Bridge collapse prevention buffer chain

Abstract

The present invention provides a bridge collapse prevention buffer chain that can prevent stress concentration at the contact points between rings when an impact load is applied. [Solution] A bridge collapse prevention buffer chain 1, comprising a ring connector 2 in which multiple rings are connected to each other, and a covering 3 covering the ring connector 2, connects a bridge superstructure such as a bridge girder to a bridge substructure such as a bridge abutment or bridge pier to prevent the bridge superstructure from falling, wherein the ring connector 2 is covered with a rubber elastic material except for a part of the end rings 21a (21b) at the ends, the end rings 21a (21b) and adjacent rings 22a (22b) are brought into contact, and the wire diameter of the ring steel material of one or both of the end rings 21a (21b) and adjacent rings 22a (22b) is set to be larger than the wire diameter of the ring steel material of the other rings of the ring connector 2.

Description

Technical Field

[0001] The present invention relates to a bridge-fall prevention buffer chain for preventing the fall of a bridge girder. More specifically, the present invention relates to a bridge-fall prevention buffer chain that can prevent the bridge from falling without breaking even when an impact load acts by interposing a buffer material.

Background Art

[0002] In a general bridge, the upper structure of the bridge such as the bridge girder and the lower structure of the bridge such as the abutment and pier are not rigidly joined, but are joined by roller bearings or pin bearings through support members.

[0003] Furthermore, from the perspective of preventing major accidents involving human lives, a bridge-fall prevention device is installed to prevent the upper structure of the bridge from falling off the lower structure of the bridge. As this bridge-fall prevention device, the upper structure of the bridge and the lower structure of the bridge are connected by a wire rope, a chain, or the like.

[0004] Conventionally, as this type of bridge-fall prevention device, a buffer chain in which rings are connected to each other with a buffer material such as rubber that absorbs impact so as not to break due to the impact load transmitted during an earthquake or the like has also been proposed.

[0005] For example, in Patent Document 1, each of a plurality of rings 6 is fitted to each other with a gap so that they do not contact each other, and the entire ring 6 is embedded in an elastic body 7 in a state where the rings 6 are aligned linearly, and the elastic body 7 is also filled in the gap. One end of a buffer member 5 formed in a substantially rod shape is fixed near the end of the girder 2 by a connecting member 11 and a fixing member 10, and the other end is fixed near the end of the pier 1 or an adjacent girder 2A by a connecting member 9 and a fixing member 8. A buffer chain is disclosed (see Claim 1 of the claims of Patent Document 1, paragraphs

[0029] to

[0031] of the specification, and FIGS. 1 and 2 of the drawings).

[0006] However, the cushioning chain described in Patent Document 1 had a heavy overall weight because the total length of the elastic material was long relative to the number of places where the elastic material was inserted between the rings that provided the cushioning effect. As a result, there were problems with poor transportation efficiency and work efficiency, as well as high labor costs for installing and replacing the cushioning chain. In addition, the cushioning effect was limited, and increasing the cushioning effect would result in an increased weight.

[0007] Furthermore, Patent Document 2 discloses a cushioning chain in which expansion rings 9, 9 are connected to both ends of a chain 8, and cushioning members 10, 10, which are molded from rubber or various synthetic resins and have a recessed cross-section forming an engagement portion 11 on their outer circumference, are fitted into the expansion rings 9, 9 respectively (see Claim 1 of the claims, paragraphs

[0017] to

[0022] of the specification, and Figures 1, 2, and 6 of the drawings of Patent Document 2).

[0008] However, the cushioning chain described in Patent Document 2 requires two cushioning members 10 to be fitted per chain, which is time-consuming and increases labor costs. Furthermore, depending on how the impact load is transmitted, the cushioning effect may be weakened.

[0009] Furthermore, Patent Document 3 discloses a bridge collapse prevention buffer chain proposed by the applicants of the present application, which comprises a plurality of interconnected rings 21 to 25 and connects a bridge superstructure such as a bridge girder H to a bridge substructure such as a bridge abutment B or bridge pier to prevent the bridge superstructure from falling. In this buffer chain, the connection points between the rings are spaced apart at four locations and the area around them is solidified with a rubber elastic body 3, and the length of the rubber elastic body 3 is within the length of four rings (see Claim 1 of the claims in Patent Document 3, paragraphs

[0024] to

[0040] of the specification, and Figures 1 to 5 of the drawings, etc.).

[0010] The bridge collapse prevention buffer chain described in Patent Document 3 has the function of mitigating impact tensile force because the chains do not come into direct contact with each other. However, in the current product (conventional bridge collapse prevention buffer chain 10), which is an embodiment of the bridge collapse prevention buffer chain described in Patent Document 3, the end ring A and the adjacent ring B were in contact from three viewpoints: (1) transmission of impact force from the end ring A to the rubber coating which is made of a rubber elastic material solidified around the chain, which is the shockless portion; (2) fixing the chain during the vulcanization molding of the rubber coating; and (3) securing space for passing the shackle through the end ring A during assembly.

