ANTI-COLLAPSE BUFFER CHAIN FOR BRIDGE

Abstract

Provided is an anti-collapse buffer chain for bridge that enables the prevention of stress concentration on a contact portion between rings when an impact load acts. In an anti-collapse buffer chain for bridge 1 that includes a ring linked body 2 in which a plurality of rings are linked to one another, and a covering body 3 covering a peripheral area of the ring linked body 2, and prevents a bridge upper structure, such as a bridge girder, from collapsing by linking the bridge upper structure to a bridge lower structure, such as a bridge abutment and a bridge pier, excluding a part of an end ring 21a (21b) at an end portion, the ring linked body 2 is covered with a rubber elastic body, the end ring 21a (21b) is brought into contact with an adjacent ring 22a (22b) that is adjacent to the end ring 21a (21b), and a wire diameter of a ring steel material of one or both rings of the end ring 21a (21b) and the adjacent ring 22a (22b) is set to be larger than a wire diameter of a ring steel material of another ring of the ring linked body 2.

Claims

1. An anti-collapse buffer chain for bridge that prevents a bridge upper structure, such as a bridge girder, from collapsing by linking the bridge upper structure to a bridge lower structure, such as a bridge abutment and a bridge pier, the anti-collapse buffer chain for bridge comprising: a ring linked body in which a plurality of rings are linked to one another; and a covering body covering a peripheral area of the ring linked body, wherein excluding parts of end rings at end portions, the ring linked body is covered with the covering body, and an adjacent ring adjacent to the end ring is in contact with the end ring, and a wire diameter of a ring steel material of at least one ring of the end ring and the adjacent ring is set to be larger than a wire diameter of a ring steel material of another ring of the ring linked body.

2. The anti-collapse buffer chain for bridge according to claim 1, wherein 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 another ring of the ring linked body.

3. The anti-collapse buffer chain for bridge according to claim 1, wherein the plurality of rings undergo a rustproofing treatment, such as hot dip galvanizing, then, undergo a rough surface treatment, such as a phosphoric acid treatment, and thereafter, are covered with the covering body.

4. The anti-collapse buffer chain for bridge according to claim 2 wherein the plurality of rings undergo a rustproofing treatment, such as hot dip galvanizing, then, undergo a rough surface treatment, such as a phosphoric acid treatment, and thereafter, are covered with the covering body.

5. The anti-collapse buffer chain for bridge according to claim 2, wherein the wire diameter of the ring steel material of the adjacent ring is set to from 20% to 100% of an inner surface width of the end ring.

6. The anti-collapse buffer chain for bridge according to claim 2, wherein the wire diameter of the ring steel material of the adjacent ring is set to from 50% to 100% of an inner surface width of the end ring.

7. The anti-collapse buffer chain for bridge according to claim 1, wherein the end ring and the adjacent ring are connected in a state of being twisted at a first angle, the adjacent ring and another ring of the ring linked body covered by the covering body are connected in a state of being twisted at a second angle, and the first angle and the second angle are different angles.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 is a perspective view illustrating a case where an anti-collapse buffer chain for bridge according to an embodiment of the present invention is linked to and put between a bridge abutment made of concrete and a bridge girder made of an H steel;

[0027] FIG. 2A is a frontal perspective view illustrating the same anti-collapse buffer chain for bridge as above;

[0028] FIG. 2B is a plan view illustrating the same anti-collapse buffer chain for bridge as above;

[0029] FIG. 3 is a cross-sectional view illustrating a contact state between an end ring and an adjacent ring of a ring linked body of the same anti-collapse buffer chain for bridge as above;

[0030] FIG. 4 is a graph showing the relation between static and dynamic tensile loads (kN) and the extension amount (mm) of a rubber portion by a tensile test;

[0031] FIG. 5 is a graph showing the relation between a tensile load (kN) and an absorption energy amount (kN.Math.m) by a static tensile test;

[0032] FIG. 6 is a graph showing the relation between a tensile load (kN) and a displacement (mm) of the test result of a static fracture test;

[0033] FIG. 7 is a frontal perspective view illustrating a conventional (current product) anti-collapse buffer chain for bridge;

[0034] FIG. 8 is a cross-sectional view illustrating a contact state between an end ring and an adjacent ring of a ring linked body of the same conventional (current product) anti-collapse buffer chain for bridge as above;

[0035] FIG. 9 is a drawing illustrating the FEM analysis result of stress concentration of the conventional (current product) anti-collapse buffer chain for bridge;

[0036] FIG. 10A is a vertical cross-sectional view illustrating a linking portion between an end ring and an adjacent ring of an anti-collapse buffer chain for bridge according to a second embodiment of the present invention;

[0037] FIG. 10B is a vertical cross-sectional view illustrating a linking portion between the adjacent ring and an intermediate ring of the anti-collapse buffer chain for bridge according to the second embodiment of the present invention; and

[0038] FIG. 11 is a frontal perspective view illustrating an anti-collapse buffer chain for bridge 1according to the embodiment.

