JP3635004B2 - Bridge cantilever construction method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cantilever erection method for a bridge, and more specifically, when a bridge is erected, a bridge girder block of a cantilever structure is sequentially extended from the pier part to the side to extend the entire bridge girder between the piers. It is intended for construction methods.
[0002]
[Prior art]
The cantilever-type erection method is known as a method that is useful when support work cannot be performed from the ground due to the water surface under the bridge piers or roads or buildings with heavy traffic.
Since relatively short bridge girder blocks can be added one after another over the side of the pier, facilities such as large support works across the pier are unnecessary on the ground side. It is easy to apply when there is a water surface such as a river between bridge piers, roads, railroad tracks, and buildings.
[0003]
The cantilever erection method includes a method of constructing the bridge girder block on the ground and then placing it on the end of the bridge pier or bridge girder block, and a method of creating a new bridge girder block in the air at the end of the bridge pier or bridge girder block. Are known.
In addition, prestressed concrete is used as a bridge structure. Prestressed concrete is a technique for improving the proof stress during use by applying stress in the direction opposite to the load applied during use to the concrete before or after placing the concrete. Since concrete is a material property that is strong in compressive force and weak in tensile force, if prestress is applied to the part of the concrete structure where the tensile load is applied, the compressive strength of the concrete structure is greatly improved. be able to. If such prestress is applied to the bridge piers and bridge girder blocks constituting the bridge, a bridge that is extremely strong against the load applied during construction and during use can be constructed.
[0004]
In order to give prestress to the bridge girder block, for example, when building the girder block on the ground, PC (prestress concrete) steel material is embedded in the concrete, and prestress is applied to the PC steel material. In the case of a method for constructing a bridge girder block in the air, PC steel material insertion or prestress introduction work is performed during the construction work of the bridge girder block.
[0005]
[Problems to be solved by the invention]
Of the conventional cantilever erection methods, the method of building the bridge girder block on the ground requires a work space for building the bridge girder block on the ground. Further, it takes a large amount of equipment and work time to lift a heavy bridge girder block to the sky and install it in a predetermined place. For example, a crane device that suspends a bridge girder block is very large. Furthermore, it is troublesome to connect and fix a new bridge girder block to an existing bridge pier or bridge girder block. In a state where the bridge girder block constructed on the ground is lifted up to a predetermined place, it is difficult to connect the bridge girder block by tensioning with PC steel because it is a high place. If the place where the bridge girder block is manufactured and the construction site are separated from each other, it will take time to carry the heavy girder block. Therefore, there were many problems in terms of construction and economy.
[0006]
The method of constructing a new bridge girder block at the end of a bridge pier or bridge girder block has the advantage that no large equipment or work space is required on the ground. However, support for placing a formwork to construct a new bridge girder block, constructing a framework with reinforcing bars and steel frames in the interior space of the formwork, and placing concrete inside the formwork The structure must be temporarily installed in the air at the end of the existing pier or bridge girder block. A support structure that can hold the entire weight of the concrete and the framework and the formwork becomes very large. Constructing such a large support structure in the air requires a lot of labor, work time, and equipment cost.
[0007]
An object of the present invention is to improve a conventional cantilever erection method of a bridge, and to provide a method of performing a construction work on a bridge pier easily and efficiently and obtaining a bridge excellent in strength. .
[0008]
[Means for Solving the Problems]
The bridge cantilever erection method according to the present invention is a method of erection a bridge by sequentially adding bridge girder blocks to a pier in a cantilever structure, and the following steps (a) to (d) are repeated.
Step (a): A steel truss frame composed of a hollow steel pipe, part of which is inserted through a PC steel material, is connected to and supported by the end of an installed pier or bridge girder block.
Step (b): A concrete frame for casting is installed around the steel truss frame, supported by the steel truss frame.
[0009]
Step (c): Concrete is placed in the concrete casting form, and a bridge girder block made of concrete in which a steel truss frame is embedded is constructed.
Step (d): PC steel material is inserted into the hollow steel pipe of the steel truss frame, and prestress is introduced into the concrete of the bridge girder block.
[Bridge]
Applicable to various ordinary bridges. There are no particular limitations on the purpose or form of use of the bridge, such as road bridges, railway bridges, pedestrian bridges, and aqueducts.
