Method and system for comprehensively analyzing fatigue of steel-UHPC (Ultra High Performance Concrete) combined bridge deck slab

Abstract

The invention discloses a comprehensive fatigue analysis method and system for a steel-UHPC combined bridge deck, and the method comprises the steps: constructing a finite element model, and carrying out the calculation; periodic stress is obtained, and a cracking part is obtained; performing a fatigue test according to the periodic stress and the cracking part to obtain an attenuation coefficient of an elastic modulus of the crack of the UHPC structure in a water immersion state; the periodic load is applied to the finite element model again for calculation, and the elastic modulus of the unit of the cracking part is attenuated according to the attenuation proportion after the preset round of loading is achieved every time; and performing fatigue analysis according to the stress data. According to the method, the influence of the crack water content of the UHPC structure on the overall stress state of the combined bridge deck slab can be analyzed, fatigue analysis of the combined bridge deck slab is achieved, then a solid foundation is laid for fatigue analysis of the steel-UHPC combined bridge deck slab in a complex environment, and the service safety of the steel-UHPC combined bridge deck slab is improved.

Description

Technical Field

[0001] This invention relates to the field of intelligent analysis technology, specifically to a comprehensive fatigue analysis method and system for steel-UHPC composite bridge decks. Background Technology

[0002] In engineering practice, steel-UHPC composite bridge decks are not only subjected to reciprocating wheel loads but are also susceptible to the effects of the service environment. Various adverse factors exist in the service environment, directly impacting the UHPC structural layer and accelerating the accumulation of fatigue damage. This further exacerbates the damage evolution of the structural system. Key adverse factors include rain-induced immersion, a common service scenario for bridge deck structures. Rainwater easily seeps into cracks in the UHPC structural layer under vehicle loads, leading to a coupling effect of the immersion environment and fatigue loads. In this situation, water-filled cracks open and close rapidly, preventing the timely removal of free water and causing a sharp increase in internal water pressure, thus accelerating the fatigue damage process of the UHPC structural layer. Simultaneously, the intensified fatigue damage to the UHPC structural layer alters the stress response of the entire composite bridge deck, affecting the stress state of the superstructure steel beams and intermediate connectors. Currently, no solutions exist for analyzing this condition. This application, based on the National Natural Science Foundation of China (52408217) project of Professor Cheng Zhenyu, investigates the above-mentioned content regarding the time-dependent degradation mechanism and remaining life prediction method of fatigue performance of steel-UHPC composite bridge deck. Summary of the Invention

[0003] In order to at least overcome the above-mentioned deficiencies in the prior art, the purpose of this application is to provide a comprehensive fatigue analysis method and system for steel-UHPC composite bridge decks.

[0004] In a first aspect, embodiments of this application provide a comprehensive fatigue analysis method for steel-UHPC composite bridge decks, including: Construct a finite element model of at least one span of the target steel-UHPC composite bridge deck, and perform calculations by applying periodic loads to the bridge deck; Obtain the periodic stress at the top of the UHPC structure in the finite element model described in the calculation results, and identify the cracked locations of the UHPC structure; the cracked locations are those where the stress exceeds a preset value. Based on the periodic stress and the crack location, a fatigue test was conducted on the UHPC structure to obtain the attenuation coefficient of the elastic modulus of the UHPC structure under water immersion. The attenuation coefficient is the attenuation ratio of the elastic modulus at the crack of the UHPC structure under a preset number of cycles of periodic stress loading. The finite element model is recalculated by applying periodic loads, and the elastic modulus of the elements at the cracked part is reduced according to the attenuation ratio after each preset loading cycle. Obtain stress data for each part in the calculation results, and perform fatigue analysis on the upper steel beam, connectors and the UHPC structure based on the stress data.

