A bridge abutment structure with a two-level limit-resistance seismic system along the bridge direction

Abstract

The present invention provides an abutment structure with a two-level limit-seismic system along the bridge direction, including an abutment body, a pile foundation, a back wall, a wing wall and a limit pile; the abutment body is installed on the pile foundation, and an assembled design is adopted between the back wall and the wing wall to control the damage position of the abutment; the limit pile is installed behind the back wall, and together with the back wall, it constitutes a two-level limit-seismic system. The present invention effectively controls the displacement of the main beam through the two-level limit system of the abutment, with the back wall as the first-level limit measure. After the connecting piece between the back wall and the abutment body is broken (i.e., the first-level limit fails), the limit pile serves as the second-level limit measure. The two limit positions provided by the present invention can adapt to the limit requirements of different earthquake intensities, realize the effective control of the displacement of the main beam along the bridge direction under an earthquake, prevent the main beam from falling, greatly ensure the traffic capacity of the bridge after the earthquake, shorten the traffic recovery time, and significantly improve the toughness of the bridge structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of bridge abutment seismic resistance, and in particular relates to a bridge abutment structure with a two-stage limit seismic resistance system in the direction of the bridge. Background Art

[0002] The abutment is the transition structure between the bridge structure and the roadbed, playing an important role in supporting the bridge superstructure and resisting the lateral earth pressure of the roadbed. The pile-based abutment is generally composed of the back wall, abutment body, wing wall, pile foundation and backfill (see Figure 1 (a) As one of the most common abutment forms in my country, it is widely used in highway bridges and urban bridges.

[0003] In previous earthquakes, the back wall of the pedestal abutment was damaged due to the collision of the main beam, and even separated from the abutment body and shifted significantly (see Figure 1 In (b), severe damage to the abutment leads to the failure of its restraint on the adjacent main beam, which in turn causes the main beam to lose control of displacement, fall or even fall. In addition, since the back wall, abutment body and wing wall are cast as a whole, damage will lead to large areas of exposed steel bars, which will increase the cost and time of repair. However, if the back wall strength is designed too high, it will cause damage to the pile foundation (see Figure 1 (c)), and pile foundation is a concealed project, which makes post-earthquake inspection and repair more difficult.

[0004] At present, the existing pedestal abutments generally have the following problems:

[0005] (1) The displacement of the main beam is uncontrollable under strong earthquakes, and the function of preventing the beam from falling cannot be effectively realized:

[0006] In existing designs for seated abutments, the strength of the backwall is not designed to account for the impact forces of the main beam. Therefore, the backwall is often a vulnerable link in the event of a main beam collision. Once the backwall is damaged, and the backfill behind the abutment is unable to provide sufficient resistance, the main beam will lose its longitudinal restraint, leading to beam collapse, resulting in significant economic losses and hindering the restoration of post-earthquake traffic.

[0007] (2) Pile foundations are likely to be damaged, increasing the difficulty and cost of post-earthquake repairs:

[0008] On the one hand, in existing designs for seated abutments, because the back wall and abutment body are connected by integral casting, the main beam inertia force is transferred from the back wall to the pile foundation, potentially damaging the pile foundation. On the other hand, increasing the back wall strength or directly transferring the main beam inertia force to the abutment body through other devices such as steel cables, anti-buckling braces, or steel blocks – measures to prevent longitudinal beam fall – will increase the stress on the abutment pile foundation and may cause damage to the pile foundation. Because pile foundations are concealed structures, the cost of inspection and repair is enormous. In-situ reconstruction also requires removing the old piles, resulting in a waste of time and cost.

[0009] (3) The damage to the abutment is large, making rapid post-earthquake repair difficult:

[0010] In existing designs for pedestal abutments, the back wall and the abutment body, as well as the back wall and wing walls, are connected by integral cast-in-place. This connection method can cause extensive, difficult-to-repair structural damage in the event of a girder collision, often requiring reconstruction.

