JP2001146713A - Continuous beam bridge structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuous beam bridge structure capable of easily introducing prestress to an intermediate supporting point of a continuous beam bridge. SOLUTION: A corrugated steel plate wave 11 is placed to a steel girder 1 part in an intermediate supporting point of a continuous beam. Prestress is introduced to a concete floor slab 2 in the intermediate supporting point placing the corrugated steel plate wave 11 thereto. Prestress can be easily introduced to the intermediate supporting point of a continuous beam bridge. A space for introducing prestress is not required, introduced prestress is clarified, and even when prestress is decreased by drying shrinkage and creep, optimum prestress can be always reintroduced. When reintroduction of prestress is used together with prestress introduction in the direction of a bridge axis by jack up/down, more accurate prestress can be introduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a continuous girder bridge.

[0002]

2. Description of the Related Art FIG. 9 shows a two-span continuous composite girder bridge in which a steel girder 1 and a concrete floor slab 2 are mechanically connected via studs 3. As compared with the non-composite girder, the composition such as bending increases and the weight of the steel girder 1 can be reduced, so that the cost can be reduced. In addition, the bridge structure is advantageous in that it is not easily damaged due to, for example, the occurrence of fatigue cracks.

[0003] In a continuous girder bridge, an intermediate bearing 4 is generally arranged also at an intermediate portion of the bridge, and the steel girder 1 is supported by the intermediate bearing 4 as shown in FIG.
When such a continuous girder receives a load (live load) of an automobile or the like, in the span intermediate portion A, FIG.
Due to the positive bending moment m1 shown in FIG. 9, the compressive stress σc shown in FIG.
Therefore, no tensile stress that causes cracks in the concrete floor slab 2 is generated.

However, at the intermediate fulcrum B, FIG.
By the negative bending moment m2 as shown in (c),
When the tensile stress .sigma.t as shown in FIG. 9 (e) is generated in the concrete slab 2 and the tensile stress exceeds the crack generation stress of concrete, FIG. 9 (c)
As shown in (1), there is a possibility that cracks 5 may occur in the concrete slab 2.

Therefore, in order to prevent the occurrence of cracks 5 in the concrete slab 2 at the intermediate fulcrum B as described above, a structure in which prestress is introduced into the portion has been adopted.

FIG. 10 shows an intermediate fulcrum B of the composite girder.
Shows a case where prestress is directly introduced into the concrete slab portion of the present invention. For example, a precast slab 6 is disposed at the intermediate fulcrum portion B, and a prestressed steel wire 7 is provided in the bridge axis direction of the precast slab 6. By introducing a prestress using the method, a compressive stress σc is uniformly generated in the precast floor slab 6 at the intermediate fulcrum B as shown in FIG.

[0007] With the introduction of this prestress,
A live load acts on the lower flange of steel girder 1, resulting in a tensile stress σt.
However, when the prestress is subtracted from the compressive stress .sigma.c due to the prestress, the compressive stress .sigma.c1 remains in the precast floor slab 6, as shown in FIG.
Cracks do not occur in the precast floor slab 6.

FIG. 11 shows a case where prestress is introduced in the bridge axis direction by jacking up the steel girder 1 by δ at the intermediate fulcrum B while restraining the vertical displacement of the fulcrum at the bridge end. The stud 3 is welded to the steel girder 1 in advance, and as shown in FIG. 11A, the concrete floor slab 2 is cast while the intermediate fulcrum B is jacked up by δ. (FIG. 11 (b)), and after hardening, the jack is loosened to reduce the value by δ (FIG. 11 (b)).
(C)) The steel girder 1 sinks to its original position due to the springback amount and the weight of the concrete slab 2 and the steel girder 1 which have been raised before.
As shown in (d), a compressive stress σc is introduced.

[0009]

However, FIG.
The method of directly introducing prestress into a concrete slab as described in (1) has the following problems. Since the precast slab 6 is constrained by the steel girder 1 and the stud 3, prestress is unlikely to enter near the main girder, and prestress is not uniformly introduced to the entire concrete slab.

It is necessary to secure a space for arranging jacks for introducing prestress, but it is necessary to fill this space with joint concrete 8 after introducing the prestress, so that the process is extended accordingly. After the introduction of prestress, it is not possible to estimate the amount by which the prestress decreases due to drying shrinkage or creep. Further, even if the amount of prestress is reduced, it is difficult to reintroduce the prestress and secure a certain prestress.

