JP7118880B2 - Shear reinforcement method for PC box girder bridge - Google Patents

Description

The present invention relates to a method for shear reinforcement of a PC box girder bridge, and more particularly, a PC box girder bridge in which the prestress of the PC steel bars of the PC box girder bridge is relaxed or released, and other shear reinforcement is performed instead. related to the shear reinforcement construction method.

In the past, due to the ability to resist large compressive forces due to bending moments and the characteristics of the cross section that facilitates the placement of reinforcing materials, etc., the cross section of the main girder is box-shaped, and PC steel bars are placed vertically or diagonally on the sides of the box for post tensioning. Prestressed PC box girder bridges are known.

For example, Patent Document 1 discloses a PC box girder bridge in which prestressing is applied by vertically arranging prestressing tendons 43, which are PC steel rods, on a box girder web 41 to resist shear forces. (see paragraph [0032] of the specification of Patent Document 1, FIG. 10 of the drawings, etc.).

However, PC box girder bridges to which prestress is applied with this type of PC steel bar, including the PC box girder bridge described in Patent Document 1, decrease in prestress or break due to deterioration over time, resulting in PC steel. There was also the risk of an accident in which a part of the rod jumped out of the floor slab.

In particular, bridges such as PC box girder bridges are often built as elevated bridges over wide roads, with railways and other roads running below them. There was a danger that the part would fall downward and hit people, cars, and trains on the road, leading to a serious accident.

In the past, there were only coping methods for such problems, such as pasting a fiber material on the road surface side so that the PC steel bar would not pop out even if it were to break. For example, Patent Document 2 discloses a prestressed concrete bridge structure 10 in which an outer cable 13 is stretched with a low tension such that a fixture 16 of a prestressed concrete bridge 11 and a bearing plate are in close contact with each other, and the outer cable is tensioned. A prestressed concrete bridge structure is disclosed in which a tensioning mechanism 14 for holding and a detecting means 15 for detecting variations in the tension of the outer cable are provided, and the detecting means quantitatively monitors the tension of the outer cable (Patent Document 2 Claim 1 of the scope of claims, paragraphs [0011] to [0021] of the specification, FIGS. 1 to 5 of the drawings, etc.).

However, in the prestressed concrete bridge structure described in Patent Document 2, although it is possible to know that the PC steel material of the existing bridge has broken, it is necessary to constantly monitor it, which increases the running cost and, as described above, It did not go beyond the realm of symptomatic therapy and was not a fundamental solution.

In view of these, the inventors of the present invention have devised the method of pre-relaxing or canceling the pre-stress of the PC steel material, which may break due to deterioration over time and jump out of the floor slab, and instead perform other shear reinforcement. . As a method for shear reinforcement of the side part of the PC box girder bridge, (1) steel plate adhesion method, (2) PC reinforcement method, (3) fiber reinforcement method, etc. can be considered.

However, (1) the steel plate bonding method has the problem that the steel plate is heavy and requires a lifting machine such as a crane, resulting in poor workability. In addition, due to the reinforcement work, the self-weight of the PC box girder bridge increased compared to when the structure was designed, which had an adverse effect on the bridge piers and bearings.

In addition, (2) the PC reinforcement construction method has the problem that it is necessary to provide a fixing portion and a deflecting portion in order to stabilize the shape of the outer cable, resulting in poor workability and a long construction period.

Furthermore, in the (3) fiber reinforcement construction method, when general carbon fibers are used as fiber reinforcement, there is a problem that it is not possible to visually confirm the aging deterioration of the reinforcement fibers after reinforcement. In addition, there is also a problem that the strength of the reinforcing fibers as a whole is determined by the fixing method of the ends, and the fiber strength of the reinforcing fibers is not fully utilized. In addition, the CF anchor, which is known as a carbon fiber fixing method, has the problem that the construction procedure is troublesome, the construction period increases, and the construction cost increases.

For example, although it is not a PC box girder bridge, as a method of shear reinforcing a bridge with reinforcing fibers, Patent Document 3 describes a thickening method of increasing the thickness of cement or polymer mortar after fixing FRP lattice bars to concrete rod members. In the above, the concrete surface to which the FRP lattice is fixed is the web surface of the concrete bar member, and before fixing the FRP lattice, the web surface is subjected to surface treatment using water jet, shot blast, or sand blast. and the FRP grid bars are fixed to the web surface using rivet anchors (claim 1 of the scope of patent document 3, paragraph [ 0031] to [0045], see FIGS. 1 to 5 of the drawings, etc.).