DETAILED DESCRIPTION

[0039] The following describes an anti-collapse buffer chain for bridge according to embodiments of the present invention with reference to the drawings.

First Embodiment

[0040] With reference to FIG. 1 to FIG. 3, an anti-collapse buffer chain for bridge 1 according to a first embodiment of the present invention will be described. FIG. 1 is a perspective view illustrating a case where a steel girder H1 is linked to a bridge abutment P with the anti-collapse buffer chain for bridge 1 according to the embodiment of the present invention. FIG. 2A is a frontal perspective view illustrating the anti-collapse buffer chain for bridge 1 according to the embodiment, and FIG. 2B is a plan view illustrating the anti-collapse buffer chain for bridge 1 alone. FIG. 3 is a cross-sectional view illustrating a contact state between an end ring and an adjacent ring of a ring linked body 2 of the anti-collapse buffer chain for bridge 1.

[0041] As illustrated in FIG. 1, this anti-collapse buffer chain for bridge 1 is a shockless chain that links a bridge lower structure, such as the bridge abutment P and a bridge pier, to a bridge upper structure including the steel girder H1 of, for example, an H-shaped steel or an I-shaped steel via brackets B1, B2 in a state of sagging with a margin in length, and thus, has a function of absorbing and reducing impact force while preventing the bridge upper structure from collapsing from the bridge lower structure when a large earthquake occurs.

[0042] Note that the configuration illustrated in FIG. 1 exemplarily illustrates the case of linking the steel girder H1 made of an H steel as the bridge upper structure to the bridge abutment P made of reinforced concrete as the bridge lower structure. Note that while the illustrated configuration exemplarily illustrates the installation of one anti-collapse buffer chain for bridge 1, a plurality of anti-collapse buffer chains for bridge 1 may naturally be installed as necessary corresponding to the scale and the number of girders of the bridge.

[0043] The anti-collapse buffer chain for bridge 1 according to the embodiment is configured of, as illustrated in FIG. 2A and FIG. 2B, the ring linked body 2 as a chain main body made of a plurality of rings linked to one another, a covering body 3 formed of rubber, a resin material, or the like covering a part of this ring linked body 2, and the like.

<Ring Linked Body>

[0044] As illustrated in FIG. 2A and FIG. 2B, the ring linked body 2 is a ring linked body made of nine ring steel materials processed into oval shapes from a steel bar linked in a chain shape such that ring axes are at right angles to one another. Each of the ring steel materials of the ring linked body 2 according to the embodiment is made of a steel material, such as SWRM6, SWRM8, SWM-B, and SS400, and is processed into an oval shape and linked in a chain shape, thereby configuring the ring linked body 2. Surely, it is needless to say that the type of the steel material is not limited to those exemplarily described, and only needs to be appropriately selected corresponding to the size of the anti-collapse buffer chain for bridge 1.

[0045] This ring linked body 2 is made of a pair of right and left end rings 21a, 21b positioned at the outermost ends, adjacent rings 22a, 22b adjacent to these respective end rings 21a, 21b to be linked to the end rings 21a, 21b, and five intermediate rings 23 to 27 connecting the adjacent ring 22a to the adjacent ring 22b.

(End Ring)

[0046] As illustrated in FIG. 1, FIG. 2A, and FIG. 2B, the end rings 21a, 21b are ring steel materials having parts projecting from right and left end surfaces 3a in a circular shape of a columnar shape of a covering body described below, and linked to the chain connected to the bracket B1 and the bracket B2 via a shackle S1. The end rings 21a, 21b according to the embodiment are made of a ring steel material of a commercially available type 1 chain with a diameter of 19 mm. Surely, it is needless to say that the wire diameter of the steel material is not limited to that exemplarily described, and only needs to be appropriately selected depending on the size of the anti-collapse buffer chain for bridge 1.

(Adjacent Ring)

[0047] The adjacent rings 22a, 22b are positioned at adjacent positions at inner sides of these above-described end rings 21a, 21b, and linked to the respective end rings 21a, 21b to have a function of transmitting impact force when an earthquake occurs, which is input from the end rings 21a, 21b, to the covering body 3.

