JP2005171645A - Reinforcing method of overhanging beam section of reinforced concrete viaduct - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spraying reinforced material having the same inorganic system as that of a concrete skeleton capable of holding the integrity with the skeleton, obtaining the bending reinforced effective like in the case tension reinforcement is increased by using a fiber reinforced cement composite material of the reinforced material having at least traction yield strength 3.6 (MPa) and 0.5% or above of end elongation, reducing a reinforced cost for enabling the influence of self-weight to lighten, thinning down the increased thickness since area of reinforcement is decreased and increasing durability against an external deterioration factor since the width of flexural crack becomes very small. <P>SOLUTION: The roughening treatment is applied to the surface of concrete of the lower face of an overhanging beam section 22 of a reinforced concrete viaduct 21 so that the interfacial bond strength can become at least 1.5 N/mm<SP>2</SP>. Alternatively, the existing reinforcement 14 is chipped, and the high ductile fiber reinforced cement composite material (high ductile FRC material) 15 having at least traction yield strength 3.6 (MPa) and 0.5% or above of end elongation is sprayed thereon. Accordingly, maintenance expenses can be reduced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for reinforcing an overhanging beam portion of a reinforced concrete viaduct that is a railway bridge.

  For example, in the case of a reinforced concrete viaduct, when installing a new soundproof wall with a high height on the overhanging beam part, it becomes a problem that the existing section of the overhanging beam part cannot secure the use performance against the wind load during a storm. .

  In such a case, conventionally, a cement-based repair material is used to reinforce by the lower surface thickening method.

  The following Patent Document 1 is a method of reinforcing a floor plate, not an overhanging beam portion, but the bottom surface of the floor plate 2 that requires repair as shown in FIG. 6 (concrete faces downward at the joint between the floor plate 2 and the plate garter 1). The necessary number of fixing holes 4 are drilled in the swelled part), a required amount of shear key 5 is driven into the lower surface of the floor board 2, and both ends of reinforcing bars 6 such as reinforcing bars or FRP rods are inserted into the fixing holes 4. Then, the grout material 7 is injected into the gap between the fixing hole 4 and the reinforcing bar 6 and fixed.

If the fixing length is not sufficient, the mechanical fixing device 8 is used in combination. A formwork is installed below the reinforcing bars 6 and concrete or mortar is injected between the lower surface of the floor board 2 and the formwork.

JP-A-8-218326

  In the thickening method as in Patent Document 1, since the amount of necessary reinforcing bars is increased, there is a drawback that the thickness of the entire casing is increased.

  It should be noted that bending cracks are generated in the overhanging beam portion due to the action of wind load or the like, so that it is necessary to block the penetration of external deterioration factors.

  For this, surface coating material has been applied in the past, but for surface coating material, bending cracks penetrate through the surface coating material by repeatedly receiving a load, so periodic repairs are required. This has led to an increase in maintenance costs.

  Furthermore, as a surface protector, the surface coating material is a resin paint-based or polymer-based material, and has the advantage of high material strength and shielding properties. However, the material is expensive, and has an elastic coefficient and thermal expansion coefficient. Since it is greatly different from the concrete of the existing frame, there is a drawback that when external force is repeatedly applied, the external force causes separation between the existing part and peeling off easily.

  In particular, the resin coating is often weak against ultraviolet rays, and the followability is poor because the resin characteristic peculiar to organic and the concrete characteristic peculiar to inorganic are different as described above.

  The object of the present invention is to eliminate the inconveniences of the conventional examples, and the reinforcing material is the same inorganic material as the concrete case, can maintain the integrity with the case, and further reduce the thickness and increase the service life. The purpose of this project is to provide a method to reinforce the overhanging beam section of a reinforced concrete viaduct that can reduce the maintenance cost as much as possible.

In order to achieve the above object, the present invention according to claim 1 is characterized in that the surface of the concrete on the lower surface of the overhanging beam portion of the reinforced concrete viaduct is subjected to a roughening treatment such that the adhesion strength of the interface is 1.5 N / mm ² or more. The gist of the present invention is to carry out or to lift an existing rebar and spray a fiber-reinforced cement composite material having a tensile yield strength of 2.0 (MPa) or more and an ultimate elongation of 0.5% or more.