[0005] In one possible implementation, obtaining the attenuation coefficient includes: A similar model of the UHPC structure of the target steel-UHPC composite bridge deck is constructed as a sample UHPC component, and crack strain gauges are installed at the corresponding crack locations of the sample UHPC component; the reinforcement and strength of the sample UHPC component are the same as those of the UHPC structure. The initial elastic modulus corresponding to the cracked portion was obtained by applying static loading to the sample UHPC component. A pre-fabricated notch is made on the surface of the corresponding cracked part of the sample UHPC component, and a ring of water-containing rubber tube is laid at the pre-fabricated notch before the sample UHPC component is loaded by the periodic stress. Each time the preset number of loading cycles is reached, the sample UHPC component is subjected to static loading to obtain the current elastic modulus corresponding to the cracked part, and the ratio of the current elastic modulus to the initial elastic modulus is calculated as the attenuation coefficient corresponding to the number of loading cycles.

[0006] In one possible implementation, the calculation of the elastic modulus includes: Under static loading, the ratio of the loading stress to the strain obtained by the crack strain gauge is used as the elastic modulus of the corresponding cracked part.

[0007] In one possible implementation, attenuating the elastic modulus of the element at the cracked portion according to the attenuation ratio includes: Each time the preset number of loading cycles is reached, the number of preset number of loading cycles is obtained, and the decay coefficient corresponding to the number of loading cycles is obtained; The attenuation is achieved by multiplying the attenuation coefficient by the original elastic modulus of the element at the cracked part of the finite element model, which is then used as the elastic modulus of the element in the current state.

[0008] In one possible implementation, fatigue analysis of the upper steel beam, connectors, and UHPC structure based on the stress data includes: The stress time history curves of each key component of the upper steel beam, connectors and UHPC structure were obtained, and the number of cycles at different stress levels of each key component was obtained by rainflow counting method. The fatigue damage of the critical parts is calculated based on the number of cycles and the corresponding SN curve.

[0009] Secondly, embodiments of this application also provide a comprehensive fatigue analysis system for steel-UHPC composite bridge decks, comprising: The modeling unit is configured to construct a finite element model of at least one span of the target steel-UHPC composite bridge deck and perform calculations under periodic loads applied to the bridge deck. The acquisition unit is configured to acquire the periodic stress at the top of the UHPC structure in the finite element model of the calculation results, and to acquire the cracked part of the UHPC structure; the cracked part is the part where the stress exceeds a preset value. The experimental unit is configured to conduct fatigue tests on the UHPC structure based on the periodic stress and the crack location, and obtain the attenuation coefficient of the elastic modulus of the UHPC structure under water immersion; the attenuation coefficient is the attenuation ratio of the elastic modulus at the crack of the UHPC structure under a preset number of cycles of periodic stress loading. The calculation unit is configured to recalculate by applying periodic loads to the finite element model, and to reduce the elastic modulus of the element at the cracked part according to the attenuation ratio after each preset loading cycle. The analysis unit is configured to acquire stress data for each part in the calculation results and perform fatigue analysis on the upper steel beam, connectors and the UHPC structure based on the stress data.

[0010] In one possible implementation, the experimental unit is further configured as follows: A similar model of the UHPC structure of the target steel-UHPC composite bridge deck is constructed as a sample UHPC component, and crack strain gauges are installed at the corresponding crack locations of the sample UHPC component; the reinforcement and strength of the sample UHPC component are the same as those of the UHPC structure. The initial elastic modulus corresponding to the cracked portion was obtained by applying static loading to the sample UHPC component. A pre-fabricated notch is made on the surface of the corresponding cracked part of the sample UHPC component, and a ring of water-containing rubber tube is laid at the pre-fabricated notch before the sample UHPC component is loaded by the periodic stress. Each time the preset number of loading cycles is reached, the sample UHPC component is subjected to static loading to obtain the current elastic modulus corresponding to the cracked part, and the ratio of the current elastic modulus to the initial elastic modulus is calculated as the attenuation coefficient corresponding to the number of loading cycles.

[0011] In one possible implementation, the experimental unit is further configured as follows: Under static loading, the ratio of the loading stress to the strain obtained by the crack strain gauge is used as the elastic modulus of the corresponding cracked part.

