CA2195418A1 - Reinforcing bar for frp concrete - Google Patents
Reinforcing bar for frp concreteInfo
- Publication number
- CA2195418A1 CA2195418A1 CA 2195418 CA2195418A CA2195418A1 CA 2195418 A1 CA2195418 A1 CA 2195418A1 CA 2195418 CA2195418 CA 2195418 CA 2195418 A CA2195418 A CA 2195418A CA 2195418 A1 CA2195418 A1 CA 2195418A1
- Authority
- CA
- Canada
- Prior art keywords
- bending
- frp
- reinforcement
- concrete according
- concrete
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/07—Reinforcing elements of material other than metal, e.g. of glass, of plastics, or not exclusively made of metal
Abstract
A reinforcing bar for FRP concrete having one or more bent portions in which the cross section thereof is shaped substantially into a rectangular in such a manner that the relationship between the thickness t and width w thereof is expressed by t/w1.
Description
219~glg SPECIFICATION
FRP REINFORCEMENT FOR CONCRETE
TECHN~ r. FJFr~n The present invention relates to a FRP (Fiber Reinforced Plastic) reinLuL, ~ for a uulluL~L~. More specifically, the present invention relates to a FRP
reinforcement for a concrete such as a stirrup reinforcement for a concrete, a hoop reinfuL~~ L for a concrete or the like, in which a bending work is carried out in accordance with a sectional shape of a concrete structure.
BAC~CR9UND ART
As a reinfu~ for a ~ulluL~L~, such as a conventional stirrup reinfuLu, L, hoop reinfuL, nt or the like, which is used by bending, a steel reinruLu. t has been generally used. However, in a case where the sea sands in which salt ul , ~nt and so forth still remains comes to be mixed with a concrete, or in a case where a crack or so forth can be caused in the conorete construotion under a severe salt , ,~n~nt environment, there arises a problem of corroslon of the above-mentioned reinLuL~ t for the uull~L~L~, which ~ 2195418 occurs by an ~poc1ng of the concrete to the salt.
Thus, in the recent years, corrosion reslstlve FRP
rods have been used as the substitute for the steel reinfol~ t.
As the reinfui~, ~, such as a conventional FRP
stirrup, hoop or the like, which is bent is described in for example, Japanese Un~Am I n~ Patent Publication (Kokai) No. Hei 6-136882, the reinLoL, t is produced by the steps of (1) inserting a matrix resin impregnated carbon fiber into a fl~1cl hl ~ tube;
FRP REINFORCEMENT FOR CONCRETE
TECHN~ r. FJFr~n The present invention relates to a FRP (Fiber Reinforced Plastic) reinLuL, ~ for a uulluL~L~. More specifically, the present invention relates to a FRP
reinforcement for a concrete such as a stirrup reinforcement for a concrete, a hoop reinfuL~~ L for a concrete or the like, in which a bending work is carried out in accordance with a sectional shape of a concrete structure.
BAC~CR9UND ART
As a reinfu~ for a ~ulluL~L~, such as a conventional stirrup reinfuLu, L, hoop reinfuL, nt or the like, which is used by bending, a steel reinruLu. t has been generally used. However, in a case where the sea sands in which salt ul , ~nt and so forth still remains comes to be mixed with a concrete, or in a case where a crack or so forth can be caused in the conorete construotion under a severe salt , ,~n~nt environment, there arises a problem of corroslon of the above-mentioned reinLuL~ t for the uull~L~L~, which ~ 2195418 occurs by an ~poc1ng of the concrete to the salt.
Thus, in the recent years, corrosion reslstlve FRP
rods have been used as the substitute for the steel reinfol~ t.
As the reinfui~, ~, such as a conventional FRP
stirrup, hoop or the like, which is bent is described in for example, Japanese Un~Am I n~ Patent Publication (Kokai) No. Hei 6-136882, the reinLoL, t is produced by the steps of (1) inserting a matrix resin impregnated carbon fiber into a fl~1cl hl ~ tube;
(2) bending the obtained tube with the matrix resin;
(3) after curing the matrix resin; and (4) removing the fl~ hl e tube to obtain an article.
However, when the curvature of the above-mentioned conventional reinforcement for the concrete is large, it is difficult to increase the strength of the reinfol~ ~ around the bending worked portion. Namely, (1) To increase the strength thereof it i8 necessary to increase the sectional area thereof. Then, the difference between the inside length of the bending worked portion and the outside length thereof becomes large. Thus, a relnforcing fiber bundle of a portion around the lnside bending worked portion is sub~ected to a strong compression force so that the inside bending ~ 219~4~8 worked portion has a wrinkle, in the result, the reinforcing fiber orientation is disarranged and the strength of the bending worked portion is remarkably lowerea .
(2) Further, the disarrangement is advanced to the straight portion of the reinful, ~ for the concrete, with the result that even the tensile strength of the straight portion thereof is lowered.
(3) Full- ~, when it is sub~ected to a bending work, a bending worked portion is crushed and it is lmposslble to maintain such clrcular sectlonal shape thereln that the straight portion of the reinLulc~ t has. Thus, the sectional shape is warped and the ~ ~r of the entire reinfulu ~ becomes ununiform. This leads to a stress concentration which results in a cause of lowering the strength of the reinfu~
As ~Yrl ~ 1 n~d above, the conventlonal FRP
reinforcement for the concrete has been produced as a substitute for a conventional steel rod. Therefore, the sectlonal shape of the former is circular. As a result, when partlcularly, the bendlng radius ls made small, the strength of the reinfulu ~ ls l~ Ihly lowered.