[0011] Patent publication number CN107190632A discloses a beam-fall prevention device for highway bridges. This device uses two sets of steel strands to connect the main beam and abutment, restraining beam displacement and preventing beam fall. However, a drawback is that the device's ability to prevent beam fall is lost if the main beam's back wall is damaged (as evidenced by numerous earthquake disasters, which often serve as a weak point in bridge abutment failure).

[0012] Patent publication number CN109083000A discloses a modular, multi-stage, earthquake-resistant bridge anti-collision and beam-dropping device based on BRB technology. This invention connects the main beam and abutment using a buckling-restrained brace (BRB) structure, restraining beam displacement and preventing beam drop. However, a drawback is that the abutment bears all the inertial forces of the main beam, potentially damaging the abutment pile foundations. Furthermore, pile foundations are concealed structures, making them difficult to inspect and repair after an earthquake.

[0013] Patent document with patent publication number CN116377847A discloses a bridge abutment structure with a replaceable back wall and a construction method. The back wall of the abutment of this invention is a prefabricated component, and the connection between the abutment back wall and the abutment pedestal can be achieved through shear rods and screws. When the earthquake force exceeds the set value, the connection part is damaged by the earthquake force. This invention is convenient for assembly construction, and the back wall segments damaged by the earthquake can be quickly replaced, which can achieve rapid repair of the abutment after the earthquake. However, its disadvantage is the same as that of the traditional seat-type abutment, that is, after the back wall-abutment body connection is damaged, the abutment structure will not be able to restrain the further increase of the main beam displacement, and the purpose of preventing the beam from falling cannot be achieved.

[0014] Bridge beam collapse during an earthquake can cause enormous economic losses, severely impacting post-earthquake traffic function, the time and cost of post-earthquake repair, and impacting disaster relief efforts. Therefore, designing a practical abutment structure with a longitudinal restraint system to control main beam displacement, prevent beam collapse, and minimize abutment damage is crucial. Summary of the Invention

[0015] The purpose of the present invention is to provide an abutment structure with a two-level limit-resistance seismic system in the longitudinal direction of the bridge, so as to solve the technical problem that the traditional seat-type abutments have insufficient limit capacity for the main beam in the longitudinal direction of the bridge under earthquakes, resulting in the main beam falling.

[0016] To achieve the above object, the present invention provides the following technical solutions:

[0017] The present invention realizes a two-level limiting system along the bridge direction by using the back wall and the limiting piles installed behind the abutment; and effectively controls the damaged position of the abutment by using the assembled connection structure of the abutment body, back wall and wing wall, and facilitates post-earthquake repair.

[0018] Specifically, the present invention designs an abutment structure with a two-level limit-resistance seismic system along the bridge direction, including an abutment body, pile foundation, back wall, wing wall, limit piles, scaffolding, filling materials behind the abutment, etc. Among them, an assembled design is adopted between the abutment body, back wall and wing wall. The back wall and wing wall are prefabricated components, which are connected to the abutment body by screws. The prefabricated back wall and wing wall are not connected, and their joints are filled with waterproof material. Limit piles are installed behind the back wall and under the scaffolding. Low-strength and high-ductility energy-absorbing materials are used to fill the space between the back wall and the limit piles, and a sand cushion layer is set at the bottom for drainage. A sliding layer is also set between the limit piles and the scaffolding.

[0019] The abutment structure of the two-stage limit-seismic system along the bridge direction designed by the present invention has the following characteristics:

[0020] (1) Prefabricated design of platform body, back wall and wing wall: A threaded sleeve in the direction of the bridge is pre-embedded on the top of the platform body, and a screw hole in the direction of the bridge is reserved at the bottom of the back wall. The platform body and the back wall are connected by screws. The screw only bears tensile force during the collision of the main beam with the back wall. The force is simple and clear, and easy to calculate. Screw sleeves in the direction of the bridge are pre-embedded on both sides of the platform body, and screw holes are reserved on the wing walls. The platform body and the wing walls are connected by screws. There is no connection between the back wall and the wing wall, and the joints can be filled with waterproof material.

