JP2002220812A - Bridge girder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bridge girder reduced in weight, compared with a conventional concrete box girder and economically constructible with a small number of processes. SOLUTION: A bridge girder having a box-shaped section is formed by an upper floor slab 11 of concrete, a lower floor slab 12 of concrete provided on the lower side of the upper floor slab, and a web 13 for mutually connecting the both. The web 13 is formed of a plurality of plate members arranged in the axial direction of the bridge girder, and each of the plate members is formed so that the width is gradually extended from the height directional middle position toward the upper edge to be connected to the upper floor slab and the lower edge to be connected to the lower floor slab. The plate member is formed of a steel having flanges bonded along the upper edge and lower edge, and stud dowel implanted on the flanges are buried in and bonded to the concrete of the upper floor slab or lower floor slab. The plate member may be formed of precast concrete.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bridge girder such as a road bridge or a railway bridge, and more particularly to a bridge girder having an upper slab and a lower slab made of concrete and a web made of a steel member or a precast concrete member.

[0002]

2. Description of the Related Art Conventionally, a bridge girder is generally formed of concrete, particularly prestressed concrete. In a concrete bridge with a long span, the cross section of the girder is usually a box shape, and is composed of an upper slab, a lower slab, and a web connecting these. In a bridge girder made of such concrete, the web occupies about 10 to 30% of the girder's own weight, and the girder's own weight is considerably larger than that of a steel bridge girder.

For this reason, it has been proposed to reduce the weight of the girder by replacing the concrete web with a steel plate. Japanese Unexamined Patent Publication (Kokai) No. 7-189425 discloses a girder using a steel flat plate as a web and a vertical girder. A girder using, as a web, a steel sheet bent in a wavy line at a bending line is disclosed. A bridge girder having a web made of such a steel member can reduce the weight of the girder to reduce the load on the foundation and substructure of the bridge. Work such as assembling and concrete casting can be omitted, and it is possible to save labor and shorten the construction period.

[0004]

However, a bridge girder using a steel member as a web as described above has the following problems. The steel member is manufactured in advance in a factory or the like, and is supported at a predetermined position at a bridge girder erection site, and is integrated with the concrete of the upper slab and the lower slab to be cast on site. Then, as the erection progresses in the axial direction of the bridge girder, steel members having a predetermined length are sequentially joined. Steel members are generally joined by welding. However, welding at an erection site has poor conditions, requires many costs, and is an obstacle to shortening the process. In particular, in the so-called cantilever method, in which the bridge girder under construction is cantilevered and a sequential girder is built at the tip, it is difficult to increase the length of one construction block, and many joints of steel members are repeated. To do,
The above problem becomes more remarkable.

When a steel plate is used for the web, when a prestress in the axial direction of the bridge girder is introduced into the concrete of the upper slab or the lower slab, the steel member restrains the deformation and the compressive stress is efficiently applied to the concrete. There is a problem that is not introduced.

On the other hand, when a corrugated steel member is used for the web, the web member is easily deformed in the axial direction of the bridge girder, and prestress is efficiently introduced into the concrete of the upper deck or the lower deck. A lot of trouble and cost are required for bending into a waveform.

[0007] The present invention has been made in view of the above circumstances, and provides a bridge girder that can be economically constructed with a reduced number of steps while reducing the weight as compared with a conventional concrete box girder. The purpose is to do.

[0008]

Means for Solving the Problems In order to solve the above problems, the invention according to claim 1 comprises: an upper slab made of concrete; a lower slab provided below the upper slab and made of concrete; It is a bridge girder having a web having a box shape in cross section, comprising a web for connecting these,
A plurality of plate members are arranged in the axial direction of the bridge girder, and each of the plate members is connected to the upper side and the lower floor plate joined to the upper floor plate from a middle position in the height direction. To provide a bridge girder that gradually widens as it approaches the bottom.

In such a bridge girder, the plate-like member serving as a web is joined to the concrete of the upper floor slab and the lower floor slab while being separated at a predetermined width in the axial direction of the bridge girder. Therefore, it is not necessary to join these plate members, and the process of constructing the bridge girder is simplified. In addition, since the plate-like members before being installed at the predetermined positions have a predetermined width and are independent from each other, the handling is easy.

[0010] Further, since the plate-shaped member is joined to the upper floor slab or the lower floor slab with the entire lengths of the upper side and the lower side, respectively, the rod-shaped member is joined to the upper floor slab or the lower floor slab like a truss structure. The structure of the joint is not complicated, and the local increase in stress is reduced.

When the plate-like member is integrated with the concrete of the upper slab and the lower slab as a web, a compressive force is applied in a diagonal diagonal direction to the shear force acting on the bridge girder in the plate-like member. Tensile force acts. At this time, since the width of the plate-shaped member increases as it approaches the upper side and the lower side, the compressive and tensile forces in the oblique direction are effectively transmitted to the upper and lower slabs and resist the shearing force. Can be. Also, the width of the middle portion of the plate-shaped member in the vertical direction is reduced, so that the weight is reduced.

