CN104652293B - A kind of Cable-Stayed Bridge Structure for reinforcing PSC Continuous Box Girder Bridge and construction method - Google Patents

Abstract

The invention relates to a cable-stayed bridge structure and a construction method for strengthening a PSC continuous box girder bridge. To improve the bearing capacity of beam bridges. The section steel is anchored to the top plate of the box girder through the connecting device. The bridge pylon is welded on the composite section steel, and the bridge tower and the composite section steel are connected by stay cables. In traditional cable-stayed bridges, the main girder in the mid-span mid-span cable-free area is subject to a large axial tension; while the main girder at the root of the pylon is subject to a large axial tension. The present invention anchors the combined section steel on the main girder, and connects the combined section steel with a cable, so that the excessive axial tension and pressure act on the combined section steel without adverse effects on the main beam, and the combined section steel is under the action force of the cable Provide upward lifting force to the main beam, enhance the bending resistance and shear resistance of the main beam, reduce the deflection deformation of the main beam, and inhibit the development of cracks in the main beam. The invention is efficient, simple, safe and economical.

Description

A cable-stayed bridge structure and construction method for strengthening PSC continuous box girder bridge

technical field

The present invention relates to a cable-stayed bridge structure and construction method (PSC: prestressed reinforced concrete) for strengthening a PSC continuous box girder bridge, the reinforced structure of the invention includes bridge towers, stay cables and a bridge placed on the centerline of the bridge deck Combined section steel, through the cable-stayed bridge system, changes the stress condition of the PSC continuous girder bridge, thereby improving its bearing capacity. The section steel is anchored to the top plate of the box girder through the connecting device. The bridge tower is welded on the composite section steel, and the bridge tower and the composite section steel are connected by cables. In traditional cable-stayed bridges, the main girder in the mid-span mid-span cable-free area is subject to a large axial tension; while the main girder at the root of the pylon is subject to a large axial tension. Excessive tension and pressure have adverse effects on the main beam. In the present invention, the composite section steel is anchored on the main beam, and the composite section steel is connected with a drag cable, so that the excessive axial tension and pressure all act on the composite section steel, which has no adverse effect on the main beam, and the composite section steel exerts force on the cable The lower part provides upward lifting force to the main girder, which enhances the bending resistance and shear resistance of the main girder, reduces the deflection deformation of the main girder, and can inhibit the development of cracks in the main girder. The reinforcement method of this cable-stayed bridge can make it more efficient, simple, safe and economical to increase the bearing capacity of the PSC continuous box girder bridge.

Background technique

At present, the main technical methods for strengthening and transforming bridges at home and abroad are as follows:

1) Increased section reinforcement method: This method increases the bearing capacity and stiffness of the component by increasing the section of the concrete component and increasing the reinforcement. Depending on the purpose and requirements of the reinforcement, it can be reinforced mainly by increasing the section, or by increasing the reinforcement. During reinforcement, it is necessary to ensure that the old and new concrete are well bonded. But the disadvantage of this method is also very obvious, because the structure self-weight is inevitably increased in the reinforcement, so it is not very suitable for the long-span prestressed concrete continuous box girder bridge studied by the present invention.

2) Reinforcing method of thickening the bridge deck: This method is to chisel out the original bridge deck pavement layer and re-lay a layer of concrete or reinforced concrete reinforcement layer. This method can repair bridge decks that have cracks, peeling and other diseases, and can increase the effective height of the original main girder, increase the bending resistance of the main girder, and improve the lateral load distribution of the hinged girder, thereby improving the bearing capacity of the bridge. However, this method increases the dead load bending moment due to the increase of the bridge's own weight, and is still limited by the allowable stress of the steel bars in the tension area of the lower edge of the original bridge structure. Therefore, the reinforcement method is generally only suitable for T-shaped bridges with small spans. Girder bridge or slab girder. This method is also not effective for long-span prestressed concrete continuous box girder bridges.

