JP4437064B2 - Construction method and formwork structure of concrete floor slab for composite floor slab bridge - Google Patents

Description

  The present invention relates to a method for constructing a concrete floor slab of a hollow type composite floor slab bridge having a space below a concrete floor slab, which is a form of a bridge (bridge girder) structure, and a formwork structure used for the construction. is there.

  Synthetic slab bridges made of shape steel and concrete slabs are often used for bridges and road viaducts. In this composite floor slab bridge, T-shaped or H-shaped steel bars, which are main girders, are arranged in parallel at predetermined intervals on the pier, and a bottom steel plate is welded between the lower end surfaces of these steel bars. In the upper part of the steel bar, the upper reinforcement bar is arranged in a position slightly above the upper flange of the section steel, either directly or in parallel with the section steel, and from the upper surface of the bottom steel plate to a position slightly above the upper reinforcement bar. It is common to construct by placing concrete in a so-called open section steel box girder.

  However, this type of full-blown composite floor slab bridge that fully fills with concrete increases the height of the floor slab to maintain rigidity as the length between piers (so-called `` span length '') increases. As a result, the thickness of the concrete increases and the weight per unit area also increases. As a result, to support the increased concrete weight, the web height of the section steel needs to be higher, which further increases the weight of the composite deck slab bridge. In particular, when the span length exceeds 20 m, the weight per unit area of the section steel constituting the main girder increases rapidly. Therefore, if the span length is 25m or more, it will be difficult to build a solid type composite deck slab both mechanically and economically.

  As a technique for solving this problem, there has been proposed a composite floor slab bridge that reduces the weight of the composite floor slab bridge by eliminating the concrete filled in the lower part of the shape steel that hardly affects the strength of the floor slab bridge. For example, in Patent Document 1, T-shaped steels are arranged in parallel at required equal intervals, a bottom steel plate is welded between the lower end surfaces of the T-shaped steel, and the T-shaped steel is positioned slightly above the T-shaped steel web portion. An upper reinforcement bar is arranged perpendicular to the steel, and a lower distribution reinforcement bar is disposed in the middle of the T-shaped steel web through the web. By constructing a composite floor slab bridge by placing concrete only on the upper part from the position to a position slightly above the upper reinforcing steel bar, the weight of concrete and steel girder per unit area is reduced, and the composite floor slab bridge is reduced. A technique for extending the application length of the span length to about 40 m is disclosed.

Specifically, in order to place concrete only on the upper part of the composite floor slab bridge from a position slightly below the lower reinforcement bar to a position slightly above the upper reinforcement bar, Filled with a foamed resin plate with a specific gravity of 0.06 or less to a slightly lower position, and then put concrete on the top, or attach a support bracket to the web slightly below the lower reinforcing steel bar, and support this In this method, a corrugated steel sheet of a lower surface formwork is laid through a metal fitting, and concrete is placed on the upper part.
JP-A-60-195205

  However, the method of filling foamed polystyrene or the like disclosed in Patent Document 1 is an effective technique because the height of the hollow portion is about 700 mm if the span length is about 40 m. However, if the applicable span length exceeds 40m, the web height of the T-shaped steel will increase rapidly, and the height of the hollow portion will also increase (for example, if the span length is 60m, the hollow portion height will be about 1200mm). The material cost of the expanded polystyrene greatly increases, causing a cost increase.

  In recent years, fatigue cracks have occurred in viaducts due to repeated stress loads caused by passing vehicles and the like, and periodic maintenance inspections such as viaducts are strongly desired. However, in the composite floor slab bridge filled with the foamed resin material, there is no space at the lower part of the concrete floor slab, so that there is a problem that the occurrence of fatigue cracks cannot be sufficiently checked.

  On the other hand, the method of laying a corrugated steel plate as a lower surface formwork for placing another concrete is because the attachment of the metal fitting for supporting the lower surface formwork to the shaped steel web is performed by welding. There was a problem that fatigue cracks were liable to occur when stress was repeatedly applied to.

