A longitudinal seismic block for flexible pier bridges and its design method

Abstract

The present invention relates to the technical field of bridge seismic resistance, and particularly to a longitudinal seismic block for a flexible pier bridge and a design method thereof; the longitudinal seismic block is installed between the transition pier capping beam and the main beam of the flexible pier bridge, and the longitudinal seismic block includes: a steel box block, an anchor plate, anchor bars and a rubber cushion block; the transition pier capping beam is connected to the steel box block through the anchor plate or the anchor plate and the anchor bars; a rubber cushion block is pasted on the upper part of the steel box block. This longitudinal seismic blocking part enables the transition piers of this type of bridge to participate in resisting seismic actions and dissipating seismic energy under strong earthquake actions, ensuring that the bridge does not have the problem of beam falling.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge seismic resistance, and particularly relates to a longitudinal seismic block for flexible pier bridges and a design method therefor. Background Art

[0002] Flexible piers are widely used in ordinary bridges due to their simple design and construction and strong adaptability. With the rapid development of highway construction, more and more such bridges will be built in high-intensity seismic areas. Since the seismic displacement response of bridges in these areas is relatively large, the code requires anti-falling beam design, and one of the important measures is to set longitudinal seismic blocks. In China, longitudinal seismic blocks belong to seismic design measures, and the design requirements are relatively brief. Foreign design codes generally calculate the design seismic impact force of seismic blocks by using the reaction force of the simple support end bearings of bridges. When the width and length of the beam span are large, the calculated seismic impact force may be too small, and when the piers are relatively flexible, it may be too large, so it is not very accurate. The force-bearing process of longitudinal seismic blocks under seismic action is essentially an impact collision process between the upper beam span and the piers. Therefore, many scholars directly use the collision analysis method to study seismic blocks, and propose relatively applicable finite elements for simulation analysis to directly calculate the collision effect of seismic blocks. However, due to the very complex impact collision effect of the blocks and many influencing factors, it is still difficult to accurately calculate and analyze, and the calculation is also very cumbersome, making it difficult to directly apply to the design of longitudinal seismic blocks for bridges. High-intensity seismic areas are widely distributed in China. Bridges are often important disaster relief control channels during earthquakes. If they fall or are damaged due to earthquakes, it will not only cause heavy losses, but also have a huge adverse impact on earthquake relief. Therefore, studying the design method of longitudinal seismic blocks for flexible pier bridges and making it easy to apply to the design of ordinary bridges, and at the same time studying simple and practical longitudinal seismic blocks for large-scale application in bridge construction, all have very important practical significance. Summary of the Invention

[0003] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a longitudinal seismic block for flexible pier bridges and a design method therefor. The longitudinal seismic block enables this type of bridge to transition the pier to participate in resisting seismic action and dissipating seismic energy under strong seismic action, ensuring that the bridge does not have the problem of falling beams.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A longitudinal seismic block for flexible pier bridges, the longitudinal seismic block 12 is installed between the transition pier capping beam 1 and the main beam 7 of the flexible pier bridge, and is characterized in that: the longitudinal seismic block 12 includes: a steel box block 2, an anchor plate 3, anchor bars 4 and a rubber cushion block 5;

[0006] The transition pier capping beam 1 is connected to the steel box block 2 through the anchor plate 3 or the anchor plate 3 and the anchor bars 4.

[0007] A rubber cushion block 5 is pasted on the upper part of the steel box block 2.

[0008] The longitudinal seismic block 12 is longitudinally arranged on the mid-span side of the end cross beam 6 on the main beam 7, and the clear distance from the end cross beam 6 is ≥200 mm; the longitudinal seismic block 12 is transversely arranged in the beam-to-beam gap and is close to the web of the main beam 7.

[0009] The longitudinal seismic blocks 12 are arranged on both the front and rear longitudinal sides of the transition pier capping beam 1. There are several longitudinal seismic blocks 12 on one side, and the several longitudinal seismic blocks 12 are symmetrically arranged with respect to the transverse center line of the transition pier capping beam 1.

[0010] The steel box block 2 is a box-shaped steel structure. The web 10 and the top and bottom plates 9 are connected by butt welds. The upper cover plate 11 of the steel box block 2 is connected by fillet welds. The lower part of the steel box block 2 has no bottom plate, and the bottom of the steel box block 2 is connected to the anchor plate 3 by a combined weld of butt and fillet joints.

