Fatigue performance evaluation method for steel-UHPC (Ultra High Performance Concrete) combined bridge deck slab

Abstract

The invention relates to the technical field of ultra-high performance concrete, particularly discloses a fatigue performance evaluation method for a steel-UHPC combined bridge deck slab, and is used for solving the problem that the fatigue damage evolution process of the steel-UHPC combined bridge deck slab in the life cycle is difficult to accurately predict due to the fact that an existing evaluation method does not consider the influence of structural fatigue performance degradation. And the evaluation result is likely to be unsafe. According to structural parameters and material attributes of a reinforced UHPC layer, fatigue performance evaluation of a reinforced UHPC component under the action of an axial tension fatigue load is carried out, fatigue performance analysis of a stud connecting piece in ultra-thin UHPC under the action of a shear fatigue load is carried out, bending fatigue performance analysis of a steel-UHPC-pavement composition board is carried out based on a five-point bending test, and the bending fatigue performance of the steel-UHPC-pavement composition board is analyzed. And a time-varying fatigue analysis framework of the steel-concrete composite effect degraded steel-UHPC composite bridge deck is established, so that the evaluation result is more reliable, and the risk of unsafety is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-high performance concrete, and more specifically, to a fatigue performance evaluation method for a steel-UHPC composite bridge deck. Background Art

[0002] In order to enhance the mechanical properties and durability of concrete materials, ultra-high performance concrete (UHPC) has been developed. The matrix mix ratio of UHPC materials is designed based on the maximum packing density theory to obtain high density, high impermeability, high durability and high compressive strength, and an appropriate amount of high-strength fibers are added to the matrix to obtain high tensile and crack resistance. UHPC materials are applied to fatigue reinforcement of existing steel bridge decks and new bridge deck structure projects to form an orthotropic steel-UHPC composite bridge deck (hereinafter referred to as "steel-UHPC composite bridge deck") system including three key load-bearing components: steel bridge deck, reinforced UHPC layer and bolt connectors. This can significantly reduce the deadweight of the bridge deck and improve the crack resistance and durability of the concrete structure layer. Engineering practice shows that this type of bridge deck system has excellent fatigue resistance and service performance, but a few early-built steel-UHPC composite bridge decks have experienced local stiffness degradation after more than ten years of service. Wang et al. conducted a 7-year real bridge monitoring on the Mafang Bridge, the first bridge in my country to be fatigue-reinforced with UHPC materials. The monitoring results showed that: ① After adding the reinforced UHPC layer, the mechanical properties and deformation of the longitudinal ribs and the top plate were significantly improved; ② The reinforced steel-UHPC composite bridge deck did not show obvious mechanical property degradation. Compared with the Mafang Bridge with L-shaped open ribs, the Fochen West Bridge is the first newly built bridge in my country to use a steel-UHPC composite bridge deck structure with U-shaped closed ribs. Zhang Longwei et al. used a 35-ton standard vehicle and a 45-ton overweight vehicle to carry out the dynamic performance test of the bridge deck, focusing on the stress response at the arc-shaped cutout of the diaphragm. The monitoring results showed that the stress amplitudes of each fatigue-vulnerable detail were significantly reduced and within the fatigue cutoff limit, ensuring its fatigue performance within the design reference period. Zhu Zhiwen and others conducted research on the stress response characteristics and fatigue performance of various fatigue-vulnerable details of the steel-UHPC composite bridge deck under the action of random traffic on a real bridge. The monitoring results showed that the bridge deck structure system used in the Fochen West Bridge has sufficient fatigue strength to meet the use requirements within the design reference period.