Further, since the plate-like members are not continuous in the axial direction of the bridge girder, when prestress is introduced into the concrete of the upper deck or the lower deck, the deformation of the upper deck or the lower deck is slightly restrained. The compression stress is effectively introduced in the axial direction of the bridge girder. The plate member is desirably a steel plate material, but may be made of precast concrete.

According to a second aspect of the present invention, in the bridge girder of the first aspect, the plate-like member is a steel plate, and has an oblique rib between the upper side and the lower side.

The steel plate has a small thickness and may be buckled when a compressive force acts in the in-plane direction. However, by providing a rib in a direction in which the compressive force acts and increasing the rigidity, the oblique seating can be achieved. Bowing can be prevented.

According to a third aspect of the present invention, in the bridge girder according to the second aspect, the rib is made of concrete formed by welding and joining a plurality of projections to an inner surface of the steel plate and embedding the projections. Shall be.

In this bridge girder, the concrete member is integrated with the steel plate by the projection, and the rigidity of the steel plate increases. Therefore, buckling of the steel plate is effectively prevented. Further, compared to the case where the ribs are formed by welding and joining steel members, it is possible to avoid the formation of the welding line so as to cross the direction in which the tensile force acts obliquely. Therefore, there is no influence of heat due to welding, and the requestability of members is improved.

According to a fourth aspect of the present invention, in the bridge girder of the first aspect, the plate member is a concrete plate, and oblique prestress is introduced between the upper side and the lower side. Shall be.

In this bridge girder, a plate-like member serving as a web can be formed on site, and the cost can be reduced. In addition, cracks can be prevented from occurring by introducing a pre-stress in advance with respect to the tensile force acting in the oblique direction of the plate member.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view and a cross-sectional view of a bridge girder according to an embodiment of the present invention, and FIG. 2 is a perspective view of the same bridge girder from below. FIG. 3 is a side view showing a portion supported by a pier of the same bridge girder. The bridge girder 2 is a continuous girder supported on a plurality of piers 1a and 1b and an abutment (not shown), and includes a concrete upper slab 11 and a concrete lower slab 12 supported below. The main part is composed of a steel member 13 which connects the upper floor slab 11 and the lower floor slab 12 and functions as a web.

The upper floor slab 11 is continuous in the axial direction of the bridge girder 2 and has a road surface formed thereon. A PC steel material (not shown) is buried in the axial direction and at right angles thereto. . Prestress is introduced by tensioning these PC steel materials and fixing them to concrete, and when a negative bending moment acts on the bridge girder,
In addition, when a load of a vehicle or the like acts on the upper floor slab 11, harmful cracks or the like are not generated. On the other hand, prestress is also introduced into the lower deck 12 in the axial direction of the bridge,
It can resist tensile stress based on a positive bending moment.

A tension member in the axial direction of the bridge girder 2 is disposed outside the concrete member and inside the box-shaped girder cross section, and the tension of the tension member causes the concrete of the upper slab 11 and the lower slab 12 to be concreted. Prestress can also be introduced into

As shown in FIG. 4, the steel member 13 includes a main body 21 made of a steel plate and functioning as a web, and an upper flange 22 and a lower flange 23 which are provided substantially at right angles along the upper and lower sides thereof. And the main part is constituted.

The main body 21 has the smallest width at an intermediate position between the upper side and the lower side, and the width is linearly enlarged as approaching the upper side or the lower side, and is a plate member having a drum-like shape. . The upper flange 22 and the lower flange 23 are joined to the upper edge or the lower edge of the main body 21 by welding, and a plurality of stud dowels 24 and 25 are planted on the upper surface of the upper flange 22 and the lower surface of the lower flange 23. Has been established. The concrete of the upper slab 11 and the lower slab 12 is formed so as to be in close contact with the upper surface of the upper flange 22 or the lower surface of the lower flange 23 and to embed the stud dowels 24 and 25, thereby forming the upper slab 11 and The steel member 13 and the lower floor slab 12 are integrated.

A plurality of stud dowels 26 are formed along one diagonal line on the inner side of the box girder section of the main body 21.
Has been planted. A concrete member 27 is formed so as to be in close contact with the steel plate forming the main body 21 and to embed the stud dowel 26 therein. The concrete member 27 has a columnar shape in an oblique direction, and when a large compressive stress acts in this direction, the main body 21
In addition to preventing buckling of the steel plate, a part of the compressive force is borne.

As shown in FIG. 2 or FIG. 3, the steel members 13 are arranged in the axial direction in two planes substantially parallel to the axis of the bridge girder 2, and the upper slab 11 and the lower slab 12 are box-shaped. Connect to When a bending moment acts on the bridge girder 2, the upper slab 11 and the lower slab 12 are integrated and resist.

