JP7705339B2 - Precast railing structure - Google Patents

Description

This invention relates to a precast railing structure.

A concrete wall balustrade described in Patent Document 1 below is known as a technology in this field. This concrete wall balustrade is a precast concrete member in which a ground cover is integrally formed with the wall body. A bolt insertion hole and a fastening recess are formed at the lower end of the concrete wall balustrade, and a spring structure fixing bracket is attached to the inner lower end of the ground cover. The embedded rebar of the spring structure fixing bracket is embedded in the concrete wall balustrade without being joined to the rebar of the wall balustrade. The tip of the outer anchor bolt is fastened to the fastening recess, and the tip of the inner anchor bolt is fastened to the protruding fixing portion of the spring structure fixing bracket, and the concrete wall balustrade is installed on the side edge of the concrete floor slab. It is proposed that this concrete wall balustrade will reduce the collision energy when a vehicle collides and transmit it to the concrete floor slab, thereby avoiding damage to the concrete floor slab.

JP 2015-071907 A

However, when a vehicle collides with a wall railing, the wall railing may be damaged, and in this case, it is necessary to prevent fragments of the wall railing caused by the damage from scattering. The present invention aims to provide a precast railing structure that prevents fragments of the wall railing from scattering when a vehicle collides.

The precast balustrade structure of the present invention is a precast balustrade structure that includes a balustrade body made of fiber-reinforced concrete, and a scattering prevention layer for preventing fragments of the balustrade body from scattering is provided along at least the top surface and a portion of the back surface opposite the front surface facing the road.

The scatter suppression layer may be provided along a portion of the front surface of the balustrade main body. The scatter suppression layer may include an aramid fiber mesh sheet embedded along the surface of the balustrade main body. The scatter suppression layer may include a scatter suppression sheet material that covers the surface of the balustrade main body. The back surface of the balustrade main body may be formed with a recess that is recessed toward the front side.

The present invention provides a precast balustrade structure that prevents fragments of the balustrade from scattering due to vehicle collisions.

FIG. 2 is an enlarged cutaway perspective view showing a side edge portion of a road bridge to which the precast railing structures of the first and second embodiments are applied. This is a cross-sectional view showing a section of a precast balustrade block perpendicular to the bridge axis direction. FIG. 2 is a partially enlarged view of a triaxial aramid fiber mesh sheet. FIG. 11 is an enlarged cross-sectional view showing the vicinity of the surface on the back side of a precast balustrade block in the precast balustrade structure of the second embodiment.

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

Figure 2 is a cross-sectional view showing a cross section of the precast balustrade block 3 perpendicular to the bridge axis direction. As can be seen from Figure 1, the precast balustrade block 3 extends in the bridge axis direction with a uniform cross-sectional shape as shown in Figure 2. The precast balustrade block 3 comprises a balustrade main body 7 and a shatter-suppression layer 9 formed to cover the surface of the balustrade main body 7.

The balustrade main body 7 is a molded body that generally has the shape of the entire precast balustrade block 3. Hereinafter, the surface of the balustrade main body 7 that faces the road side of the road bridge 101 will be referred to as the "front 11", and the surface opposite the front 11 will be referred to as the "back 12". As shown in FIG. 2, on the front 11 side of the balustrade main body 7, a haunch portion 7a that protrudes toward the road side at the lower end is formed, and the wall surface extending above the haunch portion 7a is a vertical surface. On the back 12 side of the balustrade main body 7, a recess 15 is formed that is recessed toward the front 11 side. The recess 15 has a generally isosceles trapezoidal cross-sectional shape, with the lower end of the recess 15 being at approximately the same height as the upper end of the haunch portion 7a, and the upper end of the recess 15 being slightly lower than the upper end of the precast balustrade block 3.

The material of the balustrade main body 7 may be, for example, a hydraulic material, such as non-shrink mortar. The material of the balustrade main body 7 may also be high-strength fiber-reinforced mortar. High-strength fiber-reinforced mortar is short-fiber-reinforced mortar with a compressive strength of 120 N/ ^mm2 or more and a tensile strength of 1 N/mm2 or ^more borne by the short fibers.

The material of the balustrade main body 7 may be, for example, fiber-reinforced concrete. The material of the balustrade main body 7 may be ultra-high performance fiber reinforced cement-based composites. Ultra-high performance fiber reinforced cement-based composites are sometimes commonly referred to as "UHPFRC."