3) Increased beam rib reinforcement method: The increased beam rib reinforcement method is often used to strengthen T-beams. For this type of bridge, the lower end of the beam can be widened to increase the cross-sectional area, and add the main reinforcement in the new concrete section. However, the self-weight of the structure is also increased after the section is enlarged, and it is not suitable for the reinforcement of long-span prestressed concrete continuous box girder bridges.

4) Paste carbon fiber reinforcement method: Paste carbon fiber reinforcement method is to use the adhesive carbon fiber reinforced composite material (CFRP) to paste on the concrete surface of the beam body. Joint force, thereby improving the bearing capacity and stiffness of the bridge, played a role in reinforcement. However, due to the need to paste the reinforced composite material to the bottom of the beam during construction, workers need to stand on the bracket to apply the adhesive, which is extremely inconvenient to operate and difficult to guarantee the quality of the paste. At the same time, since the reinforced composite material only participates in the work when the bridge is subjected to live load, it is a passive force. When the reinforced composite material plays a role, the downward deflection of the reinforced beam is often already large. Therefore, in the large-span prestressed concrete The reinforcement effect of continuous box girder bridge is not ideal when large deflection deformation has occurred.

5) Reinforcement method of adding load-bearing components: When the bearing capacity of the bridge cannot meet the requirements, but the beam structure is basically intact, in order to increase the bearing capacity, the method of adding load-bearing components can be adopted, and the bearing capacity and stiffness of the newly added components are relatively large. During construction, it is necessary to ensure that the connection between the old and new components is reliable so that they can participate in the force action together. This reinforcement method will have a great impact on traffic during construction, and there is a problem that the force of the old and new components is not synchronized.

6) Paste steel plate reinforcement method: use epoxy resin series adhesive to paste the steel plate on the tensile side or weak part of the reinforced concrete structure, so that the steel plate and the original structure form a whole joint force, and improve the bending resistance and anti-corrosion of the structure. The shear capacity and stiffness can improve the stress state of the steel bars and concrete of the original structure, and limit the development of cracks, thereby improving the bearing capacity and durability of the bridge. Similar to the pasting carbon fiber reinforcement method, the pasting steel plate reinforcement method is also passive reinforcement, and it is not suitable for long-span prestressed concrete continuous box girder bridges that have undergone large deflection deformation.

7) External prestress reinforcement method: External prestress reinforcement beam bridge is a reinforcement method that changes the original stress state of the beam body. When the bearing capacity of the bridge structure is insufficient or the load level needs to be increased, the external prestressing reinforcement method can be considered. This method is to arrange prestressed steel bars or steel wire bundles outside the beam body to improve the stress condition of the bridge. This method often requires the installation of prestressed anchorage devices on the beam body, causing damage to the beam body; local excessive compressive stress may exceed the limit, causing safety hazards.

8) Change the bridge system reinforcement method: This reinforcement method is to reduce the internal stress of the main girder and improve the bearing capacity by changing the bridge structure system. Such as adding supports or piers under simply supported beams; connecting two adjacent spans of simply supported beams to form continuous beams. In the construction of this reinforcement method, it is often necessary to work under the bridge to add piers, thereby occupying the clearance under the bridge and affecting traffic or bridge flood discharge. This reinforcement method has a better effect and is a common measure to solve the problem of temporarily passing overweight vehicles both at home and abroad. After heavy vehicles pass, remove temporary piers or supports. The reinforcement method in the present invention belongs to this method.

9) Anchor shotcrete reinforcement method: The anchor shotcrete reinforcement method is to use mechanical spraying of high-pressure, high-speed concrete onto the anchored steel mesh to make it solidify and harden to form a reinforced concrete structure, increasing the strength and stiffness of the original bridge structure. However, this reinforcement method is widely used in the reinforcement of masonry masonry arch bridges, and can better solve the common diseases of stone arch bridges.

