Precast parapet structure

Abstract

To provide a precast balustrade structure that suppresses scattering of fragments of a wall balustrade due to collision of a vehicle.SOLUTION: A precast balustrade structure 1 includes a balustrade body part 7 made of fiber-reinforced concrete, wherein a scattering suppression layer 9 for suppressing scattering of broken pieces of the balustrade body part 7 is provided along at least an upper surface 13 and a back surface 12 opposite to a front surface 11 facing a roadside among surfaces of the balustrade body part 7.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a precast fence structure.

Background Art

[0002] Conventionally, as a technology in this field, a concrete wall fence described in Patent Document 1 below is known. This concrete wall fence is a precast concrete member in which a ground covering portion is integrally formed on a wall main body portion. A bolt insertion hole and a fastening recess are formed at a lower end portion of the concrete wall fence, and a spring structure fixing fitting is attached to an inner lower end portion of the ground covering portion. The embedded reinforcing bar of the spring structure fixing fitting is embedded in the concrete wall fence without being joined to the reinforcing bar of the wall fence. When the tip of an outer anchor bolt is fastened to the fastening recess and the tip of an inner anchor bolt is fastened to the protruding fixing portion of the spring structure fixing fitting, the concrete wall fence is installed at a side edge portion of a concrete floor slab. It has been proposed that when a vehicle collides, the impact energy is alleviated by the concrete wall fence and transmitted to the concrete floor slab, thereby avoiding damage to the concrete floor slab.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when a vehicle collides with the wall fence, the wall fence may be damaged. In this case, it is necessary to suppress the scattering of fragments of the damaged wall fence. An object of the present invention is to provide a precast fence structure that suppresses the scattering of fragments of a wall fence due to a vehicle collision.

Means for Solving the Problems

[0005] The precast guardrail structure of the present invention is a precast guardrail structure including a guardrail main body made of fiber-reinforced concrete, and a scattering suppression layer for suppressing the scattering of fragments of the guardrail main body is provided along at least a part of the upper surface of the guardrail main body and a part of the back surface opposite to the front surface facing the road side.

[0006] The scattering suppression layer may be provided along a part of the front surface of the guardrail main body. The scattering suppression layer may include an aramid fiber mesh sheet embedded along the surface of the guardrail main body. The scattering suppression layer may include a scattering suppression sheet material covering the surface of the guardrail main body. A recess may be formed on the back surface of the guardrail main body, recessed toward the front surface side.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a precast guardrail structure that suppresses the scattering of fragments of a wall guardrail due to a vehicle collision.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0009] (First Embodiment) Hereinafter, a first embodiment of a precast railing structure according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a broken perspective view showing an enlarged side edge portion of a road bridge 101 to which the precast railing structure 1 of the present embodiment is applied. The railing portion 103 of the road bridge 101 is configured by connecting a plurality of precast railing blocks 3 manufactured in a factory in the bridge axis direction. Each precast railing block 3 is joined to the upper surface of the side edge portion of the floor slab 105 of the road bridge 101 and rises vertically upward from the side edge portion. This precast railing block 3 constitutes the precast railing structure 1 according to the present embodiment.

[0010] FIG. 2 is a cross-sectional view showing a cross-section of the precast railing block 3 orthogonal to the bridge axis direction. As understood from FIG. 1, the precast railing block 3 extends in the bridge axis direction in a shape having a uniform cross-section shown in FIG. 2. The precast railing block 3 includes a railing main body portion 7 and a scattering suppression layer 9 formed so as to cover the surface of the railing main body portion 7.

[0011] The railing main body portion 7 is a molded body generally presenting the shape of the entire precast railing block 3. Hereinafter, among the surfaces of the railing main body portion 7, the surface facing the road side of the road bridge 101 is referred to as the "front surface 11", and the surface opposite to the front surface 11 is referred to as the "rear surface 12". As shown in FIG. 2, on the front surface 11 side of the railing main body portion 7, a hunch portion 7a protruding toward the road side is formed at the lower end portion, and the wall surface extending above the hunch portion 7a is a vertical surface. On the rear surface 12 side of the railing main body portion 7, a recess 15 recessed toward the front surface 11 side is formed. The recess 15 generally has an isosceles trapezoidal cross-sectional shape, the lower end of the recess 15 is at a position approximately the same height as the upper end of the hunch portion 7a, and the upper end of the recess 15 is at a position slightly lower than the upper end of the precast railing block 3.