[0011] In the prestress introduction method using jack-up and jack-down as shown in FIG.
There are problems listed below. The raised amount of the steel girder 1 is actually about 1 m, and it is necessary to pay sufficient attention to the safety of field work.

[0012] The amount of prestress to be introduced is different even if the amount of raising is the same due to drying shrinkage of the concrete during hardening of the concrete, and a predetermined prestress may not always be introduced. Once the amount of jack-up is set and the concrete hardens, it cannot be corrected even if the amount of pre-stress is insufficient when jacking down.

[0013] Even if the amount of prestress is unexpectedly reduced due to drying shrinkage and creep of the concrete after the jack down, it cannot be corrected. It is to be noted that the amount of decrease in prestress can be measured by embedding a sensor or the like, but such a method is very expensive and requires special techniques.

The present invention has been made in view of the above-described problems of the continuous girder bridge, and has been developed even when a live load is applied without introducing prestress to the intermediate fulcrum portion of the continuous girder bridge. It is an object of the present invention to provide a continuous girder bridge structure in which cracks do not occur in the floor slab of the intermediate fulcrum.

[0015]

In order to achieve the above-mentioned object, a continuous girder bridge structure of the present invention has a corrugated steel sheet web disposed on a steel girder portion at an intermediate fulcrum of a continuous girder. The prestress is to be introduced into the concrete slab at the middle fulcrum where the is placed. And
This makes it possible to easily introduce prestress into the intermediate fulcrum of the continuous girder.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A continuous girder bridge structure according to the present invention has a corrugated steel sheet web disposed on a steel girder portion at an intermediate fulcrum portion of a continuous girder, and is provided on a concrete slab of the intermediate fulcrum portion where the corrugated steel sheet web is disposed. Prestress is introduced.
That is, as shown in FIG. 1 (c), the continuous girder bridge structure of the present invention has a negative bending moment (-
M) The corrugated steel sheet web is used in the range of M), and prestress is introduced into the concrete slab on the corrugated steel sheet web.

In the continuous girder bridge structure of the present invention, the prestress is easily introduced into the concrete slab on the corrugated steel web by arranging the corrugated steel web on the steel girder portion at the middle fulcrum of the continuous girder. Will be able to do it.

In the continuous girder bridge structure of the present invention, when an adhering plate is attached to the middle fulcrum position of the corrugated steel sheet web and concrete is filled in a cavity formed by the adhering plate and the corrugated steel sheet web, In the concrete filling section,
Strength against compressive load increases.

Further, in the continuous girder bridge structure of the present invention,
When a large number of ring-shaped dowels are attached instead of the upper flange of the corrugated steel sheet web, prestress can be more effectively introduced into the concrete slab.

At this time, when the steel girder and the corrugated steel sheet web are attached, only the upper flange of the steel girder is extended toward the corrugated steel sheet web side, and the corrugated steel sheet web is inserted into the notch for insertion provided in this projection. In the case of fitting and welding integrated,
The stress concentration at the joint can be reduced. Also,
If the overhang of the upper flange of the steel girder is rounded,
Stress concentration at the joint can be further reduced.

[0021]

1 to 8 show a continuous girder bridge structure of the present invention.
A description will be given based on the embodiment shown in FIG. 1A and 1B are diagrams for explaining the outline of a continuous girder bridge structure of the present invention. FIG. 1A is a diagram in which a bridge girder is bridged between piers, FIG. 1B is a diagram in which concrete is cast on the bridge girder, and FIG. FIG. 2 is a view for explaining a bending moment acting on a bridge girder, FIG. 2 is an explanatory view of a continuous girder bridge structure of the present invention, a perspective view of an intermediate fulcrum portion, and FIG. 3A is a view of FIG. , (B) is a view of FIG. 2 viewed from a plane direction,
(C) is a view of FIG. 2 as viewed from the front, FIG. 4 is an explanatory view (perspective view) when introducing a prestress in the continuous girder bridge structure of the present invention shown in FIG. 2, (a) of FIG. ) Is A in FIG.
FIG. 4A is a view of a cross section viewed from a plane direction, and FIG.
FIG. 6 (c) is a cross-sectional view taken along line BB of FIG. 4, FIG. 6 (d) is a cross-sectional view taken along line CC of FIG. 4, and FIG. 6 is an explanatory view of another embodiment of the continuous girder bridge structure of the present invention. (a) is a view from the side, (b)
7 is a perspective view of an intermediate fulcrum, FIG. 7 is an enlarged perspective view of a main part of FIG. 6B, FIG. 8 is an explanatory view of a welded portion between the steel girder and the corrugated steel sheet web in the embodiment shown in FIG. FIG. 3A is a diagram of a normal welding structure, FIG. 3B is an explanatory diagram of an upper flange of a steel girder adopting the structure of the present invention, and FIG. 3C is a diagram of a welding structure adopting the structure of FIG.