UHPFRC is a mixture containing, for example, cement, inorganic powder, aggregate, mixing water, chemical admixtures for concrete, and reinforcing fibers. The cement may be, for example, ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, or low-heat Portland cement. The inorganic powder may be, for example, silica fume, ground granulated blast furnace slag, fly ash, fine silica powder, wollastonite, or an expanding agent.

As an example, the above-mentioned aggregate has a particle size of 5.0 mm or less, an oven-dry density of 2.5 g/cm3 ^or more, a water absorption rate of 3.0% or less, a clay mass amount of 1.0% or less, a fine powder amount of 2.0% or less, and a NaCl content of 0.02% or less. This aggregate is one for which the organic impurity test result for fine aggregate specified in JIS (Japanese Industrial Standards) A 1105 is "light". In addition, this aggregate is one for which the stability of sodium sulfate specified in JIS A 1122 is 10% or less according to the aggregate stability test method, and further, which is classified as Class A in terms of alkali-silica reactivity specified in JIS A 5308 Appendix 1.

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

The UHPFRC constituting the material of the balustrade main body 7 is, for example, a matrix composed of Portland cement, a pozzolan material, a binder containing inorganic powder such as an ettrin guide generating material, aggregate with a particle size of 2.5 mm or less, water, and a water reducing agent. The mix of the material of the balustrade main body 7 is a standard formula mix. The reinforcing fiber may be a mixture of 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, mixed at 1.75 vol. %. The characteristic values of each strength after hardening of the UHPFRC are preferably a compressive strength of 150 N/mm ² or more, a crack initiation strength of 4 N/mm ² , and a tensile strength of 5 N/mm ² .

The standard designated mix ratio for the UHPFRC that constitutes the material of the balustrade main body 7 can be a flow value of 250±20 mm, a ratio of mixing water to binder of 15%, air content of 2.0%, mixing water of 195 kg/ ^m3 , high-performance water reducing agent of 32.2 kg/ ^m3 , and reinforcing fiber of 137.4 kg/ ^m3 (1.75 vol.%).

In this embodiment, UHPFRC is used as the material for the balustrade main body 7. Because UHPFRC itself has sufficient strength, no rebar is embedded in the balustrade main body 7, and the balustrade main body 7 is integrally formed from UHPFRC. Because there is no rebar in the balustrade main body 7, there is no need to consider the thickness of the rebar, and the balustrade main body 7 can be made thinner, for example, by forming the aforementioned recess 15. Furthermore, by making the balustrade main body 7 thinner and eliminating the rebar, the balustrade main body 7 is made lighter, and the precast balustrade block 3 is made lighter.

As described above, since there is no reinforcing bar in the balustrade main body 7, if the balustrade main body 7 is damaged when a vehicle collides with the balustrade 103 of the road bridge 101, fragments of the balustrade main body 7 may easily scatter. Therefore, in order to suppress the scattering of fragments of the balustrade main body 7, the above-mentioned scattering suppression layer 9 is provided. The scattering suppression layer 9 is formed as a surface layer of the precast balustrade block 3 along the surface of the balustrade main body 7. Specifically, the scattering suppression layer 9 is provided along the surface of the balustrade 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 is continuously present 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 shatter-suppressing layer 9 is present continuously over the vertical surface 7b above the haunch portion 7a of the front surface 11, the horizontal top surface 13, and one side surface 15a and bottom surface 15b of the recess 15 of the back surface 12.

For example, the scattering suppression layer 9 in this embodiment is a layer including a triaxial aramid fiber mesh sheet 19 (FIG. 3) embedded along the surface of the balustrade main body 7. As shown in a partially enlarged view in FIG. 3, the triaxial aramid fiber mesh sheet 19 is made by crossing and connecting aramid fibers 19a extending in three axial directions to form a mesh of equilateral triangles with sides of about 40 mm, and further by bonding a large number of sand grains 19b to the surface of the aramid fibers 19a. Such a triaxial aramid fiber mesh sheet 19 is sometimes commonly referred to as a "SAMM sheet (Sandy Aramid Mesh Sheet)". In this case, a commercially available SAMM sheet may be used.