  An object of the present invention is to provide a method for constructing a concrete floor slab of a composite floor slab bridge of a hollow type without using a foamed resin material and without welding a support fitting to a web part causing fatigue cracks. It is another object of the present invention to provide a formwork structure for placing concrete used at that time.

  The inventors have intensively studied to solve the above problems. As a result, bolts or bolts can be used instead of the method of supporting the formwork structure for placing concrete to form a concrete slab via a support fitting welded to a T-shaped steel web. Developed the present invention by discovering that if the method is carried out via a beam fixed with a nut, it will not cause residual stress in the web welded part, and thus will not cause fatigue failure of the main girder. It came to.

That is, the present invention relates to a main girder of T-shaped steel arranged in parallel, a bottom steel plate attached between the web lower end surfaces of the main girder, and a concrete floor slab placed on the flange part of the main girder and the upper part of the web. A method for constructing a concrete floor slab of a hollow type composite floor slab bridge in which a space is provided between the concrete floor slab and the bottom steel plate. An angle is attached via a bolt or a bolt and a nut along the length direction, and a beam is suspended between the angle and an angle attached to an opposing web of a main girder arranged adjacent to the angle, Form frame plywood on the beam material, put concrete on the mold frame plywood, harden the concrete, remove the bolts or bolts and nuts, the angle, beam material and formwork Remove plywood While, in a hole remove the bolt or bolts and nuts, again, by inserting the bolt, which is how to build the concrete slab, characterized in that re-tighten the nut.

  The present invention also provides a T-shaped steel main girder arranged in parallel, a bottom steel plate attached between the web lower end surfaces of the main girder, and a concrete floor slab placed on the flange portion of the main girder and the upper portion of the web. And a method for constructing a concrete floor slab of a hollow type composite floor slab bridge provided with a space between the concrete floor slab and the bottom steel plate, wherein a plurality of upper chord members are provided between the main girders arranged in parallel. A diagonal structure is provided, and a beam material is attached between the upper chord members in parallel to the main girder via bolts or bolts and nuts. A formwork plywood is laid on the beam material, and concrete is placed on the formwork plywood. The concrete floor slab construction method is characterized in that, after the concrete is hardened, the bolts or bolts and nuts are removed, and the beam material and the formwork plywood are removed.

  The construction method of the present invention is characterized in that a flat steel plate or a corrugated steel plate is laid and buried instead of the formwork plywood.

  The present invention also provides a T-shaped steel main girder arranged in parallel, a bottom steel plate attached between the web lower end surfaces of the main girder, and a concrete floor embedded in the flange portion of the main girder and the upper portion of the web. A formwork structure used for constructing a concrete floor slab of a hollow type composite floor slab bridge comprising a plate and having a space between the concrete floor slab and a bottom steel plate, wherein the main girder arranged in parallel A plurality of anti-tilt structures having upper chord members provided between them, a beam member mounted between the upper chord members via bolts or bolts and nuts in parallel to the main girder at intervals, and laid on the beam member A formwork structure comprising a formwork plywood, wherein the concrete placed on the formwork plywood is hardened and then removed.

  The formwork structure of the present invention is characterized in that a flat steel plate or a corrugated steel plate is laid and buried in place of the formwork plywood.

  ADVANTAGE OF THE INVENTION According to this invention, the hollow type synthetic floor slab bridge whose span length exceeds 40 m can be constructed | assembled at low cost, without using a foamed resin material. In addition, since the composite floor slab bridge constructed according to the present invention has no welded portion in the T-shaped steel web that is the main girder, there is no risk of causing fatigue failure, and the space portion can be used as an inspection passage. Excellent safety and maintainability.

