Support posts for vehicle guardrails

Abstract

To provide a guard fence support post which brings about excellent effects in the sense that even if it is used in the work of replacing the deck of a road on a bridge, there is no need for temporary re-installation, and even if it is used on roads with narrow median strips, it can be used for both guard fences installed on both sides.SOLUTION: In a guard fence support post 1 which includes a base plate 11 fixed to a slab 7 as a foundation and a pipe body 21 erected from the base plate 11, and can absorb through plastic deformation of the tube body 21 the impact load applied to the tube body 21, the tube body 21 is square shaped, and a pair of notch holes 31A, 31B are respectively provided at the four corners 21e of the lower end 21a of the rectangular tube body 21 with intervals 33 in the tube axis direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a support column for a protective fence used for protective fences for roads, bridges, etc.

Background Art

[0002] Conventionally, for protective fences for roads, bridges, etc., it has been required to have a structure that can absorb the impact load during a collision of a vehicle or the like and minimize the damage of an accident while ensuring the safety of passengers and the like. Regarding the support column for a protective fence used for a protective fence, it has also been required to have a structure suitable for such requirements.

[0003] For example, as the performance required for a square support column for a protective fence in recent years, when a load test is performed, in the SB type (standard support column interval of 1.0 m), it is required that the ultimate support force is 3 kN or more and that the impact load can be absorbed without breaking until the displacement amount reaches 300 mm.

[0004] In order to satisfy such required performance, simply adjusting the wall thickness, material, etc. of the support column for a protective fence to increase the rigidity will cause early breakage of the welded joint between the base plate and the pipe body constituting the support column for a protective fence, making it difficult to satisfy the required performance. For this reason, conventionally, various devices have been proposed for the structure of the support column for a protective fence so as to satisfy the required performance.

[0005] For example, Patent Document 1 discloses a support column for a protective fence in which the lower end of the support column member and the base plate are not welded with a center stiffener (interrupting rib) in order to have good energy absorption and eliminate the worry of the support column member breaking near the stiffener.

[0006] However, the conventional guardrail posts disclosed in Patent Document 1 have a problem in that the load in the initial stage of post deformation is low, and they cannot guide the colliding vehicle in a safe direction early on. Furthermore, the conventional guardrail posts disclosed in Patent Document 1 require an additional center stiffener member in addition to the post material, which leads to problems such as increased material costs, increased costs due to increased welding work, and deterioration of workability due to increased weight.

[0007] In contrast, Patent Document 2 discloses a protective fence support post which has a pair of notches formed at an interval in the direction of the pipe axis at the lower end opposite to the side of the pipe that receives the impact load, and two sets of notches are formed at an interval in the direction of the pipe circumference.

[0008] The conventional guardrail support posts disclosed in Patent Document 2 have excellent shock absorption effects, such as being able to achieve a maximum load capacity equivalent to or greater than that when reinforcing plates are joined, even without reinforcing plates, in the initial deformation stage when the amount of post displacement is small, further improving the load capacity in the final deformation stage, and also enabling a reduction in the number of members used.

[0009] However, even with the protective fence posts disclosed in Patent Document 2, which have excellent shock absorption effects, for example, when they are installed as temporary fixtures to prevent vehicles from falling through the opening after the deck slab is removed during deck slab replacement work on a four-lane road on a bridge, there is a problem in that in order to exert their effect, it is necessary to reverse and temporarily reinstall the protective fence after the work on one half of the cross-section is completed and the work on the other half of the cross-section is carried out.

[0010] Furthermore, the protective fence support posts disclosed in Patent Document 2, which possess excellent shock absorption effects, have the problem that, in cases such as roads with narrow median strips, their excellent shock absorption effect can only be applied to one of the protective fences installed on both sides.