[0003] The cracking mechanism of reinforced UHPC layer and fatigue failure of stud connectors in steel-UHPC composite bridge decks is as follows: Figure 1As shown in the figure, under the coupling effect of the stress on the main beam of the first system and the local deflection of the bridge deck structure of the second system, the reinforced UHPC layer near the top of the diaphragm will be subjected to higher bending tensile stress, resulting in transverse distributed cracks. Under the action of local wheel loads, the bridge deck structure of the third system will bend locally, and longitudinal cracks will appear in the reinforced UHPC layer near the top of the longitudinal ribs. In addition, under the action of local wheel loads, the steel bridge deck and the reinforced UHPC layer produce coordinated deformation through the stud connectors, and the difference in the bending curvature between the two causes the stud connectors themselves to be subjected to a large shear force, which in turn causes fatigue damage, causing degradation of their own mechanical properties, and leading to internal force redistribution in the stud connector group. Under the action of reciprocating wheel loads, cracks in the reinforced UHPC layer develop steadily, and fatigue damage in the stud connector group continues to accumulate, thereby continuously weakening the steel-concrete composite effect, causing degradation of the local mechanical properties of the structure, reducing the fatigue resistance of the steel-UHPC composite bridge deck, and ultimately leading to fatigue cracking of the steel bridge deck, as shown in Figure 2. Figure 2 As shown in the schematic diagram of fatigue performance evaluation method comparison, since the current evaluation method does not take into account the impact of structural fatigue performance degradation, it is difficult to accurately predict the fatigue damage evolution process of the steel-UHPC composite bridge deck during its life cycle, resulting in the evaluation results being unsafe.

[0004] In order to solve the above problems, a technical solution is now provided. Summary of the invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a fatigue performance evaluation method for a steel-UHPC composite bridge deck, which is used to solve the problem that the existing evaluation method does not take into account the influence of structural fatigue performance degradation, and it is difficult to accurately predict the fatigue damage evolution process of the steel-UHPC composite bridge deck during its life cycle, resulting in its evaluation results may be unsafe, so as to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A fatigue performance evaluation method for a steel-UHPC composite bridge deck comprises the following steps:

[0008] Step 1: Based on the structural parameters and material properties of the reinforced UHPC layer, the fatigue performance of the reinforced UHPC component under axial tensile fatigue load is evaluated. Through the axial tensile static test of the reinforced UHPC component, the internal force distribution characteristics of the steel bars and UHPC during the tensile cracking of the reinforced UHPC component, as well as the crack spacing and crack width of the reinforced UHPC component are determined; through the axial tensile fatigue test of the reinforced UHPC component, the internal force transfer law of the steel bars and UHPC materials and the crack development law of the reinforced UHPC component under fatigue load are determined;

[0009] Step 2: Fatigue performance analysis of a bolt connector with a diameter of 16 mm in ultra-thin UHPC under shear fatigue load is performed through a static performance test to obtain the evolution of the first mechanical performance index of the bolt connector with the number of loading actions; the first mechanical performance index is the regular shear stiffness and residual slip;

[0010] Step 3, analyzing the bending fatigue performance of the steel-UHPC-paving composite slab by a five-point bending test;

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

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

[0013] As a further solution of the present invention, in step 1, the fatigue performance of the reinforced UHPC component under axial tensile fatigue load is evaluated according to the structural parameters and material properties of the reinforced UHPC layer, specifically: by constructing a surface crack width evolution model of the UHPC component, the control crack width threshold of the surface crack width of the reinforced UHPC component reaching the durability design requirement of the UHPC material and the occurrence of fracture failure of the reinforced UHPC component are used as fatigue failure criteria, and the formula of the surface crack width evolution model of the UHPC component is:

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

[0015] Where: w c,f is the crack width on the surface of the UHPC component, β is the adjustment coefficient of the crack width on the surface of the UHPC component, S c is the surface crack spacing of UHPC components, ε s is the steel bar strain, k is the crack width growth coefficient, and N is the number of fatigue cycles;

[0016] The surface crack width of the UHPC component is extracted, and the surface crack width of the 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 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 and fails, at this time, the fatigue performance of the UHPC component is unqualified.

[0017] As a further solution of the present invention, in step 1, the axial tension static test of the reinforced UHPC component includes axial tension tests of reinforced UHPC components with two typical reinforcement ratios, each type of test includes three specimens, and a total of six specimens; the axial tension fatigue test of the reinforced UHPC component includes axial tension tests of reinforced UHPC components with two typical reinforcement ratios, each type of test includes four specimens, and a total of eight specimens.

