JPH04285247A - Prestress introduction member and prestress introduction method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prestress introducing member and a prestress introducing method that can be applied to repairing or reinforcing cracks in a member by introducing prestress into the member.

0002

[Prior Art] Conventionally, as a technique for repairing cracks etc. that have occurred in existing RC or PC structures and reinforcing the members, the surface of the member is coated with steel plate or fiber-reinforced plastic (FR).
There is a method of directly attaching a planar reinforcing material such as P) with adhesive. There is also a method (out-cable method using post-tension) in which a tension member such as a PC steel strand is placed outside the member to introduce prestress into the member. moreover,
There is also a method of introducing prestress into the member by attaching a planar reinforcing material such as a tensioned FRP sheet or high-tensile steel plate to the surface of the member using an adhesive.

0003

[Problems to be Solved by the Invention] However, the first method has the following problems. First, when simply attaching a reinforcing material to the surface of a member, the bending or shear reinforcing effect is obtained by the rigidity (size, thickness, Young's modulus) of the attached steel plate or FRP sheet itself. Among these, the Young's modulus is constant depending on the material, and the size is determined by the dimensions of the member, so the above-mentioned effect often depends on the thickness. For this reason, the thickness dimension increases (especially since FRP sheets are softer than steel plates,
(becomes thicker), is uneconomical, and has the disadvantage of spoiling the aesthetics. Furthermore, since steel plates are heavy, they have the drawback of poor handling and workability. In addition, it is possible to use steel plates or FRP without applying tension.
There is also the problem that because the reinforcement is simply pasting a plastic sheet, it cannot be expected to reduce the width of cracks, recover from deformation such as deflection of the member, or alleviate stress. Therefore, this method only has the function of preventing the damage from progressing beyond the current level.

[0004] Furthermore, the second method has the following problems. That is, since it is difficult to fix the general part of the tension material and the member, it is necessary to fix and fix the tension material only at both ends, and a large-scale reaction force plate or fixing device is required each time. In addition, since a reaction plate and a fixing device are required, the tendon must be placed at a distance from the surface of the member, resulting in a so-called "unbonded state" between the member and the general portion of the tendon. Therefore, when cracks occur due to excessive load, it is difficult to control the cracks by dispersing the cracks and reducing the width of the cracks. Furthermore, depending on the position of the reinforcing members, the tendons may be exposed to the outside of the structure, spoiling the appearance.

[0005] In the third method, when a bending test is performed on a member to which the reinforcing material is attached with an adhesive, the member may break under a load smaller than the designed proof strength of the member. Specifically, splitting cracks in the concrete occur from the ends of the member, and these splitting cracks become more prominent than the bending cracks that occur on the member's surface, eventually penetrating the member in the length direction and causing the member to break. There is. Such destructive properties occur due to the relationship between the concrete strength and the tension applied to the reinforcing material, and are more likely to occur when the concrete strength is low. For this reason, if the concrete strength of an existing structure has decreased due to deterioration or the like, simply pasting reinforcing material cannot sufficiently contribute to improving the strength of the member. Therefore, it is necessary to devise ways to prevent splitting and cracking of the concrete from occurring at the ends of the members.

The present invention has been made in view of the above-mentioned problems, and is capable of introducing prestress into a member with a simple structure, and also prevents fracture due to the propagation of splitting cracks that occur in the member due to the introduction of prestress. It is an object of the present invention to provide a prestress introduction member and a prestress introduction method that can prevent such damage and reinforce the member.

[0007]

[Means for Solving the Problems] Therefore, the prestress introducing member and prestress introducing method according to the present invention are such that a planar reinforcing material to which tension has been applied in advance is directly attached to the surface of the reinforced material using a jig. It is configured to be installed.

[0008] The reinforcing material may be attached to the surface of the material to be reinforced via an adhesive. Further, it is preferable that the mounting jig comprises an anchor means buried at a predetermined depth from the surface of the material to be reinforced. Further, the anchor means may be fixed to the reinforced material via a steel plate interposed on either the upper or lower surface of the reinforcing material.

