Highway bridge structure anti-seismic performance design method

Abstract

The invention discloses a highway bridge structure anti-seismic performance design method, which relates to the field of bridge seismic resistance, and sequentially comprises the following steps of: firstly, obtaining target bridge basic information such as bridge pier height, structure type and the like, and then carrying out anti-seismic performance analysis so as to determine fortification category and seismic level; then selecting an adaptive anti-seismic performance target from a preset table, analyzing the irregularity degree of a bridge to determine a site and earthquake related parameters, calculating and analyzing bridge structures and steel-concrete composite beams with different performance levels according to the selected target, finding out weak and key parts, and verifying and adjusting the weak and key parts. According to the method, a scientific, systematic and quantitative design system is constructed, traditional design limitation is broken through, the problem that'medium earthquake repairable 'lacks quantitative indexes is effectively solved, multiple factors are comprehensively integrated, through scientific demonstration, target selection, strict design verification and rationality and reliability guarantee, a complete, efficient and brand-new technical scheme is created for highway bridge aseismic design, and the method is worthy of popularization and application. And the safety performance of the bridge in an earthquake is powerfully guaranteed.

Description

Technical Field

[0001] The invention relates to the field of bridge seismic resistance, and in particular to a seismic performance-based design method for a highway bridge structure. Background Art

[0002] In the construction of highway transportation infrastructure, bridges are key links, and their seismic performance is directly related to the safety and smoothness of transportation. With the continuous development of the economy and society, the construction scale of highway bridges has continued to expand, and their safety under earthquake disasters has received more and more attention.

[0003] Traditional seismic design of highway bridges mainly follows the three-level, two-stage design method adopted by the current "Highway Bridge Seismic Design Code" (JTG / T2231-01-2020). Among them, the three levels are "no damage in small earthquakes, repairable in medium earthquakes, and no collapse in large earthquakes", and the two stages are elastic bearing capacity verification under the action of "small earthquakes" and elastic-plastic deformation verification under the action of "large earthquakes". Under this design framework, the performance goals of "no damage in small earthquakes" and "no collapse in large earthquakes" have relatively clear quantitative parameters, which makes it easier to operate and control in actual design. However, for the key performance goal of "repairable in medium earthquakes", the code only gives a qualitative description, and in design practice it mostly relies on structural measures to achieve it.

[0004] This traditional design method has certain limitations. From the perspective of performance balance, it generally adopts a single solution of "low elastic bearing capacity-high ductility". In actual earthquakes, factors such as earthquake characteristics in different regions, functional requirements of bridges, and structural forms are complex and diverse, and a single design strategy is difficult to fully adapt. For example, in some areas where earthquakes are frequent and seismic motion characteristics are complex, relying solely on high ductility design may not be able to effectively guarantee the overall performance of bridges under moderate and large earthquakes; and in some transportation hubs that have extremely high requirements for the continuity of bridge functions, low elastic bearing capacity design may result in a long maintenance cycle for the bridge after a moderate earthquake, even though it has not collapsed, which seriously affects transportation efficiency.

[0005] In addition, with the continuous development of bridge construction technology, new materials and complex structural forms (such as large-span steel-concrete composite structure bridges, special-shaped arch bridges, etc.) continue to emerge, and traditional design methods are increasingly unable to cope with these new situations. For these new bridge structures, how to accurately evaluate their seismic performance under different earthquake levels and achieve a reasonable match between bearing capacity and ductility has become an urgent problem to be solved. At the same time, in urban bridge construction, due to factors such as complex surrounding environment and limited space, higher requirements are placed on the repairability and rapid functional recovery ability of bridges after earthquakes. Traditional design methods are obviously insufficient in meeting these special needs. Summary of the invention

[0006] The purpose of the present invention is to provide a seismic performance-based design method for highway bridge structures. The method establishes a scientific, systematic and quantitatively indexed seismic performance-based design method for highway bridge structures, accurately achieves different seismic performance targets such as "repairable in moderate earthquakes", and in the design process, comprehensively considers various factors such as pier height, structural regularity, site type, seismic fortification standards, etc., and then selects appropriate seismic performance targets through scientific analysis and demonstration, and ensures the rationality and reliability of the design through strict design verification and adjustment, thereby providing a complete and effective technical means for the seismic design of highway bridges.

[0007] The present invention is achieved through the following technical solutions: A seismic performance-based design method for a highway bridge structure is provided, wherein the design method is performed in the following steps: Step 1: Obtain basic information of the target bridge, including pier height, structure type, site type, and seismic fortification standards; Step 2: Perform seismic performance analysis on the target bridge based on the information obtained in step 1 to obtain the seismic fortification category and earthquake level of the target bridge; Step 3: According to the seismic fortification category and earthquake level of the target bridge, select the corresponding seismic performance target from the preset seismic performance target table; Step 4: Analyze and determine the extent and condition of bridge structure irregularities exceeding those specified in the Code for Seismic Design of Highway Bridges, which is used to determine site conditions, earthquake levels, and ground motion parameters; Step 5: Based on the selected seismic performance target, calculate and analyze bridge structures with different performance levels to demonstrate that the structure can meet the seismic performance requirements, including bearing capacity design calculations for bridge structures with different performance levels and design calculations for steel-concrete composite beams. Based on the calculation results, find out the weak parts of the bridge structure and the key parts that need to be strengthened, and then verify and adjust the design of the weak parts and key parts.

[0008] In this scheme, by sequentially obtaining basic bridge information, conducting seismic performance analysis, selecting seismic performance targets, determining the degree and situation of irregularities, and performing structural calculations and analysis based on the selected targets, a seismic performance-based design method for highway bridge structures with quantitative indicators is provided for bridge seismic design. These steps can not only fully consider the characteristics, site conditions and seismic requirements of different bridges, but also accurately locate the weak and critical parts of the structure. Through design verification and adjustment, it can ensure that the bridge meets the seismic performance requirements under different earthquake levels, effectively solve the difficulties of traditional design in aspects such as "repairable in moderate earthquakes", and significantly improve the seismic reliability of the bridge.

