A restorable ductile structural pier for railway bridge

Abstract

The invention discloses a restorable ductile structural pier of a railway bridge, comprising a concrete pier body, the pier body comprising an outer steel cage and an inner steel cage, the outer steel cage comprising a first longitudinal bar and a first hoop, the first longitudinal bar being arranged along the entire length of the pier body, a gap being provided between the bottom surface of the outer steel cage and the top surface of the pedestal, a mortar cushion being arranged in the gap, the inner steel cage comprising a second longitudinal bar and a second hoop, the bottom of the inner steel cage extending into the pedestal. With the structure, under normal operation of the railway bridge and the action of a small earthquake, the pier can meet the stiffness requirements of normal operation of the train, under the action of a large earthquake, a plastic hinge is formed at the bottom of the pier to dissipate the seismic energy, and the ductile seismic design of the pier is realized, the ductile deformation capacity and seismic energy dissipation capacity of the traditional railway pier are improved, the mortar cushion can be quickly repaired after the earthquake, the pier is restored to the size and stiffness before the earthquake, the driving safety after the earthquake is ensured, and precious time is gained for the rescue after the earthquake.

Description

Technical Field

[0001] The invention relates to the technical field of bridge engineering, and in particular to a restorable ductile structural pier of a railway bridge. Background Art

[0002] Many studies have been conducted at home and abroad on the ductility performance, resilience model, performance index, and damage and destruction of reinforced concrete bridge piers under earthquakes, and a large number of research results have been achieved. However, these studies are mainly aimed at highway bridge piers with relatively small pier column stiffness. For railway bridge piers, in order to meet the normal operation needs of railways, the specifications stipulate that the stiffness requirements of railway bridge piers are relatively large, often dozens of times that of highway bridge piers. The cross-sectional dimensions of the piers are also relatively large. Under the action of earthquakes, they often remain in an elastic state and it is difficult to enter a ductile state, resulting in a large seismic force distributed during an earthquake, and a large seismic force transmitted to the pile foundation, which indirectly increases the difficulty of pile foundation design. In addition, once a railway bridge is damaged in an earthquake, such as cracking, tilting deformation, and shearing of the piers, it is basically difficult to repair it, and new piers can only be rebuilt. Therefore, it is difficult and time-consuming to repair railway bridge piers after earthquake damage, which makes post-earthquake disaster relief very difficult and it is impossible to achieve post-disaster operation of the bridge in a short time, which seriously affects post-earthquake rescue work. Summary of the invention

[0003] The purpose of the present invention is to provide a restorable ductile structural pier for railway bridges to address the above-mentioned shortcomings of railway bridge piers in the prior art, such as high rigidity, difficulty in entering a ductile state under earthquake action, poor ductile deformation capacity, difficulty in repairing once damaged and long repair period.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A restorable ductile structural pier of a railway bridge comprises a concrete pier body, wherein the pier body comprises an outer ring steel cage and an inner ring steel cage, wherein the outer ring steel cage comprises a first longitudinal bar and a first stirrup, wherein the first longitudinal bar is arranged along the entire length of the pier body, wherein a gap is provided between the bottom surface of the outer ring steel cage and the top surface of the pedestal, wherein a mortar cushion layer is provided in the gap, wherein the inner ring steel cage comprises a second longitudinal bar and a second stirrup, wherein the bottom of the inner ring steel cage extends into the pedestal.