1 to 8, reference numeral 11 denotes a corrugated steel sheet web. In the continuous girder bridge structure of the present invention, the corrugated steel sheet web 11 is disposed on a steel girder 1 at an intermediate fulcrum B of the continuous girder. It is.

At the time of construction, first, the corrugated steel sheet web 11 and the I-shaped steel girder 1 are welded to each other, and as shown in FIG. And bridge the bridge girder. At this time, since the corrugated steel sheet web 11 has upper and lower flanges 11a and 11b, the corrugated steel sheet web 11 does not spread like an accordion.

In this state, the steel girder 1 and the corrugated steel web 11
When concrete is cast on the upper flanges 1a, 11a, the steel beams 1 and the corrugated steel sheet web 11 have upper flanges 1a, 1a.
The concrete slab 2 and the steel girder 1 and the corrugated steel sheet web 11 are joined via the studs 3 welded on 1a.

After hardening of the concrete, FIG.
As shown in (b), the PC steel rod 14 and the nut 15 are attached to the anchor 13 attached near the corrugated steel sheet web 11 of the steel girder 1, and the PC steel rod 14 is tightened.
Prestress is introduced into the concrete slab 2 in the area of the corrugated steel sheet web 11.

Assuming that the average prestress to be introduced into the concrete slab 2 is 1.47 MPa, the prestress amount P to be introduced is the concrete slab 2 (width 16 m, thickness 0.32
m) Overall, P = 16 × 0.32 × 1.47 × 10 ⁶ = 752640
0N.

Therefore, if the power is set to about 400 tons per digit, the PC steel rod 14 can be applied with a force of about 490 kN per rod, and as shown in FIG.
What is necessary is just to design the anchor 13 so that the PC steel rod 14 can be set. Generally, the width of the upper flange 1a of the steel girder 1 is 500 to 600 mm, and it is not so difficult to mount about eight PC steel rods 14 per girder.

FIG. 2 is a perspective view of an intermediate fulcrum portion in the continuous girder bridge structure of the present invention. A considerable load acts on the intermediate bearing 4 disposed at the intermediate fulcrum portion.
Therefore, in the embodiment shown in FIGS. 2 and 3, the contact plate 16 is attached to the corrugated steel sheet web 11 at a position corresponding to the intermediate support 4, and the contact sheet 16 and the corrugated steel sheet web 11 are formed. The cavity 17 is filled with concrete 17 so as to resist a compressive load. A cross girder 18 is disposed on the intermediate fulcrum to restrain the steel girder 1 from torsional deformation. The cross girder 18 is joined to the corrugated steel sheet web 11 by welding or bolts.

FIGS. 4 and 5 show the detailed arrangement of the PC steel rod 14. FIG. Among them, section A in FIG. 4 is an outer bridge axial section of a main girder made of steel girder 1, corrugated steel web 11, and concrete slab 2, section B is an inner cross section of the main girder, and section C is also a main girder. It is a diagram showing a center cross section of a girder.

In the section A, the PC steel rod 14 is arranged horizontally in the bridge axis direction. In the section B, the PC steel bars 14 are arranged in the same manner as in the section A, and the curved PC steel wires 19 are arranged to introduce a compressive force into the concrete slab 2. The PC steel wire 19 is fixed to the anchor 13 using, for example, a wedge-shaped bracket 20. However, when sufficient prestress can be introduced only by the horizontal PC steel rod 14, the above-mentioned PC steel wire 19 is unnecessary.