[0011] The steel box block 2 is installed on both sides of the end cross beam 6 provided on the main beam 7, and the distance from the end cross beam 6 is ≥20 mm.

[0012] When the transition pier capping beam 1 is a concrete capping beam, the anchor plate 3 is connected to the concrete capping beam through the anchor bars 4; when the transition pier capping beam 1 is a steel capping beam, the anchor plate 3 is welded to the steel capping beam.

[0013] The thickness of the anchor plate 3 is ≥25 mm.

[0014] The thickness of the rubber cushion block 5 is ≥40 mm.

[0015] A design method for the longitudinal seismic block in a flexible pier bridge longitudinal seismic block, including

[0016] S1. Calculate the seismic force acting on the longitudinal seismic block 12;

[0017] S2. Calculate the design bending moment and design shear force of the steel box block on the longitudinal seismic block 12 through the seismic force;

[0018] S3. Calculate the design bending moment and design shear force of the anchor plate 3 anchorage through the seismic force.

[0019] The calculation method of the seismic force is as follows:

[0020]

[0021] The calculation method of the design bending moment and design shear force of the steel box block 2 is as follows:

[0022] M s= 1.1F·h (2)

[0023] V s = 1.2×1.1F (3)

[0024] The calculation methods for the design bending moment and design shear force anchored by the anchor plate 3 are as follows:

[0025] M s = 1.2×1.1F·h (4)

[0026] V s = 1.2×1.1F (5)

[0027] In formulas (1) to (5), M ye is the equivalent yield bending moment of the pier column 14 at the plastic hinge 13 at the bottom along the longitudinal direction of the bridge; H is the distance from the center of the pier plastic hinge 13 to the top of the transition pier capping beam 1; h is the distance from the seismic force action point of the steel box block 2 to the top of the transition pier capping beam 1; F is the seismic force acting on the steel box block 2; M s is the design bending moment; V s is the design shear force.

[0028] In the calculations of the seismic force, the design bending moment and design shear force of the steel box block 2, and the design bending moment and design shear force of the anchor plate 3 anchoring, the standard values are taken for the strength of all materials.

[0029] The beneficial effects of the present invention are as follows:

[0030] 1. The present invention enables the transition piers to participate in resisting the strong longitudinal seismic action of the bridge, giving full play to the overall seismic performance of the bridge. By setting the gap between the main girder end crossbeam and the longitudinal seismic block, when the bridge is under minor earthquake action, due to the small longitudinal displacement of the bridge, the longitudinal seismic block is not stressed; when the bridge is under strong earthquake action, the longitudinal displacement of the bridge is large, the main girder impacts the longitudinal seismic block, and the longitudinal seismic block drives the transition piers to participate in resisting the earthquake action and consuming earthquake energy. Therefore, the present invention adopts the seismic design principle of staged fortification, improving the seismic performance of the overall bridge.

[0031] 2. The steel box block in the longitudinal seismic block of the present invention has stable performance, can resist the impact of the main girder under earthquake action and consume a large amount of earthquake energy, ensuring that the bridge does not experience unseating. The steel box block is made of steel structure, with stable material properties, and is of box-shaped structure, having good stability. A relatively thick rubber cushion block is provided at the part where the upper part of the steel box block acts on the main girder end crossbeam, playing a role in buffering the seismic force. Therefore, the steel box block can resist the impact action of the earthquake. The steel structure of the steel box block has excellent yield performance, and its performance is stable after yielding, and it can consume a large amount of earthquake energy. When the earthquake acting force is very large, the bottom of the steel box block yields, but the upper part remains intact, increasing the relative displacement of the main girder, and the seismic force acting on the steel box block will relatively decrease, so unseating can be prevented.

[0032] 3. The longitudinal seismic block design method of the present invention is simple and practical. For flexible pier bridges in high-intensity seismic areas, it is necessary to calculate the equivalent yield moment of the piers during design. According to the method of the present invention, the longitudinal seismic force borne by the longitudinal seismic block can be easily calculated using the equivalent yield moment, and the corresponding longitudinal seismic block can be designed. Therefore, the design of this longitudinal seismic block hardly increases the workload of bridge design and is very simple and practical.

[0033] 4. The longitudinal seismic block of the present invention has a simple structure, is easy to process, and has a wide range of applications. The main structure of the longitudinal seismic block is a simple box-shaped steel block and an anchor plate, and the processing, transportation, and installation are all very simple. It can be applied to concrete or steel girder main beams, and can also be applied to concrete piers or steel piers, so the scope of application is very wide.