[0012] As the material of the railing main body portion 7, for example, a hydraulic material is adopted, for example, non-shrinking mortar is adopted. Further, the material of the railing main body portion 7 may be high-strength fiber-reinforced mortar. High-strength fiber-reinforced mortar means that the compressive strength is 120 N / mm 2 As described above, the tensile strength borne by the short fibers is 1 N / mm2 It is the above short fiber reinforced mortar.

[0013] Also, as the material of the railing main body 7, for example, fiber reinforced concrete may be adopted. The material of the railing main body 7 may be an ultra-high performance fiber reinforced cement-based composite material (Ultra High Performance Fiber Reinforced cement-based Composites). The ultra-high performance fiber reinforced cement-based composite material may generally be abbreviated as "UHPFRC" in some cases.

[0014] UHPFRC is, for example, a mixture containing cement, inorganic powder, aggregate, mixing water, chemical admixture for concrete, and reinforcing fiber. The above cement is, for example, ordinary Portland cement, early strength Portland cement, medium heat Portland cement, or low heat Portland cement. The inorganic powder includes silica fume, blast furnace slag fine powder, fly ash, silica fine powder, wollastonite, expansive material, etc.

[0015] As an example, the aforementioned aggregate has a particle size of 5.0 mm or less, an absolute dry density of 2.5 g / cm 3 or more, a water absorption rate of 3.0% or less, a viscosity lump amount of 1.0% or less, a fine powder content of 2.0% or less, an NaCl content of 0.02% or less. This aggregate is one for which the test result of the organic impurities of the fine aggregate specified in JIS (Japanese Industrial Standards: Japanese Industrial Standards) A 1105 is "light". Also, this aggregate has a stability of 10% or less according to the stability test method of the aggregate with sodium sulfate specified in JIS A 1122, and is an aggregate for which the classification according to the alkali-silica reactivity specified in Annex 1 of JIS A 5308 is Class A.

[0016] The above kneaded water is, for example, kneaded water other than the recovered water specified in JSCE - B 101 - 2013. The above chemical admixture for concrete is a high - performance water - reducing agent specified in JIS A 6204. Also, the above reinforcing fiber has a diameter of 0.1 - 0.25 mm, a length of 10 - 24 mm, and a tensile strength of 2×10N 3 / mm 2 or more. The above reinforcing fiber may be, for example, steel fiber, high - strength aramid fiber, or carbon fiber.

[0017] The UHPFRC constituting the material of the barrier main body 7 is composed of, for example, a binder added with inorganic powders such as Portland cement, pozzolanic material, and ettringite - forming system material, aggregate with a particle size of 2.5 mm or less, water, and a water - reducing agent. The mixing ratio of the material of the barrier main body 7 is the standard mixing ratio. Also, the reinforcing fiber is steel fiber with a diameter of 0.2 mm, a length of 15 mm (manufacturing error less than ±2 mm), and a tensile strength of 2×10 3 N / mm 2 or more, and 1.75 vol.% of a mixture of the above may be incorporated. Also, the characteristic values of each strength after the hardening of UHPFRC are preferably a compressive strength of 150 N / mm 2 or more, a cracking strength of 4 N / mm 2 , and a tensile strength of 5 N / mm 2 .

[0018] The standard mixing ratio of the UHPFRC constituting the material of the barrier main body 7 is a flow value of 250±20 mm, the ratio of kneaded water to the binder is 15%, the air content is 2.0%, the kneaded water is 195 kg / m 3 , the high - performance water - reducing agent is 32.2 kg / m 3 , and the reinforcing fiber is 137.4 kg / m 3 (1.75 vol.%).