[0009] Further optimizing the scheme, the performance level includes a first performance level, a second performance level, a third performance level, a fourth performance level and a fifth performance level; The first performance level is designed to meet the elastic design specifications of the current "Highway Bridge Seismic Design Specifications" for its bearing capacity and deformation under the E1 earthquake. Under the design earthquake, the seismic bearing capacity of the bridge structure meets the following formula: ; is the permanent action partial coefficient, is the permanent effect standard value, is the design value of the bridge structure bearing capacity, is the structural internal force of the standard value of horizontal earthquake action, is the structural internal force of the standard value of vertical earthquake action, is the partial coefficient of horizontal earthquake action, is the partial coefficient of horizontal seismic action; Under the design earthquake action or E2 earthquake action, the shear bearing capacity of the plastic energy dissipation zone and the seismic bearing capacity of key components of the second performance level meet the requirements of formula (1-1), wherein the normal section bearing capacity of the plastic energy dissipation zone meets the following formula: ; is the standard value of the bearing capacity of the bridge structure section, calculated according to the standard value of the material, and 0.4 is the combined value coefficient of the vertical seismic action; In the third performance level, under the design earthquake action or E2 earthquake action, the normal section bearing capacity of key components and ordinary components meets the requirements of formula (1-2), the normal section bearing capacity of key components of the long-span bridge structure meets the requirements of formula (1-3), and some plastic hinge areas enter the yield stage, and their shear bearing capacity meets formula (1-2), where formula (1-3) is as follows: ; 0.4 is the combined value coefficient of horizontal earthquake action; Under the design earthquake or E2 earthquake, some common components and most of the plastic hinge areas enter the yield stage. The shear section of the reinforced concrete structure should meet the requirements of formula (1-4), which is as follows: ; is the shear force of the member under gravity load, b is the width of the rectangular section or the thickness of the web of the T-shaped or I-shaped section, is the distance from the point of action of the longitudinal reinforcement force to the compression edge, It is the standard value of compressive strength of concrete cube with side length of 150mm; The shear section of the steel-concrete composite structure meets the requirements of formula (1-5), where formula (1-5) is as follows: ; b is the width of the rectangular section or the thickness of the web of the T-shaped or I-shaped section, is the distance from the point of action of the longitudinal reinforcement force to the compression edge, is the cross-sectional area of ​​the steel-concrete composite structure steel beam, is the component shear force of the standard value of earthquake action, is the standard value of steel strength; In the fifth performance level, under the action of E2 earthquake, more common components enter the yield stage, and the shear section of the common components meets the requirements of formula (1-4) or formula (1-5), allowing some plastic energy-absorbing components to be severely damaged, and the elastic-plastic displacement of the structure meets the maximum elastic-plastic displacement limit of the structure.

[0010] In this scheme, the specific design requirements of bridge structures under different earthquakes from the 1st to the 5th performance levels are defined in detail, providing accurate and operational quantitative standards for the entire seismic design. In each performance level, the calculation formulas and conditions of key indicators such as seismic bearing capacity, normal section and inclined section bearing capacity, shear section requirements, and plastic hinge area performance are clearly defined, so that designers can accurately design according to these clear criteria, ensuring that the performance of bridge structures under different earthquake levels is predictable and controllable, which strongly supports the seismic performance design goal with quantitative indicators pursued by the invention, ensures the safety and stability of bridges in earthquakes, and effectively makes up for the shortcomings of traditional design methods in refined design.

[0011] Further optimization scheme, the stress and deformation of reinforced concrete components under the second performance level under the design earthquake or E2 earthquake need to meet the following standards: When the reinforced concrete member is a bending member, the calculation of its normal section bending bearing capacity shall comply with the following formula: ; is the bending moment caused by the gravity of the structure, is the bending moment caused by the lateral earthquake action, is the bending moment caused by vertical earthquake action, x is the height of the equivalent compression zone of concrete, is the standard value of concrete axial compressive strength, b is the width of rectangular section or the thickness of web of T-shaped or I-shaped section, is the distance from the point of action of the longitudinal reinforcement force to the compression edge, is the standard value of compressive strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​the longitudinal ordinary steel bars in the compression zone, is the standard value of compressive strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​the longitudinal prestressed tendons in the compression zone, is the stress of the prestressed tendon when the normal stress of concrete at the resultant force point of the prestressed tendon in the compression zone is equal to zero, is the distance from the longitudinal ordinary steel bar in the compression zone to the edge of the compression zone, It is the distance from the longitudinal prestressed tendons in the compression zone to the edge of the compression zone.

[0012] In this scheme, a clear and critical calculation standard for the bending capacity of the positive section is given for the stress and deformation of reinforced concrete flexural members under the second performance level under the design earthquake or E2 earthquake. By introducing parameters such as structural gravity, bending moments caused by lateral and vertical earthquakes, and combining relevant regulations on the height of the equivalent compression zone of concrete, the bearing capacity requirements of the members under complex earthquake conditions are accurately quantified. This not only provides scientific and specific guidance for designers to design reinforced concrete flexural members under this performance level, ensuring that the member design meets the quantitative indicators of seismic performance-based design, but also helps to accurately evaluate the performance of the members in earthquakes and ensure the overall safety and stability of the bridge structure under the corresponding earthquake action.

[0013] To further optimize the scheme, the concrete equivalent compression zone height x is calculated by the following formula: ; x is the height of the equivalent compression zone of concrete, is the standard value of concrete axial compressive strength, is the width of a rectangular section or the thickness of a web of a T-shaped or I-shaped section, is the standard value of tensile strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​the longitudinal ordinary steel bars in the tension zone, is the standard value of tensile strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​the longitudinal prestressed tendons in the tension zone.

[0014] In this scheme, by accurately defining the mathematical relationship between the height x of the equivalent compression zone of concrete and the material properties of steel and concrete as well as the geometric parameters of the cross section of the member, a core basis is provided for accurately calculating the bearing capacity of reinforced concrete members under different stress states. In the process of seismic design, especially for the design calculation of the second performance level and other related performance levels, it can help designers accurately evaluate the bearing capacity and deformation characteristics of the member under the action of earthquake, and ensure that the designed member meets the predetermined seismic performance requirements.