  According to the first aspect of the present invention, by applying a fiber reinforced cement composite material having a tensile yield strength of 2.0 (MPa) or more and an ultimate elongation of 0.5% or more, it is possible to bear a tensile stress in the spray reinforcement portion. .

  In other words, ordinary concrete and cement-based repair materials are not able to consider the tensile performance in the design because they break at a tensile strain of about 0.02% as soon as cracks occur. On the other hand, the fiber-reinforced cement composite material to be sprayed exhibits a so-called pseudo-strain hardening property that the tensile stress increases after the occurrence of cracking, and is more than 5 times the yield strain (about 0.2%) of the reinforcing bar. It has excellent tensile strain performance that it does not fall below the crack strength even in tensile strain. By having this characteristic, a tensile load can be expected in the design.

  Also, it is not necessary to install anchors etc. for integration with existing parts by roughening the surface of the concrete and spraying fiber reinforced cement composite material (high toughness FRC material) on it. Thus, the workability can be improved.

This invention according to claim 2 is characterized in that the fiber-reinforced cement composite material is
The following [F1] PVA (Polyvinyl Alcohol) short fibers are added to the formulation matrix of [M1], exceeding 1 to 3 Vol. The high-toughness fiber-reinforced cement composite material (high-toughness FRC material) blended three-dimensionally randomly or two-dimensionally with a blending amount of%.
[M1]
-Water binder ratio (W / C) 25% or more-Sand binder weight ratio (S / C) is 1.5 or less (including 0)
・ Maximum particle size of fine aggregate 0.8mm or less, average particle size 0.4mm or less ・ Unit water volume 250kg / m ³ or more and 400kg / m ³ or less ・ Air volume at the time of kneading 3.5% or more and 20% or less ・ High performance AE water reducing agent less than an amount 30kg / ^{m 3} [F1]
・ Fiber diameter 50μm or less ・ Fiber length: 5-20mm
・ Fiber tensile strength: 1500 MPa to 2400 MPa or less

  According to the second aspect of the present invention, the high-toughness fiber-reinforced cement composite material (high-toughness FRC material) has a tensile strain exceeding 1% due to its formulation matrix and fiber blending amount. Direction) and a crack dispersion type fracture phenomenon in which a large number of cracks (multi-cracks) occur in a direction substantially perpendicular to the direction.

  Therefore, cracks can be reliably controlled to a very small width, and by using such a high toughness fiber reinforced cement composite material (high toughness FRC material) as a surface protector, frame concrete due to bending load or fatigue load Even if cracks occur, it is possible to realize a surface protection work that maintains the function.

  As described above, the reinforcing method of the overhanging beam portion of the reinforced concrete viaduct of the present invention is that the reinforcing material to be sprayed is the same inorganic system as the concrete frame, and can maintain the integrity with the frame, and this reinforcing material has the tensile yield strength By using a fiber reinforced cement composite material having 2.0 (MPa) or more and an ultimate elongation of 0.5% or more, the bending reinforcement effect can be obtained in the same manner as when the tensile reinforcement is increased.

  In addition, since the amount of reinforcing bars is reduced compared to the case of using normal concrete, the thickness of the increased thickness is reduced and the influence of its own weight can be reduced, so that the reinforcement cost can be reduced.

  Furthermore, since the bending crack width is very small, durability against external deterioration factors is improved. Maintenance costs can be reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view showing an embodiment of a method for reinforcing a projecting beam portion 22 of a reinforced concrete viaduct 21 according to the present invention. In FIG. 1, reference numeral 10 denotes a bridge pier arranged in parallel in the direction perpendicular to the bridge axis and arranged at intervals in the bridge axis direction. , 11 is a beam for connecting piers 10 parallel to the direction perpendicular to the bridge axis, 12 is a girder for connecting adjacent piers 10 in the direction of the bridge axis, 13 is a slab on which a railroad track is laid or becomes a road, There is an overhanging beam portion 22 as an extension portion of the slab 13.

  The overhanging beam portion 22 bears a large live load such as a railroad bridge beam and receives severe bending fatigue.