Therefore, taklng the above-mentioned problems into consideration, it is an ob~ect of the present invention to provide a FRP reinfvl~ ~ for a concrete in which ~ 21g~41g even when the sectional area of the reinL~l~, L i8 large and the bending radius thereof~is small, namely, the curvature thereof is large, a sufficient ~ LL~ Lh of the bending worked portion thereof can be obtained, and also a strength of the straight portion which continues to the bending worked portion can be sllff;r.;Pntly obtained.
DISCLOSURE OF THE INV~NTION
In order to a~, ,li~h the above-mentloned ob~ect of the present invention, according to an aspect of the present invention, there is provided a FRP reinLull - t for a concrete having one or more bending worked portions characteri~ed in that a shape of the section of the reinforcement is substantially rectangular so that the relationship between the th; r.knP~ t and the width w satisfies t/w < 1.
According to the above-mentioned constitution, a section of a FRP reinf~L, t for a ~ull~L-te is substantially rectangular. Therefore, the th~rkn~e~ of the reinL~L~, L can be decreased without changing the sectional area thereof. Thus, a difference between the outside surface length and the inside surface length of the bending worked portion of the reinruL, t is decreased, so that a reinforcing fiber bundle passing through around the inslde of the bending worked portion is subjected to only a small compression force. In the result, the disarrangement of the fiber is not generated, 80 that the ~L~ny~h decrease of the bending worked portion is small.
In the above-mentioned constitution, it is preferable that the relationship between the bending radius R of the inside surface of the bending worked portion and the th~r.kn~.cs t satisfies R/t 2 2.8.
Further, in the above constitution, it is also preferable that when bending directions of adjoining bending worked portions are the same, the length L of the straight portion between the adjoining bending worked portions satisfies L 2 3,5 X R X ~ + 3,5 X R~ X ~
in which the bending radiuses and bending angles Of adjoining bending worked portions are respectively R, and R', ~'.
Further, the substantial rectangle may have outwardly curved short sides or an oval shape.
DRIEF DESCRIPTION QF THE ~RAWINGS
The present invention will be un~eL~o~d more fully from the detailed description given hereinbelow and from a~ ~ ying drawings of the preferred embodiments of the ? .
~ 219~418 ., invention, which, however, should not be taken to be limitatlve to the invention, but are for explanation and understanding only.
In the drawings:
Figs. lA and lB show one embodiment of a FRP
reinful~ ~ for a concrete according to the present invention, in which Fig. lA iS a sectional view, and Fig.
lB is a side view;
Figs. 2A to 2C show a change of a state and the orientation angle on a bending action for a reinforcing fiber in the bending worked portion of the above-mentioned embodiment, in which Fig. 2A is a diagram illustrating the state before bending work of the reinf~" t, Fig. 2B is a diagram illustrating a state where a wrinkle is made by bending work, and Fig. 2C is a diagram illustrating calculation of the orientation angle;
Fig. 3 is a diagram illustrating the tensile strength to the orientation angle in the above-mentioned embodiment of the present invention;
Fig. 4 is a side view illustrating a FRP
reinfoL, t for a ~ in which bending directions of adjoining portions are different from each other, as another ~mhn~ t of the present invention;
Fig.s 5A and 5B show a first e~perimental example of ~ 219S418 the present invention, in which Fig. 5A is a side view, and Fig. 5B is a sectional view taken along line C-C of Fig. 5A;
Fig. 6 is a side view of a second experimental example of the present invention; and Fig. 7 i8 a sectional view of a third ~pPr~r-ntal example of the present invention.
BEST ~QDF FDR I~PL~ENTTNG TH~ IN~NTION
A FRP reinforcement for a concrete according to a preferred embodiment of the present invention will be described below with reference to the ~ ~ yLng drawings.
As shown in Fig. lA, a FPR reinfuL, ~ for a concrete 1 has a substantially rectangular section with a ~hl rkn~q~ of t and a width of w. The opposite short sides of the rectangular section are curved outside.
When the FPR reinforcement for the ~UII~L~tU 1 is sub~ected to a bending work so as to have the inside surface bending radius R and the inside surface bending angle ~, as shown in Fig. lB, (1) the compression force acts on the inner side portion from the center line 2 across the bending worked portion A and the inner side portion is contracted by (t/2) X ~
However, since a reinforcing fiber 3 can not be ~ 219S418 contracted and is buckled to have wrlnkle. This leads to dlsarrangement of the orlentatlon of the flber 3.
(2) This dlsaL~ t of the orlentatlon of the fiber 3 is advanced to a stralght portlon of the FPR
relnforcement. As a result, lf the advanced dlstance X
within the stralght portion is ~n~~ ed by uslng the bendlng radius R and the bendlng angle ~, lt could be found that X = 3.5 X R X G by varlous experiments.
