Variable cross-section pier top fixing structure and construction method

Abstract

The application relates to a variable cross-section pier top fixing structure, which comprises a pier, a plurality of first anchor bolts, a plurality of second anchor bolts and a box girder, the pier has an equal cross-section area and a variable cross-section area, and one side of the pier is provided with a first pull rod structure, the first pull rod structure is provided with at least one row of first anchor bolt holes and at least one row of second anchor bolt holes; the plurality of first anchor bolts are fixed to the equal cross-section area of the pier through the first anchor bolt holes, the plurality of second anchor bolts are fixed to the variable cross-section area of the pier through the second anchor bolt holes, and the inner diameter of the first anchor bolt holes is smaller than that of the second anchor bolt holes; the box girder is supported above the pier, the box girder is fixedly provided with a second pull rod structure, and the second pull rod structure is hinged to the first pull rod structure. By fixing the second anchor bolts to the variable cross-section area of the pier through the anchor bolt holes with a larger inner diameter, the second anchor bolts resist tensile force and do not bear shear force, and the technical problem that the anchor bolts located in the variable cross-section area of the pier cannot bear shear force in the prior art is solved, so that the lever arm of the anchor bolts is relatively long, and the anchor bolts are prone to damage.

Description

Technical Field

[0001] This application relates to the field of bridge engineering, specifically to a variable cross-section pier top fixing structure and construction method. Background Technology

[0002] With the booming development of the transportation industry, vehicle overloading has become a frequent occurrence, increasing the risk of bridge overturning. Due to their simple structure and convenient construction, tie rods are often used to reinforce bridges against overturning.

[0003] In related technologies, variable cross-section bridge piers are widely used in bridge engineering due to their good visual effect. The pier body of a variable cross-section bridge pier has a variable cross-section as a whole, while the cap beam at the top of the pier has a constant cross-section. The anchor bolts located in the pier body are in the variable cross-section area, which results in a long lever arm of the anchor bolts. They cannot withstand the bending stress generated by shear force, so mortar needs to be filled between the steel anchor plate at the top of the pier and the pier body. However, the mortar is easy to fall off, which makes the anchor bolts easy to be damaged.

[0004] Therefore, it is necessary to design a new variable cross-section pier top fixing structure to overcome the above problems. Summary of the Invention

[0005] This application provides a variable cross-section pier top fixing structure and construction method, which can solve the technical problem in related technologies that the anchor bolts located in the variable cross-section area of ​​the pier cannot withstand the bending stress generated by shear force, resulting in a long anchor bolt lever arm and easy damage.

[0006] In a first aspect, embodiments of this application provide a variable cross-section pier top fixing structure, comprising: a pier, a plurality of first anchor bolts, a plurality of second anchor bolts, and a box girder. The pier has a constant cross-section region and a variable cross-section region, and a first tie rod structure is provided on one side of the pier. The first tie rod structure has at least one row of first anchor bolt holes and at least one row of second anchor bolt holes. A plurality of first anchor bolts pass through the first anchor bolt holes and are fixed to the constant cross-section region of the pier, and a plurality of second anchor bolts pass through the second anchor bolt holes and are fixed to the variable cross-section region of the pier. The diameter of the first anchor bolt is equal to the diameter of the second anchor bolt, and the inner diameter of the first anchor bolt hole is smaller than the inner diameter of the second anchor bolt hole. The box girder is supported above the pier, and the box girder is fixedly provided with the second tie rod structure, which is hinged to the first tie rod structure.

[0007] In conjunction with the first aspect, in one embodiment, the first tie rod structure includes an anchor plate and a transverse ear plate. The anchor plate is provided with at least one row of first anchor bolt holes and at least one row of second anchor bolt holes. The anchor plate is fixed to one side of the pier by a plurality of first anchor bolts and a plurality of second anchor bolts. The anchor plate is perpendicularly connected to the transverse ear plate, and the transverse ear plate is hinged to the second tie rod structure.

[0008] In conjunction with the first aspect, in one embodiment, the second tie rod structure includes a support plate and a vertical ear plate. The support plate is fixed to the box girder, and the support plate and the vertical ear plate are vertically connected. One end of the vertical ear plate is fixed to the support plate, and the other end of the vertical ear plate is hinged to the transverse ear plate via a pin.

[0009] In conjunction with the first aspect, in one embodiment, a plurality of first anchor bolts are symmetrically arranged along the axis of the vertical ear plate, and a plurality of second anchor bolts are symmetrically arranged along the axis of the vertical ear plate.