[0006] The invention discloses a restorable ductile structural pier for a railway bridge, wherein an outer ring steel cage and an inner ring steel cage are provided in the concrete pier body, and the design parameters such as the number of steel bars, steel bar diameter, steel bar strength, the shrinkage distance of the inner ring steel cage relative to the outer ring steel cage, cushion thickness, cushion strength, cushion area, etc. of the outer ring steel cage and the inner ring steel cage are designed according to the ductility and stiffness requirements of the pier under different earthquake intensities, the lower part of the inner ring steel cage extends into the pedestal for anchoring, and the upper part is deep in the pier body. The anchoring depth required by the current specification is sufficient. The inner ring steel cage is set inward, so that the yield strength is reduced while the elastic stiffness of the pier bottom section remains unchanged, thereby improving the ductile deformation capacity of the pier. The outer ring steel cage is set in the pier body, and there is a gap between its bottom surface and the top surface of the cap, that is, the lower part of the outer ring steel cage does not extend into the cap, and the gap is filled with the mortar cushion layer, which is connected with the concrete part to form a dense pier body. The mortar cushion layer does not contain gravel and has high compressive strength, so as to meet the rigidity requirements of normal operation. Under the action of earthquake, when the mortar cushion layer at the bottom of the pier cracks, the cross-sectional size of the pier bottom is reduced, the rigidity is reduced, and the pier forms a plastic hinge, so that the pier swings and dissipates energy to reduce the seismic response. As the pier swings under the action of reciprocating earthquake loads, the mortar cushion layer will be crushed, but the cross-sectional area where the inner ring steel cage is located can play the role of a plastic hinge, effectively controlling the damage of the pier at the plastic hinge part of the pier bottom, improving the seismic energy dissipation capacity of the pier, and ensuring that the pier does not collapse. The bearing capacity and deformation energy dissipation capacity of the bridge plastic hinge can be controlled according to parameter design, so that the seismic force transmitted from the superstructure to the pier bottom will be significantly reduced, and the seismic force on the pile foundation under the action of a large earthquake will be reduced, thereby reducing the amount of engineering work for the pile foundation when designing the pile foundation and saving construction costs. After the earthquake, the remaining part of the mortar cushion layer can be chiseled off and the mortar can be re-injected to form a new mortar cushion layer. Under the normal operation of the railway bridge and the action of small earthquakes, the piers of this device can maintain sufficient rigidity to meet the rigidity requirements of normal train operation. Under the action of small earthquakes, the piers maintain elasticity and are not damaged. Under the action of large earthquakes, the ultimate bearing capacity of the piers is reduced, which effectively reduces the seismic force borne by the piers, indirectly reduces the seismic force of the pile foundation, and protects the pile foundation. At the same time, the rigidity of the cross-section above the pier bottom is relatively large, and only the cross-section at the pier bottom cushion layer reduces the rigidity due to the cracking of the mortar cushion layer, so that a plastic hinge is formed at the pier bottom, causing ductile deformation of the pier, effectively dissipating seismic energy, realizing the ductile seismic design of the pier, and improving the ductile deformation capacity and seismic energy dissipation capacity of traditional railway piers. After the earthquake, the pier cross-section can be quickly repaired by re-pouring mortar, so that the pier can be restored to the size and rigidity before the earthquake, ensuring the driving safety of the railway bridge after the earthquake, and winning precious time for post-earthquake rescue work.

[0007] Preferably, the bottom of the first longitudinal reinforcement has a bending section, and the gap is between the bottom surface of the bending section and the top surface of the support platform.

[0008] Further preferably, the thickness of the gap is adapted to the sum of the thickness of the protective layer and the thickness of the mortar cushion layer, the thickness of the mortar cushion layer is 2cm-10cm, and the mortar cushion layer is arranged along the outer side of the protective layer of the inner circle steel cage.

[0009] That is, the width of the mortar cushion layer extends from the outer side of the protective layer of the inner ring steel cage to the outer side surface of the pier body, the top surface of the mortar cushion layer is connected to the bottom protective layer of the outer ring steel cage, and the bottom surface of the mortar cushion layer is connected to the top surface of the pedestal, which is beneficial to the reinforcement design and post-earthquake repair of the pier body.

[0010] Further preferably, the bending section is a 90-degree hook.

[0011] The above-mentioned arrangement is beneficial to improving the stress-bearing performance of the bending section and improving the stability of the section above the pier bottom under earthquake action.

[0012] Preferably, the pier body has a hollow cavity, the hollow cavity has a chamfer, and oblique ribs are provided at the chamfer.

[0013] The above-mentioned arrangement method is adopted, that is, the pier body adopts a hollow structure, which effectively saves materials, reduces the deadweight of the pier, reduces costs, and improves rigidity. The diagonal reinforcement is arranged in the solid part of the chamfer, which is beneficial to improving the stress performance of the pier body at the variable cross-section.

[0014] Further preferably, the anchoring depth of the inner ring steel cage in the pier body is adapted to the height of the solid section below the hollow cavity.

[0015] Further preferably, the outer ring steel cage comprises at least two layers of the first longitudinal bars, a plurality of the first stirrups are evenly arranged on each layer of the first longitudinal bars, first tension bars are connected between the innermost layer of the first longitudinal bars and the outermost layer of the first longitudinal bars, and the first tension bars are evenly arranged along the length direction of the first longitudinal bars.

