JP2006057352A - Method of repairing steel structure by using carbon fiber reinforced plastic board, carbon fiber reinforced plastic board for use in the method, and repaired steel structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of repairing a fatigue crack formed in a steel structure by using a carbon fiber reinforced plastic board (CFRP board). <P>SOLUTION: The method is applicable to repairing a crack occurring in the steel structure formed by boxing a gusset joint 2 to an out-of-plane area of a steel base material 1, at a location of a toe of the weld of the gusset joint. According to the method, at least the CFRP board 4 is stuck to both side surfaces of the gusset 2 and a plane of the base material 1 at the toe of the weld, in a manner forming a U-like shape, and at the same time the CFRP board 4 is intimately stuck to a weld bead 3 of a welding portion between the base material 1 and the gusset 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to the repair of steel structures such as steel bridges, and cracks in welds, particularly fatigue that occurs in the base metal near the toe of joint steel members called so-called gusset joints outside the base material. The present invention relates to a member for suppressing the progress of a crack and a repair method using the member.

  In recent years, many damages have been reported to each member of a steel bridge due to fatigue, corrosion, and the like due to vibrations, shocks, and the like accompanying an increase in the size of a vehicle and an increase in traffic. Moreover, in order to cope with an increase in load, many steel bridges require reinforcement. Once a fatigue crack occurs in a steel member, the crack gradually progresses and the main member may break. In particular, it is known that many cracks are concentrated at the welded joint of the steel plate.

  Conventionally, for repairing / reinforcing each member of such an existing steel bridge, a construction method in which a steel plate is fastened with a high-strength bolt or a steel plate is further welded is mainly used. However, such repair / reinforcement is often a narrow part where the joints of the members are complex and the workability is extremely poor in both high-strength bolted joints and welded joints. was there. Therefore, a simple and efficient construction method is desired.

  In response to such a request, in Patent Document 1, a fibre-reinforced synthetic resin sheet that can be easily carried is attached to a crack generated in a portion of a steel structure subjected to repeated stress, and the crack was discovered. A method for delaying the development of the is disclosed. Here, a method has been proposed in which an uncured prepreg sheet is applied to a steel structure and then cured by irradiation with heat or ultraviolet rays. In the Examples, a glass fiber reinforced synthetic resin prepreg is pasted and the delay rate of crack propagation is measured. It is disclosed that the crack growth rate is reduced to about 1/3 as compared with the case where a reinforcing sheet is not attached.

  However, this method merely suppresses the crack growth rate, and is implemented as a bridge until permanent repair. The permanent repair itself must be relied on the conventional method. In addition, in order to cure the prepreg, it is necessary to irradiate heat and ultraviolet rays, and there is a possibility that a sufficient effect cannot be obtained particularly in a narrow portion. In addition, the sheet is excellent in workability on site because of its high flexibility. However, since the sheet has a small amount of fibers per sheet, it needs to be laminated considerably in order to ensure sufficient rigidity.

On the other hand, Non-Patent Document 1 outlines the research results for the purpose of clarifying the applicability of carbon fiber reinforced resin plates (hereinafter abbreviated as CFRP plates) to repair and reinforcement of existing steel bridges. It is shown. With such a plate shape, V _f can be made larger than that of the sheet of Patent Document 1, so that the required rigidity can be easily obtained, and in the turn welded portion of the out-of-plane gusset targeted by the present invention. On the other hand, it is convenient in terms of workability to provide high rigidity to repair and reinforce. Here, as a result of evaluating the number of repetitions (remaining life) of the steel member having gusset from the time of crack occurrence until the time of breaking, the lower the stress range, the more effective the improvement of the remaining life by repair, the higher the stress range In this case, there is no repair effect due to the peeling of the CFRP plate at the initial stage, and from the viewpoint of preventive maintenance, the optimum application position of the CFRP plate is to bring the CFRP plate and adhesive into close contact with the weld bead. It is disclosed that the plastic strain region is most suppressed in a planar manner by pasting. Specifically, as shown in FIG. 7, a method of attaching the CFRP plate 104 to the end portion of the weld bead 103 on the steel base material 101 from both side surfaces of the gusset 102 to the crack occurrence point is good. Has been.

JP-A-2004-212338 Kazufumi Nakamura, “Study on Repair Method of Steel Members with Carbon Fiber Reinforced Plastic Sheet”, [online], [Search August 6, 2004], Internet <URL: http://www.metro-u.ac .jp / toku_kenkyu / 2002 / w / h-nakamura.pdf>

  Although the method according to the prior art has the effect of reinforcing the first-aid that delays the growth of cracks, it is desired to further suppress the crack growth rate and extend the remaining life.

  The object of the present invention is to investigate the method of attaching a CFRP plate, which is more effective in delaying the crack growth rate than the prior art, and further enables the application of a CFRP plate as a repair material. Particularly in the present invention, a carbon fiber reinforced resin plate is attached to a crack generated at the toe portion of the joint steel member in a steel structure in which the joint steel member is turned and welded out of the plane of the steel base material. It provides a method for repair.

