of a theoretical model for the fatigue deterioration of studs in UHPC.

[0044] Specifically, in step 3, the five-point bending test of the steel-UHPC-pavement composite slab includes two types of composite bridge deck tests with different structural parameters. Each type of test uses three load amplitudes, for a total of six specimens. By conducting the five-point bending fatigue test of the steel-UHPC-pavement composite slab, the interlayer shear performance of the pavement layer in the steel-UHPC bridge deck is verified to meet the requirements, and the reasonable thickness of the pavement layer is confirmed. The three-point positive and negative bending tests of the steel-pavement composite slab consider three load amplitudes for each type of test, for a total of six specimens. By conducting the three-point positive and negative bending tests of the steel-pavement composite slab, the longitudinal tensile performance of the pavement layer is determined, and the deflection limit of the steel-pavement composite slab is determined.

[0045] In engineering practice, the main defects in the pavement layer of steel-UHPC composite bridge deck systems are delamination and shoving, the root cause of which is the failure of the bonding layer between the pavement layer and the reinforced UHPC layer. For steel-epoxy bridge deck systems, the main defects in the pavement layer are longitudinal and transverse structural cracks. As an important component of the bridge deck structure, the mechanical properties of the pavement layer need to be verified. Therefore, considering the structural characteristics of the two types of composite decks, two types of bending fatigue performance tests were conducted, one targeting interlayer shear resistance and the other targeting longitudinal tensile resistance.

[0046] Specifically, in step 4, a time-varying fatigue analysis framework for steel-UHPC composite bridge decks with degraded steel-concrete composite effects is established and verified based on full-scale model fatigue test data. Specifically, this involves: establishing a time-varying fatigue analysis framework for steel-UHPC composite bridge decks by incorporating the mechanical property degradation model of reinforced UHPC components and studs into the finite element method; deriving a theoretical method applicable to the structural response calculation of steel-UHPC composite bridge decks and bridge deck pavement; deriving the calculation formulas for the section characteristic indices of the longitudinal and transverse standard sections of the key load-bearing components; determining the calculation formulas for the bending moment and shear force at both ends of the key load-bearing components; and establishing a load-slip deformation coordination mechanical model.

[0047] At the structural system scale, the mechanical property degradation model of reinforced UHPC components and studs is incorporated into the finite element method to establish a time-varying fatigue analysis framework for steel-UHPC composite bridge decks that can account for the degradation effect of steel-concrete composite effects. The feasibility and accuracy of this method are verified based on full-scale model fatigue test data. Furthermore, the time-dependent evolution mechanism of the fatigue performance of steel-UHPC composite bridge decks is explored. Using the fatigue damage degree of typical fatigue-vulnerable details in the steel bridge deck as a basic indicator, the correlation between the mechanical property degradation of key load-bearing components and the fatigue performance of the composite bridge deck is revealed. The deterioration effect of steel-concrete composite effects on the structural fatigue performance is quantified, laying the foundation for the subsequent establishment of an integrated design method for steel-UHPC composite bridge decks and bridge deck pavement.

[0048] Specifically, in step 5, based on steps 3 and 4, an integrated design of the steel-UHPC composite bridge deck and bridge pavement is carried out. Specifically, through full-scale fatigue tests on the steel-UHPC composite bridge deck model, the longitudinal and transverse fatigue performance is clarified, and the key load-bearing components controlling the fatigue performance of the structure are identified. On this basis, theoretical analysis of the fatigue performance of the steel-UHPC composite bridge deck and bridge pavement is carried out, mainly involving two aspects: calculation of various cross-sectional characteristic indicators of components at the location of interest and calculation of the internal forces borne by components at the location of interest.