[0016] The above arrangement is adopted to ensure the stress-bearing performance of the hollow thin-walled structure, and the number of rows of the first longitudinal reinforcement is determined according to design requirements.

[0017] Further preferably, the inner circle steel cage comprises at least two layers of the second longitudinal bars, a plurality of the second stirrups are evenly arranged on each layer of the second longitudinal bars, second tension bars are connected between the innermost layer of the second longitudinal bars and the outermost layer of the second longitudinal bars, and the second tension bars are evenly arranged along the length direction of the second longitudinal bars.

[0018] Further preferably, a third tensioning reinforcement is connected between the second stirrup of the innermost layer and the first stirrup of the outermost layer.

[0019] Further preferably, the solid section below the hollow cavity further comprises staggered fourth tie bars, and both ends of the fourth tie bars are connected to the outermost layer of the first hoop bars.

[0020] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. By adopting the restorable ductile structural pier of the railway bridge described in the present invention, the pier can maintain sufficient rigidity to meet the rigidity requirements of normal train operation under the normal operation of the railway bridge and the action of small earthquakes. Under the action of small earthquakes, the pier maintains elasticity and is not damaged. Under the action of large earthquakes, the ultimate bearing capacity of the pier is reduced, which effectively reduces the seismic force borne by the pier, indirectly reduces the seismic force of the pile foundation, and protects the pile foundation. At the same time, the rigidity of the cross section above the pier bottom is relatively large, and only the cross section at the gap at the pier bottom is reduced due to the damage of the outer concrete, so that a plastic hinge is set at the pier bottom, resulting in ductile deformation of the pier, effectively dissipating the seismic energy, realizing the ductile seismic design of the pier, and improving the ductile deformation capacity and seismic energy dissipation capacity of traditional railway piers. After the earthquake, the cross section of the pier can be quickly repaired by re-pouring mortar, so that the pier can be restored to the size and rigidity before the earthquake, ensuring the driving safety of the railway bridge after the earthquake, and winning precious time for post-earthquake rescue work. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A half-section view of a restorable ductile structural pier of a railway bridge in the transverse direction of the bridge according to the present invention;

[0023] Figure 2 A half-section view of a restorable ductile structural pier of a railway bridge in the longitudinal direction of the bridge according to the present invention;

[0024] Figure 3 for Figure 1 Cross-section at AA in the middle;

[0025] Figure 4 for Figure 1 Schematic diagram of the reinforcement arrangement at the middle BB;

[0026] Figure 5 for Figure 1 Schematic diagram of reinforcement arrangement at CC in the middle.

[0027] Markings in the figure: 11-first longitudinal reinforcement, 12-first stirrup, 2-cap, 31-second longitudinal reinforcement, 32-second stirrup, 41-first tension reinforcement, 42-second tension reinforcement, 43-third tension reinforcement, 44-fourth tension reinforcement, 5-hollow cavity, 6-oblique reinforcement, 7-mortar cushion. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0029] Example 1

[0030] The invention provides a restorable ductile structural pier for a railway bridge, such as Figure 1-5 As shown, a restorable ductile structural pier of a railway bridge comprises a concrete pier body, the shape of the pier body is not limited, the cross-sectional shape of the pier body is only an example, and a circular cross-section may also be adopted, the pier body is provided with an outer ring steel cage and an inner ring steel cage, the outer ring steel cage comprises a first longitudinal reinforcement 11 and a first stirrup 12, the first longitudinal reinforcement 11 is arranged along the entire length of the pier body, the first stirrup 12 is evenly arranged along the first longitudinal reinforcement 11, a gap is provided between the bottom surface of the outer ring steel cage and the top surface of the pedestal 2, a mortar cushion layer 7 is provided in the gap; the inner ring steel cage is arranged at the bottom of the pier body, the inner ring steel cage comprises a second longitudinal reinforcement 31 and a second stirrup 32, the second stirrup 32 is evenly arranged along the second longitudinal reinforcement 31, and the bottom of the inner ring steel cage extends into the pedestal 2.