[0009]

[Operation] According to the present invention, by attaching the planar reinforcing material to which tension has been applied in advance directly to the surface of the member using a mounting jig, a reaction force that tends to compress the member acts on the member. Prestress (compressive force) is introduced into the cross section.

[0010] A first embodiment of the present invention will be described below along with the implementation procedure with reference to FIGS. 1 to 9. This embodiment is a basic format for attaching reinforcing material to the lower surface of an existing bridge girder.

[Investigation and Design] (1) For existing members, investigate the occurrence of cracks and the amount of deflection. For newly installed members, the bending performance etc. required for the member are set. (2) Determine the prestress to be introduced into the member according to the investigation/examination results and design conditions shown in (1). (3) Determine the specifications of the reinforcing material. (4) Determine the type, shape, dimensions, quantity, and type of adhesive of the mounting jig based on the amount of tension to be applied, construction conditions, etc.

[Construction] Among reinforcement works for existing structures, the bridge girder 1 shown in FIGS. 1 and 2 will be exemplified here. (1) Drill a hole 7 at the installation location of the mounting jig K on the lower surface of the girder 1 installed between the supports 31 of the abutment 30 (near the support end of the girder 1) (FIG. 3). Mounting jig K around hole 7
A cut corresponding to the size and thickness of the steel plate portion 6 is performed. (2) Install the mounting jig K into the hole 7 (Fig. 4). The mounting jig K is illustrated with two sets of hole-in anchors 5 at one location. This mounting jig K plays the role of preventing splitting and cracking that occurs near the surface of the concrete member, similar to ordinary RC tension reinforcing bars. Installation jig K
A steel plate part 6 is installed, an adhesive 3 is applied to the surface of the steel plate part, and a reinforcing material 4, which will be described later, is attached. This results in
Cross-sectional damage can be prevented without drilling holes in reinforcing materials such as FRP sheets. Furthermore, even when the surface of a concrete member or the like is deteriorated and adhesives are not effective, reinforcing materials can be attached. (3) Apply adhesive 3 to the entire lower surface of girder 1, which is the reinforcing material attachment surface, including steel plate portion 6 (FIG. 5). (4) Pull the reinforcing material 4 with the required force using the reinforcing material attachment device 10 described later, and while maintaining this tensile force,
Attach the reinforcing material 4 to the lower surface of the girder 1 coated with adhesive 3 (Figure 6). (5) After the adhesive 3 has hardened, when the reinforcing material 4 is removed from the reinforcing material attachment device 10, a prestress (compressive force) is applied to the girder 1.
is introduced (Figure 7).

As shown in FIG. 6, the reinforcing material attachment device 10 includes a support portion (with an adjustment mechanism that can be expanded and contracted up and down) mounted on a base 11 on which wheels 15 are attached to the underside so as to be movable on a flat surface. A truss frame) 12 is placed, and both support parts 1
A reaction beam 13 is integrally attached to 2 and 12 to take the reaction force when the reinforcing material is pulled, and the length of the reaction beam 13 is adjusted according to the length of the reinforcing material. A telescopic jack 14 is equipped for this purpose. The reaction beam 13 is a long beam connected in series with bolts or the like, and its length is adjusted. A tension jig 16 for tensioning the reinforcing material is attached to both ends 13a, 13a of the reaction beam 13.

One end of this tensioning jig 16 is a U-shaped connecting portion 16a, and the other end is connected to a hydraulic jack 17 on the opposite side through an end 13a of the reaction beam 13. As shown in FIG. 8, an end jig 19 of the reinforcing member 4 is connected to the connecting portion 16a via a steel rod 18.

