Seismic design method of prestressed pipe pile frame for prefabricated assembled pile-slab highway bridge

Abstract

The present invention discloses a seismic design method for a prestressed pipe pile frame of a highway prefabricated assembled pile-slab bridge, and belongs to the technical field of prestressed high-strength concrete pipe piles and highway prefabricated assembled pile-slab bridges. The present invention solves the technical problems of obvious brittle failure characteristics and poor ductility and energy dissipation capacity of the prestressed pipe pile frame of a typical highway prefabricated assembled pile-slab bridge; the pipe pile connection transition section is used as a potential plastic hinge area, and the advantages of large ultimate strain and strong energy dissipation capacity of the longitudinal ordinary steel bar are used to improve the ultimate displacement and energy dissipation capacity of the prestressed pipe pile frame; and through capacity protection design, it is ensured that the damage under earthquake only occurs in the pipe pile connection transition section, avoiding brittle failure of the standard section of the pipe pile, structural shear failure and other failure modes, thereby improving the ductility of the prestressed pipe pile frame; through the provided design steps, the design parameters of the prestressed pipe pile frame can be quickly determined without complex nonlinear earthquake response calculations, significantly improving the design efficiency of the structure.

Description

Technical Field

[0001] The invention relates to the technical field of prestressed high-strength concrete pipe piles and highway prefabricated assembled pile-slab type bridges, and in particular to a seismic design method for a prestressed pipe pile frame of a highway prefabricated assembled pile-slab type bridge. Background Art

[0002] The highway prefabricated pile-slab bridge is a frame-type structural system composed of factory-produced main beams, cap beams and prestressed high-strength concrete pipe piles, and a core-filled connection transition section is set on the pile top to connect the cap beam and the prestressed high-strength concrete pipe piles. The transverse direction of each pier is usually a prestressed pipe pile frame structure, and the pocket connection shown in Figure 1 (d) is used between the cap beam and the pipe pile connection transition section. When the structural components are prefabricated and assembled, a steel tray is set in the hollow part of the top of the prestressed high-strength concrete pipe pile and a connecting structural steel cage (made of ordinary steel bars tied together) is placed to form a pipe pile connection transition section, and then the extended part of the connecting structural steel cage is inserted into the reserved slot of the cap beam, and finally grouting is poured into the hollow part of the pre-embedded connecting structural steel cage on the top of the prestressed high-strength concrete pipe pile and the reserved slot of the cap beam to achieve a rigid connection between the prestressed high-strength concrete pipe pile and the cap beam. Prestressed high-strength concrete pipe piles are prestressed by longitudinally arranged prestressed tendons and are prefabricated by the pre-tensioning method. The prestressed high-strength concrete pipe piles can be divided into two parts: the pipe pile connection transition section and the pipe pile standard section, depending on whether the hollow part is pre-buried with a structural steel cage and grouting.

[0003] For the prestressed pipe pile frame of a typical highway prefabricated assembled pile-slab bridge, the relevant quasi-static test results show that its failure mode is the brittle breakage of the prestressed tendons in the standard section of the pipe pile, and the structural ductility is poor and the energy consumption capacity is insufficient, which is not conducive to the promotion and application in bridge projects in high-intensity areas. In order to improve the ductility of the prestressed pipe pile frame and avoid brittle failure of the standard section of the pipe pile, it is urgent to propose an efficient and safe seismic design method for the prestressed pipe pile frame, which is a technical problem that needs to be solved. To this end, the present invention proposes a seismic design method for the prestressed pipe pile frame of a highway prefabricated assembled pile-slab bridge. Summary of the invention

[0004] The technical problem to be solved by the present invention is how to improve the ductility of the prestressed pipe pile frame and avoid brittle failure of the standard section of the pipe pile, and provides a seismic design method for the prestressed pipe pile frame of a highway prefabricated assembled pile-slab bridge.

[0005] The present invention solves the above technical problems through the following technical solutions, and the present invention comprises the following steps:

[0006] S1: Preliminarily plan the size and reinforcement arrangement of the prestressed pipe pile frame, and arrange the longitudinal and transverse reinforcement of the pipe pile connection transition section according to the ductile seismic design requirements;

[0007] S2: Establish a finite element analysis model of the prestressed pipe pile frame and calculate the ultimate displacement of the prestressed pipe pile frame through static push-down analysis;

[0008] S3: Establish a full-bridge dynamic calculation model of the pile-slab bridge structure in step S1, use an elastic method to solve the displacement of the prestressed pipe pile frame under the design earthquake level, and consider the elastic-plastic effect for correction to obtain the inelastic seismic displacement demand of the structure, that is, the seismic displacement demand of the prestressed pipe pile frame, wherein the pile-slab bridge structure is the pile-slab bridge where the prestressed pipe pile frame is located;

[0009] S4: Compare the ultimate displacement of the prestressed pipe pile frame with the seismic displacement requirement. If the ultimate displacement does not meet the requirement, adjust the reinforcement arrangement of the pipe pile connection transition section until the ultimate displacement meets the requirement.

[0010] S5: Design other parts and components of the prestressed pipe pile frame according to the capacity protection design principle.

[0011] Furthermore, in step S1, the specific process is as follows:

[0012] S11: Based on the static design results of the pile-slab bridge structure, the geometric dimensions and reinforcement arrangement information of the prestressed pipe pile frame are preliminarily determined;

[0013] S12: Check and adjust the longitudinal ordinary steel bars and spiral stirrups in the transition section of the pipe pile connection to meet the relevant structural requirements for ductile seismic design in the current seismic design specifications.

[0014] Furthermore, in step S11, the geometric dimensions and reinforcement arrangement information of the prestressed pipe pile frame include the outer diameter of the cross section of the prestressed high-strength concrete pipe pile. , inner diameter , the number and diameter of longitudinal prestressed tendons of prestressed high-strength concrete piles , layout position and longitudinal reinforcement ratio , the diameter of the spiral stirrups of the pile ,spacing and volumetric stirrup ratio ; Number of longitudinal ordinary steel bars in the core of the transition section of the pipe pile connection ,diameter , layout position and longitudinal reinforcement ratio , the diameter of the spiral stirrups filling the transition section of the pipe pile connection ,spacing and volumetric stirrup ratio ; The equivalent consolidation point position of the prestressed pipe pile frame is taken as the maximum bending moment point of the prestressed high-strength concrete pipe pile below the ground line under the action of lateral force; Among them, the longitudinal prestressed tendons of the prestressed high-strength concrete pipe pile are divided into two parts: the bonded longitudinal prestressed tendons in the standard section of the pipe pile and the unbonded longitudinal prestressed tendons in the transition section of the pipe pile connection.

