CN203222727U - Bridge of variable cross-section case and made by pre-stressed concrete - Google Patents

Abstract

The utility model discloses a prestressed concrete variable cross-section box bridge, in which a horizontal anchor plate is arranged at the corresponding girder height position of the bottom plate at the mid-span position; above the horizontal anchor plate, upward bending anchors are arranged longitudinally along the box girder in the direction from the mid-span to the bridge pier slab; in the mid-span to 3L/8 cross-section section, the upward-bending anchorage plate, horizontal anchorage The floor cables are arranged inside the horizontal anchor plates. The above-mentioned bridge provided by the utility model can reduce the hollowing rate of the floor section and the flat bending amplitude of the prestressed floor cables, and the upward radial component force of the prestressed floor cables in the upward bend can offset the secondary dead load and the vehicle load force.

Description

A Prestressed Concrete Variable Section Box Bridge

technical field

The utility model relates to the technical field of civil engineering bridges, in particular to a prestressed concrete variable-section box bridge. the

Background technique

Long-span prestressed concrete variable-section box bridges are widely used bridge types at present, and continuous beams and continuous rigid frame bridges are the most common, and they are often constructed by hanging basket cantilever casting method. the

As shown in Figure 1 to Figure 1-2, Figure 1 is a schematic structural diagram of a long-span prestressed concrete variable-section box bridge with floor cables bent down, and Figure 1-1 is the A-A section of the bridge shown in Figure 1 Structural schematic diagram, Figure 1-2 is the structural schematic diagram of the B-B section of the bridge shown in Figure 1. the

The commonly used cross-section form of this kind of variable-section box bridge is single-box single-chamber cross-section. Due to the requirement of force, the beam height increases from the mid-span L/2 cross-section to the fulcrum cross-section, resulting in the lower edge of the floor 01 being arched. From the mid-span to the fulcrum of the cantilever root at the pier 06, the clearance of the box room increases, the beam height increases, the bottom plate 01 gradually thickens, the web 02 is partially thickened near the fulcrum section, and the longitudinal direction of the bottom plate 01 is arched. Base plate 01 arch rise-span ratio (sag height/main span diameter) is generally about 1/20. The sawtooth block 03 is used for anchoring positive moment cables. the

As shown in Figure 2 to Figure 2-2, Figure 2 is a structural schematic diagram of the longitudinal arrangement of steel cables of a long-span prestressed concrete variable-section box bridge with floor cables bent down, and Figure 2-1 is A-A of the bridge shown in Figure 2 Schematic diagram of the cross-sectional structure, Figure 2-2 is a schematic structural diagram of the B-B cross-sectional plane of the bridge shown in Figure 2. the

Since the positive moment cables are arranged in the bottom plate 01, the positive moment cables are often called the bottom plate cables 05. Since the elevation of the bottom plate 01 is arched, this structural arrangement causes the elevation of the bottom plate cables 05 to also be arched, and the bottom plate Cable 05 is arranged in a downward bend, and the rise-span ratio is generally about 1/20. Since the floor cable 05 is stretched and its two ends are anchored on the sawtooth block 03, the tensioned floor cable 05 must generate a downward radial force. When the span of the bridge increases, measures such as increasing the beam height, thickening the floor 01, thickening the web 02, and adding cables are used to set it up. However, increasing the beam height and increasing the cables will further increase the radial force of the floor cable 05. Increase, this unreasonable structure leads to the problem of unfavorable force, the larger the span of the bridge, the more serious this problem is, which restricts the development of this type of bridge. the

Table 1 analyzes the relationship between the radial force of the floor cable 05 and the load of the highway lane when the span is enlarged. the

Table I

It can be seen from Table 1 that when the span increases, the radial force of the floor cable 05 increases sharply, and the ratio of the downward radial force of the floor cable to the roadway load also increases sharply. the

Increase the span and increase the distribution of cables. Generally, the floor cable 05 is arranged in a single layer, and the horizontal hollowing rate of the floor increases sharply. In Table 2, when the span is increased, the relationship between the total diameter and length of the bottom plate cable 05 and the width of the bottom plate is analyzed. the

Table II

It can be seen from Table 2 that when the span increases, the diameter of the pipeline increases, and the ratio of the diameter of the pipeline to the length of the bottom plate also increases. the