[0011] However, when a conventional bridge collapse prevention buffer chain 10, shown in Figures 7 and 8, in which the end ring A and the adjacent ring B are in contact, was subjected to FEM analysis as shown in Figure 9, it was found that when an impact load was applied, stress concentrated on the end ring A and the adjacent ring B, resulting in locally high stress levels. Therefore, there was a demand for the development of a new type of bridge collapse prevention buffer chain that could prevent stress concentration at the contact point between the end ring A and the adjacent ring B when an impact load is applied, while simultaneously achieving the above-mentioned problems (1) to (3). [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 9-242019 [Patent Document 2] Japanese Patent Publication No. 2002-97607 [Patent Document 3] Japanese Patent Publication No. 2016-138416 [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 bridge collapse prevention buffer chain that can prevent stress concentration at the contact points between rings when an impact load is applied. [Means for solving the problem]

[0014] The bridge collapse prevention buffer chain according to claim 1 comprises a ring assembly in which a plurality of rings are connected to each other, and a covering body that covers the ring assembly, and is a bridge collapse prevention buffer chain that connects a bridge superstructure such as a bridge girder to a bridge substructure such as a bridge abutment or bridge pier to prevent the bridge superstructure from falling, wherein the ring assembly is covered with the covering body except for a part of the end ring at the end, the end ring and the adjacent ring are in contact, and the wire diameter of the ring steel material of at least one of the rings of the end ring and the adjacent ring is set to be larger than the wire diameter of the ring steel material of the other rings of the ring assembly.

[0015] The bridge collapse prevention buffer chain according to claim 2 is characterized in that, in the bridge collapse prevention buffer chain according to claim 1, the wire diameter of the ring steel material of the adjacent ring is set to be larger than the wire diameter of the ring steel material of the other rings of the ring connecting body.

[0016] The bridge collapse prevention buffer chain according to claim 3 is characterized in that, in the bridge collapse prevention buffer chain according to claim 1 or 2, the plurality of rings are subjected to rust prevention treatment such as hot-dip galvanizing, followed by rough surface treatment such as phosphoric acid treatment, and then covered with the coating.

[0017] The bridge collapse prevention buffer chain according to claim 4 is characterized in that, in the bridge collapse prevention buffer chain according to claim 2, the wire diameter of the ring steel material of the adjacent ring is set between 20% and 100% of the inner width of the end ring.

[0018] The bridge collapse prevention buffer chain according to claim 5 is characterized in that, in the bridge collapse prevention buffer chain according to claim 2, the wire diameter of the ring steel material of the adjacent ring is set between 50% and 100% of the inner width of the end ring.

[0019] The bridge collapse prevention buffer chain according to claim 6 is the bridge collapse prevention buffer chain according to claim 1, characterized in that the end ring and the adjacent ring are connected in a state of being twisted at a first angle, the adjacent ring and the other rings of the ring connector covered by the covering are connected in a state of being twisted at a second angle, and the first angle and the second angle are different angles. [Effects of the Invention]

[0020] According to the first to sixth inventions, the wire diameter of the ring steel material of the end ring and the adjacent ring is set to be larger than the wire diameter of the ring steel material of the other rings in the ring assembly, so that stress concentration at the contact portion between the end ring and the adjacent ring can be prevented when an impact load is applied. Furthermore, even if tensile force is generated in the bridge collapse prevention buffer chain in advance, the stress concentration at the contact portion can be mitigated and the impact force can be reduced.

[0021] Furthermore, according to the first to sixth inventions, since the end rings and adjacent rings are in constant contact, the impact force from the end rings to the covering can be transmitted smoothly. Moreover, according to the first to sixth inventions, since the left and right pair of end rings and the adjacent rings inside them are in contact, the chain can be easily fixed during the vulcanization molding of the covering by simply applying tensile force (tension) to the left and right pair of end rings and interposing spacers or the like between each ring, thereby shortening the manufacturing time and reducing the manufacturing cost of the bridge collapse prevention buffer chain. Furthermore, according to the first to sixth inventions, by bringing the end rings and adjacent rings into contact, the protruding length of the end rings from the covering can be increased, and space can be secured for passing shackles through the end rings during assembly.

[0022] In particular, according to the second invention, the contact area between the end ring and the adjacent ring can be increased without changing the size of the ring steel material of the end ring from the current product, eliminating the need to change the size of other related components such as the shackle, and making it possible to reduce stress concentration due to impact force compared to the current product while keeping manufacturing costs down.

[0023] Particularly, according to the third invention, since rust prevention treatment such as hot dip galvanizing is performed and surface roughening treatment such as phosphate treatment is carried out, not only the corrosion resistance of the chain is improved, but also the adhesion of the rubber elastic body does not decrease. Therefore, the corrosion resistance can be improved while maintaining the buffering effect, and the durability can also be improved. In addition, it is possible to save the labor of performing rust prevention treatment on the exposed part of the chain later.

[0024] [[ID=�]]

[0025] Particularly, according to the fourth invention, since the wire diameter of the adjacent ring steel material is set between 20% and 100% of the inner surface width of the end ring, the overall weight can be suppressed without particularly increasing the size of the covering body that covers a part of the ring connecting body, and stress concentration on the contact part can be alleviated.