In the section C, when the prestress introduced from the main girder as described above is not enough, the arrangement of the PC steel wire 19 for introducing the prestress in the bridge axis direction directly to the concrete slab 2 is adopted. It is shown. In this case, the anchoring portion of the PC steel wire 19 extends the lower surface of the concrete slab 2 so as to be slightly larger, and a reinforcing steel bar 21 for preventing cracking due to the compressive force from the PC steel wire 19 is embedded in that portion. . The introduction of the prestress in the section C is performed using a jack from below the concrete slab 2.

In the above embodiment, the corrugated steel sheet web 11 is provided with the upper flange 11a, but FIGS. 6 to 8 show embodiments without the upper flange. If the upper flange is not provided, when the prestress is introduced, the upper flange does not resist, so that the prestress can be more effectively introduced into the concrete slab 2.

When such an upper flange is not provided, the corrugated steel sheet web 11 and the concrete slab 2 are connected by forming a hole in the upper part of the corrugated steel sheet web 11 and attaching a ring-shaped dowel 22 to the hole. Do. In the case of such a ring-shaped dowel 22, there is an advantage that the position of the reinforcing bar can be easily maintained as compared with the straight bar.

When the corrugated steel sheet web 11 without such an upper flange is used, when the girder is hung on the intermediate support 4, there is a problem that bending rigidity is insufficient. In order to cope with this problem, the tensile strength held by the upper flange may be shared by attaching the PC steel rod 14 in advance. 6 to 8.
In the case of using the corrugated steel sheet web 11 without the upper flange shown in FIG.
The connection between the cross beam 18 and the corrugated steel sheet web 11 is performed by welding or bolts.

The front and rear steel girders 1 and the corrugated steel web 11 are usually joined by butt welding at a position where the moment is small. However, when the corrugated steel web 11 having no upper flange is used, the steel girder is used. As shown in FIG. 8A, there is a concern that a sharp cross-sectional change may occur at the upper flange 1a of the tire 1 to cause fatigue cracks.

Therefore, in such a case, FIG.
As shown in FIG. 8, only the upper flange 1a of the front and rear steel girders 1 is extended toward the corrugated steel sheet web 11, and the notch for insertion 1b provided in this extended portion is provided with a notch as shown in FIG. The corrugated steel sheet web 11 is fitted and integrated by welding. In this case, the stress concentration at the joint can be reduced.

At this time, as shown in FIG. 8B, the overhang of the upper flange 1a of the steel girder 1 is rounded so that the rigidity of the upper flange 1a does not change suddenly. In this case, stress concentration at this portion can be avoided.

[0038]

As described above, according to the continuous girder bridge structure of the present invention, prestress can be easily introduced into the intermediate fulcrum of the continuous girder bridge. Further, the main girder structure of the bridge according to the present invention does not require a space for introducing prestress, and furthermore, the introduced prestress amount is clear, and even if the prestress is reduced by drying shrinkage and creep, it is always It is possible to reintroduce to the optimal amount. Further, in the main girder structure of a bridge according to the present invention, more accurate prestress can be introduced when used together with prestress introduction in the bridge axis direction by jack-up / jack-down.

In the continuous girder bridge structure of the present invention,
When a contact plate is attached to the middle fulcrum position of the corrugated steel sheet web and concrete is filled in the cavity formed by this contact plate and the corrugated steel sheet web, the concrete filling portion increases the proof stress against the compressive load. Can be done.

In the continuous girder bridge structure of the present invention,
When a large number of ring-shaped dowels are attached instead of the upper flange of the corrugated steel sheet web, prestress can be more effectively introduced into the concrete slab. Then, at that time, when mounting the steel girder and the corrugated steel sheet web, only the upper flange of the steel girder is extended toward the corrugated steel sheet web side, and the corrugated steel sheet web is inserted into the notch for insertion provided in this overhang portion. When integrated by welding, stress concentration at the joint can be reduced. Further, when the overhang portion of the upper flange of the steel girder is rounded, the stress concentration at the joint portion can be further reduced.

[Brief description of the drawings]

1A and 1B are diagrams illustrating an outline of a continuous girder bridge structure of the present invention, wherein FIG. 1A is a diagram in which a bridge girder is bridged between piers, FIG. 1B is a diagram in which concrete is cast on the bridge girder, and FIG. () Is a diagram for explaining the bending moment acting on the bridge girder.

FIG. 2 is an explanatory view of a continuous girder bridge structure of the present invention, and is a perspective view of an intermediate fulcrum portion.