In order to install support works on the ground of the construction site, such as construction on the surface of rivers, lakes, seas, etc., and construction across bridges, roads, railways, building structures, and valleys, etc. It is suitable when it is difficult to secure a large occupied space.
[0010]
It is also suitable for relatively small bridges where it is difficult to place a heavy object such as an excessive installation device or structural material on the pier or bridge girder.
The basic structure of the bridge is a girder bridge in which a bridge girder is installed between bridge piers, but other structures such as a suspension bridge and an arch bridge can be combined.
The overall structure of the bridge girder may be the same as a normal bridge. For example, the upper surface side on which roads and railways are arranged is often flat. The bottom side is often curved in an upward direction from the side closer to the pier to the side farther away. In some cases, both the upper surface side and the lower surface side are curved upward.
[0011]
The cross-sectional structure of the bridge girder is preferably one that can exhibit sufficient strength and proof stress, is light in weight, and uses less material. For example, it is possible to employ one having a generally rectangular shape as a whole and having a circular or box-shaped hollow portion in the center. A double T-shaped cross section in which two T-characters are arranged horizontally can also be adopted.
[Piers]
It is a structure for supporting a bridge on the ground, and has a structure such as concrete, reinforced concrete, steel concrete, etc., as in a normal bridge.
A bridge is constructed by connecting a plurality of bridge girder blocks between so-called spans between piers. Both ends of the bridge are connected to the abutment installed on the ground. Bridge girder blocks are also installed between the pier and the abutment. In this specification, unless otherwise specified, the pier means a technical concept in which a narrow pier and an abutment are combined.
[0012]
The distance between piers in a bridge, so-called span distance, varies depending on the construction conditions, but can usually be set in the range of 40 to 70 m.
[Bridge girder block]
The bridge girder part is divided into a plurality of blocks according to the structure and form of the bridge. When a bridge girder block is connected to form a bridge girder, the bridge girder block needs to have strength or proof strength that supports its own weight and the weight of a structure built on the upper part.
The size of one bridge girder block varies depending on the scale and overall length of the bridge, but is usually set in a range of 3 to 5 m in length, 3 to 6 m in width, and 0.7 to 3 m in height.
[0013]
The basic structure of the bridge girder block is composed of a steel truss frame and concrete covering the outer periphery of the steel truss frame.
The bridge girder block can be provided with a space and a shape in which various pipes such as a power source and a communication line, a balustrade, an illumination lamp, and other equipment structures are arranged.
[Steel truss frame]
It forms the basic structure of the bridge girder block and plays the role of supporting the weight of the concrete and reinforcing the concrete with mechanical strength and rigidity.
Made of steel. Steel materials include ordinary truss structures such as round, square or irregular shaped steel bars, shaped steel materials such as L, H, I and T, hollow steel tubes of cylinders and square tubes, steel plates, etc. Similar steel materials can be used. The hollow steel pipe has a narrowness ratio smaller than that of the shape steel material, and is suitable for a truss member to which an axial load is mainly applied. In addition, the adherence of concrete to the steel material is excellent in hollow steel pipes, particularly round steel pipes. By providing irregularities such as protrusions on the outer periphery of the steel material, the binding force with the concrete can be increased. Steel wires and cables can be combined.
[0014]
The truss structure is a combination of linear members that form a triangle, so that the axial load acts on each member to improve overall rigidity, deformation resistance, and mechanical strength. It is a civil engineering structure.
The steel truss frame only needs to have the basic characteristics of the truss structure as described above, and may include a portion that is not part of the truss structure.
In order to construct a steel truss frame, the steel materials described above may be joined by means such as flange connection, bolt connection, welding, riveting, and adhesion.
(Hollow steel pipe)
A part of the steel truss frame is constituted by a hollow steel pipe through which the PC steel material is inserted.
[0015]
The hollow steel pipe can be made of the same material as the normal truss structure described above. Therefore, a hollow steel pipe having at least mechanical strength and proof strength that can constitute a truss structure is used. Further, a part of the load applied to the steel truss frame can be borne by the hollow steel pipe.
The inner diameter of the hollow steel pipe is set so that the PC steel material can be inserted. The applicable dimensions of the hollow steel pipe vary depending on the outer diameter and type of the PC steel used.