[0019] In this embodiment, it is assumed that UHPFRC is used as the material of the guardrail main body 7. Since UHPFRC itself has sufficient strength, no reinforcing bars are embedded in the guardrail main body 7, and the guardrail main body 7 is integrally formed of UHPFRC. Since there are no reinforcing bars in the guardrail main body 7 in this way, it is not necessary to consider the cover thickness of the reinforcing bars, etc., and for example, the guardrail main body 7 can be thinned by forming the aforementioned recess 15. Then, by thinning the guardrail main body 7 and omitting the reinforcing bars, the guardrail main body 7 is lightened, and the precast guardrail block 3 is lightened.

[0020] Since there are no reinforcing bars in the guardrail main body 7 as described above, if the guardrail main body 7 is damaged when a vehicle collides with the guardrail section 103 of the road bridge 101, there is a possibility that the fragments of the guardrail main body 7 will scatter easily. Therefore, in order to suppress the scattering of the fragments of the guardrail main body 7, the aforementioned scattering suppression layer 9 is provided. The scattering suppression layer 9 is formed as the surface layer of the precast guardrail block 3 along the surface of the guardrail main body 7. Specifically, the scattering suppression layer 9 is provided along the surface of the guardrail main body 7 so as to be continuously connected across the front surface 11, the upper surface 13, and the back surface 12. In this embodiment, as shown in FIG. 2, the scattering suppression layer 9 continuously exists across the upper part of the front surface 11, the horizontal upper surface 13, and the upper part of the back surface 12. More specifically, the scattering suppression layer 9 continuously exists across the vertical surface 7b above the hunch part 7a of the front surface 11, the horizontal upper surface 13, and one side surface 15a and the bottom surface 15b of the recess 15 of the back surface 12.

[0021] For example, the splash suppression layer 9 in the present embodiment is a layer including a triaxial aramid fiber mesh sheet 19 (Fig. 3) embedded along the surface of the guardrail main body 7. The triaxial aramid fiber mesh sheet 19 is formed by intersecting and connecting aramid fibers 19a extending in three axial directions so as to form a regular triangular mesh with a side length of about 40 mm, as partially enlarged and shown in Fig. 3. Further, a large number of sand grains 19b are adhered to the surface of the aramid fibers 19a. Such a triaxial aramid fiber mesh sheet 19 is sometimes generally abbreviated as "SAMM sheet (Sandy Aramid Mesh Sheet)". Here, a commercially available SAMM sheet may be adopted.

[0022] When the precast guardrail block 3 shown in Fig. 2 is manufactured, for example, on the inner wall surface of the mold for molding the precast guardrail block 3, the SAMM sheet 19 is stretched over the area where the splash suppression layer 9 is provided. Then, UHPFRC is placed in the mold so as to embed the SAMM sheet 19. In the completed precast guardrail block 3, the SAMM sheet 19 is embedded in the surface layer. That is, a splash suppression layer 9 including the hardened UHPFRC in the surface layer and the SAMM sheet 19 embedded in the UHPFRC of the surface layer is formed on the surface layer of the precast guardrail block 3. And inside this splash suppression layer 9, a guardrail main body 7 made of UHPFRC is formed.

[0023] According to the structure of the precast guardrail block 3 of the present embodiment described above, even if the guardrail main body 7 is damaged when a vehicle collides with the guardrail portion 103, the scattering of fragments is suppressed by the SAMM sheet 19 of the splash suppression layer 9. Here, on the outside of the road bridge 101 (the back surface 12 side of the guardrail main body 7), there are often other roads below the road bridge 101, so there is a particularly high need to suppress the scattering of fragments to the outside of the road bridge 101. In contrast, according to the structure of the precast guardrail block 3 of the present embodiment, since the splash suppression layer 9 exists on the upper surface 13 and the back surface 12 side of the guardrail main body 7, the fragments scattered to the back surface 12 side by the collision of the vehicle are suppressed, and as a result, the scattering of fragments to the outside of the road bridge 101 can be suppressed.

[0024] Furthermore, in the structure of the precast guardrail block 3 of the present embodiment, since the splash suppression layer 9 also exists around and wraps around the front surface 11 of the guardrail main body 7, it is possible to suppress the scattering of fragments to the inside of the road bridge 101 (the front surface 11 side of the guardrail main body 7). Note that, when the scattering of fragments to the inside of the road bridge 101 is allowed to some extent compared to the scattering of fragments to the outside of the road bridge 101, the portion of the splash suppression layer 9 on the front surface 11 side may be omitted. That is, the splash suppression layer 9 is provided along at least a part of the upper surface 13 and a part of the back surface 12 of the surface of the guardrail main body 7, and may be further provided in addition to a part of the front surface 11.

