ANTI-COLLAPSE BUFFER CHAIN FOR BRIDGE

Description

BACKGROUND

1. Technical Field

The present invention relates to an anti-collapse buffer chain for bridge for preventing a bridge girder from collapsing, and more specifically, relates to an anti-collapse buffer chain for bridge that enables the prevention of bridge collapse without fracture by interposing a buffer even when an impact load acts.

2. Related Art

A general bridge has a structure in which a bridge upper structure, such as a bridge girder, and a bridge lower structure, such as a bridge abutment and a bridge pier, are not rigidly joined, but they are joined by roller bearing, pin bearing, or the like via a bridge bearing member.

Moreover, from the aspect of preventing a major accident involving human lives, a bridge collapse prevention device that prevents the bridge upper structure from collapsing from the bridge lower structure is installed, and for this bridge collapse prevention device, the bridge upper structure is linked to the bridge lower structure with a wire rope, a chain, or the like.

Conventionally, as a bridge collapse prevention device of this type, there has been proposed a buffer chain in which rings are linked with a buffer, such as rubber, being interposed that absorbs impact so as to avoid fracture caused by an impact load transmitted when an earthquake or the like occurs.

For example, JP-A-9-242019 discloses a buffer chain in which one end of a cushioning member 5 formed into an approximately bar shape by burying rings 6 in an elastic body 7 in a state where a plurality of the rings 6 are mutually engaged with clearances provided so as to prevent the rings 6 from contacting one another and all the rings 6 are aligned in a straight line, and filling also the clearances with the elastic body 7 is fixed in the proximity of an end portion of a girder 2 by means of a linking member 11 and an anchoring member 10, and the other end is fixed at a bridge pier 1 or in the proximity of an end portion of an adjacent girder 2A by means of a linking member 9 and an anchoring member 8 (see claim 1 in the claims, paragraphs to in the specification, and FIG. 1 and FIG. 2 in the drawings in JP-A-9-242019).

However, the buffer chain described in JP-A-9-242019 is heavy in total weight since the length of the whole elastic body is long compared with the number of positions at which the elastic bodies are inserted between the rings that provide a buffer effect. Therefore, conveyance efficiency and operation efficiency are poor, and there has been a problem of increased operational costs of installation work and replacement work of the buffer chain. The buffer effect is also limited, and in order to increase the buffer effect, there has been a problem that the weight increases.

JP-A-2002-97607 discloses a chain for buffering in which enlarged rings 9, 9 are linked to both ends of a chain 8 and cushioning members 10, 10 formed of rubber or various kinds of synthetic resins and having an engagement portion 11 with a cross-sectional surface made of a depressed portion formed on an outer periphery are respectively inserted into these enlarged rings 9, 9 (see claim 1 in the claims, paragraphs [0017] to [0022] in the specification, and FIG. 1, FIG. 2, and FIG. 6 in the drawings in JP-A-2002-97607).

However, in the chain for buffering described in JP-A-2002-97607, the cushioning members 10 need to be inserted into two positions per chain, which requires time and effort, thus increasing operational costs, and moreover, depending on how an impact load is transmitted, the buffer effect may be deteriorated.

Furthermore, JP-A-2016-138416 discloses an anti-collapse buffer chain for bridge that includes a plurality of rings 21 to 25 linked to one another and prevents a bridge upper structure, such as a bridge girder H, from collapsing by linking the bridge upper structure to a bridge lower structure, such as a bridge abutment B and a bridge pier, proposed by the applicants of the present application. In the anti-collapse buffer chain for bridge, joining portions of the rings have peripheral areas solidified with a rubber elastic body 3 with four positions spaced apart, and the rubber elastic body 3 has a length falling within the length of four rings (see claim 1 in the claims, paragraphs to in the specification, FIG. 1 to FIG. 5 in the drawings, and the like in JP-A-2016-138416).

The anti-collapse buffer chain for bridge described in JP-A-2016-138416 has a function of reducing impact tensile force since the chains are not in direct contact. However, a current product (a conventional anti-collapse buffer chain for bridge 10) as an embodiment of the anti-collapse buffer chain for bridge described in JP-A-2016-138416 has an end ring A being in contact with an adjacent ring B from three aspects of (1) the transmission of impact force from the end ring A to a rubber covering body made by solidifying the peripheral area of the chain as a shockless portion with the rubber elastic body, (2) the fixation of the chain when the rubber covering body is vulcanization-molded, and (3) the securement of a space for passing a shackle through the end ring A during assembly.