[0048] These adjacent rings 22a, 22b are made of a commercially available type 2 chain with a diameter of the ring steel material of 25 mm. That is, as illustrated in FIG. 2A and FIG. 2B, the ring steel materials of the adjacent rings 22a, 22b have a wire diameter set to be larger than the wire diameter of the ring steel materials of the above-described end rings 21a, 21b and the intermediate rings 23 to 27 described below.

[0049] As described in Background, the end rings 21a, 21b are preferably brought into contact with the adjacent rings 22a, 22b for three reasons of (1) transmitting the impact force to the covering body 3, (2) fixing the ring linked body 2 so as to be immobile until a rubber material or the resin material is hardened during vulcanization molding of the covering body 3, and (3) securing a space for inserting the shackle S1 through the end rings 21a, 21b. However, if the end rings 21a, 21b are in contact with the adjacent rings 22a, 22b, there has been a possibility of stress concentration on a contact portion between these end rings 21a, 21b and adjacent rings 22a, 22b when an impact load acts at the time of bridge collapse or the like, resulting in fracture.

[0050] Therefore, as illustrated in FIG. 3, in the anti-collapse buffer chain for bridge 1, the wire diameter of the ring steel materials of the adjacent rings 22a, 22b is made larger than the wire diameter of the ring steel materials of the end rings 21a, 21b, and thus, the length of the contact portion between the end rings 21a, 21b and the adjacent rings 22a, 22b is set to approximately 19 mm to make a contact area larger than the above-described current product (see FIG. 7 and FIG. 8), thereby reducing a contact pressure at the time of impact to reduce a risk of the fracture (also see FIG. 5).

[0051] Next, with reference to FIG. 3, and Table 1 and Table 2 below, an examination performed for the relations between the ring diameters of the chain and the diameters of the covering body 3 by simulations will be described.

TABLE-US-00001 TABLE 1 Covering body ratio of comparative example A to B Assumption of initation of R New type buffer chain new type buffer chain (comparative Comparative example A Comparative example B example B) Wire Wire Inner Rubber Wire Wire Inner Rubber R Chain diameter dameter surface diameter diameter diameter surface diameter (comparative type A B width dA R A B width dA R example A) 1 19 25 30 100 19 20 248 2.48 2 25 30 40 125 25 26 260 320 2.56 3 30 32 48 150 30 310 2.53 4 32 38 51 160 32 33 330 404 2.53 5 38 42 60 190 38 39 390 476 2.51 6 42 50 67 210 42 43 430 524 2.50 8 50 52 80 250 50 51 510 620 2.48 9 52 60 90 250 52 53 530 644 2.58 10 60 96 300 60 61 610 740 2.47 .Math. Approximately 2.5 times of comparative example A indicates data missing or illegible when filed

TABLE-US-00002 TABLE 2 Covering body ratio of comparative example A to B Assumption of initation of R New type buffer chain new type buffer chain (comparative Comparative example A Comparative example B example B) Wire Wire Inner Rubber Wire Wire Inner Rubber R Chain diameter dameter surface diameter diameter diameter surface diameter (comparative type A B width dA R A B width dA R example A) 1 19 25 30 100 19 20 100 1.48 2 25 30 40 125 25 26 190 1.52 3 30 32 45 150 30 31 155 225 1.50 4 32 38 51 160 32 33 165 239 1.49 5 38 42 60 190 38 39 195 281 1.48 6 43 50 67 210 42 43 309 1.47 8 50 52 80 250 50 51 255 365 1.46 9 52 60 80 250 52 265 379 1.52 10 60 96 300 60 61 305 435 1.45 .Math. Approximately 1.5 times of comparative example A indicates data missing or illegible when filed

[0052] Table 1 and Table 2 show effects the relations between the wire diameters of the adjacent rings 22a, 22b and the inner surface widths of the end rings 21a, 21b have on the thicknesses of the covering body 3. Comparative Examples A and B shown in Table 1 and Table 2 show the wire diameters of the end rings 21a, 21b (wire diameter A) and the wire diameters of the adjacent rings 22a, 22b (wire diameter B), the inner surface widths of the end rings 21a, 21b (inner surface width dA), and the thicknesses of the covering body 3 (R), and have a thickness (t) obtained by dividing the thickness of the covering body obtained by deducting the wire diameter of the end rings 21a, 21b (the wire diameter A) and the inner surface width of the end rings 21a, 21b (the inner surface width dA) from the thickness of the covering body (R) by two, where the thickness (t) is 5 mm that is the minimum thickness necessary for covering in the production of the anti-collapse buffer chain for bridge.