With the development of society and economy, the road traffic volume in our country has increased rapidly. At the same time, the relatively low design load standard value in the previous codes has led to a relatively insufficient carrying capacity of a large number of bridges, and there are potential safety hazards that cannot be ignored. In view of the fact that the current conventional bridge reinforcement methods still have some deficiencies in improving the bearing capacity of long-span prestressed concrete continuous box girder bridges, this invention takes the existing long-span prestressed concrete box girder bridges as the research object, collects and analyzes the bearing capacity of the existing long-span prestressed concrete box girder bridges. In order to improve the bearing capacity of PSC continuous box girder bridge, it is more efficient, simple, safe and economical.

Contents of the invention

The purpose of the invention is to improve the benefit of strengthening the PSC continuous box girder bridge, and design a kind of cable-stayed bridge structure and construction method for strengthening the PSC continuous box girder bridge. The structural features of the present invention are as follows:

The strengthening principle of cable-stayed bridge structure:

The box girder roof 1 and the combined steel 2 are anchored together by the vertical prestressed steel bar 3 and the connecting device 10, the cable 4 connects the bridge tower 5 and the combined steel 2, the bridge tower 5 is welded on the combined steel 2, and the 4 pairs of the cables are combined The section steel 2 exerts tensile force, so that the combined section steel 2 is subjected to axial force and vertical lifting force. Due to the anchoring effect, the box girder roof 1 also receives the vertical lifting force, and the bridge tower 5 receives the pulling force of the cable 4, and the bridge tower 5 transmits the force To the combined section steel 2 above the bridge pier, the combined section steel 2 then transmits the load to the No. 0 block 6 of the box girder, and the No. 0 block 6 bears the force and transmits it to the middle fulcrum support 7, and then transmits the load to the foundation through the pier 8 and the foundation 9. The combined section steel is subjected to axial pressure in the areas AB and CD, and axial tension in the cable-free area BC. In this way, the excessive pressure and tension are borne by the combined section steel instead of the main beam itself, which avoids the impact of excessive axial force on the main beam. Adverse effects, while the main girder is subjected to an upward lifting force. Therefore, the bending and shearing resistance of the main girder of the PSC continuous box girder bridge can be enhanced, the deflection deformation of the main girder can be reduced, and the development of cracks in the main girder can be inhibited.

The cable-stayed bridge structure includes:

Box girder roof 1, combined section steel 2, vertical prestressed steel bars 3, cables 4, bridge towers 5, block 0 6, middle fulcrum supports 7, bridge piers 8, foundation 9, connecting devices 10, first drilling 11 , cable anchor head 12, cable anchor block 13, baffle plate 14, local reinforced steel plate 15, steel anchor beam 16, corbel 17, cable anchor head 18, box girder 19, second drill hole 20, vertical steel plate 21, the lower horizontal steel plate 22 and the upper horizontal steel plate 23.

Before reinforcement, the box girder 19 acts on the pier 8, the pier 8 acts on the foundation 9, and the foundation 9 acts on the foundation. The box girder 19, the pier 8 and the foundation 9 form a standard three-span continuous box girder bridge.

The combined section steel 2 is welded by a vertical steel plate 21, a lower horizontal steel plate 22, an upper horizontal steel plate 23, a cable anchor block 13, a baffle plate 14, and a local reinforced steel plate 15. The box girder 19 is a PSC material structure. Use machinery to punch out the first drill hole 11 on the lower horizontal steel plate 22, connect the connecting device 10 with the vertical prestressed steel bar 3, and anchor the combined section steel 2 and the box girder top plate 1 as a whole.

The bridge tower 5 is welded on the composite section steel 2, and the bridge tower 5 is made up of a steel anchor beam 16 and a corbel 17. The steel anchor beam 16 is used to bear the horizontal force of the stay cable 4, and the vertical component force of the stay cable 4 is transmitted to the bridge tower 5 by the corbel 17. Such a structure makes the bridge tower 5 be in a compressed state as much as possible. The steel anchor crossbeam 16 and the corbel 17 arranged in this way prevent the connection between the bridge tower and the cable from being damaged due to excessive stress.

