A performance-based seismic design method for highway bridge structures

Abstract

The present invention discloses a performance-based seismic design method for highway bridge structures, which relates to the field of bridge seismic resistance. Its steps are as follows: First, obtain the basic information of the target bridge such as pier height and structural type. Then, conduct seismic performance analysis based on this to determine the fortification category and seismic level. Subsequently, select the appropriate seismic performance objectives from the preset table. After that, analyze the irregularity degree of the bridge, etc. to determine the site and earthquake-related parameters. Then, calculate and analyze the bridge structure and steel-concrete composite beam at different performance levels according to the selected objectives, find out the weak and key parts and verify and adjust them. The present invention constructs a scientific, systematic and quantitative design system, breaks through the limitations of traditional design, effectively solves the problem of the lack of quantitative indicators for "repairable in moderate earthquake", comprehensively considers multiple factors, selects objectives through scientific demonstration, strictly verifies the design, ensures rationality and reliability, creates a complete and efficient new technical solution for highway bridge seismic design, and effectively guarantees the safety performance of the bridge during earthquakes.

Description

Technical Field

[0001] The present invention relates to the field of seismic resistance of bridges, and particularly to a performance-based seismic design method for highway bridge structures. Background Art

[0002] In the construction of highway traffic infrastructure, bridges, as key connecting links, their seismic performance is directly related to the safety and smoothness of transportation. With the continuous development of the economic society, the construction scale of highway bridges is constantly expanding, and their safety under earthquake disasters has received increasing attention.

[0003] Traditional seismic design of highway bridges mainly follows the three-level and two-stage design method adopted in the current "Code for Seismic Design of Highway Bridges" (JTG / T 2231-01-2020). Among them, the three levels are "not damaged under minor earthquakes, reparable under moderate earthquakes, and not collapsing under major earthquakes", and the two stages are elastic bearing capacity verification under "minor earthquakes" and elastoplastic deformation verification under "major earthquakes". Under this design framework, the performance objectives of "not damaged under minor earthquakes" and "not collapsing under major earthquakes" have relatively clear quantitative parameters, which makes it easier to operate and control in actual design. However, for the key performance objective of "reparable under moderate earthquakes", the code only gives qualitative descriptions, and in design practice, it mostly relies on construction measures to achieve.

[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 seismic actions, factors such as the seismic characteristics of different regions, the functional requirements of bridges, and the structural forms are complex and diverse, and a single design strategy is difficult to fully adapt to. For example, in some earthquake-prone areas with complex ground motion characteristics, relying solely on high-ductility design may not effectively guarantee the overall performance of bridges under moderate and major earthquakes; while at some transportation hubs with extremely high requirements for the continuity of bridge functions, low elastic bearing capacity design may lead to long repair cycles for bridges after moderate earthquakes, seriously affecting transportation efficiency.

[0005] In addition, with the continuous development of bridge construction technology, new materials and complex structural forms (such as long-span steel-concrete composite structure bridges, special-shaped arch bridges, etc.) have emerged continuously, and traditional design methods are becoming increasingly inadequate in dealing with these new situations. For these new bridge structures, how to accurately evaluate their seismic performance under different seismic levels and achieve a reasonable match between bearing capacity and ductility has become an urgent problem to be solved. At the same time, in the construction of urban bridges, due to factors such as complex surrounding environments and limited space, higher requirements are put forward for the reparability and rapid functional recovery ability of bridges after earthquakes, and traditional design methods have obvious deficiencies in meeting these special requirements. Summary of the Invention

[0006] The object of the present invention is to provide a performance-based seismic design method for highway bridge structures, which establishes a scientific, systematic and quantifiable performance-based seismic design method for highway bridge structures, accurately realizes different seismic performance objectives such as "repairable in moderate earthquake", and comprehensively considers various factors such as pier height, structural regularity, site type, seismic fortification standard, etc. in the design process. Then, through scientific analysis and demonstration, a suitable seismic performance objective is selected, and through strict design verification and adjustment, the rationality and reliability of the design are ensured, providing a complete and effective technical means for the seismic design of highway bridges.

[0007] The present invention is realized by the following technical solutions:

[0008] A performance-based seismic design method for highway bridge structures, and this design method is carried out according to the following steps:

[0009] Step 1: Obtain the basic information of the target bridge, including pier height, structural type, site type and seismic fortification standard;

[0010] Step 2: Conduct seismic performance analysis on the target bridge according to the information obtained in Step 1 to obtain the seismic fortification category and seismic level of the target bridge;

[0011] Step 3: Select the corresponding seismic performance objective from the preset seismic performance objective table according to the seismic fortification category and seismic level of the target bridge;

[0012] Step 4: Analyze and determine the degree and situation of the bridge structure exceeding the irregular bridge determined by the "Code for Seismic Design of Highway Bridges" to determine the site conditions, seismic level and ground motion parameters;

[0013] Step 5: According to the selected seismic performance objective, through calculation and analysis of bridge structures at different performance levels, demonstrate that the structure can meet the seismic performance requirements. Among them, it includes carrying out bearing capacity design calculations on bridge structures at different performance levels and designing and calculating steel-concrete composite beams. According to the calculation results, find out the weak parts and key parts that need to be strengthened in the bridge structure, and then conduct design verification and adjustment on the weak parts and key parts.

[0014] In this solution, by sequentially performing operations such as obtaining the basic information of the bridge, conducting seismic performance analysis, selecting seismic performance objectives, determining the degree and situation of irregularity, and performing structural calculations and analyses based on the selected objectives, a performance-based seismic design method for highway bridge structures with quantitative indicators is provided for bridge seismic design. These steps can not only fully consider the characteristics of different bridges, site conditions, and seismic requirements, but also accurately locate the weak and key parts of the structure. Through design verification and adjustment, it is ensured that the bridge meets the seismic performance requirements under different seismic levels, effectively solving the problems of traditional design in aspects such as "repairable under medium earthquake", and significantly improving the seismic reliability of the bridge.

[0015] Further optimize the solution, and the performance levels include the 1st performance level, the 2nd performance level, the 3rd performance level, the 4th performance level, and the 5th performance level;

[0016] Among them, for the 1st performance level, under the action of the E1 earthquake, its bearing capacity and deformation meet the elastic design specifications of the current "Code for Seismic Design of Highway Bridges", and under the action of the fortification earthquake, the seismic bearing capacity of the bridge structure satisfies the following formula:

[0017]

[0018] γ G is the partial coefficient of permanent action, G ik is the standard value of permanent action, R d is the design value of the bearing capacity of the bridge structure, S Ehk is the structural internal force of the standard value of the horizontal seismic action, S Evk is the structural internal force of the standard value of the vertical seismic action, γ Eh is the partial coefficient of horizontal seismic action, γ Ev is the partial coefficient of vertical seismic action;

[0019] For the 2nd performance level, under the action of the fortification earthquake or the E2 earthquake, the shear bearing capacity of the plastic energy dissipation zone and the seismic bearing capacity of the key components satisfy the provisions of formula (1-1). Among them, the normal section bearing capacity of the plastic energy dissipation zone satisfies the following formula:

[0020]