[0026] Particularly, according to the fifth invention, since the area of the contact part between the end ring and the adjacent ring can be increased without changing the covering thickness of the elastic body of the covering body, stress concentration on the contact part can be more optimally alleviated.

Brief Description of the Drawings

[0027] [Figure 1] FIG. 1 is a perspective view showing a case where the bridge-fall prevention buffer chain according to an embodiment of the present invention is connected and spanned between a concrete bridge pier and a bridge girder made of H steel. [Figure 2] FIG. 2 is a view showing the same bridge-fall prevention buffer chain, where (a) is a perspective front view and (b) is a plan view. [Figure 3] FIG. 3 is a cross-sectional view showing the contact state between the end ring and the adjacent ring of the ring connecting body of the same bridge-fall prevention buffer chain. [Figure 4] Figure 4 is a graph showing the relationship between static and dynamic tensile loads (kN) obtained from tensile tests and the elongation (mm) of the rubber part. [Figure 5] Figure 5 is a graph showing the relationship between tensile load (kN) and absorbed energy (kN·m) in a static tensile test. [Figure 6] Figure 6 is a graph showing the relationship between tensile load (kN) and displacement (mm) in the static fracture test results. [Figure 7] Figure 7 is a perspective front view showing a conventional (current product) bridge collapse prevention buffer chain. [Figure 8] Figure 8 is a cross-sectional view showing the contact state between the end ring and the adjacent ring of the ring-connected member of the conventional (current product) bridge collapse prevention buffer chain shown above. [Figure 9] Figure 9 shows the FEM analysis results of stress concentration in a conventional (current) bridge collapse prevention buffer chain. [Figure 10] Figure 10 is a vertical cross-sectional view of a bridge collapse prevention buffer chain according to a second embodiment of the present invention, where (a) shows the connection between the end ring and the adjacent ring, and (b) shows the connection between the adjacent ring and the intermediate ring. [Figure 11] Figure 11 is a perspective front view showing the bridge collapse prevention buffer chain 1' according to this embodiment. [Modes for carrying out the invention]

[0028] Hereinafter, a bridge collapse prevention buffer chain according to an embodiment of the present invention will be described with reference to the drawings.

[0029] [First Embodiment] The bridge collapse prevention buffer chain 1 according to the first embodiment of the present invention will be described with reference to Figures 1 to 3. Figure 1 is a perspective view showing the bridge collapse prevention buffer chain 1 according to the embodiment of the present invention when a steel girder H1 is connected to a bridge abutment P. Figure 2(a) is a perspective front view showing the bridge collapse prevention buffer chain 1 according to this embodiment, and Figure 2(b) is a plan view showing the bridge collapse prevention buffer chain 1 alone. Figure 3 is a cross-sectional view showing the contact state between the end ring and adjacent ring of the ring connector 2 of the bridge collapse prevention buffer chain 1.

[0030] As shown in Figure 1, this bridge collapse prevention buffer chain 1 is a shock-absorbing chain that prevents the bridge superstructure from falling from the bridge substructure during a major earthquake while absorbing and mitigating impact forces. It connects the bridge substructure, such as abutments P and piers, with the bridge superstructure, which includes steel girders H1 such as H-shaped steel and I-shaped steel, via brackets B1 and B2, allowing for some slack in length.

[0031] The configuration shown in Figure 1 illustrates a case where a reinforced concrete abutment P serves as the bridge substructure, and a steel girder H1 made of H-beams is connected as the bridge superstructure. The illustrated configuration shows an example with one bridge collapse prevention buffer chain 1 installed, but of course, multiple chains may be installed as appropriate depending on the size and number of girders of the bridge.

[0032] As shown in Figure 2, the bridge collapse prevention buffer chain 1 according to this embodiment consists of a ring connector 2, which is a chain body in which a plurality of rings are connected to each other, and a covering 3 made of rubber, resin, or the like that covers a part of the ring connector 2.

[0033] <Ring-shaped connector> As shown in Figure 2, the ring connector 2 is a ring connector in which nine ring steel materials, processed into an oval shape from a steel rod, are connected in a chain-like manner so that the axes of the rings are perpendicular to each other. In this embodiment, each ring steel material of the ring connector 2 is made of steel materials such as SWRM6, SWRM8, SWM-B, and SS400, which are processed into an oval shape and connected in a chain-like manner to constitute the ring connector 2. Of course, the type of steel material is not limited to those exemplified, and it goes without saying that it should be appropriately selected according to the size of the bridge collapse prevention buffer chain 1.

[0034] Furthermore, this ring connector 2 consists of a pair of left and right end rings 21a, 21b located at the outermost ends, adjacent rings 22a, 22b connected to these end rings 21a, 21b, and five intermediate rings 23 to 27 connecting these adjacent rings 22a, 22b.

[0035] (End ring) As shown in Figures 1, 2(a), and 2(b), the end rings 21a and 21b are ring-shaped steel materials that partially protrude from the cylindrical circular left and right end faces 3a of the covering body described later, and are connected to the chain that connects to brackets B1 and B2 via shackles S1. The end rings 21a and 21b in this embodiment are made of commercially available Type 1 chain ring-shaped steel materials with a diameter of φ19 mm. Of course, the wire diameter of the steel material is not limited to the example shown, and it goes without saying that it can be appropriately selected according to the size of the bridge collapse prevention buffer chain 1.

