Separated anti-seismic bridge abutment structure in high-intensity earthquake area

Abstract

The invention provides a separated anti-seismic bridge abutment structure in a high-intensity earthquake area. The anti-seismic bridge abutment structure comprises a pile foundation; the platform body is mounted above the pile foundation and is connected to the lower part of the main beam through a seismic mitigation and isolation support; the box-type back wall is mounted at the rear upper part of the platform body and is not connected with the platform body; one end of the limiting pull rod is mounted on the transverse partition plate of the main beam, and the other end is mounted on the box-type back wall; the anti-lateral pile is mounted below the box type back wall; the rear portion of the box type back wall and the peripheral sides of the pile tops of the anti-lateral piles are filled with energy dissipation materials. Collision buffering materials are filled between the main beam and the box type back wall. From the perspective of'function separation to improve system reliability ', the vertical bearing function and the horizontal bearing function of a traditional seat-type bridge abutment are separated, and the horizontal bearing structure is specially designed, so that the problems of girder falling and the like caused by insufficient limiting capability of the traditional seat-type bridge abutment on a girder in the longitudinal bridge direction in an earthquake are solved, and the safety of the system is improved. And the anti-seismic requirement is fully met.

Description

Technical Field

[0001] The present invention belongs to the technical field of seismic design of abutments, and particularly relates to a separated seismic abutment structure in high-intensity earthquake areas. Background Art

[0002] An abutment is a transitional structure between a bridge structure and a roadbed, playing an important role in supporting the upper structure of the bridge and resisting the lateral earth pressure of the roadbed. A seated pile foundation abutment is a common form of abutment, generally consisting of a back wall, a pier body, wing walls, a pile foundation, and backfill behind the abutment, etc. (see Figure 1 a), and is widely used in highway bridges and urban bridges.

[0003] Previous earthquake damage shows that in high-intensity areas, especially under near-field ground motions, the relative displacement between the pier (abutment) and the beam of the bridge will be very large, often leading to the occurrence of beam-drop earthquake damage. When the main beam has a large displacement away from the abutment, the back wall of the abutment may fail prematurely and cannot effectively restrain the displacement of the main beam, resulting in out-of-control displacement of the main beam and even beam-drop (see Figure 1 b), such as Mingzu Bridge in the Chi-Chi earthquake in , and Yematan Bridge in the Maduo earthquake in 2021; when the main beam has a large displacement away from the abutment, beam-drop may also occur due to insufficient support length of the abutment (see Figure 1 c).

[0004] The "beam-drop" of bridges during earthquakes will cause huge economic losses, seriously affecting the post-earthquake traffic function of bridges, the post-earthquake repair time and cost, and disaster relief. Existing anti-beam-drop technologies mostly connect the main beam and the abutment through other components such as cables, but generally have the following problems: (1) Functional coupling of the abutment leads to system vulnerability Although in the current bridge seismic design code, the abutment generally does not bear the horizontal inertial force of the upper structure of the bridge, under extreme earthquake actions (higher than the design standard), due to the collision between the main beam and the abutment, and various anti-beam-drop devices installed for the purpose of preventing beam-drop, the abutment needs to bear a considerable amount of seismic horizontal load (inertial force) of the upper structure of the bridge. That is to say, the abutment structure needs to bear both the vertical load and the seismic horizontal load of the upper structure of the bridge, namely the coupling of the vertical bearing function and the horizontal bearing function.

[0005] During an earthquake, the seismic horizontal load of the upper structure of the bridge borne by the back wall of the abutment and various anti-beam-drop devices of the abutment will be transmitted to the pile foundation of the abutment. The pile foundation of the abutment is responsible for multiple functions (i.e., vertical bearing function and horizontal bearing function) at the same time. Once this component is damaged, all functions relying on it will be affected. And the pile foundation belongs to a hidden project, and the difficulty and cost of its inspection and repair are very high.

[0006] (2) Insufficient resistance of the abutment in the longitudinal direction of the bridge In the case of extreme earthquake actions (especially when the ground motion contains pulses) or when the bridge length is relatively long (the overall mass of the main girder is relatively large), the strength of the traditional abutment back wall and the anti-falling beam device is relatively small, resulting in relatively insufficient horizontal resistance, unable to effectively restrain the main girder, and may lead to the seismic damage of the falling beam.