In order to introduce prestress into a concrete structure using PC steel, it is necessary to arrange the PC steel so as to penetrate from one end of the concrete structure to the other. Therefore, the hollow steel pipe for PC steel material insertion provided in the steel truss frame is arranged from one end to the other end of the steel truss frame or bridge girder block so that a space penetrating the inside from end to end is formed. Keep it.
[0016]
Of the bridge girder block, a hollow steel pipe in a direction in which prestress is introduced may be used for insertion of the PC steel material. Normally, a hollow steel pipe for inserting a PC steel material is arranged in the span direction of the bridge girder block. However, a hollow steel pipe for inserting a PC steel material can be arranged along the width direction or the vertical direction of the bridge girder block.
A plurality of hollow steel pipes for inserting a PC steel material can be provided on a steel truss frame. If a plurality of PC steel material hollow steel pipes are arranged at intervals in parallel with the prestress introduction direction, a large prestress can be introduced evenly throughout.
[0017]
[PC steel]
As the PC (prestress concrete) steel material, the same PC steel material as that used for manufacturing a normal prestressed concrete structure can be used.
As the PC steel material, a round bar or wire cable is used.
PC steel having a size that can be inserted into a hollow steel pipe of a steel truss frame is used.
[Process (a): Construction of steel truss frame]
The steel truss frame of the bridge girder block to be newly constructed is connected and supported at the end of the bridge pier or bridge girder block that has already been installed.
[0018]
The steel truss frame can be carried in the upper part of an existing bridge pier or bridge girder block in an assembled state, suspended from the end of the existing bridge pier or bridge girder block, and placed at a predetermined position.
If the steel truss frame exposed at the end of an existing bridge pier or bridge girder block and the newly placed steel truss frame are connected by means such as bolt fastening or welding, the newly placed steel truss The frame is supported by existing piers or girder blocks.
The material can be carried to the upper part of an existing pier or bridge girder in a state of a partial structure in which individual members or a part of members constituting the steel truss frame are assembled. In this case, a special transport device or a large crane device is unnecessary. At the end of an existing bridge pier or bridge girder block, individual members or partial structures can be connected to assemble a steel truss frame and simultaneously supported by the existing steel truss frame. In this case, a simple work scaffolding for assembling and connecting the steel truss frame can be temporarily set over the end face of the existing bridge pier or bridge girder block.
[0019]
Among the steel truss frames installed in this way, the hollow steel pipes through which the PC steel material is inserted are connected in a state of communicating with the hollow steel pipes for inserting the PC steel material in the existing steel truss frame.
A support member for supporting the formwork for placing concrete can be attached to the steel truss frame.
[Step (b): Arrangement of formwork]
Form a concrete casting form around the steel truss frame.
The formwork can be supported on the steel truss frame via bolts, spacer members, wires, and the like. A part of the formwork may be supported on the end of an existing bridge pier or bridge girder block. The formwork support for the piers and bridge girder blocks should be strong enough to support the weight of the concrete when the concrete is placed inside the formwork.
[0020]
The formwork may be capable of covering the entire steel truss frame and placing concrete on the entire bridge girder block, or dividing the bridge girder block into multiple parts and installing a formwork for each divided part. it can.
Of the steel truss frame, the end of the hollow steel pipe into which the PC steel material is inserted is preferably plugged or welded to the inner surface of the mold so that the concrete does not flow.
[Process (c): Placing concrete]
When concrete is placed in the interior space of the formwork, a bridge girder block in which the steel truss frame is covered with concrete is formed.
[0021]
The concrete to be cast can be transported from above-ground concrete manufacturing equipment and transport equipment to the upper part of the bridge pier or bridge girder block via a hose and piping and injected into the formwork. Containers containing concrete can be lifted with a crane or the like and carried to the upper part of a pier or bridge girder block.
Once the cast concrete is hardened, the formwork is removed. When removing the formwork, a support structure such as a separator supporting the formwork on the steel truss frame can also be removed. The support structure can be left embedded in the concrete. After removing the support structure, it can also be filled with concrete.
[0022]
[Step (d): Prestress introduction]
The PC steel material is inserted through the hollow steel pipe of the steel truss frame embedded in the concrete.
