Dislocation splicing design method for multi-beam bridge with differential vertical deformation

Abstract

The invention relates to a staggered splicing design method for a multi-beam bridge with different vertical deformation, which comprises the following steps: S1, according to the staggered relationship of an old bridge A, an old bridge B, a new bridge C and a new bridge D in the multi-beam bridge, obtaining the maximum value Dmax of the vertical deformation difference at the moment; s2, the structural forms of the rigid splicing structure A and the rigid splicing structure B are designed preliminarily according to Dmax-(i) = 75% * Dmax; s3, according to the setting in the S2, the maximum value Dmax-(i + 1) of the vertical deformation difference in the section where the flexible splicing structure is located at the moment is obtained; s4, if Dmax-(i + 1) is larger than or equal to 90% * Dmax-(i) and smaller than or equal to 110% * Dmax-(i), preliminary design is completed, and the step S5 is executed; otherwise, returning to the step S3; if L1 cannot be greater than 1 / 2 of min (LA, LC), or L3 cannot be greater than 1 / 2 of min (LB, LD), returning to the step S2; and S5, further checking whether the transverse stress of the multi-beam bridge meets the design requirements or not. Compared with the prior art, the method has the advantages that excessive design redundancy is reduced, accurate deformation control can be achieved, and the method adapts to a variable stiffness structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of reconstruction and widening of small and medium span bridges, in particular to a design method for misaligned splicing of multi-beam bridges with different vertical deformations. BACKGROUND

[0002] Multi-beam bridges are a common type of bridge structure in small and medium span bridges. Due to the requirements of bridge clearance and line alignment, in the process of bridge reconstruction and expansion, the new bridge is often misaligned and spliced with the old bridge to save economic cost, which is a common way.

[0003] To ensure the smoothness of vehicles on the bridge, a certain method is needed to connect the joint between the new and old bridges. One practical way is to cast a concrete wet joint with certain connection stiffness. However, such concrete joints in misaligned bridges can lead to unfavorable transverse stress on the old bridge beam, and even cause cracking of the old bridge deck, which is not conducive to the long-term use of the structure. SUMMARY

[0004] The purpose of the present application is to overcome the defects of the prior art and provide a design method for misaligned splicing of multi-beam bridges with different vertical deformations, which effectively releases structural constraints, reduces excessive design redundancy, realizes precise deformation control, adapts to variable stiffness structures, has wide applicability, simple structure, and reliability.

[0005] The purpose of the present application can be achieved by the following technical solutions: The present application provides a design method for misaligned splicing of multi-beam bridges with different vertical deformations, comprising the following steps: S1: According to the misaligned relationship of the old bridge A, the old bridge B, the new bridge C and the new bridge D in the multi-beam bridge, calculate the vertical deformation distribution curve at the splicing position of the old bridge A, the old bridge B and the new bridge C, the new bridge D along the longitudinal direction of the bridge, and obtain the maximum value D of the vertical deformation difference at this time. max ; S2: Preliminarily design the structure form of the rigid splicing structure A and the rigid splicing structure B according to D max-(i) =75%×D max ; S3: Set the rigid splicing structure A and the rigid splicing structure B according to S2, and preliminarily set the length L1 of the rigid splicing structure A as L A 1=2 / 3×min(L C , L B ), the length L3 of the rigid splicing structure B as L D 3=2 / 3×min(L A , L B ), L C , L DThe span of the old bridge A, the old bridge B, the new bridge C, and the new bridge D respectively, the distribution curve of the vertical deformation at the splicing position of the old bridge A, the old bridge B, the new bridge C, and the new bridge D is calculated, and the maximum value D of the vertical deformation difference in the section where the flexible splicing structure is located is obtained max-(i+1) ; S4: If 90%×D max-(i) ≤ D max-(i+1) ≤ 110%×D max-(i) , then the preliminary design is completed and step S5 is entered; otherwise, return to step S3, increase or decrease the length L1 of the rigid splicing structure A and the length L3 of the rigid splicing structure B, and recalculate; if L1 cannot satisfy more than 1 / 2 of min(L A , L C ) or L3 cannot satisfy more than 1 / 2 of min(L B , L D ), then return to step S2 to redesign the rigid splicing structure A and the rigid splicing structure B; S5: Further checking whether the transverse stress of the old bridge A, the old bridge B, the new bridge C, the new bridge D, and the new-old bridge splicing structure meets the design requirements of each material, and if yes, then the corresponding new-old bridge splicing structure length L1, L2, L3 is the final scheme, L2 is the length of the flexible splicing structure, otherwise, return to step S2. max-(i+1)