[0012] In one possible implementation, the computing unit is further configured as follows: Each time the preset number of loading cycles is reached, the number of preset number of loading cycles is obtained, and the decay coefficient corresponding to the number of loading cycles is obtained; The attenuation is achieved by multiplying the attenuation coefficient by the original elastic modulus of the element at the cracked part of the finite element model, which is then used as the elastic modulus of the element in the current state.

[0013] In one possible implementation, the analysis unit is further configured as follows: The stress time history curves of each key component of the upper steel beam, connectors and UHPC structure were obtained, and the number of cycles at different stress levels of each key component was obtained by rainflow counting method. The fatigue damage of the critical parts is calculated based on the number of cycles and the corresponding SN curve.

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects: This invention provides a comprehensive fatigue analysis method and system for steel-UHPC composite bridge decks. It can analyze the influence of water content in cracks in the UHPC structure on the overall stress state of the composite bridge deck, realize fatigue analysis of the composite bridge deck, and thus lay a solid foundation for fatigue analysis of steel-UHPC composite bridge decks in complex environments, thereby improving the service safety of steel-UHPC composite bridge decks. Attached Figure Description

[0015] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the method steps in an embodiment of this application; Figure 2 This is a schematic diagram of the finite element model of an embodiment of this application; Figure 3 This is a detailed schematic diagram of the finite element model of an embodiment of this application; Figure 4 This is a schematic diagram of the experimental model in an embodiment of this application. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the accompanying drawings in this application are for illustrative and descriptive purposes only and are not intended to limit the scope of protection of this application. Furthermore, it should be understood that the schematic drawings are not drawn to scale. The flowcharts used in this application illustrate operations implemented according to some embodiments of this application. It should be understood that the operations in the flowcharts may not be implemented in sequence, and steps without logical contextual relationships may be reversed or implemented simultaneously. In addition, those skilled in the art, guided by the content of this application, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts.

[0017] Furthermore, the described embodiments are merely some, not all, of the embodiments of this application. The components of the embodiments of this application described and illustrated herein can typically be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0018] Please refer to the following: Figure 1 The above is a flowchart illustrating a comprehensive fatigue analysis method for steel-UHPC composite bridge decks provided in an embodiment of the present invention. Further, the comprehensive fatigue analysis method for steel-UHPC composite bridge decks may specifically include the contents described in steps S1-S5.

[0019] S1: Construct a finite element model of at least one span of the target steel-UHPC composite bridge deck and perform calculations by applying periodic loads to the bridge deck; S2: Obtain the periodic stress at the top of the UHPC structure in the finite element model in the calculation results, and obtain the cracked part of the UHPC structure; the cracked part is the part where the stress exceeds the preset value; S3: Conduct fatigue tests on the UHPC structure based on the periodic stress and the crack location to obtain the attenuation coefficient of the elastic modulus of the UHPC structure under immersion conditions; the attenuation coefficient is the attenuation ratio of the elastic modulus at the crack of the UHPC structure under a preset number of cycles of periodic stress loading. S4: Recalculate by applying periodic loads to the finite element model, and reduce the elastic modulus of the elements at the cracked part according to the attenuation ratio after each preset loading cycle. S5: Obtain stress data for each part in the calculation results, and perform fatigue analysis on the upper steel beam, connectors and the UHPC structure based on the stress data.

[0020] When implementing the embodiments of this application, it is necessary to first construct a finite element model of the target steel-UHPC composite bridge deck. Please refer to [link / reference] for the constructed finite element model. Figure 2 and Figure 3 At this point, it is necessary to construct the periodic load on the bridge deck to represent vehicle travel based on specifications or relevant data, i.e., the longitudinal wheel load at the top of the bridge in the figure; the periodic load represents the load above the bridge deck, and is generally represented in a periodic manner. Each time a finite element calculation is performed, dynamic response calculation can be performed by continuously applying multiple periods of load. After loading calculation on the finite element model, relevant parameters of the corresponding elements of the UHPC structure can be obtained, such as stress data. As a concrete structure, UHPC generally requires tensile stress to exceed a certain level to crack. Therefore, based on the stress data of the elements, it can be determined which parts are more prone to cracking, i.e., the parts where tensile stress exceeds the preset value; the impact on these parts is calibrated in this embodiment of the application through fatigue testing.