[0025] In addition, since the material of the guardrail main body 7 is UHPFRC and it is easy to ensure the strength of the precast guardrail block 3, for example, it is not necessary to provide vertical reinforcing ribs or the like in the concave portion 15. Therefore, the precast guardrail block 3 can be formed into a shape having a uniform cross section as shown in FIG. 2, for example. And since the precast guardrail block 3 has a uniform cross section as described above, it is easy to install the SAMM sheet 19 along the surface of this precast guardrail block 3.

[0026] (Second Embodiment) Next, a second embodiment of the precast guardrail structure of the present invention will be described. FIG. 4 is a cross-sectional view showing an enlarged view near the surface on the back surface 12 side of the precast guardrail block 33 according to the precast guardrail structure of the present embodiment. The precast guardrail block 33 includes a splash suppression layer 39 instead of the splash suppression layer 9 described above. Since the configuration other than this splash suppression layer 39 is the same as that of the first embodiment, the same or equivalent elements are denoted by the same reference numerals in the drawings, and redundant descriptions are omitted. The cross-sectional view of the entire precast guardrail block 33 is generally the same as the cross-sectional view of the precast guardrail block 3 of the first embodiment as shown in FIG. 2. That is, the splash suppression layer 39 exists on the vertical surface 7b above the hunch portion 7a among the front surfaces 11 of the guardrail main body 7, the horizontal upper surface 13, and one side surface 15a and the bottom surface 15b of the concave portion 15 among the back surfaces 12, similar to the splash suppression layer 9.

[0027] As shown in FIG. 4, the scattering suppression layer 39 includes a reinforcing fiber sheet material 41 (scattering suppression sheet material) that covers the surface of the fence main body portion 7, and a resin layer 43 in which the reinforcing fiber sheet material 41 is embedded. As the reinforcing fiber sheet material 41, for example, an aramid fiber sheet formed by weaving aramid fibers into a sheet shape, a carbon fiber sheet formed by weaving carbon fibers into a sheet shape, or a glass fiber sheet formed by weaving glass fibers into a sheet shape is adopted. In this case, as the reinforcing fiber sheet material 41, a commercially available aramid fiber sheet, carbon fiber sheet, or glass fiber sheet may be adopted.

[0028] As a method for manufacturing this precast fence block 33, first, a thin plate-shaped fiber-reinforced resin (FRP: Fiber Reinforced Plastics) portion 38 obtained by hardening the reinforcing fiber sheet material 41 with an epoxy resin, a phenolic resin, or the like is manufactured in the same shape as the scattering suppression layer 39. As a method for manufacturing this fiber-reinforced resin portion 38, a known method for manufacturing a fiber-reinforced resin may be used. Then, this thin plate-shaped fiber-reinforced resin portion 38 is installed on the inner wall surface of the mold of the precast fence block 3, the inner surface of the fiber-reinforced resin portion 38 (the surface in contact with the UHPFRC to be placed) is roughened, and UHPFRC is placed in the mold.

[0029] In the completed precast fence block 33, the fiber-reinforced resin portion 38 is joined to the surface of the fence main body portion 7 made of UHPFRC. That is, as shown in FIG. 4, a scattering suppression layer 39 composed of the thin plate-shaped fiber-reinforced resin portion 38 is formed on the surface of the fence main body portion 7. Since the inner surface of the fiber-reinforced resin portion 38 is roughened before the UHPFRC is placed as described above, good joining between the fence main body portion 7 and the scattering suppression layer 39 can be obtained. The resin layer 43 of the scattering suppression layer 39 is made of an epoxy resin, a phenolic resin, or the like in the fiber-reinforced resin portion 38, and the reinforcing fiber sheet material 41 is in a state of being embedded in this resin layer 43.