[0007] For example, the patent document with the patent publication number CN101892639A discloses an anchoring installation method for replacing the horizontal seismic anchor rod of a highway bridge abutment. The invention uses an anchor rod to connect the main girder and the abutment back wall to achieve the purpose of restraining the displacement of the main girder and preventing the falling beam. Another example is that the patent document with the patent publication number CN107190632A discloses a highway bridge anti-falling beam limit device. The invention connects the main girder and the abutment together through two sets of steel strand connection mechanisms to achieve the purpose of restraining the displacement of the main girder and preventing the falling beam. However, the disadvantage of both of these inventions is that once the back wall of the main girder is damaged (a large number of seismic damages show that the back wall is usually the weak point of the abutment failure), their functions of preventing the main girder from falling will fail. Another example is that the patent document with the patent publication number CN109083000A discloses a combined multi-level seismic bridge anti-collision and anti-falling beam device based on BRB technology. The invention connects the main girder and the abutment together through a buckling-restrained brace structure (BRB) to achieve the purpose of restraining the displacement of the main girder and preventing the falling beam. But the disadvantage is that the inertial force of the main girder will be entirely borne by the abutment, which is likely to cause damage to the abutment pile foundation, and the pile foundation belongs to hidden works and is difficult to inspect and repair after the earthquake. Summary of the Invention

[0008] The purpose of the present invention is to provide a separated seismic abutment structure in a high-intensity seismic area. From the perspective of "separating functions to improve system reliability", the vertical load-bearing function and the horizontal load-bearing function of the traditional seat-type abutment are separated, and the horizontal load-bearing structure is specially designed to solve the problems such as the insufficient ability of the traditional seat-type abutment to limit the main girder in the longitudinal direction of the bridge during an earthquake, resulting in the falling beam of the main girder, etc., and fully meets the seismic requirements.

[0009] To achieve the above purpose, the present invention provides the following technical solutions: A separated seismic abutment structure in a high-intensity seismic area, comprising: a pile foundation; a pier body, installed above the pile foundation and connected to the lower part of the main girder through a seismic isolation and energy dissipation bearing; a box-shaped back wall, installed at the rear upper part of the pier body and having no connection with the pier body; a limiting tie rod, one end of which is installed on the diaphragm of the main girder and the other end is installed on the box-shaped back wall; a lateral resistance pile, installed below the box-shaped back wall; wherein, the rear of the box-shaped back wall and the circumferential side of the pile top of the lateral resistance pile are filled with energy dissipation materials; a collision buffer material is filled between the main girder and the box-shaped back wall.

[0010] Optionally, the pile foundation and the pier body meet the requirements of the vertical load of the superstructure and the earth pressure load of the fill.

[0011] Optionally, the box-shaped back wall is constructed by in-situ casting and cast together with the approach slab of the abutment.

[0012] Optionally, the limit tie rod is provided with a limit block at its anchorage end and an installation gap is reserved to adapt to temperature deformation and the displacement of the main girder under minor earthquakes, and the energy dissipation capacity of the seismic isolation and dissipation bearing is exerted.

[0013] Optionally, the lateral resistance piles remain elastic under the action of the inertial force of the main girder.

[0014] Optionally, the lateral resistance piles only bear horizontal loads and do not bear vertical loads, and the pile length is relatively short.

[0015] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: (1) Improvement of the reliability of the abutment system: Through the separated design of the abutment body and the back wall, the vertical load-bearing function and the horizontal load-bearing function of the abutment are separated, and the force transmission path of the abutment structure is optimized; the horizontal inertial force of the main girder under extreme earthquakes is borne by the box-shaped back wall and the lateral resistance piles, rather than the pile foundation, completely avoiding the damage and failure of this concealed structure, ensuring the vertical load-bearing capacity of the pile foundation, and at the same time avoiding inspection and repair.

[0016] (2) Improvement of the anti-falling beam performance: The form of combining the box-shaped back wall, the lateral resistance piles and the limit tie rod is adopted to resist the inertial force of the superstructure of the bridge under extreme earthquakes and prevent the main girder from suffering from falling beam disasters in two directions of moving away from and approaching the abutment.

[0017] (3) Energy dissipation grading and displacement controllability: The energy is dissipated step by step through the seismic isolation and dissipation bearing, the limit tie rod, the energy dissipation materials on the periphery of the lateral resistance piles and behind the box-shaped back wall; by reasonably designing the load-bearing capacity of the limit tie rod and the lateral resistance piles, the displacement of the main girder is limited to effectively prevent the main girder from falling. Description of the Drawings

[0018] Figure 1 shows the structure of a traditional seat-type abutment and common falling beam modes; Figure 2 is the elevation view of the seismic-resistant abutment structure provided by the embodiment of the present invention.