[0021] In this embodiment, to facilitate fatigue testing, it is necessary to first obtain the periodic stress at the top of the UHPC structure. It should be understood that the periodic distribution of the periodic stress and the periodic load should be the same or similar, and can be presented in the form of a load spectrum. For the fatigue test specimen, a concrete specimen similar to the UHPC portion under the actual target steel-UHPC composite bridge deck needs to be constructed for tensile and compressive tests. The tensile and compressive load uses the aforementioned periodic stress to better simulate the actual situation. Simultaneously, water immersion simulation needs to be performed at the cracked areas of the specimen to obtain the change in the elastic modulus of the cracked area under the condition of water filling the crack.

[0022] In this embodiment, the attenuation coefficient obtained from experiments can be fed back into the aforementioned finite element model for further finite element simulation. In this calculation, the changes in the overall stress on the bridge under water immersion conditions can be simulated by adjusting the element parameters of the cracked area, thus more closely reflecting the actual situation and effectively improving the accuracy of the calculation. Under multiple rounds of cyclic loading calculations, the elastic modulus of the cracked area gradually decreases, causing changes in the overall stress on the bridge, which in turn affects the stress on the connecting parts and the superstructure. The stress data of these simulated parts can better characterize the actual fatigue damage when used for fatigue analysis.

[0023] In one possible implementation, obtaining the attenuation coefficient includes: A similar model of the UHPC structure of the target steel-UHPC composite bridge deck is constructed as a sample UHPC component, and crack strain gauges are installed at the corresponding crack locations of the sample UHPC component; the reinforcement and strength of the sample UHPC component are the same as those of the UHPC structure. The initial elastic modulus corresponding to the cracked portion was obtained by applying static loading to the sample UHPC component. A pre-fabricated notch is made on the surface of the corresponding cracked part of the sample UHPC component, and a ring of water-containing rubber tube is laid at the pre-fabricated notch before the sample UHPC component is loaded by the periodic stress. Each time the preset number of loading cycles is reached, the sample UHPC component is subjected to static loading to obtain the current elastic modulus corresponding to the cracked part, and the ratio of the current elastic modulus to the initial elastic modulus is calculated as the attenuation coefficient corresponding to the number of loading cycles.

[0024] When implementing the embodiments of this application, please refer to Figure 4 The diagram illustrates the specific conditions of the model test. It shows that the sample UHPC component is a vertical concrete structure used to characterize a portion of the UHPC structure. Strain gauges spanning the cracked area are used to detect strain changes at the crack. The reinforcement and concrete strength of this sample UHPC component need to be consistent with the actual UHPC structure to improve the accuracy of the test. To calibrate the attenuation coefficient, the elastic modulus of the cracked area in the initial state needs to be determined first. This can be obtained through static loading, where the initial elastic modulus can be calculated based on the stress under static loading and the strain detected by the crack strain gauges.

[0025] In the implementation of this application embodiment, to simulate the generation and development of cracks, a prefabricated notch is made on the surface at the crack location. Simultaneously, a ring of water-containing rubber tubing is installed at the prefabricated notch to simulate water immersion. The water-containing rubber tubing also seals the water within the crack generated by the prefabricated notch. At this time, the periodic stress obtained above is used to apply tensile and compressive loading to the end of the sample UHPC structure. During the tensile and compressive loading process, due to the stress concentration effect at the prefabricated notch, cracks will be generated along the transverse direction of the component. This type of crack development is completely consistent with actual crack development. Therefore, during the loading process, the generation and propagation of cracks are also completely consistent with actual cracks, thus achieving a simulation test of water immersion in cracks.