[0030] As another manufacturing method of the precast guardrail block 33, first, UHPFRC is placed in a formwork to manufacture the guardrail main body portion 7. Then, a reinforcing fiber sheet material 41 is adhered to the surface of the guardrail main body portion 7 over the area where the scattering suppression layer 39 is to be provided. As a specific method of adhesion, first, a primer is applied to the surface of the guardrail main body portion 7, and the reinforcing fiber sheet material 41 is temporarily adhered onto this primer. Then, an adhesive is further applied onto the reinforcing fiber sheet material 41 on the primer. The adhesive impregnates the reinforcing fiber sheet material 41 and the reinforcing fiber sheet material 41 is buried in the adhesive. When this adhesive cures, a resin layer 43 composed of the above primer and adhesive is formed. Thereby, as shown in FIG. 4, a scattering suppression layer 39 including a reinforcing fiber sheet material 41 covering the surface of the guardrail main body portion 7 and a resin layer 43 embedding the reinforcing fiber sheet material 41 is formed on the surface of the guardrail main body portion 7.

[0031] Also, with the structure of the precast guardrail block 33 as described above, the same operational effects as those of the precast guardrail block 3 of the first embodiment can be obtained. When a vehicle collides, the scattering of fragments is suppressed by the scattering suppression layer 39. Further, the reinforcing fiber sheet material 41 of the scattering suppression layer 39 not only has a function of suppressing the scattering of fragments but also functions as a tensile reinforcing material of the precast guardrail block 33. Therefore, the scattering suppression layer 39 also contributes to the improvement of the strength and impact resistance of the precast guardrail block 33. As a result, according to the structure of the precast guardrail block 33 provided with the scattering suppression layer 39, further thinning of the guardrail main body portion 7 becomes possible, and weight reduction of the precast guardrail block 33 becomes possible.

[0032] The present invention can be implemented in various forms with various changes and improvements based on the knowledge of those skilled in the art, starting from the above-described embodiments. Also, it is possible to configure a modification of the embodiment by using the technical matters described in the above-described embodiments. The configurations of each embodiment and the like may be appropriately combined and used.

[0033] For example, in the method of manufacturing the precast fence block 33 in the second embodiment, only the reinforcing fiber sheet material 41 may be installed on the inner wall surface of the formwork, and UHPFRC may be placed in the formwork. If the bonding between the reinforcing fiber sheet material 41 and the fence main body 7 can be achieved in this way, the scattering suppression layer 39 can be formed without using a resin part (adhesive) that is relatively easily deteriorated by ultraviolet rays. Therefore, it is preferable from the viewpoint of extending the service life of the precast fence block 33. Further, the scattering suppression layer 9 in the first embodiment is composed of a triaxial aramid fiber mesh sheet 19 and UHPFRC and does not contain a resin part that is relatively easily deteriorated by ultraviolet rays. Therefore, it is preferable from the viewpoint of extending the service life of the precast fence block 3.

Explanation of reference numerals

[0034] 1... precast fence structure, 3, 33... precast fence block, 7... fence main body, 9, 39... scattering suppression layer, 11... front surface, 12... back surface, 13... upper surface, 15... recess, 19... triaxial aramid fiber mesh sheet, 41... reinforcing fiber sheet material (scattering suppression sheet material).

Claims

A precast guardrail structure comprising a guardrail main body made of fiber-reinforced concrete without embedded steel bars, wherein a scattering suppression layer for suppressing scattering of fragments of the guardrail main body is provided so as to be continuously connected across at least a part of the front surface facing the road side, the upper surface, and a part of the back surface opposite to the front surface, of the surface of the guardrail main body; the scattering suppression layer includes an aramid fiber mesh sheet installed on the surface of the guardrail main body, and fiber-reinforced concrete after casting along the surface of the guardrail main body so as to embed the aramid fiber mesh sheet.

2. The scattering suppression layer is further provided along a part of the front surface of the surface of the guardrail main body. The precast guardrail structure according to claim 1.

3. The scattering suppression layer includes a sheet material for scattering suppression that covers the surface of the guardrail main body. The precast guardrail structure according to claim 1 or 2.

4. A concave portion recessed toward the front surface side is formed on the back surface of the guardrail main body. The precast guardrail structure according to any one of claims 1 to 3.

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