[0036] (Adjacent rings) The adjacent rings 22a and 22b are located adjacent to the end rings 21a and 21b mentioned above, and each is connected to the end rings 21a and 21b, and has the function of transmitting the earthquake impact force input from the end rings 21a and 21b to the covering 3.

[0037] These adjacent rings 22a and 22b are made of commercially available Type 2 chains with a ring steel diameter of φ25 mm. In other words, as shown in Figures 2(a) and 2(b), the wire diameter of the ring steel of the adjacent rings 22a and 22b is set to be larger than the wire diameter of the ring steel of the end rings 21a and 21b mentioned above and the intermediate rings 23 to 27 described later.

[0038] As described in the background technology, it is preferable for the end rings 21a, 21b and the adjacent rings 22a, 22b to be in contact for three reasons: (1) to transmit impact force to the covering 3, (2) to fix the ring connection 2 so that it does not move until the rubber material and resin components of the covering 3 harden during vulcanization molding, and (3) to secure space for inserting the shackle S1 through the end rings 21a, 21b. However, if the end rings 21a, 21b and the adjacent rings 22a, 22b are in contact, stress may concentrate at the contact point between the end rings 21a, 21b and the adjacent rings 22a, 22b when an impact load is applied, such as during bridge collapse, and there is a risk of fracture.

[0039] Therefore, as shown in Figure 3, in the bridge collapse prevention buffer chain 1, the wire diameter of the ring steel material of adjacent rings 22a and 22b is increased compared to the wire diameter of the ring steel material of end rings 21a and 21b. By making the contact length between the end rings 21a and 21b and the adjacent rings 22a and 22b approximately 19 mm, the contact area is increased compared to the aforementioned existing product (see Figures 7 and 8), thereby reducing the surface pressure during impact and reducing the risk of breakage (see also Figure 5).

[0040] Next, we will explain the relationship between the chain ring diameter and the diameter of the covering 3, which was investigated through simulation, using Figure 3 and Tables 1 and 2 below.

[0041] [Table 1]

[0042] [Table 2]

[0043] Tables 1 and 2 show the effect of the relationship between the wire diameter of adjacent rings 22a and 22b and the inner width of end rings 21a and 21b on the thickness of the covering 3. Comparative examples A and B shown in Tables 1 and 2 are defined as follows: wire diameter (ΦA) of end rings 21a and 21b, wire diameter (ΦB) of adjacent rings 22a and 22b, inner width (dA) of end rings 21a and 21b, and thickness (ΦR) of covering 3. The thickness (t) is calculated by subtracting the wire diameter (ΦA) and inner width (dA) of end rings 21a and 21b from the thickness (ΦR) of the covering, and dividing this by two. The thickness (t) is set to 5 mm, which is the minimum thickness required for covering in the manufacture of bridge collapse prevention buffer chains.

[0044] Furthermore, in Comparative Example A in Table 1, the wire diameter (ΦB) of adjacent rings 22a and 22b is larger than the wire diameter (ΦA) of end rings 21a and 21b, and is approximately 60% of the inner width (dA) of end rings 21a and 21b. In contrast, in Comparative Example B in Table 1, the wire diameter (ΦB) of adjacent rings 22a and 22b is larger than the wire diameter (ΦA) of end rings 21a and 21b, and the inner width (dA) of end rings 21a and 21b is set to be 10% or less of the inner width (dA) of end rings 21a and 21b. In Comparative Example B in Table 1, the thickness (ΦR) of the coating 3 in Comparative Example B needs to be approximately 2.5 times or more than the thickness (ΦR) of the coating in Comparative Example A.

[0045] Furthermore, in Comparative Example A in Table 2, the wire diameter (wire diameter ΦB) of adjacent rings 22a and 22b is larger than the wire diameter (wire diameter ΦA) of end rings 21a and 21b, and is approximately 60% of the inner width (inner width dA) of end rings 21a and 21b. In contrast, in Comparative Example B in Table 1, the wire diameter (wire diameter ΦB) of adjacent rings 22a and 22b is larger than the wire diameter (wire diameter ΦA) of end rings 21a and 21b, and the inner width (inner width dA) of end rings 21a and 21b is set to be 20% or less of the inner width (inner width dA) of end rings 21a and 21b. In Comparative Example B in Table 1, the thickness (ΦR) of the coating 3 in Comparative Example B needs to be approximately 1.5 times or more than the thickness (ΦR) of the coating in Comparative Example A.

[0046] From the comparative examples in Tables 1 and 2, if the wire diameter (wire diameter ΦB) of adjacent rings 22a and 22b is greater than the wire diameter (wire diameter ΦA) of end rings 21a and 21b, and is less than 20% of the inner width (inner width dA) of end rings 21a and 21b, the total length in the short direction of adjacent rings 22a and 22b will be greater than the thickness in the short direction of the coating 3, requiring the coating to be 1.5 times thicker or more, resulting in an increased size of the coating 3.