When the precast balustrade block 3 shown in FIG. 2 is manufactured, for example, a SAMM sheet 19 is laid over the area where the shatter-suppressing layer 9 is to be provided on the inner wall surface of a formwork for molding the precast balustrade block 3. Then, UHPFRC is poured into the formwork so as to embed the SAMM sheet 19. After completion, the precast balustrade block 3 has the SAMM sheet 19 embedded in the surface layer. That is, a shatter-suppressing layer 9 including the hardened UHPFRC of 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 balustrade block 3. Then, inside this shatter-suppressing layer 9, a balustrade main body 7 made of UHPFRC is formed.

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

In addition, in the structure of the precast balustrade block 3 of this embodiment, the scattering suppression layer 9 is present around the front surface 11 of the balustrade main body 7, so scattering of debris to the inside of the road bridge 101 (the front surface 11 side of the balustrade main body 7) can also be suppressed. Note that, if scattering of debris to the inside of the road bridge 101 is permitted to a certain extent compared to scattering of debris to the outside of the road bridge 101, the portion of the scattering suppression layer 9 on the front surface 11 side may be omitted. In other words, the scattering 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 balustrade main body 7, and may also be provided in addition to a part of the front surface 11.

In addition, since the material of the balustrade main body 7 is UHPFRC, it is easy to ensure the strength of the precast balustrade block 3, so there is no need to provide vertical reinforcing ribs, for example, in the recess 15. Therefore, the precast balustrade block 3 can be made to have a uniform cross-sectional shape, for example, as shown in Figure 2. And because the precast balustrade 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 balustrade block 3.

Second Embodiment
Next, the second embodiment of the precast balustrade structure of the present invention will be described. FIG. 4 is a cross-sectional view showing an enlarged view of the surface vicinity of the back surface 12 side of the precast balustrade block 33 relating to the precast balustrade structure of this embodiment. The precast balustrade block 33 is provided with a scatter suppression layer 39 instead of the above-mentioned scatter suppression layer 9. Since the configuration other than the scatter suppression layer 39 is the same as that of the first embodiment, the same or equivalent elements are given the same reference numerals in the drawings, and duplicated explanations are omitted. As shown in FIG. 2, the cross-sectional view of the entire precast balustrade block 33 is generally similar to the cross-sectional view of the precast balustrade block 3 of the first embodiment. That is, the scatter suppression layer 39, like the scatter suppression layer 9, exists on the vertical surface 7b above the haunch portion 7a of the front surface 11 of the balustrade main body 7, the horizontal upper surface 13, and one side surface 15a and bottom surface 15b of the recess 15 of the back surface 12.

As shown in FIG. 4, the shatter-suppression layer 39 includes a reinforcing fiber sheet material 41 (shatter-suppression sheet material) that covers the surface of the railing main body 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 made by weaving aramid fibers into a sheet, a carbon fiber sheet made by weaving carbon fibers into a sheet, or a glass fiber sheet made by weaving glass fibers into a sheet, is used. In this case, a commercially available aramid fiber sheet, carbon fiber sheet, or glass fiber sheet may be used as the reinforcing fiber sheet material 41.

The method for manufacturing this precast balustrade block 33 is as follows: first, a thin plate-shaped fiber reinforced plastics (FRP) section 38 is made by solidifying reinforcing fiber sheet material 41 with epoxy resin, phenolic resin, or the like, and is manufactured in the same shape as the scattering suppression layer 39. This fiber reinforced plastic section 38 can be manufactured using any known fiber reinforced plastic manufacturing method. Then, this thin plate-shaped fiber reinforced plastic section 38 is installed on the inner wall surface of the formwork for the precast balustrade block 3, the inner surface of the fiber reinforced plastic section 38 (the surface that contacts the UHPFRC to be cast) is roughened, and the UHPFRC is cast into the formwork.

In the completed precast balustrade block 33, the fiber-reinforced resin part 38 is bonded to the surface of the balustrade main body part 7 made of UHPFRC. That is, as shown in FIG. 4, a scattering suppression layer 39 composed of a thin plate-shaped fiber-reinforced resin part 38 is formed on the surface of the balustrade main body part 7. As described above, the inner surface of the fiber-reinforced resin part 38 is roughened before the UHPFRC is poured, so that a good bond is obtained between the balustrade main body part 7 and the scattering suppression layer 39. The resin layer 43 of the scattering suppression layer 39 is made of epoxy resin, phenolic resin, etc. in the fiber-reinforced resin part 38, and the reinforcing fiber sheet material 41 is embedded in this resin layer 43.

