Bridge variable stiffness distribution design method, variable stiffness supporting system and bridge structure

Abstract

The invention relates to the field of bridge engineering, in particular to a bridge variable stiffness distribution design method, a variable stiffness supporting system and a bridge structure. Vertical supporting and horizontal force transmission between the main beam and the lower structure are achieved through the variable-rigidity supporting system, in the variable-rigidity supporting system, vertical supporting force is only provided for the main beam through a support, and longitudinal rigidity is provided for the main beam through a variable-rigidity device; through the mode that the functions of providing longitudinal rigidity and vertical bearing capacity are designed separately, the problem that high bearing capacity and small longitudinal rigidity design and manufacturing cannot be achieved at the same time under the condition that a traditional single bridge support needs to meet the bearing capacity requirement and also needs to have the horizontal force transmission function is solved. By means of the variable-rigidity supporting system, according to different pier column heights and different pier column rigidities, reasonable distribution of constraint rigidities of pier columns at different height positions can be achieved by conducting customized design on structural parameters of the corrugated steel pipe, the internal force of a pier is adjusted, and the design economy is improved.

Description

Technical Field

[0001] The present invention relates to the field of bridge engineering, and in particular to a bridge variable stiffness distribution design method, a variable stiffness support system, and a bridge structure. Background Art

[0002] When designing bearings, existing techniques often first determine the bearing capacity and longitudinal stiffness requirements based on a calculation model. Bearing types are then selected based on the required capacity and stiffness range (different bearing models have corresponding stiffness adjustment ranges). Finally, bearing structural parameters are designed based on the specific stiffness requirements. Existing bearing structural designs are influenced by both the bearing capacity and longitudinal stiffness.

[0003] In order to meet the demand for high bearing capacity, if high-strength materials such as high-strength rubber are required when making the bearing, the elastic modulus of the bearing will increase, which will inevitably lead to the objective phenomenon of high stiffness. On this basis, if a smaller longitudinal stiffness is to be achieved, it is necessary to change the structural parameters by raising the bearing to reduce the shear stiffness of the bearing. However, due to working conditions, the range of raising the bearing is limited, resulting in an inability to achieve a relatively ideal small longitudinal stiffness, which makes it difficult to select and design the bearing structure. If the bearing is made of materials with strong deformation ability such as flexible rubber, it is impossible to achieve a relatively ideal high bearing capacity effect. Therefore, according to the design concept of the existing bearing, there is an irreconcilable contradiction between high bearing capacity and low longitudinal stiffness.

[0004] However, in some cases, such as when the superstructure of a continuous simply supported beam utilizes a concrete structure or a heavy main beam such as a large box beam, the substructure's piers have varying heights, and the safety factors (ratio of resistance to internal forces) at the base of each pier vary significantly. Piers with low safety factors become the weakest link in the entire bridge, and it is necessary to reduce the horizontal forces on these piers by reducing the bearing stiffness. In this case, high-capacity, low-longitudinal-stiffness bearings are required to transfer some of the forces to piers with high safety reserves. If bearing stiffness is not considered during design, to compensate for the weak piers, it is often necessary to strengthen other piers or main beams as a whole, which in turn increases material usage. Furthermore, when the safety factor of a pier is significantly lower than that of the others, it will be the first to undergo deformation or failure, leading to a redistribution of internal forces and ultimately a cascading failure.

[0005] Therefore, how to solve the design problem of high bearing capacity and small longitudinal stiffness of the support, realize the stiffness adjustment of the pier with low safety factor, improve the internal force of the pier column, and how to realize variable stiffness distribution between piers of different heights through the support, reduce the difference in safety factors of each pier, realize the optimization of the internal force distribution of the pier, improve bridge safety and reduce material redundancy and waste, are technical problems that technical personnel in this field need to solve. Summary of the Invention

[0006] The purpose of the present invention is to solve at least one of the above-mentioned shortcomings and to provide a bridge variable stiffness distribution design method and a variable stiffness support system and a bridge structure, which can realize the internal force distribution of the pier, control the safety factor, and improve the overall dynamic performance of the bridge.

[0007] In a first aspect, the present invention provides a bridge variable stiffness distribution design method, comprising: providing a variable stiffness support system between a main beam and a substructure, achieving variable stiffness distribution between bridge piers of different heights through the variable stiffness support system, the variable stiffness support system comprising a support and a variable stiffness device, the support vertically supporting the main beam, the support being a sliding support or being in planar contact with the main beam or the substructure; the variable stiffness device longitudinally connecting the main beam and the substructure, the variable stiffness device comprising a corrugated steel pipe, one end of the corrugated steel pipe being connected to the main beam, and the other end of the corrugated steel pipe being connected to the substructure; designing structural parameters of the support according to bearing capacity requirements, and designing the corresponding stiffness of the variable stiffness device according to the stiffness of the pier and the position of the pier in a bridge. The design steps comprise: S1: Determine the target constraint stiffness of the corresponding pier according to the height of each pier K e , so that the safety factor of each pier column, the maximum bending moment at the pier bottom and the longitudinal natural frequency of the main beam all meet the preset requirements; S2: According to the target constraint stiffness of the corresponding pier K e , determine the axial design stiffness of the variable stiffness device on each pier K x ; S3: According to the axial design stiffness of the variable stiffness device on each pier K x , determine the structural parameters of the corrugated steel pipe.

[0008] The present invention adopts a variable stiffness support system to achieve vertical support and horizontal force transmission between the main beam and the substructure. In the variable stiffness support system, the support only provides vertical support force for the main beam, and the longitudinal stiffness of the support is not considered, so that the longitudinal stiffness of the support is set to 0 as much as possible: the support can be set as a sliding support, and the upper and lower support plates of the sliding support itself can achieve horizontal relative sliding, so that the main beam and the bridge substructure can slide against each other, that is, there is no longitudinal stiffness. Alternatively, the support can be made to be in plane contact with the main beam of the superstructure (or the bridge substructure) without being connected, so that the main beam can move longitudinally relative to the bridge substructure, that is, no longitudinal stiffness is provided; on this basis, a variable stiffness device is adopted to provide longitudinal stiffness for the main beam without providing vertical support force; the variable stiffness support system adopts a method of separately designing the functions of providing longitudinal stiffness and vertical bearing capacity, overcoming the difficulty of designing and manufacturing traditional single bridge supports that cannot simultaneously achieve high bearing capacity and low longitudinal stiffness while meeting the bearing capacity requirements and having the horizontal force transmission function. By adopting this solution, when designing the high bearing capacity of the support, there is no need to consider whether the material used for the support can achieve small longitudinal stiffness, which reduces the difficulty of supporting design and manufacturing. On the other hand, when designing the longitudinal stiffness of the variable stiffness device, there is no need to consider the vertical bearing capacity, which is conducive to realizing the design of arbitrary stiffness according to the actual working conditions, and has a wider applicability to working conditions. The mutual cooperation between the support and the variable stiffness device reduces the difficulty of variable stiffness distribution design between piers of different heights.