[0053] Furthermore, in Comparative Example A in Table 1, the wire diameter of the adjacent rings 22a, 22b (the wire diameter B) is larger than the wire diameter of the end rings 21a, 21b (the wire diameter A), and is approximately 60% of the inner surface width of the end rings 21a, 21b (the inner surface width dA), whereas in Comparative Example B in Table 1, the wire diameter of the adjacent rings 22a, 22b (the wire diameter B) is larger than the wire diameter of the end rings 21a, 21b (the wire diameter A), and the inner surface width of the end rings 21a, 21b (the inner surface width dA) is set such that the wire diameter of the adjacent rings 22a, 22b (the wire diameter B) is 10% or less of the inner surface width of the end rings 21a, 21b (the inner surface width dA). In Comparative Example B in Table 1, the thickness of the covering body 3 (R) in Comparative Example B needs to be approximately 2.5 times or more of the thickness of the covering body (R) in Comparative Example A.

[0054] In Comparative Example A in Table 2, the wire diameter of the adjacent rings 22a, 22b (the wire diameter B) is larger than the wire diameter of the end rings 21a, 21b (the wire diameter A), and is approximately 60% of the inner surface width of the end rings 21a, 21b (the inner surface width dA), whereas in Comparative Example B in Table 1, the wire diameter of the adjacent rings 22a, 22b (the wire diameter B) is larger than the wire diameter of the end rings 21a, 21b (the wire diameter A), and the inner surface width of the end rings 21a, 21b (the inner surface width dA) is set such that the wire diameter of the adjacent rings 22a, 22b (the wire diameter B) is 20% or less of the inner surface width of the end rings 21a, 21b (the inner surface width dA). In Comparative Example B in Table 1, the thickness of the covering body 3 (R) in Comparative Example B needs to be approximately 1.5 times or more of the thickness of the covering body (R) in Comparative Example A.

[0055] From Comparative Examples in Table 1 and Table 2, when the wire diameter of the adjacent rings 22a, 22b (the wire diameter B) is larger than the wire diameter of the end rings 21a, 21b (the wire diameter A), and is less than 20% of the inner surface width of the end rings 21a, 21b (the inner surface width dA), the total length in a short side direction of the adjacent rings 22a, 22b is larger than the thickness in a short side direction of the covering body 3, and therefore, the thickness of the covering body needs to be increased by 1.5 times or more, thereby increasing the size of the covering body 3.

[0056] Meanwhile, setting the wire diameter of the adjacent rings 22a, 22b (the wire diameter B) to be a length of at least 20% or more of the inner surface width of the end rings 21a, 21b (the inner surface width dA) allows a reduction of stress concentration on the contact portion as well as a reduction in the total weight without increasing the size of the covering body 3 covering a part of the ring linked body 2.

[0057] Next, a further examination is performed with a type 6 having a large difference from the larger wire diameter. Table 3 below shows calculations of Hertz surface pressure with a B wire diameter being set to the smallest 43 mm and an A inner surface width being varied. In order to examine the cover thickness of the rubber of the covering body 3, the minimum necessary cover thickness of the rubber is set to 5 mm, and the range of the B wire diameter with which this cover thickness falls below is examined and shown in Table 4.

TABLE-US-00003 TABLE 3 A wire A inner B wire Hertz surface diameter surface width diameter pressure mm mm mm N/mm2 Comparative 42 67 42 40 example A Comparative 42 70 43 40 example B 42 71 43 40 42 72 43 41 42 73 43 41 42 74 43 41 42 75 43 42 42 76 43 42 42 77 43 42 42 78 43 43 42 79 43 43 42 80 43 43 42 100 43 48 42 120 43 51

TABLE-US-00004 TABLE 4 n % of A inner surface width to B wire diameter 100% of A inner surface width From approved drawing of current buffer chain Chain Wire Rubber Inner surface type diameter A diameter R width dA 1 19 100 30 2 25 125 40 3 30 150 48 4 32 160 51 5 38 190 60 6 42 210 67 8 50 250 80 9 52 250 80 10 60 300 96 dA where t = 5 Smallest B n (B/dA) fulfilling dA = R 2(A + t) B = A + 1 dA n % B 52 20 0.385 65 26 0.400 80 31 0.388 86 33 0.384 104 39 0.375 116 43 0.371 140 51 0.364 136 53 0.390 170 61 0.359 .Math.30%

[0058] Table 4 shows the relations between the wire diameters of the adjacent rings 22a, 22b and the inner surface widths of the end rings 21a, 21b with which the cover thicknesses of the covering body 3 fall within the minimum necessary range. Table 4 shows the wire diameters of the end rings 21a, 21b (the wire diameter A) and the wire diameters of the adjacent rings 22a, 22b (the wire diameter B), the inner surface widths of the end rings 21a, 21b (the inner surface width dA), and the thicknesses of the covering body 3 (R), and shows the relations between the wire diameters of the end rings 21a, 21b (the wire diameter A) and the wire diameters of the adjacent rings 22a, 22b (the wire diameter B), and the inner surface widths of the end rings 21a, 21b (the inner surface width dA) with which the thickness (t) obtained by dividing the thickness of the covering body obtained by deducting the wire diameter of the end rings 21a, 21b (the wire diameter A) and the inner surface width of the end rings 21a, 21b (the inner surface width dA) from the thickness of the covering body (R) by two falls within 5 mm that is the minimum thickness providing the collapse prevention effect of the buffer chain.