[0021] G ik is the standard value of permanent action, R k is the standard value of the cross-section bearing capacity of the bridge structure, calculated according to the material standard value, and 0.4 is the combination value coefficient of the vertical seismic action;

[0022] Under the fortification earthquake action or E2 earthquake action, the flexural bearing capacity of the key components and ordinary components meets the requirements of formula (1-2), and the flexural bearing capacity of the key components of the long-span bridge structure meets the requirements of formula (1-3). Some plastic hinge regions enter the yield stage, and their shear bearing capacity meets the requirements of formula (1-2). Among them, formula (1-3) is as follows:

[0023]

[0024] 0.4 is the combination value coefficient of the horizontal earthquake action;

[0025] Under the fortification earthquake action or E2 earthquake action, some ordinary components and most plastic hinge regions enter the yield stage. The shear section of the reinforced concrete structure should meet the requirements of formula (1-4), and formula (1-4) is as follows:

[0026] V G +V Ek ≤0.15f cu，k bh0 (1-4)

[0027] V G is the shear force of the component under the action of gravity load, b is the width of the rectangular section or the web thickness of the T-shaped or I-shaped section, h0 is the distance from the resultant force point of the longitudinal reinforcement to the compression edge, and f cu,k is the standard value of the cubic compressive strength of concrete with a side length of 150mm;

[0028] The shear section of the steel-concrete composite structure meets the requirements of formula (1-5), and among them, formula (1-5) is as follows:

[0029] V G +V Ek ≤0.15f cu，k bh0+0.25f ak A a (1-5)

[0030] b is the width of the rectangular section of the concrete structure or the web thickness of the T-shaped or I-shaped section, h0 is the distance from the resultant force point of the longitudinal reinforcement to the compression edge, and A a is the cross-sectional area of the steel beam of the steel-concrete composite structure, V Ek is the shear force of the component under the standard value of the earthquake action, and f cu,k is the standard value of the cubic compressive strength of concrete with a side length of 150mm, and f ak is the standard value of the strength of the steel;

[0031] Under the action of the E2 earthquake, for the 5th performance level, a relatively large number of ordinary components enter the yielding stage. The shear cross-section of the ordinary components meets the requirements of formula (1-4) or formula (1-5). Partial plastic energy-dissipating components are allowed to undergo relatively severe damage, and the elastoplastic displacement of the structure meets the limit value of the maximum elastoplastic displacement of the structure.

[0032] In this solution, the specific design requirements of the bridge structure under different seismic actions from the 1st to the 5th performance levels are defined in detail, providing accurate and operable quantitative criteria for the entire seismic design. In each performance level, the calculation formulas and conditions of key indicators such as seismic bearing capacity, flexural and shear bearing capacities of the normal section, shear cross-section requirements, and performance of the plastic hinge region are clearly specified, enabling designers to carry out precise designs based on these clear criteria, ensuring that the performance of the bridge structure under different seismic levels is predictable and controllable, strongly supporting the seismic performance-based design goal with quantitative indicators pursued by the invention, guaranteeing the safety and stability of the bridge during earthquakes, and effectively making up for the deficiencies of traditional design methods in refined design.

[0033] For a further optimized solution, when under the action of the fortification earthquake or the E2 earthquake, for the 2nd performance level, the stress and deformation conditions of the reinforced concrete components need to meet the following standards:

[0034] When the reinforced concrete component is a flexural member, the calculation of the flexural bearing capacity of its normal section shall comply with the following formula:

[0035]

[0036] M ik is the bending moment caused by the structural gravity, M Ehk is the bending moment caused by the lateral seismic action, M Evk is the bending moment caused by the vertical seismic action, x is the equivalent compression zone height of the concrete, f ck is the standard value of the axial compressive strength of the concrete, b is the width of the rectangular section or the web thickness of the T-shaped or I-shaped section, h0 is the distance from the resultant force point of the longitudinal reinforcement to the compression edge, f' sk is the standard value of the compressive strength of the longitudinal ordinary reinforcement, A' s is the cross-sectional area of the longitudinal ordinary reinforcement in the compression zone, f' pk is the standard value of the compressive strength of the longitudinal ordinary reinforcement, A' p is the cross-sectional area of the longitudinal prestressed reinforcement in the compression zone, σ' p0 is the stress of the prestressed reinforcement when the concrete stress corresponding to the resultant force point in the compression zone is zero, a' s is the distance from the longitudinal ordinary reinforcement in the compression zone to the compression edge, a' p is the distance from the longitudinal prestressed reinforcement in the compression zone to the compression edge.

[0037] In this solution, for the stress and deformation of reinforced concrete flexural members under the fortification earthquake or E2 earthquake at the second performance level, clear and key calculation criteria for the flexural bearing capacity of the normal section are given. By introducing parameters such as the bending moment caused by the structural gravity, lateral and vertical seismic actions, and combining with the relevant regulations of the equivalent compression zone height of concrete, the bearing capacity requirements of the members under complex seismic conditions are accurately quantified. This not only provides scientific and specific guidance for designers to design reinforced concrete flexural members at 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 during earthquakes, and guarantees the overall safety and stability of the bridge structure under the corresponding seismic actions.

[0038] To further optimize the solution, the equivalent compression zone height x of the concrete is calculated according to the following formula:

[0039] f sk A s +f pk A p =f ck bx+f' sk A' s +(f' pk -σ' p0 )A' p (2-2)

[0040] x is the equivalent compression zone height of the concrete, f ck is the standard value of the axial compressive strength of the concrete, b is the width of the rectangular section or the web thickness of the T-shaped or I-shaped section, f sk is the standard value of the tensile strength of the longitudinal ordinary reinforcement, A s is the cross-sectional area of the longitudinal ordinary reinforcement in the tension zone, f pk is the standard value of the tensile strength of the longitudinal ordinary reinforcement, A p is the cross-sectional area of the longitudinal prestressed reinforcement in the tension zone, f' sk is the standard value of the compressive strength of the longitudinal ordinary reinforcement, A' s is the cross-sectional area of the longitudinal ordinary reinforcement in the compression zone, f' pk is the standard value of the compressive strength of the longitudinal ordinary reinforcement, A' p is the cross-sectional area of the longitudinal prestressed reinforcement in the compression zone, σ' p0 is the stress of the prestressed reinforcement when the concrete stress corresponding to the resultant force point in the compression zone is zero.

[0041] In this solution, by precisely defining the mathematical relationship between the equivalent compression zone height x of concrete, the material properties of steel bars and concrete, and the geometric parameters of the component cross-section, it provides the core basis for accurately calculating the bearing capacity of reinforced concrete components under different stress states. During the seismic design process, especially for the design calculations of the second performance level and other related performance levels, it can help designers accurately evaluate the bearing capacity and deformation characteristics of components under seismic actions, ensuring that the designed components meet the predetermined seismic performance requirements.

[0042] For further optimized solutions, the axial compressive bearing capacity of the normal cross-section of the axially compressed member in the reinforced concrete component shall comply with the following formula:

[0043]

[0044] N ik is the axial force of the structure caused by the structural gravity, N Ehk is the axial force of the structure caused by the lateral seismic action, N Evk is the axial force of the structure caused by the vertical seismic action, f ck is the standard value of the axial compressive strength of concrete, A is the gross cross-sectional area of the component, f' sk is the standard value of the compressive strength of longitudinal ordinary steel bars, A' s is the cross-sectional area of all longitudinal ordinary steel bars, is the stability coefficient of the axially compressed member.