  A composite floor slab bridge to which the present invention is directed includes a main girder made of T-shaped steels arranged in parallel, a bottom steel plate attached between the web lower end surfaces of the main girder, a flange portion of the main girder, and a web. It is a hollow type composite floor slab bridge comprising a concrete floor slab embedded in concrete and having a space between the concrete floor slab and the bottom steel plate. And, the present invention provides a concrete floor slab of the above-mentioned hollow type composite slab bridge without using a foamed resin material and without requiring the welding of a support fitting to a web part causing fatigue cracks. As a construction method, two methods described below are proposed.

  In the first concrete floor slab construction method according to the present invention, the angle of the main girder (T-section steel) arranged in parallel with the web in the height direction is bolted along the length direction of the T-section steel. It is detachably attached via bolts and nuts (hereinafter also referred to as “bolts”), and the beam material is placed in the length direction of the T-section between this angle and the angle attached to the adjacent T-section. After laying the formwork plywood over the entire area between the main girders on the beam material, placing and hardening the concrete on it, removing the bolts, the angle and beam material, This is a method of removing the formwork plywood.

  1 (a) to 1 (c) illustrate a composite floor slab bridge immediately after concrete placement constructed by the first method of the present invention, and FIG. 1 (a) shows the composite floor slab bridge. FIGS. 1B and 1C are a cross-sectional view taken along line AA ′ of FIG. 1A and a partially enlarged view thereof. Reference numeral 1 in the figure denotes T-shaped steels arranged in parallel at a predetermined interval constituting the main beam, and a bottom steel plate 4 is welded between the lower end surfaces of the T-shaped steel web 2. On the other hand, an angle 6 for supporting a formwork structure for placing concrete is attached by bolts and nuts 5 to an intermediate portion in the height direction of the web 2 of the T-shaped steel 1 (below the flange portion 3). Beam material (square steel pipe) 7 is arranged at a predetermined interval in the length direction of the main girder between the angle 6 and the angle 6 'attached to the opposing web of the adjacent T-shaped steel, which is also arranged in parallel. On the beam material, a formwork (wooden plywood) 8 on the bottom surface of the concrete floor slab is laid on the entire surface of the main girders, and further, an upper portion of the T-shaped steel web 2 and the flange portion 3 are embedded thereon. A concrete 9 is placed. In addition, although not shown in the concrete 9, main reinforcing bars and distribution reinforcing bars are arranged on the top of the T-shaped steel web 2.

A first construction method for a concrete slab according to the present invention will be described with reference to FIG.
To construct a composite floor slab bridge, start with a steel box girder assembled in advance at the factory. In this steel box girder, the T-shaped steel 1 as the main girder is arranged in parallel with an interval of 800 to 1000 mm in parallel with the length of the bridge so that the flange 3 is on top and the web 2 is on the bottom. A bottom steel plate 4 is attached between the web lower end surfaces of the shape steel, or a side plate is attached in parallel to the bottom steel plate and the main girder as required. The bottom steel plate 4 has a role as a lower flange of the main girder (T-shaped steel 1) and is indispensable in terms of strength. The bottom steel plate is usually attached to the lower end of the web by welding, but there is no problem of a decrease in fatigue strength due to this welding. In addition, in composite floor slab bridges with span lengths exceeding 40m, between the main girders arranged in parallel, for the purpose of maintaining the shape, the diagonal and horizontal girders are spaced at a predetermined interval in the main girder length direction. Is usually installed.

  After laying the steel girders between the piers, a formwork structure for constructing concrete slabs by placing concrete is installed between the main girders. In the first method of the present invention, first, an angle 6 serving to support the formwork structure is attached to an intermediate portion of the main girder (T-shaped steel) in the web height direction. The angle needs to be strong enough to support the load of the concrete placed on the upper part of the concrete formwork. For example, the equal side specified in JIS G 3106 “Rolled steel for general structure” A so-called angle such as angle steel or unequal angle angle steel having a side dimension of about 50 to 75 mm can be suitably used. In addition, the attachment of the angle 6 to the web requires fatigue bolting due to residual stress in welding, so it is necessary to use a bolt 5 or the like. For example, a high-strength bolt of about M16 (S10T) is preferably used. Can do. The position of the web in the height direction of the angle varies depending on the cover thickness of the concrete 9 to be cast, but is preferably about 150 mm from the flange portion. Moreover, the space | interval of the volt | bolt etc. which attach an angle should just be about 500-1000 mm, and it is preferable to change suitably according to the weight of concrete. Of course, the attachment of the angle to the web may be performed in advance in a factory.