As shown in FIG. 9, this end jig 19 is a 2 piece that is integrated with the reinforcing material 4 by sandwiching the end of the reinforcing material 4 from above and below.
It is composed of two steel plates 20, 20, and both steel plates 20, 20 are provided with a through hole 21 through which the steel rod 18 is inserted vertically. In order to integrate the two steel plates 20, 20 with the ends of the reinforcing material 4, the adhesive 22 may be applied to the upper and lower adhesive surfaces, or they may be fastened with bolts and nuts 23, or both may be used in combination. Furthermore, a moving roller 22 is installed on the upper surface of the reaction beam 13, which is expandable and retractable in the height direction and movable in the axial direction of the reaction beam 13. The moving roller 22 moves the reinforcing material 4 stretched between both ends 13a, 13a of the reaction beam 13 laterally from below and presses it against the adhesive surface on the lower surface of the girder, thereby moving the reinforcing material 4 onto the girder 1. It is designed to be installed on the bottom.

In this embodiment, an example is shown in which the reinforcing material 4 is attached to the entire lower surface of the girder 1, but depending on the damage condition of the girder 1, the reinforcing material 4 may be attached partially.

FIGS. 10 and 11 show an applied version of the above basic model.

In this embodiment, as shown in FIG. 11, two reinforcing members 4, 4 are attached to the lower surface of the bridge girder 1 parallel to each other in the span direction, and the mounting jig K for the reinforcing members 4 is They are arranged in two rows per sheet of reinforcing material, and are arranged densely in the span direction of the girder 1. Further, the adhesive 3 is applied over the entire surface of the reinforcing material 4. However, when the mounting jigs K are closely arranged, it is sufficient to apply the coating only to the steel plate portion 6.

FIGS. 12 to 16 show specific examples of the mounting jig K, respectively.

The mounting jig K shown in FIG. 12 is composed of a hole-in anchor 5 buried in the lower surface of the girder 1 and a steel plate part 6 attached to the hole-in anchor 5. The steel plate portion 6 is integrally attached to the hole-in anchor 5 by screwing the threaded portion 6a protruding from the hole-in anchor 5 into the screw hole 5a of the hole-in anchor 5 facing the steel plate portion 6. The mounting jig K having such a shape may have a threaded portion 5b provided on the hole-in anchor 5 side and a threaded hole 6b provided on the steel plate portion 6 side, as shown in FIG. Furthermore, as shown in FIG. 14, the steel plate portion 6 may be attached to the hole-in anchor 5 using countersunk screws 40.

The mounting jig K shown in FIG. 15 includes a chemical anchor 41 (made of deformed reinforcing bars using epoxy resin or the like as a fixing agent) buried in the lower surface of the girder 1, and a steel plate part 6 shown in FIG. It is said to be composed of.

The mounting jig K shown in FIG. 16 is used when applying to a newly constructed structure, and the steel plate part 6, on which reinforcing deformed reinforcing bars 42 have been welded and fixed in advance, is attached during concrete pouring. The concrete member 50 is directly buried under the concrete member 50.

FIGS. 17 and 18 show details of how the reinforcing member 4 is attached.

As shown in FIG. 17, the concrete member 5
A hole-in anchor 5 of a mounting jig K is buried in the lower part of the hole-in anchor 5, and a steel plate portion 6 along the lower surface of the concrete member 50 is fixed to the hole-in anchor 5. A reinforcing material 4 is attached to the lower surface of the concrete member 50 with an adhesive 3 applied to the entire surface of the reinforcing material 4 to a constant thickness. In the installed state of the reinforcing material 4 as shown in FIG. The resistance force in the height direction of the member 50 increases, and the occurrence of splitting cracks can be effectively prevented.

Note that the steel plate portion 6 of the mounting jig K is shown in FIG.
It may also be buried in the concrete surface. In this case, if it is an existing concrete member, the location 43 corresponding to the steel plate portion 6 is cut and set.

[0026] In addition, for newly installed concrete members, Fig. 1
The mounting jig K shown in FIG. 6 is placed on the formwork 44 as shown in FIG. 19, and is buried in the surface of the concrete member 50 by pouring concrete as shown in FIG. 16.