[0026] In this embodiment, since fatigue testing requires many loading cycles, a preset number of cycles is set to characterize the end of one cycle, typically around 200 cycles for a complete cycle. The attenuation coefficient characterizes the decrease in the elastic modulus of the cracked area after each cycle, primarily reflecting crack development. Therefore, after each preset cycle, static loading is performed again to obtain the current elastic modulus, calculated in the same way as the initial elastic modulus. Based on the current and initial elastic modulus, the attenuation coefficient can be calculated. It should be understood that the attenuation coefficient corresponds to the number of preset cycles; as the number of cycles increases, the attenuation coefficient changes, generally decreasing gradually.

[0027] In one possible implementation, the calculation of the elastic modulus includes: Under static loading, the ratio of the loading stress to the strain obtained by the crack strain gauge is used as the elastic modulus of the corresponding cracked part.

[0028] In one possible implementation, attenuating the elastic modulus of the element at the cracked portion according to the attenuation ratio includes: Each time the preset number of loading cycles is reached, the number of preset number of loading cycles is obtained, and the decay coefficient corresponding to the number of loading cycles is obtained; The attenuation is achieved by multiplying the attenuation coefficient by the original elastic modulus of the element at the cracked part of the finite element model, which is then used as the elastic modulus of the element in the current state.

[0029] In the implementation of this application embodiment, when attenuating the elastic modulus of the element at the cracked part by attenuation ratio, it is necessary to obtain the number of preset loading cycles, and look up the corresponding attenuation coefficient based on the number of cycles. Then, attenuation can be achieved by multiplying the initial original elastic modulus of the element at the cracked part. This can be achieved by multiplying the stiffness matrix of the cracked part. This application embodiment does not impose any limitations.

[0030] In one possible implementation, fatigue analysis of the upper steel beam, connectors, and UHPC structure based on the stress data includes: The stress time history curves of each key component of the upper steel beam, connectors and UHPC structure were obtained, and the number of cycles at different stress levels of each key component was obtained by rainflow counting method. The fatigue damage of the critical parts is calculated based on the number of cycles and the corresponding SN curve.

[0031] In the implementation of this application embodiment, fatigue analysis of different components is an existing technology when the stress data changes are known. This application embodiment preferably uses the rainflow counting method to count the number of cycles passing through the stress level, and then compares the corresponding SN curves to perform fatigue damage analysis. For different parts, the appropriate SN curve needs to be selected according to the material used.

[0032] Based on the same inventive concept, this application also provides a comprehensive fatigue analysis system for steel-UHPC composite bridge decks, comprising: The modeling unit is configured to construct a finite element model of at least one span of the target steel-UHPC composite bridge deck and perform calculations under periodic loads applied to the bridge deck. The acquisition unit is configured to acquire the periodic stress at the top of the UHPC structure in the finite element model of the calculation results, and to acquire the cracked part of the UHPC structure; the cracked part is the part where the stress exceeds a preset value. The experimental unit is configured to conduct fatigue tests on the UHPC structure based on the periodic stress and the crack location, and obtain the attenuation coefficient of the elastic modulus of the UHPC structure under water immersion; the attenuation coefficient is the attenuation ratio of the elastic modulus at the crack of the UHPC structure under a preset number of cycles of periodic stress loading. The calculation unit is configured to recalculate by applying periodic loads to the finite element model, and to reduce the elastic modulus of the element at the cracked part according to the attenuation ratio after each preset loading cycle. The analysis unit is configured to acquire stress data for each part in the calculation results and perform fatigue analysis on the upper steel beam, connectors and the UHPC structure based on the stress data.

[0033] In one possible implementation, the experimental unit is further configured as follows: A similar model of the UHPC structure of the target steel-UHPC composite bridge deck is constructed as a sample UHPC component, and crack strain gauges are installed at the corresponding crack locations of the sample UHPC component; the reinforcement and strength of the sample UHPC component are the same as those of the UHPC structure. The initial elastic modulus corresponding to the cracked portion was obtained by applying static loading to the sample UHPC component. A pre-fabricated notch is made on the surface of the corresponding cracked part of the sample UHPC component, and a ring of water-containing rubber tube is laid at the pre-fabricated notch before the sample UHPC component is loaded by the periodic stress. Each time the preset number of loading cycles is reached, the sample UHPC component is subjected to static loading to obtain the current elastic modulus corresponding to the cracked part, and the ratio of the current elastic modulus to the initial elastic modulus is calculated as the attenuation coefficient corresponding to the number of loading cycles.