[0006] Further, in S1, the old bridge A and the old bridge B are longitudinally adjacent existing simply supported multi-beam bridge structures, and the old bridge A and the old bridge B are connected through an old bridge expansion joint; the new bridge C and the new bridge D are newly built simply supported multi-beam bridge structures, parallel to and located on the same side of the old bridge A and the old bridge B, and the new bridge C and the new bridge D are connected through a new bridge expansion joint; the span L C of the new bridge C is 50% to 150% of the span L A of the old bridge A, but does not include 100%. The spans of the old bridge A, the old bridge B, the new bridge C, and the new bridge D are L A , L B , L C , and L D respectively, and should satisfy the following formula: L=L A +L B =L C +L D (L A ≠L C ).

[0007] ​Further, the main girder sections of the old bridge A, the old bridge B, the new bridge C and the new bridge D are of the same form; a plurality of old bridge diaphragms are arranged between the adjacent main girders of the old bridge A and the old bridge B, the number of new bridge diaphragms arranged on the main girders of the new bridge C and the new bridge D is not less than two; and no diaphragm structure is arranged between the old bridge A, the old bridge B and the new bridge C and the new bridge D.

[0008] Further, in S3, the new and old bridge splicing structures with different connection stiffnesses are adopted between different sections of the old bridge A, the old bridge B and the new bridge C and the new bridge D, the rigid splicing structure A is adopted within the range of 0~L1 along the longitudinal direction of the bridge, the flexible splicing structure is adopted within the range of L1~L1+L2, and the rigid splicing structure A is adopted within the range of L1+L2~L along the longitudinal direction of the bridge. The new and old bridge splicing structures should satisfy the following formula along the longitudinal direction of the bridge: L= L1+L2+L3(L A ≠L C ); L1≤min(L A , L C ); L2≤min(L B , L D ).

[0009] Further, the rigid splicing structure A and the rigid splicing structure B are cement concrete reinforced structures for connecting the adjacent main girder structures of the old bridge and the new bridge and transmitting bending moment, axial force, shear force and other structural internal forces; and the flexible splicing structure is an asphalt concrete structure and plays a role of continuous pavement layer and does not transmit bending moment, axial force, shear force and other structural internal forces.

[0010] Further, in S3, the deformation of each position of the multi-beam bridge can be obtained by the following formula: △=δ(z)·η(x); wherein δ(z) is a longitudinal deflection matrix of each main girder, and η(x) is a load transverse distribution coefficient matrix of a certain piece of main girder section. δ(z) is an m×1 matrix, and m is not less than the number of longitudinal key sections on each bridge; and η(x) is a 1×n matrix, and n is equal to the sum of the number of old bridge main girder pieces n1 and the number of new bridge main girder pieces n2.

[0011] Further, the longitudinal key sections are selected according to the following principles: the diaphragm section position, the section position of the midpoint between the adjacent diaphragms, the positions near the two sides of the intersection section of the rigid splicing structure A, the rigid splicing structure C and the flexible splicing structure, the old bridge expansion joint and the new bridge expansion joint section position, the section position of the midpoint between the old bridge expansion joint and the new bridge expansion joint, and other key section positions.

[0012] Further, the longitudinal deflection matrix δ(z) of the main girder is obtained by the following formula: δ(z)=[K] -1 [P] Wherein, [K] is the main beam stiffness matrix, [P] is the node force matrix; The element values in the stiffness matrix [K] are related to the product EI of the elastic modulus and the bending resistance moment of the main beams of the old bridge A, the old bridge B, the new bridge C and the new bridge D.