In another method for producing the precast balustrade block 33, UHPFRC is first poured into a formwork to produce the balustrade main body 7. Then, the reinforcing fiber sheet material 41 is attached to the surface of the balustrade main body 7 over the area where the scattering suppression layer 39 is to be provided. As a specific method for attachment, a primer is first applied to the surface of the balustrade main body 7, and the reinforcing fiber sheet material 41 is temporarily attached onto the primer. Then, adhesive is further applied onto the reinforcing fiber sheet material 41 on the primer, so that the adhesive permeates the reinforcing fiber sheet material 41 and the reinforcing fiber sheet material 41 is embedded in the adhesive. When the adhesive hardens, a resin layer 43 made of the primer and adhesive is formed. As a result, as shown in FIG. 4, a scattering suppression layer 39 is formed on the surface of the balustrade main body 7, the scattering suppression layer 39 comprising a reinforcing fiber sheet material 41 that covers the surface of the balustrade main body 7 and a resin layer 43 in which the reinforcing fiber sheet material 41 is embedded.

The above-described structure of the precast balustrade block 33 also provides the same effect as the precast balustrade block 3 of the first embodiment. In the event of a vehicle collision, the scattering of fragments is suppressed by the scattering suppression layer 39. Furthermore, the reinforcing fiber sheet material 41 of the scattering suppression layer 39 not only has the function of suppressing scattering of fragments, but also functions as a tensile reinforcement material for the precast balustrade block 33. Therefore, the scattering suppression layer 39 also contributes to improving the strength and impact resistance of the precast balustrade block 33. As a result, the structure of the precast balustrade block 33 equipped with the scattering suppression layer 39 allows the balustrade main body 7 to be further thinned, and the precast balustrade block 33 to be lighter.

The present invention can be implemented in various forms, including the above-described embodiment, with various modifications and improvements based on the knowledge of those skilled in the art. It is also possible to configure modified examples by utilizing the technical matters described in the above-described embodiment. The configurations of each embodiment, etc. may be used in appropriate combination.

For example, in the manufacturing method of the precast balustrade 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 cast into the formwork. If the reinforcing fiber sheet material 41 and the balustrade main body 7 can be joined in this way, the shatter-suppression layer 39 can be formed without using a resin part (adhesive) that is relatively susceptible to deterioration by ultraviolet rays, which is preferable from the viewpoint of extending the life of the precast balustrade block 33. In addition, the shatter-suppression layer 9 in the first embodiment is made of a triaxial aramid fiber mesh sheet 19 and UHPFRC, and does not include a resin part that is relatively susceptible to deterioration by ultraviolet rays, which is preferable from the viewpoint of extending the life of the precast balustrade block 3.

1...Precast balustrade structure, 3, 33...Precast balustrade block, 7...Balustrade main body, 9, 39...Scattering prevention layer, 11...Front, 12...Back, 13...Top, 15...Recess, 19...Triaxial aramid fiber mesh sheet, 41...Reinforcing fiber sheet material (scattering prevention sheet material).

Claims (4)

A precast balustrade structure having a balustrade body made of fiber-reinforced concrete without embedded reinforcing bars,
A scattering prevention layer for preventing scattering of fragments of the balustrade main body is provided so as to be continuously connected over at least a part of the front surface of the balustrade main body facing the road, the upper surface, and a part of the back surface opposite the front surface ,
The shatterproof layer is
An aramid fiber mesh sheet installed on the surface of the railing main body;
and hardened fiber-reinforced concrete poured along the surface of the balustrade main body so as to embed the aramid fiber mesh sheet . The shatterproof layer is
The precast balustrade structure according to claim 1 , further comprising a front surface of the balustrade body, the front surface being provided along a portion of the front surface. The shatterproof layer is
The precast balustrade structure according to claim 1 or 2, further comprising a shatter-suppression sheet material covering the surface of the balustrade main body portion. The precast balustrade structure according to any one of claims 1 to 3 , wherein a recess is formed on the rear surface of the balustrade main body portion, the recess being recessed toward the front surface side.

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