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

[0019] As a further solution of the present invention, in step 3, the five-point bending test of the steel-UHPC-paving composite plate includes two types of composite bridge deck tests with different structural parameters. Each type of test adopts three load amplitudes, with a total of 6 specimens. By carrying out the five-point bending fatigue test of the steel-UHPC-paving composite plate, it is verified whether the interlayer shear performance of the pavement layer in the steel-UHPC bridge deck meets the requirements and confirms the reasonable thickness of the pavement layer; the three-point positive and negative bending test of the steel-paving composite plate, each type of test considers three load amplitudes, with a total of 6 specimens. By carrying out the three-point positive and negative bending test of the steel-paving composite plate, the longitudinal tensile performance of the pavement layer is determined, and the deflection limit of the steel-paving layer composite plate is determined.

[0020] As a further solution 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: a time-varying fatigue analysis framework for steel-UHPC composite bridge decks is established, the mechanical performance degradation model of reinforced UHPC components and studs is taken into account in the finite element, and a time-varying fatigue analysis framework for steel-UHPC composite bridge decks with degraded steel-concrete composite effects is established; a theoretical method for structural response calculation applicable to steel-UHPC composite bridge decks and bridge deck pavement is derived. The calculation formulas for the section characteristic indexes of the longitudinal and transverse standard sections at the control parts of key load-bearing components are derived, the calculation formulas for the bending moment and shear force at both ends of the control parts of key load-bearing components are determined, and a load-slip deformation coordination mechanical model is established.

[0021] As a further solution of the present invention, in step 5, an integrated design of the steel-UHPC composite bridge deck and the bridge deck pavement is performed based on steps 3 and 4, specifically: through a full-scale model fatigue test of the steel-UHPC composite bridge deck, the longitudinal and transverse fatigue performance are clarified, and the control position of the key load-bearing components that control the fatigue performance of the structure by the longitudinal and transverse fatigue performance is determined.

[0022] The technical effects and advantages of a fatigue performance evaluation method for a steel-UHPC composite bridge deck of the present invention are as follows: the present invention evaluates the fatigue performance of reinforced UHPC components under axial tension fatigue loads according to the structural parameters and material properties of the reinforced UHPC layer, and analyzes the fatigue performance of bolt connectors in ultra-thin UHPC under shear fatigue loads, thereby determining reasonable fatigue strength and design requirements, which is helpful to optimize the structural design, thereby extending the service life of the steel-UHPC composite bridge deck; based on a five-point bending test, a bending fatigue performance analysis of a steel-UHPC-paving composite plate is performed, and a time-varying fatigue analysis framework for a steel-UHPC composite bridge deck with degraded steel-concrete composite effect is established, and the influence of the deterioration of the steel-concrete composite effect on the fatigue performance of the structure is considered, which is helpful to design a composite bridge deck with stronger fatigue resistance, adapt to more complex load conditions and more severe environmental influences, make the evaluation results more reliable, and reduce the risk of unsafety; the thickness and deflection requirements of the pavement layer in the steel-UHPC composite bridge deck and the orthotropic steel bridge deck are clarified, which is helpful to reduce material waste and ensure structural strength, and avoid performance problems caused by unreasonable pavement layer design. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0025] Figure 3 A technical roadmap for a fatigue performance evaluation method for a steel-UHPC composite bridge deck provided by the present invention. ;

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

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

[0028] In the figure: 1. Clamping screw; 2. Force transmission ring; 3. UHPC; 4. Steel bar; 5. Reinforcement screw; 6. Anchor steel plate; 7. Hanging ear. DETAILED DESCRIPTION

[0029] The following will be combined with the accompanying drawings in the present invention to clearly and completely describe the technical solution in the present invention. Obviously, the described technical solution is only a part of the present invention, not all of it. Based on the technical solution in the present invention, all other technical solutions obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] Figure 1 The present invention provides a structural schematic diagram of a fatigue performance evaluation method for a steel-UHPC composite bridge deck. Figure 1 As shown, a fatigue performance evaluation method for a steel-UHPC composite bridge deck comprises the following steps:

[0031] Step 1: Based on the structural parameters and material properties of the reinforced UHPC layer, the fatigue performance of the reinforced UHPC component under axial tensile fatigue load is evaluated. Through the axial tensile static test of the reinforced UHPC component, the internal force distribution characteristics of the steel bars and UHPC during the tensile cracking of the reinforced UHPC component, as well as the crack spacing and crack width of the reinforced UHPC component are determined; through the axial tensile fatigue test of the reinforced UHPC component, the internal force transfer law of the steel bars and UHPC materials and the crack development law of the reinforced UHPC component under fatigue load are determined;

[0032] Step 2: Fatigue performance analysis of a bolt connector with a diameter of 16 mm in ultra-thin UHPC under shear fatigue load is performed through a static performance test to obtain the evolution of the first mechanical performance index of the bolt connector with the number of loading actions; the first mechanical performance index is the regular shear stiffness and residual slip;

[0033] Step 3, analyzing the bending fatigue performance of the steel-UHPC-paving composite slab by a five-point bending test;

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

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

[0036] Specifically, in step 1, the fatigue performance of reinforced UHPC components under axial tensile fatigue load is evaluated according to the structural parameters and material properties of the reinforced UHPC layer. Specifically, by constructing a surface crack width evolution model for UHPC components, the control crack width threshold of the surface crack width of the reinforced UHPC components reaching the durability design requirements of the UHPC material and the occurrence of fracture failure of the reinforced UHPC components are used as fatigue failure criteria. The formula of the surface crack width evolution model for UHPC components is:

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

[0038] Where: w c,fis the crack width on the surface of the UHPC component, β is the adjustment coefficient of the crack width on the surface of the UHPC component, S c is the surface crack spacing of UHPC components, ε s is the steel bar strain, k is the crack width growth coefficient, and N is the number of fatigue cycles;

[0039] The surface crack width of the UHPC component is extracted, and the surface crack width of the 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 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 and fails, at this time, the fatigue performance of the UHPC component is unqualified.

[0040] like Figure 4 Front view of the reinforced UHPC component shown and Figure 5 The side view of the reinforced UHPC component is shown. In step 1, the axial tension static test of the reinforced UHPC component includes axial tension tests of reinforced UHPC components with two typical reinforcement ratios, each type of test includes three specimens, and a total of six specimens; the axial tension fatigue test of the reinforced UHPC component includes axial tension tests of reinforced UHPC components with two typical reinforcement ratios, each type of test includes four specimens, and a total of eight specimens.

[0041] The reinforced UHPC layer is an important component of the steel-UHPC composite bridge deck. The reinforced UHPC layer in the negative bending zone is prone to fatigue cracking under local wheel loads, which in turn affects the durability of the bridge deck structure. The reinforced UHPC layer is essentially a reinforced UHPC component. According to the structural parameters and material properties of the reinforced UHPC layer, the reinforced UHPC component is designed to carry out axial tension static tests and axial tension fatigue tests of the reinforced UHPC component. Through the axial tension static tests of the reinforced UHPC component, the internal force distribution characteristics of the steel bars and UHPC during the tensile cracking of the reinforced UHPC component are determined, and the crack spacing, crack width and parameter influence rules of the reinforced UHPC component are determined. Axial tensile fatigue tests on reinforced UHPC components were carried out to determine the internal force transfer law and crack development law of reinforced UHPC components and steel bars under fatigue loads, thereby determining the fatigue damage evolution mechanism of reinforced UHPC components. The fatigue failure criteria were the controlled crack width at which the maximum crack width on the surface of the reinforced UHPC component reached the durability design requirement of the UHPC material and the fracture failure of the reinforced UHPC component. The fatigue strength characteristic curve of the reinforced UHPC component was determined, and a tensile fatigue performance evaluation method for reinforced UHPC components was developed based on the two types of fatigue strength characteristic curves, providing methodological support for the fatigue resistance design of the reinforced UHPC layer in the steel-UHPC composite bridge deck.