[0045] In this solution, by incorporating the axial forces caused by structural gravity and seismic actions, as well as the material properties of steel bars and concrete and the geometric parameters of the component into the formula for calculation, designers can accurately evaluate the compressive capacity of axially compressed members at different seismic levels based on this quantitative formula. This not only ensures the scientificity and rationality of component design, guarantees that it can effectively bear the pressure during an earthquake and maintain the stability of the structure, but also lays a solid foundation for the quantitative system of the seismic performance-based design of the entire bridge structure.

[0046] For further optimized solutions, when the reinforced concrete component is a flexural member, the calculation of its shear resistance of the inclined section complies with the provisions of (2-4) to (2-7):

[0047]

[0048] V sbk = 0.75×10 -3 f sk ∑A sb sinθ s (2-6)

[0049] V pbk = 0.75×10 -3 f pk∑A pb sinθ p (2-7)

[0050] V csk is the standard value of the shear resistance of concrete and stirrups in the inclined section, V sbk is the standard value of the shear resistance of ordinary bent-up bars intersecting the inclined section, V pbk is the standard value of the shear resistance of prestressed bent-up bars intersecting the inclined section, V ik is the shear force caused by the structural gravity, V Ek is the shear force caused by the seismic action. α1 is the influence coefficient of opposite-sign bending moments. When calculating the shear resistance of simply supported beams and the near-edge support beam segments of continuous beams, take 1.0; when calculating the shear resistance of the near-middle support beam segments of continuous beams and cantilever beams, take 0.9; α2 is the prestress improvement coefficient. For reinforced concrete flexural members, take 1.0; for prestressed concrete flexural members, take 1.25. α3 is the influence coefficient of the compression flange. For rectangular sections, take 1.0; for T-shaped and I-shaped sections, take 1.1; b is the width of the rectangular section or the web thickness of the T-shaped or I-shaped section, h0 is the distance from the resultant force action point of the longitudinal reinforcement to the compression edge, P is the reinforcement ratio of the longitudinal tensile reinforcement in the inclined section, P ≤ 2.5, f cu,k is the standard value of the cubic compressive strength of concrete with a side length of 150 mm, ρ sv is the reinforcement ratio of stirrups in the inclined section, ρ pv is the reinforcement ratio of vertical prestressed tendons in the inclined section, f svk is the standard value of the tensile strength of stirrups, f pvk is the standard value of the tensile strength of vertical prestressed tendons, f sk is the standard value of the tensile strength of ordinary bent-up bars, A sb is the cross-sectional area of ordinary bent-up bars in the same bent-up plane in the inclined section, θ s is the angle between the tangent of the ordinary bent-up bar and the horizontal line, f pk is the standard value of the tensile strength of prestressed bent-up bars, A pb is the cross-sectional area of prestressed bent-up bars in the same bent-up plane in the inclined section, θ p is the angle between the tangent of the prestressed bent-up bar and the horizontal line.

[0051] In this solution, the combined action of concrete and stirrups in the inclined section, the contribution of ordinary bent-up bars and prestressed bent-up bars to the shear bearing capacity are comprehensively considered. Through precise mathematical expressions, the shear resistance of each part is closely related to the material properties, geometric parameters of the component and the shear force generated under seismic action. In the seismic design of highway bridge structures, designers can accurately calculate the inclined section shear bearing capacity of flexural members under different seismic levels based on these formulas, and thus reasonably configure shear-resistant structures such as stirrups and bent-up bars to ensure that the components will not fail due to inclined section shear failure under seismic action, effectively guaranteeing the overall seismic performance of the bridge structure.

[0052] To further optimize the solution, the design calculation steps of the steel-concrete composite beam include the positive moment section and the negative moment section;

[0053] Among them, in the positive moment section, when the plastic neutral axis (1) of the composite section is within the concrete slab, if the condition Af ak ≤b e h c f ck is satisfied, the normal section compressive bearing capacity should be calculated according to the following formula:

[0054]

[0055] x = af ak / b e f ck (3-2)

[0056] where A, b e , h c are the section parameters of the steel-concrete composite beam, M ik , M Ehk , M EVK are the corresponding bending moments, and the steel bar reinforcement and dimensions of the concrete slab and steel beam are determined based on the calculation results. M ik is the bending moment caused by the structural gravity, M Ehk is the bending moment caused by the lateral seismic action, M Evk is the bending moment caused by the vertical seismic action, 0.4 is the combination value coefficient of the vertical seismic action, A 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 section and the resultant force of the concrete compression zone, b e is the effective width of the concrete slab, f ck is the standard value of the axial compressive strength of concrete.

[0057] In this solution, the design calculation method in the positive bending moment section is specified in detail, especially under the common and critical condition that the plastic neutral axis of the composite section is located within the concrete slab. By introducing the section parameters of the steel-concrete composite beam and the bending moments generated under different loads, an accurate calculation formula for the normal section compressive bearing capacity is given. This enables designers to accurately calculate the required compressive capacity of the steel-concrete composite beam under positive bending moment according to this formula and in combination with the specific parameters in the actual project, and then scientifically and reasonably determine the reinforcement and dimensions of the concrete slab and steel beam. This not only ensures the normal 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, contributing to the achievement of the overall seismic performance objectives of the bridge.

[0058] For the further optimized solution, in the positive bending moment section, when the plastic neutral axis (1) of the composite section is within the concrete slab, if the condition is met, the normal section compressive bearing capacity should be calculated according to the following formula:

[0059]

[0060] A c =0.5(A - b e h c f ck / f ak ) (3 - 4)

[0061] b e is the effective width of the concrete slab, h c is the cross-sectional height of the concrete slab, A c is the height of the compression zone of the steel beam cross-section, f ak is the standard value of the tensile strength of the steel beam cross-section, y1 is the distance from the resultant force point of the tensile zone of the steel beam to the resultant force point of the compression zone of the concrete, and y2 is the distance from the resultant force point of the tensile zone of the steel beam to the resultant force point of the compression zone of the steel beam.

[0062] In this solution, designers can substitute the actual project data for calculation, thereby accurately determining the value of the normal section compressive bearing capacity that meets the seismic performance requirements under this condition. Based on this, the reinforcement and dimensions of the concrete slab and steel beam are further determined to ensure that the positive bending moment section of the steel-concrete composite beam has sufficient strength and stability under earthquake action, effectively preventing structural damage caused by insufficient normal section compression.

[0063] For the further optimized solution, in the negative bending moment section, the normal section compressive bearing capacity of the steel-concrete composite beam should comply with the provisions of Formulas (3 - 5) to (3 - 7):

[0064]

[0065] M sk =Wnpx f ak (3 - 6)

[0066] f sk A s + f ak (A - A c ) = f ak A c (3 - 7)

[0067] W npx is the plastic section moment of inertia of the steel beam section, f sk is the standard value of the tensile strength of the steel bar, f ak is the standard value of the tensile strength of the steel beam section. y3 is the distance from the plastic neutral axis of the composite beam to the resultant force point of the steel bars, y4 is the distance from the plastic neutral axis of the composite beam to the plastic neutral axis of the steel beam, A s is the cross - sectional area of the steel bars in the concrete slab, A is the cross - sectional area of the steel beam section, A c is the height of the compression zone of the steel beam section.