[0009] The above-mentioned variable stiffness device is used to longitudinally connect the main beam and the bridge substructure. It can not only limit the displacement amplitude of the main beam under external loads (such as earthquakes, strong winds, vehicle impacts, etc.) through mechanical constraints, thereby preventing structural damage or collapse due to excessive displacement, but also utilize the tension-compression coupling effect of the corrugated steel tube to produce energy dissipation effect, thereby adapting to the longitudinal deformation of the main beam.

[0010] When adopting the above-mentioned variable stiffness device for stiffness design, this scheme can realize reasonable distribution of target constraint stiffness for piers of different heights and positions by customizing the structural parameters of the corrugated steel tube according to different pier heights and different pier stiffness requirements, so that the safety factor of each pier, the maximum bending moment of the pier bottom and the longitudinal natural frequency of the main beam all meet the preset requirements, realize variable stiffness distribution of piers of different heights, and controllable stiffness design; adjust the internal force of the pier through the variable stiffness support system, which is conducive to reducing the difference between the safety factors of each pier, thereby improving the design economy, improving the internal force of the pier, and improving the economic benefits and bridge safety.

[0011] Preferably, in step S1, the target constraint stiffness of the corresponding pier is determined K e The steps include: S11: Establish a finite element model based on the designed bridge type and size, and initially set the longitudinal bridge constraint stiffness of each pier toK 0, calculate the bending moment distribution, safety factor and longitudinal natural frequency of each pier; S12: Adjust the longitudinal bridge-direction constraint stiffness distribution of the main beam according to the pier column bending moment distribution, so that the safety factor of each pier bottom meets the first preset requirement, the maximum bending moment of the pier bottom meets the second preset requirement, and the longitudinal natural vibration frequency of the main beam meets the third preset requirement, thereby obtaining the adjusted longitudinal bridge-direction constraint stiffness of each pier column; S13: When the first preset requirement, the second preset requirement, and the third preset requirement are met at the same time, the longitudinal bridge constraint stiffness of each pier is output, which is used as the target constraint stiffness of the corresponding pier. K e .

[0012] The design is convenient and fast, and the calculation amount is small.

[0013] Preferably, the structural parameters include the nominal diameter D , wave distance q , wave height h ,thickness t and length L .

[0014] In a second aspect, the present invention provides a variable stiffness support system, including a variable stiffness device, the variable stiffness device including a corrugated steel pipe, the two ends of the corrugated steel pipe are respectively integrally provided with a first connecting steel plate and a second connecting steel plate, the first connecting steel plate is used to connect the main beam, the second connecting steel plate is used to connect the lower structure of the bridge, and the first connecting steel plate and the second connecting steel plate are arranged in parallel.

[0015] The present invention adopts corrugated steel pipe for main beam damping and limiting, so that the corrugated steel pipe is connected to the main beam through a first connecting steel plate, and is connected to the bridge lower structure through a second connecting steel plate, and the first connecting steel plate and the second connecting steel plate of the variable stiffness device are parallel in the installed state, so that the variable stiffness device transmits force in the axial direction. Under the action of external load, the structural ductility of the corrugated steel pipe can be used to achieve the effect of buffering and shock absorption and preventing the beam from falling, so as to better adapt to the deformation and displacement of the main beam.

[0016] Moreover, by using the above-mentioned variable stiffness device to connect the main beam and the bridge substructure, the stiffness of the corrugated steel pipe can be changed by adjusting the waveform parameters of the corrugated steel pipe, such as the peak height, wave pitch size and corrugation shape, and the bearing capacity of the corrugated steel pipe can be changed by adjusting the wall thickness parameters of the corrugated steel pipe, so that the stiffness of the variable stiffness device matches the displacement dynamic response of the bridge structure and adapts to the actual working conditions. The variable stiffness device has a wide range of adjustable stiffness and wide applicability. The above-mentioned variable stiffness device can be used to adjust the internal forces of the piers, improve the dynamic performance of the main beam, achieve a more ideal vibration reduction effect, and solve the problem of uncontrollable stiffness of the traditional limit system.

[0017] The above-mentioned variable stiffness device can be arranged along the longitudinal direction of the bridge or along the transverse direction of the bridge, and is not limited to the above examples. Its specific arrangement can be reasonably set according to actual working conditions.

[0018] As an implementable embodiment, the first connecting steel plate can be directly connected to the main beam by means of bolts, welding or partial embedding, and the second connecting steel plate can also be directly connected to the bridge substructure by means of bolts, welding or partial embedding.

[0019] Preferably, the corrugated steel pipe is filled with a flexible material that can adapt to the compression deformation of the corrugated steel pipe. As another possible implementation method, the corrugated steel pipe in the variable stiffness device can also adopt a hollow structure.

[0020] Preferably, the stiffness varying device further comprises a stopper vertically disposed on the bridge substructure, wherein the second connecting steel plate is connected to the bridge substructure via the stopper, and the stopper axially limits one end of the stiffness varying device.

[0021] Preferably, the limit stopper is a metal structure or a concrete structure.

[0022] As one possible implementation method, when the limit stop adopts a metal structure, the second connecting steel plate can be welded to the limit stop on site, or a detachable connection method such as threaded connection or bonding can be adopted, and the limit stop can be integrally connected to the lower structure of the bridge by welding or pre-embedding. As another possible implementation method, when the limit stop adopts a concrete structure, the limit stop can be integrally connected to the lower structure of the bridge by tying pre-embedded steel bars, and a threaded sleeve can be embedded in the limit stop, thereby facilitating the installation and fixation of the limit stop and the second connecting steel plate by bolting, which is not limited to the above examples.

[0023] The above-mentioned bridge substructure includes a cap beam and piers, and can also be piers without a cap beam.

[0024] Preferably, a transverse diaphragm is provided at the bottom of the main beam, the corrugated steel pipe is located between the transverse diaphragm and the limit baffle, the first connecting steel plate is bolted to the transverse diaphragm, and the second connecting steel plate is bolted to the limit baffle. The corrugated steel pipe is arranged between the transverse diaphragm and the limit baffle, so that the first connecting steel plate at one end of the corrugated steel pipe is bolted to the transverse diaphragm, and the second connecting steel plate at one end is bolted to the limit baffle, that is, the variable stiffness device is arranged along the longitudinal direction of the bridge. This can be used to control the width of the expansion joint of the main beam and prevent the beam from falling. The corrugated steel pipe is arranged between the transverse diaphragm and the limit baffle, and the first connecting steel plate and the second connecting steel plate at both ends can effectively transmit the axial load through a larger contact area. Compared with the method of connecting the top of the first steel plate to the main beam, or connecting the bottom of the second steel plate to the lower structure of the bridge, the structural stress resistance of this arrangement is better. Furthermore, by connecting the corrugated steel pipe to the transverse diaphragm and the limit baffle with bolts, this solution is easy to install and disassemble, which is conducive to later maintenance and replacement, and has low maintenance costs.