I_ the length of the fiber 3 in the inner slde from the center line 2 shown ln Fig. lB, is defined as LBB' as shown in Fig. 2A, the length LBB' i5 changed to LAA' due to the formation of wrinkle by the bendlng work, as shown ln Fig. 2B. Therefore, the orlentatlon angle Q of the fiber 3 of this portion wlll be glven by the followlng expresslons (refer to Fig. 2C) cos~ = LAA'/LBB' (3) The fiber orientation angle ~ due to wrlnkle is glven by the followlng expressions.
cos~ = (R X ~ + 2 X X)JC(R + t/2) X ~ + 2 X X}
= (R X ~ + 2 X 3.5 X R X ~)/C(R + t/2) X G + 2 X 3.5 X R X ~}
~ 8 X R/(8 X R + t/2)--- (l) (4) Fig. 3 is a diagram illustratlng the relationship between the fiber orlentatlon angle derlved from the disarrangement of the fiber and the tenslle strength ~ 2195418 g (load)in a rod-shaped FRP reinf~l ~ for a concrete having a diameter of 10 mm. As shown in Fig. 3, it can be found that when the fiber orientation angle ~ is larger than substantially 12 degrees the tensile strength is remarkably lowered.
However, when the curvature of the above-mentioned conventional reinforcement for the concrete is large, it is difficult to increase the strength of the reinfol~ ~ around the bending worked portion. Namely, (1) To increase the strength thereof it i8 necessary to increase the sectional area thereof. Then, the difference between the inside length of the bending worked portion and the outside length thereof becomes large. Thus, a relnforcing fiber bundle of a portion around the lnside bending worked portion is sub~ected to a strong compression force so that the inside bending ~ 219~4~8 worked portion has a wrinkle, in the result, the reinforcing fiber orientation is disarranged and the strength of the bending worked portion is remarkably lowerea .
(2) Further, the disarrangement is advanced to the straight portion of the reinful, ~ for the concrete, with the result that even the tensile strength of the straight portion thereof is lowered.
(3) Full- ~, when it is sub~ected to a bending work, a bending worked portion is crushed and it is lmposslble to maintain such clrcular sectlonal shape thereln that the straight portion of the reinLulc~ t has. Thus, the sectional shape is warped and the ~ ~r of the entire reinfulu ~ becomes ununiform. This leads to a stress concentration which results in a cause of lowering the strength of the reinfu~
As ~Yrl ~ 1 n~d above, the conventlonal FRP
reinforcement for the concrete has been produced as a substitute for a conventional steel rod. Therefore, the sectlonal shape of the former is circular. As a result, when partlcularly, the bendlng radius ls made small, the strength of the reinfulu ~ ls l~ Ihly lowered.
Therefore, taklng the above-mentioned problems into consideration, it is an ob~ect of the present invention to provide a FRP reinfvl~ ~ for a concrete in which ~ 21g~41g even when the sectional area of the reinL~l~, L i8 large and the bending radius thereof~is small, namely, the curvature thereof is large, a sufficient ~ LL~ Lh of the bending worked portion thereof can be obtained, and also a strength of the straight portion which continues to the bending worked portion can be sllff;r.;Pntly obtained.
DISCLOSURE OF THE INV~NTION
In order to a~, ,li~h the above-mentloned ob~ect of the present invention, according to an aspect of the present invention, there is provided a FRP reinLull - t for a concrete having one or more bending worked portions characteri~ed in that a shape of the section of the reinforcement is substantially rectangular so that the relationship between the th; r.knP~ t and the width w satisfies t/w < 1.
According to the above-mentioned constitution, a section of a FRP reinf~L, t for a ~ull~L-te is substantially rectangular. Therefore, the th~rkn~e~ of the reinL~L~, L can be decreased without changing the sectional area thereof. Thus, a difference between the outside surface length and the inside surface length of the bending worked portion of the reinruL, t is decreased, so that a reinforcing fiber bundle passing through around the inslde of the bending worked portion is subjected to only a small compression force. In the result, the disarrangement of the fiber is not generated, 80 that the ~L~ny~h decrease of the bending worked portion is small.
In the above-mentioned constitution, it is preferable that the relationship between the bending radius R of the inside surface of the bending worked portion and the th~r.kn~.cs t satisfies R/t 2 2.8.
Further, in the above constitution, it is also preferable that when bending directions of adjoining bending worked portions are the same, the length L of the straight portion between the adjoining bending worked portions satisfies L 2 3,5 X R X ~ + 3,5 X R~ X ~
in which the bending radiuses and bending angles Of adjoining bending worked portions are respectively R, and R', ~'.
Further, the substantial rectangle may have outwardly curved short sides or an oval shape.
DRIEF DESCRIPTION QF THE ~RAWINGS
The present invention will be un~eL~o~d more fully from the detailed description given hereinbelow and from a~ ~ ying drawings of the preferred embodiments of the ? .
~ 219~418 ., invention, which, however, should not be taken to be limitatlve to the invention, but are for explanation and understanding only.
