A separated seismic abutment structure for high-intensity earthquake zones

Abstract

The present invention provides a separated seismic abutment structure for high-intensity earthquake zones. The seismic abutment structure includes: a pile foundation; an abutment body, installed above the pile foundation and connected to the bottom of the main beam through a seismic isolation support; a box-type back wall, installed at the rear and upper part of the abutment body and not connected to the abutment body; a limiting pull rod, one end of which is installed on the transverse diaphragm of the main beam and the other end is installed on the box-type back wall; an anti-lateral pile, installed below the box-type back wall; wherein the rear of the box-type back wall and the pile top periphery of the anti-lateral pile are filled with energy-absorbing materials; and the space between the main beam and the box-type back wall is filled with collision buffer materials. From the perspective of "functional separation to improve system reliability", the present invention separates the vertical bearing function and the horizontal bearing function of the traditional seat-type abutment, and specially designs the horizontal bearing structure, thereby solving the problem of the main beam falling due to the insufficient limiting capacity of the traditional seat-type abutment on the main beam in the longitudinal direction during an earthquake, and fully meets the seismic requirements.

Description

Technical Field

[0001] The present invention belongs to the technical field of bridge abutment seismic resistance, and in particular relates to a separated seismic-resistant bridge abutment structure for high-intensity earthquake zones. 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 soil pressure of the roadbed. The pile-based abutment is the most common type of abutment, generally consisting of a back wall, abutment body, wing walls, pile foundation and backfill (see Figure 1 a), widely used in highway bridges and urban bridges.

[0003] Previous earthquake damage has shown that in high-intensity areas, especially under near-ground vibrations, the relative displacement between the bridge piers (abutments) and beams will be very large, often leading to beam collapse. When the main beam has a large displacement away from the abutment, the abutment back wall may fail prematurely and be unable to effectively restrain the main beam displacement, resulting in uncontrolled main beam displacement or even beam collapse (see Figure 1 b), such as the Mingzu Bridge in the 1999 Jiji earthquake and the Yematan Bridge in the 2021 Maduo earthquake; when the main beam has a large displacement away from the abutment, the beam may fall due to insufficient abutment support length (see Figure 1 c).

[0004] Bridge beam collapse during an earthquake can cause enormous economic losses, severely impacting the bridge's post-earthquake function, the time and cost of post-earthquake repairs, and impacting disaster relief efforts. Existing beam collapse prevention technologies often connect the main beam and abutments with other components such as tie rods (cables), but these commonly suffer from the following problems:

[0005] (1) System vulnerability caused by functional coupling of abutments

[0006] Although current bridge seismic design specifications generally stipulate that abutments do not bear the horizontal inertia forces of the bridge superstructure, under extreme earthquakes (exceeding the design standard), due to the collision between the main beam and the abutment, as well as the various abutment anti-fall beam devices installed to prevent the beam from falling, the abutment must bear considerable seismic horizontal loads (inertia forces) of the bridge superstructure. In other words, the abutment structure must simultaneously bear the vertical loads of the bridge superstructure and the horizontal seismic loads, i.e., the vertical and horizontal load-bearing functions are coupled.

[0007] During an earthquake, the seismic horizontal loads on the bridge superstructure, borne by the abutment backwall and various abutment beam-fall protection devices, are transferred to the abutment pile foundation. Abutment pile foundations simultaneously perform multiple functions (i.e., vertical and horizontal load bearing). Damage to these components affects all dependent functions. Furthermore, pile foundations are concealed structures, making their inspection and repair difficult and costly.

[0008] (2) Insufficient resistance of abutments along the bridge direction

[0009] Under extreme earthquake conditions (especially when the earthquake motion also includes pulses) or when the bridge is long (the overall mass of the main beam is large), the strength of traditional abutment back walls and anti-beam drop devices is relatively small, resulting in relatively insufficient horizontal resistance and an inability to effectively restrain the main beam, which may cause beam drop damage.