[0059] As a condition of the thickness (t) of the covering body 3 falling within 5 mm, it can be seen that the wire diameter B of the adjacent rings 22a, 22b needs to be at least 35% or more of the inner surface width dA of the end rings 21a, 21b.

[0060] As shown in Table 3, Comparative Example B that shows respective Hertz surface pressures by setting the wire diameter of the end rings 21a, 21b (the A wire diameter) to 42 mm and the wire diameter of the adjacent rings 22a, 22b (the B wire diameter) to 43 mm, and varying the A inner surface width (dA) is compared with Comparative Example A that shows a Hertz surface pressure by setting the wire diameter of the end rings 21a, 21b (the A wire diameter) and the wire diameter of the adjacent rings 22a, 22b (the B wire diameter) to 42 mm, and the inner surface width of the end rings 21a, 21b (the A inner surface width) to 67 mm. It can be seen from the comparison result that the wire diameter with which the Hertz surface pressure is larger than that of Comparative Example A has an A inner surface width of 72 mm or more and the wire diameter PA of the adjacent rings 22a, 22b is 50% or more of the inner surface width dA of the end rings 21a, 21b.

[0061] From the results of Table 3 and Table 4, by setting the wire diameter B of the adjacent rings 22a, 22b to be a length of at least 50% to 100% of the inner surface width dA of the end rings 21a, 21b, the area of the contact portion between the end rings 21a, 21b and the adjacent rings 22a, 22b is increased without varying the cover thickness of the elastic body of the covering body, and therefore, the stress concentration on the contact portion is more optimally reduced, thereby enabling a reduction in impact force.

[0062] Here, it is considered to further increase the wire diameter of the ring steel materials of the adjacent rings 22a, 22b to set the diameter of the ring steel materials to 26 mm and 29 mm. However, when the diameter of the ring steel materials is set to 26 mm and 29 mm, taking the minimum necessary cover thickness of the rubber elastic body being 5 mm into consideration, the ring steel material fails to be housed within a column having a diameter of 100 mm of the covering body 3 the same as the current product, and the covering body 3 needs to be increased in size. In view of this, in order to avoid an increase in production costs and reduced work efficiency due to the weight increase, the wire diameter of the ring steel materials of the adjacent rings 22a, 22b preferably has a diameter of 25 mm.

[0063] Surely, it is considered that a similar effect can be provided even when the wire diameter of the ring steel materials of the end rings 21a, 21b is set to 25 mm and the wire diameter of the ring steel materials of the adjacent rings 22a, 22b is set to 19 mm since the stress concentration of impact force is reduced when the area of the contact portion between the end rings 21a, 21b and the adjacent rings 22a, 22b is increased.

(Intermediate Ring)

[0064] The intermediate rings 23 to 27 have a function of connecting the adjacent ring 22a to the adjacent ring 22b and transmitting impact force between the end ring 21a and the end ring 21b. The ring steel materials of these intermediate rings 23 to 27 are made of ring steel materials of a commercially available type 1 chain having a diameter of each ring steel material of 19 mm similarly to the end rings 21a, 21b.

[0065] As illustrated in FIG. 2A and FIG. 2B, excluding the contact portion between the end rings 21a, 21b and the adjacent rings 22a, 22b, the ring linked body 2 is covered with the covering body 3 and solidified in a state where the ring steel materials are spaced apart by a clearance D1 (in this embodiment, D1 equivalent to the diameter of the ring steel material=approximately 23 mm).

<Covering Body>

[0066] As illustrated in FIG. 2A and FIG. 2B, the covering body 3 according to the embodiment covers a part of the ring linked body 2, is made of a rubber elastic body formed into a columnar shape having a diameter of approximately 100 mm, and is large in resistive power and repulsion force, and therefore, hard rubber made by mixing natural rubber and synthetic rubber and vulcanizing the mixture is employed. Note that while the covering body 3 is preferably made of hard rubber high in weather resistance and UV resistance, anything made of a rubber elastic body with buffer action on an impact load may be employed. As long as the buffer action on an impact load is provided, the covering body 3 may be configured of an elastoplastic body, a viscoelastic body, or another elastic body, such as a resin material.