[0049] Formulas for calculating the section property indices of the longitudinal and transverse standard sections of key load-bearing components in the steel-UHPC composite bridge deck and pavement were derived. Formulas for calculating the bending moment and shear force at both ends of the key load-bearing components in the steel-UHPC composite bridge deck and pavement were determined. Based on the relationship between the relative displacement between key load-bearing components and their respective loads, a load-slip deformation coordination mechanical model was established. Using the bending moment and shear force calculation formulas and the load-slip deformation coordination mechanical model, the internal forces at the control points of the load-bearing components, the shear force of each stud between the steel and concrete layers, and the shear stress between the UHPC and pavement layers can be obtained. Combined with the section property indices of each component, the response values ​​of the control points of each key load-bearing component can be calculated. The response values ​​of the control points of each key load-bearing component under various parameter combinations were calculated using the above method and compared with their resistance values. Finally, various parameter combinations that meet the design requirements were determined, and the parameter combination with the minimum self-weight was selected as the optimal structural design.

[0050] The cross-sectional properties of the longitudinal and transverse standard sections include cross-sectional area, moment of inertia, and plastic modulus. The formula for calculating the cross-sectional area is:

[0051] A = A st +A uh +A pa ;

[0052] In the formula: A is the cross-sectional area, A st Let A be the cross-sectional area of ​​the steel plate. uh Let A be the cross-sectional area of ​​the UHPC. pa This refers to the cross-sectional area of ​​the pavement layer;

[0053] The formula for calculating the moment of inertia is:

[0054] I x =I st +A st ·y st 2 +I uhpc +A uh ·y uh 2 +I pa +A pa ·y ap 2 ;

[0055] In the formula: I x Let I be the total moment of inertia along the x-axis. st Let A be the moment of inertia of the structural element about the x-axis. st Let A be the cross-sectional area of ​​the steel plate. uh Let A be the cross-sectional area of ​​the UHPC. pa y is the cross-sectional area of ​​the pavement layer. stI is the distance from the center of gravity of the structural element to the x-axis. uhpc Let y be the moment of inertia of the UHPC element (possibly the ultra-high performance concrete component) about the x-axis. uh I is the distance from the center of gravity of the UHPC element to the x-axis. pa For the moment of inertia of the additional part (e.g., a structure or filling material) about the x-axis, y pa This is the distance from the centroid of the additional portion to the x-axis;

[0056] I y =I sty +A st ·y sty 2 +I uhy +A uh ·y uhy 2 +I pay +A pa ·y pay 2 ;

[0057] In the formula: I y Let I be the total moment of inertia along the y-axis. sty Let A be the moment of inertia of the structural element about the y-axis. st Let A be the cross-sectional area of ​​the steel plate. uh Let A be the cross-sectional area of ​​the UHPC. pa y is the cross-sectional area of ​​the pavement layer. sty I is the distance from the center of gravity of a structural element to a specified axis. uhy Let y be the moment of inertia of the UHPC element (possibly the ultra-high performance concrete component) about the y-axis. uhy I is the distance from the center of gravity of the UHPC element to the y-axis. pay For the moment of inertia of the additional part (e.g., a structure or filling material) about the y-axis, y pay This is the distance from the centroid of the additional part to the y-axis.

[0058] The formula for calculating the plastic modulus is:

[0059]

[0060] In the formula: W x I is the plastic modulus of the standard transverse section. x Let x be the total moment of inertia along the x-axis, and y be the total moment of inertia along the x-axis. max W represents the distance from the farthest fiber in the transverse section to the neutral axis. y I is the plastic modulus of the longitudinal standard section. y Let x be the total moment of inertia along the y-axis. max This is the distance from the farthest fiber in the longitudinal section to the neutral axis.

[0061] The formula for calculating the bending moment is:

[0062]

[0063] Where: M is the bending moment, q is the uniformly distributed load, and L is the span of the steel-UHPC composite bridge deck;

[0064] The formula for calculating shear force is:

[0065]

[0066] In the formula: V is the shear force, q is the uniformly distributed load, and L is the span of the steel-UHPC composite bridge deck.

[0067] Based on the relationship between the relative displacements of key load-bearing components and the loads they bear, a load-slip deformation compatibility mechanical model is established. The specific formulas for the load-slip deformation compatibility mechanical model are as follows:

[0068] F s =k s ·s;

[0069]

[0070] In the formula: F s k is the shear force of the stud. s Let be the shear stiffness of the stud, s be the relative slip of the stud, τ be the shear stress of the stud, and A be the shear stiffness of the stud. s Let be the cross-sectional area of ​​the stud.