[0015] Furthermore, in step S12, the relevant structural requirements for ductile seismic design are as follows:

[0016] Longitudinal reinforcement ratio of longitudinal ordinary steel bars in the core filling of the transition section of pipe pile connection Not less than 0.6% and not more than 4%;

[0017] Volumetric stirrup ratio of core-filled spiral stirrups in transition section of pipe pile connection The following specifications must be met:

[0018] ;

[0019] in, is the axial compression ratio of the dead load in the transition section of the pipe pile connection, and They are the standard value of compressive strength of grouting concrete filling the transition section of pipe pile connection and the design value of tensile strength of spiral stirrups filling the transition section of pipe pile connection respectively;

[0020] Spacing of spiral stirrups in the transition section of pipe pile connection Not more than 10cm or 6 times the diameter of the longitudinal ordinary steel bar in the core filling of the transition section of the pipe pile connection .

[0021] Furthermore, in the step S2, the finite element analysis model of the prestressed pipe pile frame includes nodes, elastic beam-column units, rigid arms, displacement-based fiber beam-column units, zero-length units and consolidation constraints, wherein nodes are the basic constituent units in the finite element analysis model, and are used to discretize the continuous prestressed pipe pile frame into a finite number of units; elastic beam-column units are used to simulate the mechanical properties of the cap beam, and assign corresponding cross-sectional properties and material properties according to their geometric dimensions and material types; displacement-based fiber beam-column units are used to simulate the mechanical properties of the pipe pile connection transition section and the pipe pile standard section; zero-length units are used to simulate the bonding-slip mechanical behavior of the longitudinal ordinary steel bars filled in the pipe pile connection transition section in the cap beam; consolidation constraints are set at the equivalent consolidation points of the prestressed pipe pile frame; rigid arms are elastic beam-column units, and their axial stiffness and flexural stiffness are more than 100 times the axial stiffness and flexural stiffness of the prestressed pipe pile frame structural components; and structural components include a cap beam and prestressed high-strength concrete pipe piles.

[0022] Furthermore, in step S2, the limit displacement of the prestressed pipe pile frame It is the lateral displacement of the structure under the limit state, taking the minimum displacement corresponding to the following three situations: the strain of the grouting concrete filling the transition section of the pipe pile connection reaches the ultimate compressive strain; the strain of the longitudinal ordinary steel bars filling the transition section of any pipe pile connection reaches the ultimate tensile strain; the lateral bearing capacity of the structure drops to 80% of its peak value.

[0023] Furthermore, in step S3, the specific process is as follows:

[0024] S31: Establish a full-bridge dynamic calculation model of the pile-slab bridge where the prestressed pipe pile frame is located, and calculate the seismic displacement of the prestressed pipe pile frame using the elastic method;

[0025] S32: Considering the structural elastoplastic effect, the seismic displacement demand calculated by the elastic method is corrected to obtain the seismic displacement demand of the prestressed pipe pile frame.

[0026] Furthermore, in step S32, the specific process is as follows:

[0027] Considering the structural elastoplastic effect, the seismic displacement of the prestressed pipe pile frame calculated by the elastic method Multiply by the correction factor , and the inelastic displacement demand of the structure is obtained , the inelastic displacement demand of the structure Iterate and calculate according to the following formula:

[0028] ;

[0029] ;

[0030] Where T is the vibration period corresponding to the first-order vibration mode in the transverse direction of the pile-slab bridge; is the characteristic period of the response spectrum; is the structural displacement ductility coefficient, which is the structural inelastic displacement demand and yield displacement Ratio: .

[0031] Furthermore, in step S5, the specific process is as follows:

[0032] According to the capacity protection design principle, the bending and shearing capacity of the standard section of the prestressed pipe pile frame, the shearing capacity of the pipe pile connection transition section and the bending and shearing capacity of the cap beam are designed.

[0033] Furthermore, in step S5, the bending resistance of the standard section of the pile Not less than 1.2 times the equivalent yield moment of the transition section of the pipe pile connection, the shear capacity of the standard section of the pipe pile Not less than the prestressed pipe pile frame reaches the limit displacement 1.2 times of the most unfavorable shear force of each pipe pile; the shear resistance of the transition section of the pipe pile connection shall not be less than the ultimate displacement of the prestressed pipe pile frame The design value of the cap beam bending moment acting on the interface between the cap beam and the pipe piles is 1.2 times the equivalent yield moment of the section of the transition section connecting the pipe piles. The design value of the cap beam shear force acting on the interface between the cap beam and the pipe piles is the limit displacement of the prestressed pipe pile frame. The equivalent yield moment of the section of the transition section of the pipe pile connection is calculated by moment curvature analysis. In the moment curvature analysis, the most unfavorable axial force of the section in the plastic hinge area is taken as the maximum displacement of the prestressed pipe pile frame. The most unfavorable axial force of each pipe pile is taken as the plastic hinge area.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] 1. The seismic design method proposed in the present invention solves the technical problems of the obvious brittle failure characteristics and poor ductility and energy dissipation capacity of the prestressed pipe pile frame of the typical prefabricated assembled pile-slab bridge on highway; on the one hand, the pipe pile connection transition section is used as the potential plastic hinge area, and the advantages of the longitudinal ordinary steel bars filled in the pipe pile connection transition section, such as large ultimate strain and strong energy dissipation capacity, are utilized to improve the ultimate displacement and energy dissipation capacity of the prestressed pipe pile frame; on the other hand, through the capacity protection design, it is ensured that the damage under earthquake only occurs in the pipe pile connection transition section, avoiding the brittle failure of the standard section of the pipe pile, the structural shear failure and other failure modes, thereby improving the ductility of the prestressed pipe pile frame.

[0036] 2. The present invention proposes a seismic design method for a prestressed pipe pile frame. By providing design steps, the design parameters of the prestressed pipe pile frame can be quickly determined without complex nonlinear seismic response calculations, thereby significantly improving the design efficiency of the structure.

[0037] 3. The present invention is applicable to prestressed pipe pile frames using different prestressed high-strength concrete pipe pile types and different numbers of prestressed high-strength concrete pipe piles, which is convenient for practical engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 (a) is a schematic diagram of the overall structure of the prestressed pipe pile frame;

[0039] Figure 1 (b) is a schematic diagram of the steel bar structure of the standard section of the pipe pile;

[0040] Figure 1 (c) is a schematic diagram of the steel bar structure of the transition section of the pipe pile connection;

[0041] FIG1 (d) is a schematic diagram of the steel cage structure of the pipe pile connection transition section, the bonded longitudinal prestressed tendons of the pipe pile standard section, and the unbonded longitudinal prestressed tendons of the pipe pile connection transition section;

[0042] Figure 2 Schematic diagram of the flow of the seismic design method in an embodiment of the present invention;

[0043] Figure 3 Schematic diagram of determining the position of the equivalent consolidation point of the prestressed pipe pile frame in an embodiment of the present invention;

[0044] Figure 4 Schematic diagram of a finite element analysis model of a prestressed pipe pile frame in an embodiment of the present invention;