[0011] Furthermore, Patent Document 3 discloses a tubular support column in which the pipe body and base plate are welded together, and a long notch is formed in the direction of the pipe axis near the base plate on the back side facing the fence material installation area, in order to have excellent impact energy absorption capacity, ensure aesthetic appeal, and reduce manufacturing costs. However, it has the same problems as the support column for protective fences disclosed in Patent Document 2. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 11-117245 [Patent Document 2] Japanese Patent Publication No. 2011-127408 [Patent Document 3] Japanese Patent Publication No. 2008-202393 [Overview of the project] [Problems that the invention aims to solve]

[0013] Therefore, the present invention was devised in view of the above-mentioned problems, and its objective is to provide a support post for a guardrail that can be used in bridge deck replacement work without requiring the hassle of temporary reinstallation, and can exert its excellent shock absorption effect on both sides of the guardrail even when used on roads with narrow median strips. [Means for solving the problem]

[0014] The vehicle guardrail support post according to the first invention comprises a base plate fixed to a foundation and a pipe erected from the base plate, and is capable of guiding a colliding vehicle in a safe direction without breaking up to a predetermined displacement amount, while absorbing the impact load applied to the pipe by the plastic deformation of the pipe, wherein the pipe is rectangular and each of the four corners of the lower end of the rectangular pipe is provided with a set of notched holes formed at intervals in the direction of the pipe axis. The set of notches has a diameter of 25 mm or more and 48 mm or less, and the spacing between them is set to 10 mm or more, and the height of the lower end of the lower notch is set to 10 mm or more from the upper surface of the base plate. It is characterized by being present.

[0015] According to the second invention For vehicles In the first invention, the pair of notch holes of the support column for the guardrail are through holes penetrating the pipe body, which is characterized in that.

[0016] According to the third invention For vehicles In the first or second invention, the pair of notch holes of the support column for the guardrail are characterized in that the height positions of the lower notch hole and the upper notch hole are substantially the same respectively.

[0017] According to the fourth invention For vehicles In any one of the first to third inventions, the pair of notch holes of the support column for the guardrail are characterized in that the diameter of the lower notch hole and the diameter of the upper notch hole are substantially the same or the upper notch hole is larger.

Effect of the invention

[0020] For the first invention to the 4 According to the invention For vehicles According to the support column for the guardrail, if a cross member is installed on either the front side or the back side of the pipe body, it can be used for the floor slab replacement work of the road on the bridge without the need for the labor of reinstalling the temporary structure. Even when used for a road with a narrow median strip or the like, for both sides of the guardrail provided with cross members on both the front side and the back side of the pipe body, a maximum load-bearing capacity equivalent to or greater than that when a reinforcing plate is joined can be obtained at the initial stage of deformation with a small amount of column displacement, and the load-bearing capacity at the final stage of deformation can be further improved. Furthermore, the number of members used can be reduced, and an excellent impact absorption effect and the like can be exerted. Furthermore, according to the vehicle guardrail posts of the first to fourth inventions, the diameter of a set of notched holes is set to 25 mm or more and 48 mm or less. For example, in the SB type (standard post spacing of 1.5 m), it has been confirmed in demonstration tests that the ultimate bearing capacity is 30 kN or more and that it can absorb impact loads without breaking until the displacement reaches 300 mm. Furthermore, in the vehicle guardrail support posts according to the first to fourth inventions, the spacing between a pair of notched holes is set to 10 mm or more, and the height position of the lower end of the lower notched hole is set to 10 mm or more from the upper surface of the base plate, and it has been confirmed in demonstration tests that this facilitates processing.

[0021] In particular, according to the second invention For vehicles According to the support column for the guardrail, since the pair of notch holes are through holes penetrating the pipe body, they can be easily formed by punching or the like.

[0022] In particular, according to the third invention For vehiclesAccording to the support column for the protective fence, in a set of notch holes, the height positions of the lower notch hole and the upper notch hole are substantially the same respectively, so the performance on the front side and the back side of the pipe body can be easily made substantially the same.