[0015] Further optimization scheme, the cross-sectional compressive bearing capacity of the axially compressed member in the reinforced concrete member shall comply with the following formula: ; is the structural axial force caused by structural gravity, is the structural axial force caused by lateral earthquake action, is the structural axial force caused by vertical earthquake action, is the standard value of concrete axial compressive strength, is the gross cross-sectional area of ​​the component, is the standard value of compressive strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​all longitudinal ordinary steel bars, is the stability factor of the axially compressed member.

[0016] In this scheme, by incorporating structural gravity, axial force caused by earthquake action, steel and concrete material properties, and geometric parameters of components into the formula for calculation, designers can accurately evaluate the compressive capacity of axially compressed components under different earthquake levels based on this quantitative formula. This not only ensures the scientificity and rationality of component design, ensuring that it can effectively bear pressure and maintain structural stability during an earthquake, but also lays a solid foundation for the quantitative system of seismic performance-based design of the entire bridge structure.

[0017] Further optimization scheme, when the reinforced concrete member is a bending member, the calculation of the shear bearing capacity of its inclined section shall comply with the provisions of (2-4) to (2-7): ; ; ; ; is the standard value of the shear bearing capacity of concrete and stirrups in the inclined section, is the standard value of shear bearing capacity of ordinary bent steel bars intersecting with inclined sections, is the standard value of the shear bearing capacity of the prestressed bent steel bar intersecting the inclined section, is the shear force caused by the structural gravity, is the shear force caused by earthquake action, is the influence coefficient of the bending moment of opposite sign. When calculating the shear bearing capacity of the beam section near the edge support of the simply supported beam and the continuous beam, it is taken as 1.0. When calculating the shear bearing capacity of the beam section near the middle support of the continuous beam and the cantilever beam, it is taken as 0.9. is the prestressing factor, which is 1.0 for reinforced concrete flexural members and 1.25 for prestressed concrete flexural members. is the influence coefficient of the compression flange, which is 1.0 for rectangular sections and 1.1 for T-shaped and I-shaped sections; b is the width of the rectangular section or the thickness of the web of the T-shaped or I-shaped section, is the distance from the point of action of the longitudinal reinforcement to the compression edge, P is the reinforcement percentage of the longitudinal tensile reinforcement in the inclined section, P≤2.5, is the reinforcement ratio of stirrups in the inclined section, is the reinforcement ratio of the vertical prestressed tendons in the inclined section, is the standard value of the tensile strength of stirrups, is the standard value of tensile strength of vertical prestressed tendons, is the standard value of tensile strength of ordinary bent steel bars, is the cross-sectional area of ​​the ordinary bent steel bar in the same bending plane in the inclined section, is the angle between the tangent line of the ordinary bent steel bar and the horizontal line, is the standard value of tensile strength of prestressed bent reinforcement, is the cross-sectional area of ​​the prestressed bent reinforcement in the same bending plane in the inclined section, It is the angle between the tangent line of the prestressed bent reinforcement and the horizontal line.

[0018] In this scheme, the combined effect of concrete and stirrups in the inclined section, the contribution of ordinary bent steel bars and prestressed bent steel bars to the shear bearing capacity are comprehensively considered, and the shear capacity of each part is closely linked to the material properties, geometric parameters and shear force generated by earthquakes through precise mathematical expressions. In the seismic design of highway bridge structures, designers can accurately calculate the shear bearing capacity of the inclined section of bending members under different earthquake levels based on these formulas, so as to reasonably configure shear structures such as stirrups and bent steel bars to ensure that the components will not fail due to shear damage of the inclined section under earthquakes, effectively ensuring the overall seismic performance of the bridge structure.

[0019] Further optimizing the scheme, the steel-concrete composite beam design calculation steps include a positive moment section and a negative moment section; Among them, in the positive moment section, when the plastic neutral axis of the composite section is inside the concrete slab, if Conditions, the compressive bearing capacity of the positive section should be calculated according to the following formula: ; ; Among them, A and b e 、h c is the cross-sectional parameter of the steel-concrete composite beam, M ik 、M Ehk 、M EVK is the corresponding bending moment, and the reinforcement and size of the concrete slab and steel beam are determined based on the calculation results. is the bending moment caused by the structural gravity, is the bending moment caused by the lateral earthquake action, is the bending moment caused by vertical earthquake action, 0.4 is the combination value coefficient of vertical earthquake action, is the cross-sectional area of ​​the steel beam, x is the height of the compression zone of the concrete slab, y is the distance between the resultant force of the steel beam cross-sectional area and the resultant force of the compression zone of the concrete, is the effective width of the concrete slab, It is the standard value of concrete axial compressive strength.

[0020] In this scheme, the design and calculation methods in the positive moment section are specified in detail, especially under the common and critical working condition that the plastic neutral axis of the composite section is located in the concrete slab. By introducing the cross-sectional parameters of the steel-concrete composite beam and the bending moment generated under different loads, an accurate calculation formula for the compressive bearing capacity of the positive section is given. This enables designers to accurately calculate the required compressive capacity of the steel-concrete composite beam under the positive moment based on this formula and the specific parameters in the actual project, and then scientifically and reasonably determine the reinforcement and size of the concrete slab and steel beam. This not only ensures the positive section bearing performance of the steel-concrete composite beam under complex loads such as earthquakes, but also provides a key local structural design basis for the seismic design of the entire highway bridge structure, which helps to achieve the overall seismic performance target of the bridge.

[0021] Further optimization scheme, in the positive moment section, when the plastic neutral axis of the composite section is inside the concrete slab, if Conditions, the compressive bearing capacity of the positive section should be calculated according to the following formula: ; ; is the effective width of the concrete slab, is the concrete slab section height, is the height of the compression zone of the steel beam section, is the standard value of tensile strength of steel beam section, is the distance between the resultant force point in the tension zone of the steel beam and the resultant force point in the compression zone of the concrete, It is the distance from the resultant force point in the tension zone of the steel beam to the resultant force point in the compression zone of the steel beam.