[0010] In conjunction with the first aspect, in one embodiment, mortar is filled between the anchor plate and the pier.

[0011] In conjunction with the first aspect, in one embodiment, the anchor plate includes a horizontal plate and a vertical plate, the horizontal plate and the vertical plate being connected to form a T-shape, the horizontal plate being provided with at least one row of first anchor bolt holes, and the vertical plate being provided with at least one row of second anchor bolt holes.

[0012] In conjunction with the first aspect, in one embodiment, the difference between the inner diameter of the first anchor bolt hole and the inner diameter of the second anchor bolt hole ranges from 3 to 5 mm.

[0013] In conjunction with the first aspect, in one implementation, the number of the first anchor bolts is determined according to the following formula:

[0014]

[0015] Where N is the total number of first anchor bolts, F is the overturning force on the second tie rod structure, and V is the shear design bearing capacity of the first anchor bolts.

[0016] In conjunction with the first aspect, in one embodiment, the length of the first anchor bolt is less than the length of the second anchor bolt.

[0017] Secondly, embodiments of this application provide a construction method for a variable cross-section pier top fixed structure, which includes the following steps:

[0018] Step 1: Pass multiple first anchor bolts through the first anchor bolt holes and fix them to the constant cross-section area of ​​the pier. Pass multiple second anchor bolts through the second anchor bolt holes and fix them to the variable cross-section area of ​​the pier. Fill the space between the first tie rod structure and the pier with mortar.

[0019] Step 2: Install the second tie rod structure at the bottom of the box girder, and hinge the second tie rod structure to the first tie rod structure using a pin.

[0020] The beneficial effects of the technical solutions provided in this application include:

[0021] By fixing multiple first anchor bolts through first anchor bolt holes to the constant cross-section area of ​​the pier, and fixing multiple second anchor bolts through second anchor bolt holes to the variable cross-section area of ​​the pier, wherein the inner diameter of the first anchor bolt hole is smaller than the inner diameter of the second anchor bolt hole, the multiple first anchor bolts resist the shear force generated by bridge overturning, and the multiple second anchor bolts resist the tensile force generated by the overturning moment, without bearing shear force. This solves the technical problem in related technologies where anchor bolts located in the variable cross-section area of ​​the pier cannot withstand the bending stress generated by shear force, resulting in long anchor bolt lever arms and easy damage. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of a variable cross-section pier top fixing structure provided in an embodiment of this application;

[0024] Figure 2 for Figure 1 Sectional view of AA;

[0025] Figure 3 This is a schematic diagram of the structure of the anchor plate provided in the embodiments of this application;

[0026] Figure 4 This is a schematic diagram illustrating the principle of calculating the tensile force on the first and second anchor bolts, provided for embodiments of this application.

[0027] In the diagram: 1. Pier; 2. First tie rod structure; 21. Anchor plate; 211. First anchor bolt hole; 212. Second anchor bolt hole; 22. Transverse ear plate; 23. First stiffening plate; 3. First anchor bolt; 4. Second anchor bolt; 5. Box girder; 6. Second tie rod structure; 61. Support plate; 62. Vertical ear plate; 63. Second stiffening plate; 7. Pin; 8. Mortar. Detailed Implementation

[0028] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0029] This application provides a variable cross-section pier top fixing structure and construction method, which can solve the technical problem that the anchor bolts located in the variable cross-section area of ​​the pier cannot withstand the bending stress generated by shear force, resulting in long anchor bolt lever arms and easy damage.

[0030] See Figure 1-3 As shown in the figure, this application provides a variable cross-section pier top fixing structure, which includes: a pier 1, a plurality of first anchor bolts 3, a plurality of second anchor bolts 4, and a box girder 5. The pier 1 has a constant cross-section area and a variable cross-section area, and a first tie rod structure 2 is provided on one side of the pier 1. The first tie rod structure 2 is provided with at least one row of first anchor bolt holes 211 and at least one row of second anchor bolt holes 212. The plurality of first anchor bolts 3 pass through the first anchor bolt holes 211 and are fixed to the constant cross-section area of ​​the pier 1, and the plurality of second anchor bolts 4 pass through the second anchor bolt holes 212 and are fixed to the variable cross-section area of ​​the pier 1. The diameter of the first anchor bolt 3 is equal to the diameter of the second anchor bolt 4, and the inner diameter of the first anchor bolt hole 211 is smaller than the inner diameter of the second anchor bolt hole 212. The box girder 5 is supported above the pier 1, and the box girder 5 is fixedly provided with a second tie rod structure 6, which is hinged to the first tie rod structure 2.