[0034] In one possible implementation, the experimental unit is further configured as follows: Under static loading, the ratio of the loading stress to the strain obtained by the crack strain gauge is used as the elastic modulus of the corresponding cracked part.

[0035] In one possible implementation, the computing unit is further configured as follows: Each time the preset number of loading cycles is reached, the number of preset number of loading cycles is obtained, and the decay coefficient corresponding to the number of loading cycles is obtained; The attenuation is achieved by multiplying the attenuation coefficient by the original elastic modulus of the element at the cracked part of the finite element model, which is then used as the elastic modulus of the element in the current state.

[0036] In one possible implementation, the analysis unit is further configured as follows: The stress time history curves of each key component of the upper steel beam, connectors and UHPC structure were obtained, and the number of cycles at different stress levels of each key component was obtained by rainflow counting method. The fatigue damage of the critical parts is calculated based on the number of cycles and the corresponding SN curve.

[0037] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0038] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices or units, or may be electrical, mechanical or other forms of connection.

[0039] The units described as separate components may or may not be physically separate. As will be apparent to those skilled in the art, the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0040] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0041] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or grid device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0042] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A comprehensive fatigue analysis method for steel-UHPC composite bridge decks, characterized in that, include: Construct a finite element model of at least one span of the target steel-UHPC composite bridge deck, and perform calculations by applying periodic loads to the bridge deck; Obtain the periodic stress at the top of the UHPC structure in the finite element model described in the calculation results, and obtain the crack location of the UHPC structure; The cracked area is the part where the stress exceeds a preset value; Based on the periodic stress and the crack location, a fatigue test was conducted on the UHPC structure to obtain the attenuation coefficient of the elastic modulus of the UHPC structure under water immersion. The attenuation coefficient is the attenuation ratio of the elastic modulus at the crack in the UHPC structure under a preset number of cyclic stress loading cycles. The finite element model is recalculated by applying periodic loads, and the elastic modulus of the elements at the cracked part is reduced according to the attenuation ratio after each preset loading cycle. Obtain stress data for each part in the calculation results, and perform fatigue analysis on the upper steel beam, connectors and the UHPC structure based on the stress data.

2. The fatigue comprehensive analysis method for steel-UHPC composite bridge deck according to claim 1, characterized in that, The attenuation coefficient is obtained by: A similar model of the UHPC structure of the target steel-UHPC composite bridge deck is constructed as a sample UHPC component, and crack strain gauges are installed at the corresponding crack locations of the sample UHPC component; the reinforcement and strength of the sample UHPC component are the same as those of the UHPC structure. The initial elastic modulus corresponding to the cracked portion was obtained by applying static loading to the sample UHPC component. A pre-fabricated notch is made on the surface of the corresponding cracked part of the sample UHPC component, and a ring of water-containing rubber tube is laid at the pre-fabricated notch before the sample UHPC component is loaded by the periodic stress. Each time the preset number of loading cycles is reached, the sample UHPC component is subjected to static loading to obtain the current elastic modulus corresponding to the cracked part, and the ratio of the current elastic modulus to the initial elastic modulus is calculated as the attenuation coefficient corresponding to the number of loading cycles.

3. The fatigue comprehensive analysis method for steel-UHPC composite bridge deck according to claim 2, characterized in that, The calculation of the elastic modulus includes: Under static loading, the ratio of the loading stress to the strain obtained by the crack strain gauge is used as the elastic modulus of the corresponding cracked part.