The position where the PC steel material is inserted may be any position as long as it needs to be strengthened by introducing prestress to the concrete of the bridge girder block.
In the case of a bridge girder block of a general bridge, since a large tensile force tends to be applied to the upper side, it is preferable to introduce a prestress by inserting a PC steel material into a hollow steel pipe disposed on the upper side.
[0023]
The prestress introduction device and introduction work may be the same as those of a normal prestress structure. Usually, both ends of the PC steel material arranged at both ends of the bridge girder block are supported by the fixing device, and a tensile force is applied to the PC steel material from the fixing device, so that prestress in the compression direction is introduced into the concrete around the PC steel material. The
Prestress can be introduced only in newly constructed bridge girder blocks, but prestress can be introduced in both existing bridge girder blocks and new bridge girder blocks. In this case, the PC steel material is inserted into a hollow steel pipe communicating with both bridge girder blocks, and a fixing device is attached to the PC steel material at both ends of the plurality of bridge girder blocks to introduce prestress.
[0024]
Since the pre-stressed PC steel remains embedded in the bridge girder block, the hollow steel pipe used for pre-stress introduction through the PC steel is then introduced into the newly connected bridge girder block. Can not be used.
Therefore, when prestress is introduced over a plurality of existing and newly installed girder blocks, a hollow steel pipe for inserting a PC steel material that is not used for prestress introduction must remain in the existing girder block. Therefore, it is preferable to provide a plurality of sets of hollow steel pipes for PC steel material insertion in the bridge girder block in accordance with the number of steps for introducing prestress in the entire bridge. If it does so, whenever a new bridge girder block is connected, a pre-stress can be introduced by inserting a PC steel material into a new set of hollow steel pipes that have not been used so far.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
1 to 9 show stepwise embodiments of a bridge cantilever erection method.
FIG. 9 shows the overall structure of the completed bridge. The spans of the bridge piers 10, 10 erected on the ground at regular intervals are connected by a bridge girder, and the bridge girder is sequentially arranged on the side of the pier block 12 and the pier block 12 arranged on the upper part of the pier 10. A plurality of bridge girder blocks 14 to 18 are combined.
[Construction of pier block]
As shown in FIG. 1, the bridge erection starts from the construction stage of the pier 10 and the pier block 12.
[0026]
The columnar pier 10 is entirely made of concrete, and a frame member made of a steel material such as a reinforcing bar is embedded therein as needed. A bridge pier block 12 projecting left and right from the upper part of the pier 10 is constructed. The pier block 12 is entirely made of concrete, and a steel truss frame 20a configured by combining steel pipes and shaped steel materials is embedded therein. Although not shown, the steel truss frame 20a of the pier block 12 and the frame member inside the pier 10 are also connected.
The steel truss frame 20 a includes an upper chord member 22 disposed along the upper surface of the pier block 12, a lower chord member 24 disposed along the lower surface of the pier block 12, and a vertical member that connects the upper chord member 22 and the lower chord member 24. 26, and an oblique member 28 that obliquely connects the intersections of the upper chord member 22, the lower chord member 24, and the vertical member 26 to constitute a truss structure in terms of structural mechanics. As shown in FIG. 10A, in the width direction of the pier block 12, truss structures in the vertical plane composed of the upper chord member 22, the lower chord member 24, the vertical member 26, and the diagonal member 28 are arranged in a plurality of rows. These are connected to each other by a horizontal chord member 29 and a diagonal member (not shown), and a truss structure is also formed in a horizontal plane.
[0027]
Among the members constituting the steel truss frame 20a, the upper chord member 22, the lower chord member 24, and the vertical member 26 are hollow steel pipes. In the upper chord member 22 and the lower chord member 24, there is a space penetrating the both end surfaces of the pier block 12. The diagonal member 28 is a steel bar or a shaped steel.
The pier block 12 is constructed by constructing a steel truss frame 20a on the upper part of the pier 10 and then placing a concrete frame around the steel truss frame 20a and placing concrete in the interior space of the mold frame. To cast. After the formwork is removed, the pier block 12 made of concrete in which the steel truss frame 20a is embedded is formed.
[0028]
[Construction of bridge girder block: Steel truss frame]
As shown in FIG. 2, steel truss frames 20 b for constructing the bridge girder block 14 are respectively constructed on both end faces of the pier block 12.