[0068] In this solution, the mechanical properties of the steel - concrete composite beam under negative bending moment are comprehensively considered, including key factors such as structural gravity, the moment caused by seismic action, and the plastic section moment of inertia of the steel beam itself. Through precise mathematical relationships, it provides a basis for quantitative calculation for designers. During the seismic design of highway bridge structures, based on these formulas, the compressive bearing capacity of the steel - concrete composite beam in the negative bending moment section can be accurately evaluated, so as to reasonably design the connection structure between the steel beam and the concrete slab, the reinforcement method, etc., to ensure the structural safety of the negative bending moment section of the steel - concrete composite beam under complex load conditions such as earthquakes, and effectively prevent damage caused by insufficient compression.

[0069] To further optimize the solution, the following steps are also included in the design verification and adjustment steps:

[0070] S51. Conduct seismic response analysis on the designed bridge structure through finite - element analysis software. During the analysis, input seismic waves that meet the site conditions and seismic fortification requirements to comprehensively simulate the stress, deformation, and failure conditions of the bridge under different seismic levels, so as to verify whether it meets the selected seismic performance objectives;

[0071] S52. If weak links or parts that do not meet the performance requirements are found in the structure during the verification process, optimize and adjust the design. After the adjustment, verification analysis should be carried out again until the structure fully meets the requirements of seismic performance - based design.

[0072] In this solution, in step S51, a finite element analysis software is used for seismic response analysis. By inputting seismic waves that meet the actual site and fortification requirements, the true state of the bridge under different seismic levels can be accurately simulated, thus providing a scientific and intuitive basis for judging whether the selected seismic performance objectives are achieved. In step S52, optimization and adjustment are carried out for the weak or non-compliant parts found during verification, and repeated verification is performed to form a closed-loop process. This ensures the effective connection from theoretical calculation to actual performance in bridge design, makes up for possible design defects, greatly improves the reliability and accuracy of bridge seismic design, and strongly promotes the realization of the seismic performance-based design objective with quantitative indicators.

[0073] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0074] The present invention establishes a scientific, systematic and quantitative seismic performance-based design method, and accurately realizes different seismic performance objectives such as "repairable under medium earthquake". In the design process, various factors such as pier height and structural regularity are comprehensively considered. Through rigorous analysis, appropriate objectives are selected, and accurate calculation and verification adjustment are used to ensure the rationality and reliability of the design. There are detailed design calculation criteria for bridge structures and steel-concrete composite beams at different performance levels, overcoming the limitations of the traditional single design strategy, being able to better adapt to complex seismic characteristics, bridge function requirements and new structural forms, and effectively improving the safety and stability of highway bridge structures during earthquakes. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not constitute a limitation to the embodiments of the present invention. In the drawings:

[0076] Figure 1 is a schematic diagram of the seismic performance-based design process of the present invention;

[0077] Figure 2 is a schematic diagram of a reinforced concrete rectangular cross-section flexural member of the present invention;

[0078] Figure 3 is a simplified diagram for the seismic performance-based calculation of the flexural resistance of the normal section of a reinforced concrete rectangular cross-section flexural member of the present invention;

[0079] Figure 4 is a simplified diagram for the seismic performance-based calculation of the shear resistance of the inclined section of a reinforced concrete rectangular cross-section flexural member of the present invention;

[0080] Figure 5 is a schematic diagram of the structure with the plastic neutral axis in the concrete slab of the present invention;

[0081] Figure 6 is a simplified diagram for the seismic performance-based calculation with the plastic neutral axis in the concrete slab;

[0082] Figure 7 It is the simplified calculation diagram for the seismic performance-based design of the plastic neutral axis within the steel beam;

[0083] Figure 8 It is the structural schematic diagram of the steel-concrete composite beam under negative bending moment;

[0084] Figure 9 It is the simplified calculation diagram for the seismic performance-based design of the steel-concrete composite beam under negative bending moment.

[0085] Markings in the attached drawings and corresponding component names:

[0086] 1 - Plastic neutral axis of the composite section, 2 - Plastic neutral axis of the steel beam. Specific implementation manners

[0087] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments and the attached drawings. The illustrative implementation manners of the present invention and their descriptions are only used to explain the present invention and do not serve as a limitation to the present invention.

[0088] Embodiment

[0089] Since the traditional seismic design code for highway bridges only gives qualitative descriptions and solves problems 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 quantitatively indexed seismic performance-based design method for highway bridge structures. By pursuing the best balance between bearing capacity and ductility, it provides performance-based design solutions of "low elastic bearing capacity - high ductility" or "high elastic bearing capacity - low ductility", accurately achieving different seismic performance objectives such as "repairable under moderate earthquake", among which, as Figure 1 shown, the specific implementation steps are as follows:

[0090] First, according to step 1, comprehensively collect the basic information of the target bridge, including pier height, structural type (such as beam bridge, arch bridge, etc.), site type (determine the site soil category based on the geological exploration report, etc.), and seismic fortification standard (determine the seismic fortification category to which the bridge belongs, such as categories A, B, C, D, according to the local seismic fortification intensity and relevant specifications).

[0091] Then, according to step 2, use the collected information for seismic performance analysis to analyze the influence of these factors on the seismic performance of the bridge. For example, high-pier bridges are more likely to generate large displacements and inertial forces during earthquakes, and soft soil foundation sites may amplify the effect of seismic waves. According to the analysis results, judge whether it is necessary to adopt the seismic performance-based design objective. If the bridge is in a high-seismic-risk area and has a complex structure, this design objective should usually be adopted. This step closely combines the actual situation of the bridge with the specification standards to ensure the pertinence and rationality of the subsequent design.

[0092] Then, according to Step 3, referring to the preset seismic performance target table as shown in Table 1, and combining the determined seismic fortification category and earthquake level, select the accurate seismic performance target (for example, for a Class B bridge, the target is 1 under the action of E1 earthquake, 2 under the action of the fortification earthquake, and 3 under the action of E2 earthquake).

[0093] Table 1 Seismic Performance Target Table

[0094]

[0095] At the same time, clarify the specific requirements of the structural seismic performance level as shown in Table 2 under the selected performance target, including the degree of bearing capacity damage, the degree of ductility deformation, key components (referring to components whose failure may cause structural damage or serious damage endangering life safety, such as beam bodies, main arch rings of arch bridges, etc.), ordinary components (referring to vertical components other than "key components"), and the damage conditions and the possibility of continued use of energy dissipation components (such as plastic hinge areas of bridge piers, cross beams of bridge piers, seismic isolation and vibration reduction bearings, etc.) and other aspects of the standards.