[0045] FIG5( a ) is a schematic diagram of a fiber cross section of a displacement-based fiber beam-column unit of a pipe pile connecting a transition section and a standard section in an embodiment of the present invention;

[0046] FIG5( b ) is a schematic diagram of a fiber cross section of a zero-length unit of the bond-slip mechanical behavior in an embodiment of the present invention;

[0047] Figure 6 Schematic diagram of the compressive stress-strain constitutive model of concrete in an embodiment of the present invention;

[0048] Figure 7 Schematic diagram of the stress-strain constitutive model of steel bars in an embodiment of the present invention;

[0049] Figure 8 Schematic diagram of the stress-slip constitutive model of steel bars in an embodiment of the present invention;

[0050] Fig. 9 is a static push-down curve of the prestressed pipe pile frame in an embodiment of the present invention;

[0051] Fig.10 Schematic diagram of effectiveness verification of the numerical model of the prestressed pipe pile frame in the embodiment of the present invention;

[0052] FIG. 11 ( a ) is a schematic diagram of a linear elastic bar system unit model of a full bridge in an embodiment of the present invention;

[0053] FIG11( b ) is a schematic diagram of a calculation-linked bridge model in an embodiment of the present invention;

[0054] FIG. 12 ( a ) is a three-dimensional view of the first-order vibration mode in the transverse direction of the pile-slab type bridge according to an embodiment of the present invention;

[0055] FIG12( b ) is a top view of the first-order vibration in the transverse direction of the pile-slab type bridge according to an embodiment of the present invention;

[0056] FIG12( c ) is a side view of the first-order vibration mode of the pile-slab type bridge in the transverse direction of the bridge according to an embodiment of the present invention;

[0057] Fig.13 It is a schematic diagram of the cap beam design and calculation of the design example in the embodiment of the present invention;

[0058] Fig.14 is the earthquake acceleration response spectrum at the bridge site of the design example in the embodiment of the present invention;

[0059] FIG15( a ) is a schematic diagram of a fiber cross section for moment curvature analysis of a standard section of a pipe pile according to an embodiment of the present invention;

[0060] FIG. 15( b ) is a schematic diagram of a fiber cross section for moment curvature analysis of a transition section of a pipe pile connection in an embodiment of the present invention.

[0061] In the figure: 1. Cap beam; 2. Prestressed high-strength concrete pipe pile; 3. Pipe pile connection transition section; 4. Pipe pile standard section; 5. Pipe pile connection transition section core filling grouting concrete; 6. Steel tray; 7. Prestressed pipe pile frame equivalent consolidation point; 8. Cap beam-pipe pile connection node; 9. Pipe pile standard section with bonded longitudinal prestressed tendons; 10. Pipe pile spiral stirrups; 11. Pipe pile connection transition section without bonded longitudinal prestressed tendons; 12. Pipe pile connection transition section core filling; 13. Pipe pile connection transition section core filling longitudinal ordinary steel bars; 14 , spiral stirrups filled with core in the transition section of pipe pile connection; 15, nodes; 16, elastic beam-column unit; 17, rigid arm; 18, displacement-based fiber beam-column unit; 19, zero-length unit; 20, consolidation constraint; 21, concrete fiber; 22, bonded longitudinal prestressed fiber in the standard section of pipe pile; 23, ordinary steel fiber; 24, static push-down curve; 25, calculated joint bridge; 26, boundary joint bridge; 27, soil spring; 28, main beam; 29, slide plate support; 30, middle pier; 31, joint end side pier. DETAILED DESCRIPTION

[0062] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0063] Embodiment 1

[0064] This embodiment provides a seismic resistance system of a prestressed pipe pile frame of a highway prefabricated assembled pile-slab bridge, which is applied to the prestressed pipe pile frame of a highway prefabricated assembled pile-slab bridge. Taking a three-column frame as an example, the relevant structure of the prestressed pipe pile frame is shown in Figure 1 (a)-Figure 1 (d), including: a cap beam 1, a prestressed high-strength concrete pipe pile 2, a pipe pile connection transition section 3, a pipe pile standard section 4, a pipe pile connection transition section core filling grouting concrete 5, a steel tray 6, a prestressed pipe pile frame equivalent consolidation point 7, a cap beam-pipe pile connection node 8, a pipe pile standard section bonded longitudinal prestressed tendons 9, a pipe pile spiral stirrup 10, a pipe pile connection transition section non-bonded longitudinal prestressed tendons 11, a pipe pile connection transition section core filling 12, a pipe pile connection transition section core filling longitudinal ordinary steel bar 13, and a pipe pile connection transition section core filling spiral stirrup 14. Under the action of earthquake, the prestressed pipe pile frame seismic system provided in this embodiment uses the pipe pile connection transition section as a potential plastic hinge area, and uses its elastic-plastic deformation to dissipate seismic energy, extend the structural period, and resist earthquake action; the remaining parts and components such as the cap beam, the pipe pile standard section, the cap beam-pipe pile connection node, etc. are reinforced according to the capacity protection design principle to ensure that the parts and components other than the pipe pile connection transition section are basically in the elastic range. In order to realize the above-mentioned seismic system and ensure that the pipe pile connection transition section is destroyed before the pipe pile standard section, the longitudinal prestressed tendons of the pipe pile connection transition section are subjected to the non-bonding treatment (tape wrapping or casing and other measures) as shown in Figure 1 (d) to avoid participating in the stress of the cross section of the pipe pile connection transition section, so as to reduce the equivalent yield bending moment of the cross section of the pipe pile connection transition section.

[0065] Embodiment 2

[0066] Based on the prestressed pipe pile frame seismic system provided in the first embodiment, this embodiment provides a seismic design method for a prestressed pipe pile frame, such as Figure 2 As shown, the method comprises the following steps:

[0067] Step S1: preliminarily plan the size and reinforcement arrangement of the prestressed pipe pile frame, and arrange the longitudinal reinforcement and transverse reinforcement of the pipe pile connection transition section according to the ductile seismic design requirements;

[0068] Step S11: Based on the static design results of the pile-slab bridge structure, the geometric dimensions and reinforcement arrangement of the prestressed pipe pile frame are preliminarily determined, including: the geometric dimensions of the cap beam; the outer diameter of the prestressed high-strength concrete pipe pile section; , inner diameter , the number and diameter of the longitudinal prestressed tendons of prestressed high-strength concrete pipe piles (including the bonded longitudinal prestressed tendons in the standard section of the pipe piles and the unbonded longitudinal prestressed tendons in the transition section of the pipe piles, the reinforcement arrangement of the two is exactly the same) , layout position and longitudinal reinforcement ratio , the diameter of the spiral stirrups of the pile ,spacing and volumetric stirrup ratio ; Number of longitudinal ordinary steel bars in the core of the transition section of the pipe pile connection ,diameter , layout position and longitudinal reinforcement ratio , the diameter of the spiral stirrups filling the transition section of the pipe pile connection ,spacing and volumetric stirrup ratio The longitudinal prestressed tendons of prestressed high-strength concrete pipe piles can be divided into two parts: the longitudinal prestressed tendons with bonding in the standard section of the pipe pile and the longitudinal prestressed tendons without bonding in the transition section of the pipe pile. When the prestressed high-strength concrete pipe piles are produced in factories, the longitudinal prestressed tendons of any prestressed high-strength concrete pipe piles are subjected to non-bonding treatment (tape wrapping or casing and other measures) in the corresponding transition section of the pipe pile connection to avoid bonding with the pile body concrete in the transition section of the pipe pile connection and participating in the stress of the cross section of the transition section of the pipe pile connection, so as to reduce the equivalent yield moment of the cross section of the transition section of the pipe pile connection, and realize that the transition section of the pipe pile connection is destroyed before the standard section of the pipe pile.