The basic members and structure of the steel truss frame 20b are the same as the steel truss frame 20a of the pier block 12 described above. Specifically, an oblique member 28 made of a steel bar or a shaped steel member is disposed on an upper chord member 22, a lower chord member 24, and a vertical member 26 made of a hollow steel pipe.
The upper chord member 22 and the lower chord member 24 of the steel truss frame 20b are connected to the upper chord member 22 and the lower chord member 24 of the pier block 12, and the internal space is in communication therewith. The steel truss frame 20b is supported in a cantilevered state with respect to the steel truss frame 20a of the pier block 12.
[0029]
The steel truss frame 20b may be connected to the steel truss frame 20a of the bridge pier block 12 by lifting up the pre-assembled steel truss frame 20b to the end face position of the pier block 12, or constituting the steel truss frame 20b. In the state of a partial structure in which individual members or a plurality of members are assembled, they can be carried from the ground to the upper part of the pier block 12 and assembled while being connected to the steel truss frame 20a of the pier block 12.
In FIG. 2, the erection vehicle 30 is arranged on the upper part of the pier block 12. The erection vehicle 30 is movable on the upper surface of the pier block 12 and is provided with suspension devices 32 at both ends. The members and partial structures constituting the steel truss frame 20b are suspended, and the end surface of the pier block 12 is suspended. Each member can be arranged at a predetermined position.
[0030]
[Construction of bridge girder block: concrete placement]
As shown in FIG. 3, after the steel truss frame 20b is supported at both ends of the pier block 12, a formwork 40 for concrete placement is constructed so as to surround the outer periphery of the steel truss frame 20b.
The mold 40 is configured using a normal mold material made of wood, synthetic resin, or metal. Usually, a necessary formwork surface can be configured by arranging steel plate forms formed in a panel shape having a predetermined shape such as a rectangle and a predetermined size. The steel plate formwork is suitable for being removed and reused repeatedly after placing concrete. The mold 40 is supported by the steel truss frame 20b or the pier block 12. Specifically, the formwork panel may be attached to the steel truss frame 20b via a separator, a spacing member, a bolt, or the like. The above-described erection vehicle 30 can also be used when the mold 40 is disposed.
[0031]
For example, as shown in FIG. 10, in the cross-section in the width direction of the bridge girder blocks 12 to 18, when the hollow portion 19 is provided or the concavo-convex structure is provided, the arrangement structure of the mold frame 40 is set in accordance with the shape. Will be set.
Concrete is injected into the constructed mold 40 using a concrete injection pipe 42 or the like. The above-described construction vehicle 30 can be provided with a concrete injection pipe 42, a concrete storage tank, and the like. A concrete transport pipe can also be laid from the ground via the pier 10 and the pier block 12.
When the concrete poured into the mold 40 is cured, the mold 40 is removed.
[0032]
[Construction of bridge girder block: Pre-stress introduction]
As shown in FIG. 4, bridge girder blocks 14 and 14 are constructed on both sides of the pier block 12. The steel truss frame 20b is embedded in the bridge girder block 14 made of concrete. However, in FIG. 4, in order to make the drawing easier to understand, the vertical members 26 and the diagonal members 28 of the steel truss frames 20 a and 20 b are omitted from illustration, and the upper chord member 22, the lower chord member 24, Is mainly shown.
Prestress is introduced into the concrete by using the upper chord member 22 made of a hollow steel pipe disposed over both end faces of the bridge pier block 12 and the bridge girder blocks 14 and 14 on both sides.
[0033]
The apparatus and work method used for introducing prestress are basically performed in the same manner as the construction of a normal prestressed concrete structure.
A highly rigid PC steel material 50 is inserted into the upper chord member 22, and fixing devices 60, 60 are attached to both ends.
As shown in FIG. 5, a plurality of PC steel members 50 are inserted into the upper chord member 22. In the fixing device 60, a plurality of PC steel materials 50 are simultaneously tensioned and fixed.
The fixing device 60 includes a male cone 62 that becomes a wedge, a female cone 64 that receives a wedge, and a pressure plate 66. A bearing plate 66 is disposed on the concrete end face of the bridge girder block 14, and a plurality of PCs are provided on the circumference between the female cone 64 disposed in the center of the bearing plate 66 and the male cone 62 disposed in the center. A steel material 50 is disposed.