In the drawings:
Figs. lA and lB show one embodiment of a FRP
reinful~ ~ for a concrete according to the present invention, in which Fig. lA iS a sectional view, and Fig.
lB is a side view;
Figs. 2A to 2C show a change of a state and the orientation angle on a bending action for a reinforcing fiber in the bending worked portion of the above-mentioned embodiment, in which Fig. 2A is a diagram illustrating the state before bending work of the reinf~" t, Fig. 2B is a diagram illustrating a state where a wrinkle is made by bending work, and Fig. 2C is a diagram illustrating calculation of the orientation angle;
Fig. 3 is a diagram illustrating the tensile strength to the orientation angle in the above-mentioned embodiment of the present invention;
Fig. 4 is a side view illustrating a FRP
reinfoL, t for a ~ in which bending directions of adjoining portions are different from each other, as another ~mhn~ t of the present invention;
Fig.s 5A and 5B show a first e~perimental example of ~ 219S418 the present invention, in which Fig. 5A is a side view, and Fig. 5B is a sectional view taken along line C-C of Fig. 5A;
Fig. 6 is a side view of a second experimental example of the present invention; and Fig. 7 i8 a sectional view of a third ~pPr~r-ntal example of the present invention.
BEST ~QDF FDR I~PL~ENTTNG TH~ IN~NTION
A FRP reinforcement for a concrete according to a preferred embodiment of the present invention will be described below with reference to the ~ ~ yLng drawings.
As shown in Fig. lA, a FPR reinfuL, ~ for a concrete 1 has a substantially rectangular section with a ~hl rkn~q~ of t and a width of w. The opposite short sides of the rectangular section are curved outside.
When the FPR reinforcement for the ~UII~L~tU 1 is sub~ected to a bending work so as to have the inside surface bending radius R and the inside surface bending angle ~, as shown in Fig. lB, (1) the compression force acts on the inner side portion from the center line 2 across the bending worked portion A and the inner side portion is contracted by (t/2) X ~
However, since a reinforcing fiber 3 can not be ~ 219S418 contracted and is buckled to have wrlnkle. This leads to dlsarrangement of the orlentatlon of the flber 3.
(2) This dlsaL~ t of the orlentatlon of the fiber 3 is advanced to a stralght portlon of the FPR
relnforcement. As a result, lf the advanced dlstance X
within the stralght portion is ~n~~ ed by uslng the bendlng radius R and the bendlng angle ~, lt could be found that X = 3.5 X R X G by varlous experiments.
I_ the length of the fiber 3 in the inner slde from the center line 2 shown ln Fig. lB, is defined as LBB' as shown in Fig. 2A, the length LBB' i5 changed to LAA' due to the formation of wrinkle by the bendlng work, as shown ln Fig. 2B. Therefore, the orlentatlon angle Q of the fiber 3 of this portion wlll be glven by the followlng expresslons (refer to Fig. 2C) cos~ = LAA'/LBB' (3) The fiber orientation angle ~ due to wrlnkle is glven by the followlng expressions.
cos~ = (R X ~ + 2 X X)JC(R + t/2) X ~ + 2 X X}
= (R X ~ + 2 X 3.5 X R X ~)/C(R + t/2) X G + 2 X 3.5 X R X ~}
~ 8 X R/(8 X R + t/2)--- (l) (4) Fig. 3 is a diagram illustratlng the relationship between the fiber orlentatlon angle derlved from the disarrangement of the fiber and the tenslle strength ~ 2195418 g (load)in a rod-shaped FRP reinf~l ~ for a concrete having a diameter of 10 mm. As shown in Fig. 3, it can be found that when the fiber orientation angle ~ is larger than substantially 12 degrees the tensile strength is remarkably lowered.
(5) According to the above expression (1), if the condition a ~ 12 degrees is satisfied, cos 12 ~ 8 X
R/(8 X R + t/2). Then, R/t 2 2.8. Therefore, if R/t 2 2.8, that is the width w i8 broad and the thickness t is sufficiently thin in the bending radial direction, strength decrease due to the disarrangement of the orientation of the fiber 3 is hardly exhibited.
In this connection, even if the reinforcement 1 has any shape of section, when the bending radius i8 large, the condition R/t 2 2.8 is 3atisfied. Then, in the present invention, to cause a bending worked portion to have a sufficient strength even in a bendlng radius R
where when a conventional reinful, ~ has a circular section the strength thereo~ is lowered, the section of the reinf~L~ t is caused to be a substantial rectangle having a condition of t/w < 1.
Further, the FRP reinforcement for the concrete of the present invention is not different from a conventional FRP reinf~L- ~ for a concrete having a circular section in that the former is effective under .; I
21~18 the following condition.
0.1 X R2 < S '--(2) in which the sectional area is S. This reasons are described below.
Namely, in other words, if only the relation R/t 2 2.8 is satlsfied, it is suggested that the strength of the bending worked portions is not lowered by the disarrangement of the ~iber orientation even if the section of the reinfu~ has any shape. Namely, if the conventional reinforcement having a circular section maintains a relation:
S -- 7T(t/2)2 ~ ~I (R/2/2.8)Z = 0.1 X R2---(3) The decrease of the strength of the bending worked portion of the reinful~ t could not be exhibited.
However, the FRP reinful~e~ ~ for the concrete of the present invention has such a section that the relation R/t 2 2.8 is satisfied in a condition t/w < 1, that is it has substantially rectangular section. Thus, a sufficient ~Ll~n~ can be obtained in the bending worked portion of the reinforcement of the present invention.