[0023] Particularly, according to the For vehicles support column for the protective fence according to the fourth invention, in a set of notch holes, the diameter of the lower notch hole and the diameter of the upper notch hole are substantially the same or the upper notch hole is larger. Therefore, in the case of being substantially the same, an excellent shock absorption effect can be exerted, and in the case of the upper notch hole being larger, it has been confirmed by the demonstration test that a more excellent shock absorption effect can be exerted.

Brief Description of the Drawings

[0026] [Figure 1] FIG. 1(a) is a plan view showing a schematic configuration of a protective fence assembled using the support column for the protective fence according to an embodiment of the present invention, and FIG. 1(b) is a side view of FIG. 1(a). [Figure 2] FIG. 2(a) is a perspective view showing a schematic configuration of the support column for the protective fence according to an embodiment of the present invention, FIG. 2(b) is a cross-sectional view taken along the line A-A in FIG. 2(a), and FIG. 2(c) is a cross-sectional view taken along the line B-B in FIG. 2(a). [Figure 3] FIG. 3 is a graph showing the relationship between the ultimate support force in the support column for the protective fence and the ultimate bending moment of the horizontal member. [Figure 4] FIGS. 4(a) to 4(c) are graphs showing the relationship between the displacement and the load in the support column for the protective fence when the diameter of the notch hole in the support column for the protective fence is changed respectively. [Figure 5] FIG. 5 is a graph showing the relationship between the diameter of the notch hole in the support column for the protective fence and the displacement at the time of fracture. [Figure 6] FIG. 6 is a diagram schematically showing the stress distribution applied to the lower end portion of the pipe body in the initial stage of deformation of the support column for the protective fence according to an embodiment of the present invention. [Figure 7] FIG. 7 is a diagram schematically showing the deformed state of the lower end portion of the pipe body together with its stress distribution after the initial stage of deformation of the support column for the protective fence according to an embodiment of the present invention. [Figure 8] Figure 8 is a schematic diagram showing the deformation state of a protective fence support post according to an embodiment of the present invention at the final stage of deformation, along with its stress distribution. [Modes for carrying out the invention]

[0027] The embodiments illustrated below, applying the present invention, will be described with reference to the drawings.

[0028] [Embodiment] Figure 1(a) is a plan view showing the schematic configuration of a protective fence assembled using protective fence posts according to an embodiment of the present invention, and Figure 1(b) is a side view of Figure 2(a). Figure 2(a) is a perspective view showing the schematic configuration of protective fence posts according to an embodiment of the present invention, Figure 2(b) is a cross-sectional view taken along line AA in Figure 2(a), and Figure 2(c) is a cross-sectional view taken along line BB in Figure 2(a).

[0029] As shown in Figures 1(a) and 1(b), the guardrail 3 according to this embodiment comprises a plurality of guardrail support posts 1 erected at intervals from the road deck 7 on the bridge, which is made of concrete or the like, by passing fixing bolts 6 through fixing bolt holes 17 (described later) in the base plate 11 and fixing them in place; horizontal members 51 fixed to the upper surface of the plurality of guardrail support posts 1 by welding or the like; and horizontal members 52 and 53 erected by fixing to the front and back sides of the plurality of guardrail support posts 1, respectively, by welding or the like. In this embodiment, the guardrail 3 is a temporary type used, for example, in road construction on a bridge, and the lower deck 7 of the base plate 11 is supported by the receiving plates 12 via bolts 6. In this embodiment, the guardrail 3 is a type in which the horizontal members 51, 52, and 53 are attached without brackets, but it is not limited to this, and it may also be implemented as a type in which the horizontal members are attached via brackets. Furthermore, the protective fence 3 according to this embodiment may be a permanent type installed in the median strip of a road.

[0030] As shown in Figures 2(a) and 1(b), the protective fence support post 1 according to this embodiment comprises a base plate 11 having fixing bolt holes 17 that are fixed to a foundation slab 7, and a pipe body 21 erected from the base plate 11 by a welded joint 22, and is a protective fence support post capable of absorbing impact loads applied to the pipe body 21 through plastic deformation of the pipe body 21.