[0042] Specifically, the fatigue performance analysis of the stud connector with a diameter of 16 mm in ultra-thin UHPC under shear fatigue load was carried out through fatigue push-out test, and the evolution of the first mechanical performance index of the stud connector with the number of loading actions was obtained; the first mechanical performance index is regular shear stiffness and residual slip; the static performance test of the stud connector in ultra-thin UHPC includes static push-out test of studs with a diameter of 16 mm in ultra-thin UHPC, including 3 specimens, totaling 3 specimens; the fatigue performance test of the stud connector in ultra-thin UHPC includes fatigue push-out test of studs with a diameter of 16 mm in ultra-thin UHPC, each type of test includes 5 specimens, totaling 5 specimens.

[0043] Stud connectors with a diameter of 16 mm are often used in conventional thickness steel-UHPC composite bridge decks. There are studies on their shear fatigue performance. However, there are few studies on the fatigue performance of stud connectors with a diameter of 16 mm in ultra-thin UHPC. Based on fatigue push-out tests, fatigue performance studies of stud connectors with a diameter of 16 mm in ultra-thin UHPC are conducted to explore the evolution law of mechanical performance indicators such as shear stiffness and residual slip of such stud connectors with the number of loading actions, and combined with existing data, further improve the fatigue strength curve of studs with a diameter of 16 mm in UHPC. Combined with the fatigue strength curve of studs and the evolution law of key mechanical indicators, the quantitative relationship between the mechanical properties of studs and their fatigue damage degree under different damage states is clarified, and then a fatigue degradation theoretical model of studs in UHPC is developed.

[0044] Specifically, in step 3, the five-point bending test of the steel-UHPC-paving composite slab includes two types of composite bridge deck tests with different structural parameters. Each type of test adopts three load amplitudes, with a total of 6 specimens. By carrying out the five-point bending fatigue test of the steel-UHPC-paving composite slab, it is verified whether the interlayer shear performance of the pavement layer in the steel-UHPC bridge deck meets the requirements and confirms the reasonable thickness of the pavement layer; the three-point positive and negative bending test of the steel-paving composite slab, each type of test considers three load amplitudes, with a total of 6 specimens. By carrying out the three-point positive and negative bending test of the steel-paving composite slab, the longitudinal tensile performance of the pavement layer is determined, and the deflection limit of the steel-paving layer composite slab is determined.

[0045] In engineering practice, the pavement defects in the steel-UHPC composite bridge deck system are mainly delamination and displacement, and the root cause is the damage of the bonding layer between the pavement layer and the reinforced UHPC layer. For the steel-epoxy bridge deck system, the pavement defects are mainly longitudinal and transverse structural cracks in the pavement layer. As an important part of the bridge deck structure, the mechanical properties of the pavement layer need to be verified. Therefore, combined with the structural characteristics of the two types of composite plates, two types of bending fatigue performance tests were carried out, one targeting interlayer shear performance and the other targeting longitudinal tensile performance.

[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: a time-varying fatigue analysis framework for steel-UHPC composite bridge decks is established, the mechanical performance degradation model of reinforced UHPC components and studs is taken into account in the finite element, and a time-varying fatigue analysis framework for steel-UHPC composite bridge decks with degraded steel-concrete composite effects is established; a theoretical method for structural response calculation applicable to steel-UHPC composite bridge decks and bridge deck pavement is derived. The calculation formulas for the cross-sectional characteristic indexes of the longitudinal and transverse standard sections at the control parts of key load-bearing components are derived, the calculation formulas for the bending moment and shear force at both ends of the control parts of key load-bearing components are determined, and a load-slip deformation coordination mechanical model is established.