[0019] Description of the Reference Numerals 1 - Main girder; 2 - Seismic isolation and dissipation bearing; 3 - Abutment body; 4 - Pile foundation; 5 - Limit tie rod; 51 - Installation gap; 6 - Box-shaped back wall; 7 - Lateral resistance piles; 8 - Energy dissipation materials; 9 - Collision buffer materials; 10 - Fill soil. Detailed Embodiments

[0020] To make the objectives, features, and beneficial effects of the present invention more apparent and understandable, the following provides a detailed description of the specific embodiments of the present invention with reference to the accompanying drawings. It can be understood that the specific embodiments described below are only for explaining the present invention and are not intended to limit the present invention. Moreover, in the drawings, the same or similar reference numerals may be used to refer to the same or similar elements in different embodiments, and the descriptions of the same or similar elements in different embodiments and the descriptions of the prior art elements, features, effects, etc. may also be omitted.

[0021] Referring to Figure 2 , an embodiment of the present invention provides a separated seismic abutment structure in a high-intensity seismic area. Specifically, the seismic abutment structure may include a abutment body 3, a pile foundation 4, a limit tie rod 5, a box-shaped back wall 6, and a lateral resistance pile 7.

[0022] In a specific implementation, the abutment body 3 is installed above the pile foundation 4 and is also connected to the lower part of the main beam 1 through a seismic isolation and energy dissipation bearing 2.

[0023] In some embodiments, the pile foundation 4 may adopt a cast-in-place friction pile. Moreover, the abutment body 3 and the pile foundation 4 can be constructed according to traditional methods and meet the requirements of the vertical load of the superstructure and the earth pressure load of the fill soil 10.

[0024] The box-shaped back wall 6 is installed at the upper rear part of the abutment body 3 and is not connected to the abutment body 3 to achieve structural separation.

[0025] In a specific implementation, the transverse bridge length of the box-shaped back wall 6 is the same as that of the abutment body 3, and it can be constructed by the in-situ casting method and cast together with the abutment slab.

[0026] In a specific implementation, a collision buffer material 9 is also filled between the box-shaped back wall 6 and the main beam 1 to reduce the collision force and avoid damage to the box-shaped back wall 6.

[0027] The lateral resistance pile 7 is installed below the box-shaped back wall 6. The number and length of the piles of the lateral resistance pile 7 can be adjusted according to actual needs to ensure that the lateral resistance pile 7 can remain elastic under the action of the inertial force of the main beam 1. At the same time, the box-shaped back wall 6 at the top of the lateral resistance pile 7 ensures that each lateral resistance pile 7 is stressed synergistically.

[0028] In some embodiments, the number and length of the piles of the lateral resistance pile 7 can be obtained through the following process: The first step is to establish a single-pile finite element model of the lateral resistance pile 7, in which the pile is simulated by a fiber beam-column element and the soil resistance is simulated by a soil spring; The second step is to carry out a nonlinear static analysis on the model of the lateral resistance pile 7 to obtain the relationship between the horizontal resistance and displacement curve of the lateral resistance pile 7; The third step is to establish and carry out a full-bridge finite element model, and combine the relationship between the horizontal resistance and displacement curve of the lateral resistance pile 7 as its macroscopic constitutive relationship to carry out seismic checking calculations; In the fourth step, the parameters of the lateral resistance piles 7 are repeatedly iterated, and finally the dimensions and quantities of the lateral resistance piles 7 that meet the seismic design requirements are determined.

[0029] Specifically, the specific implementation processes of the above steps are all conventional technical means in the art, and will not be elaborated here.

[0030] In specific implementation, the lateral resistance piles 7 only bear horizontal loads and do not bear vertical loads. Compared with the pile foundation 4 of the abutment (usually a friction pile), the pile length of the lateral resistance piles 7 is relatively short.

[0031] In some embodiments, the lateral resistance piles 7 can be precast pipe piles, or cast-in-place piles, or square piles, or cylindrical piles.

[0032] In specific implementation, energy-dissipating materials 8 are also filled behind the box-shaped back wall 6 and around the top of the lateral resistance piles 7 to provide sufficient deformation capacity for the box-shaped back wall 6 and the lateral resistance piles 7 to dissipate energy.

[0033] In some embodiments, the energy-dissipating materials 8 can be polystyrene foam (EPS).

[0034] The limiting tie rod 5 is used to restrain the displacement of the main beam 1 away from the abutment direction and prevent the beam from falling. One end of it is installed on the diaphragm of the main beam 1, and the other end is installed on the box-shaped back wall 6.

[0035] In specific implementation, the limiting tie rod 5 is provided with a limiting block at the anchoring end and a mounting gap 51 is reserved to adapt to the temperature deformation and the displacement of the main beam 1 under minor earthquakes, so as to give full play to the energy-dissipating capacity of the seismic isolation and energy dissipation bearing 2 (primary energy dissipation). The limiting tie rod 5 only plays a role when the earthquake is relatively large.

[0036] In specific implementation, the anchoring end refers to the diaphragm of the main beam 1 or the front wall of the box-shaped back wall 6.