[0025] Preferably, the variable-stiffness support system further includes a support for vertically supporting the main beam. The support may be a sliding support, preferably a sliding plate support, or may be arranged in contact with the main beam or substructure plane so that the longitudinal stiffness of the support is zero. The support and the variable-stiffness device together support the main beam and transmit horizontal force.

[0026] In a third aspect, the present invention provides a bridge structure comprising a bridge substructure, a main beam and the above-mentioned variable stiffness support system, wherein the main beam comprises a plurality of longitudinal beams and a plurality of transverse diaphragms; The variable stiffness support system is located between the bridge substructure and the main beam. The variable stiffness support system is arranged at intervals along the transverse direction of the bridge. Each variable stiffness device is arranged along the longitudinal direction of the bridge. The first connecting steel plate is connected to the transverse diaphragm, and the second connecting steel plate is connected to the bridge substructure through a limit block. The support is in plane contact with the main beam or the bridge substructure, and the support is used to vertically support the main beam.

[0027] The above-mentioned bridge structure is adopted, by using skateboard supports, and making the supports contact with the main beam or the bridge substructure plane, the longitudinal stiffness of the supports is set close to 0, and only the vertical load is transmitted by the supports. The load is transmitted along the longitudinal bridge direction through the variable stiffness device to adapt to the longitudinal deformation of the main beam. On the one hand, this can avoid structural damage of the supports due to excessive displacement and deformation of the main beam. On the other hand, it can absorb axial load excitation under the tension-compression coupling effect of the corrugated steel pipe. The longitudinal constraint force of the variable stiffness support system on the main beam is significantly enhanced as the displacement amplitude of the beam increases, forming a progressive limit protection, which can effectively suppress the risk of beam falling under extreme working conditions and ensure the overall structural safety of the bridge.

[0028] Preferably, the variable stiffness support system is symmetrically arranged about the center line of the bridge substructure, which is beneficial to the expansion joint control.

[0029] Preferably, the longitudinal beam can be an I-shaped concrete beam, a T-shaped concrete beam, a small box beam or an I-beam beam, etc.

[0030] Preferably, two variable stiffness support systems are provided between two adjacent longitudinal beams to facilitate uniform force distribution.

[0031] Preferably, threaded sleeves are embedded in both the transverse partition and the limit block, the transverse partition is connected to the first connecting steel plate by bolts, and the limit block is connected to the second connecting steel plate by bolts, which is convenient for maintenance.

[0032] Compared with the prior art, the present invention has the following beneficial effects: 1. The design method provided by the present invention improves the vertical bearing capacity of the main beam by adopting a support and sets the longitudinal stiffness of the support to 0 as much as possible, so that the issue of whether the longitudinal stiffness of the support is compatible with the bearing capacity is not considered during the design, which is conducive to better realizing the high bearing capacity design of the variable stiffness support system. By adopting a variable stiffness device to provide longitudinal stiffness for the main beam without providing vertical support force, the stiffness control of the variable stiffness support system between the main beam and the bridge substructure is realized; by designing the functions of providing longitudinal stiffness and vertical bearing capacity separately, the design and manufacturing difficulties of a single bridge support that cannot simultaneously achieve high bearing capacity and small longitudinal stiffness are overcome, and this coordination method can reduce the difficulty of variable stiffness distribution design between piers of different heights.

[0033] 2. The present invention uses a variable stiffness device with a corrugated steel tube to longitudinally connect the main beam and the bridge substructure. It can not only limit the displacement amplitude of the main beam under external loads (such as earthquakes, strong winds, vehicle impacts, etc.) through mechanical constraints to prevent structural damage or collapse due to excessive displacement, but also utilize the tension-compression coupling effect of the corrugated steel tube to produce energy dissipation effect, thereby adapting to the longitudinal deformation of the main beam.

[0034] 3. The design method of the present invention realizes reasonable distribution of target constraint stiffness for piers of different heights by customizing the structural parameters of the corrugated steel tube in the variable stiffness device according to the stiffness of the pier itself, so as to make the safety factor of each pier basically consistent under the ultimate bearing capacity state, improve the design economy, improve the internal force of the pier, and evenly distribute the internal force of high and low piers, which is beneficial to improving the dynamic performance of the main beam and improving economic benefits.

[0035] 4. By adopting the variable stiffness device of the present invention, the stiffness can be adjusted in a wide range, the stiffness design is controllable, and the adaptability to working conditions is good.

[0036] 5. The design method provided by the present invention can increase the length of the bridge, realize the aggregation of pier groups, improve the overall stiffness and dynamic performance of a bridge, reduce the arrangement of expansion joints and improve driving comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the longitudinal layout diagram of a beam bridge; Figure 2 Adjustment flow chart for the distribution of longitudinal bridge-direction restraint stiffness of the main beam; Figure 3 Schematic diagram of the structure of corrugated steel pipe Figure 1 ; Figure 4 Schematic diagram of the structure of corrugated steel pipe Figure 2 ; Figure 5 Schematic diagram of the structure of the variable stiffness device in Example 1; Figure 6 This is the installation diagram of the variable stiffness device; Figure 7 Schematic diagram of the structural arrangement of the variable stiffness device in the internal structure of the main beam ( Figure 2 Remove the bridge deck); Figure 8 A simplified diagram of the arrangement of the variable stiffness device ( Figure 3 Remove the main beam and longitudinal beam); Figure 9 This is a schematic diagram of the arrangement of the variable stiffness device in the transverse direction of the bridge; Figure 10 for Figure 9 The large-scale drawing of part A in the figure; Figure 11 This is a schematic diagram of the arrangement of the variable stiffness device in the longitudinal bridge direction; Figure 12 for Figure 11 The large-scale drawing of part B in the Figure 13 is the internal force and moment diagram of the pier under the basic combination (equal stiffness constraint); Figure 14 is the internal force and moment diagram of the pier under the basic combination (variable stiffness constraint); Figure 15 This is an analytical simulation diagram of the longitudinal natural frequency of the main beam obtained through finite element software.

[0038] Markings in the figure: 1-corrugated steel pipe; 2-first connecting steel plate; 21-first connecting hole; 3-second connecting steel plate; 31-second connecting hole; 4-limiting block; 5-cap beam; 6-cross partition; 7-longitudinal beam; 8-boss block; 9-support. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments, as all technologies implemented based on the present invention fall within the scope of the present invention.