An oval shaped section may of course be used as the shape of the section of the reinful~ ~ other than the rectan~ular shaped section having outwardly curved opposite short sides.
~ 2195~18 (6) Further, since the ad~acent bending worked portions A and B are spaced by 3.5R~ + 3.5R'~' or more as shown in Fig. lB, the disarrangement of the fiber orientation in one of the bending worked portions does not affect on the ~iber orlentatlon in the other of the bending worked portions. The reasons wlll be described below.
The above~ r~1 h~ expresslons (1) and (2) are satisfied when the bending worked portions are respectively independent from each other. When the reinfol~ t has two or more bending worked portions, such conditions are required that one bending worked portion does not affect other bending worked portions.
Then, a case where a flrst bending worked portion A
having a bending radlus of R and a bendlng angle of 9 ls ad~acent to a second bending worked portion B having a bending radius of R' and a bendlng angle of ~', as shown ln Fig. lB, is considered.
The length of a straight portion which a first bending worked portion A affects is 3.5G. A straight portion which is affected by a second bending worked portion should not exist within this range. Therefore, the length L between the bending worked portions A and B
should be satisfied as follows.
L > 3.5R~ + 3.5R'~'---(4) Eowever, when the bending dlrections of the ad~oining ~ 21~5418 bending worked portions A and B are different from each other, as shown in Fig. 4, a fiber which receives a compression force at the first bending worked portion A
receives a tensile force at the second bending worked portion B so that both forces are offset to each other.
Thus, the straight portion does not require above-discussed distance.
R/(8 X R + t/2). Then, R/t 2 2.8. Therefore, if R/t 2 2.8, that is the width w i8 broad and the thickness t is sufficiently thin in the bending radial direction, strength decrease due to the disarrangement of the orientation of the fiber 3 is hardly exhibited.
In this connection, even if the reinforcement 1 has any shape of section, when the bending radius i8 large, the condition R/t 2 2.8 is 3atisfied. Then, in the present invention, to cause a bending worked portion to have a sufficient strength even in a bendlng radius R
where when a conventional reinful, ~ has a circular section the strength thereo~ is lowered, the section of the reinf~L~ t is caused to be a substantial rectangle having a condition of t/w < 1.
Further, the FRP reinforcement for the concrete of the present invention is not different from a conventional FRP reinf~L- ~ for a concrete having a circular section in that the former is effective under .; I
21~18 the following condition.
0.1 X R2 < S '--(2) in which the sectional area is S. This reasons are described below.
Namely, in other words, if only the relation R/t 2 2.8 is satlsfied, it is suggested that the strength of the bending worked portions is not lowered by the disarrangement of the ~iber orientation even if the section of the reinfu~ has any shape. Namely, if the conventional reinforcement having a circular section maintains a relation:
S -- 7T(t/2)2 ~ ~I (R/2/2.8)Z = 0.1 X R2---(3) The decrease of the strength of the bending worked portion of the reinful~ t could not be exhibited.
However, the FRP reinful~e~ ~ for the concrete of the present invention has such a section that the relation R/t 2 2.8 is satisfied in a condition t/w < 1, that is it has substantially rectangular section. Thus, a sufficient ~Ll~n~ can be obtained in the bending worked portion of the reinforcement of the present invention.
An oval shaped section may of course be used as the shape of the section of the reinful~ ~ other than the rectan~ular shaped section having outwardly curved opposite short sides.
~ 2195~18 (6) Further, since the ad~acent bending worked portions A and B are spaced by 3.5R~ + 3.5R'~' or more as shown in Fig. lB, the disarrangement of the fiber orientation in one of the bending worked portions does not affect on the ~iber orlentatlon in the other of the bending worked portions. The reasons wlll be described below.
The above~ r~1 h~ expresslons (1) and (2) are satisfied when the bending worked portions are respectively independent from each other. When the reinfol~ t has two or more bending worked portions, such conditions are required that one bending worked portion does not affect other bending worked portions.
Then, a case where a flrst bending worked portion A
having a bending radlus of R and a bendlng angle of 9 ls ad~acent to a second bending worked portion B having a bending radius of R' and a bendlng angle of ~', as shown ln Fig. lB, is considered.
The length of a straight portion which a first bending worked portion A affects is 3.5G. A straight portion which is affected by a second bending worked portion should not exist within this range. Therefore, the length L between the bending worked portions A and B
should be satisfied as follows.
L > 3.5R~ + 3.5R'~'---(4) Eowever, when the bending dlrections of the ad~oining ~ 21~5418 bending worked portions A and B are different from each other, as shown in Fig. 4, a fiber which receives a compression force at the first bending worked portion A
receives a tensile force at the second bending worked portion B so that both forces are offset to each other.
Thus, the straight portion does not require above-discussed distance.
(7) ~UL ~' ~, since the FRP reinfuL~ t for the concrete according to the present invention has the substantially rectangular section, the bending worked portion is not crushed, and a stress concentration due to ununiform diameter does not occur, whereby the decrease of the strength of the reinforcement is not exhibited.
As ~xp-~1n~ above~ in the FRP reinforcement for a concrete according to the present invention, a sufficient strength can be obtained in both the bending worked portions and the straight portion.
Next, experimental examples of the present invention will now be described.