Dragline is made up of dragline 4, dragline anchor head 12, dragline anchor head 18. The drag cable anchor head 12 and the drag cable anchor head 18 anchor the drag cable 4 to the combined section steel 2 and the bridge tower 5 respectively.

According to the structural features of the above invention, its construction method is as follows:

On the standard three-span continuous box girder bridge formed by box girder 19, bridge pier 8 and foundation 9, the composite section steel 2 is processed according to Fig. 8, wherein the upper horizontal steel plate 23 is welded to the composite section steel 2 at the end of construction. Drill out the first borehole 11 at the design position of the combined section steel 2 . The vertical prestressed steel bar 3 is connected by the connecting device 10 , and after the combined section steel 2 is arranged on the center line of the bridge deck, the combined section steel 2 is anchored on the box girder roof 1 by the connecting device 10 .

Process the 5 sections of the bridge tower, splice and weld the 5 sections of the bridge tower on site and install the steel anchor beam 16. Utilize winch, pulley to promote each stay cable, after pulling in place in bridge tower duct, fix with stay cable anchor head 18. Install the stay cables at the beam end equally, and use the stay cable anchor head 12 to anchor after utilizing the jack to stretch each stay cable. According to the structure form and disease degree of the bridge, adjust the force of each cable to keep the bridge in a good stress state. Install and weld the horizontal steel plate 23 at last, and carry out antirust treatment to all steel members.

Beneficial effects of the present invention:

The present invention relates to a cable-stayed bridge structure and a construction method for strengthening a PSC continuous box girder bridge. The continuous box girder bridge achieves active reinforcement through the combined steel, stay cables and bridge towers for strengthening the PSC continuous box girder bridge. It overcomes the shortcomings of traditional reinforcement methods such as poor reinforcement effect and large local damage to the original bridge structure. It can effectively improve the bending and shear resistance of the main girder, reduce the deflection deformation of the main girder, and inhibit the development of cracks in the main girder.

The machinery and materials involved in the present invention are very common in bridge construction, so that the practicability of this reinforcing method is guaranteed. Bridge pylons, combined section steel, and steel anchor beams are prefabricated in the factory and assembled on site. The processing quality can be guaranteed, and the construction period can be effectively shortened. The construction area is mainly in the central divider area of the bridge deck, which occupies less space, does not interrupt traffic, and has little impact on traffic. It is suitable for bridge reinforcement with heavy traffic tasks.

Description of drawings

Fig. 1 Structural diagram along the bridge direction of the three-span PSC continuous box girder bridge before reinforcement;

Figure 2 is the bridge elevation of the reinforced cable-stayed bridge system;

Figure 3 is the 1/2 elevation of the bridge of the cable-stayed bridge system after strengthening;

Figure 4 cross-sectional view of the reinforced front box girder;

Figure 5 cross-sectional view of the reinforced box girder;

Figure 6 Sectional Elevation of Combined Sectional Steel (Before Installing the Upper Horizontal Steel Plate);

Figure 7 The three-dimensional diagram of the combined steel segment;

Figure 8 Layout of the bridge tower in the transverse direction.

Figure 9 is a schematic diagram of the force before and after the bridge is strengthened.

a) Continuous girder bridge elevation

b) Force diagram of continuous girder bridge under self-weight

c) Bending moment diagram of continuous girder bridge under its own weight (unit: kN m)

d) After reinforcement, the cable-stayed bridge system is subjected to upward lifting force

e) After strengthening, it becomes the bending moment diagram of the cable-stayed bridge system under the action of its own weight (unit: kN m)

Among them, box girder top plate 1, combined section steel 2, vertical prestressed steel bar 3, cable 4, bridge tower 5, block 0 6, middle pivot support 7, bridge pier 8, foundation 9, connection device 10, first drilling 11. Cable anchor head 12, cable anchor block 13, baffle plate 14, local reinforced steel plate 15, steel anchor beam 16, corbel 17, cable anchor head 18, box girder 19, second drill hole 20, vertical Steel plate 21, lower horizontal steel plate 22, upper horizontal steel plate 23.

detailed description

Below in conjunction with accompanying drawing and specific embodiment the present invention will be further described;

Utilize a kind of cable-stayed bridge structure and construction method for strengthening PSC continuous box girder bridge of above-mentioned design, concrete steps are as follows:

Step 1: Consult the data and get the bridge structure and disease status through actual measurement, survey and get the bearing capacity of the pre-reinforced bridge, which is used to get the stress of the bridge tower, cable, combined steel, and connecting device, and then determine the components The required number, size, steel grade and specific layout.