The concrete surface on the lower surface of the overhanging beam portion 22 of the reinforced concrete viaduct 21 is subjected to a roughening treatment such that the adhesion strength of the interface is 1.5 N / mm ² or more, or the existing rebar 14 is lifted. A high-toughness fiber-reinforced cement composite material (high-toughness FRC material) 15 having a tensile yield strength of 2.0 (MPa) or more, an ultimate elongation of 0.5% or more, and preferably 1% or more is sprayed. In addition, you may make it arrange | position a reinforcing bar or FRP as needed.

  The roughening treatment is performed by high-pressure cleaning, sand blasting, sander, or the like, and for example, unevenness of ± 1 mm or less is applied.

This high-toughness fiber-reinforced cement composite material (high-toughness FRC material) 15 has a crack (crack) that exhibits a tensile strain (final elongation) of 0.5% or more, preferably 1% or more in a tensile test of a cured product on the age of 28 days. ) A dispersion type PVA (Polyvinyl Alcohol) short fiber of [F1] described below was added to the preparation matrix of [M1] by 1 to 3 Vol. % Blending amount was three-dimensional random or two-dimensional random.
[M1]
-Water binder ratio (W / C) 25% or more-Sand binder weight ratio (S / C) is 1.5 or less (including 0)
・ Maximum particle size of fine aggregate 0.8mm or less, average particle size 0.4mm or less ・ Unit water volume 250kg / m ³ or more and 400kg / m ³ or less ・ Air volume 3% or more and 20% or less when kneaded ・ High performance AE water reduction 30 dosage
kg / ^m less than ³ [F1]
・ Fiber diameter 50μm or less ・ Fiber length: 5-20mm
・ Fiber tensile strength: 1500 MPa to 2400 MPa or less

  The matters specified by the high-toughness fiber-reinforced cement composite material (high-toughness FRC material) 15 will be further described below. In the formulation of [M1], when the water binder ratio of the matrix is less than 25%, the elastic modulus and fracture toughness of the matrix of the fiber of [F1] are high and multi-cracks do not occur, and a tensile strain of 0.5% or more ( (Eventual growth) is unlikely to occur. The water / binding material ratio specifically means water / (cement + admixture).

  Examples of admixtures that can be used include blast furnace slag fine powder, fly ash, silica fumes, and fine limestone powder.

  When a part of the cement is replaced with fly ash, the replacement ratio is 40% or less (including 0) in terms of weight ratio with respect to the total bonding amount. Fly ash can improve fluidity by the ball bearing effect because the particles are spherical. Since the blast furnace slag fine powder has angular particles, such an effect cannot be expected.

  Moreover, even if it is this fiber compounding quantity, if the length of a fiber is less than 5 mm, since a multicrack will not generate | occur | produce, it is necessary to use the thing of length 5mm or more. However, even when a length longer than 20 mm is used, multi-cracking does not occur with the above blending amount. Therefore, the length of the fiber of [F1] needs to be 5 to 20 mm, preferably 8 to 15 mm.

  As the type of cement, normal Portland cement (manufactured by Taiheiyo Cement Co., Ltd.) and low heat Portland cement (manufactured by Taiheiyo Cement Co., Ltd.) can be used.

  As the fiber, PVA fiber (vinylon fiber) having the above-mentioned diameter, length and tensile strength was used.

  Each material was kneaded, the table flow and the box filling height were measured, and the fresh properties were evaluated by observing the degree of material separation in these tests. In addition, as a characteristic after curing, it was subjected to a tensile test on the 28th day of the material age, and the strain amount (final elongation amount) (%) at the maximum tensile stress value in the tensile stress-strain curve was obtained to determine whether or not multi-crack occurred. Examined.

  The tensile strain (final elongation) refers to a strain amount (final elongation amount) (%) at a maximum tensile stress value in a stress-strain curve obtained by a tensile test of a cured product having a material age of 28 days or more.

  Fig. 2 shows the test method. Actually, the tensile test in a test specimen (test specimen) on the 28th day of material age (for example, a test specimen having a cross section of 30 mm x 13 mm is subjected to a tensile test in an 80 mm test section). It is represented by strain (ultimate elongation) (%). The ultimate elongation is designed to be equal to or less than the value of the lower confidence interval estimated with a 5 percent risk using the mean and standard deviation calculated from multiple measurements of the breaking elongation measured by the tensile test method. Characteristic value.