[0022] In this solution, designers can substitute actual engineering data into calculations to accurately determine the compressive bearing capacity of the normal section that meets the seismic performance requirements under this condition. Based on this, the reinforcement and size of the concrete slab and steel beam are further determined to ensure that the steel-concrete composite beam has sufficient strength and stability in the positive moment section under earthquake action, effectively preventing structural damage caused by insufficient compressive resistance of the normal section.

[0023] To further optimize the scheme, in the negative moment section, the compressive bearing capacity of the positive section of the steel-concrete composite beam should comply with the provisions of formulas (3-5) to (3-7): ; is the plastic section moment of inertia of the steel beam section, is the standard value of steel bar tensile strength, is the distance from the plastic neutral axis of the composite beam to the steel bar resultant point, is the distance from the plastic neutral axis of the composite beam to the plastic neutral axis of the steel beam, is the cross-sectional area of ​​the steel bars in the concrete slab, is the cross-sectional area of ​​the steel beam, is the height of the compression zone of the steel beam section.

[0024] In this scheme, the mechanical properties of steel-concrete composite beams under negative bending moments are comprehensively considered, which involve key factors such as structural gravity, bending moments caused by earthquakes, and the plastic section inertia moment of the steel beam itself. Through precise mathematical relationship expressions, it provides a basis for quantitative calculations for designers. In the process of seismic design of highway bridge structures, these formulas can be used to accurately evaluate the compressive bearing capacity of steel-concrete composite beams in the negative bending moment section, so as to reasonably design the connection structure and reinforcement method between steel beams and concrete slabs, ensure the structural safety of the negative bending moment section of steel-concrete composite beams under complex load conditions such as earthquakes, and effectively prevent damage caused by insufficient compressive resistance.

[0025] To further optimize the solution, the following steps are also included in the design verification and adjustment steps: S51. Conduct seismic response analysis on the designed bridge structure through finite element analysis software. During the analysis, input seismic waves that meet site conditions and seismic fortification requirements to fully simulate the stress, deformation and damage of the bridge under different earthquake levels to verify whether the selected seismic performance target is met; S52. If during the verification process it is found that the structure has weak links or parts that do not meet the performance requirements, the design should be optimized and adjusted. After the adjustment, verification and analysis should be carried out again until the structure fully meets the seismic performance-based design requirements.

[0026] In this solution, step S51 uses finite element analysis software to perform seismic response analysis, inputs seismic waves that meet the actual site and fortification requirements, and can accurately simulate the actual state of the bridge under different earthquake levels, thereby providing a scientific and intuitive basis for judging whether the selected seismic performance target has been achieved. Step S52 optimizes and adjusts the weak or substandard parts that appear in the verification, and repeatedly verifies to form a closed-loop process. This ensures the effective connection from theoretical calculation to actual performance of bridge design, makes up for possible design defects, greatly improves the reliability and accuracy of bridge seismic design, and effectively promotes the realization of seismic performance-based design goals with quantitative indicators.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects: The present invention has established a scientific, systematic and quantitative seismic performance-based design method to accurately achieve different seismic performance goals such as "repairable in moderate earthquakes". In the design process, various factors such as pier height and structural regularity are comprehensively considered, and appropriate targets are selected through rigorous analysis. Accurate calculation and verification adjustments are used to ensure that the design is reasonable and reliable. There are detailed design and calculation criteria for bridge structures and steel-concrete composite beams with different performance levels, which overcomes the limitations of traditional single design strategies, can better adapt to complex earthquake characteristics, bridge functional requirements and new structural forms, and effectively improve the safety and stability of highway bridge structures in earthquakes. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings: Figure 1 It is a schematic diagram of the seismic performance design process of the present invention; Figure 2 It is a schematic diagram of a reinforced concrete rectangular cross-section bending member of the present invention; Figure 3 It is a simplified calculation diagram of the bending and seismic performance of the positive section of the reinforced concrete rectangular cross-section bending member of the present invention; Figure 4 A simplified diagram for calculating the shear and seismic performance of the oblique section of a reinforced concrete rectangular section bending member of the present invention; Figure 5 It is a structural schematic diagram of the plastic neutral axis in the concrete wing plate of the present invention; Figure 6 This is a simplified diagram for calculating the seismic performance of the plastic neutral axis in the concrete wing plate; Figure 7 This is a simplified diagram for calculating the seismic performance of the plastic neutral axis in the steel beam; Figure 8 It is the structural schematic diagram of the steel-concrete composite beam under the action of negative bending moment; Fig. 9 This is a simplified diagram for calculating the seismic performance of steel-concrete composite beams under negative bending moment.

[0029] Marks and corresponding parts names in the attached drawings: 1-Plastic neutral axis of composite section, 2-Plastic neutral axis of steel beam. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention. Example

[0031] Since the traditional highway bridge seismic design code only gives a qualitative description and solves it through construction, and the traditional design method only has a single solution of "low elastic bearing capacity-high ductility", this embodiment provides a scientific, systematic and quantitative index-based seismic performance design method for highway bridge structures. By pursuing the best balance between bearing capacity and ductility, a performance-based design scheme of "low elastic bearing capacity-high ductility" or "high elastic bearing capacity-low ductility" is provided to accurately achieve different seismic performance goals such as "repairable in moderate earthquakes", among which, Figure 1 As shown, the specific implementation steps are as follows: First, according to step 1, comprehensively collect basic information of the target bridge, including pier height, structure type (such as beam bridge, arch bridge, etc.), site type (determine the site soil type based on the geological survey report, etc.) and seismic fortification standard (determine the seismic fortification category of the bridge according to the local earthquake fortification intensity and relevant specifications, such as A, B, C, and D).

[0032] Then, according to step 2, the collected information is used to conduct seismic performance analysis to analyze the impact of these factors on the seismic performance of the bridge. For example, high-pier bridges are more likely to produce larger displacements and inertia forces during earthquakes, and soft soil foundation sites may amplify the effects of seismic waves. Based on the analysis results, it is determined whether it is necessary to adopt a seismic performance-based design target. If the bridge is located in a high earthquake risk area and has a complex structure, this design target should usually be adopted. This step closely combines the actual situation of the bridge with the specifications and standards to ensure the pertinence and rationality of the subsequent design.