(First Experimental ~xampiej Fig.s 5A and 5B show a first experimental example of the present invention, in which a reinforcement 4 composed of an epoxi resin-impregnated carbon fiber ls orlented in one direction (longitudinal direction). The reinforcement 4 has a shape of the section having a 219~ 8 substantlally rectangular shape in which the width is w and the ~hlrknPqq (height) i8 t, while being provided with a number of proJected portions 5 with the same intervals.
By molding and curing the reinful~ ~ 4 so as to have the thickness t = 3mm, width w = 12.8mm, the radius R = 15mm, and the distance L of the straight portion between the bending worked portions = 200 mm, a hoop shaped FRP relnful~ t for a concrete is produced.
Since the distance L of the straight portion between the bending worked portions of the reinfulu, --t 4 satisfies L = 200 > 3,5 X R X ~ + 8.5 X R' X ~' = 165, and the relationship between the bending radius R and the ~h~rknP~ t satisfies R/t = 5 > 2.8, then following condition satisfies.
a g o~ < 12~
Consequently, a sufficiently small fiber orientation angle a, a sufficient ~lellyLII of the bending worked portion and a sufficient tensile ~L~I~h of the straight portion of the reinfulu~ ~ 4 could be obtained.
Further, since in the present invention, the bending worked portion is not crushed, (l) the stress concentration due to ununiformness of the thickness t 1- 2~418 does not occur, (2) an area contacting to a maln (stralght) relnf~ at the bendlng worked portlon 18 broad and a thlckness thereof ls unlform. In the result, the stress whlch ls applied to the bendlng worked portion from the maln relnf~L~ t is small. These are causes that make the strength of the bending worked portion large.
Further, thls relnforcement of the present lnventlon has an lmproved ~hPql~n force to the ~n~l~Le. The adheslon force to the concrete is preferably provided by unevenness ln pro~ected portions of the surface of the concrete. Accordingly, slnce the surface area to the sectlon area is larger in this example than in a ' conventional circular gection case, a large ~h~clrn strength against the same tenslle ~LL~n~LII can be obtained.
~Second Experimental Example) When the thlrknrqq of the reinfol, t for the concrete must be increased, the problem can be resolved by piling a plurality of them.
Fig. 6 shows this experimental example ln which another reinforcement 4a which is one size larger than the reinforcement 4 discussed in the first experimental example is piled on the relnforcement 4 ln the thl r.kn~cq dlrection thereof so that the respectlve projected and ~ 2195~18 recessed portions are fixed to each other.
Thus, by piling both reinforcements 4 and 4a the strenyth of this reinful~- t is increased. However, since the bending work is carried out every reinforcement, the di~LL~ny ~ of the fiber orientation at the bending worked portions and the unevenness of the shape of the section do not occur. As a result, the strength of the reinfuL, ~ can be increased without increasing the width thereof. Further the number of the reinfuL, ~ to be piled are not limited to two, and any number of reinfuL~ ~ may be piled.
(Third Experimental Example ) In the above-mentioned first and second experimental 15 r ~ lPe~ reinfuLu~ ~ts composed of only FRP are described. However, taking the l ~h1 l 1 ty, bending wnrk~hlllty, high impact properties or the like into consideration, a FRP core material 6 on the surface of which a coating layer 7 composed of a thermoplastic resin is applied may be used, as shown in Fig. 7. The pro~ected portion 5 shown in Fig. 7 is composed of the thermoplastic resin. Further, an example having no pro~ected portion 5 may be used.
It should be considered that the above-mentioned thickness t and width w correspond to the ~h~kn~e t1 and ~ ~ 213~4~8 width w1 of the core material 6, and that the respective relations are calculated by taking the bending radius R
as (R + d) or (R + d') including the th~rkn~ss d of the ccating layer 7 or the thi~knp~ d' of the proJected portion 5 into consideration.
It is not necessary that the coating layer 7 is composed of a thermoplastic resin ghown in Fig. 7. For example, a coating layer 7 which ig formed by spirally windlng a tape on the FRP core material 6 or another coatlng layer 7 which is formed by sandwiching the FRP
core material 6 by twc sheets of films may be used.
As materials which construct the reinful t for the concrete, particularly as the reinforced fiber for FRP, inorganic fiber such as a carbon fiber, glass fiber or an organic fiber such as aramid fiber is used. Further, as a matrix resin a thermosetting resin such as an epoxi resin, un~uL~d polyester, phenolic resin is used.
As ~xp1R~n~fl above, even if the sectional area is broad and the ~UlV~UL~ is large, the FRP reinf~L, t for the concrete of the present invention can have a sufficient bending strength. Also, the strength of the straight portion ccntinuing to this bending portion can have a sufficient strength.
Although the present invention has been illustrated and described with respect to ~PmplRry embodiment - ~ 219~41~
thereo~, it should be understood by those skilled in the art that the fore~oing and various other changes, omissions and additions may be made therein and thereto, without departing from the gist and scope of the present invention. Therefore, the present invention should not be understood as limited to the specific embodiments set out above but to include all possible embodiments which can be embodied within a scope encompassed and equivalents thereof with re~pect to the features set out in the appended claims.
As ~xp-~1n~ above~ in the FRP reinforcement for a concrete according to the present invention, a sufficient strength can be obtained in both the bending worked portions and the straight portion.