  Next, between the angle 6 and the angle 6 'attached to the web of the main girder arranged adjacent to each other, the beam material 7 is spanned at an interval of 300 to 500 mm in the length direction of the main girder. Since this beam member 7 needs to keep the amount of deflection due to the load of the concrete to be placed within an allowable range (for example, within 2 mm), it is desirable to use a material having a large cross-sectional secondary moment. It is preferable to use a certain lightweight section steel (JIS G 3350) or a square steel pipe (JIS G 3466). For example, a square steel pipe of 40 mm × 40 mm × 1.6 mmt is suitable as a beam material.

  Next, the formwork plywood 8 which is the lower surface of the concrete placing formwork is laid on the beam material 7 over the entire surface between the adjacent main girders. As this formwork plywood 8, a wooden plywood having a thickness of about 15 mm can be suitably used. After the laying of the mold plywood 8 is completed, the main reinforcing bar and the distribution reinforcing bar are arranged at a position slightly above the T-shaped steel flange 3 in a direction perpendicular to or parallel to the T-shaped steel. Concrete 9 is placed from the upper surface of the steel to a position slightly above the reinforcing bar.

  After the cast concrete 9 is hardened, the bolts 5 used to mount the angle 6 are removed to disassemble the formwork structure, and the space formed between the concrete floor slab and the bottom steel plate is used for disassembly. Remove the formwork member. Since the removed formwork member can be used again for the construction of the formwork structure, it is advantageous in terms of cost. The height of the space formed between the concrete floor slab and the bottom steel plate is 70 cm or more when the span length is 40 m or more, and 1.2 m or more when the span length is 60 m or more. It can be effectively used as a safety inspection passage.

  The formwork structure of the present invention can be buried as it is without disassembling / removing. However, in that case, the wooden formwork plywood may deteriorate with time and may decay and fall. Therefore, instead of the above-mentioned wooden formwork plywood, a deck plate, a flat steel plate, or a corrugated high plate specified in JIS G 3352 may be used as a formwork on the lower surface of the concrete floor slab and buried as it is.

  In the construction method of the first concrete floor slab, since the mounting of the angle supporting the formwork structure for placing the concrete to the T-shaped steel web is carried out by bolts, etc., the residual stress of the web welded portion is reduced. There is no risk of causing fatigue failure. In addition, a bolt hole remains in the web after removing the said bolt and removing a formwork structure. Although this bolt hole causes stress concentration, it does not accompany a large residual stress as in a welded portion. Therefore, even if it is subjected to repeated stress thereafter, it is unlikely to become a starting point of fatigue failure. However, in order to further improve safety, it is preferable to insert a bolt into this bolt hole, tighten it with a nut, and fill the bolt hole, since stress concentration can be reduced.

  Next, the construction method of the second concrete floor slab according to the present invention will be described. In this method, a plurality of anti-tilt structures having upper chord members are provided at predetermined intervals between main girders (T-shaped steel) arranged in parallel, and the main girders are connected between the upper chord members of the anti-tilt structure via bolts. Install the beam material at intervals in parallel, lay the formwork plywood across the entire space between the main girders on the beam material, place concrete on the formwork plywood and harden it, then remove the bolts It is a method of removing beam materials and formwork plywood.

