Method for preventing projection of PC steel rod

Abstract

To provide a method for preventing projection of a PC steel rod in which a reinforced part can be inspected by making the reinforcing structure transparent.SOLUTION: A method for preventing the projection of PC steel rods comprises steps of applying or sticking a surface protective material (2) for preventing scattering to a first region (S2) including the vicinity of the tip of a PC steel rod (20) buried on a surface (12) of a concrete structure, arranging a transparent polycarbonate plate (3) from above the surface protective material so as to cover a second region (S1) including the vicinity of the tip of the PC steel rod buried, and fixing the polycarbonate plate to the surface of the concrete structure by an anchor (4) in a plurality of places.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for preventing protrusion of a PC steel rod. [Background technology]

[0002] Prestressed concrete (PC) bridges, which are characterized by being lightweight and strong, are sometimes used on expressways and other roads. PC bridges are bridges constructed with PC, and the tensile stress that occurs in the concrete due to load is countered by applying compressive stress to the concrete using PC steel bars. The PC steel bars are arranged vertically and horizontally (in the direction of the bridge axis and perpendicular to the bridge axis).

[0003] It is known to provide a reinforcing structure on the surface of a concrete structure to prevent the PC steel rod from rusting or corroding and breaking, causing the introduced tension to be suddenly released, leading to the PC steel rod protruding from the side or bottom of the bridge girder and the falling of the PC steel rod itself or pieces of concrete (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-227792 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the reinforcement structure described in Patent Document 1, a receiving member such as a stainless steel mesh sheet is attached to the concrete surface with a fiber-reinforced sheet, so that the concrete surface cannot be inspected after the reinforcement structure is installed.

[0006] The present invention aims to provide a method for preventing the protrusion of PC steel bars by making the reinforcing structure transparent, thereby enabling inspection of the reinforced portion. [Means for solving the problem]

[0007] One aspect of the present invention relates to a method for preventing PC steel rods from protruding from a concrete structure in which prestress is applied based on the PC steel rods being embedded in a tensioned state, and is characterized by comprising the steps of applying or attaching a transparent surface protective material for preventing scattering to a first area including the vicinity of the tip of the buried PC steel rod on the surface of the concrete structure, placing a transparent polycarbonate plate on top of the transparent surface protective material to cover a second area including the vicinity of the tip of the buried PC steel rod, and fixing the polycarbonate plate to the surface of the concrete structure with anchors at multiple points.

[0008] In the method for preventing protrusion of a PC steel bar according to one aspect of the present invention, the first region is preferably larger than the second region.

[0009] In one aspect of the present invention, in the method for preventing protrusion of a PC steel bar, the polycarbonate plate preferably has a thickness of 12 mm or more and 15 mm or less.

[0010] In the method for preventing protrusion of PC steel bars according to one aspect of the present invention, it is preferable that the surface protective material is selected from one or more of epoxy resin, urethane resin, acrylic resin, methacrylic resin, polyester sheet, and glass fiber sheet.

[0011] In the method for preventing protrusion of a PC steel rod according to one aspect of the present invention, the anchor is preferably arranged so as to surround the vicinity of the tip of the buried PC steel rod. Effect of the Invention

[0012] The method for preventing protrusion of PC steel bars according to the present invention has a simple configuration and makes it possible to prevent the PC steel bars themselves from falling and concrete pieces from flying off. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing a state in which a method for preventing protrusion of PC steel bars is applied to a concrete structure to which prestress is applied. [Diagram 2] 1A is a cross-sectional view of the protrusion prevention mechanism, and FIG. 1B is a plan view of the protrusion prevention mechanism. [Diagram 3] (a) shows another method of arranging anchors, and (b) shows yet another method of arranging anchors. [Figure 4] FIG. 1 is a diagram showing an overview of a test device for performing an evaluation test. [Diagram 5] 1 is a table showing test results. [Figure 6] 1A shows an image after the evaluation test in the case of Example 1, and FIG. 1B shows an image after the evaluation test in the case of Example 2. FIG. [Figure 7] 1A shows an image after the evaluation test in the case of Example 3, and FIG. 1B shows an image after the evaluation test in the case of Example 4. FIG. [Figure 8] 11 shows an image after the evaluation test in the case of Example 5. [Figure 9] 1A shows an image after the evaluation test in the case of Comparative Example 1, and FIG. 1B shows an image after the evaluation test in the case of Comparative Example 2. FIG. [Figure 10] 1A shows an image after the evaluation test in the case of Comparative Example 3, and FIG. 1B shows an image after the evaluation test in the case of Comparative Example 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, various embodiments of the present invention will be described with reference to the drawings. It should be noted that the technical scope of the present invention is not limited to these embodiments, but covers the inventions described in the claims and their equivalents.