[0071] This invention analyzes the static and fatigue properties of reinforced UHPC components and stud connectors in steel-UHPC composite bridge decks to determine their respective fatigue strengths; clarifies the thickness requirements and deflection limits of the pavement layer in steel-UHPC composite bridge decks and orthotropic steel bridge decks; establishes a time-varying fatigue analysis framework for steel-UHPC composite bridge decks, considering the impact of steel-concrete composite effect degradation on structural fatigue performance; and further extends the proposed structural design sub-method to the structural design of two typical structural systems: steel-steel fiber reinforced concrete composite bridge decks and orthotropic steel bridge decks, by establishing an integrated design method for steel-UHPC composite bridge decks and bridge deck pavement. This invention, through its embodiments, evaluates the fatigue performance of reinforced UHPC components under axial tensile fatigue loads based on the structural parameters and material properties of the reinforced UHPC layer, and analyzes the fatigue performance of stud connectors in ultra-thin UHPC under shear fatigue loads. This determines reasonable fatigue strength and design requirements, which helps optimize structural design and extend the service life of steel-UHPC composite bridge decks. Furthermore, based on five-point bending tests, it analyzes the bending fatigue performance of steel-UHPC-pavement composite panels, establishing a time-varying fatigue analysis framework for steel-UHPC composite bridge decks with degraded steel-concrete composite effects. Considering the impact of steel-concrete composite effect degradation on structural fatigue performance, this helps design composite bridge decks with stronger fatigue resistance, adapting to more complex load conditions and harsher environmental influences, making the evaluation results more reliable and reducing the risk of safety hazards. Finally, it clarifies the thickness and deflection requirements of the pavement layer in steel-UHPC composite bridge decks and orthotropic steel bridge decks, helping to reduce material waste and ensure structural strength, avoiding performance problems caused by unreasonable pavement layer design.

[0072] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0073] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fatigue performance evaluation of a steel-UHPC composite bridge deck panel, characterized in that, Comprising the following steps: Step 1, according to the structural parameters and material properties of the reinforced UHPC layer, the fatigue performance of the reinforced UHPC component under the action of axial tension fatigue load is evaluated, the steel and UHPC internal force distribution characteristics during the tension cracking process of the reinforced UHPC component are determined through the axial tension static test of the reinforced UHPC component, and the crack spacing and crack width of the reinforced UHPC component are determined; the internal force transfer law and crack development law of the steel and UHPC material of the reinforced UHPC component under fatigue load are determined through the axial tension fatigue test of the reinforced UHPC component; According to the structural parameters and material properties of the reinforced UHPC component, the fatigue performance of the reinforced UHPC component under the action of axial tension fatigue load is evaluated, specifically: by constructing the surface crack width evolution model of the reinforced UHPC component, taking the surface crack width of the reinforced UHPC component reaching the control crack width threshold required by the durability design of the UHPC material and the reinforced UHPC component occurring fracture failure as the fatigue failure criterion, the formula of the surface crack width evolution model of the reinforced UHPC component is: ； In the formula: is the surface crack width of the reinforced UHPC member, is the surface crack width adjustment coefficient of the reinforced UHPC member, is the surface crack spacing of the reinforced UHPC member, is the steel strain, is the crack width growth coefficient, is the number of fatigue cycles; The surface crack width of the reinforced UHPC component is extracted, and the surface crack width of the reinforced UHPC component is compared with the control crack width threshold required by the durability design of the UHPC material. If the surface crack width of the reinforced UHPC component is greater than or equal to the control crack width threshold required by the durability design of the UHPC material, the fatigue performance of the reinforced UHPC component is unqualified; if the surface crack width of the reinforced UHPC component is less than the control crack width threshold required by the durability design of the UHPC material, the fatigue performance of the reinforced UHPC component is qualified; and if the reinforced UHPC component occurs fracture failure, the fatigue performance of the reinforced UHPC component is unqualified; Step 2, the fatigue performance of the 16mm diameter bolt connector in the ultra-thin UHPC under the action of shear fatigue load is analyzed through the static performance test, and the evolution of the first mechanical performance index of the bolt connector with the loading frequency is obtained; the first mechanical performance index is the regular shear stiffness and residual slip; Step 3, the bending fatigue performance of the steel-UHPC-paving composite plate is analyzed through the five-point bending test; Step 4, a time-varying fatigue analysis framework of the steel-UHPC composite effect degradation of the steel-UHPC composite bridge deck is established, and is verified according to the fatigue test data of the full-size model; Step 5, based on steps 3 and 4, the steel-UHPC composite bridge deck and bridge deck pavement integrated design is carried out.