[0033] Then, according to step 3, refer to the preset seismic performance target table shown in Table 1, and combine the determined seismic fortification category and earthquake level to select an accurate seismic performance target (for example, for a Class B bridge, the target is 1 under the E1 earthquake, the target is 2 under the fortification earthquake, and the target is 3 under the E2 earthquake).

[0034]

[0035] At the same time, the specific requirements for the seismic performance level of the structure under the selected performance target as shown in Table 2 are clarified, including standards for the degree of damage to bearing capacity, degree of ductile deformation, damage to key components (referring to components whose failure may cause structural damage or serious damage that endangers life safety, such as beams, main arch rings of arch bridges, etc.), ordinary components (referring to vertical components other than "key components") and energy-absorbing components (such as plastic hinge areas of piers, pier tie beams, vibration reduction and isolation bearings, etc.) and the possibility of continued use.

[0036]

[0037] Afterwards, follow step 4 to conduct an in-depth analysis of the degree and specific circumstances of the bridge structure exceeding the irregularity specified in the "Highway Bridge Seismic Design Code", including the planar irregularities (such as torsional irregularities, concave and convex irregularities, etc.) and vertical irregularities (such as lateral stiffness irregularities, sudden changes in floor bearing capacity, etc.) of the structure. By accurately evaluating these irregular factors, the site conditions (such as peak seismic acceleration, response spectrum characteristic period, etc.), earthquake levels and seismic parameters can be more accurately determined, making the design calculations more in line with the actual seismic stress state of the bridge, and effectively making up for the shortcomings of traditional design in dealing with irregular structures.

[0038] According to step 5, comprehensive calculation and analysis work is carried out on bridge structures of different performance levels according to the selected seismic performance target. For bridge structures of different performance levels, the bearing capacity design calculation is carried out strictly according to the corresponding calculation formula. In this embodiment, the performance levels include the first performance level, the second performance level, the third performance level, the fourth performance level and the fifth performance level.

[0039] Among them, the first performance level meets the elastic design requirements of the current specifications under the E1 earthquake action, and meets the following seismic bearing capacity calculation formula under the design earthquake action:

[0040] is the permanent action partial coefficient, is the permanent effect standard value, is the design value of the bridge structure bearing capacity, is the structural internal force of the standard value of horizontal earthquake action, is the structural internal force of the standard value of vertical earthquake action, is the partial coefficient of horizontal earthquake action, is the partial coefficient of horizontal seismic action; Among them, under the second performance level, under the design earthquake action or E2 earthquake action, the shear bearing capacity of the plastic energy dissipation zone and the seismic bearing capacity of key components meet the requirements of formula (1-1), among which, the positive section bearing capacity of the plastic energy dissipation zone should be verified as follows:

[0041] is the standard value of the bearing capacity of the bridge structure section, calculated according to the standard value of the material, and 0.4 is the combined value coefficient of the vertical seismic action; Among them, under the design earthquake action or E2 earthquake action of the third performance level, the normal section bearing capacity of key components and ordinary components meets the requirements of formula (1-2), the normal section bearing capacity of key components of the long-span bridge structure meets the requirements of formula (1-3), and some plastic hinge areas enter the yield stage, and their shear bearing capacity meets formula (1-2), where formula (1-3) is as follows:

[0042] 0.4 is the combined value coefficient of horizontal earthquake action; Among them, under the design earthquake action or E2 earthquake action of the 4th performance level, some ordinary components and most of the plastic hinge areas enter the yield stage, and the shear section of the reinforced concrete structure should meet the requirements of formula (1-4), which is as follows:

[0043] is the shear force of the member under gravity load, b is the width of the rectangular section or the thickness of the web of the T-shaped or I-shaped section, is the distance from the point of action of the longitudinal reinforcement force to the compression edge, It is the standard value of compressive strength of concrete cube with side length of 150mm; The shear section of the steel-concrete composite structure meets the requirements of formula (1-5), where formula (1-5) is as follows:

[0044] b is the width of the rectangular section or the thickness of the web of the T-shaped or I-shaped section, is the distance from the point of action of the longitudinal reinforcement force to the compression edge, is the cross-sectional area of ​​the steel beam of the steel-concrete composite structure, is the component shear force of the standard value of earthquake action, is the standard value of steel strength; Among them, under the action of E2 earthquake, in the 5th performance level, more ordinary components enter the yield stage, and the shear section of the ordinary components meets the requirements of formula (1-4) or formula (1-5), allowing some plastic energy-absorbing components to suffer relatively serious damage, and the elastic-plastic displacement of the structure meets the maximum elastic-plastic displacement limit of the structure.

[0045] Here, in the seismic performance-based design method of the present invention, the second performance level has a clear seismic target setting, for example, under the design earthquake action or the E2 earthquake action, there are clear performance expectations for the structural components, so the design calculation of the reinforced concrete components is given by the second performance level, which is as follows: When the second performance level is under the design earthquake action or E2 earthquake action, the stress and deformation of reinforced concrete components need to meet the following standards: like Figure 2 As shown in the figure, when the reinforced concrete member is a bending member, the calculation of its positive section bending bearing capacity should comply with the following formula:

[0046] is the bending moment caused by the structural gravity, is the bending moment caused by the lateral earthquake action, is the bending moment caused by vertical earthquake action, x is the height of the equivalent compression zone of concrete, is the standard value of concrete axial compressive strength, b is the width of rectangular section or the thickness of web of T-shaped or I-shaped section, is the distance from the point of action of the longitudinal reinforcement force to the compression edge, is the standard value of compressive strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​the longitudinal ordinary steel bars in the compression zone, is the standard value of compressive strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​the longitudinal prestressed tendons in the compression zone, is the stress of the prestressed tendon when the normal stress of concrete at the resultant force point of the prestressed tendon in the compression zone is equal to zero, is the distance from the longitudinal ordinary steel bar in the compression zone to the edge of the compression zone, It is the distance from the longitudinal prestressed tendons in the compression zone to the edge of the compression zone.