[0040] Unless otherwise specified, in the description of the specific embodiments of the present invention, the terms indicating the orientation or positional relationship, such as "upper", "lower", "left", "right", "center", "inside", and "outside", are based on the expressions of the orientation or positional relationship shown in the accompanying drawings, or are the orientation or positional relationship in which the invented product / device / apparatus is placed when it is conventionally used. These terms of orientation or positional relationship are merely for the purpose of facilitating the description of the scheme of the present invention or simplifying the description of the specific embodiments to facilitate the rapid understanding of the scheme by technicians, and do not indicate or imply that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship, and therefore should not be understood as limiting the present invention.

[0041] In addition, if the terms "horizontal", "vertical", "overhanging", "parallel" and the like appear, it does not mean that the corresponding devices / components / elements are required to be absolutely horizontal or vertical or overhanging or parallel, but may be slightly tilted or have deviations. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but may be slightly tilted. Alternatively, it can be simply understood that the corresponding devices / components / elements are set in directions such as "horizontal", "vertical", "overhanging", and "parallel", and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably an error / deviation within ±8%, more preferably an error / deviation within ±6%, more preferably an error / deviation within ±5%, and more preferably an error / deviation within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its role in the solution of the present invention.

[0042] In addition, the expressions “first”, “second”, “third”, etc. in the terms are merely used to distinguish the description of the same or similar components, and should not be understood as emphasizing or implying the relative importance of specific components.

[0043] In addition, in the description of the embodiments of the present invention, "several," "plurality," and "a number" represent at least two. It can also be any number such as two, three, four, five, six, seven, eight, nine, or even more than nine.

[0044] Furthermore, in the description of the technical solution of the present invention, unless otherwise expressly specified, defined, or limited, the terms "disposed," "installed," "connected," "connected," "provided with," "laid," and "arranged" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections. They may be welded, riveted, bolted, threaded, or other commonly used connection methods in the art. Such connections may be mechanical, electrical, or communicative; they may be direct, indirect via an intermediate medium, or internally connected between two components.

[0045] Example 1 This embodiment provides a bridge variable stiffness distribution design method. A variable stiffness support system is employed between the main beam and the bridge substructure. This system achieves variable stiffness distribution between piers of different heights. The variable stiffness support system includes high-load-bearing capacity supports and a variable stiffness device. The supports support the main beam, with their longitudinal stiffness set to zero whenever possible. The variable stiffness device distributes the stiffness to provide longitudinal stiffness.

[0046] The longitudinal stiffness of the support can be set to 0 in the following two ways: The first type uses sliding bearings, leveraging the deformation capacity of the sliding bearings to enable the main beam to slide. In existing technologies, sliding bearings typically consist of an upper bearing plate, which connects to the main beam, and a lower bearing plate, which connects to the bridge substructure. The upper and lower bearing plates slide together to accommodate horizontal displacement and deformation of the main beam. Sliding bearings can be friction pendulum bearings, spherical sliding bearings, bidirectional sliding bearings, or sliding plate bearings. Sliding plate bearings are preferred.

[0047] The second method involves unconstraining the supports from the main beam or bridge substructure. For example, the supports are fixedly connected to the bridge substructure, leaving no connection between the supports and the main beam, allowing for planar contact and allowing the main beam to slide relative to the supports. Alternatively, the supports are fixedly connected to the main beam, leaving no connection between the supports and the bridge substructure, allowing the main beam and the supports to slide relative to the bridge substructure. Fixed supports can be used.

[0048] like Figures 1-8 As shown, in this embodiment, a variable stiffness device is used to longitudinally connect the main beam and the cap beam 5, the cap beam 5 is connected to the pier, and the variable stiffness device is arranged at intervals along the transverse bridge direction; the variable stiffness device includes a corrugated steel pipe 1, and the two ends of the corrugated steel pipe 1 are respectively integrally provided with a first connecting steel plate 2 and a second connecting steel plate 3, the first connecting steel plate 2 is connected to the main beam, and the second connecting steel plate 3 is connected to the cap beam 5, and the first connecting steel plate 2 and the second connecting steel plate 3 are arranged in parallel; the longitudinal bridge direction constraint stiffness distribution of the main beam is achieved by the variable stiffness devices at different pier positions, including the following steps: S1: Determine the target constraint stiffness of the corresponding pier according to the height of each pier K e , so that the safety factor, bending moment distribution and main beam natural vibration frequency of each pier column meet the preset requirements; S2: According to the target constraint stiffness of the corresponding pier K e , determine the design stiffness of the variable stiffness device on each pier K x ; S3: According to the design stiffness of the variable stiffness device on each pier Kx , determine the structural parameters of the corrugated steel pipe.

[0049] The present invention uses the above-mentioned variable stiffness device with corrugated steel tubes to longitudinally connect the main beam and the bridge substructure (such as the cap beam). It can not only limit the displacement amplitude of the main beam under external loads (such as earthquakes, strong winds, vehicle impacts, etc.) through mechanical constraints to prevent structural damage or collapse due to excessive displacement, but also utilize the tensile-compression coupling effect of the corrugated steel tubes to produce energy dissipation effects and adapt to the longitudinal deformation of the main beam. When using the above-mentioned variable stiffness device for stiffness design, this solution can achieve a reasonable distribution of target constraint stiffness for piers of different heights by customizing the structural parameters of the corrugated steel tubes in the above-mentioned variable stiffness device according to different pier heights and different pier stiffness requirements, so that the safety factor of each pier, the maximum bending moment at the pier bottom, and the longitudinal natural frequency of the main beam all meet the preset requirements, thereby achieving variable stiffness distribution for piers of different heights, thereby improving the internal forces of the piers and making the stiffness design controllable. The internal forces of each pier are adjusted through this variable stiffness support system, which is not restricted by the mutual influence of bearing capacity and stiffness, and is conducive to reducing the differences between the safety factors of each pier, thereby improving the design economy, improving the internal forces of the piers, and increasing economic benefits.