[0096] Table 2 Structural Seismic Performance Level

[0097]

[0098] In the above formula, [ΔU e ——The elastic displacement limit value of the structure under the action of the standard value of wind load or E1 earthquake calculated by the elastic method, ——The elastoplastic deformation displacement limit value of the structure under the action of the standard value of E2 earthquake.

[0099] After that, according to Step 4, deeply analyze the degree and specific situation of the bridge structure exceeding the irregular bridge determined by the "Code for Seismic Design of Highway Bridges", including the plane irregularity of the structure (such as torsional irregularity, concave-convex irregularity, etc.) and vertical irregularity (such as lateral stiffness irregularity, sudden change of floor bearing capacity, etc.). By accurately evaluating these irregular factors, the site conditions (such as peak ground acceleration, response spectrum characteristic period, etc.), earthquake level and seismic motion parameters can be more accurately determined, making the design calculation more conform to the actual seismic force state of the bridge and effectively making up for the deficiencies of traditional design in dealing with irregular structures.

[0100] According to Step 5, carry out comprehensive calculation and analysis work on the bridge structures of different performance levels according to the selected seismic performance target. For the bridge structures of different performance levels, strictly carry out the bearing capacity design calculation according to the corresponding calculation formulas. 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.

[0101] Among them, the first performance level meets the elastic design requirements of the current code under the action of E1 earthquake and meets the following seismic bearing capacity calculation formula under the action of the fortification earthquake;

[0102]

[0103] γ G is the partial coefficient of permanent action, G ik is the standard value of permanent action, R d is the design value of the bearing capacity of the bridge structure, S Ehk is the structural internal force of the standard value of horizontal earthquake action, S Evk is the structural internal force of the standard value of vertical earthquake action, γ Eh is the partial coefficient of horizontal earthquake action, γ Ev is the partial coefficient of vertical earthquake action;

[0104] Among them, under the action of the fortification earthquake or E2 earthquake, the shear bearing capacity of the plastic energy dissipation zone and the seismic bearing capacity of the key components meet the provisions of formula (1-1) for the second performance level. Among them, the normal section bearing capacity of the plastic energy dissipation zone shall be checked against the following formula:

[0105]

[0106] G ik is the standard value of permanent action, R k is the standard value of the cross-section bearing capacity of the bridge structure, calculated according to the material standard value, and 0.4 is the combination value coefficient of vertical earthquake action;

[0107] Among them, under the action of the fortification earthquake or E2 earthquake, the normal section bearing capacity of the key components and ordinary components meets the provisions of formula (1-2) for the third performance level. The normal section bearing capacity of the key components of the long-span bridge structure meets the provisions of formula (1-3). Some plastic hinge regions enter the yield stage, and its shear bearing capacity meets formula (1-2). Among them, formula (1-3) is as follows:

[0108]

[0109] 0.4 is the combination value coefficient of horizontal earthquake action;

[0110] Among them, under the action of the fortification earthquake or E2 earthquake, for the fourth performance level, some ordinary components and most plastic hinge regions enter the yield stage. The shear section of the reinforced concrete structure shall meet the provisions of formula (1-4). Formula (1-4) is as follows:

[0111] V G +V Ek ≤0.15f cu，k bh0 (1-4)

[0112] V G is the shear force of the member under the action of gravity load, b is the width of the rectangular cross-section or the web thickness of the T-shaped or I-shaped cross-section, h0 is the distance from the acting point of the resultant force of the longitudinal reinforcement to the compression edge, and f cu,k is the standard value of the compressive strength of the concrete cube with a side length of 150 mm.

[0113] The shear section of the steel-concrete composite structure satisfies the provisions of formula (1-5), where formula (1-5) is as follows:

[0114] V G +V Ek ≤0.15f cu，k bh0 + 0.25f ak A a (1-5)

[0115] b is the width of the rectangular cross-section of the concrete structure or the web thickness of the T-shaped or I-shaped cross-section, h0 is the distance from the acting point of the resultant force of the longitudinal reinforcement to the compression edge, and A a is the cross-sectional area of the steel beam in the steel-concrete composite structure, V Ek is the shear force of the member under the standard value of the seismic action, and f cu,k is the standard value of the compressive strength of the concrete cube with a side length of 150 mm, and f ak is the standard value of the strength of the steel;

[0116] Among them, at the 5th performance level under the action of the E2 earthquake, more ordinary members enter the yield stage. The shear section of the ordinary members satisfies the provisions of formula (1-4) or formula (1-5), allowing some plastic energy-dissipating members to undergo relatively serious damage, and the elastic-plastic displacement of the structure satisfies the maximum elastic-plastic displacement limit of the structure.

[0117] Here, since in the seismic performance-based design method of the present invention, the 2nd performance level has its clear seismic target setting, for example, under the action of the fortification earthquake or the E2 earthquake, there are clear performance expectations for the structural members. Therefore, the design calculation of the reinforced concrete members is given by the 2nd performance level, as follows:

[0118] When the 2nd performance level is under the action of the fortification earthquake or the E2 earthquake, the stress and deformation conditions of the reinforced concrete members need to meet the following standards:

[0119] As Figure 2 shown, when the reinforced concrete member is a flexural member, the calculation of the flexural bearing capacity of its normal section shall comply with the following formula:

[0120]

[0121] M ik is the moment caused by the structure gravity, and M Ehkis the bending moment caused by the lateral seismic action, M Evk is the bending moment caused by the vertical seismic action, x is the equivalent compressive zone height of concrete, f ck is the standard value of the axial compressive strength of concrete, b is the width of the rectangular section or the web thickness of the T-shaped or I-shaped section, h0 is the distance from the resultant force point of the longitudinal reinforcement to the compression edge, f' sk is the standard value of the compressive strength of the longitudinal ordinary reinforcement, A' s is the cross-sectional area of the longitudinal ordinary reinforcement in the compression zone, f' pk is the standard value of the compressive strength of the longitudinal ordinary reinforcement, A' p is the cross-sectional area of the longitudinal prestressed reinforcement in the compression zone, σ' p0 is the stress of the prestressed reinforcement when the concrete stress at the resultant force point of the compression zone prestressed reinforcement is equal to zero, a' s is the distance from the longitudinal ordinary reinforcement in the compression zone to the compression edge, a' p is the distance from the longitudinal prestressed reinforcement in the compression zone to the compression edge.

[0122] Refer to Figure 3 shown, the above-mentioned equivalent compressive zone height x of concrete is calculated according to the following formula:

[0123] f sk A s +f pk A p =f ck bx+f' sk A' s +(f' pk -σ' p0 )A' p (2-2)

[0124] x is the equivalent compressive zone height of concrete, f ck is the standard value of the axial compressive strength of concrete, b is the width of the rectangular section or the web thickness of the T-shaped or I-shaped section, f sk is the standard value of the tensile strength of the longitudinal ordinary reinforcement, A s is the cross-sectional area of the longitudinal ordinary reinforcement in the tension zone, f pk is the standard value of the tensile strength of the longitudinal ordinary reinforcement, A p is the cross-sectional area of the longitudinal prestressed reinforcement in the tension zone, f' sk is the standard value of the compressive strength of the longitudinal ordinary reinforcement, A' s is the cross-sectional area of the longitudinal ordinary reinforcement in the compression zone, f' pk is the standard value of the compressive strength of the longitudinal ordinary reinforcement, A' p is the cross-sectional area of the longitudinal prestressed reinforcement in the compression zone, σ' p0 is the stress of the prestressed reinforcement when the concrete stress at the resultant force point of the compression zone prestressed reinforcement is equal to zero.