Specifically, the main defects of the downward bending arrangement of the continuous rigid frame bridge floor cable described above are as follows:

(1) The downward radial force of the arched floor cable 05 generates shear force along the bridge direction at the position of the corresponding floor 01. Since the floor 01 in the middle of the span is thin, generally 25-40cm, the transverse reinforcement is configured according to the structure, and the floor is bent down If the downward radial force of the cable 05 is too large, it will easily lead to shear cracks along the bridge direction in the bottom plate 01 of the middle span, and seriously cause the bridge bottom plate 01 to crack and fail. It can be seen from Table 1 that when the span increases, the downward radial force of the floor cable 05 increases sharply. The radial force of the floor cable 5 of the bridge with a main span of 100 meters is about 1.5 times the load of the road lane, and the main span of 200 meters is about 1.5 times that of the roadway load. The radial force of the bridge floor cable 5 is about 4 times of the roadway load. This makes the disease more serious. the

(2) It can be seen from Table 2 that when the span increases, the amount of floor cables 05 increases sharply. In the prior art, floor cables 05 are generally arranged in a row in a single layer. On the horizontal section of the center of the floor cables 05, the main span is 200 meters The total diameter and length of the bridge pipes account for about 60% of the width of the floor. It shows that there is no concrete in 60% of the cross-sectional width of the bottom plate when the prestress is stretched. When the span increases, the downward radial force of the floor cable 05 increases sharply, while the effective cross-sectional area of the load decreases sharply. This is one of the main reasons for the unreasonable structure of the floor to crack or break. the

(3) The downward radial force of the floor cable 05 also directly causes the web 02 in the corresponding section to be stretched, which can easily lead to the main tensile stress cracks in the web 02. Usually, such defects are more common in the range from L/4 section to L/2 section. Common, related to this, generally the beam height from L/4 section to L/2 section is small, the vertical prestress loss is large, and the control is difficult. If the vertical effective prestress is not reliable, the cracking disease will be aggravated. the

(4) Since the floor cable 05 needs to be anchored at the junction of the web 02 and the bottom plate 01 due to structural requirements to shorten the force transmission route, the anchorage area of the floor cable 05 for long-span bridges often extends from near the mid-span to L/ Near the 8 section, the positive bending moment area of the variable section box bridge constructed by the long-span cantilever pouring method is usually between the L/4 section and the mid-span L/2 section, and the mid-span L/2 section is the largest, and the positive bending moment area near the L/8 section is The bending moment is generally small or negative. In order to ensure the force of the positive bending moment in the mid-span and the needs of the anchorage structure, the downward bending floor cable 05 arranged between the L/4 section and the L/8 section does not match the force of this section. The L/4 section to L/8 section beams are tall, the eccentricity is large, and the downward radial force is the largest, so the negative effect is large. the

(5) When the span increases, the amount of floor cable 05 increases sharply, and the floor cable 05 located near the transverse centerline of the box girder needs to be flat-bent to the junction of web 02 and floor 01 for anchorage to shorten the force transmission route. The horizontal force tension generated by excessive flat bending directly leads to the cracking of the bottom plate 01. the

(6) The downward radial force of the floor cable 05 directly causes the mid-span deflection. the

(7) The positioning of the arched down-curved floor cable 05 is difficult, the construction is not easy to control, and the prestress loss of the curved cable is large, which is uneconomical. the

(8) The downward radial force of floor cable 05, the dead load of the first and second phases, and the load of the driveway are all downward, which intensifies the shrinkage and creep effect of concrete, resulting in continuous downward deflection during the mid-span operation period. the

Therefore, in order to solve the problems caused by the above-mentioned bridges, a prestressed concrete variable-section box bridge with floor cables arranged horizontally is proposed, as shown in Fig. 3 to Fig. 4-2. Schematic diagram of the layout of the long-span prestressed concrete variable cross-section box bridge. Figure 3-1 is the structural schematic diagram of the A-A section view of the bridge shown in Figure 3. Figure 3-2 is the structural schematic diagram of the B-B section view of the bridge shown in Figure 3. Figure 4 is In the prior art, there is a structural schematic diagram of the longitudinal arrangement of steel cables in a long-span prestressed concrete variable-section box bridge with floor cables arranged horizontally. Fig. 4-1 is a structural schematic diagram of the A-A section view of the bridge shown in Fig. Schematic diagram of the structure of the B-B section view of the bridge shown in 4. the