3A is a diagram of FIG. 2 viewed from the side, FIG. 3B is a diagram of FIG. 2 viewed from the plane, and FIG. 3C is a diagram of FIG. 2 viewed from the front.

FIG. 4 is an explanatory view (perspective view) when introducing a prestress in the continuous girder bridge structure of the present invention shown in FIG. 2;

5 (a) is a view of the AA cross section of FIG. 4 viewed from the plane direction, FIG. 5 (b) is a cross sectional view of AA of FIG. 4, and FIG.
FIG. 4D is a sectional view taken along line B-C of FIG. 4.

FIGS. 6A and 6B are explanatory views of another embodiment of the continuous girder bridge structure of the present invention, wherein FIG. 6A is a view seen from the side, and FIG. 6B is a perspective view of an intermediate fulcrum.

FIG. 7 is an enlarged perspective view of a main part of FIG. 6 (b).

8 (a) and 8 (b) are explanatory views of a welded portion between the steel girder and the corrugated steel sheet web in the embodiment shown in FIG. 6, wherein (a) is a normal welding structure diagram and (b) is a steel girder employing the structure of the present invention. FIG. 3C is an explanatory view of the upper flange, and FIG. 4C is a welding structure diagram when the structure of FIG.

FIG. 9 is a diagram illustrating a problem of a conventional continuous girder bridge;
(A) is a view from the side, (b) is a view from the front of the intermediate fulcrum part of (a), (c) is an explanatory view when a live load acts on the continuous girder bridge, (d) Is an illustration of the stress acting on the mid-span when a live load is applied to the continuous girder bridge,
(E) is an explanatory view of the stress acting on the intermediate fulcrum when a live load acts on the continuous girder bridge.

FIG. 10 is an explanatory view of a conventional method of introducing a prestress to an intermediate fulcrum portion of a continuous girder bridge, wherein (a) is an explanatory view during the introduction of the prestress, (b) is an explanatory view after the introduction of the prestress, (C) is an explanatory view of the stress acting on the intermediate fulcrum after the introduction of the prestress, (d) when a live load is applied,
It is explanatory drawing of the stress which acts on an intermediate fulcrum part.

FIG. 11 is an explanatory view of another conventional method for introducing a prestress to an intermediate fulcrum portion of a continuous girder bridge. (A) is an explanatory view of jacking up a steel girder, and (b) is casting concrete. (C) is an explanatory diagram when the steel girder is jacked down, and (d) is an explanatory diagram of the compressive stress introduced into the concrete slab by jacking down.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel girder 1a Upper flange 1b Notch 4 Intermediate bearing 11 Corrugated steel sheet web 11a Upper flange 13 Anchor fitting 14 PC steel bar 15 Nut 16 Attached plate 17 Concrete 19 PC steel wire 22 Ring dowel

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiro Yasuda 1-89, Minamikohoku, Suminoe-ku, Osaka-shi, Osaka Inside Hitachi Zosen Corporation (72) Inventor Takeshi Takeshi 1-chome, Minamikohoku, Suminoe-ku, Osaka-shi, Osaka 7-89 F-term in Hitachi Zosen Corporation (reference) 2D059 AA05 AA14 BB35 CC04 GG55

Claims (5)

[Claims] 1. A continuous girder, wherein a corrugated steel sheet web is disposed on a steel girder part at an intermediate fulcrum part of a continuous girder, and a prestress is introduced into a concrete slab of the intermediate fulcrum part where the corrugated steel sheet web is disposed. Girder bridge structure. 2. The continuity according to claim 1, wherein an adhering plate is attached to a middle fulcrum position of the corrugated steel sheet web, and a cavity formed by the adhering plate and the corrugated steel sheet web is filled with concrete. Girder bridge structure. 3. Instead of the upper flange of the corrugated steel sheet web,
The continuous girder bridge structure according to claim 1 or 2, wherein a number of ring-shaped dowels are attached. 4. A steel girder and a corrugated steel sheet web in the continuous girder bridge structure according to claim 3, wherein only the upper flange of the steel girder is extended toward the corrugated steel sheet web side, and a fitting provided on the extended part is provided. A continuous girder bridge structure in which a corrugated steel sheet web is inserted into a notch and integrated by welding. 5. The continuous girder bridge structure according to claim 4, wherein the overhang portion of the upper flange of the steel girder is rounded.