Step 2: Determine the cable tension sequence and each tension force based on the stress conditions obtained in step 1 and the structural form of bridge towers, cables, and combined steel sections.

Step 3: According to the steps, the mechanical operation capacity of the construction site is considered together, and the bridge tower (segment), combined section steel (segment), and steel anchor beam are processed by the factory. The size of the drill hole is determined by the size of the connection device. Get some first boreholes 11 on the lower horizontal steel plate 22, chisel out the bridge deck pavement at the center line of the bridge deck, expose the vertical prestressed steel bar 3, utilize the connecting device 10 to connect the vertical prestressed steel bar 3, in the center of the bridge deck After the combined section steel 2 is arranged, the connecting device 10 is used to anchor the combined section steel 2 on the top plate 1 of the box girder.

Step 4: Install and weld the bridge tower segments to the composite steel 2 segment by segment. At the same time, a temporary working platform is installed on the bridge tower to facilitate the installation of the cables. The assembly accuracy and welding quality are strictly controlled during construction. In order to reduce the adverse effect of temperature on assembly and welding quality, the time period with moderate temperature should be selected for construction.

Step 5: Install pulleys and hoist cables on the bridge tower 5, pull the cables in order to be in place in the tunnel of the bridge tower 5, and anchor them with the cable anchor head 18. Install the other end of the drag cable on the combined section steel 2, and anchor it with the drag cable anchor head 12.

Step 6: The structural system of the bridge changes during the reinforcement process, resulting in redistribution of the internal force of the bridge structure, so the cable force needs to be adjusted. According to step 2, stretch the cables in sequence to the tension of each time. Whether the cable force of the cable is correct or not is one of the important factors affecting the reinforcement effect. A reliable method should be used to measure the cable force of the cable at each stage. If there is any deviation, it should be adjusted in time to avoid disadvantages to the bridge.

Step 7: The upper horizontal steel plate 23 (segment) drills the second drill hole 20 at the place where the cable passes through, splices it and then welds it. Anti-corrosion and anti-rust treatment are carried out on all steel components, and the reinforcement of the continuous girder bridge is completed.

In the present invention, the cable-stayed bridge system is adopted to reinforce the continuous girder bridge, and the axial force is applied to the combined section steel, and only a vertical upward lifting force is applied to the bridge. The stress in the present invention is described as follows, wherein the span of the bridge is 60m+90m+90m, the self-weight of the bridge is q=600kN/m, and the lifting force at each place is 1500kN.

Table 1 Force comparison table before and after reinforcement (unit: kN m)

Side span M pivot point middle span Before reinforcement 118846 -363461 244038 After reinforcement 95389 -227948 169551 After Reinforcement/Before Reinforcement 80.3% 62.7% 69.5%

Summary: From the force diagram in Figure 9 and the force comparison table, it can be seen that the internal force of the reinforced bridge is significantly reduced under the action of its own weight, and the bridge can be "load-reduced", which shows that the reinforcement method in the present invention has an obvious effect.

The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form, and any simple modification made to the above embodiments according to the technical essence of the present invention does not depart from the content of the technical solution of the present invention. , equivalent changes and modifications all still belong to the scope of the technical solution of the present invention.