[0125] By precisely defining the mathematical relationship between the equivalent compression zone height x of concrete, the material properties of steel bars and concrete, and the geometric parameters of the component cross-section, it provides a core basis for accurately calculating the bearing capacity of reinforced concrete components under different stress states.

[0126] Meanwhile, under this condition, the normal section compressive bearing capacity of the axially compressed member in the above-mentioned reinforced concrete component shall comply with the following formula:

[0127]

[0128] N ik is the axial force of the structure caused by the structural gravity, N Ehk is the axial force of the structure caused by the lateral seismic action, N Evk is the axial force of the structure caused by the vertical seismic action, f ck is the standard value of the axial compressive strength of concrete, A is the gross cross-sectional area of the component, f' sk is the standard value of the compressive strength of longitudinal ordinary steel bars, A' s is the cross-sectional area of all longitudinal ordinary steel bars, is the stability coefficient of the axially compressed member.

[0129] Such as Figure 4 shown, when the reinforced concrete component is a flexural member, the calculation of its shear bearing capacity of the inclined section complies with the provisions of (2-4) to (2-7):

[0130]

[0131] V sbk =0.75×10 -3 f sk ∑A sb sinθ s (2-6)

[0132] V pbk =0.75×10 -3 f pk ∑A pb sinθ s (2-7)

[0133] V csk is the standard value of the shear bearing capacity of concrete and stirrups in the inclined section, V sbk is the standard value of the shear bearing capacity of ordinary bent-up steel bars intersecting the inclined section, V pbk is the standard value of the shear bearing capacity of prestressed bent-up steel bars intersecting the inclined section, V ik is the shear force caused by the structural gravity, V Ekis the shear force caused by seismic action, α1 is the influence coefficient of opposite-sign bending moments, which is taken as 1.0 when calculating the shear bearing capacity of simply supported beams and the near-edge support beam segments of continuous beams, and taken as 0.9 when calculating the shear bearing capacity of the near-middle support beam segments of continuous beams and cantilever beams; α2 is the coefficient of improvement by prestress, which is taken as 1.0 for reinforced concrete flexural members and taken as 1.25 for prestressed concrete flexural members, α3 is the influence coefficient of the compression flange, which is taken as 1.0 for rectangular cross-sections and taken as 1.1 for T-shaped and I-shaped cross-sections; b is the width of the rectangular cross-section or the web thickness of the T-shaped or I-shaped cross-section, h0 is the distance from the resultant force action point of the longitudinal reinforcement to the compression edge, P is the reinforcement ratio of the longitudinal tensile reinforcement in the inclined section, P ≤ 2.5, f cu,k is the standard value of the cubic compressive strength of concrete cubes with a side length of 150 mm, ρ sv is the reinforcement ratio of stirrups in the inclined section, ρ pv is the reinforcement ratio of vertical prestressed reinforcement in the inclined section, f svk is the standard value of the tensile strength of stirrups, f pvk is the standard value of the tensile strength of vertical prestressed reinforcement, f sk is the standard value of the tensile strength of ordinary bent-up bars, A sb is the cross-sectional area of ordinary bent-up bars in the same bent-up plane in the inclined section, θ s is the angle between the tangent of the ordinary bent-up bar and the horizontal line, f pk is the standard value of the tensile strength of prestressed bent-up bars, A pb is the cross-sectional area of prestressed bent-up bars in the same bent-up plane in the inclined section, θ p is the angle between the tangent of the prestressed bent-up bar and the horizontal line.

[0134] At the same time, in this embodiment, for the steel-concrete composite beam, design calculations are carried out according to specific formulas in the positive bending moment section and the negative bending moment section respectively, so as to fully consider the mechanical properties of the steel-concrete composite beam under different stress states, as follows:

[0135] As Figures 5 - 6 shown, in the positive bending moment section, when the plastic neutral axis 1 of the composite section is within the concrete slab, if the condition Af ak ≤ b e h c f ck is satisfied, the compressive bearing capacity of the normal section should be calculated according to the following formula:

[0136]

[0137] x = af ak / b e f ck (3-2)

[0138] Where A, b e 、h care the sectional parameters of the steel-concrete composite beam, M ik , M Ehk , M EVK are the corresponding bending moments, and the steel bar reinforcement and dimensions of the concrete slab and steel beam are determined according to the calculation results. M ik is the bending moment caused by the structural gravity, M Ehk is the bending moment caused by the lateral seismic action, M Evk is the bending moment caused by the vertical seismic action. 0.4 is the combination value coefficient of the vertical seismic action. A 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 section and the resultant force of the concrete compression zone, b e is the effective width of the concrete slab, f ck is the standard value of the axial compressive strength of concrete.

[0139] As Figure 7 shown, when the plastic neutral axis 1 of the composite section is within the concrete slab, if the condition Af ak ≥b e h c f ck is satisfied, the compressive bearing capacity of the normal section should be calculated according to the following formula:

[0140]

[0141] A c =0.5(A - b e h c1 f ck / f ak )(3 - 4).

[0142] b e is the effective width of the concrete slab, h c is the cross-sectional height of the concrete slab, A c is the height of the compression zone of the steel beam section, f ak is the standard value of the tensile strength of the steel beam section, y1 is the distance between the resultant force point of the tension zone of the steel beam and the resultant force point of the concrete compression zone, and y2 is the distance between the resultant force point of the tension zone of the steel beam and the resultant force point of the compression zone of the steel beam.

[0143] As Figures 8 - 9 shown, in the negative bending moment section, when the plastic neutral axis 2 of the steel beam is within the steel-concrete composite beam, its compressive bearing capacity of the normal section should comply with the provisions of formulas (3 - 5) to (3 - 7):

[0144]

[0145] M sk =W npx f ak (3 - 6)

[0146] f sk As +f ak (A - A c ) = f ak A c (3 - 7)

[0147] W npx is the plastic section moment of inertia of the steel beam section, f sk is the standard value of the tensile strength of the steel bar, f ak is the standard value of the tensile strength of the steel beam section, y3 is the distance from the plastic neutral axis of the composite beam to the resultant force point of the steel bars, y4 is the distance from the plastic neutral axis of the composite beam to the plastic neutral axis of the steel beam, A s is the cross - sectional area of the steel bars in the concrete slab, A is the cross - sectional area of the steel beam section, A c is the height of the compression zone of the steel beam section.

[0148] By calculating the steel - concrete composite beam in the positive - moment section and negative - moment section, the bearing capacity of each area under different seismic levels can be accurately evaluated. Considering factors such as the position of the plastic neutral axis of the composite section and material properties, refined design can be achieved. This can not only ensure that the steel - concrete composite beam has sufficient strength and deformation capacity throughout the earthquake process, but also avoid the structural failure caused by the damage of a certain section.