The above-mentioned technical scheme of horizontally arranging the floor cables of the long-span prestressed concrete variable-section box bridge is as follows: the horizontal anchor plate 14 is arranged longitudinally at the position corresponding to the girder height of the mid-span mid-slab 11 of the box girder, and the mid-span section L/2 to 3L/ 8 section section, the horizontal anchor plate 14 is integrated with the bottom plate 11, and the rest of the position is separated from the bottom plate 11, and the bottom plate cable 15 is arranged in the horizontal anchor plate 14. the

Compared with the above-mentioned long-span prestressed concrete variable-section box bridge with floor cables bent down, the characteristics of prestressed concrete variable-section box bridges with horizontal floor cables are: (1) In bridges with horizontal longitudinal slopes, due to A horizontal anchor plate 14 is provided, and the floor cables 15 are arranged in the horizontal anchor plate 14, so that the mid-span positive moment floor cables 15 are arranged horizontally, eliminating the downward radial force of the mid-span positive moment cables in the prior art. (2) The floor cables 15 are arranged in the horizontal anchor plate 14. Compared with the traditional long-span prestressed concrete variable-section box bridge with cantilever construction method, the bending moment envelope diagram is more consistent, and the force Reasonable, it can overcome the large positive bending moment from the L/2 section to the 3L/8 section in the mid-span, and it can be compressed near the center near the L/4 section where the positive and negative bending moments are small, and it can resist part of the bending moment near the L/8 section. negative bending moment. (3) The bridge floor cables 15 are arranged in the horizontal anchor plate 14, which simplifies the structural design and construction of the floor in the prior art, and improves the stress on the floor. the

However, with such a setting, the following problems will arise: (1) The floor cables 15 of the long-span prestressed concrete variable-section box bridge are arranged horizontally and the bending moment of the long-span prestressed concrete variable-section box bridge using the cantilever construction method The envelope diagram (usually parabolic) cannot be completely matched, and there is a certain deviation. (2) In order to reduce the pier height of the side spans and save costs, improve the clearance under the main span bridge or overcome the deflection in the middle of the span, the main span is generally set with a two-way longitudinal slope of about 2%. On bridges with longitudinal slopes, for the convenience of design and construction, generally The horizontal anchor plate 14 is arranged parallel to the bridge deck, and the floor cables 15 are arranged on a longitudinal slope of about 2% in both directions, and there is part of the downward radial force on the floor cables 15 . (3) The horizontal arrangement of floor cables 15 cannot provide an upward force component, and cannot balance the second-phase dead load and the downward force of the lane load. (4) There is no control method to eliminate or reduce the deflection deformation of the main girder caused by the second-stage dead load, and the deformation of the main span is difficult to control after closing. (5) On bridges with two-way longitudinal slopes in the main span, the downward radial force of the floor cables 15, the first-phase and second-phase dead loads, and the driveway loads are all downward, which intensifies the concrete shrinkage and creep effect, resulting in Must continue to scratch. (6) It can be seen from Table 2 that when the span increases, the amount of floor cables 15 increases sharply, and the diameter and length of the bridge pipes with a main span of 200 meters account for 60% of the width of the floor 11. It shows that 60% of the cross-sectional width of the base plate 11 has no concrete. When the span increases, the effective load-carrying section decreases sharply, which may cause the bottom plate 11 to be cracked or broken. (7) When the span increases, the amount of floor cables 15 increases sharply, and the floor cables 15 located near the transverse centerline of the box girder need to be bent flat to the junction of the web 12 and the bottom plate 11 to shorten the force transmission route. The horizontal force tension generated by excessive flat bending directly leads to cracking of the bottom plate 11 . the

Utility model content

Aiming at the defects and insufficiencies of the prior art, the purpose of this utility model is to provide a method to eliminate or reduce the influence of the second-stage dead load and the impact of the driveway load on the deflection deformation of the main girder, reduce the horizontal hollowing rate of the cross-section cable, and reduce the stress on the structure. A prestressed concrete variable-section box bridge with more reasonable methods and convenient construction. the

In order to achieve the above object, the technical solution of the utility model is:

A kind of prestressed concrete box bridge with variable cross-section, including pier, base plate, web plate, base plate cable, a horizontal anchor plate is set at the position of the beam height of the base plate at the mid-span position; above the horizontal anchor plate, from the mid-span to the The direction of the bridge pier is provided along the longitudinal direction of the box girder with an upward-curved anchor plate; in the mid-span to 3L/8 section section, the upward-curved anchor plate, the horizontal anchor plate and the bottom plate are integrated, and the remaining positions are separated; The thickness of the above-mentioned upward bending anchor plate and the thickness of the horizontal anchor plate are the same as the thickness of the mid-span part of the bottom plate; the prestressed floor cables are arranged in two layers, and one layer of the prestressed floor cables is arranged upward Inside the upwardly curved anchoring plate, another layer of the prestressed floor cable is arranged horizontally inside the horizontal anchoring plate; The bottom plate cable is tensioned and anchored longitudinally and symmetrically by the sawtooth block at the intersection of the horizontal anchor plate or the upwardly bent anchor plate and the web. the

Preferably, the upwardly curved anchoring plate is arranged horizontally at the construction section near the mid-span closing section, and is arranged as an oblique straight line or curve according to the upward inclination, and the transition section between the mid-span horizontal section and the inclined section of the upwardly curved anchoring plate is the curve transition segment. the

Preferably, the surface of the main span portion of the upwardly curved anchoring plate is depressed downward to form a concave parabolic surface, and the upper surface of the upwardly curved anchoring plate is convexly arranged to form a convex parabolic surface and is connected to the pier The horizontal section of the pier top is connected, and the lower part of the anchor plate is integrated with the bottom plate arranged in the horizontal section of the construction section of the mid-span closing section. the

Preferably, the upwardly curved anchor plate or the horizontal anchor plate extends to the last sawtooth block on the side of the bridge pier and is arranged horizontally and extends to the bridge pier and passes through the diaphragm on the top of the pier and all the adjacent spans. The above-mentioned upward-bending anchor plate or the horizontal anchor plate are connected as a whole. the

Preferably, the upward-curved anchor plate and the horizontal anchor plate terminate at the last sawtooth block near the pier side, and a safety guardrail is provided at the rear ends of the upper-bent anchor plate and the horizontal anchor plate. the

Preferably, the transverse structural steel bars of the upwardly bent anchor plate and the horizontal anchor plate are bent at the web and welded firmly with the vertical steel bar of the web. the

Preferably, transverse reinforcing ribs are provided on the upturned anchor plate and the horizontal anchor plate of the L/2 section to 3L/8 section section of the box girder mid-span. the

Preferably, the transverse reinforcing ribs are provided with transverse prestressed cables, and the transverse prestressed cables are stretched on the two outer surfaces of the box body, or one end of the transverse prestressed cables is anchored in the web, The other end is bent to tension in the box. the

A prestressed concrete variable cross-section box bridge provided by the utility model includes pier, bottom plate, web plate, prestressed bottom plate cable, horizontal anchor plate and upward curved anchor plate, and the bottom plate at the mid-span position of the box girder corresponds to the girder height position Set the horizontal anchor plate; above the horizontal anchor plate, install an upward-sloping upward-curved anchor plate along the longitudinal direction of the box girder; The upper curved anchor plate is separated from the horizontal anchor plate and the bottom plate at other positions; the thickness of the upward curved anchor plate and the horizontal anchor plate is consistent with the thickness of the mid-span part of the bottom plate; the prestressed bottom cable is arranged in two layers, one of which is prestressed The upper bend of the floor cable is arranged inside the upper bend anchor plate, and another layer of prestressed floor cables is arranged horizontally inside the horizontal anchor plate; both the upper bend anchor plate and the horizontal anchor plate are provided with serrations at the anchorage position of the prestressed floor cable The tensioned anchor end of the prestressed floor cable is bent into the box at the saw-toothed block, and is tensioned and anchored symmetrically on the saw-toothed block along the longitudinal direction of the box girder. the

In this way, the double-layer arrangement of prestressed floor cables provides a reasonable location and anchoring position for the floor cables. The double-layer arrangement provides a reasonable laying and anchoring position for the positive moment cables, reduces the hollowing rate of the floor section and the flat bending amplitude of the prestressed floor cables, and the upwardly bent prestressed floor cables provide upward radial component force, which can offset In the second phase, the dead load and partial vehicle load force have improved the carrying capacity. the