Next, the dimensions of each part of each mounting jig K are determined as follows. Taking the installation jig K in Fig. 17 as an example,
First, the embedded length of the hole-in anchor 5 is set so that the distance from the virtual position A of the splitting crack to the upper end of the hole-in anchor 5 is a length that allows the hole-in anchor 5 to sufficiently exhibit its pull-out strength.

Next, the bolt diameter φ2 and the number of bolts of the steel plate portion 6 are set as follows since this portion is a place that receives the reaction force of the tension force of the reinforcing member 4. For example, the allowable shear stress for steel materials is 8 per square centimeter in the long term.
00 kg, it can handle 5.6 tons with φ2 = 30 mm. Also, if φ2 = 50 mm, it can handle 15.7 tons. Therefore, if the reaction force P is 60 tons and φ2 is 50 mm, 60/15.7=3.8 bolts, or 4 bolts are required. In this way, the bolt diameter φ2 and the number of bolts may be determined according to the tension force. FIG. 20 shows an example in which four steel plate parts 6 of the mounting jig are set at the fixing locations of the reinforcing material. Also,
FIG. 21 shows an example in which the flat head screws 40 of FIG. 14 are used, and four flat head screws 40 are used in one steel plate portion 6.

According to the prestress introduction method of the present invention,
It has the following effects over the out-cable method using post-tension.

(1) Since the reinforcing member 4 only needs to be tensioned while the reinforcing member 4 is attached and fixed to the surface of the member, a very simple jig is required for tensioning. (2) Since the reinforcing material 4 is attached to the surface of the member over the entire surface of the reinforcing material, there is no need for any large-scale reaction plate or fixing device as a permanent member at the end of the reinforcing material. (3) Because the structure directly introduces prestress from the surface of the member where the tensile stress generated in the member is greatest,
Excellent reinforcement effect for members. Due to this reinforcing effect, in order to obtain the same effect as the conventional reinforcing effect, it is possible to
P sheets need to be thin, and FRP sheets in particular can be expected to be even thinner and lighter, so they can be used in repair and reinforcement work, which is often applied to areas where workability is poor, such as the bottom and sides of parts. becomes extremely easy. (4) Although the reinforcing material 4 is exposed on the surface of the member, it is not separated as in the out-cable method, but is integrated, so there is no discomfort with the member and the appearance is not spoiled. (5) The ability to control and suppress cracking of concrete members and their durability are improved. In particular, since the present invention has a structure in which the reinforcing material 4 is directly attached to the surface of the member where cracks are likely to occur over its entire surface, the reinforcing material 4 and the concrete member are integrated into a so-called bonded state, and this bonded state The reinforcing material 4 used in this invention has an excellent ability to suppress and control cracks by dispersing the cracks and reducing their width when cracks occur due to excessive load or the like. (6) In addition, even through minute cracks on the surface of concrete, moisture, salt, CO2, etc. enter the concrete, which gradually causes deterioration of the material, such as carbonation and corrosion of steel materials such as reinforcing bars. According to the present invention, it is possible to prevent the intrusion of such deteriorating factors, and it is also possible to improve the durability of the member. In particular, F.R.
The P sheet is a highly durable material with excellent corrosion resistance.
In addition to reinforcing the strength of components, it also functions to improve durability. On the other hand, steel plates can also provide the same functionality by taking corrosion allowances into account and painting them. (7) It is possible to alleviate the temporal decrease in prestress introduced into the member. The fixing device at the end of the out-cable method includes:
As time passes, there are some cases in which tension members such as PC steel strands may pull out minutely. At this time, the general part of the tendon material and the member are in an unbonded state, so this minute amount of slippage is
This results in a reduction in the elastic strain of the general portion of the tendon, which immediately results in a reduction in the prestress introduced into the member. In contrast, in the present invention, the entire surface of the reinforcing material (tension material) is
It is in a bonded state where it is attached to the member with adhesive 3. Therefore, even if a minute creep deformation occurs in the adhesive 3 in the steel plate part 6 of the mounting jig K shown in the basic form of FIG.
It is transmitted to the adhesive 3 and reinforcing material 4 in a very small area adjacent to each other. Therefore, there is a structural effect that does not result in a reduction in prestress over the entire length of the reinforced member.