2. The method for fatigue performance evaluation of steel-UHPC composite bridge deck according to claim 1, wherein, In step 1, the axial tension static test of the reinforced UHPC component includes axial tension test of two types of reinforced UHPC components with typical reinforcement ratios, each type of test includes 3 test pieces, a total of 6 test pieces; the axial tension fatigue test of the reinforced UHPC component includes axial tension test of two types of reinforced UHPC components with typical reinforcement ratios, each type of test includes 4 test pieces, a total of 8 test pieces.

3. The method for fatigue performance evaluation of steel-UHPC composite bridge deck according to claim 1, wherein, In step 2, the static performance test of the dowel connector in the ultra-thin UHPC includes the static push-out test of the dowel connector with a diameter of 16 mm in the ultra-thin UHPC, including 3 test pieces, a total of 3 test pieces; the fatigue performance test of the dowel connector in the ultra-thin UHPC includes the fatigue push-out test of the dowel connector with a diameter of 16 mm in the ultra-thin UHPC, each type of test includes 5 test pieces, a total of 5 test pieces.

4. The method for fatigue performance evaluation of steel-UHPC composite bridge deck according to claim 1, wherein, In step 3, the five-point bending test of the steel-UHPC-pavement composite slab includes 2 types of composite bridge deck tests with different structural parameters, each type of test uses 3 load amplitudes, a total of 6 test pieces, by carrying out the five-point bending fatigue test of the steel-UHPC-pavement composite slab, it is verified whether the interlayer shear performance of the pavement layer in the steel-UHPC-pavement composite slab meets the requirements, and the reasonable thickness of the pavement layer is confirmed; the three-point positive and negative bending test of the steel-pavement composite slab, each type of test considers 3 load amplitudes, a total of 6 test pieces, by carrying out the three-point positive and negative bending test of the steel-pavement composite slab, the longitudinal tensile performance of the pavement layer is determined, and the deflection limit value of the steel-pavement layer composite slab is determined.

5. The method for fatigue performance evaluation of steel-UHPC composite bridge deck according to claim 1, wherein, In step 4, the time-varying fatigue analysis framework of the steel-UHPC composite bridge deck is established, which is verified according to the full-size model fatigue test data, specifically: the time-varying fatigue analysis framework of the steel-UHPC composite bridge deck is established, the mechanical performance degradation model of the reinforced UHPC member and the dowel connector is considered in the finite element, and the time-varying fatigue analysis framework of the steel-UHPC composite bridge deck is established; the theoretical method suitable for the structural response calculation of the steel-UHPC composite bridge deck and the bridge deck pavement is derived; The section characteristic index calculation formula of the longitudinal and transverse standard sections of the key stress member control position is derived, the bending moment and shear force calculation formula of the two ends of the key stress member control position is determined, and the load-sliding deformation coordination mechanical model is established.

6. The method for fatigue performance evaluation of steel-UHPC composite bridge deck according to claim 1, wherein, In step 5, the steel-UHPC composite bridge deck and bridge deck pavement integration design is carried out based on step 3 and step 4, specifically: through the full-size model fatigue test of the steel-UHPC composite bridge deck, the longitudinal and transverse fatigue performance is determined, and the key stress member control position of the longitudinal and transverse fatigue performance control structure fatigue performance is determined.

Images