[0047] On the other hand, by setting the wire diameter (wire diameter ΦB) of adjacent rings 22a and 22b to be at least 20% of the inner width (inner width dA) of end rings 21a and 21b, the overall weight can be reduced without increasing the size of the covering 3 that covers a part of the ring connection 2, and stress concentration at the contact points can be alleviated.

[0048] Next, we will further examine Type 6, which has a large difference from the higher wire diameters. Furthermore, with the minimum wire diameter B set to φ43mm, the Hertz surface pressure was calculated by varying the inner surface width A, as shown in Table 3. Additionally, to examine the rubber coating thickness of the covering 3, we set the minimum required rubber coating thickness to 5mm and examined the range of wire diameters B that fall below this thickness, as shown in Table 4.

[0049] [Table 3]

[0050] [Table 4]

[0051] Table 4 shows the relationship between the wire diameters of adjacent rings 22a and 22b and the inner surface widths of end rings 21a and 21b, so that the coating thickness of the coating body 3 is within the minimum required range. The wire diameters (ΦA) of the end rings 21a and 21b, the wire diameters (ΦB) of the adjacent rings 22a and 22b, the inner widths (dA) of the end rings 21a and 21b, and the thickness (ΦR) of the covering 3 are shown. The thickness (t) obtained by subtracting the wire diameters (ΦA) of the end rings 21a and 21b and the inner widths (dA) of the end rings 21a and 21b from the thickness (ΦR) of the covering is divided in half, and this is shown to be within 5 mm, which is the minimum thickness required to prevent the buffer chain from falling.

[0052] It can be seen that, in order for the thickness (t) of the covering 3 to be within 5 mm, the wire diameter ΦB of the adjacent rings 22a and 22b must be at least 35% of the inner surface width dA of the end rings 21a and 21b.

[0053] As shown in Table 3, Comparative Example A, which represents the Hertz surface pressure with the wire diameter (A wire diameter) of the end rings 21a and 21b and the wire diameter (B wire diameter) of the adjacent rings 22a and 22b set to 42 mm and the inner width (A inner width) of the end rings 21a and 21b set to 67 mm, was compared with Comparative Example B, which represents the Hertz surface pressure with the wire diameter (A wire diameter) of the end rings 21a and 21b set to 42 mm and the wire diameter (B wire diameter) of the adjacent rings 22a and 22b set to 43 mm and the inner width (dA) of A varied. From the comparison results, it can be seen that the wire diameters that result in a Hertz surface pressure greater than that of Comparative Example A are those with an inner width (A) of 72 mm or more, and that the wire diameter ΦA of the adjacent rings 22a and 22b is 50% or more of the inner width dA of the end rings 21a and 21b.

[0054] The results in Tables 3 and 4 show that by setting the wire diameter ΦB of adjacent rings 22a and 22b to be at least 50% to 100% of the inner surface width dA of end rings 21a and 21b, the contact area between the end rings 21a and 21b and the adjacent rings 22a and 22b increases without changing the thickness of the elastic coating of the covering. This allows for more optimal stress concentration at the contact area and reduces impact force.

[0055] Here, it is conceivable to further increase the wire diameter of the ring steel material of adjacent rings 22a and 22b to φ26mm and φ29mm. However, if the diameter of the ring steel material is φ26mm and φ29mm, considering that the minimum required coating thickness of the rubber elastic body is 5mm, it would not be possible to fit it within the same 100mm diameter cylinder of the coating body 3 as the current product, and the size of the coating body 3 would also need to be increased. For this reason, in order to avoid increasing manufacturing costs and reducing workability due to increased weight, it is preferable that the wire diameter of the ring steel material of adjacent rings 22a and 22b be φ25mm.

[0056] Of course, as the contact area between the end rings 21a, 21b and the adjacent rings 22a, 22b increases, the stress concentration of impact forces is reduced. Therefore, it is thought that a similar effect can be achieved even if the wire diameter of the ring steel material of the end rings 21a, 21b is φ25 mm and the wire diameter of the ring steel material of the adjacent rings 22a, 22b is φ19 mm.

[0057] (Intermediate ring) The intermediate rings 23-27 connect adjacent rings 22a and 22b and have the function of transmitting impact force between end rings 21a and 21b. The ring steel material of these intermediate rings 23-27 is the same as that of the end rings 21a and 21b, consisting of commercially available Type 1 chain ring steel material with a ring steel diameter of φ19 mm.

[0058] Furthermore, as shown in Figures 2(a) and 2(b), the ring connector 2 is covered and solidified with a covering 3, with a gap D1 (in this embodiment, D1 = approximately 23 mm, which corresponds to the diameter of the ring steel material) between the ring steel materials, except for the contact portions between the end rings 21a, 21b and the adjacent rings 22a, 22b.

[0059] <Coating> As shown in Figures 2(a) and 2(b), the covering 3 according to this embodiment is made of a rubber elastic body that covers a part of the ring connector 2 and is molded into a cylindrical shape with a diameter of about 100 mm. Because it has high resistance and rebound force, hard rubber made by mixing natural rubber and synthetic rubber and vulcanizing it is used. It is preferable that the covering 3 be made of hard rubber with excellent weather resistance and UV resistance, but it may be made of any rubber elastic body that has a cushioning effect against impact loads. In addition, the covering 3 may be made of other elastic bodies such as elastoplastic bodies, viscoelastic bodies, or resin members, as long as it has a cushioning effect against impact loads.