[0031] In this embodiment, the cross-sectional area of ​​the pier 1 located in the constant cross-section region is equal, and the cross-sectional area of ​​the pier 1 located in the variable cross-section region gradually decreases. At least one row of the first anchor bolt holes 211 can be configured as one row of first anchor bolt holes 211 or more rows of first anchor bolt holes 211. Preferably, at least one row of the first anchor bolt holes 211 is configured as two rows of first anchor bolt holes 211. At least one row of the second anchor bolt holes 212 can be configured as one row of second anchor bolt holes 212 or more rows of second anchor bolt holes 212. Preferably, at least one row of the second anchor bolt holes 212 is configured as two rows of second anchor bolt holes 212. Multiple first anchor bolts 3 can be configured as four first anchor bolts 3 or more first anchor bolts 3. Preferably, multiple first anchor bolts 3 are configured as eight first anchor bolts 3. Multiple second anchor bolts 4 can be configured as two second anchor bolts 4 or more second anchor bolts 4. Preferably, multiple second anchor bolts 4 are configured as four second anchor bolts. 4. The number of the first anchor bolts 3 corresponds to the number of the first anchor bolt holes 211, and the number of the second anchor bolts 4 corresponds to the number of the second anchor bolt holes 212. The inner diameter of the first anchor bolt hole 211 is slightly larger than the diameter of the first anchor bolt 3. Exemplarily, the inner diameter of the first anchor bolt hole 211 is 0.5 mm larger than the diameter of the first anchor bolt 3, so that the first anchor bolt 3 contacts the inner wall of the first anchor bolt hole 211. The inner diameter of the second anchor bolt hole 212 is larger than the diameter of the second anchor bolt 4, so that the second anchor bolt 4 does not need to contact the inner wall of the second anchor bolt hole 212. The second tie rod structure 6 is subjected to the overturning force of the box girder 5, so that the first tie rod structure 2 is subjected to an upward shear force and a rightward tensile force. The multiple first anchor bolts 3 resist the shear force generated by the overturning of the bridge, and the multiple second anchor bolts 4 resist the tensile force generated by the overturning moment, without bearing shear force. It is not necessary to set longer anchor bolts in the variable cross-section area. Even if the mortar 8 falls off, it will not affect the stress on the anchor bolts.

[0032] This embodiment fixes multiple first anchor bolts 3 through the first anchor bolt holes 211 to the constant cross-section area of ​​the pier 1, and multiple second anchor bolts 4 through the second anchor bolt holes 212 to the variable cross-section area of ​​the pier 1. The inner diameter of the first anchor bolt hole 211 is smaller than the inner diameter of the second anchor bolt hole 212. This allows the multiple first anchor bolts 3 to resist the shear force generated by bridge overturning, and the multiple second anchor bolts 4 to resist the tensile force generated by the overturning moment, without bearing shear force. It eliminates the need for longer anchor bolts in the variable cross-section area. Even if the mortar 8 falls off, it will not affect the stress on the anchor bolts. This solves the technical problem in related technologies where anchor bolts located in the variable cross-section area of ​​the pier 1 cannot withstand the bending stress generated by shear force, resulting in long anchor bolt lever arms and easy damage.

[0033] Further, see Figure 1-3As shown, in some embodiments, the first tie rod structure 2 includes an anchor plate 21 and a transverse ear plate 22. The anchor plate 21 is provided with at least one row of first anchor bolt holes 211 and at least one row of second anchor bolt holes 212. The anchor plate 21 is fixed to one side of the pier 1 by a plurality of first anchor bolts 3 and a plurality of second anchor bolts 4. The anchor plate 21 is perpendicularly connected to the transverse ear plate 22, and the transverse ear plate 22 is hinged to the second tie rod structure 6.

[0034] In this embodiment, the transverse ear plate 22 is welded to one side of the anchor plate 21. The number of transverse ear plates 22 can be set to one, two, or more. Exemplarily, the second tie rod structure 6 is clamped between two transverse ear plates 22 and hinged to the two transverse ear plates 22, so that the overturning force of the box girder 5 on the second tie rod structure 6 is converted into the upward shear force and the rightward tension force on the transverse ear plates 22, and transmitted to the multiple first anchor bolts 3 and multiple second anchor bolts 4 through the anchor plate 21. A first stiffening plate 23 is provided on one side of each transverse ear plate 22, and the first stiffening plate 23 is fixed to the anchor plate 21.