[0050] When traditional bearings are used to support and transmit force between the upper and lower structures of a bridge, their upper and lower base plates are generally connected to the upper and lower structures of the bridge respectively during installation. They are used to reliably transmit the reaction force, deformation, displacement, and rotation of the upper structure of the bridge to the lower structure. They cannot simultaneously meet the design requirements of high bearing capacity and low longitudinal stiffness. High bearing capacity is inevitably accompanied by high stiffness. If the stiffness is too high, there will be redundancy in the stiffness design, resulting in material waste. In addition, if the bearing stiffness is too large, it is prone to damage in the case of large longitudinal displacement and deformation of the bridge main beam. Therefore, in some cases, specific requirements for the longitudinal flexibility of the bearing are required. However, when manufacturing this type of bearing, it is necessary to balance the contradiction between vertical bearing capacity and longitudinal flexibility. For example, for the working conditions requiring a vertical bearing capacity greater than 4000kN and a longitudinal stiffness less than 800kN / m, the core difficulty in manufacturing this type of bearing is that for the high bearing capacity requirement, high-strength materials such as high-strength rubber are required, while for the small longitudinal stiffness requirement, materials with strong deformation ability such as flexible rubber are required, resulting in a contradiction between high bearing capacity and low longitudinal stiffness.

[0051] To address the above challenges, this embodiment proposes the use of a variable stiffness support system. Based on the stiffness requirements at different locations on the pier, high-load-bearing capacity bearings are employed, with the longitudinal stiffness of the bearings set to zero as much as possible. The aforementioned variable stiffness device is then added to distribute the stiffness, providing longitudinal stiffness and jointly achieving both vertical load-bearing and horizontal force transmission. By designing the functions of providing longitudinal stiffness and vertical load-bearing capacity separately, the design and manufacturing challenges of a single bridge bearing, which cannot simultaneously achieve high load-bearing capacity and low longitudinal stiffness, are overcome. This eliminates the need to consider whether the bearing material can achieve low longitudinal stiffness when designing the bearing's high load-bearing capacity, thus reducing the requirements for variable stiffness design. Furthermore, when designing the longitudinal stiffness of the variable stiffness device, the vertical load-bearing capacity does not need to be considered. The stiffness of the corrugated steel pipe can be designed to any desired stiffness based on actual working conditions, providing a wider range of applicability. The coordination between the bearing and the variable stiffness device reduces the difficulty of designing variable stiffness distribution between piers of different heights.

[0052] By using multiple variable stiffness devices with different adaptive deformation capabilities to coordinate deformation between the main beam, cap beam and piers, variable stiffness design of piers at different positions of the bridge can be achieved, which greatly reduces the design difficulty and makes the force transmission path clearer.

[0053] By adopting the above design, a wider range of stiffness design can be achieved by adjusting the structural parameters of the corrugated steel pipe in the variable stiffness device, which has a wider adaptability to working conditions and the variable stiffness device can be directly produced according to the stiffness requirements.

[0054] Furthermore, the application of this design scheme can increase the length of bridge sections, achieve pier clustering, improve the overall stiffness and dynamic performance of a single bridge section, reduce the number of expansion joints, and enhance driving comfort. For example, under the same conditions, if conventional bearings are used, the length of a single bridge section can generally be set to 120-150 meters. However, if this scheme's variable stiffness design with longitudinal constraints on the pier tops is adopted, the length of a single bridge section can reach 240 meters, improving the overall stiffness and dynamic performance of a single bridge section, thereby reducing the number of expansion joints and improving driving comfort.

[0055] Specifically, in step S1, the target constraint stiffness of the corresponding pier is determined K e The steps include: S11: Establish a finite element model based on the designed bridge type and size. Initially, each pier is constrained with equal stiffness, and the longitudinal bridge constraint stiffness of each pier is set to K 0, calculate the bending moment distribution, safety factor and longitudinal natural frequency of each pier; S12: Adjust the longitudinal bridge-direction constraint stiffness distribution of the main beam according to the bending moment distribution of the piers. Under the variable stiffness constraint, recalculate the bending moment distribution, safety factor, and longitudinal natural frequency of the main beam of each pier to determine whether the safety factor of each pier bottom meets the first preset requirement, whether the maximum bending moment of the pier bottom meets the second preset requirement, and whether the longitudinal natural frequency of the main beam meets the third preset requirement. S13: When the first preset requirement, the second preset requirement, and the third preset requirement are met at the same time, the longitudinal bridge constraint stiffness of each pier is output, which is used as the target constraint stiffness of the corresponding pier. K e .

[0056] In this embodiment, when determining the target constraint stiffness of each pier, K e During the calculation process, the first preset requirement is preferably: the safety factor of each pier column is greater than 1, the second preset requirement is preferably: the maximum bending moment of the pier bottom under the action of variable stiffness constraint should be reduced by at least 20% compared with the maximum bending moment of the pier bottom under the condition of equal stiffness constraint, and the third preset requirement is preferably: the longitudinal natural frequency of the main beam is greater than 0.2 Hz.

[0057] When the safety factor of each pier bottom does not meet the first preset requirement, the longitudinal bridge constraint stiffness at the corresponding position is reduced for piers with a small safety factor, and the longitudinal bridge constraint stiffness is increased for piers with a large safety factor.

[0058] If the maximum bending moment at the pier bottom does not meet the second preset requirement, the longitudinal bridge-direction constraint stiffness distribution of the main beam needs to be readjusted based on the pier bending moment distribution until an appropriate variable stiffness constraint is achieved, ensuring that both the safety factor at each pier bottom and the maximum bending moment at the pier bottom meet the preset requirements. Given a given pier size and structural resistance, the internal forces, and thus the safety factor, can be altered by changing the longitudinal bridge-direction constraint stiffness of the pier column, making the safety factor controllable. This embodiment adjusts the longitudinal bridge-direction constraint stiffness distribution of the main beam through a variable stiffness support system, reducing the maximum bending moment at the pier bottom by at least 20%, achieving the effect of peak internal force reduction. This allows for a reasonable distribution of pier column bending moments, minimizes differences in safety factors between pier columns, and reduces material redundancy and waste, ultimately saving costs and improving structural safety.

[0059] If the longitudinal natural frequency of the main beam does not meet the third preset requirement, the longitudinal bridge constraint stiffness of each pier can be increased proportionally. The finite element model can then be re-calculated to calculate the bending moment distribution of each pier, the safety factor at each pier base, and the longitudinal natural frequency of the main beam. By determining the longitudinal natural frequency of the main beam, the dynamic deformation capacity of the main beam under variable stiffness constraints can be verified.

[0060] The longitudinal natural frequency of a girder is a core parameter of a bridge's dynamic characteristics. It refers to the inherent frequency of a bridge structure's free vibration in the longitudinal direction (along the bridge). It reflects the structure's ability to resist longitudinal dynamic deformation and directly influences the bridge's response to wind loads, earthquakes, and vehicle dynamics. The longitudinal natural frequency of a girder is related to the longitudinal bridge restraint stiffness and the mass of the piers.