[0069] in, It is the ratio of the longitudinal common steel bar area of ​​the pipe pile connection transition section to the cross-sectional area of ​​the pipe pile connection transition section:

[0070] ;

[0071] Among them, the physical meaning of each parameter is the same as mentioned above;

[0072] Calculate as follows:

[0073] ;

[0074] in, It is the diameter of the spiral stirrup ring filling the transition section of the pipe pile connection. The physical meanings of other parameters are the same as mentioned above.

[0075] The location of the equivalent consolidation point of the prestressed pipe pile frame can be taken as the maximum bending moment point of the prestressed high-strength concrete pipe pile below the ground line under the action of lateral force, such as Figure 3 shown.

[0076] Step S12: Check and adjust the longitudinal ordinary steel bars and spiral stirrups in the core of the pipe pile connection transition section to meet the relevant structural requirements for ductile seismic design in the current seismic design code. It should not be less than 0.6% and should not exceed 4%; the volume ratio of the spiral stirrups in the transition section of the pipe pile connection should be The following specifications should be met:

[0077] ;

[0078] in, is the axial compression ratio of the dead load in the transition section of the pipe pile connection, and They are the standard value of compressive strength of grouting concrete filling the transition section of pipe pile connection and the design value of tensile strength of spiral stirrups filling the transition section of pipe pile connection respectively;

[0079] Spacing of spiral stirrups in the transition section of pipe pile connection It should not be larger than 10cm or 6 times the diameter of the longitudinal ordinary steel bar in the core filling of the transition section of the pipe pile connection. .

[0080] Step S2: Calculate the ultimate displacement (displacement capacity) of the prestressed pipe pile frame through static pushover analysis;

[0081] The finite element analysis model of the prestressed pipe pile frame was established, and static pushover analysis was performed. The ultimate displacement of the structure is the lateral displacement corresponding to the structure under the limit state, taking the minimum displacement corresponding to the following three cases: the strain of the grouting concrete filling the transition section of the pipe pile connection reaches the ultimate compressive strain; the strain of the longitudinal ordinary steel bars filling the transition section of any pipe pile connection reaches the ultimate tensile strain; the lateral bearing capacity of the structure drops to 80% of its peak value.

[0082] Among them, the finite element analysis model of the prestressed pipe pile frame is as follows: Figure 4 As shown in FIG5(a), it includes: nodes 15, elastic beam-column units 16, rigid arms 17, displacement-based fiber beam-column units 18, zero-length units 19, and consolidation constraints 20. The elastic beam-column unit 16 is used to simulate the mechanical properties of the cap beam, and the corresponding section properties and material properties are assigned according to its geometric size and material type. The displacement-based fiber beam-column unit 18 is used to simulate the mechanical properties of the pipe pile connection transition section and the pipe pile standard section. Its fiber cross section is shown in FIG5(a), including: concrete fiber 21, bonded longitudinal prestressed tendon fiber 22 of the pipe pile standard section, and ordinary steel fiber 23. The zero-length unit 19 is used to simulate the bond-slip mechanical behavior of the longitudinal ordinary steel bar 13 in the core of the pipe pile connection transition section in the cap beam. Its fiber cross section is shown in FIG5(b), including: concrete fiber 21 and ordinary steel fiber 23. The consolidation constraint 20 is set at the equivalent consolidation point of the prestressed pipe pile frame.

[0083] Among them, for the standard section of the pile, the compressive stress-strain relationship of the concrete fiber in the pile body is based on the Kent-Scott-Park concrete constitutive model ( Figure 6 ) is used for simulation, and the contribution of concrete tensile strength is not considered; the material stress-strain relationship of the standard section of pipe pile with bonded longitudinal prestressed tendon fibers is based on the Giuffre-Menegotto-Pinto steel constitutive model ( Figure 7) is simulated, and the initial tensile stress of the bonded longitudinal prestressed tendons in the standard section of the pipe pile is simulated by setting the initial tensile stress of the bonded longitudinal prestressed tendons in the standard section of the pipe pile. For the section of the transition section of the pipe pile connection, the compressive stress-strain relationship of the concrete fiber is simulated using the Kent-Scott-Park concrete constitutive model; the material stress-strain relationship of the ordinary steel fiber is simulated using the Giuffre-Menegotto-Pinto steel constitutive model. For the fiber section of the zero-length unit simulating the bond-slip mechanical behavior (Figure 5 (b)), the compressive stress-strain relationship of the concrete fiber is simulated using Figure 6 The Kent-Scott-Park concrete constitutive model shown in Figure 1 is used for simulation, and the contribution of concrete tensile strength is not considered; the constitutive relationship of ordinary steel fiber is adopted Figure 7 The Zhao-Sritharan stress-slip constitutive model shown in Figure 3 is used for simulation.

[0084] in, Figure 6 The main parameters of the Kent-Scott-Park concrete constitutive model shown include the concrete compressive strength (peak stress) , compressive strain corresponding to peak stress of concrete (0.002 is acceptable), ultimate compressive strain of concrete The compressive stress corresponding to the ultimate compressive strain of concrete (0.2 is acceptable ). and Calculate according to the following formula:

[0085] Concrete compressive strength (peak stress) :

[0086] ;

[0087] Ultimate compressive strain of concrete :

[0088] ;

[0089] ;

[0090] in, is the compressive strength of plain concrete cylinder; To constrain the strength increase factor of concrete relative to plain concrete, for plain concrete =1; is the volume ratio of spiral stirrups, for plain concrete ; is the yield strength of spiral stirrups; for Figure 6The slope of the descending section of the stress-strain curve of the concrete constitutive model; is the width of the concrete core area confined by stirrups; is the stirrup spacing.

[0091] in, Figure 7 The main parameters of the Giuffre-Menegotto-Pinto steel bar constitutive model shown include the yield stress of the steel bar , yield strain , Ultimate Stress and ultimate strain In the standard section of the pipe pile, the stress of the bonded longitudinal prestressed tendon fibers and ordinary steel fiber drops to 0 after reaching the ultimate strain for the first time, and then they no longer participate in the cross-sectional stress.