[0035] Further, see Figure 1 and Figure 2 As shown, in some embodiments, the second tie rod structure 6 includes a support plate 61 and a vertical ear plate 62. The support plate 61 is fixed to the box girder 5. The support plate 61 and the vertical ear plate 62 are vertically connected. One end of the vertical ear plate 62 is fixed to the support plate 61, and the other end of the vertical ear plate 62 is hinged to the transverse ear plate 22 through a pin 7.

[0036] In this embodiment, the support plate 61 is fixed at the bottom of the box girder 5. The support plate 61 can be a steel plate. The support plate 61 is vertically connected to the vertical ear plate 62. The vertical ear plate 62 is provided with second stiffening plates 63 on both sides. The second stiffening plates 63 are fixed to the support plate 61. The vertical ear plate 62 is hinged to the transverse ear plate 22 through the pin 7, so that the overturning force of the box girder 5 on the vertical ear plate 62 can be converted into the upward shear force and the rightward tension force on the transverse ear plate 22.

[0037] Further, see Figure 2 As shown, in some embodiments, a plurality of first anchor bolts 3 are symmetrically arranged along the axis of the vertical ear plate 62, and a plurality of second anchor bolts 4 are symmetrically arranged along the axis of the vertical ear plate 62.

[0038] In this embodiment, the plurality of first anchor bolts 3 can be configured as four or more first anchor bolts 3, and the plurality of second anchor bolts 4 can be configured as two or more second anchor bolts 4. Preferably, the plurality of first anchor bolts 3 are configured as eight first anchor bolts 3, and the plurality of second anchor bolts 4 are configured as four second anchor bolts 4. The eight first anchor bolts 3 are arranged in two rows, and the four second anchor bolts 4 are arranged in two rows. The eight first anchor bolts 3 are symmetrically arranged along the axis of the vertical ear plate 62, and the four second anchor bolts 4 are symmetrically arranged along the axis of the vertical ear plate 62, so that the force on each first anchor bolt 3 and each second anchor bolt 4 is uniform, thereby improving the stability of the variable cross-section pier top fixing structure.

[0039] Further, see Figure 1 and Figure 2 As shown, in some embodiments, mortar 8 is filled between the anchor plate 21 and the pier 1.

[0040] In this embodiment, the mortar 8 can be set as epoxy mortar to protect the second anchor bolt 4. Even if the mortar 8 falls off, it will not affect the stress on the second anchor bolt 4.

[0041] Further, see Figure 3 As shown, in some embodiments, the anchor plate 21 includes a horizontal plate and a vertical plate, the horizontal plate and the vertical plate are connected to form a T-shape, the horizontal plate is provided with at least one row of first anchor bolt holes 211, and the vertical plate is provided with at least one row of second anchor bolt holes 212.

[0042] In this embodiment, the horizontal plate is provided with one row of first anchor bolt holes 211 or more rows of first anchor bolt holes 211, and the vertical plate is provided with one row of second anchor bolt holes 212 or more rows of second anchor bolt holes 212. Preferably, the horizontal plate is provided with two rows of first anchor bolt holes 211, and the vertical plate is provided with two rows of second anchor bolt holes 212. The two rows of first anchor bolt holes 211 and the two rows of second anchor bolt holes 212 are symmetrically arranged along the axis of the vertical ear plate 62 to cooperate with the use of multiple first anchor bolts 3 and multiple second anchor bolts 4. The anchor plate 21 is set into a T-shape according to the arrangement of the first anchor bolt holes 211 and the second anchor bolt holes 212, so that the anchor plate 21 is fixed to one side of the pier 1 in the best stress state.

[0043] Further, see Figure 1-3 As shown, in some embodiments, the difference between the inner diameter of the first anchor bolt hole 211 and the inner diameter of the second anchor bolt hole 212 ranges from 3 to 5 mm.

[0044] In this embodiment, the difference between the inner diameter of the first anchor bolt hole 211 and the inner diameter of the second anchor bolt hole 212 can be set to a range of 3 to 5 mm, so that the second anchor bolt 4 resists the tensile force generated by the overturning moment and does not bear the shear force, and does not contact the inner wall of the second anchor bolt hole 212, while cooperating with the nut to fix the anchor plate 21.