However, the concrete reinforcement method described in Patent Literature 3 also requires time and effort for surface treatment, etc., and cannot solve the above-described problems of the fiber reinforcement method.

JP 2006-112189 A JP 2012-127053 A JP-A-2002-129753

SUMMARY OF THE INVENTION Accordingly, the present invention has been devised in view of the above-mentioned problems. To provide a shear reinforcement construction method for a PC box girder bridge which can be carried out in a short time and at a low cost.

A shear reinforcement method for a PC box girder bridge according to claim 1 is a shear reinforcement method for a PC box girder bridge in which prestress is applied by placing PC steel bars in the web portion of the box girder, wherein the PC steel bars A shear reinforcement step of performing new shear reinforcement on one or both sides of the web portion that can bear the shear stress of the web portion borne by the prestress release step of relaxing or releasing the prestress applied to the PC steel bar and.

A shear reinforcement method for a PC box girder bridge according to claim 2 is the shear reinforcement method for a PC box girder bridge according to claim 1, wherein in the prestress releasing step, the PC steel bars are cut and removed. and

The shear reinforcement method for a PC box girder bridge according to claim 3 is the shear reinforcement method for a PC box girder bridge according to claim 1 or 2, wherein in the shear reinforcement step, reinforcing fibers are used, and the ends of the reinforcing fibers are The fixation to the web portion is performed by adhering a steel plate to the reinforcing fibers and fixing the steel plate to the concrete frame.

The shear reinforcement method for a PC box girder bridge according to claim 4 is the shear reinforcement method for a PC box girder bridge according to claim 3, wherein in the shear reinforcement step, reinforcing fibers are arranged in stripes on the web portion at predetermined intervals. It is characterized in that it is arranged in

The shear reinforcement method for a PC box girder bridge according to claim 5 is the shear reinforcement method for a PC box girder bridge according to claim 3 or 4, wherein in the shear reinforcement step, the steel plates are separated so as not to constrain the axial force. It is characterized in that it is installed by

The shear reinforcement method for a PC box girder bridge according to claim 6 is the shear reinforcement method for a PC box girder bridge according to claim 5, wherein in the shear reinforcement step, post-installed anchors are used to fix the steel plates to the concrete frame. , wherein the weight of the steel plate is borne by post-installed anchors.

The shear reinforcement method for a PC box girder bridge according to claim 7 is the shear reinforcement method for a PC box girder bridge according to claim 5, wherein in the shear reinforcement step, a steel plate with an eccentric head is used as the steel plate, and the steel plate with the eccentric head is used as the steel plate. By embedding the eccentric head of a steel plate in the concrete frame and fixing it with a material that hardens over time, the fixing of the ends of the reinforcing fibers to the web portion is stopped by pressing from above with the steel plate with the eccentric head. It is characterized by performing by

According to the inventions of Claims 1 to 7, since the prestress releasing step is provided, it is possible to reliably prevent a pop-out accident due to breakage of the PC steel bar.

In particular, according to the second aspect of the invention, since the PC steel bar is cut and removed, it is possible to completely eliminate the risk of a pop-out accident due to breakage of the PC steel bar.

In particular, according to the third aspect of the invention, a steel plate is adhered to the reinforcing fiber, and the steel plate is fixed to the concrete frame. can be done. Therefore, the strength of the reinforcing fibers can be maximized to solve the problem that the overall reinforcing strength is determined by the fixing method of the ends and the fiber strength of the reinforcing fibers is not fully utilized. In addition, according to the third aspect of the invention, shear reinforcement work can be performed safely and in a short time. Therefore, construction costs can be reduced.

In particular, according to the fourth aspect of the invention, since the reinforcing fibers are arranged in stripes at predetermined intervals in the web portion, even if the reinforcing fibers are opaque carbon fibers, cracks or the like in the web portion can be prevented. It is possible to visually confirm the presence or absence of occurrence.

In particular, according to the fifth aspect of the invention, since the steel plates are spaced apart from each other, the axial force is not constrained, unnecessary stress does not act on the steel plates and the reinforcing fibers, and the horizontal direction acting on the web portion does not occur. Only shear forces can be borne. Therefore, shear reinforcement can be effectively performed.

In particular, according to the sixth and seventh aspects of the present invention, the shear reinforcement work can be performed more safely and in a shorter time, and the ends of the reinforcing fibers can be reliably fixed to the web. .