[0031] Specifically, the concrete pier body includes an outer ring steel cage and an inner ring steel cage. The design parameters such as the number of steel bars, steel bar diameter, steel bar strength, the inward shrinkage distance of the inner ring steel cage relative to the outer ring steel cage, cushion thickness, cushion strength, cushion area, etc. of the outer ring steel cage and the inner ring steel cage are designed according to the ductility and stiffness requirements of the pier under different earthquake intensities. There is a gap between the bottom surface of the outer ring steel cage and the top surface of the pedestal 2, and the lower part of the outer ring steel cage does not extend into the pedestal 2. Preferably, the bottom of the first longitudinal reinforcement 11 has a bending section, and the bending section is a 90-degree hook, which is beneficial to improve the stress performance at the bending section and improve the stability of the section above the bending section of the pier bottom under earthquake action. Of course, it can also be other angles in the current design specifications, such as 45 degrees. The length of the bending section refers to the requirements of the current design specifications, and there is the gap between the bottom surface of the bending section and the top surface of the pedestal 2. Preferably, the thickness of the gap is adapted to the sum of the thickness of the protective layer and the thickness of the mortar cushion layer 7. The thickness of the protective layer refers to the requirements of the current design specifications. The thickness of the mortar cushion layer 7 is 2cm-10cm to ensure that there is enough space to form a plastic hinge. The top surface of the mortar cushion layer 7 is connected to the bottom surface protective layer of the outer ring steel cage, the bottom surface of the mortar cushion layer 7 is connected to the top surface of the cap 2, the inner side of the mortar cushion layer 7 is connected to the outer side of the protective layer of the inner ring steel cage, and the outer side of the mortar cushion layer 7 is flush with the outer side surface of the pier body. Figure 5As shown, the pier body is formed with dense filling and uniform cross-sectional dimensions, which effectively meets the rigidity requirements of normal operation and is easy to construct. Preferably, the concrete of the pier body is constructed first, and then the mortar cushion layer 7 is constructed.

[0032] The pier body has a hollow cavity 5, and the upper and lower parts of the hollow cavity 5 are solid parts. The hollow cavity 5 has a chamfer, and oblique reinforcement 6 is provided in the concrete at the chamfer. That is, the pier body adopts a hollow structure, which effectively saves materials, reduces the deadweight of the pier, reduces costs, and improves rigidity. The oblique reinforcement 6 is provided in the solid part at the chamfer, which is beneficial to improving the stress performance of the pier body at the variable cross-section.

[0033] The upper solid part of the pier body is only provided with the outer ring steel cage, and the corresponding height of the hollow cavity 5 is also provided with the outer ring steel cage. The lower solid part of the pier body is provided with the outer ring steel cage and the inner ring steel cage, but the setting depth of the inner ring steel cage in the pier body is not limited to adapt to the height of the lower solid part, and the anchoring depth required by the current design specifications can be met. Preferably, the anchoring depth of the inner ring steel cage in the pier body is adapted to the height of the lower solid section of the hollow cavity 5, and the lower part of the inner ring steel cage extends into the pedestal 2 for anchoring. The anchoring depth refers to the anchoring depth requirements of the current design specifications. The pier body can be integrally formed and cast with the pedestal 2. The outer ring steel cage includes at least two layers of the first longitudinal reinforcement 11 to ensure the stress performance of the hollow thin-walled structure. The number of layers of the first longitudinal reinforcement 11 is determined according to the design requirements. This embodiment only exemplifies two layers. See. Figure 1-4 , a plurality of first stirrups 12 are evenly arranged on each row of the first longitudinal bars 11, and a first tie bar 41 is connected between two adjacent layers of the first longitudinal bars 11. The first tie bars 41 are evenly arranged along the length direction of the first longitudinal bars 11, and are tied to the oblique bars 6 on the inner side of the first tie bars 41 where the oblique bars 6 are arranged. The inner ring steel cage includes at least two layers of the second longitudinal bars 31, and the number of layers of the second longitudinal bars 31 is determined according to the design requirements. This embodiment also only illustrates two layers, see Figure 1 , 2 , 4 and 5, a plurality of second stirrups 32 are evenly arranged on each layer of the second longitudinal reinforcement 31, and a second tensioning bar 42 is connected between two adjacent second stirrups 32 of two layers. Further, a third tensioning bar 43 is connected between the innermost layer of the second stirrup 32 and the outermost layer of the first stirrup 12, see Figure 1-2 .

[0034] Preferably, the solid section below the hollow cavity 5 further comprises staggered fourth reinforcing bars 44, the fourth reinforcing bars 44 are evenly distributed along the longitudinal direction of the outer ring steel cage, and both ends of the fourth reinforcing bars 44 are connected to the first hoop 12 of the outermost layer, such as Figure 4 shown.