[0047] Reference Figure 3 As shown, the height x of the equivalent compression zone of the above concrete is calculated by the following formula:

[0048] x is the height of the equivalent compression zone of concrete, is the standard value of concrete axial compressive strength, is the width of a rectangular section or the thickness of a web of a T-shaped or I-shaped section, is the standard value of tensile strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​the longitudinal ordinary steel bars in the tension zone, is the standard value of tensile strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​the longitudinal prestressed tendons in the tension zone.

[0049] By accurately defining the mathematical relationship between the height x of the equivalent compressive zone of concrete and the material properties of steel bars and concrete as well as the geometric parameters of the member cross section, a core basis is provided for accurately calculating the bearing capacity of reinforced concrete members under different stress states.

[0050] At the same time, under this condition, the compressive bearing capacity of the positive section of the axially compressed member in the above reinforced concrete member should meet the following requirements:

[0051] is the structural axial force caused by structural gravity, is the structural axial force caused by lateral earthquake action, is the structural axial force caused by vertical earthquake action, is the standard value of concrete axial compressive strength, is the gross cross-sectional area of ​​the component, is the standard value of compressive strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​all longitudinal ordinary steel bars, is the stability factor of the axially compressed member.

[0052] like Figure 4 As shown in the figure, when the reinforced concrete member is a bending member, the calculation of the shear bearing capacity of its inclined section complies with the provisions of (2-4) to (2-7): ; ; ; ;

[0053] is the standard value of the shear bearing capacity of concrete and stirrups in the inclined section, is the standard value of shear bearing capacity of ordinary bent steel bars intersecting with inclined sections, is the standard value of the shear bearing capacity of the prestressed bent steel bar intersecting the inclined section, is the shear force caused by the structural gravity, is the shear force caused by earthquake action, is the influence coefficient of the bending moment of opposite sign. When calculating the shear bearing capacity of the beam section near the edge support of the simply supported beam and the continuous beam, it is taken as 1.0. When calculating the shear bearing capacity of the beam section near the middle support of the continuous beam and the cantilever beam, it is taken as 0.9. is the prestressing factor, which is 1.0 for reinforced concrete flexural members and 1.25 for prestressed concrete flexural members. is the influence coefficient of the compression flange, which is taken as 1.0 for rectangular sections and 1.1 for T-shaped and I-shaped sections; is the width of a rectangular section or the thickness of a web of a T-shaped or I-shaped section, is the distance from the point of action of the longitudinal reinforcement to the compression edge, P is the reinforcement percentage of the longitudinal tensile reinforcement in the inclined section, P≤2.5, is the reinforcement ratio of stirrups in the inclined section, is the reinforcement ratio of the vertical prestressed tendons in the inclined section, is the standard value of the tensile strength of stirrups, is the standard value of tensile strength of vertical prestressed tendons, is the standard value of tensile strength of ordinary bent steel bars, is the cross-sectional area of ​​the ordinary bent steel bar in the same bending plane in the inclined section, is the angle between the tangent line of the ordinary bent steel bar and the horizontal line, is the standard value of tensile strength of prestressed bent reinforcement, is the cross-sectional area of ​​the prestressed bent reinforcement in the same bending plane in the inclined section, It is the angle between the tangent line of the prestressed bent reinforcement and the horizontal line.

[0054] At the same time, in this embodiment, for the steel-concrete composite beam, design calculations are performed in the positive moment section and the negative moment section according to specific formulas, so as to fully consider the mechanical properties of the steel-concrete composite beam under different stress states, as follows: like Figure 5-Figure 6 As shown in the figure, in the positive moment section, when the plastic neutral axis 1 of the composite section is inside the concrete slab, if Conditions, the compressive bearing capacity of the positive section should be calculated according to the following formula: ; ;

[0055] Among them, A and b e 、h c is the cross-sectional parameter of the steel-concrete composite beam, M ik 、M Ehk 、M EVK is the corresponding bending moment, and the reinforcement and size of the concrete slab and steel beam are determined based on the calculation results. is the bending moment caused by the structural gravity, is the bending moment caused by the lateral earthquake action, is the bending moment caused by vertical earthquake action, 0.4 is the combination value coefficient of vertical earthquake action, is the cross-sectional area of ​​the steel beam, x is the height of the compression zone of the concrete slab, y is the distance between the resultant force of the steel beam cross-sectional area and the resultant force of the compression zone of the concrete, is the effective width of the concrete slab, It is the standard value of concrete axial compressive strength.

[0056] like Figure 7 As shown in the figure, when the plastic neutral axis 1 of the composite section is inside the concrete slab, if Conditions, the compressive bearing capacity of the positive section should be calculated according to the following formula: ; ;

[0057] is the effective width of the concrete slab, is the concrete slab section height, is the height of the compression zone of the steel beam section, is the standard value of tensile strength of steel beam section, is the distance between the resultant force point in the tension zone of the steel beam and the resultant force point in the compression zone of the concrete, It is the distance from the resultant force point in the tension zone of the steel beam to the resultant force point in the compression zone of the steel beam.

[0058] like Figure 8-Figure 9 As shown in the figure, in the negative moment section, when the plastic neutral axis 2 of the steel beam is in the steel-concrete composite beam, the compressive bearing capacity of its positive section should comply with the provisions of formulas (3-5) to (3-7):

[0059] is the plastic section moment of inertia of the steel beam section, is the standard value of steel bar tensile strength, is the distance from the plastic neutral axis of the composite beam to the steel bar resultant point, is the distance from the plastic neutral axis of the composite beam to the plastic neutral axis of the steel beam, is the cross-sectional area of ​​the steel bars in the concrete slab, is the cross-sectional area of ​​the steel beam, is the height of the compression zone of the steel beam section.

[0060] By calculating the positive and negative moment sections of steel-concrete composite beams, the bearing capacity of each area under different earthquake levels can be accurately evaluated, and factors such as the position of the plastic neutral axis of the composite section and material properties can be considered to achieve refined design. This can not only ensure that the steel-concrete composite beam has sufficient strength and deformation capacity throughout the earthquake process, but also avoid structural failure due to damage to a certain section.