[0060] Furthermore, the shape of the covering body 3 is not limited to a cylindrical shape; it can be a prismatic shape or a cross-shaped cross-section, as long as it covers and solidifies a portion of the ring connecting body 2 at predetermined intervals.

[0061] Here, a rubber-elastic material refers to an object that exhibits rubber elasticity, meaning it has a Young's modulus of approximately 1 to 10 MPa at room temperature, stretches significantly without breaking under small stress, and returns to its original shape almost instantaneously when the external force is removed. Hard rubber, on the other hand, refers to rubber-elastic materials such as CR (Chloroprene) rubber, NRB (nitrile rubber), EPDM (ethylene propylene diene monomer), and SBR (styrene-butadiene rubber), which are made by adding a large amount of sulfur to the raw rubber, resulting in a hardness of 70° or higher according to the JIS K6253 durometer hardness test (Type A).

[0062] Furthermore, the bridge collapse prevention buffer chain 1 is constructed by hot-dip galvanizing the ring connector 2, then treating the portion to be covered with a rubber elastic material with phosphoric acid, and finally covering it with a rubber elastic material coating 3 and solidifying it. As a result, the adhesion force of the coating 3 to the ring connector 2 of the bridge collapse prevention buffer chain 1 is comparable to that of a chain without plating, and the shock absorption buffer effect is also enhanced. In addition, the effort of applying rust prevention treatment to exposed parts after coating is eliminated.

[0063] Although hot-dip galvanizing was used as an example of rust prevention treatment for the ring connector 2, the rust prevention treatment for the ring connector is not limited to hot-dip galvanizing. Other rust prevention treatments such as electroplating, electroless plating, and vapor deposition are also acceptable. In short, any treatment that can prevent the ring connector 2 from rusting for a desired period of time or longer is acceptable. Furthermore, phosphate treatment is also a surface roughening treatment that makes the surface of the ring connector 2 rough, and is not limited to phosphate treatment as long as it is a treatment that improves the adhesion between the ring connector 2 and the rubber elastic material.

[0064] According to the bridge collapse prevention buffer chain 1 of the embodiment of the present invention described above, the end rings 21a (21b) and adjacent rings 22a (22b) are in constant contact, so the impact force from the end rings 21a (21b) to the covering 3 can be transmitted smoothly. Moreover, with the bridge collapse prevention buffer chain 1, the left and right pair of end rings 21a and 21b and the adjacent rings 22a (22b) inside them are in contact, so by applying tensile force (tension) to the left and right pair of end rings 21a and 21b and interposing spacers or the like between each ring, the chain of the ring connector 2 can be easily fixed during the vulcanization molding of the covering 3, thereby shortening the manufacturing time and reducing the manufacturing cost of the bridge collapse prevention buffer chain.

[0065] Furthermore, with the bridge collapse prevention buffer chain 1, by bringing the end ring 21a (21b) into contact with the adjacent ring 22a (22b), the protruding length of the end ring 21a (21b) from the covering 3 can be increased. Therefore, when assembling the bridge superstructure, which includes the steel girder H1, to connect the bridge substructure, such as the abutment P, via brackets B1 and B2, space can be secured for passing the shackle S1 through the end ring 21a (21b).

[0066] Furthermore, with the bridge collapse prevention buffer chain 1, only the adjacent rings 22a (22b) are enlarged, so the contact area between the end rings 21a (21b) and the adjacent rings 22a (22b) can be increased without changing the size of the ring steel material of the end rings 21a (21b) from the current product, eliminating the need to change the size of other related components such as the shackle S1. For this reason, the bridge collapse prevention buffer chain 1 can mitigate stress concentration from impact forces while keeping manufacturing costs down compared to the conventional bridge collapse prevention buffer chain 10.

[0067] Furthermore, the bridge collapse prevention buffer chain 1 is treated with rust prevention measures such as hot-dip galvanizing and surface roughening measures such as phosphoric acid treatment. This not only improves the corrosion resistance of the chain in the ring connector 2, but also prevents a decrease in the adhesion strength of the rubber elastic material in the covering 3. Therefore, it is possible to improve corrosion resistance and durability while maintaining the buffer effect. In addition, it eliminates the need to apply rust prevention treatment to the exposed parts of the chain afterward.

[0068] [Second Embodiment] Next, the bridge collapse prevention buffer chain 1' according to the second embodiment of the present invention will be described using Figures 10 and 11. The only difference between the bridge collapse prevention buffer chain 1' according to the second embodiment and the bridge collapse prevention buffer chain 1 according to the first embodiment described above is that the rings of the ring connector are connected in a state where they are twisted together by rotating around the axis of the covering 3. Therefore, this point will be explained mainly, and the other configurations will be omitted from the explanation. Figure 10 is a vertical cross-sectional view of the bridge collapse prevention buffer chain 1' according to the second embodiment of the present invention, where (a) shows the connection between the end ring 21a (21b) and the adjacent ring 22a (22b), and (b) shows the connection between the adjacent ring 22a (22b) and the intermediate rings 23 to 27. Figure 11 is a perspective front view showing the bridge collapse prevention buffer chain 1' according to this embodiment.