[0047] At the structural system scale, the mechanical performance degradation model of reinforced UHPC components and studs is taken into account in the finite element method, and a time-varying fatigue analysis framework for steel-UHPC composite bridge decks that can consider the degradation of the steel-concrete composite effect is established. The feasibility and accuracy of this method are verified based on the fatigue test data of the full-scale model. On this basis, the time evolution mechanism of the fatigue performance of the steel-UHPC composite bridge deck is explored, and the fatigue damage degree of typical fatigue-vulnerable details in the steel bridge deck is used as the basic indicator to reveal the corresponding relationship between the degradation of the mechanical properties of key load-bearing components and the fatigue performance of the composite bridge deck, and to quantify the degradation effect of the steel-concrete composite effect on the fatigue performance of the structure, 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, an integrated design of the steel-UHPC composite bridge deck and the bridge deck pavement is carried out based on steps 3 and 4, specifically: through a full-scale model fatigue test of the steel-UHPC composite bridge deck, the longitudinal and transverse fatigue performances are clarified, and the control positions of the key load-bearing components where the longitudinal and transverse fatigue performances control the fatigue performance of the structure are determined; on this basis, a theoretical analysis of the fatigue performance of the steel-UHPC composite bridge deck and the bridge deck pavement is carried out, which mainly involves two aspects: the calculation of various cross-sectional characteristic indicators of the components at the focus positions and the calculation of the internal forces borne by the components at the focus positions.

[0049] The calculation formulas of the cross-sectional characteristic indexes of the longitudinal and transverse standard sections of the key load-bearing components in the steel-UHPC composite bridge deck and the bridge deck pavement are derived, and the calculation formulas of the bending moment and shear force at both ends of the key load-bearing components in the steel-UHPC composite bridge deck and the bridge deck pavement are determined. Based on the relationship between the relative displacement between the key load-bearing components and the loads they bear, a load-slip deformation coordination mechanics model is established; the internal forces at the load-bearing component control parts, the shear force of each bolt between the steel-concrete layer, and the shear stress between the UHPC-paving layers can be obtained by the calculation formulas of the bending moment and shear force and the load-slip deformation coordination mechanics model. Combined with the cross-sectional characteristic indexes of each component, the response values ​​of the control parts of each key load-bearing component can be calculated. The response values ​​of the control parts of each key load-bearing component under various parameter combinations are calculated by the above method, and compared with their resistance values. Finally, various parameter combinations that meet the design requirements are determined, and the parameter combination with the smallest dead weight is selected as the optimal structural design.

[0050] Among them, the cross-sectional characteristic indicators of the longitudinal and transverse standard cross-sections include cross-sectional area, moment of inertia and plastic modulus. The calculation formula of the cross-sectional area is:

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

[0052] Where: A is the cross-sectional area, A st is the cross-sectional area of ​​the steel plate, A uh is the cross-sectional area of ​​UHPC, A pa is 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] Where: I x is the total moment of inertia about the x-axis, I st is the moment of inertia of the structural element about the x-axis, A st is the cross-sectional area of ​​the steel plate, A uh is the cross-sectional area of ​​UHPC, A pa is the cross-sectional area of ​​the pavement layer, y stis the distance from the center of gravity of the structural element to the x-axis, I uhpc is the intrinsic moment of inertia of the UHPC element (possibly the ultra-high performance concrete part) about the x-axis, y uh is the distance from the center of gravity of the UHPC component to the x-axis, I pa is the inertia moment of the additional part (such as a structure or filling material) about the x-axis, y pa is the distance from the center of gravity of the attached part 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] Where: I y is the total moment of inertia about the y-axis, I sty is the moment of inertia of the structural element about the y-axis, A st is the cross-sectional area of ​​the steel plate, A uh is the cross-sectional area of ​​UHPC, A pa is the cross-sectional area of ​​the pavement layer, y sty is the distance from the centroid of the structural element to the specified axis, I uhy is the intrinsic moment of inertia of the UHPC element (possibly the ultra-high performance concrete part) about the y-axis, y uhy is the distance from the center of gravity of the UHPC component to the y-axis, I pay is the inertia moment of the additional part (such as a structure or filling material) about the y-axis, y pay is the distance from the center of gravity of the attached part to the y-axis.

[0058] The calculation formula of plastic modulus is:

[0059]

[0060] Where: W x is the plastic modulus of the transverse standard section, I x is the total moment of inertia about the x-axis, and y max W is the distance from the farthest fiber in the transverse section to the neutral axis. y is the plastic modulus of the longitudinal standard section, I y is the total moment of inertia about the y-axis, x max It is the distance from the farthest fiber in the longitudinal section to the neutral axis.