3 and 4 show the results of the tensile test. FIG. 4 is an enlarged view of a part of FIG. The straight trapezoidal portion is the analysis value. Examples of material setting values that can be set in the structural design as can be seen from this figure are as shown in Table 1 below. The design values are 35.5 or more in compressive strength (MPa), 2.0 or more in tensile yield strength (MPa), The Young's modulus (× 10 ⁴ MPa) is 1.5 or more and the ultimate elongation is 0.5% or more.

  With ordinary concrete and cement-based repair materials, as soon as cracks occur, they will break at a tensile strain of about 0.02%, so the tensile performance cannot be considered in the design. On the other hand, the high-toughness fiber-reinforced cement composite material (high-toughness FRC material) 15 exhibits a so-called pseudo-strain hardening characteristic in which the tensile stress increases after the occurrence of cracks as shown in FIGS. It has excellent tensile strain performance that it does not fall below the cracking strength even at a tensile strain of 5 times or more the yield strain (about 0.2%) of the reinforcing bar. By having this characteristic, a tensile load can be expected in the design.

  The tensile strain of 0.5% or more means that a crack dispersion type fracture phenomenon in which a large number of cracks (multi-cracks) are generated in a direction substantially perpendicular to the loading direction (stress direction).

  FIG. 3 shows a spraying system in which the high-toughness fiber-reinforced cement composite material (high-toughness FRC material) 15 is kneaded and formed by a mixer 16 and received by a hopper 17, and a pressure-resistant hose 19 is pumped by a pump 18. Then, it sprays with the spray gun 20 which mixes compressed air.

  The high-toughness fiber-reinforced cement composite material (high-toughness FRC material) 15 has a high ability to restrain cracks caused by fibers, prevents the cracks from expanding, and generates the next cracks. Subsequently, since many new micro cracks are generated one after another, even if an apparently very large tensile strain occurs, it can withstand the load. Further, the crack can be controlled to a minute width (for example, 0.05 mm or less).

It is explanatory drawing which shows one Embodiment of the reinforcement construction method of the overhanging beam part of the reinforced concrete viaduct of this invention. It is explanatory drawing of a test method. It is the graph which showed the result of the tension test by the dumbbell-type test body shown in FIG. FIG. 4 is an enlarged view of a portion where the horizontal axis in FIG. 3 is 0 to 10,000. It is a system diagram of spraying. It is a vertical side view which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Plate gutter 2 ... Floor board 4 ... Fixing hole 5 ... Shear key 6 ... Reinforcing bar 7 ... Grout material 8 ... Mechanical fixing tool 10 ... Pier 11 ... Beam 12 ... Girder 13 ... Slab 14 ... Existing rebar 15 ... High toughness Fiber reinforced cement composite (high toughness FRC material)
16 ... Mixer 17 ... Hopper 18 ... Pump 19 ... Pressure hose 20 ... Spray gun 21 ... Reinforced concrete viaduct 22 ... Overhang beam

Claims (2)

The surface of the concrete on the underside of the reinforced concrete viaduct overhanging the surface of the concrete is roughened so that the bond strength at the interface is 1.5 N / mm ² or more, or the existing rebar is pulled out and the tensile yield strength is applied here. Reinforcement method of reinforced concrete overhanging beam, characterized by spraying fiber reinforced cement composite material with 2.0 (MPa) or more and ultimate elongation of 0.5% or more. Fiber reinforced cement composite material
The following [F1] PVA (Polyvinyl Alcohol) short fibers are added to the formulation matrix of [M1], exceeding 1 to 3 Vol. The reinforcing method for a reinforced concrete overhanging beam portion according to claim 1, which is a high-toughness fiber-reinforced cement composite material (high-toughness FRC material) blended three-dimensionally randomly or two-dimensionally in a blending amount of 2%.
[M1]
-Water binder ratio (W / C) 25% or more-Sand binder weight ratio (S / C) is 1.5 or less (including 0)
・ Maximum particle size of fine aggregate 0.8mm or less, average particle size 0.4mm or less ・ Unit water volume 250kg / m ³ or more and 400kg / m ³ or less ・ Air volume at the time of kneading 3.5% or more and 20% or less ・ High performance AE water reducing agent Amount 30
kg / ^m less than ³ [F1]
・ Fiber diameter 50μm or less ・ Fiber length 5-20mm
・ Fiber tensile strength: 1500 MPa to 2400 MPa or less

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