[0013] Further, the bending stiffness of the old bridge A and the old bridge B is determined according to the field measurement results, and the bending stiffness values of each longitudinal key section can be different, that is, the old bridge A and the old bridge B are variable stiffness structures in the longitudinal direction; the bending stiffness of the new bridge C and the new bridge D is determined according to the design document or the field measurement result, and the bending stiffness values of each longitudinal key section are the same, that is, the new bridge C and the new bridge D are equal stiffness structures in the longitudinal direction.

[0014] Further, the η(x) is obtained by the grillage method, and for the section of the flexible splicing structure, the element value of the corresponding non-solution side main beam in η(x) is set to 0. The rest is still the calculated value.

[0015] Compared with the prior art, the present application has the following advantages: (1) Effectively release structural constraints, reduce excessive design redundancy. By adopting the combination of rigid splicing structure and flexible splicing structure, the constraints of the new and old bridge splicing structure are partially released, the transverse stress of the new and old bridge main beam at the misaligned splicing position is reduced, and the old bridge slab cracking problem is avoided. By optimizing the length and position of the rigid splicing structure, the excessive redundant design of the splicing structure is effectively reduced under the premise of ensuring the safety of the structure.

[0016] (2) Accurate deformation control can be achieved, which is suitable for variable stiffness structure and has wide applicability. By establishing the main beam longitudinal deflection matrix δ(z) and the load transverse distribution coefficient matrix η(x), the vertical deformation difference distribution curve at the splicing position can be accurately calculated, and the scientificity of the design result is ensured. Considering the variable stiffness characteristics of the old bridge main beam, the bending stiffness is determined according to the field measurement results, so that the design is more in line with the actual engineering conditions. It is suitable for misaligned arrangement of new bridge span of 50% to 150% (not including 100%) of old bridge span, and has strong engineering adaptability.

[0017] (3) Simple structure, reliable at the same time. No transverse diaphragm structure is set between the old bridge and the new bridge, which simplifies the structural design, facilitates construction operation and reduces construction difficulty. The rigid splicing structure adopts cement concrete reinforced structure, which can transfer bending moment, axial force and shear force; the flexible splicing structure adopts asphalt concrete structure, which only plays a continuous role of pavement layer, and the function is clear and the stress is clear. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Flow chart of design method for staggered splicing of multi-beam bridge with different vertical deformations Figure 2 Structure diagram of multi-beam bridge with different vertical deformations Figure One ; Figure 3 Structure diagram of multi-beam bridge with different vertical deformations Figure Two (including old bridge diaphragm and new bridge diaphragm); Figure 4 Structure diagram of multi-beam bridge with different vertical deformations Figure Three ; Figure 5 Schematic diagram of key section selected in step S3.

[0019] Reference numerals: 1, old bridge A, 2, old bridge B, 3, new bridge C, 4, new bridge D, 5, old bridge diaphragm, 6, new bridge diaphragm, 701, rigid splicing structure A, 702, flexible splicing structure, 703, rigid splicing structure B, 801, old bridge expansion joint, 802, new bridge expansion joint. DETAILED DESCRIPTION

[0020] The present application will be described in detail below in combination with the drawings and specific embodiments. In the technical solution, if the component model, material name, connection structure, control method, algorithm and other features are not explicitly described, they are considered as common technical features disclosed in the prior art.

[0021] Example 1 In this embodiment, a group of multi-beam bridges needing staggered splicing and widening is obtained from a practical engineering design scheme, as shown in FIG. 1. Figure 2 The bridge spans of the old bridge A (1), the old bridge B (2), the new bridge C (3) and the new bridge D (4) are L A = 30 m, L B = 20 m, L C = 35 m and L D = 15 m respectively; the span L C of the new bridge C (3) is 116% × L A , which meets the requirement that the span L C of the new bridge C should be 50% to 150% of the span L A of the old bridge A, but not including 100%.