[0034] 5. The longitudinal seismic block of the present invention is easy to recover. If the steel box block has a large yield deformation under strong earthquake action, after the earthquake, the deformed and unusable steel box block can be cut off, and a newly processed steel box block can be welded and installed on the anchor plate to restore the seismic and anti-falling beam functions of the longitudinal seismic block. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic diagram of the overall installation structure of the present invention;

[0036] Figure 2 is a schematic diagram of the layout of the longitudinal seismic block in Embodiment 1;

[0037] Figure 3 is a schematic diagram of the structure of the longitudinal seismic block in Embodiment 1;

[0038] Figure 4 is a schematic diagram of the layout of the longitudinal seismic block in Embodiment 2;

[0039] Figure 5 is a schematic diagram of the structure of the longitudinal seismic block in Embodiment 2;

[0040] As shown in the figure: 1 Transition pier capping beam; 2 Steel box block; 3 Anchor plate; 4 Anchor bar; 5 Rubber cushion block; 6 End cross beam; 7 Main beam; 8 Expansion joint; 9 Top and bottom plates; 10 Web; 11 Upper cover plate; 12 Longitudinal seismic block; 13 Pier plastic hinge; 14 Pier column; 15 Pier foundation; 16 Bearing. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] The technical solutions of the present invention will be further described below in conjunction with the drawings and specific embodiments:

[0042] Embodiment 1

[0043] As Figure 1 , 2As shown in FIGS. 2 and 3, the present invention provides a longitudinal seismic block for a flexible pier bridge and a design method. The longitudinal seismic block 12 is applied to a flexible pier bridge and is arranged on the transition pier capping beam 1 of the flexible pier bridge. The piers of the flexible pier bridge are composed of a foundation, flexible pier columns and a capping beam. The main girder 7 is composed of multiple T-shaped girders or small box girders. There is a net spacing between the T-shaped girders or small box girders, and end cross beams 6 are provided at the ends. The transition pier is the pier on which the expansion joint 8 is provided for the main girder 7 thereon.

[0044] The longitudinal seismic block 12 of the present invention includes: a steel box block 2, an anchor plate 3, anchor bars 4 and a rubber cushion block 5, and the specific implementation is as described below:

[0045] The steel box block 2 is a box-shaped steel structure. The web 10 and the top and bottom plates 9 are all connected by butt welds. The upper cover plate 11 of the steel box block 2 is connected by fillet welds. The lower part of the steel box block 2 has no bottom plate. The bottom of the steel box block 2 is connected to the anchor plate 3 by a combined weld of butt and fillet joints. A rubber cushion block 5 with a thickness ≥ 40 mm is pasted on the upper part of the steel box block 2.

[0046] In this embodiment, the transition pier capping beam 1 is a concrete capping beam. The anchor plate 3 is connected to the concrete capping beam through the anchor bars 4. The thickness of the anchor plate 3 ≥ 25 mm.

[0047] The longitudinal seismic block 12 is installed on the transition pier capping beam 1, longitudinally arranged on the mid-span side of the end cross beam 6, and the net distance from the end cross beam 6 ≥ 200 mm; transversely arranged in the beam gap and close to the web of the main girder 7; the longitudinal seismic block 12 is provided on both the front and rear sides of the transition pier capping beam 1 in the longitudinal direction of the bridge. There are several longitudinal seismic blocks 12 on one side, and several longitudinal seismic blocks 12 are symmetrically arranged relative to the transverse center line of the transition pier capping beam 1; the number of longitudinal seismic blocks 12 provided on one transition pier capping beam 1 should be determined according to calculations.

[0048] After a strong earthquake, if the steel box block 2 is deformed too much and cannot be used, the steel box block 2 can be cut off from the anchor plate 3, and then a new steel box block 2 is welded in place.

[0049] Embodiment 2

[0050] As Figure 1 、 3 As shown in FIGS. 2 and 4, the present invention provides a longitudinal seismic block for a flexible pier bridge and a design method. The longitudinal seismic block 12 is applied to a flexible pier bridge and is arranged on the transition pier capping beam 1 of the flexible pier bridge. The piers of the flexible pier bridge are composed of a foundation, flexible pier columns and a capping beam. The main girder 7 is composed of multiple T-shaped girders or small box girders. There is a net spacing between the T-shaped girders or small box girders, and end cross beams 6 are provided at the ends. The transition pier is the pier on which the expansion joint 8 is provided for the main girder 7 thereon.