Next, experimental examples of the present invention will now be described.
(First Experimental ~xampiej Fig.s 5A and 5B show a first experimental example of the present invention, in which a reinforcement 4 composed of an epoxi resin-impregnated carbon fiber ls orlented in one direction (longitudinal direction). The reinforcement 4 has a shape of the section having a 219~ 8 substantlally rectangular shape in which the width is w and the ~hlrknPqq (height) i8 t, while being provided with a number of proJected portions 5 with the same intervals.
By molding and curing the reinful~ ~ 4 so as to have the thickness t = 3mm, width w = 12.8mm, the radius R = 15mm, and the distance L of the straight portion between the bending worked portions = 200 mm, a hoop shaped FRP relnful~ t for a concrete is produced.
Since the distance L of the straight portion between the bending worked portions of the reinfulu, --t 4 satisfies L = 200 > 3,5 X R X ~ + 8.5 X R' X ~' = 165, and the relationship between the bending radius R and the ~h~rknP~ t satisfies R/t = 5 > 2.8, then following condition satisfies.
a g o~ < 12~
Consequently, a sufficiently small fiber orientation angle a, a sufficient ~lellyLII of the bending worked portion and a sufficient tensile ~L~I~h of the straight portion of the reinfulu~ ~ 4 could be obtained.
Further, since in the present invention, the bending worked portion is not crushed, (l) the stress concentration due to ununiformness of the thickness t 1- 2~418 does not occur, (2) an area contacting to a maln (stralght) relnf~ at the bendlng worked portlon 18 broad and a thlckness thereof ls unlform. In the result, the stress whlch ls applied to the bendlng worked portion from the maln relnf~L~ t is small. These are causes that make the strength of the bending worked portion large.
Further, thls relnforcement of the present lnventlon has an lmproved ~hPql~n force to the ~n~l~Le. The adheslon force to the concrete is preferably provided by unevenness ln pro~ected portions of the surface of the concrete. Accordingly, slnce the surface area to the sectlon area is larger in this example than in a ' conventional circular gection case, a large ~h~clrn strength against the same tenslle ~LL~n~LII can be obtained.
~Second Experimental Example) When the thlrknrqq of the reinfol, t for the concrete must be increased, the problem can be resolved by piling a plurality of them.
Fig. 6 shows this experimental example ln which another reinforcement 4a which is one size larger than the reinforcement 4 discussed in the first experimental example is piled on the relnforcement 4 ln the thl r.kn~cq dlrection thereof so that the respectlve projected and ~ 2195~18 recessed portions are fixed to each other.
Thus, by piling both reinforcements 4 and 4a the strenyth of this reinful~- t is increased. However, since the bending work is carried out every reinforcement, the di~LL~ny ~ of the fiber orientation at the bending worked portions and the unevenness of the shape of the section do not occur. As a result, the strength of the reinfuL, ~ can be increased without increasing the width thereof. Further the number of the reinfuL, ~ to be piled are not limited to two, and any number of reinfuL~ ~ may be piled.
(Third Experimental Example ) In the above-mentioned first and second experimental 15 r ~ lPe~ reinfuLu~ ~ts composed of only FRP are described. However, taking the l ~h1 l 1 ty, bending wnrk~hlllty, high impact properties or the like into consideration, a FRP core material 6 on the surface of which a coating layer 7 composed of a thermoplastic resin is applied may be used, as shown in Fig. 7. The pro~ected portion 5 shown in Fig. 7 is composed of the thermoplastic resin. Further, an example having no pro~ected portion 5 may be used.
It should be considered that the above-mentioned thickness t and width w correspond to the ~h~kn~e t1 and ~ ~ 213~4~8 width w1 of the core material 6, and that the respective relations are calculated by taking the bending radius R
as (R + d) or (R + d') including the th~rkn~ss d of the ccating layer 7 or the thi~knp~ d' of the proJected portion 5 into consideration.
It is not necessary that the coating layer 7 is composed of a thermoplastic resin ghown in Fig. 7. For example, a coating layer 7 which ig formed by spirally windlng a tape on the FRP core material 6 or another coatlng layer 7 which is formed by sandwiching the FRP
core material 6 by twc sheets of films may be used.
As materials which construct the reinful t for the concrete, particularly as the reinforced fiber for FRP, inorganic fiber such as a carbon fiber, glass fiber or an organic fiber such as aramid fiber is used. Further, as a matrix resin a thermosetting resin such as an epoxi resin, un~uL~d polyester, phenolic resin is used.
As ~xp1R~n~fl above, even if the sectional area is broad and the ~UlV~UL~ is large, the FRP reinf~L, t for the concrete of the present invention can have a sufficient bending strength. Also, the strength of the straight portion ccntinuing to this bending portion can have a sufficient strength.
Although the present invention has been illustrated and described with respect to ~PmplRry embodiment - ~ 219~41~
thereo~, it should be understood by those skilled in the art that the fore~oing and various other changes, omissions and additions may be made therein and thereto, without departing from the gist and scope of the present invention. Therefore, the present invention should not be understood as limited to the specific embodiments set out above but to include all possible embodiments which can be embodied within a scope encompassed and equivalents thereof with re~pect to the features set out in the appended claims.