[0022] The main beams of the old bridge A (1) and the old bridge B (2) are both precast T-beam structures, and the main beams of the new bridge C (3) and the new bridge D (4) are both precast small box girder structures, as shown in FIG. 2. Figure 3The old bridge A (1) has seven main girder pieces, the old bridge B2 has eight main girder pieces, and the new bridge C (3) and the new bridge D (4) each have three main girder pieces. The old bridge A (1), the old bridge B (2), the new bridge C (3) and the new bridge D (4) each have three transverse diaphragms. The old bridge A (1) and the old bridge B (2) are connected through the old bridge expansion joint 801, and the new bridge C (3) and the new bridge D (4) are connected through the new bridge expansion joint 802.

[0023] The embodiment provides a multi-girder bridge misalignment splicing design method with different vertical deformations, as shown in the figure, comprising the following steps: Figures 1-4 S1: According to the misalignment relationship of the old bridge A1, the old bridge B2, the new bridge C3 and the new bridge D4 in the multi-girder bridge, the vertical deformation distribution curve of the old bridge A1, the old bridge B2 and the new bridge C3, and the new bridge D4 at the splicing position is calculated along the longitudinal direction of the bridge, and the maximum value D of the vertical deformation difference at this time is obtained. max max D = 20mm; S2: The structure forms of the rigid splicing structure A701 and the rigid splicing structure B703 are designed according to D max-(i) = 75%xD max = 15cm; in the specific embodiment, the rigid splicing structure A701 and the rigid splicing structure B703 are cement concrete reinforced structures, which are used for connecting the adjacent main girder structures of the old bridge and the new bridge, transmitting bending moment, axial force, shear force and other structural internal forces, and can theoretically meet the deformation requirement of the vertical deformation difference of 15cm; the flexible splicing structure 702 is an asphalt concrete structure, which plays a role of continuous pavement layer and does not transmit bending moment, axial force, shear force and other structural internal forces, and can meet the deformation requirement of the vertical deformation difference of 20mm.

[0024] S3: The rigid splicing structure A701 and the rigid splicing structure B703 are set according to S2, and the length L1 of the rigid splicing structure A701 is preliminarily set as L1 = 2 / 3xmin(L A , L C ), the length L3 of the rigid splicing structure B703 is preliminarily set as L3 = 2 / 3xmin(L B , L D ), L A , L B , L C , L D are the spans of the old bridge A1, the old bridge B2, the new bridge C3 and the new bridge D4 respectively, the vertical deformation distribution curve of the old bridge A1, the old bridge B2 and the new bridge C3, and the new bridge D4 at the splicing position is calculated, and the maximum value D max-(i+1) of the vertical deformation difference in the section where the flexible splicing structure 702 is located is obtained. ​​In a specific implementation, the splicing structure between the old and new bridges is set according to step S2, and the length L1 of the rigid splicing structure A701 is initially set as 2 / 3 × min (L A L C =20m, the length L3 of the rigid splicing structure B703 is L3 = 2 / 3 × min (L B L D If ) = 10m, then the length L2 of the flexible splicing structure 702 is 20m; In a specific implementation, the longitudinal key sections are selected according to the following principles: the position of the transverse diaphragm section, the position near both sides of the junction of the rigid splicing structure A701, the rigid splicing structure C703 and the flexible splicing structure 702, and the position of the sections of the old bridge expansion joint 801 and the new bridge expansion joint 802.

[0025] Based on the selected key sections, such as Figure 5 As shown, the longitudinal deflection matrix δ(z) of each bridge is established respectively: The longitudinal deflection matrix δ of old bridge A1 A (z) is a 5×1 matrix. The key section locations are the cross section of the old bridge A diaphragm (3 sections) and the section 0.5m away from the interface between the rigid splicing structure A701 and the flexible splicing structure 702 (1 section). Longitudinal deflection matrix δ of old bridge B2 B (z) is a 6×1 matrix. The key section locations are the cross section of the old bridge B diaphragm (3), the sections at 0.5m on both sides of the interface between the flexible splicing structure 702 and the rigid splicing structure B703 (2), and the section location at the junction with the expansion joint 802 of the new bridge (1). Longitudinal deflection matrix δ of Xinqiao C3 C (z) is a 6×1 matrix. The key section locations are the cross section of the new bridge C diaphragm (3), the sections at 0.5m on both sides of the interface between the rigid splicing structure A701 and the flexible splicing structure 702 (2), and the section location at the junction with the old bridge expansion joint 801 (1). Longitudinal deflection matrix δ of Xinqiao D4 D (z) is a 5×1 matrix. The key section locations are the cross section of the new bridge D diaphragm (3 sections) and the sections 0.5m on both sides of the interface between the flexible splicing structure 702 and the rigid splicing structure B703 (2 sections).