Description of drawings

Fig. 1 is a structural schematic diagram of a large-span prestressed concrete variable-section box bridge with floor cables bent down in the prior art;

Figure 1-1 is a structural schematic diagram of the A-A section of the bridge shown in Figure 1;

Figure 1-2 is a structural schematic diagram of the B-B section of the bridge shown in Figure 1;

Fig. 2 is a structural schematic diagram of the longitudinal arrangement of steel cables of a large-span prestressed concrete variable-section box bridge with floor cables bent down in the prior art;

Figure 2-1 is a structural schematic diagram of the A-A sectional plane of the bridge shown in Figure 2;

Figure 2-2 is a structural schematic diagram of the B-B cross-section of the bridge shown in Figure 2;

Fig. 3 is a structural schematic diagram of a large-span prestressed concrete variable-section box bridge with floor cables arranged horizontally in the prior art;

Figure 3-1 is a structural schematic diagram of the A-A sectional plane of the bridge shown in Figure 3;

Figure 3-2 is a structural schematic diagram of the bridge B-B section shown in Figure 3;

Fig. 4 is a structural schematic diagram of the longitudinal layout of steel cables of a large-span prestressed concrete variable-section box bridge with floor cables arranged horizontally in the prior art;

Figure 4-1 is a structural schematic diagram of the A-A sectional plane of the bridge shown in Figure 4;

Figure 4-2 is a structural schematic diagram of the B-B cross-section of the bridge shown in Figure 4;

Fig. 5 is the structural representation of the prestressed concrete variable section box bridge in a kind of embodiment provided by the utility model;

Figure 5-1 is a structural schematic diagram of the A-A sectional plane of the bridge shown in Figure 5;

Figure 5-2 is a structural schematic diagram of the B-B cross-section of the bridge shown in Figure 5;

Fig. 6 is a structural schematic diagram of the longitudinal arrangement of the steel cables of the prestressed concrete variable-section box bridge in a specific embodiment provided by the utility model;

Figure 6-1 is a structural schematic diagram of the A-A section of the bridge shown in Figure 6;

Figure 6-2 is a structural schematic diagram of the B-B section of the bridge shown in Figure 6;

Among them: in Figure 1-Figure 2-2:

Bottom plate 01, web plate 02, sawtooth block 03, bottom plate cable 05, pier 06, diaphragm 07;

In Figure 3-Figure 4-2:

Bottom plate 11, web plate 12, sawtooth block 13, horizontal anchor plate 14, bottom plate cable 15, pier 16, diaphragm 17;

In Figure 5-Figure 6-2:

Bottom plate 1, web plate 2, sawtooth block 3, upward-curved anchor plate 4, horizontal anchor plate 41, bottom plate cable 5, pier 6, and transverse diaphragm 7. the

Detailed ways

The core of the utility model is to provide a prestressed concrete variable cross-section box bridge, which can reduce the hollowing rate of the bottom plate section and the flat bending amplitude of the bottom plate cable, can offset the force of the second-stage dead load and part of the vehicle load, and improve the carrying capacity . the

In order to enable those skilled in the art to better understand the solution of the utility model, the utility model will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. the

Please refer to Fig. 5 to Fig. 6-2, Fig. 5 is a structural schematic diagram of a prestressed concrete variable section box bridge in a specific embodiment provided by the utility model; Fig. 5-1 is an A-A sectional view of the bridge shown in Fig. 5 Fig. 5-2 is the structural schematic diagram of the B-B sectional plane of the bridge shown in Fig. 5; Fig. 6 is the longitudinal arrangement of steel cables of the prestressed concrete variable cross-section box bridge in a specific embodiment provided by the utility model Schematic diagram of the structure; Figure 6-1 is a schematic structural diagram of the A-A section of the bridge shown in Figure 6; Figure 6-2 is a schematic structural diagram of the B-B section of the bridge shown in Figure 6. the