[0045] Further, see Figure 1 and Figure 2 As shown, in some embodiments, the number of the first anchor bolts 3 is determined according to the following formula:

[0046]

[0047] Where N is the total number of first anchor bolts, F is the overturning force on the second tie rod structure, and V is the shear design bearing capacity of the first anchor bolts.

[0048] In this embodiment, the total number N of the first anchor bolts can be set within a certain range according to the specifications. When the shear design bearing capacity V of the first anchor bolt meets the requirements, the total number N of the first anchor bolts can be determined.

[0049] Further, see Figure 1 As shown, in some embodiments, the length of the first anchor bolt 3 is less than the length of the second anchor bolt 4.

[0050] In this embodiment, the first anchor bolt 3 and the second anchor bolt 4 have the same anchoring depth, and the length of the second anchor bolt 4 increases with the width of the pier 1 located in the variable cross-section area.

[0051] Further, see Figure 1 As shown, in some embodiments, this application provides a construction method for a variable cross-section pier top fixed structure, which includes the following steps:

[0052] Step 1: Pass multiple first anchor bolts 3 through the first anchor bolt hole 211 and fix them to the equal cross-section area of ​​the pier 1. Pass multiple second anchor bolts 4 through the second anchor bolt hole 212 and fix them to the variable cross-section area of ​​the pier 1. Fill the space between the first tie rod structure 2 and the pier 1 with mortar 8.

[0053] Step 2: Install the second tie rod structure 6 at the bottom of the box girder 5, and hinge the second tie rod structure 6 and the first tie rod structure 2 together with the pin 7.

[0054] In this embodiment, the number of the first anchor bolt 3 and the second anchor bolt 4 is determined. Multiple first anchor bolts 3 are passed through the first anchor bolt holes 211 and fixed to the equal cross-section area of ​​the pier 1. Multiple second anchor bolts 4 are passed through the second anchor bolt holes 212 and fixed to the variable cross-section area of ​​the pier 1. Mortar 8 is filled between the anchor plate 21 and the pier 1. The support plate 61 is anchored at the bottom of the box girder 5. The vertical ear plate 62 is welded to the support plate 61. The transverse ear plate is welded to one side of the anchor plate 21. 22. The vertical ear plate 62 and the horizontal ear plate 22 are hinged by the pin 7. The vertical ear plate 62 is subjected to the overturning force of the box girder 5, which causes the anchor plate 21 to be subjected to upward shear force and rightward tension. The multiple first anchor bolts 3 resist the shear force generated by the overturning of the bridge, and the multiple second anchor bolts 4 resist the tension generated by the overturning moment, without bearing shear force. This achieves non-contact with the inner wall of the second anchor bolt hole 212, eliminating the need to set longer anchor bolts in the variable cross-section area. Even if the mortar 8 falls off, it will not affect the stress on the anchor bolts.

[0055] The tensile forces acting on the first anchor bolt 3 and the second anchor bolt 4 satisfy the following formula:

[0056]

[0057] M = F·L(3),

[0058] Among them, T i Let y be the tensile force on the i-th anchor bolt. i Let F be the height difference between the i-th anchor bolt and the top anchor bolt, F be the overturning force on the second tie rod structure, L be the distance between the pin shaft and the anchor plate, and M be the torque of the overturning force. Figure 4 As shown, exemplarily, the overturning force F on the second tie rod structure is set to 200kN, the distance L from the pin shaft to the anchor plate is set to 0.3m, the eight first anchor bolts 3 can be arranged in two rows, and the four second anchor bolts 4 can be arranged in two rows. The first row of first anchor bolts 3 are top anchor bolts, and the second row of second anchor bolts 4 are bottom anchor bolts. The height difference between the first anchor bolts 3 and the top anchor bolt in the first row is set to 0m, and the height difference between the first anchor bolts 3 and the top anchor bolt in the second row is set to 0.2m. The height difference between the second anchor bolts 4 and the top anchor bolt in the first row is set to... The second anchor bolt 4 in the second row is 0.4m above the top anchor bolt. The tensile force on each of the first anchor bolts 3 in the first row is 0. The tensile force on each of the first anchor bolts 3 in the second row is 6.7kN. The tensile force on each of the second anchor bolts 4 in the first row is 13.3kN. The tensile force on each of the second anchor bolts 4 in the second row is 20kN. The second anchor bolt 4 is mainly used to resist the tensile force generated by the overturning moment.