[0051] The longitudinal seismic block 12 of the present invention comprises: a steel box block 2, an anchor plate 3, anchor bars 4 and a rubber cushion block 5, and the specific implementation is as described below:

[0052] The steel box block 2 is a box-shaped steel structure. The web 10 and the top and bottom plates 9 are all connected by butt welds, and the upper cover plate 11 of the steel box block 2 is connected by fillet welds. The lower part of the steel box block 2 has no bottom plate, and the bottom of the steel box block 2 and the anchor plate 3 are connected by a combined weld of butt and fillet joints. A rubber cushion block 5 with a thickness ≥ 40 mm is pasted on the upper part of the steel box block 2.

[0053] In this embodiment, the transition pier capping beam 1 is a steel capping beam, and the anchor plate 3 is directly welded to the steel capping beam. The thickness of the anchor plate 3 ≥ 25 mm.

[0054] The longitudinal seismic block 12 is installed on the transition pier capping beam 1, longitudinally arranged on the mid-span side of the end cross beam 6, with a clear distance from the end cross beam 6 ≥ 200 mm; transversely arranged within the beam gap and close to the web of the main beam 7; longitudinal seismic blocks 12 are provided on both the front and rear sides of the transition pier capping beam 1 in the longitudinal direction of the bridge. A number of longitudinal seismic blocks 12 are provided on one side, and the number of longitudinal seismic blocks 12 is symmetrically arranged with respect to the transverse center line of the transition pier capping beam 1; the number of longitudinal seismic blocks 12 provided on one transition pier capping beam 1 should be determined according to calculations.

[0055] After a strong earthquake, if the steel box block 2 is deformed too much to be used, the steel box block 2 can be cut off from the anchor plate 3, and then a new steel box block 2 is welded in place.

[0056] Embodiment III

[0057] The present invention also provides a design method for the longitudinal seismic block of a flexible pier bridge to calculate the seismic force acting on the longitudinal seismic block 12 and design the longitudinal seismic block 12. The following formula is used to calculate the seismic force:

[0058]

[0059] The following formula is used to calculate the design bending moment and design shear force of the steel box block 2:

[0060] M s = 1.1F·h (2)

[0061] V s = 1.2×1.1F (3)

[0062] The following formula is used to calculate the design bending moment and design shear force of the anchor plate 3 for anchoring:

[0063] M s = 1.2×1.1F·h (4)

[0064] V s= 1.2×1.1F (5)

[0065] In formulas (1)-(5), M ye is the equivalent yield moment of the plastic hinge 13 at the bottom of the transition pier column 14 along the longitudinal direction of the bridge; H is the distance from the center of the pier plastic hinge 13 to the top of the transition pier capping beam 1; h is the distance from the seismic force acting point of the steel box bumper 2 to the top of the transition pier capping beam 1; F is the seismic force acting on the steel box bumper 2; M s is the design moment; V s is the design shear force; in the calculations of the seismic force, the design moment and design shear force of the steel box bumper 2, and the design moment and design shear force of the anchorage of the anchor plate 3, the standard values of the strength of all materials are taken.

[0066] The working principles of Embodiment 1 and Embodiment 2 are as follows:

[0067] For a flexible pier bridge transition pier, a longitudinal sliding bearing 16 is generally provided. The main girders 7 on both sides of the upper part of the transition pier will longitudinally slide relative to the transition pier under the action of an earthquake. The two main girders 7 may move in the same direction or in opposite directions relative to each other. When a strong earthquake occurs, the displacement of the beam end of the main girder 7 is large. If the main girders 7 move in the same direction relative to each other, the end cross beam 6 of one side of the main girder 7 will hit the steel box bumper 2 in the longitudinal seismic bumper 12. Due to the relatively thick rubber cushion block 5, the seismic force acting on the steel box bumper 2 is relatively uniform and stable. Therefore, under the action of the seismic force, the longitudinal seismic bumper 12 drives the transition pier to move together with the main girder 7, so that the transition pier participates in resisting the earthquake action; when the seismic force is very large, the bottom of the transition pier reaches the equivalent yield moment. At this time, the longitudinal seismic bumper 12 is intact. Therefore, driven by the longitudinal seismic bumper 12, the transition pier undergoes a large displacement along with the main girder 7, but the beam-drop does not occur. If the two main girders 7 move in opposite directions relative to each other, in the extreme case, the end cross beams 6 of the two main girders 7 both hit the corresponding longitudinal seismic bumpers 12. Due to the limitation of the longitudinal seismic bumpers 12, the seismic effects of the two main girders 7 will both be reduced; when the seismic force is very large, the steel box bumpers 2 in the structures of the two longitudinal seismic bumpers 12 yield, which will consume a large amount of seismic energy and reduce the seismic effect. At the same time, the upper part of the steel box bumper 2 is still intact, and there is still a long distance between the beam end of the main girder 7 and the edge of the transition pier capping beam 1. During the movement, the seismic energy will be further greatly weakened, so the beam-drop will not occur. Since the anchor plate 3 in the longitudinal seismic bumper 12 is designed according to the capacity protection relative to the steel box bumper 2, the anchor plate 3 will not be damaged. After the earthquake, if the steel box bumper 2 has a large yield deformation and cannot be used, the steel box bumper 2 can be cut off at the anchor plate 3, and then a new steel box bumper 2 can be welded in place, which is very convenient. Therefore, the longitudinal seismic bumper 12 of the present invention has the advantages of improving the overall seismic performance of the flexible pier bridge, preventing beam-drop, and being convenient for restoration.

[0068] It is apparent to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Accordingly, all changes that fall within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

[0069] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only includes an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A longitudinal seismic block design method for flexible pier bridges, where the longitudinal seismic block is installed between the transition pier capping beam and the main beam of the flexible pier bridge, and is characterized in that: The longitudinal seismic block includes: a steel box block, an anchor plate, anchor bars and a rubber cushion block; The transition pier capping beam is connected to the steel box block through the anchor plate or the combination of the anchor plate and the anchor bars; A rubber cushion block is pasted on the upper part of the steel box block; The longitudinal seismic block is longitudinally arranged on the mid-span side of the end cross beam on the main girder, and the clear distance from the end cross beam is ≥200 mm; the longitudinal seismic block is transversely arranged in the beam-to-beam gap and is close to the main girder web; Longitudinal seismic blocks are provided on both the front and rear longitudinal sides of the transition pier capping beam. A number of longitudinal seismic blocks are provided on one side, and the number of longitudinal seismic blocks is symmetrically arranged with respect to the transverse center line of the transition pier capping beam; The steel box block is a box-shaped steel structure. The web plate is connected to the top and bottom plates by butt welds. The upper cover plate of the steel box block is connected by fillet welds. The lower part of the steel box block has no bottom plate. The bottom of the steel box block is connected to the anchor plate by a combination of butt and fillet welds; The design method of the longitudinal seismic block includes: S1. Calculate the seismic force acting on the longitudinal seismic block; the calculation method of the seismic force is: S2. Calculate the design bending moment and design shear force of the steel box block on the longitudinal seismic block through the seismic force; the calculation methods of the design bending moment and design shear force of the steel box block are: M s = 1.1F·h (2) V s = 1.2 × 1.1F (3) S3. Calculate the design bending moment and design shear force of the anchor plate anchorage through the seismic force; the calculation methods of the design bending moment and design shear force of the anchor plate anchorage are: M s = 1.2 × 1.1F·h (4) V s = 1.2 × 1.1F (5) In formulas (1) to (5), M ye is the equivalent yield moment of the pier column bottom plastic hinge bending along the longitudinal direction of the bridge; H is the distance from the plastic hinge center of the bridge pier to the top of the capping beam of the transition pier; h is the distance from the seismic force acting point of the steel box block to the top of the capping beam of the transition pier; F is the seismic force acting on the steel box block; M s is the design moment; V s is the design shear force; all material strengths are taken as standard values in the calculations of the seismic force, the design moment and design shear force of the steel box block, and the design moment and design shear force of the anchor plate anchorage.

2. The design method of the longitudinal seismic block for the flexible pier bridge according to claim 1, wherein: When the transition pier capping beam is a concrete capping beam, the anchor plate is connected to the concrete capping beam through anchor bars; when the transition pier capping beam is a steel capping beam, the anchor plate is welded to the steel capping beam.

3. A design method for longitudinal seismic retaining blocks of flexible pier bridges according to claim 1, characterized in that: The thickness of the anchor plate is ≥25 mm, and the thickness of the rubber cushion block is ≥40 mm.

Images