[0061] Finally, in the calculation process, the possible weak parts of the bridge structure and the key parts that need to be strengthened are accurately found according to the calculation results. For example, under certain performance levels, some ordinary components or plastic hinge areas may experience stress concentration or insufficient bearing capacity. Then, using finite element analysis software, input seismic waves that meet site conditions and seismic fortification requirements, comprehensively simulate the stress, deformation and damage of the bridge under different earthquake levels, conduct strict verification and analysis of the design, and determine whether it meets the selected seismic performance goals. If weak links or parts that do not meet performance requirements are found in the structure during the verification process, the design is optimized and adjusted in a timely manner, and verification and analysis are performed again after adjustment, and this process is repeated until the structure fully meets the seismic performance-based design requirements.

[0062] Through the above design process and specific implementation process, the present invention can effectively realize the seismic performance-based design of highway bridge structures and improve the safety and stability of bridges during earthquakes.

[0063] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 in the scope of protection of the present invention.

Claims

1. A method for seismic performance-based design of highway bridge structures, characterized in that: The design method proceeds as follows: Step 1: Obtain basic information of the target bridge, including pier height, structure type, site type, and seismic fortification standards; Step 2: Perform seismic performance analysis on the target bridge based on the information obtained in step 1 to obtain the seismic fortification category and earthquake level of the target bridge; Step 3: According to the seismic fortification category and earthquake level of the target bridge, select the corresponding seismic performance target from the preset seismic performance target table; Step 4: Analyze and determine the extent and condition of bridge structure irregularities exceeding those specified in the Code for Seismic Design of Highway Bridges, which is used to determine site conditions, earthquake levels, and ground motion parameters; Step 5: Based on the selected seismic performance target, calculate and analyze bridge structures with different performance levels to demonstrate that the structure can meet the seismic performance requirements, including bearing capacity design calculations for bridge structures with different performance levels and design calculations for steel-concrete composite beams. Based on the calculation results, find out the weak parts of the bridge structure and the key parts that need to be strengthened, and then verify and adjust the design of the weak parts and key parts.

2. A highway bridge structure seismic performance-based design method according to claim 1, characterized in that: The performance levels include a first performance level, a second performance level, a third performance level, a fourth performance level, and a fifth performance level; The first performance level is designed to meet the elastic design specifications of the current "Highway Bridge Seismic Design Specifications" for its bearing capacity and deformation under the E1 earthquake. Under the design earthquake, the seismic bearing capacity of the bridge structure meets the following formula: ； is the permanent action partial coefficient, is the permanent effect standard value, is the design value of the bridge structure bearing capacity, is the structural internal force of the standard value of horizontal earthquake action, is the structural internal force of the standard value of vertical earthquake action, is the partial coefficient of horizontal earthquake action, is the partial coefficient of horizontal seismic action; Under the design earthquake action or E2 earthquake action, the shear bearing capacity of the plastic energy dissipation zone and the seismic bearing capacity of key components of the second performance level meet the requirements of formula (1-1), wherein the normal section bearing capacity of the plastic energy dissipation zone meets the following formula: ； is the standard value of the bearing capacity of the bridge structure section, calculated according to the standard value of the material, and 0.4 is the combined value coefficient of the vertical seismic action; In the third performance level, under the design earthquake action or E2 earthquake action, the normal section bearing capacity of key components and ordinary components meets the requirements of formula (1-2), the normal section bearing capacity of key components of the long-span bridge structure meets the requirements of formula (1-3), and some plastic hinge areas enter the yield stage, and their shear bearing capacity meets formula (1-2), where formula (1-3) is as follows: ； 0.4 is the combined value coefficient of horizontal earthquake action; Under the design earthquake or E2 earthquake, some common components and most of the plastic hinge areas enter the yield stage. The shear section of the reinforced concrete structure should meet the requirements of formula (1-4), which is as follows: ； is the shear force of the member under gravity load, b is the width of the rectangular section or the thickness of the web of the T-shaped or I-shaped section, is the distance from the point of action of the longitudinal reinforcement force to the compression edge, It is the standard value of compressive strength of concrete cube with side length of 150mm; The shear section of the steel-concrete composite structure meets the requirements of formula (1-5), where formula (1-5) is as follows: ； b is the width of the rectangular section or the thickness of the web of the T-shaped or I-shaped section, is the distance from the point of action of the longitudinal reinforcement force to the compression edge, is the cross-sectional area of ​​the steel-concrete composite structure steel beam, is the component shear force of the standard value of earthquake action, is the standard value of steel strength; In the fifth performance level, under the action of E2 earthquake, more common components enter the yield stage, and the shear section of the common components meets the requirements of formula (1-4) or formula (1-5), allowing some plastic energy-absorbing components to be severely damaged, and the elastic-plastic displacement of the structure meets the maximum elastic-plastic displacement limit of the structure.

3. A highway bridge structure seismic performance-based design method according to claim 2, characterized in that: The second performance level, when subjected to the design earthquake or E2 earthquake, the stress and deformation of reinforced concrete components must meet the following standards: When the reinforced concrete member is a bending member, the calculation of its normal section bending bearing capacity shall comply with the following formula: ； is the bending moment caused by the gravity of the structure, is the bending moment caused by the lateral earthquake action, is the bending moment caused by vertical earthquake action, x is the height of the equivalent compression zone of concrete, is the standard value of concrete axial compressive strength, b is the width of rectangular section or the thickness of web of T-shaped or I-shaped section, is the distance from the point of action of the longitudinal reinforcement force to the compression edge, is the standard value of compressive strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​the longitudinal ordinary steel bars in the compression zone, is the standard value of compressive strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​the longitudinal prestressed tendons in the compression zone, is the stress of the prestressed tendon when the normal stress of concrete at the resultant force point of the prestressed tendon in the compression zone is equal to zero, is the distance from the longitudinal ordinary steel bar in the compression zone to the edge of the compression zone, It is the distance from the longitudinal prestressed tendons in the compression zone to the edge of the compression zone.