[0021] (2) First-level restraint measures: When the main beam is displaced significantly, the main beam and the back wall collide first. Therefore, the back wall serves as the first-level restraint measure, and its strength is determined by the strength of the screw connection between the platform and the back wall. Based on the "capacity protection principle," the number and strength of the screws connecting the platform and the back wall are designed to ensure that the pile foundation is not damaged.

[0022] (3) Second level limiting measures: When the first level limiting measures are unable to effectively limit the displacement of the main beam, the limiting piles will stop the displacement of the main beam and prevent the main beam from falling due to excessive displacement. The limiting piles are installed behind the back wall and below the slab. The limiting piles are composed of several prefabricated piles and the pile top is cast in place and provided with oil felt. The limiting piles can be prefabricated, and their diameter, number and length need to ensure that they remain elastic under the inertial force of the main beam. The cast-in-place section at the pile top ensures that the limiting piles are subjected to coordinated force. The top oil felt is located between the limiting piles and the slab, providing a sliding low-friction interface.

[0023] (4) Low-strength, high-ductility, energy-absorbing materials are used to fill the space between the limit piles and the back wall, such as polystyrene foam (EPS), fluidized solidified soil, foam concrete, etc. Due to the adjustable strength, the horizontal resistance generated by this material can be significantly greater than the ultimate passive earth pressure of traditional fill. Therefore, compared with traditional fill, the use of low-strength, high-ductility, energy-absorbing materials can significantly dissipate energy and reduce the displacement requirements of the main beam. In addition, low-strength, high-ductility, energy-absorbing materials have the characteristics of light density and no lateral pressure (self-supporting), which can reduce the dynamic earth pressure load of the bridge abutment under earthquakes.

[0024] (5) Screw connection of platform body-back wall-wing wall assembly: A threaded sleeve is embedded in the platform body, and screw holes are reserved on the back wall and wing wall. The screw is threaded at both ends, and the diameter of the middle part is smaller than that of the two ends, forming a "dog bone" shape. One end of the screw is installed in the embedded threaded sleeve on the platform body, and the other end is installed in the groove on the back wall or wing wall through a steel washer and nut. To increase the durability of the connection, the screw is preferably galvanized, and the reserved hole is filled with sealing material. In addition, the grooves on the back wall and wing wall are sealed with cement mortar.

[0025] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0026] (1) The main beam displacement is effectively controlled through the two-level limit system of the abutment: the back wall serves as the first-level limit measure. After the connection between the back wall and the abutment body is broken (i.e., the first-level limit fails), the limit piles serve as the second-level limit measure. The two limit positions of the present invention can adapt to the limit requirements of different earthquake intensities, thereby achieving effective control of the displacement of the main beam along the bridge during an earthquake, preventing the main beam from falling, greatly ensuring the bridge's post-earthquake traffic capacity, shortening the traffic recovery time, and significantly improving the bridge structure's resilience.

[0027] (2) Ensure that the abutment pile foundation is not damaged by the inertia force of the main beam: In the first-level limiting system, the connection between the abutment back wall and the abutment body is designed with reasonable strength to limit the force transmitted from the back wall to the pile foundation, ensuring that the pile foundation is not damaged. This method is also known as the "capacity protection principle." In the second-level limiting system, the inertia force of the main beam is borne by the limiting piles.

[0028] (3) The prefabricated design of the abutment, back wall, and wing wall effectively controls the location of damage to the abutment, facilitating post-earthquake repair: the back wall and wing wall are both prefabricated components, and the abutment and back wall are connected by screws, as are the abutment and wing wall connections, while there is no connection between the back wall and wing wall. This structure controls the location of damage to the prefabricated back wall, prefabricated wing wall, abutment-back wall connection screws, and abutment-wing wall screw connections. This facilitates post-earthquake repair of the damaged areas and avoids damage to the components that provide the vertical bearing capacity of the bridge structure (the abutment and pile foundation). BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the structure and common failure mode of traditional seated abutments;

[0030] Figure 2 is an exploded view of the abutment structure provided by an embodiment of the present invention;

[0031] Figure 3 is a cross-sectional view of an abutment structure provided by an embodiment of the present invention;

[0032] Figure 4 is a schematic diagram of a connector provided by an embodiment of the present invention;

[0033] Figure 5 Schematic diagram of the limit pile provided in an embodiment of the present invention.