[0061] The calculation formula for 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 shear force calculation formula is:

[0065]

[0066] Where: 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 displacement between key load-bearing components and the loads they bear, a load-slip deformation coordination mechanics model is established. The specific formula of the load-slip deformation coordination mechanics model is:

[0068] F s =k s ·s;

[0069]

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

[0071] The embodiments of the present invention determine the fatigue strength of reinforced UHPC components and bolt connectors in steel-UHPC composite bridge decks by analyzing the static and fatigue properties; clarify the thickness requirements and deflection limits of pavement layers in steel-UHPC composite bridge decks and orthotropic steel bridge decks; establish a time-varying fatigue analysis framework for steel-UHPC composite bridge decks, and consider the influence of steel-concrete composite effect degradation on structural fatigue performance; and establish an integrated design method for steel-UHPC composite bridge decks and bridge deck pavement, and based on the proposed structural design method, further extend it to the structural design of two typical structural systems: steel-steel fiber concrete composite bridge decks and orthotropic steel bridge decks. The embodiment of the present invention evaluates the fatigue performance of reinforced UHPC components under axial tension fatigue loads according to the structural parameters and material properties of the reinforced UHPC layer, and analyzes the fatigue performance of bolt connectors in ultra-thin UHPC under shear fatigue loads, thereby determining reasonable fatigue strength and design requirements, which is helpful to optimize the structural design and thus extend the service life of the steel-UHPC composite bridge deck; based on the five-point bending test, the bending fatigue performance analysis of the steel-UHPC-paving composite plate is carried out, and a time-varying fatigue analysis framework for the steel-UHPC composite bridge deck with degraded steel-concrete composite effect is established, and the influence of the degradation of the steel-concrete composite effect on the fatigue performance of the structure is considered, which is helpful to design a composite bridge deck with stronger fatigue resistance, adapt to more complex load conditions and more severe environmental influences, make the evaluation results more reliable, and reduce the risk of unsafety; the thickness and deflection requirements of the pavement layer in the steel-UHPC composite bridge deck and the orthotropic steel bridge deck are clarified, which is helpful to reduce material waste and ensure structural strength, and avoid performance problems caused by unreasonable pavement layer design.

[0072] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection 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 in the protection scope of the present invention.

Claims

1. A fatigue performance evaluation method for steel-UHPC composite bridge deck, characterized in that: The steps include: Step 1: Based on the structural parameters and material properties of the reinforced UHPC layer, the fatigue performance of the reinforced UHPC component under axial tensile fatigue load is evaluated. Through the axial tensile static test of the reinforced UHPC component, the internal force distribution characteristics of the steel bars and UHPC during the tensile cracking of the reinforced UHPC component, as well as the crack spacing and crack width of the reinforced UHPC component are determined; through the axial tensile fatigue test of the reinforced UHPC component, the internal force transfer law of the steel bars and UHPC materials and the crack development law of the reinforced UHPC component under fatigue load are determined; Step 2: Fatigue performance analysis of a bolt connector with a diameter of 16 mm in ultra-thin UHPC under shear fatigue load is performed through a static performance test to obtain the evolution of the first mechanical performance index of the bolt connector with the number of loading actions; the first mechanical performance index is the regular shear stiffness and residual slip; Step 3, analyzing the bending fatigue performance of the steel-UHPC-paving composite slab by a five-point bending test; Step 4: Establish a time-varying fatigue analysis framework for steel-UHPC composite bridge decks with degraded steel-concrete composite effect and verify it based on full-scale model fatigue test data; Step 5: Based on Steps 3 and 4, an integrated design of the steel-UHPC composite bridge deck and bridge pavement is performed.