[0149] Finally, in the calculation process, according to the calculation results, the possible weak parts and key parts that need to be strengthened in the bridge structure can be accurately found. For example, under certain performance levels, stress concentration or insufficient bearing capacity may occur in some ordinary components or plastic hinge areas. Then, using finite - element analysis software and inputting seismic waves that meet the site conditions and seismic fortification requirements, the stress, deformation, and failure conditions of the bridge under different seismic levels are comprehensively simulated, and a strict verification analysis of the design is carried out to determine whether it meets the selected seismic performance objectives. If weak links or parts that do not meet the performance requirements are found during the verification process, the design is promptly optimized and adjusted, and then the verification analysis is carried out again. This process is repeated until the structure fully meets the requirements of seismic performance - based design.

[0150] Through the above design process and specific implementation process, the present invention can effectively achieve the seismic performance - based design of highway bridge structures, improving the safety and stability of bridges during earthquakes.

[0151] The above - mentioned specific implementation manners further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above - mentioned are only the specific implementation manners of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A performance-based seismic design method for highway bridge structures, characterized in that The design method is carried out according to the following steps: Step 1: Obtain the basic information of the target bridge, including pier height, structural type, site type, and seismic fortification standard; Step 2: Conduct a seismic performance analysis of the target bridge based on the information obtained in Step 1 to obtain the seismic fortification category and seismic level of the target bridge; Step 3: Select the corresponding seismic performance target from the preset seismic performance target table according to the seismic fortification category and seismic level of the target bridge; Step 4: Analyze and determine the degree and situation of the bridge structure exceeding the irregular bridge defined by the "Code for Seismic Design of Highway Bridges" (JTG / T 2231-01-2020) to determine the site conditions, seismic level, and ground motion parameters; Step 5: According to the selected seismic performance target, through calculation and analysis of bridge structures at different performance levels, demonstrate that the structure can meet the seismic performance requirements. Among them, it includes carrying out bearing capacity design calculations for bridge structures at different performance levels and design calculations for steel-concrete composite beams. According to the calculation results, find out the weak parts and key parts that need to be strengthened in the bridge structure, and then conduct design verification and adjustment on the weak parts and key parts; Among them, 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; Among them, the bearing capacity and deformation of the first performance level meet the elastic design specifications of the current "Code for Seismic Design of Highway Bridges" under the action of E1 earthquake. Under the action of the fortification earthquake, the seismic bearing capacity of the bridge structure shall satisfy the following formula: γ G is the partial coefficient for permanent action, G ik is the standard value of permanent action, R d is the design value of the bearing capacity of the bridge structure, S Ehk is the structural internal force of the standard value of horizontal seismic action, S Evk is the structural internal force of the standard value of vertical seismic action, γ Eh is the partial coefficient of horizontal seismic action, γ Ev is the partial coefficient of vertical seismic action; Under the action of the fortification earthquake or E2 earthquake, the shear resistance of the plastic energy dissipation zone and the seismic resistance of the key components meet the requirements of formula (1-1). Among them, the normal section bearing capacity of the plastic energy dissipation zone satisfies the following formula: G ik is the standard value of permanent action, R k is the standard value of the bearing capacity of the bridge structure section, calculated according to the material standard value, and 0.4 is the combination value coefficient of the vertical seismic action; Under the action of the fortification earthquake or E2 earthquake, the flexural bearing capacity of the key components and ordinary components meets the requirements of formula (1-2), and the flexural bearing capacity of the key components of the long-span bridge structure meets the requirements of formula (1-3). Some plastic hinge regions enter the yield stage, and their shear bearing capacity meets formula (1-2). Among them, formula (1-3) is as follows: 0.4 is the combination value coefficient of the horizontal seismic action; Under the fortification earthquake action or E2 earthquake action, for the fourth performance level, some ordinary components and most plastic hinge regions enter the yielding stage. The shear section of the reinforced concrete structure should meet the provisions of formula (1-4), and formula (1-4) is as follows: V G +V Ek ≤0.15f cu，k bh0 (1 - 4) V G is the shear force of the member under the action of gravity load, b is the width of the rectangular cross-section or the web thickness of the T-shaped or I-shaped cross-section, h0 is the distance from the resultant force action point of the longitudinal reinforcement to the compression edge, f cu,k is the standard value of the compressive strength of the concrete cube with a side length of 150 mm; The shear section of the steel-concrete composite structure meets the provisions of formula (1-5), where formula (1-5) is as follows: V G +V Ek ≤0.15f cu，k bh0 + 0.25f ak A a (1 - 5) b is the width of the rectangular section of the concrete structure or the web thickness of the T-shaped or I-shaped section, h0 is the distance from the resultant force action point of the longitudinal reinforcement to the compression edge, A a is the cross-sectional area of the steel beam in the steel-concrete composite structure, V Ek is the shear force of the component under the standard value of the seismic action, f cu,k is the standard value of the cubic compressive strength of the concrete cube with a side length of 150 mm, f ak is the standard value of the strength of the steel; Under the E2 earthquake action, for the fifth performance level, more ordinary components enter the yielding stage. The shear section of the ordinary components meets the provisions of formula (1-4) or formula (1-5), allowing some plastic energy-dissipating components to have relatively serious damage, and the elastic-plastic displacement of the structure meets the maximum elastic-plastic displacement limit of the structure.

2. A seismic performance-based design method for highway bridge structures according to claim 1, characterized in that Under the fortification earthquake action or E2 earthquake action, for the second performance level, the stress and deformation conditions of the reinforced concrete components need to meet the following standards: When the reinforced concrete component is a flexural member, the calculation of the flexural bearing capacity of its normal section should comply with the following formula: M ik is the bending moment caused by structural gravity, M Ehk is the bending moment caused by lateral seismic action, M Evk is the bending moment caused by vertical seismic action, x is the equivalent compression zone height of concrete, f ck is the standard value of the axial compressive strength of concrete, b is the width of the rectangular section or the web thickness of the T-shaped or I-shaped section, h0 is the distance from the resultant force action point of the longitudinal reinforcement to the compression edge, f' sk is the standard value of the compressive strength of longitudinal ordinary reinforcement, A' s is the cross-sectional area of longitudinal ordinary reinforcement in the compression zone, f' pk is the standard value of the compressive strength of longitudinal ordinary reinforcement, A' p is the cross-sectional area of longitudinal prestressed reinforcement in the compression zone, σ' p0 is the stress of the prestressed reinforcement when the concrete normal stress at the resultant force point of the compression zone prestressed reinforcement is zero, a' s is the distance from the longitudinal ordinary reinforcement in the compression zone to the compression edge, a' p is the distance from the longitudinal prestressed reinforcement in the compression zone to the compression edge.