[0015] FIG. 1 is a schematic diagram showing a state in which a method for preventing protrusion of PC steel bars is applied to a prestressed concrete structure.

[0016] In Fig. 1, a cross section of a PC bridge 10 is shown as a concrete structure to which prestress is applied. When the PC bridge 10 is used for an expressway or the like, vehicles will run on the top surface 11 of the PC bridge 10. Also, in Fig. 1, a PC steel bar 20 is arranged vertically in one girder of the PC bridge 10. Note that although only one PC steel bar is shown in Fig. 1, multiple PC steel bars may actually be arranged.

[0017] As shown in FIG. 1, the PC steel rods 20 arranged in a direction substantially perpendicular to the upper surface 11 are referred to as vertical PC steel rods, and the PC steel rods arranged in a direction parallel to the upper surface 11 are referred to as horizontal PC steel rods.

[0018] An anti-protrusion mechanism 1 is placed near the tip of the PC steel bar 20, on the underside 12 side of the PC bridge 10. Although not clearly shown in Fig. 1, the PC bridge 10 is often fixed to the top of another road, etc., by other piers, etc. Therefore, the anti-protrusion mechanism 1 prevents the PC steel bar 20 from rusting or corroding and breaking, causing the introduced tension to be suddenly released and causing the vertical PC steel bar 20 itself or pieces of concrete to fall.

[0019] Fig. 2(a) is a cross-sectional view of the extrusion prevention mechanism 1, and corresponds to an enlarged view of the area A surrounded by a dashed line in Fig. 1. Fig. 2(b) is a plan view of the extrusion prevention mechanism 1 as seen from the underside 12 of the PC bridge 10.

[0020] As shown in Figure 2(a), the protrusion prevention mechanism 1 is composed of a surface protection material 2 applied or affixed to the underside 12 of the PC bridge 10, a transparent polycarbonate plate 3 arranged to cover the upper surface of the surface protection material 2, and a number of anchors 4 that fix the polycarbonate plate 3 to the underside 12 of the PC bridge 10.

[0021] The surface protective material 2 is applied or affixed to the underside 12 of the PC bridge 10 to prevent concrete pieces from scattering when the tip of the PC steel bar 20 protrudes from the underside 12 of the PC bridge 10. As the surface protective material 2, one or more of epoxy resin, urethane resin, acrylic resin, methacrylic resin, polyester sheet, and glass fiber sheet can be selected. All of the resins are transparent, allowing the surface condition of the concrete structure to be visually observed after the surface protective material is applied or affixed.

[0022] As shown in Figure 2(a), the depth B from the tip of the PC steel rod 20 placed inside the PC bridge 10 to the underside 12 of the PC bridge 10 is called the "cover" and is set to 15 to 30 mm. The thickness C of the transparent polycarbonate plate 3 is set to 12 to 15 mm. Because the polycarbonate plate 3 is transparent, it becomes easy to discover whether the PC steel rod is about to protrude when inspecting the underside of the PC bridge 10.

[0023] As shown in FIG. 2(b), a polycarbonate plate 3 is fixed to the underside 12 of a PC bridge 10 by six anchors 4 so that the tip of a PC steel bar 20 is located at the intersection of diagonal lines. The application or attachment area S1 (first area) of the surface protection material 2 is set to be larger than the surface area S2 (second area) of the polycarbonate plate 3. In one example, S1 is set to 740×600 mm, and S2 is set to 500×500 mm, but is not limited to these. By making S1>S2, scattering of concrete pieces can be better prevented.

[0024] FIG. 3(a) shows another method for arranging the anchors 4, and FIG. 3(b) shows yet another method for arranging the anchors 4.

[0025] As shown in Figures 2(b), 3(a) and 3(b), the anchors 4 that secure the polycarbonate plate 3 need only be arranged around the tip of the PC steel rod 20, and it is preferable to secure it with six or more anchors, but it may also be possible to secure it with eight or more anchors.