[0034] Description of Reference Numerals

[0035] 1—platform body; 11—notch of platform body; 12—side of platform body; 2—pile foundation; 3—back wall; 31—screw hole of back wall; 32—notch of back wall; 4—wing wall; 41—screw hole of wing wall; 5—boarding; 6—filling material; 7—limit pile; 71—oil felt pad; 72—cast-in-place section; 73—prefabricated section; 8—connecting piece; 81—embedded threaded sleeve; 82—screw; 83—sealing material; 84—steel gasket; 85—nut; 86—cement mortar. DETAILED DESCRIPTION

[0036] To make the objectives, features, and beneficial effects of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described below are intended only to illustrate the present invention and are not intended to limit the present invention. Furthermore, descriptions of identical or similar elements between different embodiments, as well as descriptions of prior art elements, features, and effects, may be omitted.

[0037] Reference Figures 2 to 5 , an embodiment of the present invention provides an abutment structure with a two-level limit-seismic system along the bridge direction.

[0038] Specifically, the abutment structure includes an abutment body 1 , a pile foundation 2 , a back wall 3 , a wing wall 4 , a slab 5 , a backfill material 6 and a limit pile 7 .

[0039] In some embodiments, the abutment 1 and pile foundation 2 are constructed using conventional abutment construction methods. The pile foundation 2 is two cast-in-place friction piles. The abutment 1 is mounted on the two pile foundations 2 and constructed using a cast-in-place method.

[0040] In a specific implementation, the back wall 3 and the wing walls 4 can be installed on the platform body 1 through the connecting pieces 8 .

[0041] In some embodiments, the connector 8 may include a pre-embedded threaded sleeve 81 , a screw 82 , a sealing material 83 , a steel washer 84 , a nut 85 and cement mortar 86 .

[0042] In the specific implementation, a platform body corner cutout 11 is set at the upper rear part of the platform body 1 to form an L-shaped cross-section for installing the back wall 3; at the same time, pre-buried threaded sleeves 81 are respectively installed on the platform body corner cutout 11 and the platform body side 12 to connect the back wall 3 and the wing wall 4.

[0043] The back wall 3 and wing wall 4 can be prefabricated components using C50 concrete. During prefabrication, back wall screw holes 31 and wing wall screw holes 41 are reserved for installing screws 82 respectively, so that the back wall 3 and wing wall 4 are connected to the platform body 1 respectively through the screws 82.

[0044] In the assembly connection between the platform body 1 and the back wall 3 and wing wall 4, the screw 82 can be a galvanized screw with threads at both ends and a reduced diameter in the middle to form a "dog bone" shape to ensure that the breaking position of the screw 82 is located in the middle.

[0045] In practice, one end of the screw 82 is mounted on a pre-embedded threaded sleeve 81 of the platform body 1, and the other end is installed in a groove on the back wall 3 or wing wall 4 via a steel washer 84 and a nut 85. At the same time, the back wall screw channel 31 and the wing wall screw channel 41 are filled with sealing material 83, and the grooves on the back wall 3 and wing wall 4 are sealed with cement mortar 86 to increase durability.

[0046] There is no connection between the back wall 3 and the wing wall 4, and the joints therebetween are filled with waterproof material, such as polystyrene foam (EPS).

[0047] Back wall 3 serves as the first-level restraint along the bridge's longitudinal direction. Its failure strength depends on the strength of the screws 82 connecting back wall 3 and platform body 1. These screws 82 are evenly spaced along the transverse direction of the bridge. The diameter and number of screws 82 are determined according to the "capacity protection principle" to ensure that the pile foundation 2 is not damaged. Specifically, the equivalent yield level load of the pile foundation 2 can be determined through nonlinear static analysis, which can be used to determine the diameter, number, and strength of the screws 82.