[0031] In addition, the tensioned reinforcing material 4 is bonded to the adhesive 3.
The method of introducing prestress into a member simply by pasting it has the following effects.

(1) When the member is made of concrete, wood, etc., the ends are reinforced so that the reinforcing material 4 and the member are integrated. Therefore, it is possible to prevent the member from breaking under a load smaller than its designed proof strength due to splitting and cracking of the end of the member itself, and the performance of the member can be fully exhibited. Furthermore, since it can be attached without making holes in the reinforcing material 4, the maximum reinforcing effect can be obtained with the minimum amount of reinforcing material. When drilling holes, there may be cross-sectional defects,
In FRP sheets, fibers may be cut, so it is necessary to increase the width and thickness of the reinforcing material. In particular, in this example, in the direction perpendicular to the splitting crack direction at the end of the member,
By driving a hole-in anchor or chemical anchor with sufficient length, sufficient tensile resistance can be ensured. (2) Even when the surface of the general part of a concrete member has deteriorated and it is difficult to apply adhesive, install the mounting jig K in the general part and use the steel plate part 6 to apply the adhesive. Therefore, the reinforcing material 4 can be easily attached. (3) As a result of the above effects, even in existing concrete structures that have already developed cracks and become obsolete, the bearing capacity of the members is improved by reducing the width of cracks, recovering from deformation such as deflection, and alleviating stress. It can continue to be used as a mechanically reliable member. (4) Furthermore, when performing seismic reinforcement of existing piers and walls, the conventional method of pouring additional concrete into the piers and walls to create a composite structure increases their own weight, and the foundation itself must be reviewed. , may require reinforcement,
The present invention can be easily carried out by simply attaching a tensioned steel plate or FRP sheet, with almost no increase in its own weight.

[0033] The prestress introduction method according to the present invention described above may be used for repairing and reinforcing existing structures. Examples include reinforcement of bridge decks and beams, seismic reinforcement of bridge piers, and reinforcement of building decks and beams. In addition, as an application to newly constructed PC structures, post-tension type PC girders, linear motor car girders (
(Making use of its non-magnetic properties) and concrete factory products are also possible.

22 to 24 show the case where the mounting jig K is used only as a bolt-like anchor means, and FIGS. 22 and 23 show the case where the mounting jig K is used only as a bolt-like anchor means, and FIGS. 2 shows a method of processing the end portion 4a of the .

FIG. 22 shows that the reinforcement effect is improved by reinforcing the end portion 50a of the concrete member 50 or the like using a mounting jig K, and by inserting a thin iron plate 52 between the end portion 4a of the reinforcing material 4 made of an FRP sheet or the like. Although the figure shows a bonded state with adhesive 3 applied thereto, adhesive 3 may not be necessary in some cases. FIG. 23 is an example in which the reinforcing effect is improved by thickening the end portion 4a from the outside of the reinforcing material 4 made of an FRP sheet or high-tensile steel plate with an FRP sheet or steel plate 53. In some cases, it may not be necessary. When using a steel plate, a hole for a mounting jig is made in advance, and the mounting jig K is driven into the hole to fix it. F
The RP sheet is fixed at the site by driving a mounting jig K through the FRP sheet. In both FIGS. 22 and 23, only adhesive may be used in the sections excluding the ends. Furthermore, in order to integrate with the surface of the concrete member, the surface can be pretreated by impregnating it with a polymer or the like.

The case shown in FIG. 24 is an example in which the reinforcing material 4 made of a high-tensile steel plate or the like can be integrated with the member using the mounting jig K without using adhesive. Since the adhesive 3 is arranged in

[0037]Furthermore, the FRP sheet or high tensile strength steel plate is
This has the effect of reducing prestress loss of the member. That is, concrete, wood, etc. that have been subjected to prestress tend to shrink further due to creep or drying shrinkage that occurs over time. At this time, the strain of the tension member that tries to compress the member decreases, resulting in a loss of prestress. Therefore, in order to reduce the loss of prestress in a member, it is necessary to use a material with high elongation performance (large strain) that is less susceptible to strain reduction due to creep or drying shrinkage, such as an FRP sheet or a high-tensile material. You can use steel plate.