[0010] For example, patent publication number CN101892639A discloses a method for replacing horizontal seismic anchor bolts on highway bridge abutments. This invention uses anchor bolts to connect the main beam to the abutment back wall, restraining beam displacement and preventing beam fall. Another example is patent publication number CN107190632A, which 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, both inventions suffer from the drawback that their beam-fall prevention function becomes ineffective if the main beam back wall is damaged (as evidenced by numerous earthquake damage, which often serve as a weak point in abutment failure). Another example is patent publication number CN109083000A, which discloses a modular, multi-stage, seismic bridge anti-collision and beam-fall prevention device based on BRB technology. This device uses a buckling-restrained brace (BRB) structure to connect the main beam and abutment, restraining beam displacement and preventing beam fall. However, the disadvantage is that the inertia force of the main beam will be borne entirely by the abutment, which may easily cause damage to the abutment pile foundation. Moreover, the pile foundation is a concealed project and is difficult to inspect and repair after an earthquake. Summary of the Invention

[0011] The purpose of the present invention is to provide a separated seismic abutment structure for high-intensity earthquake zones. From the perspective of "functional separation to improve system reliability", the vertical bearing function and horizontal bearing function of the traditional pedestal abutment are separated, and the horizontal bearing structure is specially designed. This solves the problem of main beam falling caused by insufficient limiting capacity of the traditional pedestal abutment on the main beam in the longitudinal direction during earthquakes, fully meeting the seismic resistance requirements.

[0012] To achieve the above object, the present invention provides the following technical solutions:

[0013] A separated seismic abutment structure for high-intensity earthquake zones, comprising: a pile foundation; an abutment body, installed above the pile foundation and connected to the bottom of the main beam through a seismic isolation support; a box-type back wall, installed above the rear of the abutment body and not connected to the abutment body; a limiting pull rod, one end of which is installed on the transverse diaphragm of the main beam and the other end is installed on the box-type back wall; anti-side piles, installed below the box-type back wall; wherein the rear of the box-type back wall and the pile top sides of the anti-side piles are filled with energy-absorbing materials; and the space between the main beam and the box-type back wall is filled with collision buffering materials.

[0014] Optionally, the pile foundation and the platform body meet the requirements of the vertical load of the superstructure and the earth pressure load of the fill.

[0015] Optionally, the box-shaped back wall is constructed by cast-in-situ method and cast together with the abutment slab.

[0016] Optionally, the limiting pull rod is provided with a limiting block at its anchoring end and a mounting gap is reserved to adapt to temperature deformation and displacement of the main beam under small earthquakes, thereby exerting the energy dissipation capacity of the seismic isolation bearing.

[0017] Optionally, the anti-side piles maintain elasticity under the inertial force of the main beam.

[0018] Optionally, the anti-lateral piles only bear horizontal loads but not vertical loads, and the pile length is relatively short.

[0019] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0020] (1) Improvement of the reliability of the abutment system:

[0021] Through the separate design of the abutment body and back wall, the vertical and horizontal bearing functions of the abutment are separated, optimizing the force transmission path of the abutment structure. The horizontal inertia force of the main beam under extreme earthquakes is borne by the box-type back wall and anti-lateral piles, rather than the pile foundation, completely avoiding damage and destruction of the hidden structure, ensuring the vertical bearing capacity of the pile foundation, and avoiding inspection and repair.

[0022] (2) Improved anti-fall beam performance:

[0023] A combination of box-type back walls, anti-side piles and limit rods is used to resist the inertia force of the bridge superstructure under extreme earthquakes, preventing the main beam from falling and causing earthquake damage in both directions away from the abutment and close to the abutment.

[0024] (3) Energy consumption classification and displacement controllable:

[0025] Energy dissipation is achieved step by step through the seismic isolation bearings, limit rods, energy-absorbing materials around the anti-lateral piles and behind the box-type back wall; by rationally designing the bearing capacity of the limit rods and anti-lateral piles, the displacement of the main beam is limited, effectively preventing the main beam from falling. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the structure of traditional seated abutment and common beam drop mode;

[0027] Figure 2 It is an elevation view of the seismic-resistant abutment structure provided by an embodiment of the present invention.