[0031] Furthermore, as shown in Figures 2(a) to 2(c), the protective fence support post 1 according to this embodiment has a rectangular pipe body 21, and a pair of notched holes 31A and 31B are provided at the four corners 21e of the lower end 21a of the rectangular pipe body 21, with a gap 33 in the direction of the pipe axis (the direction between the lower end 21a and the upper end 21b of the pipe body 21).

[0032] Here, the notched holes 31A and 31B of the protective fence support post 1 are both through holes formed by punching or the like so as to penetrate the pipe body 21.

[0033] Furthermore, as shown in Figures 2(a) to 2(c), the height position and diameter of the lower notch 31A and the height position and diameter of the upper notch 31B are approximately the same.

[0034] Specifically, the diameter of each pair of notches 31A and 31B is set to be between 25 mm and 48 mm. Furthermore, in demonstration tests, it was confirmed that when the diameter of the lower notch 31A is set to 30 mm and the diameter of the upper notch 31B is set to 40 mm, making the upper notch 31B larger, a superior shock absorption effect can be achieved compared to when the sizes are approximately the same.

[0035] The reason for setting the diameters of this pair of notches 31A and 31B as described above will be explained below.

[0036] First, when a load test is performed on a square support column, for example, in the case of the SB type (standard support column spacing of 1.0m), the graph in Figure 3 shows that the ultimate bearing capacity required is 30kN or more.

[0037] Furthermore, when static load tests were conducted on protective fence posts 1 under the same conditions, with notches 31A and 31B having diameters of 30 mm (Figure 4(a)), 20 mm (Figure 4(b)), and 15 mm (Figure 4(c)), only the posts with notches 31A and 31B having a diameter of 30 mm, as shown in Figure 4(a), did not fracture until they deformed 300 mm, thus meeting the required requirements and providing the necessary energy absorption. In other words, as shown in Figures 4(b) and 4(c), when the diameter of the notches 31A and 31B was 20 mm or less, they fractured before deforming 300 mm, failing to meet the required requirements and not providing the necessary energy absorption.

[0038] Furthermore, the following relationship can be obtained between the section modulus Z of the protective fence post 1 and the post bearing capacity Pw. Pw=0.0007Z-4.7255 Z = (Pw + 4.7255) / 0.007 From this, we will determine the section modulus of Z required for Pw to be 30kN or greater. Z ≥ (30 + 4.7255) / 0.007 = 49608 mm 3 Therefore, Z = 49608 mm 3 After considering various hole diameters that would satisfy the requirements, we determined that it should be 48 mm. Therefore, it is considered that the diameters of the notches 31A and 31B will satisfy both the SB type strength and deformation performance as long as they are up to a maximum of 48 mm.

[0039] Next, a field test will be conducted to estimate the minimum diameter of the notches 31A and 31B from the displacement at the time of fracture. From the graph in Figure 5, which shows the test results, the following relationship can be obtained between the diameter φ (mm) of the protective fence support post 1 and the displacement δ mm at the time of fracture. δ = 9.6φ + 60 φ=25mm Therefore, the diameter φ of the notches 31A and 31B that do not fracture up to a displacement of 300 mm is 25 mm.

[0040] Furthermore, a static load test was conducted with notches 31A and 31B having a diameter of 25 mm. The material did not fracture until it deformed by 300 mm, confirming that it met the required specifications and that the necessary energy absorption was achieved.

[0041] Based on the above, it was found that it is preferable for the diameter of a pair of notches 31A and 31B to be set to between 25 mm and 48 mm.

[0042] Furthermore, the spacing 33 between these pair of notches 31A and 31B is set to 10 mm, and the height of the lower end of the lower notch 31A is set to 10 mm from the upper surface 11a of the base plate 11.

[0043] This is because, as a result of demonstration tests, it was found that machining is easier when a pair of notches 31A and 31B are spaced 33 apart by 10 mm or more, and the height of the lower end of the lower notch 31A is set 10 mm or more from the upper surface 11a of the base plate 11.