Further, since the width of the steel plate forming the main body 21 of the steel member 13 is reduced at the middle portion in the vertical direction, a substantially rhombic opening 14 is formed between the arranged steel members 13. As for the shear force, as shown in FIG. 3, the oblique tensile force A acting in each steel member 13 is applied.
And the compression force B in the direction intersecting with this. The compressive force B in the oblique direction is partially shared by the concrete member 27, and the buckling of the main body 21 due to the compressive force B is prevented by the concrete member 27.

Further, the steel member 13 serving as the web is formed of the bridge girder 2.
, And the deformation of the upper floor slab 11 or the lower floor slab 12 in the axial direction is reduced. Therefore, prestress can be effectively introduced into the upper floor slab 11 or the lower floor slab 12 with a small amount of tension material.

Next, an example of a method of constructing the bridge girder 2 will be described. First, on the pier 1, put a concrete beam 2
A column cap 2b including a is formed and temporarily fixed to the pier 1. Then, digits of a predetermined length are sequentially added so as to overhang both sides in a cantilever state. The length to be added at one time is set to be equal to the interval at which the steel members 13 are arranged in the axial direction of the bridge girder,
A precast segment 2c having this length is formed in advance, and these are sequentially joined. As shown in FIG. 5, the precast segment 2c is formed of an upper floor slab 11, a lower floor slab 12, and a pair of steel members 13 having a predetermined length in the axial direction of the bridge girder. Is provided with a duct (not shown) for inserting a tendon.

The precast segment 2c is lifted by a crane or the like, and is supported at the tip of a cantilevered bridge girder being erected.
Ties with segments that are already cantilevered.

In the bridge girder according to the present invention, concrete for the upper slab and the lower slab may be cast in place. In addition to the cantilever erection method as described above, a method of connecting precast segments on a shoring method, a method of placing concrete on the upper slab and the lower slab on the shoring method, and adding a bridge girder sequentially to the rear. And extruding it forward, so-called extrusion method, etc., can also be constructed by various methods.

FIG. 6 is a schematic perspective view showing a precast concrete member 30 functioning as a web of a bridge girder, instead of the steel member 13 used in the bridge girder 2 shown in FIGS. This precast concrete member 30
Has a minimum width at an intermediate portion between the upper side and the lower side, and the width increases linearly toward the upper side and the lower side, similarly to the steel member 13 shown in FIG. The thickness is
The entire area is substantially uniform, and the tendon material 31 is embedded in an oblique direction in which a tensile force acts, and a prestress is introduced. Further, a plurality of reinforcing bars 32 project from the inside of the concrete on the end surfaces of the upper side and the lower side.
The concrete of the upper slab and the lower slab is formed so as to embed the concrete.

[0032]

As described above, in the bridge girder according to the present invention, the web can be reduced in weight as a steel member or a precast concrete member, and the web is formed by arranging independent plate members. Therefore, the construction of the bridge girder becomes easy and the cost is reduced. In addition, the web restrains the deformation in the axial direction less, and the prestress of the upper floor slab or the lower floor slab can be effectively introduced.

[Brief description of the drawings]

FIG. 1 is a side view and a sectional view of a bridge girder according to an embodiment of the present invention.

FIG. 2 is a perspective view of the bridge girder shown in FIG. 1 as viewed from below.

FIG. 3 is a side view showing a portion supported by a pier of the bridge girder shown in FIG. 1;

FIG. 4 is a schematic perspective view of a steel member functioning as a web in the bridge girder shown in FIG.

FIG. 5 is a schematic perspective view of a precast segment used in one construction method of the bridge girder shown in FIG. 1;

6 is a schematic perspective view of a precast concrete member that can be used as a web instead of the steel member shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Bridge pier 2 Bridge girder 11 Upper deck 12 Lower deck 13 Steel member 14 Opening 21 Main part of steel member 22 Upper flange 23 Lower flange 24, 25, 26 Stud dowel 27 Concrete member 30 Precast concrete member 31 Tensile material 32

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Junji Yasuaki 13-4, Arakicho, Shinjuku-ku, Tokyo Sumitomo Construction Co., Ltd. (72) Inventor Kenji Umezu 4-13, Arakicho, Shinjuku-ku, Tokyo Sumitomo Construction Co., Ltd. F-term (reference) 2D059 AA08 AA11 AA14 BB35 BB39 CC03

Claims (4)

[Claims] 1. A bridge girder having an upper slab made of concrete, a lower slab made of concrete, provided below the upper slab, and a web connecting these, and having a box-shaped cross section. The web has a plurality of plate members arranged in the axial direction of the bridge girder, and each of the plate members has an upper side joined to the upper floor slab from a middle position in a height direction. A bridge girder having a width gradually increased as approaching a lower side joined to the lower floor slab. 2. The bridge girder according to claim 1, wherein the plate-shaped member is a steel plate, and has a diagonal rib between the upper side and the lower side. 3. The bridge girder according to claim 2, wherein the rib is formed of concrete formed by welding and joining a plurality of projections to an inner surface of the steel plate and embedding the projections. 4. The bridge girder according to claim 1, wherein the plate-like member is a concrete plate, and oblique prestress is introduced between the upper side and the lower side.