[0061] During calculation, different longitudinal bridge constraint stiffnesses need to be set for piers of different heights according to the different requirements of pier height, pier size, main beam form, and main beam span, so as to achieve a reasonable distribution of pier bending moments and achieve similar safety factors at the bottom of each pier, thereby achieving optimal design and improving economy. Figure 2 The adjustment process for the longitudinal bridge-direction restraint stiffness distribution of the main girder shown can calculate the required target restraint stiffness, making the design convenient and quick, with minimal computational effort. The above calculation process should be performed under the ultimate bearing capacity state.

[0062] In step S2, the design stiffness of the variable stiffness device is determined according to the following formula: K x : ; Where, n 1 is the number of beams in the main beam, n 2 is the number of variable stiffness devices, K e is the longitudinal bridge constraint stiffness of the corresponding pier, K x It is the axial stiffness of a single variable stiffness device.

[0063] In step S3, the structural parameters of the corrugated steel pipe can be determined according to the following formula. The corrugated steel pipe in this embodiment preferably adopts the following waveform: Figure 3 、 Figure 4 The sine waveform shown in the figure is used to achieve uniform deformation, smooth stress distribution, relatively low axial stiffness, but good ductility, and can dissipate energy through sufficient deformation. The structural parameters include the nominal diameter D , wave distance q , wave height h ,thickness t and length L The nominal diameter is the average of the inner and outer diameters of the corrugated steel pipe.

[0064] ; ; ; In the formula: K 1 is the axial compressive stiffness of the corrugated steel pipe, K2 is the axial compressive stiffness when the corrugated steel pipe is filled with a filling material (when the corrugated steel pipe is not filled with a filling material, the axial compressive stiffness is K 2=0), E 1 is the elastic modulus of the corrugated steel pipe material, E 2 is the elastic modulus of the filling material, t is the wall thickness of the steel pipe, v is Poisson's ratio, L is the length of the corrugated steel pipe, η is the waveform correction factor.

[0065] Furthermore, it is preferred to make the wave height h , wave distance q , nominal diameter D and wall thickness t Select appropriate values ​​from the following constraints: ; ; ; For example, the wave distance q The initial value is 0.1D, and the wave height h The initial value is 0.5 q , wall thickness t The initial value is 0.01D.

[0066] Furthermore, to increase the energy dissipation capacity under earthquake action, the structural damping can be increased under the condition that the following damping coefficient calculation formula is satisfied: ; Where: ξ 0 is the inherent damping ratio of the combination of flat steel and filling material. ξ 0 is 0.01~0.02, when filling rubber material ξ 0 takes 0.1~0.3; α is the correction coefficient of wave height to wave distance ratio, which is set between 0.4 and 0.6; β is the wall thickness correction factor, which is 0.1∼0.3; γ is the length correction coefficient, which is 0.05∼0.1; δ is the pipe diameter correction coefficient, ranging from 0.02 to 0.05; t 0 is the reference wall thickness, which is 1mm; L 0 is the reference length, which is 1m; D 0 is the reference pipe diameter, which is 1m.

[0067] Taking a single-deck continuous simply supported beam bridge as an example, the span is arranged as 8×30m. From small pile number to large pile number, the piers are numbered 1# to 7#, and the pier heights are 7.8m, 10.7m, 13.7m, 15.9m, 16.6m, 15.8m, and 12.0m respectively; the pier diameter is φ140cm, the longitudinal reinforcement is 28φ25 steel bars, the stirrup spacing is 10cm, the stirrup diameter is φ12, and the stirrup protective layer thickness is 5cm.

[0068] (1) The longitudinal bridge constraint stiffness of the main beam is generally 0~6000kN / m. In the initial state, the longitudinal bridge constraint stiffness of all piers is taken as K 0 are both 2000kN / m. By establishing finite element model analysis, such as Figure 13 As shown, it can be seen that under the equal stiffness constraint, the bending moment of the side pier is the largest, while the bending moment of the middle pier is the smallest. The calculation results of the internal forces of each pier are shown in Table 1 below: ; According to the "Highway Reinforced Concrete and Prestressed Concrete Bridge and Culvert Design Code" (JTG 3362-2018), the safety factors for each pier can be calculated, as shown in Table 2 below. It can be seen that some piers have safety factors that are too high, while others have safety factors that are too low. For a single bridge, the pier with the lowest safety factor determines the overall safety of the entire bridge. This is neither safe nor material-efficient. Therefore, the internal forces in the piers can be redistributed by adjusting the longitudinal bridge restraint stiffness at the corresponding pier columns.

[0069] ; (2) Under the condition of equal stiffness constraint, the bending moment of the edge pier is the largest, while the bending moment of the middle pier is the smallest. Therefore, the longitudinal bridge constraint stiffness of the edge pier is reduced, and the longitudinal bridge constraint stiffness of the middle pier is increased. The longitudinal bridge constraint stiffness of the single beam is adjusted to a variable stiffness, and the adjustment is: ; Under the action of variable stiffness constraint, the internal force and moment diagram of the pier is calculated again as follows: Figure 14 The internal forces of each pier are shown in Table 4 below: ; The safety factors of each pier are calculated as shown in Table 5 below: ; It can be seen that under the action of variable stiffness constraint, the safety factors of each pier are relatively more uniform, with the safety factor range of 0.59<1.0, which meets the design requirements. The minimum safety factor is also increased from 1.53 to 2.29, which improves the internal force distribution of the pier. Figure 13 、 14From the internal force and bending moment diagram of the pier shown, it is found that the maximum bending moment of the pier is reduced from -2913.5 kN·m to -1640.1 kN·m, a reduction of 43.7% (greater than 20%), so the next step can be carried out.

[0070] (3) Calculate the longitudinal natural frequency of the main beam Finite element software can be used to obtain modeling results such as Figure 15 As shown in the figure, under the above variable stiffness constraint, the longitudinal natural frequency of the main beam is 0.364Hz>0.2Hz, indicating that the main beam has good ability to resist longitudinal dynamic deformation. Therefore, the longitudinal bridge constraint stiffness in Table 3 is used as the target constraint stiffness of the corresponding pier column. K e .

[0071] (4) Determine the size of the variable stiffness device In this example, there are 11 beams and 20 variable stiffness devices. Based on the number of beams and variable stiffness devices, the axial design stiffness of each pier where the variable stiffness device is to be installed is obtained by the following formula: K x : .

[0072] The stiffness of the variable stiffness device on each pier K x The following Table 6 is drawn up: .

[0073] The corrugated steel pipe is made of Q235 steel and is not filled with any material. K 2=0. The structural parameters of the variable stiffness device are formulated according to the following formula: ; ; .

[0074] The following Table 7 is obtained: .

[0075] By designing a variable stiffness device according to the above parameters, it is possible to realize the variable stiffness design of the bridge system, adjust the longitudinal bridge-direction constraint stiffness distribution of the main beam, improve the internal force of the pier, enhance the economic benefits and optimize the dynamic performance of the main beam.