[0026] Based on the on-site inspection results of old bridges A1 and B2, the proposed elastic model values ​​for old bridge A1 are: E within 2m of the beam segment. a1 E is located within a range of 2m to 8m from the beam segment. a2 The remaining beam segments are within the range of E. a3 (E) a1 >E a2 >E a3); The proposed elastic model values ​​for old bridge B2 are: E within 2m of the beam segment. b1 E is located within 2m to 5m of the beam segment. b2 The remaining beam segments are within the range of E. a3 (E) b1 >E b2 >E b3 According to the design documents for new bridges C3 and D4, the elastic moduli of new bridges C3 and D4 are E, respectively. c E d .

[0027] Based on the number of main beams of each bridge, establish the lateral distribution coefficient matrix η(x) for each bridge: The lateral distribution coefficient matrix η of old bridge A1 A (x) is a 1×10 matrix, and η is the lateral distribution coefficient matrix of the old bridge B2. B (x) is a 1×11 matrix, and η is the lateral distribution coefficient matrix of Xinqiao C3. C (x) is a 1×11 matrix, and η is the lateral distribution coefficient matrix of Newbridge D4. D (x) is a 1×11 matrix.

[0028] Among them, for the old bridge A1, L1~L A η, the lateral distribution coefficient matrix of key sections within the section A The 8th to 10th elements of (x) are all equal to 0; for the old bridge B, L A The lateral distribution coefficient matrix η of the key sections within the L1+L2 segment B The 9th to 11th elements of (x) are all equal to 0; for L1 to L2 of the new bridge C... C η, the lateral distribution coefficient matrix of key sections within the section C The 8th to 10th elements of (x) are all equal to 0, and the 11th element is also equal to 0; for the L of Newbridge D4 C The lateral distribution coefficient matrix η of the key sections within the L1+L2 segment C Elements 9 through 11 of (x) are all equal to 0. Using the matrix established above, calculate the distribution curves of vertical deformation at the joints of old bridge A1, old bridge B2, and new bridge C3, new bridge D4, and find the maximum vertical deformation difference D at these joints. max-(i+1) =16mm.

[0029] S4: Maximum vertical deformation difference D max-(i+1) =16mm, meets 90%D max-(i) ≤D max-(i+1) ≤110%D max-(i) Requirements.

[0030] S5: further checking whether the transverse stress of the old bridge A1, the old bridge B2, the new bridge C3, the new bridge D4 and the splicing structure 7 of the old and new bridges meets the design requirements of each material, the transverse stress is less than the tensile strength limit of each structural material, and the misaligned splicing design of the multi-beam bridge with different vertical deformations is completed.

[0031] Example 2 The difference from the above-mentioned example 1 is that in step S3, the distribution curve of the vertical deformation at the splicing position of the old bridge A, the old bridge B and the new bridge C, the new bridge D is calculated, and the maximum value D of the vertical deformation difference at this time is max-(i+1) = 18mm In step S4, the maximum value D of the vertical deformation difference max-(i+1) = 18mm does not meet the requirement of 90% D max-(i) ≤ D max-(i+1) ≤ 110% D max-(i) .

[0032] Return to step S3, still set the splicing structure of the old and new bridges according to step S2, and modify the length L1 = 25m of the rigid splicing structure A701 and the length L3 = 13m of the rigid splicing structure B703, so that the length L2 = 12m of the flexible splicing structure 702; recalculate the distribution curve of the vertical deformation at the splicing position of the old bridge A1, the old bridge B2 and the new bridge C3, the new bridge D4, and the maximum value D of the vertical deformation difference at this time is max-(i+2) = 15.5mm.