[0069] As shown in Figure 10, the bridge collapse prevention buffer chain 1' is constructed by twisting the end rings 21a (21b) and adjacent rings 22a (22b) of the ring connector 2 to a state where they are tilted by a predetermined angle α (22.5 degrees in this embodiment), which is a first angle, from a vertical state perpendicular to the axes of the intermediate rings 23 to 27. In this state, the ring connector 2 is solidified and covered with the covering body 3. The predetermined angle α may be any other angle depending on the wire diameter of the end rings 21a (21b) and adjacent rings 22a (22b) of the ring connector 2.

[0070] Furthermore, the intermediate ring 23(27) connected to the adjacent ring 22a(22b) may be twisted from a vertical state perpendicular to the axis of the intermediate rings 23-27 to a state inclined by a second angle, which is a predetermined angle β (23 degrees in this embodiment), and in that state, the covering body 3 may be solidified and covered around the ring connector 2. The predetermined angle β may be any angle different from the predetermined angle α mentioned above, which corresponds to the wire diameter of the adjacent ring 22a(22b) and intermediate ring 23(27) of the ring connector 2.

[0071] In this state, the ring connector 2 of the bridge collapse prevention buffer chain 1', with a part of the ring twisted, is covered by the covering 3. Therefore, when an impact load is transmitted to the bridge collapse prevention buffer chain 1', the resulting tensile force causes the rings 21a (21b) to 22a (22b) of the ring connector 2 to separate.

[0072] Consequently, the rings 23 and 25 inevitably attempt to rotate in the direction that eliminates the twisting of the ring connector 2, that is, in the opposite direction to the arrows in Figures 10 and 11. At this time, the rings 23 and 25 attempt to push and rotate only a portion of the surrounding covering 3. Therefore, according to the bridge collapse prevention buffer chain 1' of the second embodiment, the transmission of impact loads is delayed, and the energy of the impact loads can be converted into kinetic energy and consumed for absorption. This improves the buffering effect in absorbing impact loads during earthquakes.

[0073] [Confirmation Test] Next, using Figures 4 to 6, we will explain the tensile tests conducted to confirm the effects of the present invention. In each test specimen, a load (kN) was applied, and the relationship between the elongation (mm) of the rubber part, the absorbed energy (kN·m), and the displacement (mm) was confirmed. Figure 4 is a graph showing the relationship between the static and dynamic tensile load (kN) and the elongation (mm) of the rubber part in the tensile tests, and Figure 5 is a graph showing the relationship between the tensile load (kN) and the absorbed energy (kN·m) in the static tensile test. Figure 6 is a graph showing the relationship between the tensile load (kN) and the displacement (mm) in the static fracture test results.

[0074] As a test specimen, a conventional bridge collapse prevention buffer chain 10, shown in Figures 7 and 8, was created as an example (current product). The ring connector R1 of the bridge collapse prevention buffer chain 10 is a ring connector made up of 11 ring steel members, each consisting of a commercially available Type 1 chain with a diameter of φ19 mm. In addition, each ring steel member of the ring connector R1 is installed at a predetermined interval D1 = 23 mm to mitigate impact tensile force, with the rubber elastic material of the covering R2 interposed between them. The covering R2 is a cylindrical body with a diameter of 100 mm and a length of 699.1 mm.

[0075] Furthermore, as an example (product 1), the aforementioned bridge collapse prevention buffer chain 1 shown in Figures 2 and 3 was created. As described above, in the ring connector 2 of the bridge collapse prevention buffer chain 1, the wire diameter of the ring steel material of adjacent rings 22a and 22b has been increased to that of a commercially available type 2 chain with a diameter of φ25 mm, and the contact area between the end rings 21a and 21b and the adjacent rings 22a and 22b has been set to be larger than that of the current product (see Figures 7 and 8). In order to fit within the length of the covering body R2 of the current product, the number of ring steel materials has been reduced compared to the ring connector R1, and it is composed of a total of 9 ring steel materials. The covering body 3 is a cylindrical body with a diameter of 100 mm and a length of 694.8 mm.

[0076] Furthermore, as a comparative example (product 2), a bridge collapse prevention buffer chain with substantially the same configuration as the aforementioned bridge collapse prevention buffer chain 1 was created. The only differences between comparative example (product 2) and example (product 1) are that, in example (product 1), the gap D1 = 23 mm between the ring steel materials of adjacent rings 22a, 22b and intermediate rings 23 and 27 is compared with comparative example (product 2), where the gap D2 = 37 mm between the ring steel materials of adjacent rings 22a, 22b and intermediate rings 23 and 27 is compared with comparative example (product 2), where the gap D1 = 22 mm between the ring steel materials of intermediate rings 24, 25 and 26 is compared with comparative example (product 2), where the gap D3 = 33 mm between the ring steel materials of intermediate rings 24, 25 and 26 is compared with comparative example (product 2). For this reason, the covering body 3 is a cylindrical body with a diameter of 100 mm and a length of 698.0 mm.