[0034]
After pulling a plurality of PC steel members 50 extending out of the male cone 62 in the direction of the white arrow in FIG. 5A using a dedicated tension jack (not shown), the male cone 62 is driven into the female cone 64. For example, the PC steel material 50 remains sandwiched between the female cone 64 and the male cone 62 and is fixed.
The tension force applied to the PC steel material 50 is transmitted to the concrete structure of the bridge girder block 14 via the support plate 66, and prestress is introduced into the concrete.
If cement milk is injected and hardened in the upper chord member 14 through which the PC steel material 50 is inserted, the integrity of the PC steel material 50 and the surrounding concrete is improved, and the strength of the bridge girder block 14 is increased. . Since the surface of the PC steel material 50 is not exposed, corrosion and deterioration can be prevented.
[0035]
The concrete in which prestress is introduced is offset by prestress when a tensile force is applied in the construction state or use state of the bridge, and the durability against the tensile force is remarkably improved. Since concrete originally has higher compressive strength than tensile strength, concrete with prestress in the compressing direction has a significantly increased load resistance.
In the overhanging method, the bridge pier block 12 and the bridge girder block 14 constituting the bridge are usually susceptible to a tensile force on the upper side of the bridge and a compressive force on the lower side. It is effective to introduce prestress in the compression direction.
[0036]
Therefore, it is preferable to insert pre-stress by inserting the PC steel material 50 into the upper chord material 22 of the bridge pier block 12 and the bridge girder block 14. However, depending on the load state on the bridge, pre-stress can be introduced by inserting the PC steel material into the lower chord material 24 as well.
As shown in FIG. 6, in the width direction of the bridge, a plurality of upper chord members 22 are arranged in parallel at intervals. The PC steel material 50 is inserted into only a part of the upper chord members 22 among the plurality of upper chord members 22 and prestress is introduced. The arrangement of the upper chord material 22 through which the PC steel material 50 is inserted is set so that uniform and sufficient prestress can be introduced into the bridge girder block 14. The upper chord material 22 through which the PC steel material 50 is not inserted can be used for prestress introduction when the next bridge girder block 16 is constructed.
[0037]
[Construction of bridge girder block: Extension of bridge girder block]
By repeating the above-described steps, the bridge girder block 14 is sequentially extended, and the bridge girder blocks 14 to 18 are constructed in the entire span of the bridge piers 10 and 10 to complete the bridge construction.
FIG. 7 shows a state in which a new steel truss frame 20 c is being constructed at the tip of the bridge girder block 14. The specific work is the same as the construction of the steel truss frame 20b in FIG.
FIG. 8 shows a pre-stress introduction process after the steel truss frame 20c and the bridge girder block 16 are constructed. When the prestress is introduced into the bridge girder block 16, the PC steel material 50 is inserted into the upper chord member 22 different from the upper chord member 22 used for introducing the prestress into the bridge girder block 14. The PC steel material 50 is inserted from the bridge girder block 16 to the bridge girder block 14, the bridge pier block 12, the bridge girder block 14 and the bridge girder block 16 on the opposite side, and fixing devices 60 are attached to both ends. If prestress is introduced in this state, prestress is introduced to the bridge girder blocks 16 and 14 and the pier block 12 in the middle.
[0038]
In FIG. 8, as the arrangement of the upper chord member 22 in the bridge girder block 16, the prestress is not introduced at the same position at the position corresponding to the upper chord member 22 into which the prestress is introduced in the bridge girder block 14. 22 is not arranged. However, in order to increase the structural strength of the steel truss frame 20c, it is possible to place the upper chord material 22 also at the above position. In this case, instead of the upper chord member 22 made of a hollow steel pipe into which the PC steel member 50 can be inserted, the upper chord member 22 made of a steel bar or a shaped steel member may be arranged.
As described above, every time the bridge girder blocks 14 and 16 are newly connected, the position of the upper chord member 22 that introduces prestress at that stage, that is, the position of the hollow steel pipe, is changed, so that the bridge girder blocks 14 and 16 are stepped. Even in the middle of construction, the strength of each bridge girder block 14 supported by the cantilever structure can be increased, and it is effectively prevented that the tip side hangs down and deforms during construction. .