Members such as beams, slabs, and columns can be considered as members to which prestress is introduced by reinforcing materials. The material may be concrete, wood, or metal such as aluminum. The concrete may be unreinforced, RC, PC, or FRC. In addition, polymer-based adhesives are suitable for the adhesive, and the anchor means can be used if the member and the reinforcing material can be integrated.
Either is fine.

[0039]

[Effects of the Invention] As explained above, according to the present invention, the following excellent effects can be achieved. This method introduces prestress from the surface of the reinforced material into the interior by directly attaching a planar reinforcing material to which tension has been applied in advance to the surface of the reinforced material using a mounting jig, reducing the width of cracks in the member. It is possible to expect deformation recovery and stress relaxation of the deflection of the member, improve the effects of repair and reinforcement of the member, improve the holding strength of the member, and obtain a mechanically reliable member. Further, it is possible to improve workability and economical efficiency when introducing prestress to a member. Furthermore,
It does not spoil the scenery. In addition, the mounting jig consists of an anchor means buried at a predetermined depth from the surface of the material to be reinforced, so that it can effectively prevent the occurrence of splitting cracks due to the introduction of prestressing and destruction due to their propagation. be effective.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing a girder of a bridge showing one embodiment of the present invention.

FIG. 2 is a back view of the same girder.

[Fig. 3] Fig. 3 is a construction procedure diagram of the same girder.

FIG. 4 is a construction procedure diagram of the same girder.

FIG. 5 is a construction procedure diagram of the same girder.

FIG. 6 is a construction procedure diagram of the same girder.

FIG. 7 is a construction procedure diagram of the same girder.

FIG. 8 is a diagram of main parts of a prestress introduction device.

FIG. 9 is a sectional view of a main part of FIG. 8;

FIG. 10 is a diagram showing an application type of the same digit.

FIG. 11 is a back view of the same girder.

FIG. 12 is an installation diagram of a mounting jig.

FIG. 13 is an installation diagram of a mounting jig.

FIG. 14 is an installation diagram of a mounting jig.

FIG. 15 is an installation diagram of a mounting jig.

FIG. 16 is an installation diagram of a mounting jig.

FIG. 17 is an installation diagram of a mounting jig.

FIG. 18 is an installation diagram of a mounting jig.

FIG. 19 is an installation diagram of a mounting jig.

FIG. 20 is a layout diagram of a mounting jig for a member.

FIG. 21 is a diagram showing another example of the configuration of the mounting jig.

FIG. 22 is a diagram illustrating a method of processing the end portion of the reinforcing material.

FIG. 23 is a diagram illustrating a method of processing the end portion of the reinforcing material.

FIG. 24 is a diagram illustrating a method of processing the end portion of a reinforcing material.

[Explanation of symbols]

1 digit 3. Adhesive 4 Reinforcement material 5 Anchor means 6 Steel plate part K Mounting jig

Claims (5)

[Claims] 1. A prestress introduction member characterized in that a planar reinforcing material to which tension is applied in advance is directly attached to the surface of a reinforced material via an attachment jig. [Claim 2] Prestress is introduced from the surface of the material to be reinforced into the interior by directly attaching a planar reinforcing material to which tension has been applied in advance to the surface of the material to be reinforced via a mounting jig. How to introduce prestress. 3. The prestress introducing method according to claim 2, wherein the reinforcing material is attached to the surface of the reinforced material via an adhesive. 4. The prestress introducing method according to claim 3, wherein the mounting jig comprises anchor means buried at a predetermined depth from the surface of the material to be reinforced. 5. The prestress introduction method according to claim 4, wherein the anchor means is fixed to the reinforced material via a steel plate interposed on either the upper or lower surface of the reinforcing material.