[0028] Description of Reference Numerals

[0029] 1—main beam; 2—seismic isolation bearing; 3—platform; 4—pile foundation; 5—limiting rod; 51—installation gap; 6—box-type back wall; 7—anti-side pile; 8—energy-absorbing material; 9—collision buffer material; 10—fill. DETAILED DESCRIPTION

[0030] 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 merely illustrative of the present invention and are not intended to limit the present invention. Furthermore, the same or similar reference numerals may be used in the drawings to refer to the same or similar elements in different embodiments, and descriptions of the same or similar elements in different embodiments, as well as descriptions of prior art elements, features, and effects, may be omitted.

[0031] Reference Figure 2 The embodiment of the present invention provides a separate seismic abutment structure for high-intensity earthquake zones. Specifically, the seismic abutment structure may include an abutment body 3, a pile foundation 4, a limiting tie rod 5, a box-type back wall 6, and a side-resisting pile 7.

[0032] In a specific implementation, the platform body 3 is installed above the pile foundation 4 and is also connected to the bottom of the main beam 1 through the seismic isolation bearing 2.

[0033] In some embodiments, the pile foundation 4 may be a cast-in-place friction pile. Furthermore, the platform 3 and the pile foundation 4 may be constructed using conventional methods and meet the requirements of the vertical load of the superstructure and the earth pressure load of the fill 10.

[0034] The box-shaped back wall 6 is installed above and behind the platform body 3 and is not connected to the platform body 3 to achieve structural separation.

[0035] In a specific implementation, the transverse length of the box-shaped back wall 6 is consistent with that of the abutment body 3, and can be constructed by on-site casting and cast together with the abutment slab.

[0036] 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 .

[0037] Underneath the box-shaped back wall 6 are installed lateral support piles 7. The number and length of these piles can be adjusted according to actual needs to ensure they maintain their elasticity under the inertial force of the main beam 1. Furthermore, the box-shaped back wall 6, which sits atop the piles, ensures that the piles 7 are supported in a coordinated manner.

[0038] In some embodiments, the number and length of the anti-side piles 7 can be obtained by the following process:

[0039] The first step is to establish a single pile finite element model of the lateral pile 7, in which the pile is simulated by fiber beam-column elements and the soil resistance is simulated by soil springs;

[0040] The second step is to carry out nonlinear static analysis on the model of the anti-side pile 7 to obtain the horizontal resistance-displacement curve relationship of the anti-side pile 7;

[0041] The third step is to establish and carry out the finite element model of the entire bridge, combining the horizontal resistance-displacement curve relationship of the lateral pile 7 as its macroscopic constitutive model, and carry out seismic verification.

[0042] The fourth step is to repeatedly iterate the parameters of the lateral piles 7 to finally determine the size and number of the lateral piles 7 that meet the seismic design requirements.

[0043] Specifically, the specific implementation processes of the above steps are conventional technical means in this field and will not be repeated here.

[0044] In a specific implementation, the lateral support piles 7 only bear horizontal loads and do not bear vertical loads. Compared with the pile foundation 4 of the abutment (usually friction piles), the lateral support piles 7 are relatively short.

[0045] In some embodiments, the anti-side piles 7 can be prefabricated pipe piles, cast-in-place piles, square piles, or cylindrical piles.

[0046] In a specific implementation, the rear of the box-shaped back wall 6 and the peripheral sides of the tops of the anti-side piles 7 are further filled with energy-absorbing materials 8 to provide the box-shaped back wall 6 and the anti-side piles 7 with sufficient deformation capacity to dissipate energy.

[0047] In some embodiments, the energy dissipation material 8 may be polystyrene foam (EPS).

[0048] The limiting rod 5 is used to constrain the displacement of the main beam 1 away from the abutment to prevent the beam from falling. One end of the limiting rod 5 is installed on the transverse diaphragm of the main beam 1, and the other end is installed on the box-type back wall 6.

[0049] In specific implementation, the limit rod 5 is adapted to temperature deformation and displacement of the main beam 1 under small earthquakes by setting a limit block at the anchoring end and reserving an installation gap 51, so as to give full play to the energy dissipation capacity (first-level energy dissipation) of the seismic isolation bearing 2. The limit rod 5 only plays a role when the earthquake is large.

[0050] In a specific implementation, the anchoring end represents a transverse diaphragm of the main beam 1 or a front wall of the box-type back wall 6 .