[0067] The shape of the covering body 3 is not limited to the columnar shape, and as long as a part of the ring linked body 2 is covered and solidified with a predetermined clearance, the shape of, for example, an outer shape, such as a prismatic shape and a cruciform cross section, is not particularly limited.

[0068] Note that the rubber elastic body here indicates an object that exhibits rubber elasticity that has a Young's modulus at ordinary temperature of approximately 1 to 10 MPa, allows largely extending without fracture by a small stress, and moreover, allows returning to the original shape almost instantaneously on removing external force. The hard rubber indicates a rubber elastic body having a hardness by a durometer hardness test (type A) of Japanese Industrial Standard K6253 of 70 or more by adding a large amount of sulfur to raw rubber, such as chloroprene (CR) rubber, nitrile rubber (NRB), ethylene propylene diene monomer (EPDM), and styrene-butadiene rubber (SBR).

[0069] The ring linked body 2 is hot dip galvanized, then, the part to be covered with the rubber elastic body is treated with phosphoric acid, and thereafter, the anti-collapse buffer chain for bridge 1 is covered with the covering body 3 made of the rubber elastic body and is solidified. In view of this, the anti-collapse buffer chain for bridge 1 has a bonding strength of the covering body 3 to the ring linked body 2 as good as a case without plating, and has a high buffering effect of impact absorption. In addition, time and effort for performing a rustproofing treatment on an exposed portion after covering can be eliminated.

[0070] Note that, while hot dip galvanizing has been exemplarily described as the rustproofing treatment of the ring linked body 2, the rustproofing treatment of the ring linked body is not limited to hot dip galvanizing, and, for example, any other rustproofing treatment, such as electroplating, electroless plating, and vapor deposition, is allowed. Basically, any treatment is allowed as long as it can prevent the ring linked body 2 from rusting for a desired period or more. The phosphoric acid treatment is a rough surface treatment making the surface of the ring linked body 2 a rough surface, but the treatment is not limited to the phosphoric acid treatment as long as the treatment improves bonding strength between the ring linked body 2 and the rubber elastic body.

[0071] With the anti-collapse buffer chain for bridge 1 according to the embodiment of the present invention described above, the end ring 21a (21b) is always in contact with the adjacent ring 22a (22b), and therefore, the transmission of impact force from the end ring 21a (21b) to the covering body 3 is smoothly achievable. Moreover, with the anti-collapse buffer chain for bridge 1, the pair of right and left end rings 21a, 21b abut on the adjacent ring 22a (22b) at the inner side thereof, and therefore, only by applying tensile force (tension) to the pair of right and left end rings 21a, 21b and interposing a spacer or the like between respective rings, the chain of the ring linked body 2 can be easily fixed during vulcanization molding of the covering body 3, thereby shortening production time and enabling a reduction in production costs of the anti-collapse buffer chain for bridge.

[0072] With the anti-collapse buffer chain for bridge 1, abutting the end ring 21a (21b) on the adjacent ring 22a (22b) enables lengthening a projection length of the end ring 21a (21b) projecting from the covering body 3. In view of this, during assembly of linking the bridge lower structure, such as the bridge abutment P, to the bridge upper structure including the steel girder H1 via the brackets B1, B2, a space for passing the shackle S1 through the end ring 21a (21b) can be secured.

[0073] Moreover, with the anti-collapse buffer chain for bridge 1, only the adjacent ring 22a (22b) is increased in size, and therefore, without changing the size of the ring steel material of the end ring 21a (21b) from the current product, the contact area between the end ring 21a (21b) and the adjacent ring 22a (22b) can be increased, thereby eliminating the necessity of a change in size of another related member, such as the size of the shackle S1. In view of this, the anti-collapse buffer chain for bridge 1 can reduce an increase in production costs while reducing stress concentration of impact force compared with the conventional anti-collapse buffer chain for bridge 10.

[0074] Furthermore, in the anti-collapse buffer chain for bridge 1, the rustproofing treatment, such as hot dip galvanizing, is performed, then, the rough surface treatment, such as a phosphoric acid treatment, is performed, and therefore, not only is the corrosion resistance of the chain of the ring linked body 2 improved, but the bonding strength of the rubber elastic body of the covering body 3 is also not deteriorated. In view of this, the corrosion resistance is improved while the buffer effect is maintained, thus enabling the improvement of durability. Time and effort for performing the rustproofing treatment on the exposed portion of the chain later can be saved.