[0026] FIG. 4 is a diagram showing an outline of a test device for carrying out an evaluation test.

[0027] The testing apparatus 30 is composed of a fixed base 33 for fixing the test protrusion prevention mechanism 1' fixed to a concrete block 31 of thickness D to a specified floor or the like, a weight 34, and a drop path structure 35 for dropping the weight 34 accurately onto the center of the test protrusion prevention mechanism 1'.

[0028] The weight 34 is allowed to naturally fall in the direction of arrow E from a predetermined height on the side of the concrete block 31 opposite to the side to which the test protrusion prevention mechanism 1' is fixed, by a fall control mechanism (not shown). The weight 34 is set so that the impact generated when it is naturally dropped from the predetermined height is just the same as the impact that the PC steel rod 20 protruding from the bridge girder gives to the underside 12 of the PC bridge 10 when the introduced tension is suddenly released. Specifically, it is set so that the 200 kg weight 34 is dropped from a height of 2 m, causing an impact of 3920 (J).

[0029] A 50 mm diameter core 32 is drilled into the center of the concrete block 31 from the side opposite to the side where the test protrusion prevention mechanism 1' is fixed. A 15 mm cover is reproduced by leaving 15 mm of the tip F of the 50 mm diameter core 32. In an actual PC bridge 10, the cover is 15 mm to 30 mm, but since the impact of the 15 mm is greater, in the evaluation test, the tip F of the 50 mm diameter core 32 was left 15 mm.

[0030] In the evaluation tests, various types of test anti-protrusion mechanisms 1' were fixed to a concrete block 31 (material: ordinary Portland cement, strength: 40 N / mm2, slump: 12 ± 2.5 cm, air pressure: 4.5 ± 1.5%, maximum dimension of coarse bone material: 20 mm or less) measuring 1000 × 740 × 150 mm (thickness D = 150 mm) and experiments were conducted.

[0031] Regardless of the thickness, a transparent polycarbonate plate measuring 500 x 500 mm was used, and the surface protective material was applied or stuck within an area of ​​740 x 600 mm. The weight 34 was dropped at approximately the center of the diagonal of the polycarbonate plate and at approximately the center of the diagonal of the area where the surface protective material was applied or stuck.

[0032] The evaluation device shown in FIG. 4 can be considered a test device that can accommodate PC steel bars arranged in the vertical and horizontal directions (the direction of the bridge axis and the direction perpendicular to the bridge axis).

[0033] FIG. 5 is a table showing the results of the evaluation test using the evaluation device shown in FIG.

[0034] In the test protrusion prevention mechanisms 1' of Examples 1 to 3, a transparent polycarbonate plate with a thickness of 15 mm was used, which was fixed to a concrete block 31 with six anchors 4 as shown in Fig. 2(b), and transparent materials A, B, and C were used as surface protection materials. Material A was a polyester sheet attached to the surface of the concrete block 31 with water-based epoxy resin, material B was coated with urethane resin, and material C was a glass fiber sheet attached to the surface of the concrete block 31 with methacrylic resin.

[0035] In Examples 1 to 3, even when weight 34 was dropped, swelling was observed in the polycarbonate plate, but it did not crack, and furthermore, pieces of concrete block 31 did not scatter, and the evaluation results were pass. Fig. 6(a) shows an image of the surface of the polycarbonate plate after weight 34 was dropped in Example 1, Fig. 6(b) shows an image of the surface of the polycarbonate plate after weight 34 was dropped in Example 2, and Fig. 7(a) shows an image of the surface of the polycarbonate plate after weight 34 was dropped in Example 3.

[0036] In the test protrusion prevention mechanisms 1' of Examples 4 to 6, a transparent polycarbonate plate having a thickness of 12 mm was used and fixed to a concrete block 31 with six anchors 4 as shown in Figure 2(b), and transparent materials A, B and C were used as surface protection materials, respectively.

[0037] In Examples 4 to 6, even when weight 34 was dropped, swelling was observed in the polycarbonate plate, but it did not crack, and furthermore, pieces of concrete block 31 did not scatter, and the evaluation results were pass. Fig. 7(b) shows an image of the surface of the polycarbonate plate after weight 34 was dropped in Example 4, and Fig. 8 shows an image of the surface of the polycarbonate plate after weight 34 was dropped in Example 5.

