JP2009030277A - Construction method of composite steel floor slab girder bridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a construction method of a composite steel floor slab girder bridge that can enlarge the installation pitch of longitudinal ribs and cross beams (lateral ribs) heretofore required to prevent buckling of a deck plate (a steel floor slab panel) due to the own weight of a steel member and the weight of concrete in constructing the composite steel floor slab girder bridge. <P>SOLUTION: The construction method of the composite steel floor slab girder bridge comprises disposing a deck plate 4 above the main beam 2 extending in a bridge axis direction and the cross beams (the lateral ribs) 3 extending in an orthogonal direction to the bridge axis direction, welding the longitudinal ribs 5 to the upper face of the deck plate 4 in the bridge axis direction, arranging reinforcing bars 6, 7 above them, and placing concrete in the upper face space of the deck plate 4 while including the reinforcing bars 6, 7 therein, wherein concrete is placed beforehand in a narrow portion 8 extending in an orthogonal direction to a bridge axis and including a reinforcement part orthogonal at least to the bridge axis, in an intermediate position between the adjacent cross beams (lateral ribs) 3, and after the concrete placed beforehand is hardened, concrete is placed in the unplaced space part. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for constructing a synthetic steel slab girder bridge that forms a girder bridge by dynamically synthesizing a steel structure and concrete.

  A conventional steel / concrete composite steel deck girder bridge basically has a structure in which a steel plate called a deck plate and reinforced concrete are synthesized (Patent Document 1).

  Specifically, vertical ribs are welded and fixed on the top surface of the deck plate in the direction of the bridge axis, and above them, the reinforcing bars are arranged so as to extend in parallel and perpendicular to the direction of the bridge axis, and concrete is cast into the space. A synthetic steel floor slab girder bridge will be formed.

  Moreover, as a basic construction method of the synthetic steel floor slab girder bridge, necessary members such as vertical ribs and horizontal ribs are arranged on the steel plate for the deck plate in the factory, and are integrated by welding or the like. After the plate panel and main girder block are transported to the site and installed, a formwork is formed at the end of the deck plate, and concrete is cast into a synthetic steel floor slab. A main girder extending in parallel with the bridge axis direction and a cross beam (lateral rib) extending in a direction orthogonal to the bridge axis direction are provided in directions orthogonal to each other (Patent Document 1).

  However, when forming such a steel / concrete composite deck, it is necessary for the deck plate itself to support the dead load before the synthesis is completed.

  Specifically, before the synthesis is completed, when steel concrete slab panels and main girder blocks are installed and concrete is placed on the deck plate, the dead load (weight of steel plate, concrete, etc.) is supported only by steel members. There is a problem that the deck plate may be buckled.

  If you try to make a steel plate for a deck plate that is reinforced and strong enough not to buckle, you will either increase the thickness of the deck plate steel plate or increase the number of vertical and horizontal ribs. Since the weight of the member is increased and the manufacturing cost is increased, the problem cannot be fundamentally solved. In addition, most of the reinforcing steel used to reinforce the deck plate is no longer necessary from the viewpoint of the strength of the steel / concrete composite slab after the cast concrete has hardened. Therefore, there has been a demand for a synthetic steel slab structure and a construction method that do not require the use of such excessive reinforcing members.

  On the other hand, a steel / concrete composite floor slab that can secure the rigidity when concrete is cast on the steel sheet and can reduce the weight of the steel material, and its construction method as a steel sheet and projecting on the surface of the steel sheet A steel / concrete composite floor slab for a bridge floor slab comprising a concrete slip-preventing member, a reinforcing bar disposed above the steel sheet, and concrete placed on the steel sheet, A part of the concrete to be placed thereon is pre-placed to form a concrete beam having the pre-placed concrete, part of the reinforcing bar and part of the steel plate, A concrete beam is provided as a steel plate reinforcement for holding dead loads before synthesis, and then the steel / concrete composite floor slab is installed at a predetermined position on the bridge to provide the concrete beam on the steel plate. Is To have no part, it is proposed that a synthesized slab than to hit back the concrete (Patent Document 2).

However, in this proposal, the technical premise is a structure and construction method as a composite floor slab, and a beam-like structure is formed by placing a part of concrete to be placed on a steel plate in advance at a factory or the like. In addition, the concrete beam-like structure is used as a steel plate reinforcing material for holding a dead load before synthesis at the time of erection, and in order to reinforce the bottom steel plate that does not stand by itself, the concrete beam is closely packed with a 1 m pitch. It is necessary to provide it. In addition, because no reinforcing steel plates such as vertical ribs are arranged in the bridge axis direction, the cross section constant in the main girder direction is small and the girder height is high, and the cross section constants before and after synthesis are the same. To increase the thickness and apply it to synthetic steel slabs, the effects of reducing the girder height and reducing dead load, which are the merits of synthetic steel slabs, are lost, and it is being considered for construction with synthetic steel slabs. It was not a thing. In addition, since concrete is cast in advance at factories and the like, the age difference from the concrete cast on site is large, and additional stress due to creep and drying shrinkage of the concrete is added, making the design complicated and the bridge shaft. Since there is no reinforcing member in the direction, the bottom steel plate may buckle when placing concrete on site.
Japanese Patent Laid-Open No. 11-158816 JP 2002-180420 A (paragraph 0017, paragraph 0024)