Second Embodiment

[0075] Next, with reference to FIG. 10A, FIG. 10B, and FIG. 11, an anti-collapse buffer chain for bridge 1 according to a second embodiment of the present invention will be described. The anti-collapse buffer chain for bridge 1 according to the second embodiment is different from the above-described anti-collapse buffer chain for bridge 1 according to the first embodiment only in that the respective rings of the ring linked body are linked in a state of rotating about an axis of the covering body 3 and being mutually twisted, and therefore, the description is mainly given on this point, and the other configurations are not described. FIG. 10A is a vertical cross-sectional view illustrating a linking portion between the end ring 21a (21b) and the adjacent ring 22a (22b) of the anti-collapse buffer chain for bridge 1 according to the second embodiment of the present invention, and FIG. 10B is a vertical cross-sectional view illustrating a linking portion between the adjacent ring 22a (22b) and the intermediate rings 23 to 27 of the anti-collapse buffer chain for bridge 1 according to the second embodiment of the present invention. FIG. 11 is a frontal perspective view illustrating the anti-collapse buffer chain for bridge 1 according to the embodiment.

[0076] As illustrated in FIG. 10A and FIG. 10B, the anti-collapse buffer chain for bridge 1 has the end ring 21a (21b) and the adjacent ring 22a (22b) of the ring linked body 2 twisted from a vertical state of being perpendicular to axes of the intermediate rings 23 to 27 to a state of being inclined by a predetermined angle (in this embodiment, 22.5 degrees) as a first angle, and the peripheral area of the ring linked body 2 is solidified and covered with the covering body 3 in this state. The predetermined angle may be another convenient angle corresponding to the wire diameters of the end ring 21a (21b) and the adjacent ring 22a (22b) of the ring linked body 2.

[0077] Furthermore, the intermediate ring 23 (27) linked to the adjacent ring 22a (22b) may be twisted from the vertical state of being perpendicular to the axes of the intermediate rings 23 to 27 to a state of being inclined by a predetermined angle (in this embodiment, 23 degrees) as a second angle, and the peripheral area of the ring linked body 2 may be solidified and covered with the covering body 3 in this state. The predetermined angle may be a convenient angle different from the above-described predetermined angle corresponding to the wire diameters of the adjacent ring 22a (22b) and the intermediate ring 23 (27) of the ring linked body 2.

[0078] Thus, the ring linked body 2 of the anti-collapse buffer chain for bridge 1in the state where a part of the ring is twisted is in the state where its peripheral area is covered by the covering body 3, and therefore, when an impact load is transmitted to the anti-collapse buffer chain for bridge 1, the rings 21a (21b) to 22a (22b) of the ring linked body 2 attempt to move away by its tensile force.

[0079] Then, the rings 23, 25 attempt to rotate in a direction in which the twist of the ring linked body 2 is inevitably released, that is, in an opposite direction of the arrows in FIG. 10A, FIG. 10B, and FIG. 11. At this time, the rings 23, 25 attempt to press and rotate only a part of the covering body 3 in the peripheral area. In view of this, the anti-collapse buffer chain for bridge 1 according to the second embodiment enables delaying the transmission of the impact load, and changing energy of the impact load to kinetic energy to consume and absorb the kinetic energy. Thus, the buffer effect of absorbing the impact load when an earthquake occurs can be improved.

[Confirmation Test]

[0080] Next, with reference to FIG. 4 to FIG. 6, a tensile test that was performed for confirming the advantageous effects of the present invention and confirmed the relation between an extension amount (mm), an absorption energy amount (kN.Math.m), and a displacement (mm) of the rubber portion when a load (kN) was added to each tested object will be described. FIG. 4 is a graph showing the relation between static and dynamic tensile loads (kN) and the extension amount (mm) of the rubber portion by the tensile test, and FIG. 5 is a graph showing the relation between the tensile load (kN) and the absorption energy amount (kN.Math.m) by a static tensile test. FIG. 6 is a graph showing the relation between the tensile load (kN) and the displacement (mm) of the test result of a static fracture test.

[0081] For the tested object, the conventional anti-collapse buffer chain for bridge 10 illustrated in FIG. 7 and FIG. 8 was fabricated as a current example (current product). A ring linked body R1 of the anti-collapse buffer chain for bridge 10 was a ring linked body in which eleven ring steel materials made of a commercially available type 1 chain all having a diameter of 19 mm were linked. Each of the ring steel materials of the ring linked body R1 was installed with a predetermined clearance D1=23 mm to reduce impact tensile force, and a rubber elastic body of a covering body R2 was interposed therebetween. The covering body R2 was a columnar body with a diameter of 100 mm, and had a length of 699.1 mm.