[0038] In the test protrusion prevention mechanism 1' of Comparative Example 1, a transparent polycarbonate plate with a thickness of 15 mm was used and fixed to a concrete block 31 with six anchors 4 as shown in FIG. 2(b), but no surface protection material was used. Even when the weight 34 was dropped, the polycarbonate plate bulged but did not break. However, pieces of the concrete block 31 were scattered, and the result was a failure. FIG. 9(a) shows an image of the surface of the polycarbonate plate after the weight 34 of Comparative Example 1 was dropped. As shown in FIG. 9(a), pieces of the concrete block 31 are scattered.

[0039] In the test protrusion prevention mechanism 1' of Comparative Example 2, a transparent polycarbonate plate with a thickness of 15 mm was used and fixed to a concrete block 31 with eight anchors 4 as shown in FIG. 3(b), but no surface protection material was used. Even when the weight 34 was dropped, the polycarbonate plate bulged but did not break. However, pieces of the concrete block 31 were scattered, and the result was a failure. FIG. 9(b) shows an image of the surface of the polycarbonate plate after the weight 34 of Comparative Example 2 was dropped. As shown in FIG. 9(b), pieces of the concrete block 31 are scattered.

[0040] In the test protrusion prevention mechanism 1' of Comparative Example 3, a transparent polycarbonate plate with a thickness of 15 mm was used and fixed to a concrete block 31 with six anchors 4 as shown in FIG. 2(b). In addition, a transparent material A was used as a surface protection material, but it was not applied to the surface of the concrete block 31. Instead, the polycarbonate plate was fixed to the concrete block 31, and then the transparent material A was applied from above the polycarbonate plate. When the weight 34 was dropped, the polycarbonate plate was penetrated, and pieces of the concrete block 31 were scattered, resulting in a failure. FIG. 10(a) shows an image of the surface of the polycarbonate plate after the weight 34 of Comparative Example 3 was dropped. As shown in FIG. 10(a), the polycarbonate plate is penetrated.

[0041] In the test protrusion prevention mechanism 1' of Comparative Example 4, a glass fiber sheet was used instead of a polycarbonate plate. Also, no surface protection material was used. When the weight 34 was dropped, the glass fiber sheet was penetrated, and pieces of the concrete block 31 were scattered, resulting in a failure. Figure 10(b) shows an image of the surface of the glass fiber sheet after the weight 34 of Comparative Example 4 was dropped. As shown in Figure 10(b), the glass fiber sheet has peeled off.

[0042] The evaluation test shown in Figure 5 revealed that by applying or sticking the surface protection material to the concrete surface and then fixing a 12 to 15 mm thick transparent polycarbonate plate to the concrete surface with anchors, it was possible to effectively prevent the PC steel rods (placed vertically and horizontally) from protruding and concrete pieces from scattering.

[0043] It should be understood that those skilled in the art can make various changes, substitutions and alterations thereto without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0044] 1 Extrusion prevention mechanism 2 Surface protection material 3 Polycarbonate plate 4. Anchor 20 Vertical PC steel rod

Claims

1. A method for preventing protrusion of a PC steel rod from a concrete structure to which prestress is applied based on embedding the PC steel rod in a tensioned state, comprising: A transparent surface protective material for preventing scattering is applied or attached to a first region including the vicinity of the tip of the embedded PC steel bar on the surface of the concrete structure; A transparent polycarbonate plate is placed on the transparent surface protective material so as to cover a second region including the vicinity of the tip of the embedded PC steel rod; The polycarbonate plate is fixed to the surface of the concrete structure by anchors at a plurality of points. A method for preventing protrusion of a PC steel rod, comprising the steps of:

2. The method for preventing protrusion of a PC steel rod according to claim 1 , wherein the first region is wider than the second region.

3. The method for preventing protrusion of a PC steel rod according to claim 1 or 2, wherein the thickness of the polycarbonate plate is 12 mm or more and 15 mm or less.

4. The method for preventing protrusion of PC steel rods according to claim 1 or 2, wherein the surface protective material is selected from one or more of epoxy resin, urethane resin, acrylic resin, methacrylic resin, polyester sheet, and glass fiber sheet.

5. 3. The method for preventing protrusion of a PC steel rod according to claim 1 or 2, wherein the anchor is arranged so as to surround the vicinity of the tip of the buried PC steel rod.

Images