  FIGS. 2 (a) to (c) illustrate a composite floor slab bridge immediately after placing concrete constructed by the second method of the present invention. FIG. 2 (a) shows the composite floor slab bridge. A side view and a partially enlarged view thereof, FIG. 2C is a cross-sectional view taken along the line BB ′ of FIG. 1 in the figure is a T-shaped steel constituting the main girder, and a bottom steel plate 4 is welded between the lower end surfaces of the web 2 of the T-shaped steel 1. The main girder is provided with a plurality of anti-tilt structures 11 having upper chord members (large channel) 12 at intervals in the length direction, and joints 13 are attached to the front and back surfaces of the upper chord members 12. And between this joint 13 and the joint 13 'attached to the upper chord member 12' adjacent to another oppositely inclined structure, a plurality of beam members 14 are provided in parallel to the main beam with a predetermined interval between the main beams. It is attached by bolts 15 and the like, and a formwork (wooden plywood) 8 on the lower surface of the concrete floor slab is laid on the entire surface of the main beam on the beam material, and further on top of the T-shaped steel web 2 Concrete 9 formed by embedding the flange portion 3 is placed. In the concrete 9, although not shown, main reinforcing bars and distribution reinforcing bars are arranged on the top of the T-shaped steel web 2.

  The 2nd construction method of the concrete floor slab which concerns on this invention is demonstrated using FIG. The second construction method is the same as the first construction method in that it starts from bridging steel box girders that have been assembled in the factory in advance between the piers when constructing the composite floor slab bridge. However, in the second method, the steel box girder is provided with a plurality of diagonal structures having an upper chord material at a predetermined interval with respect to the length direction of the main girder. It is necessary that a joint for connecting beam members is attached. The anti-tilt structure and the joint are preferably installed in advance in a factory.

  In the second construction method, the steel box girder is installed between the piers, and then a concrete structure is placed between the main girders for placing concrete to construct a concrete slab. Between the joint 13 attached to the upper chord member 12 and the joint 13 ′ attached to the adjacent upper chord member 12 ′ opposite to each other, a beam member 14 serving to support the formwork structure is attached. Here, FIG. 2 shows an example in which a channel (large) is used as the upper chord member of the diagonal structure, but a thick plate or a small section steel may be used as long as the strength can be secured. Moreover, when a horizontal beam is installed between the main beams arranged in parallel, the above horizontal beam may be used instead of the upper chord material of the diagonal structure. In addition, the method of attaching the joint to the upper chord material is preferably a method of fastening with bolts when removing the formwork structure after placing the concrete. This attachment may be performed at the construction site or in advance at a steel box processing factory.

  In FIG. 2, an example is shown in which a channel (small) is used as the beam member 14 disposed between the upper chord members of the inclined structure. However, the present invention is not limited to this example. However, the beam material used in the second method has a longer span length than the beam material of the first method (the anti-tilt structure is usually installed at intervals of 4 to 6 m), so that the rigidity is higher (cross section). For example, a channel having a dimension of about 150 mm × 75 mm can be suitably used as a beam material. Moreover, the space | interval which arrange | positions a beam material in parallel with a main girder should just be about 300-400 mm, and it is preferable to change suitably according to the weight of concrete. The beam members may be attached after the steel girders are installed on the piers, but it is preferable to assemble the steel girders in advance at the factory from the viewpoint of workability and safety.

  Next, a concrete plywood (wooden plywood) 8 for laying concrete is laid over the entire surface between the main beams arranged in parallel on the beam member 14 and then slightly above the flange of the T-shaped steel. At the position, the main reinforcing bar and the distribution reinforcing bar are arranged perpendicularly or parallel to the T-shaped steel, and then the concrete is placed from the upper surface of the formwork plywood to a position slightly above the reinforcing bar.

  After the cast concrete has hardened, remove the bolts etc. that join the beam and the joint in the same way as the first method, disassemble the formwork structure, and between the concrete floor slab and the bottom steel plate The formwork member is removed using the formed space. Also in the second method of the present invention, the formwork structure can be buried as it is without disassembling / removing, and the deck plate defined in JIS G 3352 is used instead of the wooden formwork plywood. Or a flat steel plate and a corrugated steel plate may be used.