[0048] The diameter, number and arrangement of the screws 82 connecting the wing wall 4 and the platform body 1 are determined to meet the force requirements during the construction and normal use of the wing wall 4.

[0049] In a specific implementation, the diameter and number of the screws 82 connecting the back wall 3 and the platform body 1, as well as the diameter and number of the screws 82 connecting the wing walls 4 and the platform body 1, can be achieved by conventional technical means in the prior art, which will not be repeated here.

[0050] The rear upper portion of the back wall 3 is also provided with a back wall notch 32 and formed into an L-shaped cross section for installing the buttress 5. The buttress 5 can be constructed by a cast-in-place method.

[0051] Limit piles 7 are installed behind the back wall 3 and below the slab 5, with multiple piles evenly spaced transversely across the bridge as a secondary limiting measure. The number and length of the limit piles 7 must ensure they maintain elasticity under the inertial forces of the main beam. Furthermore, because the limit piles 7 bear only horizontal loads and no vertical loads, they are relatively short compared to the abutment pile foundations 2 (typically friction piles), which bear the weight of the bridge superstructure.

[0052] In some embodiments, the number and length of the limiting piles 7 can be obtained by the following process:

[0053] The first step is to establish a single pile finite element model of the limit pile 7, in which the pile is simulated by fiber beam-column elements and the soil resistance is simulated by soil springs;

[0054] The second step is to carry out nonlinear static analysis on the model of the limit pile 7 to obtain the horizontal resistance-displacement curve relationship of the limit pile 7;

[0055] The third step is to establish and carry out a finite element model of the entire bridge, combining the horizontal resistance-displacement curve relationship of the limit pile 7 as its macroscopic constitutive model and carry out seismic verification.

[0056] The fourth step is to repeatedly iterate the parameters of the limit piles 7 to finally determine the size and number of the limit piles 7 that meet the seismic design requirements.

[0057] Specifically, the specific implementation processes of the above steps are conventional technical means in this field and will not be repeated here.

[0058] In some embodiments, the limiting pile 7 may include a prefabricated section 73 and a cast-in-place section 72 located above the prefabricated section 73. The prefabricated section 73 may be, but is not limited to, a prefabricated pile, a steel-cement-soil mixing pile, or the like.

[0059] In specific implementation, the cast-in-situ section 72 at the pile top is used to ensure that the limiting piles 7 are subjected to coordinated force.

[0060] Furthermore, an oil felt pad 71 is provided between the limiting pile 7 and the buttress plate 5 to provide a slidable low-friction interface.

[0061] A filling material 6 is also provided between the limit pile 7 and the back wall 3. The filling material 6 needs to have low strength and high ductility characteristics, and polystyrene foam (EPS), fluidized solidified soil, foam concrete, etc. can be used. Taking polystyrene foam (EPS) as an example, this material can achieve a strength of 0.1-0.7Mpa by adjusting the foaming rate and material ratio, and the compressive strain can be as high as 0.5. Due to the adjustable strength, the horizontal resistance generated by the material can be significantly greater than the ultimate passive earth pressure of traditional fill. Therefore, compared with traditional fill, the use of low-strength and high-ductility energy-absorbing materials can significantly dissipate energy and reduce the displacement requirements of the main beam. In addition, low-strength and high-ductility energy-absorbing materials have the characteristics of light density and no lateral pressure (self-supporting), which can reduce the dynamic earth pressure load of the abutment under earthquakes.

[0062] A sand cushion layer is also provided at the bottom of the filling material 6 and the cast-in-situ section 72 of the limit pile 7 for drainage.