[0076] Example 2 Based on Example 1, this embodiment provides a variable stiffness support system, such as Figure 5 、 Figure 6As shown, it includes a variable stiffness device and a support. The support is used for vertical load bearing and provides bearing capacity, but does not provide longitudinal stiffness. For example, a slide support is used. The variable stiffness device is used to provide longitudinal stiffness. The variable stiffness device includes a corrugated steel tube 1, with a first connecting steel plate 2 and a second connecting steel plate 3 integrally provided at each end of the corrugated steel tube 1. The first connecting steel plate 2 is used to connect to the main beam, and the second connecting steel plate 3 is used to connect to the cap beam 5. The first connecting steel plate 2 and the second connecting steel plate 3 are arranged in parallel.

[0077] A corrugated steel tube 1 is used for main beam damping and limiting. The corrugated steel tube 1 is connected to the main beam through the first connecting steel plate 2 and to the cap beam 5 through the second connecting steel plate 3. The first connecting steel plate 2 and the second connecting steel plate 3 of the variable stiffness device are parallel when installed, so that the variable stiffness device transmits force in the axial direction. This can utilize the tensile-compression coupling effect of the corrugated steel tube 1 to prevent the occurrence of structural yield characteristics and effectively reduce the risk of beam falling. It not only achieves the rigid constraint between the main beam and the cap beam 5, but also utilizes the structural ductility of the corrugated steel tube 1 to achieve the effect of buffering and shock absorption under external loads.

[0078] In this embodiment, the wave height, wave pitch, thickness, diameter and other parameters of the corrugated steel pipe 1 can be adjusted to meet the stiffness and bearing capacity requirements. The corrugated steel pipe 1 is fully welded to the first connecting steel plate 2 and the second connecting steel plate 3.

[0079] By using the aforementioned variable stiffness device to connect the main beam and cap beam 5, the stiffness of the corrugated steel tube 1 can be changed by adjusting the corrugated parameters of the corrugated steel tube 1, such as peak height, wave pitch, and corrugation shape. The bearing capacity of the corrugated steel tube 1 can be changed by adjusting the wall thickness of the corrugated steel tube 1, thereby matching the stiffness of the variable stiffness device with the displacement dynamic response of the bridge structure, thereby better adapting to actual working conditions and achieving a more ideal vibration reduction effect. Using corrugated steel tubes to transmit the main beam load helps reduce the difficulty of stiffness matching design and can effectively solve the problem of uncontrollable stiffness of traditional limit systems.

[0080] This product adopts a variable stiffness design concept and can dynamically adjust the load size according to the displacement response. Especially under seismic excitation, it realizes the displacement-resistance positive correlation characteristic. Its restraint force is significantly enhanced with the increase of the beam displacement amplitude, forming a progressive limit protection, which can effectively suppress the risk of beam falling under extreme working conditions and ensure the safety of the overall bridge structure.

[0081] In an optional embodiment, the interior of the corrugated steel tube 1 can be filled with a flexible polymer material, such as rubber particles. Filling with a flexible material can adapt to the compression deformation of the corrugated steel tube 1 and help improve the compressive strength of the corrugated steel tube 1.

[0082] The corrugated steel pipe in this embodiment preferably adopts the following waveform: Figure 4The sinusoidal waveform shown in the figure can achieve uniform deformation, smooth stress distribution, relatively low axial stiffness, but good ductility, and can dissipate energy through sufficient deformation; U-shaped, Ω-shaped and other forms can also be used.

[0083] In this embodiment, a transverse diaphragm 6 is provided at the bottom of the main beam in a transverse direction, with a pre-embedded threaded sleeve within it. The first connecting steel plate 2 is preferably provided with a plurality of first connecting holes 21, evenly spaced circumferentially along the corrugated steel tube 1. A variable stiffness device is positioned perpendicularly to the side of the transverse diaphragm 6 away from the centerline of the cap beam, with bolts threadedly connecting the first connecting holes 21 to the threaded sleeves on the transverse diaphragm 6. The variable stiffness device is positioned longitudinally along the bridge, transferring longitudinal loads through the transverse diaphragm 6, thereby controlling the size of the main beam expansion joint and relieving thermal stress.

[0084] Furthermore, the above-mentioned variable stiffness device also includes a limit stopper 4, which is vertically arranged on the cap beam 5. The second connecting steel plate 3 is connected to the cap beam 5 via the limit stopper 4. In this embodiment, the limit stopper 4 is made of a concrete structure and is integrally connected to the cap beam 5. Preferably, a threaded sleeve is embedded in the limit stopper 4, and a plurality of second connecting holes 31 are provided on the second connecting steel plate 3. The second connecting holes 31 are evenly arranged along the circumference of the corrugated steel pipe 1 and correspond to the positions of the threaded sleeves on the limit stopper 4. The second connecting steel plate 3 is threadedly connected to the limit stopper 4 via bolts.

[0085] During use, the variable stiffness device is positioned between the main beam diaphragm 6 and the limit stop 4, with both ends bolted together to achieve rigid restraint. This provides a large force transmission area at both ends, reducing concentrated stress, ensuring more uniform force transmission, and improving load-bearing performance. Bolting the variable stiffness device securely in place facilitates installation and removal, facilitating subsequent maintenance and replacement, and minimizing maintenance costs. The variable stiffness device is positioned close to both sides of the main beam to prevent excessive stress on the diaphragm 6.

[0086] As another possible implementation method, the limit stop 4 can also adopt a metal structure with holes, which has high structural strength. The limit stop 4 can be connected by bolts. Accordingly, a connecting steel plate can be embedded in the surface of the cap beam 5, and the limit stop 4 can be fixed by welding or bolting, which helps to reduce damage to the main structure of the cap beam 5.

[0087] Example 3 Based on Example 2, this embodiment provides a bridge structure, such as Figure 6-Figure 12 As shown, it includes the bridge substructure, main beam and the above-mentioned variable stiffness support system.

[0088] The main beam includes several longitudinal beams 7, several transverse diaphragms 6 and bridge decks. The longitudinal beams 7 and transverse diaphragms 6 are arranged vertically and horizontally, with the tops flush, and jointly support and connect the bridge decks to transfer the upper load. Among them, the longitudinal beams 7 are spliced ​​along the longitudinal direction of the bridge and arranged at intervals along the transverse direction of the bridge. The two ends of the longitudinal beams 7 are overlapped on the front and rear cap beams 5 of the lower structure of the bridge, and the expansion joints of the longitudinal beams 7 correspond to the positions of the cap beams 5; the transverse diaphragms 6 are connected to the longitudinal beams 7 horizontally, and the transverse diaphragms 6 at the ends of the longitudinal beams 7 are arranged close to the expansion joints of the longitudinal beams 7. The longitudinal beams 7 can be in the form of I-shaped concrete beams, T-shaped concrete beams, small box beams or I-beams. The transverse diaphragms 6 and the longitudinal beams 7 are made of the same material.