Claims (10)
1. A FRP reinforcement for a concrete having one or more bending worked portions, wherein a sectional area of the reinforcement is substantially rectangular so that the relationship between the thickness t and the width w satisfies t/w < 1 and a bending direction and a thickness direction of said bending worked portion are on the same plane.
2. A FRP reinforcement for a concrete according to claim 1, wherein the relationship between the bending radius R
of the inner side of the bending worked portion and the thickness t satisfies R/t ~ 2.8.
of the inner side of the bending worked portion and the thickness t satisfies R/t ~ 2.8.
3. A FRP reinforcement for a concrete according to claim 1 or 2, wherein when bending directions of adjoining bending worked portions are the same, the length L of the straight portion between said adjoining bending worked portions satisfies L ~ 3.5 X R X .theta. + 3.5 X R' X .theta.' in which the bending radius the inner side of the bending worked portion and the bending angle are respectively R, .theta. and R', .theta.'.
4. A FRP reinforcement for a concrete according to any one of claims 1 to 3, wherein said substantial rectangle has outwardly curved short sides.
5. A FRP reinforcement for a concrete according to any one of claims 1 to 3, wherein said substantial rectangle is an oval shape.
6. A FRP reinforcement for a concrete according to claim 1, wherein a number of equally-spaced projected portions 5 are provided at both the side surfaces.
7. A FRP reinforcement for a concrete according to claim 1 or 6, wherein another reinforcement which is one size larger than said reinforcement is piled thereon in the thickness direction of said reinforcement.
8. A FRP reinforcement for a concrete according to claim 1 or 6, wherein using a FRP as a core material, a coating layer composed of thermoplastic resin is provided on the surface of the core material.
9. A FRP reinforcement for a concrete according to claim 1 or 6, wherein using a FRP as a core material, a coating layer is formed by winding a tape spirally on the surface of the core material.
10. A FRP reinforcement for a concrete according to claim 1 or 6, wherein using a FRP as a core material, a coating layer is formed by sandwiching the core material by said two sheets of films.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18106094A JPH0842060A (en) | 1994-08-02 | 1994-08-02 | Concrete reinforcing bar made of frp |
| JPHEI6-181060 | 1994-08-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2195418A1 true CA2195418A1 (en) | 1996-02-15 |
Family
ID=16094088
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2195418 Abandoned CA2195418A1 (en) | 1994-08-02 | 1995-08-01 | Reinforcing bar for frp concrete |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0774552A4 (en) |
| JP (1) | JPH0842060A (en) |
| CA (1) | CA2195418A1 (en) |
| NO (1) | NO970411L (en) |
| WO (1) | WO1996004440A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU720157B2 (en) * | 1997-01-23 | 2000-05-25 | Sika Technology Ag | Flat strip lamellas for reinforcing building components and method for their production |
| WO2000006851A1 (en) * | 1998-07-27 | 2000-02-10 | Surface Technologies, Inc. | Concrete reinforcing system having non-corrosive bendable flanges |
| KR20020093792A (en) * | 2000-01-13 | 2002-12-16 | 다우 글로벌 테크놀로지스 인크. | Reinforcing bars for concrete structures |
| WO2001051731A1 (en) | 2000-01-13 | 2001-07-19 | The Dow Chemical Company | Small cross-section composites of longitudinally oriented fibers and a thermoplastic resin as concrete reinforcement |
| CN101134369A (en) * | 2006-09-01 | 2008-03-05 | 深圳市海川实业股份有限公司 | Technique of preparing FRP fibre-reinforced composite material bar |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53159115U (en) * | 1977-05-20 | 1978-12-13 | ||
| JPS6135231A (en) * | 1984-07-27 | 1986-02-19 | Mitsui Constr Co Ltd | Manufacture of structural irregular-shaped reinforcing material |
| JPS63221035A (en) * | 1987-03-10 | 1988-09-14 | Showa Highpolymer Co Ltd | Manufacture of reinforcing bar made of fiber reinforced synthetic resin with profile section |
| JP2691236B2 (en) * | 1987-10-30 | 1997-12-17 | 清水建設株式会社 | Concrete reinforcement |
| JP2602706B2 (en) * | 1988-10-24 | 1997-04-23 | 三井建設株式会社 | Method for manufacturing hoop streaks |
| JPH06136882A (en) | 1992-10-21 | 1994-05-17 | Komatsu Kasei Kk | Manufacture of concrete reinforcing material made of frp |
-
1994
- 1994-08-02 JP JP18106094A patent/JPH0842060A/en active Pending
-
1995
- 1995-08-01 EP EP95926535A patent/EP0774552A4/en not_active Withdrawn
- 1995-08-01 CA CA 2195418 patent/CA2195418A1/en not_active Abandoned
- 1995-08-01 WO PCT/JP1995/001528 patent/WO1996004440A1/en not_active Application Discontinuation
-
1997
- 1997-01-30 NO NO970411A patent/NO970411L/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| EP0774552A4 (en) | 1997-10-22 |
| JPH0842060A (en) | 1996-02-13 |
| NO970411D0 (en) | 1997-01-30 |
| EP0774552A1 (en) | 1997-05-21 |
| WO1996004440A1 (en) | 1996-02-15 |
| NO970411L (en) | 1997-02-19 |
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