However, when FEM analysis is performed on the conventional anti-collapse buffer chain for bridge 10 in which the end ring A is brought into contact with the adjacent ring B as the current product illustrated in FIG. 7 and FIG. 8 as illustrated in FIG. 9, it has been found that a stress concentrates on these end ring A and adjacent ring B when an impact load acts and the generated stress is locally high. In view of this, there has been expected the development of a new-type anti-collapse buffer chain for bridge that can simultaneously achieve the objects of (1) to (3) above while preventing the stress concentration on a contact portion between the end ring A and the adjacent ring B when the impact load acts.

Therefore, the present invention has been made in view of the problems above, and it is an object of the present invention to provide 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.

SUMMARY

An anti-collapse buffer chain for bridge according to claim 1 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 includes: 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. 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. 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.

In the anti-collapse buffer chain for bridge according to claim 2, which is in the anti-collapse buffer chain for bridge 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 another ring of the ring linked body.

In the anti-collapse buffer chain for bridge according to claim 3, which is in the anti-collapse buffer chain for bridge according to claim 1 or 2, 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.

In the anti-collapse buffer chain for bridge according to claim 4, which is in the anti-collapse buffer chain for bridge according to claim 2, 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.

In the anti-collapse buffer chain for bridge according to claim 5, which is in the anti-collapse buffer chain for bridge according to claim 2, 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.

In the anti-collapse buffer chain for bridge according to claim 6, which is in the anti-collapse buffer chain for bridge according to claim 1, 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.

With the first invention to the sixth invention, since the wire diameter of the ring steel materials of the end rings and the adjacent rings is set to be larger than the wire diameter of the ring steel materials of other rings of the ring linked body, stress concentration on a contact portion between the end ring and the adjacent ring is preventable when an impact load acts. Even when tensile force is preliminarily generated in the anti-collapse buffer chain for bridge, the stress concentration on the contact portion is reduced, thereby enabling a reduction in impact force.

In addition, with the first invention to the sixth invention, since the end ring and the adjacent ring are always in contact, the transmission of impact force from the end ring to the covering body can be smoothly achieved. Moreover, with the first invention to the sixth invention, since a pair of right and left end rings abut on the adjacent rings at inner sides thereof, only by applying tensile force (tension) to the pair of right and left end rings and interposing a spacer or the like between the respective rings, the chain can be easily fixed during vulcanization molding of the covering body, thereby shortening production time and enabling a reduction in production costs of the anti-collapse buffer chain for bridge. Furthermore, with the first invention to the sixth invention, abutting the end ring on the adjacent ring enables lengthening a projection length of the end ring projecting from the covering body, and, during assembly, a space for passing a shackle through the end ring can be secured.

In particular, with the second invention, without changing the size of the ring steel material of the end ring from the current product, the contact area between the end ring and the adjacent ring can be increased, thereby eliminating the necessity of a change in size of another related member, such as the size of the shackle, and an increase in production costs can be reduced while reducing stress concentration of impact force compared with the current product.

In particular, with the third invention, 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 improved, but the bonding strength of a rubber elastic body is also not deteriorated. In view of this, the corrosion resistance is improved while a buffer effect is maintained, thus enabling the improvement of durability. Time and effort for performing the rustproofing treatment on an exposed portion of the chain later can be saved.

In particular, with the fourth invention, since the wire diameter of the adjacent ring steel materials is set to from 20% to 100% of the inner surface width of the end ring, stress concentration on the contact portion can be reduced as well as the total weight can be reduced without significantly increasing the size of the covering body covering a part of the ring linked body.

In particular, with the fifth invention, the area of the contact portion between the end ring and the adjacent ring can be increased without changing the cover thickness of an elastic body of the covering body, and therefore, the stress concentration on the contact portion is more optimally reduceable.

In particular, with the sixth invention, the transmission of the impact load can be delayed, and energy of the impact load can be changed 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.

BRIEF DESCRIPTION OF THE DRAWINGS

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;

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

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

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;

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;

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

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;

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

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;

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

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;

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

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

DETAILED DESCRIPTION

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

First Embodiment

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.

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.

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.

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>

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.

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)

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 φ 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)

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.

These adjacent rings 22a, 22b are made of a commercially available type 2 chain with a diameter of the ring steel material of φ 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.

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.

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).