  As described above, the difference between the second construction method and the first construction method is that in the first construction method, the support of the formwork structure for the concrete floor slab is supported on the web of the main girder (T-section steel). The second method supports the above-mentioned formwork structure by using the attached angle and the beam material disposed thereon, while the upper chord material of the diagonal structure installed between the main girders. And it is the point which is performed with the beam material arrange | positioned among them. However, any construction method does not involve welding of the main girder to the web, and therefore has an effect that there is no possibility that the web will be fatigued due to residual stress in the welded portion.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining the composite floor slab bridge immediately after concrete placement constructed | assembled by the method of this invention, (a) is a side view of the said composite floor slab bridge, (b) and (c) are A of (a). It is -A 'line sectional drawing and its partial enlarged view. It is a diagram illustrating a composite floor slab bridge immediately after placing concrete constructed by another method of the present invention, (a) and (b) is a side view of the above composite floor slab bridge and its partially enlarged view, (c) FIG. 4B is a sectional view taken along line BB ′ in FIG.

Explanation of symbols

1: Main girder (T-section steel)
2: Web 3: Flange 4: Bottom steel plate 5: Bolts (bolts or bolts and nuts)
6: Angle 7: Beam material (square steel pipe)
8: Formwork (wooden plywood)
9: Concrete 10: Vertical stiffener 11: Anti-tilt structure 12: Upper chord material of anti-tilt structure (channel size)
13: Fitting 14: Beam material (small channel)
15: Bolts (bolts or bolts and nuts)

Claims (5)

A concrete floor comprising a main girder of T-shaped steel arranged in parallel, a bottom steel plate attached between the web lower end surfaces of the main girder, and a concrete floor slab placed on the flange part of the main girder and the upper part of the web. In the method of constructing a concrete floor slab of a hollow type composite floor slab bridge in which a space is provided between the plate and the bottom steel plate, along the length direction of the main girder in the middle of the web of the main girder in the height direction. Attach the angle via bolts or bolts and nuts and suspend the beam between the angle and the angle attached to the opposing web of the main girder that is placed adjacent to the angle. Laying the formwork plywood, placing concrete on the formwork plywood, after hardening the concrete, removing the bolts or bolts and nuts, removing the angle, beam material and formwork plywood , Above The hole has been removed the object or bolts and nuts, again, by inserting the bolts, how to build a concrete slab, characterized in that re-tighten the nut. A concrete floor comprising a main girder of T-shaped steel arranged in parallel, a bottom steel plate attached between the web lower end surfaces of the main girder, and a concrete floor slab placed on the flange part of the main girder and the upper part of the web. In a method for constructing a concrete floor slab of a hollow type composite floor slab bridge provided with a space between a plate and a bottom steel plate, a plurality of diagonal structures having upper chord members are provided between the main girders arranged in parallel, and A beam is attached between the upper chords in parallel to the main girder via bolts or bolts and nuts, a formwork plywood is laid on the beam, and concrete is placed on the formwork plywood. A method for constructing a concrete floor slab, comprising removing the bolts or bolts and nuts and removing the beam material and formwork plywood after curing. 3. The method for constructing a concrete slab according to claim 1, wherein a flat steel plate or a corrugated steel plate is laid and buried instead of the formwork plywood. The main girder of T-shaped steel arranged in parallel, the bottom steel plate attached between the web lower end faces of the main girder, and the concrete floor slab embedded in the flange part of the main girder and the upper part of the web, A formwork structure used to construct a concrete floor slab of a hollow type composite floor slab bridge in which a space is provided between the floor slab and the bottom steel plate, and the first chord provided between the main girders arranged in parallel It consists of a plurality of anti-tilt structures with materials, beam materials attached between the upper chord materials via bolts or bolts and nuts in parallel to the main girder at intervals, and formwork plywood laid on the beam materials A formwork structure characterized in that the concrete placed on the formwork plywood is hardened and then removed. The formwork structure according to claim 4 , wherein a flat steel plate or a corrugated steel plate is laid and buried instead of the formwork plywood.

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