[0051] In specific implementation, the size of the installation gap 51 can be determined by performing earthquake-resistant optimization design calculations according to specific circumstances. Specifically, any known finite element analysis method in the prior art can be used to perform parameter optimization design.

[0052] The implementation of the fill 10 is the same as that of the traditional abutment structure, and realizes the function of connecting the abutment and the roadbed.

[0053] In some embodiments, the fill 10 can be constructed in two stages. The first stage is performed after the abutment pile foundation 4, the abutment body 3, and the anti-lateral piles 7 are constructed (installed). The fill is then constructed to the top of the abutment body 3. The box-type back wall 6 is then constructed. After this, the second stage is performed, and finally, the slabs for the box-type back wall 6 are cast.

[0054] In some embodiments, the fill 10 is made of graded sand that is easy to drain and is compacted layer by layer to achieve the corresponding density requirements.

[0055] By adopting the above technical solution, the seismic-resistant abutment structure provided by the embodiment of the present invention can have the following characteristics:

[0056] (1) Structural separation design: The pier body 3 is completely unconnected to the box-type back wall 6. The box-type back wall 6 is located above and behind the pier body 3. The lateral piles 7 are installed below the box-type back wall 6. The vertical load of the superstructure is borne by the pier body 3 and the pile foundation 4. When the earthquake is small, the horizontal load of the superstructure is transferred to the pier body 3 and the pile foundation 4 by the seismic isolation bearing 2. This horizontal force is relatively small. When the earthquake is large, the limit rod 5 and the main beam 1-box-type back wall 6 are triggered by the limit of the main beam 1. The large horizontal force generated is borne by the box-type back wall 6, the lateral piles 7 and the fill 10. In this way, the vertical load and horizontal load transmission paths are separated. Although the seismic isolation bearing 2 of the abutment will transfer part of the horizontal load to the pier body 3 and the pile foundation 4, this horizontal force is relatively small and does not pose a threat to the pile foundation 4.

[0057] (2) Anti-falling beam system: By connecting the transverse diaphragm of the main beam 1 and the front wall of the box-type back wall 6 through the limit rod 5, the main beam 1 can be effectively restrained from large displacement away from the abutment to prevent the beam from falling; through the lateral resistance of the box-type back wall 6, the anti-side piles 7 and the fill 10, the main beam 1 can be effectively restrained from large displacement toward the abutment to prevent the far end of the main beam 1 from falling.

[0058] (3) Multi-stage energy dissipation system: The initial displacement energy of the main beam 1 is absorbed by the seismic isolation bearing 2 (first stage energy dissipation); and as the displacement increases, the limiting rod 5 is triggered to collide with the main beam 1-box-type back wall 6, and the energy dissipation material 8 around the limiting rod 5, the anti-side pile 7 and the back of the box-type back wall 6 begins to absorb the energy of the main beam (second stage energy dissipation).

[0059] 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 separate seismic abutment structure for high-intensity earthquake zones, characterized in that: include: pile foundation; The platform body is installed above the pile foundation and connected to the bottom of the main beam through the seismic isolation bearing; A box-shaped back wall is installed on the upper rear of the platform body and is not connected to the platform body; A limiting pull rod, one end of which is mounted on the transverse diaphragm of the main beam, and the other end is mounted on the box-shaped back wall; Anti-side piles, installed below the box-shaped back wall; The rear of the box-shaped back wall and the sides around the tops of the anti-side piles are filled with energy-absorbing materials; and the space between the main beam and the box-shaped back wall is filled with collision-buffering materials.

2. The seismic abutment structure according to claim 1, characterized in that: The pile foundation and the platform body meet the requirements of the vertical load of the upper structure and the pressure load of the fill soil.

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

4. The seismic-resistant abutment structure according to claim 1, characterized in that: The limiting pull rod is provided with a limiting block at its anchoring end and a reserved installation gap to adapt to temperature deformation and displacement of the main beam under small earthquakes, thereby exerting the energy dissipation capacity of the seismic isolation support.

5. The seismic-resistant abutment structure according to claim 1, characterized in that: The anti-side piles maintain elasticity under the inertial force of the main beam.

6. The seismic-resistant abutment structure according to claim 1, characterized in that: The anti-lateral piles only bear horizontal loads but not vertical loads, and the pile length is relatively short.

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