[0044] Next, using Figures 6 to 8, we will explain the case where a vehicle or the like collides with the horizontal members 5 or the support posts 1 of the guardrail 3, and a collision load is applied to the pipe body 21 of the support post 1 in the direction from the front side to the back side.

[0045] First, in the initial deformation stage before plastic deformation begins at the lower end 21a of the pipe body 21, as shown in Figure 6, a compressive stress P1 in the direction of the pipe axis is applied to the back side of the lower end 21a of the pipe body 21, and a tensile stress in the direction of the pipe axis is applied to the front side. At this time, as shown in Figure 6, the notches 31A and 31B of the pipe body 21 attempt to deform so that their side edges 31a on both sides in the circumferential direction spread apart due to the compressive stress in the direction of the pipe axis applied to them, and a tensile stress P2 in the circumferential direction is applied to both sides of the notches 31A and 31B in the circumferential direction.

[0046] Here, we will explain the stresses applied to the portion S1 surrounded by the two sets of notches 31A and 31B in the pipe body 21, as shown in Figure 6. First, a tensile stress P2 in the circumferential direction of the pipe is applied to this portion S1 as described above. In addition, a compressive stress P1 in the axial direction of the pipe is applied to this portion S1, which is roughly uniform across the circumferential direction of the pipe. Furthermore, a bending stress is applied to this portion S1, which causes it to deform inward. When these compressive stresses P1 in the axial direction, tensile stresses P2 in the circumferential direction, and bending stresses exceed a certain level, plastic deformation begins, causing this portion S1 to buckle and inward.

[0047] Incidentally, as shown in Figure 6, a tensile stress P2 in the circumferential direction is also applied to parts S2 located on both sides in the circumferential direction of the pipe, in relation to part S1 surrounded by two sets of notches 31A and 31B of the pipe body 21. Furthermore, a compressive stress P1 in the axial direction of the pipe is applied to part S2, which decreases as it moves further away from part S1 in the circumferential direction of the pipe.

[0048] Here, a gap 33 is provided between a pair of notches 31A and 31B. Therefore, this gap 33 can resist the circumferential tensile stress P2 applied to parts S1 and S2 of the pipe body 21 surrounded by the two pairs of notches 31A and 31B as described above. This improves the buckling strength against the circumferential tensile stress P2, thereby improving the maximum load-bearing capacity in the initial stages of deformation.

[0049] Subsequently, in the initial and later stages of deformation, as shown in Figure 7, compressive stress P1 in the axial direction, tensile stress P2 in the circumferential direction, and bending stress are continuously applied to each part S1 and S2 of the pipe body 21. As a result, as shown in Figures 7 and 8, plastic deformation progresses such that part S1, surrounded by the two sets of notches 31A and 31B, becomes concave inward, while parts S2 located on both sides of part S1 in the circumferential direction become convex outward.

[0050] Here, a gap 33 is provided between a pair of notches 31A and 31B. This gap 33 is provided to connect a portion S1 that deforms to be concave inward on the pipe body 21 and a portion S2 that deforms to be convex outward on the pipe body 21. Therefore, a load is applied to this gap 33 in the direction that causes the pipe body 21 to be concave inward and a load in the direction that causes the pipe body 21 to be convex outward. As a result, the amount of deformation of the gap 33 becomes smaller than the amount of deformation of portions S1 and S2. This means that the gap 33 resists the inward concave deformation of portion S1 surrounded by the two pairs of notches 31A and 31B, and the outward convex deformation of portions S2 located on both sides of the pipe circumferential direction relative to portion S1. As a result, the load-bearing capacity at the end of the deformation stage after plastic deformation has started is improved.

[0051] The same applies when a collision load is applied to the pipe body 21 of the protective fence support post 1 in the direction from the back to the front, so the explanation is omitted.

[0052] According to the protective fence support post 1 of the present invention as described above, if horizontal members 5 are installed on both the front and back sides of the pipe body 21, the effort of reinstalling the temporary structure is not required even when used in bridge deck replacement work. Therefore, according to the protective fence support post 1 of this embodiment, the construction period for bridge deck replacement work can be shortened and costs can be reduced.