[0092] in, Figure 8 The main parameters of the Zhao-Sritharan stress-slip constitutive model shown include the yield stress of the steel bar , Ultimate Stress And the corresponding slip amount at the yield stress and ultimate stress of the steel bar and , calculated as follows:

[0093] ;

[0094] ;

[0095] in, The diameter of the longitudinal common steel bar in the transition section of the pipe pile connection. is the yield stress of the longitudinal ordinary steel bars in the core filling of the transition section of the pipe pile connection, is the compressive strength of the core grouting concrete in the transition section of the pipe pile connection. =0.4 is the model parameter.

[0096] Among them, the static push-down curve of the prestressed pipe pile frame is as follows: Fig. 9 As shown, the horizontal coordinate △ is the horizontal displacement in the transverse direction of the bridge loaded during the static push-down analysis of the prestressed pipe pile frame; the vertical coordinate F is the lateral force in the transverse direction of the bridge of the prestressed pipe pile frame during the static push-down analysis, and its size is related to △. Fig. 9 The key parameters include: static push-down curve 24, yield displacement (lateral displacement of the structure corresponding to the first yield of the steel bars in the transition section of the pipe pile connection) and the ultimate displacement The hysteresis curves obtained by the quasi-static test loading and numerical simulation loading of the pipe pile frame are as follows Fig.10 As shown, the comparison results in the figure show that the nonlinear finite element analysis model has higher accuracy.

[0097] Step S3: Calculate the seismic displacement demand of the prestressed pipe pile frame;

[0098] A full-bridge dynamic calculation model of the pile-slab bridge structure (i.e., the pile-slab bridge where the prestressed pipe pile frame is located) described in step S11 is established, and the displacement of the prestressed pipe pile frame under the design earthquake level is solved by the elastic method, and the elastic-plastic effect is considered for correction to obtain the inelastic earthquake displacement demand of the structure. The specific steps are as follows:

[0099] Step S31: establishing a full-bridge dynamic calculation model of the pile-slab bridge where the prestressed pipe pile frame is located, and calculating the seismic displacement of the prestressed pipe pile frame according to the elastic method;

[0100] According to the size information and material information of the pile-slab bridge structure described in step S11, considering the interaction of piles and soil and the influence of the boundary bridge 26 on the calculation bridge 25, a linear elastic bar system unit model of the whole bridge is established, as shown in Figure 11 (a), including: the calculation bridge 25, the boundary bridge 26, and the soil spring 27. The linear elastic bar system unit model of the calculation bridge 25 is shown in Figure 11 (b), including: the main beam 28, the cap beam 1, the prestressed high-strength concrete pipe pile 2, the soil spring 27, the slide plate support 29, the middle pier 30, the end pier 31, and the rigid arm 17. In the model, the main beam, the cap beam, and the prestressed high-strength concrete pipe pile are all simulated by beam units, and the corresponding cross-sectional properties and material properties are assigned. At the middle pier, rigid arms are used between the cap beam and the prestressed high-strength concrete pipe pile, and between the main beam and the cap beam; at the end pier, the sliding effect of the slide plate support between the main beam and the cap beam is not considered, and the longitudinal and transverse translation constraints are released. The pile-soil interaction is simulated by soil springs, and the soil spring stiffness is Calculated as follows:

[0101] ;

[0102] Where a is the thickness of the soil layer; is the calculated width of the pile. For specific calculation methods, please refer to the "Design Specifications for Highway Bridge and Culvert Foundations and Foundations"; It is a coefficient determined by the elastic properties of the soil, and can refer to the design geological survey data; is the depth of the soil layer. The modeling method of the linear elastic bar unit model of the boundary bridge 26 is the same as that of the calculation bridge.

[0103] The horizontal displacement of the prestressed pipe pile frame in the transverse direction of the bridge is calculated using the multi-mode response spectrum method. , and solve the vibration period T corresponding to the first-order vibration mode in the transverse direction of the pile-slab bridge. Among them, the first-order vibration mode in the transverse direction is the transverse bending vibration of each pier pipe pile frame driven by the main beam, as shown in Figure 12 (a)-Figure 12 (c);

[0104] Step S32: Considering the structural elastoplastic effect, the seismic displacement demand calculated by the elastic method is corrected to obtain the seismic displacement demand of the prestressed pipe pile frame;

[0105] Considering the structural elastoplastic effect, the earthquake displacement calculated by the elastic method Should be multiplied by the correction factor , structural inelastic displacement demand It can be calculated iteratively as follows:

[0106] ;

[0107] ;

[0108] Where T is the vibration period corresponding to the first-order vibration mode in the transverse direction of the pile-slab bridge; is the characteristic period of the response spectrum, which can be obtained according to relevant seismic codes; is the structural displacement ductility coefficient, which is the ratio of the structural seismic displacement demand to the yield displacement .

[0109] Step S4: Compare the displacement capacity (ultimate displacement) and displacement requirement of the prestressed pipe pile frame. If the displacement capacity does not meet the requirement, adjust the reinforcement arrangement of the pipe pile connection transition section until the ultimate displacement meets the requirement.

[0110] Comparison of the ultimate displacement of prestressed pipe pile frame and structural inelastic displacement demand .like , under the earthquake protection level, the prestressed pipe pile frame adopts the initial geometric dimensions and reinforcement to meet the design requirements, and there is no need to adjust the reinforcement layout; if , the initial geometric dimensions and reinforcement of the prestressed pipe pile frame do not meet the design requirements under the earthquake protection level. It is necessary to increase the longitudinal reinforcement ratio of the ordinary steel bars in the transition section of the pipe pile connection, and repeat steps S1 to S4 until .

[0111] Step S5, designing other parts and components of the prestressed pipe pile frame according to the capacity protection design principle;

[0112] According to the principle of capacity protection design, the bending and shearing capacity of the standard section of the prestressed pile frame, the shearing capacity of the transition section of the pile connection, and the bending and shearing capacity of the cap beam are designed to ensure that the parts and components other than the transition section of the pile connection are basically within the elastic response range. Specifically, the bending capacity of the standard section of the pile Not less than 1.2 times the equivalent yield moment of the transition section of the pipe pile connection, the shear capacity of the standard section of the pipe pile Not less than the prestressed pipe pile frame reaches the limit displacement 1.2 times of the most unfavorable shear force of each pipe pile; the shear resistance of the transition section of the pipe pile connection shall not be less than the ultimate displacement of the prestressed pipe pile frame 1.2 times the most unfavorable shear force of each pile; the design value of the bending moment acting on the cap beam It is 1.2 times the equivalent yield moment of the transition section of the pipe pile connection, and the design value of the shear force acting on the cap beam The prestressed pipe pile frame reaches the limit displacement 1.2 times the most unfavorable axial force of each pile ( Fig.13 ).in, , The action position is the center of the interface between the cap beam and the prestressed high-strength concrete pile on the left side of Figure 1 (a); , The action position is the center of the interface between the cap beam and the prestressed high-strength concrete pile in the middle of Figure 1 (a); , The position of action is the center of the interface between the cap beam and the prestressed high-strength concrete pile on the right side of Figure 1 (a). The cap beam bending moment design value, shear force design value and permanent effect determined according to the capacity protection design principle must meet the requirements of relevant specifications. The equivalent yield moment of the section of the transition section of the pile connection is calculated by moment curvature analysis. In the moment curvature analysis, the most unfavorable axial force of the section in the plastic hinge area is taken as the maximum displacement of the prestressed pile frame. The most unfavorable axial force of each pipe pile.