The prestressed concrete variable cross-section box bridge provided by the utility model includes pier 6, bottom plate 1, web plate 2, prestressed bottom plate cable 5, horizontal anchor plate 41 and upward curved anchor plate 4. A horizontal anchor plate 41 is installed at a part of the corresponding beam height; above the horizontal anchor plate 41, an upwardly bent anchor plate 4 is installed along the longitudinal direction of the box girder; in the mid-span L/2 section to 3L/8 section section, the upward curved anchor Plate 4, horizontal anchor plate 41 and base plate 1 are integrated, the thickness of this section is 40-60cm, and the rest of the upward bending anchor plate 4 is separated from horizontal anchor plate 41 and base plate 1, and the thickness of this section is 30 cm. -50cm. the

As shown in Figures 6 to 6-2, the prestressed floor cables 5 are arranged in two layers, one layer of prestressed floor cables 5 is arranged in an upward bend inside the upwardly bent anchor plate 4, and the other layer of prestressed floor cables 5 is arranged horizontally The inside of the anchor plate 41; at the 5-tensioned anchor position of the prestressed floor cable, the upwardly bent anchor plate 4 and the horizontal anchor plate 41 are both provided with sawtooth blocks 3, and the 5 tensioned anchor ends of the prestressed floor cables are bent at the sawtooth block 3 into the box, and after the box girder is closed, it is tensioned and anchored on the sawtooth block 3 symmetrically along the longitudinal direction of the box girder. the

It should be noted that the sawtooth block 3 is arranged at the junction of the upwardly bent anchor plate 4 and the web 2 . the

The upward curved anchor plate 4 is arranged horizontally in the construction section near the mid-span closing section, and is arranged upwardly to form an oblique straight line or curve according to a certain slope rate. The transition section between the mid-span horizontal section and the inclined section of the upward curved anchor plate is a curved line Transition. the

It should be noted that, in this specific embodiment, the slope rate of the upward slope of the upward bending anchor plate 4 is 5%, because the slope rate is based on the upward component force of the prestressed floor cable 5 set according to the bridge upward bending, which can balance the second phase dead load and The load effect of the lane is determined, and the slope ratio is different according to different bridges, so it is not ruled out to use other slope ratios to set the upward bending anchor plate. the

In addition, the surface of the main span part of the upward-curved anchor plate 4 is concave downwards to form a concave parabolic surface, and the upper surface of the upward-curved anchor plate 4 is convexly arranged to form a convex parabolic surface and is aligned with the horizontal section of the pier top of the pier 6. Connected, the lower part of the anchor plate 4 is integrated with the bottom plate 1 arranged in the horizontal section of the construction section of the mid-span closing section. the

It should be noted that the whole part of the anchor plate 4 is arranged in a parabolic shape, wherein the two ends of the parabola of the anchor plate 4 are connected to the horizontal end of the pier top of the pier 6, and the surface of the connecting section between the anchor plate 4 and the pier 6 A convex parabolic surface set for an upward bulge. the

As shown in Figure 5, the upward-curved anchor plate 4 (or horizontal anchor plate 41) can be arranged horizontally near the last sawtooth block 3 on the side of the bridge pier 6 and extend to the bridge pier 6 and pass through the pier top diaphragm 7 and adjacent spans. The upper bent anchor plate 4 (or horizontal anchor plate 41) is connected as a whole. A curved transition section is set between the horizontal section of the pier top of the upwardly curved anchor plate 4 and the inclined section of the bridge span. The upward-curved anchor plate 4 (or horizontal anchor plate 41) can also terminate at the last sawtooth block 3 near the pier 6 side and a safety guardrail is provided at the rear end of the upward-curved anchor plate 4 (or horizontal anchor plate 41). the

The prestressed floor cable 5 is generally flat-bent in the plane to the junction of the web 2 and the bottom plate 1 in the box for tensioning and anchoring operations. As shown in Figure 6-1, the left and right sides of the upwardly bent anchor plate 4 and the horizontal anchor plate 41 are integrated with the web 2 along the longitudinal direction of the bridge, and the transverse structural reinforcement is bent at the web 2 and vertical to the web 2. Weld firmly to the steel bar or overlap. When lap joint is used, the horizontal structural steel bars of the upwardly bent anchor plate 4 and the horizontal anchor plate 41 are bent at the web (2), and the anchorage length in the web is guaranteed to be the diameter of the steel bar. more than 40 times. the