[0053] Furthermore, according to the guardrail support post 1 of this embodiment, even when used on roads with narrow median strips (including cases where the median strip is narrowed to widen the road), as explained with reference to Figures 6 to 8, the guardrail 3, which has horizontal members 5 on both the front and back sides of the pipe body 21, can achieve a maximum load capacity equivalent to or greater than that when reinforcing plates are joined, even without reinforcing plates, in the initial deformation stage when the amount of column displacement is small. In addition, it is possible to further improve the load capacity in the final deformation stage and further reduce the number of members used, thus exhibiting excellent shock absorption effects. Therefore, according to the guardrail support post 1 of this embodiment, the reduction in the weight of the guardrail support post 1 improves the constructability of the work to install the guardrail support post 1 in the median strip of a road, shortens the construction period, and reduces costs.

[0054] Furthermore, according to the protective fence support post 1 of this embodiment, the pair of notched holes 31A and 31B are through holes that penetrate the pipe body 21, and can therefore be easily formed by punching or the like.

[0055] Furthermore, according to the protective fence support post 1 of this embodiment, the height position and diameter of the lower notch 31A and the upper notch 31B are substantially the same, so the performance of the front and back sides of the pipe body 21 can be easily made substantially the same.

[0056] Furthermore, according to the protective fence support post 1 of this embodiment, the diameter of a pair of notched holes 31A and 31B is set to be between 25 mm and 48 mm. Therefore, as described above, it has been confirmed in demonstration tests that, for example, in the SB type (standard support post spacing of 1.0 m), the protective fence support post 1 of this embodiment has an ultimate bearing capacity of 30 kN or more and can absorb impact loads without breaking until its displacement reaches 300 mm.

[0057] Furthermore, as described above, the demonstration test confirmed that the protective fence support post 1 according to this embodiment has a spacing 33 of 10 mm or more between a pair of notches 31A and 31B, and the height position of the lower end of the lower notch 31A is set to 10 mm or more from the upper surface 11a of the base plate 11, making it easy to manufacture.

[0058] Although embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0059] 1 Post for protective fence 11 Base Plate 11a Top surface of the base plate 12 Receiving plate 17 bolt holes for fixing 21. Body 21a Lower end of the pipe 21b Upper end of the tube 21e Corner of the tube 22 Welded joint 3 Protective fence 31A Notch 31B Notch 31a Side edge of the notch 33. Spacing of notched holes 51 Horizontal members 52 Horizontal members 53 Horizontal members 6. Fixing bolts 7 Floor slab (foundation) P1 Compressive stress P2 Tensile stress S1 part S2 part

Claims

1. A support column for a vehicle guardrail comprising a base plate fixed to a foundation and a pipe erected from the base plate, which can guide a colliding vehicle in a safe direction without breaking up to a predetermined displacement, and can absorb the impact load applied to the pipe through the plastic deformation of the pipe, The tube is rectangular in shape, and each of the four corners of the lower end of the rectangular tube is provided with a set of notched holes formed at intervals in the direction of the tube axis. The set of notches has a diameter of 25 mm or more and 48 mm or less, and is spaced at least 10 mm apart, with the lower end of the lower notch being at least 10 mm above the top surface of the base plate. A support post for vehicle guardrails, characterized by the following features.

2. The aforementioned pair of notches are through holes that penetrate the pipe body. A support post for a vehicle guardrail according to claim 1, characterized by the above.

3. The height position of the lower notch and the height position of the upper notch are approximately the same for the pair of notches. A support post for a vehicle guardrail according to claim 1 or 2, characterized by the above.

4. The aforementioned pair of notches are such that the diameter of the lower notch and the diameter of the upper notch are approximately the same, or the upper notch is larger. A support post for a vehicle guardrail according to any one of claims 1 to 3, characterized by the above.

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