[0033] Enter step S4, the maximum value D of the vertical deformation difference max-(i+2) = 15.5mm meets the requirement of 90% D max-(i) ≤ D max-(i+1) ≤ 110% D max-(i) .

[0034] Enter step S5, further check the transverse stress of the old bridge A1, the old bridge B2, the new bridge C3, the new bridge D4 and the splicing structure of the old and new bridges, which is less than the tensile strength limit of each structural material, and the misaligned splicing design of the multi-beam bridge with different vertical deformations is completed.

[0035] The components not described in detail in this embodiment are existing components that can be purchased in the public channel.

[0036] The above description of the embodiments is for the convenience of those skilled in the art to understand and use the invention. Those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described herein to other embodiments without creative labor. Therefore, the present application is not limited to the above-mentioned embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present application should be within the scope of protection of the present application.

Claims

1. A method for designing staggered splicing of multi-beam bridges with different vertical deformations, characterized in that, The method comprises the following steps: S1: According to the misalignment relationship of the old bridge A (1), the old bridge B (2), the new bridge C (3) and the new bridge D (4) in the multi-beam bridge, the distribution curve of the vertical deformation at the splicing position of the old bridge A (1), the old bridge B (2) and the new bridge C (3), the new bridge D (4) is calculated along the longitudinal direction of the bridge, and the maximum value D of the vertical deformation difference at this time is obtained max ; S2: preliminary according to D max-(i) = 75% x D max Design the structure form of rigid splicing structure A (701), rigid splicing structure B (703). S3: set rigid splicing structure A (701), rigid splicing structure B (703) according to S2, and preliminarily set the length L1=2 / 3×min(L A , C L ), the length L3=2 / 3×min(L B , D L ) of rigid splicing structure B (703), L A , L B , L C , L D are the span of old bridge A (1), old bridge B (2), new bridge C (3), new bridge D (4) respectively, calculate the distribution curve of vertical deformation at the splicing position of old bridge A (1), old bridge B (2) and new bridge C (3), new bridge D (4), and obtain the maximum value D max-(i+1) of vertical deformation difference in the section where the flexible splicing structure (702) is located. S4: if 90% x D max-(i) ≤ D max-(i+1) ≤ 110% x D max-(i) , then the preliminary design is completed and step S5 is entered; otherwise, return to step S3 to increase or decrease the length L1 of the rigid splicing structure A (701) and the length L3 of the rigid splicing structure B (703) and recalculate; if L1 cannot satisfy more than 1 / 2 of min(L A , L C ) or L3 cannot satisfy more than 1 / 2 of min(L B , L D ), then return to step S2 to redesign the rigid splicing structure A (701) and the rigid splicing structure B (703); S5: further checking whether the transverse stress of the old bridge A (1), the old bridge B (2), the new bridge C (3), the new bridge D (4) and the new and old bridge splicing structure (7) meets the design requirements of each material, and if it meets the requirements, D max-(i+1) The lengths L1, L2 and L3 of the corresponding new and old bridge splicing structure (7) are the final scheme, and L2 is the length of the flexible splicing structure (702), otherwise return to step S2.

2. The method according to claim 1, wherein, In S1, the old bridge A (1) and the old bridge B (2) are longitudinally adjacent existing simply supported multi-beam bridge structures, the old bridge A (1) and the old bridge B (2) are connected through an old bridge expansion joint (801); the new bridge C (3) and the new bridge D (4) are newly built simply supported multi-beam bridge structures, which are parallel to and located on the same side of the old bridge A (1) and the old bridge B (2), and the new bridge C (3) and the new bridge D (4) are connected through a new bridge expansion joint (802); the span L C of the new bridge C (3) is 50% to 150% of the span L A of the old bridge A (1), but does not include 100%.