4. A highway bridge structure seismic performance-based design method according to claim 3, characterized in that: The height x of the equivalent compression zone of concrete is calculated by the following formula: ； x is the height of the equivalent compression zone of concrete, is the standard value of concrete axial compressive strength, is the width of a rectangular section or the thickness of a web of a T-shaped or I-shaped section, is the standard value of tensile strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​the longitudinal ordinary steel bars in the tension zone, is the standard value of tensile strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​the longitudinal prestressed tendons in the tension zone.

5. The seismic performance-based design method for highway bridge structures according to claim 3 is characterized in that: The compressive bearing capacity of the positive section of the axially compressed member in the reinforced concrete member shall comply with the following formula: ； is the structural axial force caused by structural gravity, is the structural axial force caused by lateral earthquake action, is the structural axial force caused by vertical earthquake action, is the standard value of concrete axial compressive strength, is the gross cross-sectional area of ​​the component, is the standard value of compressive strength of longitudinal ordinary steel bars, is the cross-sectional area of ​​all longitudinal ordinary steel bars, is the stability factor of the axially compressed member.

6. A highway bridge structure seismic performance-based design method according to claim 3, characterized in that: When the reinforced concrete member is a bending member, the calculation of the shear bearing capacity of its inclined section shall comply with the provisions of (2-4) to (2-7): ； ； ； ； is the standard value of the shear bearing capacity of concrete and stirrups in the inclined section, is the standard value of shear bearing capacity of ordinary bent steel bars intersecting with inclined sections, is the standard value of the shear bearing capacity of the prestressed bent steel bar intersecting the inclined section, is the shear force caused by the structural gravity, is the shear force caused by earthquake action, is the influence coefficient of the bending moment of opposite sign. When calculating the shear bearing capacity of the beam section near the edge support of the simply supported beam and the continuous beam, it is taken as 1.

0. When calculating the shear bearing capacity of the beam section near the middle support of the continuous beam and the cantilever beam, it is taken as 0.

9. is the prestressing factor, which is 1.0 for reinforced concrete flexural members and 1.25 for prestressed concrete flexural members. is the influence coefficient of the compression flange, which is 1.0 for rectangular sections and 1.1 for T-shaped and I-shaped sections; b is the width of the rectangular section or the thickness of the web of the T-shaped or I-shaped section, is the distance from the point of action of the longitudinal reinforcement to the compression edge, P is the reinforcement percentage of the longitudinal tensile reinforcement in the inclined section, P≤2.5, is the reinforcement ratio of stirrups in the inclined section, is the reinforcement ratio of the vertical prestressed tendons in the inclined section, is the standard value of the tensile strength of stirrups, is the standard value of tensile strength of vertical prestressed tendons, is the standard value of tensile strength of ordinary bent steel bars. is the cross-sectional area of ​​the ordinary bent steel bar in the same bending plane in the inclined section, is the angle between the tangent line of the ordinary bent steel bar and the horizontal line, is the standard value of tensile strength of prestressed bent reinforcement, is the cross-sectional area of ​​the prestressed bent reinforcement in the same bending plane in the inclined section, It is the angle between the tangent line of the prestressed bent reinforcement and the horizontal line.

7. The seismic performance-based design method for highway bridge structures according to claim 1, characterized in that: The steel-concrete composite beam design calculation steps include a positive moment section and a negative moment section; In the positive moment section, when the plastic neutral axis (1) of the composite section is inside the concrete slab, if Conditions, the compressive bearing capacity of the positive section should be calculated according to the following formula: ； ； Among them, A and b e 、h c is the cross-sectional parameter of the steel-concrete composite beam, M ik 、M Ehk 、M EVK is the corresponding bending moment, and the reinforcement and size of the concrete slab and steel beam are determined based on the calculation results. is the bending moment caused by the gravity of the structure, is the bending moment caused by the lateral earthquake action, is the bending moment caused by vertical earthquake action, 0.4 is the combination value coefficient of vertical earthquake action, is the cross-sectional area of ​​the steel beam, x is the height of the compression zone of the concrete slab, y is the distance between the resultant force of the steel beam cross-sectional area and the resultant force of the compression zone of the concrete, is the effective width of the concrete slab, It is the standard value of concrete axial compressive strength.

8. A method for seismic performance-based design of highway bridge structures according to claim 7, characterized in that , in the positive moment section, when the plastic neutral axis (1) of the composite section is inside the concrete slab, if Conditions, the compressive bearing capacity of the positive section should be calculated according to the following formula: ； ； is the effective width of the concrete slab, is the concrete slab section height, is the height of the compression zone of the steel beam section, is the standard value of tensile strength of steel beam section, is the distance between the resultant force point in the tension zone of the steel beam and the resultant force point in the compression zone of the concrete, It is the distance from the resultant force point in the tension zone of the steel beam to the resultant force point in the compression zone of the steel beam.

9. A highway bridge structure seismic performance-based design method according to claim 7, characterized in that: In the negative moment section, the compressive bearing capacity of the positive section of the steel-concrete composite beam shall comply with the provisions of formulas (3-5) to (3-7): ； is the plastic section moment of inertia of the steel beam section, is the standard value of steel bar tensile strength, is the distance from the plastic neutral axis of the composite beam to the steel bar resultant point, is the distance from the plastic neutral axis of the composite beam to the plastic neutral axis of the steel beam, is the cross-sectional area of ​​the steel bars in the concrete slab, is the cross-sectional area of ​​the steel beam, is the height of the compression zone of the steel beam section.

10. The method for seismic performance-based design of highway bridge structures according to claim 1, characterized in that: The design verification and adjustment steps also include the following steps: S51. Conduct seismic response analysis on the designed bridge structure through finite element analysis software. During the analysis, input seismic waves that meet site conditions and seismic fortification requirements to fully simulate the stress, deformation and damage of the bridge under different earthquake levels to verify whether the selected seismic performance target is met; S52. If during the verification process it is found that the structure has weak links or parts that do not meet the performance requirements, the design should be optimized and adjusted. After the adjustment, verification and analysis should be carried out again until the structure fully meets the seismic performance-based design requirements.

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