[0077] As shown in Figure 4, a clear correlation is observed between the results of the static tensile test and the dynamic tensile test. Therefore, it is considered that dynamic test results close to the usage form of the bridge collapse prevention buffer chain 1 according to the present invention can be estimated from the static tensile test, which makes it easy to obtain detailed continuous data. In addition, as indicated by the arrows in the figure, an increase in spring stiffness is observed in the example (product 1) and comparative example (product 2) compared to the current example (current product).

[0078] As shown in Figure 5, in the range of small impact loads up to 53kN indicated by the arrows in the graph, it is estimated that the generated load in the current example will be lower if the same input energy is applied to each test specimen during impact. However, in the range of large impact loads exceeding 53kN, the comparative example is expected to generate a smaller load than the current example. In other words, the comparative example (product 2) is found to generate a lower load compared to the current example (current product) when the input energy is large.

[0079] As shown in Figure 6, the static fracture test results were as follows: the current example (current product) had a maximum load of 383.5 kN and an elongation of 344.8 mm at fracture; the example (product 1) had a maximum load of 379.0 kN and an elongation of 205.8 mm at fracture; and the comparative example (product 2) had a maximum load of 380.0 kN and an elongation of 261.5 mm at fracture. Therefore, although the amount of absorbed energy differs due to the different number of chain links and thus the different elongations at fracture, it can be concluded that there is no significant difference in the maximum load among the test specimens.

[0080] Furthermore, since the fracture locations of the test specimens in both the example (product 1) and the comparative example (product 2) were not at the contact points between the contacting end rings 21a, 21b and the adjacent rings 22a, 22b, it was confirmed that even if there are chains of different diameters in the bridge collapse prevention buffer chain 1 according to the embodiment of the present invention, this does not create a weak point, and stress concentration at the contact points between rings can be prevented when an impact load is applied.

[0081] Although the bridge collapse prevention buffer chain 1 according to an embodiment of the present invention has been described in detail above, the embodiments described above or illustrated are merely examples of embodiments that have been materialized in carrying out the present invention, and the technical scope of the present invention should not be interpreted as being limited by these embodiments. In particular, although an example was given in which the ring steel material of the adjacent rings 22a and 22b is increased in size so as to increase the contact area between the end rings 21a and 21b and the adjacent rings 22a and 22b, the wire diameter of the ring steel material of one or both of the end rings 21a (21b) and adjacent rings 22a (22b) may be set to be larger than the wire diameter of the other ring steel material, such as setting the wire diameter of the ring steel material of the end rings 21a and 21b to φ25 mm and the wire diameter of the ring steel material of the adjacent rings 22a and 22b to φ19 mm. [Explanation of Symbols]

[0082] 1,1': Bridge collapse prevention buffer chain 2: Ring connector 21a, 21b: End rings (chain A) 22a, 22b: Adjacent rings (chain B) 23-27: Intermediate ring 3: Covering body 3a: End face S1, S2: Shackle B1, B2: Brackets P: Abutment (bridge substructure) H1: Steel girder (bridge superstructure) dA: Inner width ΦA: Wire diameter of the end ring ΦB: Wire diameter of adjacent rings 10: Conventional bridge collapse prevention buffer chain (current product) dA: Conventional ring connector 10: Bridge collapse prevention buffer chain A: (End) Ring B: (Adjacent) Ring R1: Ring connector R2: Conventional coating

Claims

1. A bridge collapse prevention buffer chain comprising a ring connector in which multiple rings are connected to each other, and a covering that covers the ring connector, connects a bridge superstructure such as a bridge girder to a bridge substructure such as a bridge abutment or bridge pier to prevent the bridge superstructure from falling, The ring connector is covered with the covering, except for a portion of the end ring at the end, and the end ring and the adjacent ring are in contact. The wire diameter of the ring steel material of at least one of the end rings and the adjacent rings is set to be larger than the wire diameter of the ring steel material of the other rings of the ring assembly. A bridge collapse prevention buffer chain featuring the following characteristics.

2. The wire diameter of the ring steel material of the adjacent ring is set to be larger than the wire diameter of the ring steel material of the other rings in the ring assembly. A bridge collapse prevention buffer chain according to claim 1, characterized by the above.

3. The aforementioned multiple rings are subjected to rust prevention treatment such as hot-dip galvanizing, followed by surface roughening treatment such as phosphoric acid treatment, and then covered with the aforementioned coating. A bridge collapse prevention buffer chain according to claim 1 or 2, characterized by the above.

4. The wire diameter of the ring steel material of the adjacent ring is set to be between 20% and 100% of the inner width of the end ring. A bridge collapse prevention buffer chain according to claim 2, characterized by the above.

5. The wire diameter of the ring steel material of the adjacent ring is set to be between 50% and 100% of the inner width of the end ring. A bridge collapse prevention buffer chain according to claim 2, characterized by the above.

6. The end ring and the adjacent ring are connected in a state of being twisted at a first angle, and the adjacent ring and the other rings of the ring connector covered by the covering are connected in a state of being twisted at a second angle, wherein the first angle and the second angle are different angles. A bridge collapse prevention buffer chain according to claim 1, characterized by the above.

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