BRIEF DESCRIPTION OF THE DRAWINGS It is a vertical sectional view which shows the structure of the PC box girder bridge which applies the shear reinforcement construction method of the PC box girder bridge which concerns on embodiment of this invention. Fig. 3 is a vertical cross-sectional view showing a box-girder bridge obtained by shear-reinforcing the same PC box-girder bridge by applying the shear-reinforcing construction method for a PC box-girder bridge according to the embodiment of the present invention. Fig. 4 is a partially enlarged side view of the shear reinforcement of the web portion of the same box girder bridge as seen in the horizontal direction; Fig. 4 is a partially enlarged vertical cross-sectional view showing the vicinity of the upper end of the shear reinforcement of the web portion of the same box girder bridge. (a) is a partially enlarged vertical cross-sectional view showing a modified example of shear reinforcement of the web portion of the box girder bridge, and (b) is an elevational view of only the steel plate with an eccentric head seen in the horizontal direction. . FIG. 5 is a vertical sectional view showing a box girder bridge in which shear reinforcement is performed on the inner side of the girder web as a shear reinforcement construction method for a PC box girder bridge according to another embodiment of the present invention.

Hereinafter, one embodiment of a floor slab waterproof layer construction system and a floor slab waterproof layer construction method according to the present invention will be described in detail with reference to the drawings.

A shear reinforcement construction method for a PC box girder bridge according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG. First, a brief description will be given of a PC box girder bridge to which the shear reinforcement construction method for a PC box girder bridge according to this embodiment is applied. FIG. 1 is a vertical sectional view showing the configuration of a PC box girder bridge to which a shear reinforcement construction method for a PC box girder bridge according to an embodiment of the present invention is applied.

The precondition for applying the present invention is that, in the PC box girder bridge 1 shown in FIG. The prestress applied to the bar is at least lower than the value assumed at the time of design. Therefore, in the present embodiment, the prestress of the PC box girder bridge 1, in which the PC steel rods are arranged along the vertical direction on the web portion of the box girder, is assumed to be lower than at the time of installation.

As shown in FIG. 1, the PC box girder bridge 1 is composed of an upper deck section 10, a lower deck section 11, and a pair of left and right web sections 12 connecting them. In this PC box girder bridge 1, a space surrounded by the upper deck section 10, the lower deck section 11 and the web section 12 is a hollow section 13. As shown in FIG.

A PC steel rod 14 (PC steel material) is inserted through the pair of web portions 12 as shear reinforcement against horizontal force, and prestress is applied to the PC steel rod 14 . However, this prestress is lower than the value assumed at the time of design due to aged deterioration and the like.

(Shear reinforcement process)
In the shear reinforcement construction method for a PC box girder bridge according to the embodiment of the present invention, a shear reinforcement process is performed to carry out new shear reinforcement capable of bearing the shear stress of the web portion 12 that is borne by the PC steel rods 14 . Here, the ability to bear the shear stress of the web portion 12 that the PC steel rod 14 bears means that even if the PC steel rod 14 was not inserted through the web portion 12 and there was no prestress at the time of structural design, It refers to performing shear reinforcement that can withstand the shear stress (horizontal force) acting on the PC box girder bridge 1 .

FIG. 2 is a vertical cross-sectional view showing a state in which the PC box girder bridge 1 of FIG. 3 is a partially enlarged side view of the web portion 12 of the box-girder bridge 1 subjected to shear reinforcement, viewed in the horizontal direction, and FIG. 2 is a partially enlarged vertical cross-sectional view showing the .

Specifically, as shown in FIGS. 2 to 4, in the shear reinforcement construction method for a PC box girder bridge according to the present embodiment, reinforcing fibers are first adhered to the outer surfaces of both sides of the web portion 12 using an adhesive. . Of course, depending on the state of deterioration of the PC steel bar 14, only one side of the outer surface of the web portion 12 may be shear reinforced.

In addition, in this embodiment, the carbon fiber 2 (carbon fiber) is used as the reinforcing fiber. However, the reinforcing fiber according to the present invention is not limited to carbon fiber, and may be glass fiber, vinylon fiber, polyolefin fiber, polyester fiber, polyamide fiber, aramid fiber, basalt fiber, or the like.

In addition, in this step, an epoxy resin that is highly alkaline is used as the adhesive for bonding the carbon fibers 2 to the concrete. Needless to say, the adhesive according to the present invention is not limited to the epoxy resin, and may be appropriately selected from acrylic resin, cement-based resin, or the like, depending on the reinforcing fiber to be used.

In this step, as shown in FIG. 3, the carbon fibers 2 are arranged in stripes on the web portion 12 at predetermined intervals. The reason for the striped arrangement is to enable visual confirmation of the presence or absence of cracks or the like in the portion where the PC steel rod 14 is embedded and the outer surface of the other web portion 12 . Therefore, when the PC steel bar 14 is installed obliquely, the stripes of the carbon fibers 2 are also oblique.