[0082] As an example (example product 1), the above-described anti-collapse buffer chain for bridge 1 illustrated in FIG. 2A, FIG. 2B, and FIG. 3 was fabricated. As described above, the ring linked body 2 of the anti-collapse buffer chain for bridge 1 had only the wire diameter of the ring steel materials of the adjacent rings 22a, 22b increased in size to a commercially available type 2 chain with a diameter of q 25 mm to set the contact area between the end rings 21a, 21b and the adjacent rings 22a, 22b to be larger than the above-described current product (see FIG. 7 and FIG. 8), in order to fall within the length of the covering body R2 of the current product, the number of the ring steel materials was decreased compared with the ring linked body R1, and the ring linked body 2 of the anti-collapse buffer chain for bridge 1 was configured of nine ring steel materials in total. The covering body 3 was a columnar body with a diameter of 100 mm, and had a length of 694.8 mm.

[0083] An anti-collapse buffer chain for bridge having approximately the same configuration as the above-described anti-collapse buffer chain for bridge 1 was fabricated as a comparative example (example product 2). The comparative example (example product 2) was only different from the example (example product 1) in that, while the example (example product 1) had a clearance D1=23 mm between the ring steel materials of the adjacent ring 22a and the intermediate ring 23, and the adjacent ring 22b and the intermediate ring 27, the comparative example (example product 2) had a clearance D2=37 mm between the ring steel materials of the adjacent ring 22a and the intermediate ring 23, and the adjacent ring 22b and the intermediate ring 27, and while the example (example product 1) had an clearance D1=22 mm between the ring steel materials of the intermediate ring 24, the intermediate ring 25, and the intermediate ring 26, the comparative example (example product 2) had a clearance D3=33 mm between the ring steel materials of the intermediate ring 24, the intermediate ring 25, and the intermediate ring 26. In view of this, the covering body 3 was columnar body with a diameter of 100 mm, and had a length of 698.0 mm.

[0084] As illustrated in FIG. 4, an apparent correlation is recognizable in the results of the static tensile test and the dynamic tensile test. Accordingly, from the static tensile test from which detailed continuous data is easily obtainable, a dynamic test result close to the usage configuration of the anti-collapse buffer chain for bridge 1 according to the present invention is considered to be estimated. As indicated by the arrow in the drawing, an increase in spring stiffness is observed in the example (example product 1) and the comparative example (example product 2) compared with the current example (current product).

[0085] As illustrated in FIG. 5, while it is estimated that the generated load of the current example is lowered when the same input energy is input to each tested object at the time of impact within the range of a small impact load up to 53 kN as indicated by the arrow in the graph, it is estimated that the generated load of the comparative example is smaller than that of the current example within the range of a large impact load exceeding 53 kN. That is, it is observed that the load lowers in the comparative example (example product 2) compared with the current example (current product) when the input energy is large.

[0086] As illustrated in FIG. 6, the test results of the static fracture test had the maximum load at the time of fracture of 383.5 kN and an extension at the time of fracture of 344.8 mm for the current example (current product), the maximum load at the time of fracture of 379.0 kN and an extension at the time of fracture of 205.8 mm for the example (example product 1), and the maximum load at the time of fracture of 380.0 kN and an extension at the time of fracture of 261.5 mm for the comparative example (example product 2). In view of this, even though the absorption energy amounts are different since the numbers of the links of the chains are different and the extensions at the time of fracture are different, it is observed that there is no significant difference in maximum load in any specimens.

[0087] Fracture positions of the specimens of the example (example product 1) and the comparative example (example product 2) were not the contact portions between the end rings 21a, 21b and the adjacent rings 22a, 22b. Accordingly, it was confirmed that the presence of a chain with a different diameter in the anti-collapse buffer chain for bridge 1 according to the embodiment of the present invention does not lead to a weakness, and stress concentration on the contact portion of the rings when an impact load acts can be prevented.

[0088] While the anti-collapse buffer chain for bridge 1 according to the embodiment of the present invention has been described in detail above, any of the embodiments described above or illustrated are merely illustrations of one embodiment embodied for executing the present invention, and the technical scope of the present invention should not be construed in a limited way by these embodiments. In particular, while the ring steel materials of the adjacent rings 22a, 22b increased in size so as to increase the area of the contact portion between the end rings 21a, 21b and the adjacent rings 22a, 22b have been exemplarily described, it is allowed that the wire diameter of the ring steel materials of one or both of the rings of the end ring 21a (21b) and the adjacent ring 22a (22b) is set to be larger than the wire diameter of the other ring steel materials such that the wire diameter of the ring steel materials of the end rings 21a. 21b is 25 mm and the wire diameter of the ring steel materials of the adjacent rings 22a. 22b is 19 mm.