2. A fatigue performance evaluation method for steel-UHPC composite bridge deck according to claim 1, characterized in that: In step 1, the fatigue performance of reinforced UHPC components under axial tensile fatigue load is evaluated according to the structural parameters and material properties of the reinforced UHPC layer. Specifically, the surface crack width evolution model of UHPC components is constructed, and the control crack width threshold of the surface crack width of the reinforced UHPC components reaching the durability design requirements of the UHPC material and the fracture failure of the reinforced UHPC components are used as fatigue failure criteria. The formula of the surface crack width evolution model of UHPC components is: In c，f =in c,0 +k log(N)=β S c ·ε S +k log(N); Where: w c，f is the crack width on the surface of the UHPC component, β is the adjustment coefficient of the crack width on the surface of the UHPC component, S c is the surface crack spacing of UHPC components, ε s is the steel bar strain, k is the crack width growth coefficient, and N is the number of fatigue cycles; Extract the crack width on the surface of the UHPC component, and compare the crack width on the surface of the UHPC component with the control crack width threshold required by the durability design of the UHPC material. If the crack width on the surface 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 crack width on the surface of the UHPC component is less than the controlled 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 fails by fracture, the fatigue performance of the UHPC component is unqualified.

3. A fatigue performance evaluation method for steel-UHPC composite bridge deck according to claim 1, characterized in that: In step 1, the axial tension static test of reinforced UHPC components includes axial tension tests of reinforced UHPC components with two typical reinforcement ratios, each type of test includes three specimens, and a total of six specimens; the axial tension fatigue test of reinforced UHPC components includes axial tension tests of reinforced UHPC components with two typical reinforcement ratios, each type of test includes four specimens, and a total of eight specimens.

4. A fatigue performance evaluation method for steel-UHPC composite bridge deck according to claim 1, characterized in that: In step 2, the static performance test of the stud connector in the ultra-thin UHPC includes a static push-out test of studs with a diameter of 16 mm in the ultra-thin UHPC, including 3 specimens, a total of 3 specimens; the fatigue performance test of the stud connector in the ultra-thin UHPC includes a fatigue push-out test of studs with a diameter of 16 mm in the ultra-thin UHPC, each type of test includes 5 specimens, a total of 5 specimens.

5. A fatigue performance evaluation method for steel-UHPC composite bridge deck according to claim 1, characterized in that: In step 3, the five-point bending test of the steel-UHPC-paving composite slab includes two types of composite bridge deck tests with different structural parameters. Each type of test uses three load amplitudes, with a total of 6 specimens. By carrying out the five-point bending fatigue test of the steel-UHPC-paving composite slab, it is verified whether the interlayer shear performance of the pavement layer in the steel-UHPC bridge deck meets the requirements and confirms the reasonable thickness of the pavement layer; the three-point positive and negative bending test of the steel-paving composite slab, each type of test considers three load amplitudes, with a total of 6 specimens. By carrying out the three-point positive and negative bending test of the steel-paving composite slab, the longitudinal tensile performance of the pavement layer is determined, and the deflection limit of the steel-paving layer composite slab is determined.

6. A fatigue performance evaluation method for steel-UHPC composite bridge deck according to claim 1, characterized in that: In step 4, a time-varying fatigue analysis framework for steel-UHPC composite bridge decks with degraded steel-concrete composite effect is established, and verified based on the fatigue test data of the full-scale model. Specifically, the time-varying fatigue analysis framework for steel-UHPC composite bridge decks is established, and the mechanical property degradation model of reinforced UHPC components and studs is considered in the finite element method to establish a time-varying fatigue analysis framework for steel-UHPC composite bridge decks with degraded steel-concrete composite effect; a theoretical method for structural response calculation applicable to steel-UHPC composite bridge decks and bridge deck pavement is derived; The calculation formulas for the section characteristic indexes of the longitudinal and transverse standard sections at the control parts of the key load-bearing components are derived, the calculation formulas for the bending moment and shear force at both ends of the control parts of the key load-bearing components are determined, and a load-slip deformation coordination mechanics model is established.

7. A fatigue performance evaluation method for steel-UHPC composite bridge deck according to claim 1, characterized in that: In step 5, an integrated design of the steel-UHPC composite bridge deck and the bridge pavement is performed based on steps 3 and 4. Specifically, through a full-scale model fatigue test of the steel-UHPC composite bridge deck, the longitudinal and transverse fatigue performances are clarified, and the control positions of the key load-bearing components that control the fatigue performance of the structure by the longitudinal and transverse fatigue performances are determined.

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