Further, fixing of the carbon fibers 2 to the concrete frame has conventionally been performed by CF anchors or the like. Conventional CF anchors are expensive and, as mentioned above, require a lot of time and effort in construction, such as counting the number of anchors. In addition, as described above, the strength of the overall shear reinforcement is determined by the adhesive strength of the CF anchor, and there is also the problem that the fiber strength of the carbon fibers 2 is not fully utilized.

Therefore, in the shear reinforcement construction method for a PC box girder bridge according to the present embodiment, as shown in FIGS. going through. Specifically, the steel plate 3 is adhered to the vicinity of the end of the carbon fiber 2 with an adhesive, and the steel plate 3 is fixed to the web portion 12 or the concrete skeleton such as the upper floor slab portion 10 or the lower floor slab portion 11. ing. This prevents the stress from concentrating on individual fibers of the carbon fibers 2 and breaking them. Therefore, the fiber strength of the carbon fibers 2 can be maximized. It should be noted that the carbon fiber 2 and the steel plate 3 are preferably bonded using an adhesive such as an epoxy resin or an acrylic resin.

Further, as shown in FIG. 3, these steel plates 3 are provided with joints so as not to constrain the axial force acting on the web portion 12 in the vertical direction, and are installed at predetermined intervals. Therefore, unnecessary stress does not act on the steel plate 3 and the carbon fibers 2 , and the carbon fibers 2 can bear only the horizontal shearing force acting on the web portion 12 . Of course, the distance between the joints may be such that the steel plates 3 do not contact each other even if the steel plates 3 behave separately due to the applied stress.

As shown in FIG. 4, the steel plate 3 is fixed to the concrete skeleton such as the upper floor slab 10 with post-installed anchors 30 via angle irons 31 . The angle steel 31 is fixed to the steel plate 3 by welding, bolting, or the like. Further, the steel plate 3 may be fixed to the concrete frame by fixing to the web portion 12 or the lower floor slab portion 11 .

Here, the fixing of the steel plate 3 to the concrete frame is performed for the purpose of supporting the weight of the heavy steel plate 3, and the post-installed anchor 30 may be a hole-in anchor or the like. Although not shown, the lower end portion of the carbon fiber 2 is similarly fixed to the concrete frame such as the lower floor slab 11 with the post-installed anchor 30 via the angle steel 31 .

FIG. 5(a) is a partially enlarged vertical sectional view showing a modified example of shear reinforcement of the web portion 12 of the box girder bridge 1 to which the shear reinforcement construction method for the PC box girder bridge according to the present embodiment is applied. b) is an elevational view of only the steel plate with the eccentric head seen in the horizontal direction.

As shown in FIG. 5, as a modification of fixing the steel plate 3 to the concrete frame, a steel plate 3′ with an eccentric head provided with an eccentric head 3a outside the end of the steel plate 3 described above, and the end of the carbon fiber 2 is fixed. It is conceivable to press the part from above to fix it.

As shown in FIG. 5(b), this steel plate 3' with an eccentric head has an eccentric head 3a in which a crimping grip eccentric to the outside from the axis of the steel bar 3b is fitted to the tip of a steel bar 3b such as a reinforcing bar. there is The eccentric head-equipped steel plate 3′ is fixed to the concrete frame by inserting the eccentric head 3a into the recess 10a formed in the concrete frame such as the upper floor slab 10 and using a time hardening material (not shown) such as grout or resin. Harden and fix.

In the case of fixing to the concave portion 10a that opens downward as in the illustrated embodiment, hardening mortar, high viscosity resin, or the like is used as the time-hardening material to be filled so that the time-hardening material does not fall before it hardens. . In this way, by fixing using the eccentric head 3a, the vicinity of the ends of the carbon fibers 2, which are easily peeled off, can be firmly fixed to the concrete frame, and the effect of shear reinforcement can be maximized.

By fixing the steel plate 3 to the concrete frame as described above, the shear reinforcement process is completed.

(Prestress release step)
Next, in the shear reinforcement construction method for a PC box girder bridge according to the present embodiment, a prestress releasing step for relaxing or releasing the prestress applied to the PC steel rods 14 is performed.

Specifically, in this step, the prestress is released by cutting the PC steel rod 14 or its fixture portion. At this time, when cutting the PC steel bar 14, it is preferable to take a protective measure such as a protective net so that a part of the cut PC steel bar 14 does not suddenly lose the tension of the prestress and jump out. Of course, the prestress may be relaxed by pulling out the fixing part of the PC steel bar 14 and loosening the fixing part with a jack or the like.