  In view of the above-described points, the object of the present invention is that the deck plate (steel slab panel) buckles due to the weight of the steel member and the weight of the concrete added during construction of the synthetic steel slab girder bridge. This can increase the installation pitch of vertical ribs and cross girders (transverse ribs) that are determined to prevent buckling during erection. An object of the present invention is to provide a method of constructing a synthetic steel slab girder bridge that can realize cost reduction.

The construction method of the synthetic steel slab girder bridge of the present invention that achieves the above-mentioned object has the following configuration (1).
(1) A deck plate is arranged above the main girder extending in the bridge axis direction and the cross beams and horizontal ribs extending in the direction orthogonal to the bridge axis direction. In a construction method of a synthetic steel slab girder bridge, in which a reinforcing steel bar is placed on the upper side of the deck plate and concrete is placed by including the reinforcing steel bar in the upper surface space of the deck plate. In the middle position of the cross beams and horizontal ribs, the concrete is placed in advance in a narrow portion including a reinforcing bar portion extending in a direction orthogonal to the bridge axis direction and at least orthogonal to the bridge axis direction. A method for constructing a composite steel slab girder bridge in which concrete is cast in an unplaced space after the set concrete has hardened.

Moreover, in the construction method of the synthetic steel floor slab girder bridge of the present invention, more specifically, preferably, in the construction method of the synthetic steel floor slab girder bridge having any one of the following configurations (2) to (4): is there.
(2) The method for constructing a synthetic steel slab girder bridge as described in (1) above, wherein early-strength concrete is used as the concrete to be placed in advance.
(3) The method for constructing a composite steel slab girder bridge as described in (2) above, wherein the concrete placement in the unplaced space portion is performed after 4 days after the previous placement.
(4) The preceding narrow-width placing portion includes 2 to 5 reinforcing bars orthogonal to the bridge axis direction, and the synthetic steel deck slab according to any one of (1) to (3) above Bridge construction method.

  According to the first aspect of the present invention, the deck plate (steel slab panel) may buckle due to the weight of the steel member and the added concrete weight during construction of the synthetic steel slab girder bridge. This increases the installation pitch of vertical ribs and cross girders (transverse ribs), which are determined to prevent buckling during installation, thereby improving the productivity and cost of steel floor slab panels. A method for constructing a new synthetic steel deck siding girder bridge that can realize a reduction in the amount of steel is provided.

  According to the second and third aspects of the present invention, the entire construction period can be shortened by about 3 weeks in general as compared with the case of using ordinary concrete, and the entire construction period is shortened. The construction method of the synthetic steel slab girder bridge of the present invention can be realized.

  According to this invention concerning Claim 4, the construction method of the synthetic steel slab girder bridge of this invention is realizable, enjoying the effect mentioned above of this invention still more highly.

  Hereinafter, the construction method of the synthetic steel slab girder bridge of the present invention will be described in more detail with reference to the drawings.

  FIG. 1 is a schematic model perspective view showing a state before placing concrete on a steel slab when the method for constructing a synthetic steel slab girder bridge of the present invention is carried out.

  FIG. 2 illustrates a state immediately before the concrete is placed in advance at an intermediate position between a lateral girder and a lateral rib that are adjacent to each other when the method for constructing a synthetic steel slab girder bridge of the present invention is carried out. It is a schematic model perspective view.

  As shown in FIGS. 1 and 2, the construction method of the synthetic steel floor slab girder of the present invention includes a main girder 2 extending in the bridge axis direction and a cross girder extending in a direction orthogonal to the bridge axis direction. The deck plate 4 is arranged above the horizontal rib 3, and the vertical rib 5 is welded and fixed to the upper surface of the deck plate 4 in the direction of the bridge axis, and the reinforcing reinforcing bars (the horizontal reinforcing bar 6 and the vertical reinforcing bar 7) are arranged above it. In the construction method of the synthetic steel slab girder bridge 1 in which concrete is placed by including the reinforcing reinforcing bars in the upper surface space of the deck plate 4, an intermediate between the side beams and the side ribs 3 that are adjacent to each other. In a position, after concrete is cast in a narrow width portion 8 that extends in a direction orthogonal to the bridge axis direction and includes at least a reinforcing bar portion orthogonal to the bridge axis direction, and further, after the preceding cast concrete has hardened It is characterized by placing concrete in the unplaced space Is shall.