3. A seismic performance-based design method for highway bridge structures according to claim 2, characterized in that, The equivalent compression zone height x of the concrete is calculated according to the following formula: f sk A s +f pk A p =f ck b x +f′ sk A′ s +(f′ pk -σ′ p0 )A′ p (2-2); x is the equivalent compression zone height of concrete, f ck is the standard value of the axial compressive strength of concrete, b is the width of the rectangular section or the web thickness of the T-shaped or I-shaped section, f sk is the standard value of the tensile strength of longitudinal ordinary reinforcement, A s is the cross-sectional area of longitudinal ordinary reinforcement in the tension zone, f pk is the standard value of the tensile strength of longitudinal ordinary reinforcement, A p is the cross-sectional area of longitudinal prestressed reinforcement in the tension zone, f' sk is the standard value of the compressive strength of longitudinal ordinary reinforcement, A' s is the cross-sectional area of longitudinal ordinary reinforcement in the compression zone, f' pk is the standard value of the compressive strength of longitudinal ordinary reinforcement, A' p is the cross-sectional area of longitudinal prestressed reinforcement in the compression zone, σ' p0 is the stress of the prestressed reinforcement when the concrete normal stress at the resultant force point of the compression zone prestressed reinforcement is equal to zero.

4. A seismic performance-based design method for highway bridge structures according to claim 2, characterized in that The axial compressive bearing capacity of the normal section of the axially compressed member in the reinforced concrete component should comply with the following formula: N ik is the axial force of the structure caused by the structural gravity, N Ehk is the axial force of the structure caused by the lateral seismic action, N Evk is the axial force of the structure caused by the vertical seismic action, f ck is the standard value of the axial compressive strength of concrete, A is the gross cross-sectional area of the member, f' sk is the standard value of the compressive strength of longitudinal ordinary steel bars, A' s is the cross-sectional area of all longitudinal ordinary steel bars is the stability coefficient of the axial compression member 5. A method for seismic performance-based design of highway bridge structures according to claim 2, characterized in that, When the reinforced concrete component is a flexural member, the calculation of its shear resistance of the inclined section complies with the provisions of (2-4) to (2-7): V sbk = 0.75 × 10 -3 f sk ∑A sb sinθ s (2 - 6) V pbk = 0.75 × 10 -3 f pk ∑A pb sinθ p (2 - 7) V csk is the standard value of the shear resistance of concrete and stirrups in the inclined section, V sbk is the standard value of the shear resistance of ordinary bent-up bars intersecting the inclined section, V pbk is the standard value of the shear resistance of prestressed bent-up bars intersecting the inclined section, V ik is the shear force caused by the structural gravity, V Ek is the shear force caused by the seismic action. α1 is the influence coefficient of opposite-sign bending moments. When calculating the shear resistance of simply supported beams and the near-edge support beam segments of continuous beams, take 1.0; when calculating the shear resistance of the near-middle support beam segments of continuous beams and cantilever beams, take 0.9; α2 is the prestress improvement coefficient. For reinforced concrete flexural members, take 1.0; for prestressed concrete flexural members, take 1.

25. α3 is the influence coefficient of the compression flange. For rectangular sections, take 1.0; for T-shaped and I-shaped sections, take 1.1; b is the width of the rectangular section or the web thickness of the T-shaped or I-shaped section, h0 is the distance from the resultant force action point of the longitudinal reinforcement to the compression edge, P is the reinforcement ratio of the longitudinal tensile reinforcement in the inclined section, P ≤ 2.5, f cu,k is the standard value of the cube compressive strength of concrete with a side length of 150 mm, ρ sv is the reinforcement ratio of stirrups in the inclined section, ρ pv is the reinforcement ratio of vertical prestressed reinforcement in the inclined section, f svk is the standard value of the tensile strength of stirrups, f pvk is the standard value of the tensile strength of vertical prestressed reinforcement, f sk is the standard value of the tensile strength of ordinary bent-up bars, A sb is the cross-sectional area of ordinary bent-up bars in the same bent-up plane in the inclined section, θ s is the angle between the tangent of the ordinary bent-up bar and the horizontal line, f pk is the standard value of the tensile strength of prestressed bent-up bars, A pb is the cross-sectional area of prestressed bent-up bars in the same bent-up plane in the inclined section, θ p is the angle between the tangent of the prestressed bent-up bar and the horizontal line.

6. A seismic performance-based design method for highway bridge structures according to claim 1, characterized in that, The design calculation steps of the steel-concrete composite beam include the positive moment section and the negative moment section; Among them, in the positive bending moment section, when the plastic neutral axis (1) of the composite section is within the concrete slab, if the condition Af ak ≤b e h c f ck is satisfied, the compressive bearing capacity of the normal section shall be calculated according to the following formula: x = Af ak / b e f ck (3 - 2) Among them, A, b e , h c are the cross-sectional parameters of the steel-concrete composite beam, M ik , M Ehk , M EVK are the corresponding bending moments, and the steel bar reinforcement and dimensions of the concrete slab and steel beam are determined according to the calculation results. M ik is the bending moment caused by the structural gravity, M Ehk is the bending moment caused by the lateral seismic action, M Evk is the bending moment caused by the vertical seismic action. 0.4 is the combination value coefficient of the vertical seismic action, A 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-section and the resultant force of the concrete compression zone, b e is the effective width of the concrete slab, f ck is the standard value of the axial compressive strength of concrete.

7. A seismic performance-based design method for highway bridge structures according to claim 6, characterized in that , in the positive bending moment section, when the plastic neutral axis (1) of the composite section is within the concrete slab, if the condition Af ak ≥b e h c f ck is satisfied, the compressive bearing capacity of the normal section shall be calculated according to the following formula: A c = 0.5(A - b e h c f ck / f ak ) (3 - 4); b e is the effective width of the concrete slab, h c is the cross-sectional height of the concrete slab, A c is the height of the compression zone of the steel beam cross-section, f ak is the standard value of the tensile strength of the steel beam cross-section, y1 is the distance from the resultant force point of the tensile zone of the steel beam to the resultant force point of the compression zone of the concrete, and y2 is the distance from the resultant force point of the tensile zone of the steel beam to the resultant force point of the compression zone of the steel beam.

8. A seismic performance-based design method for highway bridge structures according to claim 6, characterized in that In the negative moment section, the axial compressive bearing capacity of the normal section of the steel-concrete composite beam should comply with the provisions of formulas (3-5) to (3-7): M sk = W npx fa k (3 - 6) f sk A s +f ak (A - A c ) = f ak A c (3 - 7) W npx is the plastic section modulus of the steel beam cross-section, f sk is the standard value of the tensile strength of the steel bars, f ak is the standard value of the tensile strength of the steel beam cross-section, y3 is the distance from the plastic neutral axis of the composite beam to the resultant force point of the steel bars, y4 is the distance from the plastic neutral axis of the composite beam to the plastic neutral axis of the steel beam, A s is the cross-sectional area of the steel bars in the concrete slab, A is the cross-sectional area of the steel beam, A c is the height of the compression zone of the steel beam cross-section.

9. A seismic performance-based design method for highway bridge structures according to claim 1, characterized in that The design verification and adjustment steps also include the following steps: S51. Perform seismic response analysis on the completed bridge structure using finite element analysis software. During the analysis, input seismic waves that meet the site conditions and seismic fortification requirements to comprehensively simulate the stress, deformation, and failure conditions of the bridge under different seismic levels, so as to verify whether the selected seismic performance objectives are met; S52. If weak links or parts that do not meet the performance requirements are found in the structure during the verification process, optimize and adjust the design. After the adjustment, verification analysis should be carried out again until the structure fully meets the requirements of seismic performance-based design.

Images