[0059] The shear forces acting on the first anchor bolt 3 and the second anchor bolt 4 satisfy the following formula:

[0060]

[0061] Wherein, V is the shear design bearing capacity of the first anchor bolt, F is the overturning force on the second tie rod structure, and N is the total number of the first anchor bolts. For example, the number of the first anchor bolts is set to 8, the overturning force F on the second tie rod structure is set to 200kN, the shear force V on each of the first anchor bolts 3 is 25kN, and the shear force V on each of the second anchor bolts 4 is 0. The first anchor bolts 3 are mainly used to resist the shear force generated by the overturning of the bridge, and the second anchor bolts 4 do not bear the shear force.

[0062] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0063] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0064] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A variable cross-section pier top fixing structure, characterized in that, It includes: The bridge pier (1) has a constant cross-section area and a variable cross-section area, and a first tie rod structure (2) is provided on one side of the bridge pier (1). The first tie rod structure (2) includes an anchor plate (21) and a transverse ear plate (22). The anchor plate (21) includes a horizontal plate and a vertical plate. The horizontal plate and the vertical plate are connected to form a T-shape. The horizontal plate is provided with at least one row of first anchor bolt holes (211), and the vertical plate is provided with at least one row of second anchor bolt holes (212). Multiple first anchor bolts (3) and multiple second anchor bolts (4), the multiple first anchor bolts (3) passing through the first anchor bolt hole (211) and fixed to the equal cross-section area of ​​the pier (1), the multiple second anchor bolts (4) passing through the second anchor bolt hole (212) and fixed to the variable cross-section area of ​​the pier (1), wherein the length of the first anchor bolt (3) is less than the length of the second anchor bolt (4), the diameter of the first anchor bolt (3) is equal to the diameter of the second anchor bolt (4), and the inner diameter of the first anchor bolt hole (211) is less than the inner diameter of the second anchor bolt hole (212); The box girder (5) is supported above the pier (1). The box girder (5) is fixed with a second tie rod structure (6), and the second tie rod structure (6) and the first tie rod structure (2) are hinged together.

2. The variable cross-section pier top fixing structure as described in claim 1, characterized in that, The anchor plate (21) is provided with at least one row of first anchor bolt holes (211) and at least one row of second anchor bolt holes (212), and the anchor plate (21) is fixed to one side of the pier (1) by a plurality of first anchor bolts (3) and a plurality of second anchor bolts (4). The anchor plate (21) is perpendicularly connected to the transverse ear plate (22), and the transverse ear plate (22) is hinged to the second tie rod structure (6).

3. The variable cross-section pier top fixing structure as described in claim 2, characterized in that, The second tie rod structure (6) includes a support plate (61) and a vertical ear plate (62). The support plate (61) is fixed to the box girder (5). The support plate (61) and the vertical ear plate (62) are vertically connected. One end of the vertical ear plate (62) is fixed to the support plate (61), and the other end of the vertical ear plate (62) is hinged to the horizontal ear plate (22) through a pin (7).

4. The variable cross-section pier top fixing structure as described in claim 3, characterized in that, Multiple first anchor bolts (3) are symmetrically arranged along the axis of the vertical ear plate (62), and multiple second anchor bolts (4) are symmetrically arranged along the axis of the vertical ear plate (62).

5. The variable cross-section pier top fixing structure as described in claim 2, characterized in that, The anchor plate (21) and the pier (1) are filled with mortar (8).

6. The variable cross-section pier top fixing structure as described in claim 1, characterized in that, The difference between the inner diameter of the first anchor bolt hole (211) and the inner diameter of the second anchor bolt hole (212) ranges from 3 to 5 mm.

7. The variable cross-section pier top fixing structure as described in claim 1, characterized in that, The number of the first anchor bolts (3) is determined according to the following formula: ， Where N is the total number of first anchor bolts, F is the overturning force on the second tie rod structure, and V is the shear design bearing capacity of the first anchor bolts.

8. A construction method for a variable cross-section pier top fixed structure as described in claim 1, characterized in that, It includes the following steps: Multiple first anchor bolts (3) are passed through first anchor bolt holes (211) and fixed to the equal cross-section area of ​​the pier (1), multiple second anchor bolts (4) are passed through second anchor bolt holes (212) and fixed to the variable cross-section area of ​​the pier (1), and mortar (8) is filled between the first tie rod structure (2) and the pier (1). A second tie rod structure (6) is installed at the bottom of the box girder (5), and the second tie rod structure (6) and the first tie rod structure (2) are hinged together by a pin (7).

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