4. The fatigue comprehensive analysis method for steel-UHPC composite bridge deck according to claim 2, characterized in that, The reduction of the elastic modulus of the unit at the cracked portion according to the reduction ratio includes: Each time the preset number of loading cycles is reached, the number of preset number of loading cycles is obtained, and the decay coefficient corresponding to the number of loading cycles is obtained; The attenuation is achieved by multiplying the attenuation coefficient by the original elastic modulus of the element at the cracked part of the finite element model, which is then used as the elastic modulus of the element in the current state.

5. The fatigue comprehensive analysis method for steel-UHPC composite bridge deck according to claim 1, characterized in that, Fatigue analysis of the upper steel beam, connectors, and UHPC structure based on the stress data includes: The stress time history curves of each key component of the upper steel beam, connectors and UHPC structure were obtained, and the number of cycles at different stress levels of each key component was obtained by rainflow counting method. The fatigue damage of the critical parts is calculated based on the number of cycles and the corresponding SN curve.

6. A comprehensive fatigue analysis system for steel-UHPC composite bridge decks, characterized in that, include: The modeling unit is configured to construct a finite element model of at least one span of the target steel-UHPC composite bridge deck and perform calculations under periodic loads applied to the bridge deck. The acquisition unit is configured to acquire the periodic stress at the top of the UHPC structure in the finite element model described in the calculation results, and to acquire the crack location of the UHPC structure. The cracked area is the part where the stress exceeds a preset value; The experimental unit is configured to conduct fatigue tests on the UHPC structure based on the periodic stress and the crack location, and to obtain the attenuation coefficient of the elastic modulus of the UHPC structure under water immersion conditions. The attenuation coefficient is the attenuation ratio of the elastic modulus at the crack in the UHPC structure under a preset number of cyclic stress loading cycles. The calculation unit is configured to recalculate by applying periodic loads to the finite element model, and to reduce the elastic modulus of the element at the cracked part according to the attenuation ratio after each preset loading cycle. The analysis unit is configured to acquire stress data for each part in the calculation results and perform fatigue analysis on the upper steel beam, connectors and the UHPC structure based on the stress data.

7. The fatigue comprehensive analysis system for steel-UHPC composite bridge decks according to claim 6, characterized in that, The experimental unit is also configured as follows: A similar model of the UHPC structure of the target steel-UHPC composite bridge deck is constructed as a sample UHPC component, and crack strain gauges are installed at the corresponding crack locations of the sample UHPC component; the reinforcement and strength of the sample UHPC component are the same as those of the UHPC structure. The initial elastic modulus corresponding to the cracked portion was obtained by applying static loading to the sample UHPC component. A pre-fabricated notch is made on the surface of the corresponding cracked part of the sample UHPC component, and a ring of water-containing rubber tube is laid at the pre-fabricated notch before the sample UHPC component is loaded by the periodic stress. Each time the preset number of loading cycles is reached, the sample UHPC component is subjected to static loading to obtain the current elastic modulus corresponding to the cracked part, and the ratio of the current elastic modulus to the initial elastic modulus is calculated as the attenuation coefficient corresponding to the number of loading cycles.

8. The fatigue comprehensive analysis system for steel-UHPC composite bridge decks according to claim 7, characterized in that, The experimental unit is also configured as follows: Under static loading, the ratio of the loading stress to the strain obtained by the crack strain gauge is used as the elastic modulus of the corresponding cracked part.

9. The fatigue comprehensive analysis system for steel-UHPC composite bridge decks according to claim 7, characterized in that, The computing unit is further configured to: Each time the preset number of loading cycles is reached, the number of preset number of loading cycles is obtained, and the decay coefficient corresponding to the number of loading cycles is obtained; The attenuation is achieved by multiplying the attenuation coefficient by the original elastic modulus of the element at the cracked part of the finite element model, which is then used as the elastic modulus of the element in the current state.

10. The fatigue comprehensive analysis method for steel-UHPC composite bridge deck according to claim 6, characterized in that, The analysis unit is also configured to: The stress time history curves of each key component of the upper steel beam, connectors and UHPC structure were obtained, and the number of cycles at different stress levels of each key component was obtained by rainflow counting method. The fatigue damage of the critical parts is calculated based on the number of cycles and the corresponding SN curve.

Images