It should be noted that, in this specific embodiment, both the upward-curved anchor plate 4 and the horizontal anchor plate 41 are firmly overlapped with the web 2 through steel bars. Of course, other settings are not excluded, such as only the upward-curved anchor plate 4 The transverse structural steel bar of the web is bent at the web 2 and welded firmly with the vertical structural steel bar of the web 2. the

The radial force in the horizontal plane of the mid-span L/2 section to the 3L/8 section section is relatively large, and the transverse splitting force caused by the large longitudinal resultant force of the floor cable 5 is large, so the anchor plate 4 and the horizontal anchor plate 41 are bent upward in this section. The horizontal structural steel bars of the horizontal structure should be specially strengthened. If necessary, horizontal reinforcement ribs are set on the upward bending anchor plate 4 and the horizontal anchor plate 41, and lateral prestress is applied to the horizontal reinforcement ribs at the same time. It is possible to avoid longitudinal cracking by setting transverse prestressed cables and using transverse prestressed cables to provide the required transverse prestress. the

The transverse prestressed ribs are provided with transverse prestressed cables to be stretched at both ends of the outer surface of the box, or one end is anchored in the concrete at the web 2, and the other end is bent into the box for tension. the

It should be noted that both the upward-curved anchor plate 4 and the horizontal anchor plate 41 are provided with reinforcing ribs and transverse prestressed cables. Of course, it is not ruled out that only one of the anchor plates is provided with reinforcing ribs and transverse prestressed cables as required. the

It should also be noted that the transverse prestressing construction on the transverse stiffeners is earlier than the tensioning construction of the longitudinal floor cables. the

The setting method of the prestressed concrete variable-section box bridge in this specific embodiment has been introduced in detail above, so setting can achieve the following effects:

(1) The double-layer arrangement of the prestressed floor cables 5 provides a reasonable laying position and a reasonable anchorage position for the prestressed floor cables 5. Layer layout reduces the flat bending amplitude of the prestressed floor cables 5 and the horizontal tension caused by flat bending, reduces the hollowing rate of the center horizontal section of the prestressed floor cables 5 in each layer, and improves the structure to avoid the cracking of the floor 1. Reasonable anchoring The position avoids the longitudinal negative effect caused by the excessive deviation from the bending moment envelope diagram in the L/4 section to the L/8 section. the

(2) Since the upward-curved anchor plate 4 is installed, and the prestressed floor cables 5 are arranged in the upward-curved anchor plate 4, the prestressed floor cables 5 in the middle span of the bridge are arranged upwardly, and roads are arranged on various longitudinal slopes. On the other hand, by setting different up-slope ratios, the downward radial force at the mid-span of bridges in the prior art can be eliminated or reduced, and the downward radial force of positive moment cables at the mid-span of long-span variable-section box bridges can be solved The continuous increase of the span can avoid problems caused by the downward radial force, such as longitudinal cracks in the mid-span of girder bridges, deflection in the mid-span, and main tensile stress cracks in the web, which are likely to occur in the web. Improve the carrying capacity of long-span bridges. the

(3) Since the prestressed floor cable 5 arranged in the upward bending anchor plate 4 can provide an upward radial force, the upward radial force can balance the secondary dead load and the lane load, and can improve the shrinkage of concrete. Overcoming the continuous downward deflection of the mid-span of the bridge during the operation period will improve the carrying capacity of the long-span bridge and reduce the difficulty of construction control. Of course, the prestressed floor cables 5 can provide part of the shear component force through the upward bending arrangement, and can also improve the shear resistance capacity of the bridge. the

(4) The facade of the prestressed floor cable 5 placed inside the upwardly bent anchor plate 4 can be formed into a concave parabolic facade, so that the prestressed floor cable 5 can match the bending moment envelope diagram of the bridge, Furthermore, it can overcome the large positive bending moment generated by the L/2 section to the 3L/8 section in the mid-span, and at the same time, it can resist part of the negative bending moment near the L/8 section, so that the bridge can be reasonably stressed. the

(5) The transverse prestressing construction on the transverse reinforcing rib is earlier than the tensioning construction of the longitudinal prestressing floor cable 5, which can ensure that the floor 1 will not produce longitudinal cracking. the