3. The method of claim 1, wherein the method is characterized by, The main girder section forms of the old bridge A (1), the old bridge B (2), the new bridge C (3) and the new bridge D (4) are the same; a plurality of old bridge diaphragms (5) are arranged between the adjacent main girders of the old bridge A (1) and the old bridge B (2), the number of new bridge diaphragms (6) arranged on the main girders of the new bridge C (3) and the new bridge D (4) is not less than two; and no diaphragm structure is arranged between the old bridge A (1), the old bridge B (2) and the new bridge C (3), the new bridge D (4).

4. The method of claim 1, wherein the method is characterized by, In S3, the new and old bridge splicing structures between the old bridge A (1), the old bridge B (2) and the new bridge C (3), the new bridge D (4) in different sections adopt different connection stiffnesses, the rigid splicing structure A (701) is adopted within the range of 0~L1 along the longitudinal direction of the bridge, the flexible splicing structure (702) is adopted within the range of L1~L1+L2, and the rigid splicing structure A (701) is adopted within the range of L1+L2~L; The new and old bridge splicing structures along the longitudinal dimension of the bridge should satisfy the following formula: L = L1+L2+L3(L A ≠ L C ); L1≤ min(L A , L C ); L2≤ min(L B , L D ).

5. The method of claim 1, wherein, The rigid splicing structure A (701) and the rigid splicing structure B (703) are cement concrete reinforced structures, which are used for connecting the adjacent main girder structures of the old bridge and the new bridge and transmitting the internal force of the structure; The flexible splicing structure (702) is an asphalt concrete structure, which plays a role of continuous paving layer and does not transmit the internal force of the structure.

6. The method of claim 1, wherein the method is characterized by, In S3, the deformation of each position of the multi-beam bridge can be obtained by the following formula: △=δ(z)·η(x); Wherein, δ(z) is the longitudinal deflection matrix of each main girder, and η(x) is the load transverse distribution coefficient matrix of a main girder section; δ(z) is an m×1 matrix, and m is not less than the number of longitudinal key sections on each bridge; η(x) is a 1×n matrix, and n is equal to the sum of the number of old bridge main girder pieces n1 and the number of new bridge main girder pieces n2.

7. The method of claim 6, wherein the method is characterized by, The longitudinal key sections are selected according to the following principles: the diaphragm section position, the section position of the midpoint between adjacent diaphragms, the positions near the two sides of the intersection section of the rigid splicing structure A (701), the rigid splicing structure C (703) and the flexible splicing structure (702), the old bridge expansion joint (801) and the new bridge expansion joint (802) section position, the section position of the midpoint between the old bridge expansion joint (801) and the new bridge expansion joint (802), and other key section positions.

8. The method of claim 6, wherein the method is characterized by, The main girder longitudinal deflection matrix δ(z) is obtained by the following formula: δ(z) = [K] -1 [P] Wherein, [K] is the main girder stiffness matrix, and [P] is the node moment matrix; The element values in the stiffness matrix [K] are related to the product EI of the elastic modulus and the bending resistance moment of inertia of the main girders of the old bridge A (1), the old bridge B (2), the new bridge C (3) and the new bridge D (4).

9. The method of claim 8, wherein the method is characterized by, The bending stiffness of the main girders of the old bridge A (1) and the old bridge B (2) is determined according to the field measurement results, the bending stiffness values of each longitudinal key section can be different, that is, the longitudinal direction of the main girders of the old bridge A (1) and the old bridge B (2) is a variable stiffness structure; the bending stiffness of the main girders of the new bridge C (3) and the new bridge D (4) is determined according to the design document or the field measurement result, the bending stiffness values of each longitudinal key section are the same, that is, the longitudinal direction of the main girders of the new bridge C (3) and the new bridge D (4) is an equal stiffness structure.

10. The method of claim 6, wherein the method is a method of designing a misaligned splicing of a multi-beam bridge with different vertical deformations, characterized in that, The η(x) is obtained by a grillage method, and for a cross section of a region where the flexible splicing structure (702) is located, a value of an element corresponding to a non-solution side main beam in the η(x) is set to 0.

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