[0039]
Between the bridge piers 10 and 10, the bridge girder block 14 closer to the bridge pier 10 has a greater load and is likely to be deformed, and thus a large proof stress is required. As shown in FIG. 8, the bridge girder block 14 closer to the pier 10 has a larger load than the bridge girder block 16 far from the pier 10 because the number of PC steel members 50 introduced with prestress is increased. The strength of the bridge girder block 14 can be increased.
[Cross-section structure of bridge]
The cross-sectional structure of the bridge is appropriately set according to the purpose of use of the bridge and the required strength characteristics and functions.
[0040]
For example, in FIG. 10 (a), the steel truss frame 20 forms a rectangular frame connected to the left and right, and a circular hollow portion 19 is provided at the center of each rectangular frame. As a result, the amount of materials such as concrete can be reduced, the weight of the bridge can be reduced, and the overall rigidity and deformation resistance can be fully exhibited.
As shown in FIG. 10B, if a rectangular hollow portion 19 is provided, the material used and the weight can be further reduced.
As shown in FIG. 10 (c), a bridge with a Dulve T cross section can also be constructed. In this case, the steel truss frame 20 has no horizontal chord material disposed on the lower side portion.
[0041]
【The invention's effect】
In the cantilever erection method of the present invention, construction of a steel truss frame of a bridge girder block to be newly added at the end of a bridge pier or bridge girder block previously constructed, concrete placement, introduction of prestressing All work is done, and all the materials and equipment necessary for construction can be supported with existing piers or bridge girder blocks or steel truss frames, so large facilities and support works on the ground and on the bridge girder There is no need to occupy a large space for installing.
In particular, a new steel truss frame is supported on an existing bridge girder block, and the steel truss frame is used to support the formwork and concrete until it is hardened. There is no need to build a structure. The work on the upper part of the bridge pier and bridge girder block, which is difficult to handle narrow and heavy objects, can be greatly simplified.
[0042]
Furthermore, since the hollow steel pipe constituting a part of the steel truss frame is used as a PC steel insertion member for introducing prestress, a so-called sheath structure, prestress introduction work can be performed easily and reliably. Compared with the case where a separate sheath tube is provided for introducing prestress, it is possible to save materials and simplify the work process.
[Brief description of the drawings]
FIG. 1 is a front view showing an embodiment of the present invention and showing a construction stage of a pier block
FIG. 2 is a front view showing a steel truss frame construction stage of a bridge girder block.
FIG. 3 is a front view showing a concrete placing stage of a bridge girder block.
FIG. 4 is a front view showing a pre-stress introduction stage of a bridge girder block.
FIG. 5 is an enlarged cross-sectional view (a) and a cross-sectional view along line AA of the fixing device portion (b).
FIG. 6 is a plan view of the pre-stress introduction stage.
FIG. 7 is a front view showing the next steel truss frame construction stage.
FIG. 8 is a plan view of a prestress introduction stage.
[Fig. 9] Front view of the completed bridge
[Fig. 10] Cross-sectional view of the bridge in the width direction
[Explanation of symbols]
10 Pier
12 Pier block
14-18 Bridge girder block
20, 20a-20c Steel truss frame
22 Upper chord material
24 Lower chord material
26 Vertical material
28 diagonal
30 Construction vehicle
40 formwork
50 PC steel
60 Fixing device

Claims (2)

A cantilever-type bridge construction method that repeats the following steps (a) to (d) in which a bridge girder block is sequentially added to a bridge pier with a cantilever structure.
A step (a) of connecting and supporting a steel truss frame composed of a hollow steel pipe, a part of which is inserted through a PC steel material, at the end of an installed pier or bridge girder block.
A step (b) of installing a formwork for concrete placement around the steel truss frame, supported by the steel truss frame;
(C) constructing a bridge girder block made of concrete in which concrete is cast in the concrete casting form and embedded with a steel truss frame.
A step (d) of introducing pre-stress into the concrete of the bridge girder block by inserting the PC steel material through the hollow steel pipe of the steel truss frame; The bridge cantilever construction method according to claim 1, wherein in the step (a), at least an upper chord member of the steel truss frame is constituted by the hollow steel pipe .

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