Claims (3)

1. a cable-stayed bridge structure for strengthening PSC continuous box girder bridge, is characterized in that: comprise box girder top plate (1), combined section steel (2), vertical prestressed reinforcing bar (3), stay cable (4) , bridge tower (5), block No. 0 (6), middle fulcrum support (7), bridge pier (8), foundation (9), connection device (10), first borehole (11), first cable Anchor head (12), cable anchor block (13), baffle plate (14), local reinforced steel plate (15), steel anchor beam (16), corbel (17), second cable anchor head (18), Box girder (19), second borehole (20), vertical steel plate (21), lower horizontal steel plate (22) and upper horizontal steel plate (23); Before reinforcement, the box girder (19) acts on the pier (8), the pier (8) acts on the foundation (9), the foundation (9) acts on the foundation, the box girder (19), the pier (8) and the foundation ( 9) form a continuous box girder bridge; The combined section steel (2) is welded by vertical steel plate (21), lower horizontal steel plate (22), upper horizontal steel plate (23), cable anchor block (13), baffle plate (14), and local reinforced steel plate (15) Use machinery to punch out the first borehole (11) on the lower horizontal steel plate (22), the connecting device (10) is connected with the vertical prestressed steel bar (3), and the composite section steel (2) and the box girder roof (1) are anchored as one; The bridge tower (5) is welded on the composite section steel (2), and the bridge tower (5) is composed of a steel anchor beam (16) and a corbel (17); the steel anchor beam (16) is used to bear the level of the stay cable (4). Force, the vertical force component of stay cable (4) is transmitted to bridge tower (5) by corbel (17); Stay cable is made up of stay cable (4), the first stay cable anchor head (12), the second stay cable anchor head (18); the first stay cable anchor head (12), the second stay cable anchor head (18) respectively Anchored on the composite section steel (2) and the bridge tower (5). 2. a kind of construction method that is used to reinforce the cable-stayed bridge structure of PSC continuous box girder bridge according to claim 1, is characterized in that, construction step is as follows: Step 1: Consult the data and get the bridge structure and disease status through actual measurement, survey and get the bearing capacity of the pre-reinforced bridge, which is used to get the stress of the bridge tower, cable, combined steel, and connecting device, and then determine the components The number, size, steel grade and specific layout of the required number; Step 2: Determine the cable tension sequence and each tension force from the stress situation obtained in step 1 and the structural form of bridge towers, cables, and combined steel sections; Step 3: According to the steps, the mechanical operation capacity of the construction site is considered together, and the bridge tower, combined section steel, and steel anchor beam are processed by the factory; the size of the drill hole is determined by the size of the connecting device; several first drill holes are drilled on the lower horizontal steel plate (22) (11), remove the bridge deck pavement at the center line of the bridge deck, expose the vertical prestressed steel bar (3), use the connecting device (10) to connect the vertical prestressed steel bar (3), and arrange the combined section steel on the bridge deck center line After (2), the combined section steel (2) is anchored on the box girder roof (1) by using the connecting device (10); Step 4: install and weld the bridge tower segments segment by segment to the composite steel (2); at the same time, install a temporary working platform on the bridge tower to facilitate the installation of the cables; Step 5: Install pulleys and hoist cables on the pylon (5), pull the cables in order to put them in place in the tunnel of the pylon (5), and anchor them with the second cable anchor head (18); pull the cables The other end is installed on the combined section steel (2), and is anchored with the first cable anchor head (12); Step 6: Stretch the cables in sequence to the pulling force of each time; Step 7: The upper horizontal steel plate (23) drills the second drill hole (20) at the place where the cable passes, and welds it after splicing; anticorrosion and antirust treatment are carried out to all steel components, and then the reinforcement of the continuous girder bridge is completed. 3. a kind of cable-stayed bridge structure for strengthening PSC continuous box girder bridge according to claim 1, is characterized in that: it except being applicable to standard three spans and being the PSC continuous box girder bridge of single box double chamber, It is also applicable to the combination of two-span beams, three-span beams, and multi-span beam span types with single-box single-chamber, single-box double-chamber, single-box multi-chamber, and multi-box multi-chamber chamber types to form various structures The PSC continuous box girder bridge.