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 1
	Covering body
	ratio of
	comparative
	example A to B

		Assumption of initation of	φR
	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	φR
Chain	diameter	dameter	surface	diameter	diameter	diameter	surface	diameter	(comparative
type	φA	φB	width dA	φR	φA	φB	width dA	φR	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
⇒ Approximately 2.5 times of comparative example A
indicates data missing or illegible when filed

	TABLE 2
	Covering body
	ratio of
	comparative
	example A to B

		Assumption of initation of	φR
	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	φR
Chain	diameter	dameter	surface	diameter	diameter	diameter	surface	diameter	(comparative
type	φA	φB	width dA	φR	φA	φB	width dA	φR	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
⇒ Approximately 1.5 times of comparative example A
indicates data missing or illegible when filed

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 ΦA) and the wire diameters of the adjacent rings 22a, 22b (wire diameter ΦB), the inner surface widths of the end rings 21a, 21b (inner surface width dA), and the thicknesses of the covering body 3 (ΦR), 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 ΦA) and the inner surface width of the end rings 21a, 21b (the inner surface width dA) from the thickness of the covering body (ΦR) 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.

Furthermore, in Comparative Example A in Table 1, the wire diameter of the adjacent rings 22a, 22b (the wire diameter ΦB) is larger than the wire diameter of the end rings 21a, 21b (the wire diameter ΦA), 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 ΦB) is larger than the wire diameter of the end rings 21a, 21b (the wire diameter ΦA), 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 ΦB) 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 (ΦR) in Comparative Example B needs to be approximately 2.5 times or more of the thickness of the covering body (ΦR) in Comparative Example A.

In Comparative Example A in Table 2, the wire diameter of the adjacent rings 22a, 22b (the wire diameter ΦB) is larger than the wire diameter of the end rings 21a, 21b (the wire diameter ΦA), 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 ΦB) is larger than the wire diameter of the end rings 21a, 21b (the wire diameter ΦA), 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 ΦB) 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 (ΦR) in Comparative Example B needs to be approximately 1.5 times or more of the thickness of the covering body (ΦR) in Comparative Example A.

From Comparative Examples in Table 1 and Table 2, when the wire diameter of the adjacent rings 22a, 22b (the wire diameter ΦB) is larger than the wire diameter of the end rings 21a, 21b (the wire diameter ΦA), 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.

Meanwhile, setting the wire diameter of the adjacent rings 22a, 22b (the wire diameter ΦB) 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.

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 φ 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 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 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 φA	diameter φR	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 φB	n (≤φB/dA) fulfilling
dA = φR − 2(φA + t)	φB = φA + 1	dA × n % ≤ φB
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
		⇒30%
<Approximately 60% (boundary of stress concentration reduction effect)

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 ΦA) and the wire diameters of the adjacent rings 22a, 22b (the wire diameter ΦB), the inner surface widths of the end rings 21a, 21b (the inner surface width dA), and the thicknesses of the covering body 3 (ΦR), and shows the relations between the wire diameters of the end rings 21a, 21b (the wire diameter ΦA) and the wire diameters of the adjacent rings 22a, 22b (the wire diameter ΦB), 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 ΦA) and the inner surface width of the end rings 21a, 21b (the inner surface width dA) from the thickness of the covering body (ΦR) by two falls within 5 mm that is the minimum thickness providing the collapse prevention effect of the buffer chain.

As a condition of the thickness (t) of the covering body 3 falling within 5 mm, it can be seen that the wire diameter ΦB 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.

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.

From the results of Table 3 and Table 4, by setting the wire diameter ΦB 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.

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 φ 26 mm and φ 29 mm. However, when the diameter of the ring steel materials is set to φ 26 mm and φ 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 φ 25 mm.

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 φ 25 mm and the wire diameter of the ring steel materials of the adjacent rings 22a, 22b is set to φ 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)

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 φ 19 mm similarly to the end rings 21a, 21b.

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>

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.

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.

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).

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.

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.

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.

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.

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.

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

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.

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 α (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 α 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.

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 β (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 β may be a convenient angle different from the above-described predetermined angle α corresponding to the wire diameters of the adjacent ring 22a (22b) and the intermediate ring 23 (27) of the ring linked body 2.

Thus, the ring linked body 2 of the anti-collapse buffer chain for bridge 1′in 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.

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]

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·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·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.

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 φ 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.

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.

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.

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).

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.

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.

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.

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 φ 25 mm and the wire diameter of the ring steel materials of the adjacent rings 22a. 22b is φ 19 mm.