[0063] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A bridge abutment structure with a two-stage limit seismic resistance system along the bridge direction, characterized in that: The bridge comprises a platform body (1), a pile foundation (2), a back wall (3), a wing wall (4), a slab (5), a filling material (6) and a limit pile (7); the platform body is installed on the pile foundation, and an assembled design is adopted between the back wall and the wing wall to control the damage position of the abutment; the limit pile (7) is installed behind the back wall, and forms a two-level limit anti-seismic system with the back wall; The top of the platform body (1) is pre-buried with a threaded sleeve in the direction of the bridge, and the bottom of the back wall (3) is reserved with a screw hole (31) in the direction of the bridge, and the platform body (1) and the back wall (3) are connected by screws (82); the screws (82) only bear tension during the process of the main beam colliding with the back wall (3); transverse screw sleeves (81) are pre-buried on both sides of the platform body (1), and screw holes (41) are reserved on the wing wall (4), and the platform body (1) and the wing wall (4) are connected by screws; there is no connection between the back wall (3) and the wing wall (4), and the joints are filled with waterproof material (6); When the main beam is displaced significantly, the main beam and the back wall will collide first. The back wall serves as the first level of restraint, and its strength is determined by the strength of the screws connecting the platform body and the back wall. The number and strength of the screws connecting the platform body and the back wall are designed to ensure that the pile foundation is not damaged. When the first-level limiting measures cannot effectively limit the displacement of the main beam, the limiting pile (7) will stop the displacement of the main beam to prevent the main beam from being displaced too much and falling; the limiting pile (7) is installed behind the back wall and below the slab (5); the limiting pile (7) is composed of a number of prefabricated piles and the pile top is cast in situ and provided with oil felt (71); the limiting pile (7) is prefabricated, and its diameter, number and length ensure that it maintains elasticity under the inertial force of the main beam; the pile top cast in situ section of the limiting pile (7) ensures that the limiting pile is subjected to coordinated force; the top oil felt (71) is located between the limiting pile (7) and the slab (5) to provide a sliding low-friction interface.

2. The abutment structure according to claim 1, characterized in that: The upper rear part of the platform body is provided with a platform body corner; the platform body corner and the platform body side are respectively installed with embedded threaded sleeves to connect screws respectively; the back wall and the wing walls are respectively provided with back wall screw holes and wing wall screw holes to install the screws respectively; the back wall and the wing walls are respectively connected to the platform body through the screws.

3. The abutment structure according to claim 2, characterized in that: The back wall and the wing wall are also respectively provided with grooves; one end of the screw is installed in the embedded threaded sleeve, and the other end is installed in the groove through a steel washer and a nut.

4. The abutment structure according to claim 3, characterized in that: The back wall screw channel and the wing wall screw channel are filled with sealing material; the groove is sealed with cement mortar.

5. The abutment structure according to claim 2 or 3, characterized in that: The screw rod is a galvanized screw rod, and threads are arranged at both ends thereof, and the diameter of the middle portion is smaller than that of the two ends.

6. The abutment structure according to claim 2 or 3, characterized in that: The screws connecting the back wall and the platform body are arranged along the transverse direction of the bridge, and the diameter and number of the screws are designed based on the capacity protection principle to ensure that the pile foundation is not damaged; the diameter, number and arrangement of the screws connecting the wing walls and the platform body are designed to meet the force requirements during the construction and normal use of the wing walls.

7. The abutment structure according to claim 1, characterized in that: The upper rear part of the back wall is provided with a back wall notch for installing the scaffolding; the limit piles are installed behind the back wall and below the scaffolding, and multiple are arranged along the transverse direction of the bridge; the limit piles include a prefabricated section and a cast-in-place section located above the prefabricated section, and the cast-in-place section is used to ensure that the limit piles are subjected to coordinated force; an oil felt pad is also provided between the cast-in-place section and the scaffolding to provide a slidable low-friction interface.

8. The abutment structure according to claim 7, characterized in that: The number and length of the limit piles are designed for the purpose of ensuring that they maintain elasticity under the inertial force of the main beam; and the limit piles only bear horizontal loads and do not bear vertical loads.

9. The abutment structure according to claim 7, characterized in that: Filling material is provided between the limit piles and the back wall; a sand cushion layer is provided between the filling material and the bottom of the cast-in-place section for drainage.

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