[0113] Under the action of earthquake, the transition section of the pipe pile connection is used as a potential plastic hinge area, and its elastic-plastic deformation is used to dissipate the earthquake energy; the remaining parts and components basically remain elastic.

[0114] Embodiment 3

[0115] The following describes the operation steps in Embodiment 2 in combination with a design example:

[0116] Step S1, preliminarily planning the size and reinforcement arrangement of a prestressed pipe pile frame, and arranging the longitudinal reinforcement and transverse stirrups of the pipe pile connection transition section according to the ductile seismic design requirements;

[0117] Step S11:

[0118] The geometric dimensions of a three-column prestressed pipe pile frame cap beam determined by the static design results are 1.65m (height) × 1.5m (width) × 12.75m (length), and the outer diameter and inner diameter of the prestressed high-strength concrete pipe pile are 1m and 0.74m respectively. 32 prestressed high-strength concrete pipe piles are arranged longitudinally with a diameter of ( ) is 14mm (including the bonded longitudinal prestressed tendons in the standard section of the pile and the unbonded longitudinal prestressed tendons in the transition section of the pile connection. The reinforcement arrangement of the two is exactly the same), the radius of the longitudinal reinforcement distribution circle is 0.44m, and the longitudinal reinforcement ratio is ( ) is 0.63%, the initial tensile stress of the bonded longitudinal prestressed tendons in the standard section of the pipe pile is 600MPa, and the diameter of the spiral stirrup of the pipe pile is ( ) is 8mm, spacing ( ) is 45mm, volume stirrup ratio ( ) is 0.51%; 20 diameter ( ) is 18mm ordinary steel bar, the radius of the longitudinal reinforcement distribution circle is 0.35m, the longitudinal reinforcement ratio is ( ) is 0.65%, the diameter of the spiral stirrups filling the transition section of the pipe pile connection is ( ) is 10mm, spacing ( ) is 45mm, volume stirrup ratio ( ) is 0.97%. The height from the bottom of the cap beam to the equivalent consolidation point of the prestressed pipe pile frame (the maximum bending moment point below the ground line) is 17m.

[0119] The pile body concrete, longitudinal prestressed tendons and spiral stirrups of the prestressed high-strength concrete pipe piles are made of C80 concrete, HG1420 prestressed tendons and CDW550 spiral stirrups respectively. The grouting concrete, ordinary steel bars and spiral stirrups of the core filling of the pipe pile connection transition section are made of C50 concrete, HRB400 longitudinal bars and HPB300 spiral stirrups. The material properties can be determined according to the material type and the recommendations of the relevant specifications.

[0120] Step S12:

[0121] (1) Longitudinal reinforcement ratio of longitudinal ordinary steel bars in the core filling of the transition section of the pipe pile connection The calculation results are as follows:

[0122] 0.6%< =0.65%<4%;

[0123] Meet design requirements;

[0124] (2) Constant load axial pressure ratio of the transition section of the pipe pile connection 10%, standard value of compressive strength of core grouting concrete in transition section of pipe pile connection The tensile strength design value of the spiral stirrups in the transition section of the pipe pile connection is 32.4MPa. 250MPa, longitudinal reinforcement ratio of ordinary steel bars in the core filling of the transition section of the pipe pile connection The spacing of spiral stirrups in the transition section of the pipe pile connection is 45mm (≤6 ), meeting the design requirements. Volumetric stirrup ratio of the core-filled spiral stirrups in the transition section of the pipe pile connection The calculation results are as follows:

[0125] Minimum volume stirrup ratio

[0126] ;

[0127] Meet design requirements;

[0128] Step S2, calculating the ultimate displacement (displacement capacity) of the prestressed pipe pile frame through static pushover analysis.

[0129] Using the geometric dimensions and material information in step S11, a finite element analysis model of the prestressed frame is established and a static push-down analysis is performed to obtain the yield displacement of the prestressed pipe pile frame. 23mm and the limit displacement 403mm (the strain of ordinary steel bars in the core-filling section of the transition section of the pipe pile connection reaches the ultimate tensile strain);

[0130] Step S3, calculating the seismic displacement demand of the prestressed pipe pile frame;

[0131] Step S31:

[0132] The full bridge model of the pile-slab bridge with three-column prestressed pipe pile frame is established. The bridge site category is Class II and the response spectrum characteristic period is The acceleration response spectrum of the 5% damping ratio earthquake motion calculated according to the current specification is 0.35s, the basic earthquake peak acceleration is 0.3g, and the bridge seismic importance factor is 1.3. like Fig.14 As shown, the horizontal axis T s is the period of the pile-slab bridge; is the seismic acceleration of the pile-slab bridge under the given bridge site category, response spectrum characteristic period, basic seismic peak acceleration and bridge seismic importance factor, and T s The seismic displacement of the prestressed pipe pile frame is calculated by the multi-mode response spectrum method (elastic method). It is 0.152m, and the vibration period corresponding to the first-order vibration mode of the pile-slab bridge in the transverse direction is T=1.62s.

[0133] Step S32:

[0134] Considering the structural elastoplastic effect, the earthquake displacement calculated by the elastic method Should be multiplied by the correction factor Get the seismic displacement demand of the prestressed pipe pile frame . Through iterative calculation, we can get: , ;

[0135] Step S4, comparing the ultimate displacement of the prestressed pipe pile frame with the seismic displacement requirement, if the ultimate displacement does not meet the requirement, adjusting the reinforcement arrangement of the pipe pile connection transition section until the ultimate displacement meets the requirement;

[0136] Depend on It can be seen that under the earthquake protection level, the prestressed pipe pile frame adopts the initial geometric dimensions and reinforcement to meet the design requirements, and there is no need for reinforcement arrangement in the transition section of the pipe pile connection.

[0137] Step S5, designing other parts and components of the prestressed pipe pile frame according to the capacity protection design principle;

[0138] (1) Design and calculation of bending and shear resistance of standard section of pipe pile

[0139] ①Bending design check

[0140] Bending requirements of standard section of pipe piles It is 1.2 times the equivalent yield moment of the transition section of the pile connection. The bending capacity of the standard section of the pile is is the equivalent yield moment of the standard section of the pile, and both are obtained through section bending moment curvature analysis.