[0089] In this embodiment, the support is provided between the main beam and the cap beam 5. Preferably, the support is fixedly connected to the cap beam 5 and is not connected to the main beam. The support is used to vertically support the main beam. The support adopts a slide support.

[0090] The variable stiffness device is arranged on the cap beam 5 at intervals along the transverse direction of the bridge, and is set along the longitudinal direction of the bridge. The first connecting steel plate 2 is bolted to the transverse partition 6, and the second connecting steel plate 3 is bolted to the cap beam 5 through the limit block 4.

[0091] As an implementable embodiment, a threaded sleeve can be pre-embedded on the transverse partition 6 and directly threadedly connected to the threaded sleeve through bolts. Alternatively, a light hole can be set on the transverse partition 6, and the bolts can be passed through the first connecting steel plate 2 and the transverse partition 6 in sequence and then locked with nuts. The above examples are not limited to the above examples.

[0092] In this embodiment, the variable stiffness devices are preferably arranged symmetrically about the centerline of the cap beam. This facilitates control of the expansion joint and prevents significant deformation of the expansion joint due to temperature stress or collision effects. The installation of two variable stiffness devices between two adjacent longitudinal beams 7 helps reduce stress concentration in the main beam and ensures more uniform force distribution.

[0093] Furthermore, the cap beam 5 is equipped with boss blocks 8 at both lateral ends to prevent the beam from falling. The boss blocks 8 are provided to limit the lateral position of the cap beam 5. At least one of the outermost longitudinal beams 7 has a transverse diaphragm 6 protruding from the outside, extending outward, which can contact the boss block 8 of the cap beam 5 in advance, providing an early warning function. The inner side of the boss block 8 is equipped with an elastic pad corresponding to the position of the transverse diaphragm 6, which also provides a certain cushioning effect.

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A bridge variable stiffness distribution design method, characterized in that: include: A variable stiffness support system is provided between the main beam and the substructure, and variable stiffness distribution between piers of different heights of the bridge is achieved through the variable stiffness support system. The variable stiffness support system includes a support (9) and a variable stiffness device. The support (9) vertically supports the main beam, and the support (9) adopts a sliding support or the support (9) is in plane contact with the main beam or the substructure; the variable stiffness device longitudinally connects the main beam and the substructure, and the variable stiffness device includes a corrugated steel pipe (1), one end of the corrugated steel pipe (1) is connected to the main beam, and the other end of the corrugated steel pipe (1) is connected to the substructure; the structural parameters of the support (9) are designed according to the bearing capacity requirements, and the stiffness of the corresponding variable stiffness device is designed according to the stiffness of the pier and the position of the pier in a bridge. The design steps of the stiffness of the variable stiffness device include: S1: Determine the target constraint stiffness of the corresponding pier column based on the height of each pier column and when the safety factor, maximum bending moment at the pier bottom and longitudinal natural frequency of the main beam all meet the preset requirements. K e ; S2: According to the target constraint stiffness of the corresponding pier K e , determine the axial design stiffness of the variable stiffness device on each pier K x ; S3: According to the axial design stiffness of the variable stiffness device on each pier K x , determine the structural parameters of the corrugated steel pipe (1).

2. The bridge variable stiffness distribution design method according to claim 1 is characterized in that: In step S1, the target constraint stiffness of the corresponding pier is determined K e The steps include: S11: Establish a finite element model based on the designed bridge type and size, and initially set the longitudinal bridge constraint stiffness of each pier to be K 0, calculate the bending moment distribution, safety factor and longitudinal natural frequency of each pier; S12: Adjust the longitudinal bridge-direction restraint stiffness distribution of the main beam based on the pier bending moment distribution, ensuring that the safety factor at each pier bottom is greater than 1, the maximum bending moment at the pier bottom is at least 20% less than that at the pier bottom under the condition of equal stiffness restraint, and the longitudinal natural frequency of the main beam is greater than 0.2 Hz. Calculate the adjusted longitudinal bridge-direction restraint stiffness of each pier column. S13: Output the longitudinal bridge constraint stiffness of each pier, which is used as the target constraint stiffness of the corresponding pier. K e .

3. The bridge variable stiffness distribution design method according to claim 1 or 2, characterized in that: The structural parameters include nominal diameter D , wave distance q , wave height h ,thickness t and length L .

4. A variable stiffness support system, characterized in that: The invention comprises a variable stiffness device, wherein the variable stiffness device comprises a corrugated steel pipe (1), and a first connecting steel plate (2) and a second connecting steel plate (3) are integrally provided at both ends of the corrugated steel pipe (1), wherein the first connecting steel plate (2) is used to connect the main beam, and the second connecting steel plate (3) is used to connect the bridge substructure, and the first connecting steel plate (2) and the second connecting steel plate (3) are arranged in parallel.

5. The variable stiffness support system according to claim 4, characterized in that: The corrugated steel pipe (1) is filled with flexible material.

6. The variable stiffness support system according to claim 4, characterized in that: The variable stiffness device further comprises a limit block (4), wherein the limit block (4) is vertically arranged on the bridge substructure, and the second connecting steel plate (3) is connected to the bridge substructure via the limit block (4).

7. A variable stiffness support system according to any one of claims 4 to 6, characterized in that: A transverse diaphragm (6) is provided at the bottom of the main beam in the transverse direction, the corrugated steel pipe (1) is located between the transverse diaphragm (6) and the limit block (4), the first connecting steel plate (2) is bolted to the transverse diaphragm (6), and the second connecting steel plate (3) is bolted to the limit block (4).

8. A variable stiffness support system according to any one of claims 4 to 6, characterized in that: It also includes a support (9), which is used to vertically support the main beam, and the support (9) adopts a slide support.

9. A bridge structure, characterized in that: It comprises a bridge substructure, a main beam and a variable stiffness support system as claimed in claim 8, wherein the main beam comprises a plurality of longitudinal beams (7) and a plurality of transverse diaphragms (6); The variable stiffness support system is located between the bridge substructure and the main beam. The variable stiffness support system is spaced apart along the transverse direction of the bridge. Each variable stiffness device is arranged along the longitudinal direction of the bridge. The first connecting steel plate (2) is connected to the transverse diaphragm (6). The second connecting steel plate (3) is connected to the bridge substructure through a limit block (4). The support (9) is in plane contact with the main beam or the bridge substructure. The support (9) is used to vertically support the main beam.

10. The bridge structure according to claim 9, characterized in that: The variable stiffness support system is symmetrically arranged about the center line of the cap beam (5).

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