[0037] In specific implementation, the size of the mounting gap 51 can be determined by carrying out seismic optimization design calculations according to specific conditions. Specifically, any known finite element analysis method in the prior art can be used for parameter optimization design.

[0038] The implementation method of the fill soil 10 is the same as that of the traditional abutment structure, realizing the function of connecting the abutment and the roadbed.

[0039] In some embodiments, the fill soil 10 can be filled in two times. After the pile foundation 4, the abutment body 3 and the lateral resistance piles 7 of the abutment are constructed (installed), the first filling is carried out until the top height of the abutment body 3. Immediately after that, the box-shaped back wall 6 is constructed. After completion, the second fill soil is carried out, and finally the slab of the box-shaped back wall 6 is poured.

[0040] In some embodiments, the backfill 10 is made of well-drained graded sand and is compacted layer by layer to meet the corresponding density requirements.

[0041] By adopting the above technical solutions, the seismic abutment structure provided by the embodiments of the present invention may have the following characteristics: (1) Structural separation design: There is no connection between the abutment body 3 and the box-shaped back wall 6. The box-shaped back wall 6 is located above and behind the abutment body 3. Anti-lateral piles 7 are installed below the box-shaped back wall 6. The vertical loads of the superstructure are borne by the abutment body 3 and the pile foundation 4. When the earthquake is relatively small, the horizontal loads of the superstructure are transmitted by the seismic isolation and energy dissipation bearing 2 to the abutment body 3 and the pile foundation 4, and this horizontal force is relatively small. When the earthquake is relatively large, due to the limit on the main beam 1, the limit tie rod 5 and the collision between the main beam 1 and the box-shaped back wall 6 are triggered, and the relatively large horizontal force generated thereby is borne by the box-shaped back wall 6, the anti-lateral piles 7 and the backfill 10. Thus, the separation of the transmission paths of the vertical and horizontal loads is realized. Although the seismic isolation and energy dissipation bearing 2 of the abutment will transmit part of the horizontal load to the abutment body 3 and the pile foundation 4, this horizontal force is relatively small and does not pose a threat to the pile foundation 4.

[0042] (2) Anti-falling beam system: By connecting the diaphragm of the main beam 1 and the front wall of the box-shaped back wall 6 with the limit tie rod 5, the large displacement of the main beam 1 away from the abutment can be effectively restricted, preventing the falling of the beam. Through the lateral resistance of the box-shaped back wall 6, the anti-lateral piles 7 and the backfill 10, the large displacement of the main beam 1 towards the abutment can be effectively restricted, preventing the distal end of the main beam 1 from falling.

[0043] (3) Multi-level energy dissipation system: The initial displacement energy of the main beam 1 is absorbed by the seismic isolation and energy dissipation bearing 2 (the first-level energy dissipation); and as the displacement increases, the limit tie rod 5 and the collision between the main beam 1 and the box-shaped back wall 6 are triggered, and the energy dissipation materials 8 on the periphery of the limit tie rod 5 and the anti-lateral piles 7 and behind the box-shaped back wall 6 start to absorb the energy of the main beam (the second-level energy dissipation).

[0044] 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 protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. A separated seismic abutment structure in a high-intensity seismic area, characterized in that Comprising: Pile foundation; Pier body, installed above the pile foundation and connected to the lower part of the main girder through a seismic isolation and energy dissipation bearing; Box-shaped back wall, installed at the rear upper part of the pier body and not connected to the pier body; Limit tie rod, one end installed on the diaphragm of the main girder and the other end installed on the box-shaped back wall; Lateral resistance pile, installed below the box-shaped back wall; Wherein, energy dissipation materials are filled at the rear of the box-shaped back wall and around the pile top of the lateral resistance pile; collision buffer materials are filled between the main girder and the box-shaped back wall.

2. The aseismic abutment structure according to claim 1, characterized in that The pile foundation and the pier body meet the requirements of the vertical load of the superstructure and the earth pressure load of the fill.

3. The aseismic abutment structure according to claim 1, characterized in that, The box-shaped back wall is constructed by in-situ casting and cast together with the abutment slab.

4. The aseismic abutment structure according to claim 1, characterized in that, The limit tie rod sets a limit block at its anchoring end and reserves an installation gap to adapt to the temperature deformation and the displacement of the main girder under minor earthquakes, and exerts the energy dissipation capacity of the seismic isolation and energy dissipation bearing.

5. The aseismic abutment structure according to claim 1, characterized in that, The lateral resistance pile remains elastic under the action of the inertial force of the main girder.

6. The aseismic abutment structure according to claim 1, wherein, The lateral resistance pile only bears horizontal loads and does not bear vertical loads, and the pile length is relatively short.

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