In short, in this step, the prestress is released by cutting the PC steel bar 14 as described above, or the prestress applied to the PC steel bar 14 is relaxed to the extent that there is no risk of an accident in which the broken pieces pop out. .

With the completion of this process, the shear reinforcement construction method for the PC box girder bridge according to the present embodiment is completed.

According to the shear reinforcement construction method for a PC box girder bridge according to the embodiment of the present invention described above, the PC steel bars 14 that have deteriorated over time are cut and removed. Fear can be completely eliminated. Moreover, the same applies when the prestress applied to the PC steel bar 14 is relaxed.

In addition, according to the shear reinforcement construction method of the PC box girder bridge according to the present embodiment, the steel plate 3 is bonded to the carbon fiber 2 which is the reinforcing fiber, and the steel plate 3 is fixed to the concrete frame such as the upper floor slab 10. Perform shear reinforcement. Therefore, the weak point of the carbon fiber 2 (reinforcing fiber), which is weak against stress concentration such as bending, can be compensated for by the steel plate 3 and fixed. Therefore, the strength of the carbon fibers 2 can be maximized to solve the problem that the fiber strength is not fully utilized. In addition, shear reinforcement work can be performed safely and in a short time. Therefore, construction costs can be reduced.

Moreover, according to the shear reinforcement construction method for a PC box girder bridge according to the present embodiment, since the opaque carbon fibers 2 are arranged in stripes on the web portion 12 at predetermined intervals, cracks or the like occur in the web portion 12. It is possible to visually confirm the presence or absence of the

In addition, according to the shear reinforcement construction method of the PC box girder bridge according to the present embodiment, since joints are provided in the steel plate 3 and installed at a distance, the axial force is not constrained, and the steel plate 3 and the carbon fiber 2 are not required stress does not act. Therefore, the carbon fibers 2 can bear only the horizontal shearing force acting on the web portion 12, and shear reinforcement can be effectively performed.

The shear reinforcement construction method for a PC box girder bridge according to the embodiments of the present invention has been described in detail above. nothing more than a thing. Therefore, the technical scope of the present invention should not be construed to be limited by these.

In particular, the case of bonding the reinforcing fibers to the outer surface of the web portion 12 using an adhesive has been described as an example, but as shown in FIG. I don't mind. Also, the reinforcing fibers (carbon fibers 2) may be adhered to both the inner surface and the outer surface of the web portion 12 . The provision of reinforcing fibers (carbon fibers 2) on both sides of the web portion 12 is particularly effective when the desired shear resistance cannot be secured by adhesion alone.

1: PC box girder bridge (box girder bridge)
10: Upper deck portion 10a: Concave portion 11: Lower deck portion 12: Web portion 13: Hollow portion 14: PC steel bar (PC steel material)
2: Carbon fiber (reinforcement fiber)
3: Steel plate 30: Post-installed anchor 31: Angle steel 3': Steel plate with eccentric head (steel plate)
3a: Eccentric head 3b: Steel bar

Claims (7)

A shear reinforcement construction method for a PC box girder bridge in which PC steel bars are arranged in the web portion of the box girder and prestressed,
A shear reinforcement step of performing new shear reinforcement that can bear the shear stress of the web portion borne by the PC steel bar on one side or both sides of the web portion;
and a prestress releasing step of relaxing or releasing the prestress applied to the PC steel bars. The shear reinforcement construction method for a PC box girder bridge according to claim 1, wherein, in the prestress releasing step, the PC steel bars are cut and removed. In the shear reinforcement step, reinforcing fibers are used, and the ends of the reinforcing fibers are fixed to the web portion by bonding a steel plate to the reinforcing fibers and fixing the steel plate to the concrete frame. The shear reinforcement construction method for a PC box girder bridge according to claim 1 or 2. 4. The method for shear reinforcement of a PC box girder bridge according to claim 3, wherein, in said shear reinforcement step, reinforcing fibers are arranged in stripes at predetermined intervals on said web portion. 5. The shear reinforcement construction method for a PC box girder bridge according to claim 3 or 4, wherein in the shear reinforcement step, the steel plates are spaced apart so as not to constrain the axial force. The PC box girder bridge according to claim 5, wherein in the shear reinforcement step, the steel plate is fixed to the concrete frame using post-installed anchors, and the self-weight of the steel plate is borne by the post-installed anchors. Shear reinforcement method. In the shear reinforcement step, a steel plate with an eccentric head is used as the steel plate. The shear reinforcement construction method for a PC box girder bridge according to claim 5, characterized in that the steel plate with the eccentric head is fixed to the section by pressing it from above.

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