It should be noted that the prestressed concrete variable cross-section box bridge and its construction method provided in this specific embodiment are suitable for narrow bridges (2 to 3 lanes) with a main span of 100 to 150 meters on a longitudinal slope. Of course, It also does not exclude the use of the girder bridge and the construction method in this specific embodiment when designing other forms of girder bridges. the

A prestressed concrete variable cross-section box bridge provided by the utility model has been introduced in detail above. In this paper, specific examples are used to illustrate the principle and implementation of the present utility model, and the descriptions of the above embodiments are only used to help understand the method and core idea of the present utility model. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the utility model, some improvements and modifications can also be made to the utility model, and these improvements and modifications also fall into the protection of the claims of the utility model. within range. the

Claims (8)

1. a prestress concrete variable cross-section box bridge comprises bridge pier (6), base plate (1), web (2), prestress baseboard rope (5), it is characterized in that: described base plate (1) the respective beam high position in the span centre position arranges horizontal anchor plate (41); Described horizontal anchor plate (41) top, the direction from span centre to described bridge pier (6) vertically arranges curved anchor plate (4) along the case beam; To 3L/8 cross section section, described curved anchor plate (4), described horizontal anchor plate (41) and the described base plate (1) combines together at span centre, and separate all the other positions; The thickness of described curved anchor plate (4) and the thickness of described horizontal anchor plate (41) all the span centre thickness partly with described base plate (1) are identical; Described prestress baseboard rope (5) is double-deck to be arranged, wherein the described prestress baseboard rope of one deck (5) is gone up curved described curved anchor plate (4) inside of that is arranged in, and the described prestress baseboard rope of another layer (5) horizontal arrangement is in the inside of described horizontal anchor plate (41); Described horizontal anchor plate (41) and the described anchor plate (4) of upward bending are provided with sawtooth fast (3), and described prestress baseboard rope (5) is pressed vertical symmetrical stretch-draw anchor in described horizontal anchor plate (41) or described junction of bending anchor plate (4) and described web (2) by described sawtooth piece (3).

2. prestress concrete variable cross-section box bridge according to claim 1, it is characterized in that: near described curved anchor plate (4) the sections horizontal arrangement of the span centre closure segment, constructing that, and be inclined upwardly and be arranged to skew lines or curve, described span centre horizontal segment and the changeover portion between tilting section of curved anchor plate (4) is curve transition.

3. prestress concrete variable cross-section box bridge according to claim 1, it is characterized in that, described surface of the main span part of curved anchor plate (4) is the spill parabolic surface to lower recess, the upper face of described anchor plate (4) raises up to arrange and is the convex parabolic surface and links to each other with the pier top horizontal segment of described bridge pier (6), described anchor plate (4) bottom be arranged at the construct described base plate (1) of horizontal segment of sections of span centre closure segment and combine together.

4. prestress concrete variable cross-section box bridge according to claim 3, it is characterized in that described curved anchor plate (4) or the described horizontal anchor plate (41) extends to last described sawtooth piece (3) horizontal arrangement of described bridge pier (6) side and extend to described bridge pier (6) and locate and pass pier top diaphragm (7) and curved anchor plate (4) or described horizontal anchor plate (41) is connected as a single entity with adjacent stride described.

5. prestress concrete variable cross-section box bridge according to claim 4, it is characterized in that described curved anchor plate (4) and described horizontal anchor plate (41) are in locating termination near last described sawtooth piece (3) of described bridge pier (6) side and at the curved plate (4) admittedly of described anchor and described horizontal anchor plate (41) rear end safety barrier being set.

6. according to arbitrary described prestress concrete variable cross-section box bridge of claim 1 to 5, it is characterized in that the described transverse structure reinforcing bar of curved anchor plate (4) and described horizontal anchor plate (41) is located to bend up also and the vertical reinforcement firm welding of described web (2) at described web (2).

7. prestress concrete variable cross-section box bridge according to claim 6 is characterized in that, L/2 cross section to described curved anchor plate (4) and the described horizontal anchor plate (41) of 3L/8 section arranges horizontal ribs in the case girder span.

8. prestress concrete variable cross-section box bridge according to claim 7, it is characterized in that: described horizontal ribs is provided with the transverse prestress rope, described transverse prestress rope is in two outer surface stretch-draw of casing, or an end of described transverse prestress rope is anchored in the described web (2), and the other end bends up to stretch-draw in the case.

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