[0141] The cross section of the standard section of the pipe pile and the cross section of the transition section of the pipe pile connection are discretized into fiber cross sections composed of concrete fibers and steel fibers, as shown in Figure 15 (a) and Figure 15 (b), respectively, including: concrete fiber 21, standard section of the pipe pile with bonded longitudinal prestressed tendon fibers 22 and ordinary steel fibers 23. When solving its bending moment curvature curve, the basic assumptions are as follows: ① The cross section remains flat before and after deformation, that is, the strain increment of the standard section of the pipe pile with bonded longitudinal prestressed tendon fibers and ordinary steel fibers and the strain increment of the concrete fiber satisfy the flat section assumption; ② The tensile strength contribution of concrete is ignored; ③ The compressive stress-strain relationship of concrete fibers is simulated using the Kent-Scott-Park concrete constitutive model ( Figure 7 The stress-strain relationship of the standard section of pipe pile with bonded longitudinal prestressed tendon fibers and ordinary steel fibers is simulated using the Giuffre-Menegotto-Pinto steel constitutive model ( Figure 8 ). In the moment curvature analysis, the most unfavorable axial force of the section is taken when the prestressed pipe pile frame reaches the limit displacement The design calculation results of the bending capacity of the standard section of the pipe piles of the above three-column prestressed pipe pile frame are shown in Table 1, which shows that the bending capacity of the standard section of each pipe pile meets the capacity protection design requirements.

[0142] Table 1 Design and calculation of bending resistance of standard section of pipe pile

[0143]

[0144] ② Shear design check

[0145] Shear resistance requirements of standard pipe pile sections The prestressed pipe pile frame can reach the limit displacement The shear resistance of the standard section of the pile is 1.2 times the most unfavorable shear force of each pile. According to the current concrete specifications, the following formula is used for calculation:

[0146] ;

[0147] in, is the shear span ratio of the pipe pile, which is half the height from the bottom of the cap beam to the equivalent consolidation point of the prestressed pipe pile frame; To meet the shear requirements of the standard section of the pile The corresponding axial pressure design value is greater than When , is the cross-sectional area of ​​the prestressed high-strength concrete pile; and They are the design values ​​of axial compressive strength and tensile strength of the concrete of the prestressed high-strength concrete pipe pile. is the design value of tensile strength of spiral stirrups of pipe piles; is the cross-sectional area of ​​the spiral stirrups of the pipe pile; is the spacing of spiral stirrups of pipe piles; The cross-sectional width of the standard section of the pile is 0.88 times the outer diameter of the prestressed high-strength concrete pile; is the effective height of the prestressed high-strength concrete pile section, which is 0.8 times the outer diameter of the prestressed high-strength concrete pile. The design check results of the shear capacity of the standard section of the three-column frame pile are shown in Table 2, indicating that the shear capacity of each standard section of the pile meets the capacity protection design requirements.

[0148] Table 2 Design and calculation of shear capacity of standard section of pipe pile

[0149]

[0150] (2) Design and calculation of shear capacity of transition section of pipe pile connection

[0151] Shear resistance requirements of pipe pile connection transition section The prestressed pipe pile frame can reach the limit displacement The shear resistance of the transition section of the pile connection is 1.2 times the most unfavorable shear force of each pile. According to the current bridge seismic code, calculate as follows:

[0152] ;

[0153] ;

[0154] ;

[0155] ;

[0156] ;

[0157] in, Contribution to the shear capacity of concrete in the plastic hinge area (pipe pile connection transition section); Contribution to the shear resistance of the core-filled spiral stirrups in the transition section of the pipe pile connection; It is the design value of compressive strength of the core-filled grouting concrete in the transition section of the pipe pile connection; Cross-sectional area of ​​the transition section of the pipe pile connection; is the core concrete area, which can be taken as 0.8 ; is the displacement ductility coefficient of the pier member, which is approximately 6.0 according to the specification; is the pile axial force; , and are the cross-sectional area, spacing and tensile strength design values ​​of the core-filled spiral stirrups in the transition section of the pipe pile connection, respectively; D is the diameter of the core-filled spiral stirrup ring in the transition section of the pipe pile connection. The design check results of the shear capacity of the transition section of the pipe pile connection of the three-column prestressed pipe pile frame are shown in Table 3, indicating that the shear capacity of each pipe pile connection transition section meets the capacity protection design requirements.

[0158] Table 3 Design and calculation of shear capacity of transition section of pipe pile connection

[0159]

[0160] (3) Cap beam bending and shear capacity design: According to the capacity protection design principle, the design value of the cap beam bending moment acting on the center of the interface between the cap beam and the tension side pipe piles, the middle pipe piles and the compression side pipe piles under earthquake is They are 1.2 times of the equivalent yield moment of the core filling section of the transition section between the tension side pipe pile, the middle pipe pile and the compression side pipe pile. The design value of the shear force of the cap beam acting on the center of the interface between the cap beam and the tension side pipe pile, the middle pipe pile and the compression side pipe pile under earthquake The prestressed pipe pile frame reaches the limit displacement 1.2 times the most unfavorable axial force of each pile ( Fig.13), after combining the above-mentioned cap beam bending moment design value, shear force design value and permanent effect determined based on capacity protection design, the normal section bending strength and inclined section shear strength are calculated in accordance with the current "Highway Reinforced Concrete and Prestressed Concrete Bridge and Culvert Design Code", and the standard value of material strength can be used in the calculation of bending capacity.