  According to the method for constructing a composite steel deck girder bridge according to the present invention, the concrete narrow portion including the rebar placed in advance is provided at the intermediate position between the adjacent horizontal beams and horizontal ribs 3. Since the pre-cast concrete has a so-called “node”, the buckling strength of the deck plate can be improved when the concrete is cast. Therefore, it is possible to prevent the deck plate from buckling.

  2 includes a reinforcing bar portion (horizontal reinforcing bar 6) extending in a direction orthogonal to the bridge axis direction and at least orthogonal to the bridge axis direction at an intermediate position between the adjacent cross beams and horizontal ribs 3 in FIG. The narrow width portion 8 is formed by forming a formwork for placing only the portion at the construction site and placing concrete.

  It is preferable that the narrow-width portion 8 to be placed in advance is placed so as to include at least one reinforcing bar orthogonal to the bridge axis direction in order to make the above-described “node” stronger.

  According to the knowledge of the present inventors, it is preferable to include 2 to 5 reinforcing bars perpendicular to the bridge axis direction.

  As shown in FIG. 2, the specific width W of the narrow portion 8 to be placed in advance is not particularly limited, but according to the knowledge of the present inventors, the width is about 200 mm to 350 mm. It is good to do. More preferably, it is 200 mm-300 mm. In the present invention, the pitch of the horizontal reinforcing bars is preferably about 100 mm to 150 mm, and by setting the width of the preceding concrete placing portion to the above-described range, the preceding concrete placing portion includes several reinforcing bars. This is preferable.

  In addition, the narrow portion 8 to be placed in advance does not need to be configured such that the positions of both end portions thereof exist over the entire width of the bridge. It is sufficient that the length is a minimum length capable of exhibiting “(Fushi)”.

  As the concrete to be placed in advance, it is better to use the concrete that is cured in a shorter period of time, such as concrete that is commercially available as early-strength concrete or ultra-early-strength concrete, Since curing requires less than about a month, the construction of placing concrete in an unplaced part is slow, which increases the length of the process and is generally undesirable.

  In carrying out the construction method of the present invention, it is particularly preferable that the concrete is placed in an unplaced space portion after 4 days after the prior placement. Preferably, it is effective to carry out within 4 days after 7 days.

  When placing concrete in an unplaced space portion, it is preferable to cast concrete after removing the formwork used for the previous placement.

  Regarding the synthetic steel floor slab girder bridge in which the construction method of the present invention can be adopted, the main girder structure may be either I-type or box-type, and may be of a truss structure.

  The main point is that the deck plate is placed above the main girder extending in the bridge axis direction and the cross beams and horizontal ribs extending in the direction perpendicular to the bridge axis direction. It is effective if it is adopted in the construction method of a synthetic steel floor slab girder where a reinforcing steel bar is placed on top of it, a reinforcing bar is placed above it, and the concrete is placed with the reinforcing bar inside the deck plate. It is.

FIG. 1 is a schematic model perspective view showing a state before placing concrete on a steel slab when the method for constructing a synthetic steel slab girder bridge of the present invention is carried out. FIG. 2 illustrates a state immediately before the concrete is placed in advance at an intermediate position between a lateral girder and a lateral rib that are adjacent to each other when the method for constructing a synthetic steel slab girder bridge of the present invention is carried out. It is a schematic model perspective view.

Explanation of symbols

1 Girder bridge of composite steel floor 2 Main girder 3 Cross girder (lateral rib)
4 Deck plate 5 Vertical rib 6 Horizontal reinforcing bar 7 Vertical reinforcing bar 8 Pre-placed formwork

Claims (4)

  A deck plate is arranged above the main girder extending in the bridge axis direction and the cross beams and horizontal ribs extending in the direction orthogonal to the bridge axis direction, and the vertical rib is welded and fixed in the bridge axis direction on the top surface of the deck plate. In the construction method of the synthetic steel slab girder bridge in which the reinforcing steel bars are arranged above and the concrete is placed by including the reinforcing steel bars in the upper surface space of the deck plate, they are adjacent to each other. In the middle position of the cross beam and the horizontal rib, the concrete was previously placed in a narrow portion including a reinforcing bar portion extending in a direction perpendicular to the bridge axis direction and at least perpendicular to the bridge axis direction. A method for constructing a composite steel slab girder bridge, wherein concrete is cast in an unplaced space after the concrete is hardened.   2. The method for constructing a composite steel slab girder bridge according to claim 1, wherein early-strength concrete is used as the concrete to be placed in advance.   3. The method for constructing a synthetic steel slab girder bridge according to claim 2, wherein the concrete placement in the unplaced space portion is performed after 4 days after the prior placement.   The construction method for a synthetic steel slab girder bridge according to any one of claims 1 to 3, wherein the narrow-width leading portion includes 2 to 5 reinforcing bars orthogonal to the bridge axis direction.

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