[0035] The invention discloses a restorable ductile structural pier for a railway bridge. The inner ring steel cage is set inwardly, so that the yield strength is reduced while the elastic stiffness of the pier bottom section remains unchanged. Compared with the traditional pier scheme, the equivalent yield bending moment and the ultimate bending moment can be reduced, and the ductile deformation capacity of the pier is significantly improved. Under the normal operation of the railway bridge and the action of small earthquakes, the pier maintains sufficient stiffness to meet the stiffness requirements of normal train operation. Under the action of small earthquakes, the pier maintains elasticity without being damaged. Under the action of large earthquakes, the mortar cushion layer at the bottom of the pier cracks at 7 places and quickly spreads to the inner ring steel cage. At this time, the cross-sectional size of the pier bottom is reduced, resulting in a decrease in stiffness. A plastic hinge is formed at the bottom of the pier, resulting in ductile deformation of the pier, effectively dissipating seismic energy, and realizing the ductile seismic design of the pier. This solves the problem that it is difficult to balance stiffness and ductility of traditional railway piers, improves the ductile deformation capacity and seismic energy dissipation capacity of traditional railway piers, protects the pile foundation, and avoids the collapse of the pier. At the same time, after the earthquake, the remaining part of the mortar cushion layer 7 is chiseled off and the mortar is re-poured to quickly repair the bottom section of the pier, so that the pier is restored to its size and stiffness before the earthquake, ensuring the driving safety of the railway bridge after the earthquake. The repair is easy and time-saving, which wins precious time for post-earthquake rescue work.

[0036] 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 protection scope of the present invention.

Claims

1. A restorable ductile structural pier for a railway bridge, characterized in that: The invention comprises a concrete pier body, wherein the pier body comprises an outer steel cage and an inner steel cage, wherein the outer steel cage comprises a first longitudinal steel bar (11) and a first stirrup (12), wherein the first longitudinal steel bar (11) is arranged along the entire length of the pier body, wherein a gap is provided between the bottom surface of the outer steel cage and the top surface of a cap (2), wherein a mortar cushion layer (7) is provided in the gap, wherein the inner steel cage comprises a second longitudinal steel bar (31) and a second stirrup (32), wherein the bottom of the inner steel cage extends into the cap (2), wherein the pier body comprises a hollow cavity (5), wherein the anchoring depth of the inner steel cage in the pier body is adapted to the height of the solid section below the hollow cavity (5), wherein the outer steel cage comprises at least two layers of the first longitudinal steel bar (11), wherein each layer of the first longitudinal steel bar (11) is evenly provided with a plurality of the first stirrups (12), and wherein the inner steel cage comprises at least two layers of the second longitudinal steel bar (31), wherein each layer of the second longitudinal steel bar (31) is evenly provided with a plurality of the second stirrups (32).

2. The ductile structural pier according to claim 1, characterized in that: The first longitudinal rib (11) has a bent section at the bottom, and there is a gap between the bottom surface of the bent section and the top surface of the support platform (2).

3. The ductile structural pier according to claim 2, characterized in that: The thickness of the gap is adapted to the sum of the thickness of the protective layer and the thickness of the mortar cushion layer (7), the thickness of the mortar cushion layer (7) is 2 cm-10 cm, and the mortar cushion layer (7) is arranged along the outer side of the protective layer of the inner ring steel cage.

4. The ductile structural pier according to claim 2, characterized in that: The bending section is a 90-degree hook.

5. The ductile structural pier according to any one of claims 1 to 4, characterized in that: The hollow cavity (5) has a chamfer, and an oblique rib (6) is provided at the chamfer.

6. The ductile structural pier according to claim 5, characterized in that: A first tensioning bar (41) is connected between the first longitudinal bars (11) of the innermost layer and the first longitudinal bars (11) of the outermost layer.

7. The ductile structural pier according to claim 6, characterized in that: A second tensioning bar (42) is connected between the second longitudinal bars (31) of the innermost layer and the second longitudinal bars (31) of the outermost layer.

8. The ductile structural pier according to claim 7, characterized in that: A third tensioning bar (43) is connected between the second innermost stirrup (32) and the first outermost stirrup (12).

9. The ductile structural pier according to claim 8, characterized in that: The solid section below the hollow cavity (5) further comprises staggered fourth tie bars (44), both ends of which are connected to the first hoop bars (12) of the outermost layer.

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