[0161] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A seismic design method for prestressed pipe pile frames of prefabricated assembled pile-slab type highway bridges, characterized in that: The following steps are involved: S1: Preliminarily plan the size and reinforcement arrangement of the prestressed pipe pile frame, and arrange the longitudinal and transverse reinforcement of the pipe pile connection transition section according to the ductile seismic design requirements; S2: Establish a finite element analysis model of the prestressed pipe pile frame and calculate the ultimate displacement of the prestressed pipe pile frame through static push-down analysis; In step S2, the limit displacement of the prestressed pipe pile frame is the lateral displacement of the structure under the limit state, taking the minimum displacement corresponding to the following three situations: the strain of the grouting concrete filling the transition section of the pipe pile connection reaches the ultimate compressive strain; the strain of the longitudinal ordinary steel bars filling the transition section of any pipe pile connection reaches the ultimate tensile strain; the lateral bearing capacity of the structure drops to 80% of its peak value; S3: Establish a full-bridge dynamic calculation model of the pile-slab bridge structure in step S1, use an elastic method to solve the displacement of the prestressed pipe pile frame under the design earthquake level, and consider the elastic-plastic effect for correction to obtain the inelastic seismic displacement demand of the structure, that is, the seismic displacement demand of the prestressed pipe pile frame, wherein the pile-slab bridge structure is the pile-slab bridge where the prestressed pipe pile frame is located; In step S3, the specific process is as follows: S31: Establish a full-bridge dynamic calculation model of the pile-slab bridge where the prestressed pipe pile frame is located, and calculate the seismic displacement of the prestressed pipe pile frame using the elastic method; S32: Considering the structural elastoplastic effect, the seismic displacement demand calculated by the elastic method is corrected to obtain the seismic displacement demand of the prestressed pipe pile frame; In step S32, the specific process is as follows: Considering the structural elastoplastic effect, the seismic displacement of the prestressed pipe pile frame calculated by the elastic method Multiply by the correction factor , and the inelastic displacement demand of the structure is obtained , structural inelastic displacement demand Iterate and calculate as follows: ； ； in, is the vibration period corresponding to the first-order vibration mode of the pile-slab bridge in the transverse direction; is the characteristic period of the response spectrum; is the structural displacement ductility coefficient, which is the structural inelastic displacement demand and yield displacement Ratio: ; S4: Compare the ultimate displacement of the prestressed pipe pile frame with the seismic displacement requirement. If the ultimate displacement does not meet the requirement, adjust the reinforcement arrangement of the pipe pile connection transition section until the ultimate displacement meets the requirement. S5: Based on the capacity protection design principle, design other parts and components of the prestressed pipe pile frame.

2. The seismic design method for prestressed pipe pile frame of prefabricated assembled pile-slab type highway bridge according to claim 1 is characterized in that: In step S1, the specific process is as follows: S11: Based on the static design results of the pile-slab bridge structure, the geometric dimensions and reinforcement arrangement information of the prestressed pipe pile frame are preliminarily determined; S12: Check and adjust the longitudinal ordinary steel bars and spiral stirrups in the transition section of the pipe pile connection to meet the relevant structural requirements for ductile seismic design in the current seismic design specifications.

3. The seismic design method for prestressed pipe pile frame of prefabricated assembled pile-slab type highway bridge according to claim 2 is characterized in that: In step S11, the geometric dimensions and reinforcement arrangement information of the prestressed pipe pile frame include the outer diameter of the cross section of the prestressed high-strength concrete pipe pile. , inner diameter , the number and diameter of longitudinal prestressed tendons of prestressed high-strength concrete piles , layout position and longitudinal reinforcement ratio , the diameter of the spiral stirrups of the pile ,spacing and volumetric stirrup ratio ; Number of longitudinal ordinary steel bars in the core of the transition section of the pipe pile connection ,diameter , layout position and longitudinal reinforcement ratio , the diameter of the spiral stirrups filling the transition section of the pipe pile connection ,spacing and volumetric stirrup ratio ; The equivalent consolidation point position of the prestressed pipe pile frame is taken as the maximum bending moment point of the prestressed high-strength concrete pipe pile below the ground line under the action of lateral force; Among them, the longitudinal prestressed tendons of the prestressed high-strength concrete pipe pile are divided into two parts: the bonded longitudinal prestressed tendons in the standard section of the pipe pile and the unbonded longitudinal prestressed tendons in the transition section of the pipe pile connection.

4. The seismic design method for prestressed pipe pile frame of prefabricated assembled pile-slab type highway bridge according to claim 3 is characterized in that: In step S12, the relevant structural requirements for ductile seismic design are as follows: Longitudinal reinforcement ratio of longitudinal ordinary steel bars in the core filling of the transition section of pipe pile connection Not less than 0.6% and not more than 4%; Volumetric stirrup ratio of core-filled spiral stirrups in transition section of pipe pile connection The following specifications must be met: ； in, is the axial compression ratio of the dead load in the transition section of the pipe pile connection, and They are the standard value of compressive strength of grouting concrete filling the transition section of pipe pile connection and the design value of tensile strength of spiral stirrups filling the transition section of pipe pile connection respectively; Spacing of spiral stirrups in the transition section of pipe pile connection Not more than 10cm or 6 times the diameter of the longitudinal ordinary steel bar in the core filling of the transition section of the pipe pile connection .

5. The seismic design method for prestressed pipe pile frame of prefabricated assembled pile-slab type highway bridge according to claim 1 is characterized in that: In the step S2, the finite element analysis model of the prestressed pipe pile frame includes nodes, elastic beam-column units, rigid arms, displacement-based fiber beam-column units, zero-length units and consolidation constraints, wherein nodes are the basic constituent units in the finite element analysis model, and are used to discretize the continuous prestressed pipe pile frame into a finite number of units; elastic beam-column units are used to simulate the mechanical properties of the cap beam, and assign corresponding cross-sectional properties and material properties according to their geometric dimensions and material types; displacement-based fiber beam-column units are used to simulate the mechanical properties of the pipe pile connection transition section and the pipe pile standard section; zero-length units are used to simulate the bonding-slip mechanical behavior of the longitudinal ordinary steel bars filled in the pipe pile connection transition section in the cap beam; consolidation constraints are set at the equivalent consolidation points of the prestressed pipe pile frame; rigid arms are elastic beam-column units, and their axial stiffness and flexural stiffness are more than 100 times the axial stiffness and flexural stiffness of the prestressed pipe pile frame structural components; and structural components include cap beams and prestressed high-strength concrete pipe piles.

6. The seismic design method for prestressed pipe pile frame of prefabricated assembled pile-slab type highway bridge according to claim 1 is characterized in that: In step S5, the specific process is as follows: According to the capacity protection design principle, the bending and shearing capacity of the standard section of the prestressed pipe pile frame, the shearing capacity of the pipe pile connection transition section and the bending and shearing capacity of the cap beam are designed.

7. The seismic design method for prestressed pipe pile frame of prefabricated assembled pile-slab type highway bridge according to claim 6 is characterized in that: In step S5, the bending resistance of the standard section of the pile Not less than 1.2 times the equivalent yield moment of the transition section of the pipe pile connection, the shear capacity of the standard section of the pipe pile Not less than the prestressed pipe pile frame reaches the limit displacement 1.2 times of the most unfavorable shear force of each pipe pile; the shear resistance of the transition section of the pipe pile connection shall not be less than the ultimate displacement of the prestressed pipe pile frame The design value of the cap beam bending moment acting on the interface between the cap beam and the pipe piles is 1.2 times the equivalent yield moment of the section of the transition section connecting the pipe piles. The design value of the cap beam shear force acting on the interface between the cap beam and the pipe piles is the limit displacement of the prestressed pipe pile frame. The equivalent yield moment of the section of the transition section of the pipe pile connection is calculated by moment curvature analysis. In the moment curvature analysis, the most unfavorable axial force of the section in the plastic hinge area is taken as the maximum displacement of the prestressed pipe pile frame. The most unfavorable axial force of each pipe pile is taken as the plastic hinge area.

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