  In order to solve the above problems, the present invention provides a carbon structure in which a crack generated at a toe portion of a joint steel member is formed in a steel structure in which the joint steel member is turned and welded out of the plane of the steel base material. A method of affixing and repairing a reinforced resin plate, wherein at least the carbon fiber reinforced resin plate is affixed to the both side surfaces of the joint steel member and the base material surface of the toe portion at the same time, A U-shaped inner side surface is attached in close contact with a weld bead of a welded portion between the base material and the joint steel member.

  The repair method according to claim 1, wherein a plurality of carbon fiber reinforced resin plates are laminated and pasted, and each of the carbon fiber reinforced resin plates to be stuck is in close contact with the weld bead.

  The repair method according to claim 1, wherein the carbon fiber reinforced resin plate is formed by previously laminating a plurality of prepregs.

  The carbon fiber reinforced resin plate has a substantially U-shaped opening, the opening is inserted from the toe of the joint steel member, and the inner surface of the opening is adhered to the weld bead and pasted. The repair method described above.

  Further, the present invention provides a steel structure in which a joint steel member is turned and welded out of the surface of the steel base material, and a crack generated in the toe base material of the joint steel member is pasted on the base material surface. A repair member made of a carbon fiber reinforced resin plate for repair, having a substantially U-shaped opening at one end of the resin plate, and an inner surface of the substantially U-shaped opening Also, the present invention relates to the repair member, wherein the repair member is in close contact with a weld bead surface of a welded portion of the joint steel member.

  Furthermore, the present invention relates to a steel structure in which a joint steel member is turned and welded out of the plane of a steel base material, and the steel structure is repaired by the repair method described above.

  According to the present invention, by affixing the CFRP plate by a specific method, the progress of fatigue cracks generated in the vicinity of the toe portion of the joint steel member, that is, the out-of-plane gusset, is remarkably suppressed, and the crack propagation according to the conventional technology From the reinforcement due to the delay, the prospect of application to the repair method was found.

  Although the CFRP plate used in the present invention has a specific gravity of about 1/5 that of steel, the tensile strength is about 6 times that of steel, and can be easily carried. Since it is a simple method of applying and sticking, it is easy to repair narrow portions.

  The steel structure to be repaired in the present invention is a so-called out-of-plane gusset in which a gusset is welded perpendicularly to the side surface of the steel material as a base material, and a fatigue crack is generated in the weld due to repeated stress. is there. In such an out-of-plane gusset, a fatigue crack is likely to occur from the toe of the corner welded portion of the gusset, and if left as it is, the crack progresses and the base material is broken.

The CFRP plate used in the present invention is, for example, a standard product (S type) 1.52 × 10 ⁵ N / mm ² or more, a medium elastic product in a tensile test method of carbon fiber reinforced resin according to JIS K7073. A material having a tensile modulus of 1.96 × 10 ⁵ N / mm ² or more is used for (M type), and 2.94 × 10 ⁵ N / mm ² or more is used for a highly elastic product (H type).

  In particular, it is desirable that the CFRP plate be formed by so-called pultrusion, in which a predetermined amount of carbon fiber is continuously drawn from a creel stand, aligned, and cured with a mold heated through a resin bath. Also, prepreg sheets in which fibers aligned in one direction are impregnated with resin are laminated in the same direction as required to obtain the desired strength, and this laminate is pressed and heated to cure the resin. Can also be obtained.

  In the present invention, as shown in FIG. 1, the CFRP plate is attached so as to cover both side surfaces and the toe end portion (longitudinal tip portion) of the out-of-plane gusset. In this example, since the gusset 2 is welded to both surfaces of the base material 1, the CFRP plates 4 are attached to both surfaces of the base material 1. When the gusset 2 is welded to only one side, a CFRP plate may be attached to the gusset welding surface as shown in the figure, and a CFRP plate may be attached to the opposite surface.

  In the example shown in FIG. 1, CFRP plates having different U-shaped opening widths and opening lengths are stacked. At this time, the one having a smaller opening width and opening length is used as the CFRP plate of each layer is laminated on the weld bead 3 in close contact with each other. Also, a laminated CFRP plate 4 integrally formed as shown in FIG. 2 is obtained by previously stacking prepreg sheets having different U-shaped opening widths and opening lengths to obtain a laminate, and curing the resin by applying pressure and heating. It can also be. Alternatively, a laminate is obtained by simply laminating a plurality of prepreg sheets, and after obtaining a laminated CFRP plate integrally formed by pressurizing and heating to cure the resin, it is cut into a shape along the weld bead shape. An opening may be formed.

  In the above example, an example of using a CFRP plate in which a U-shaped opening is formed has been shown. However, the present invention is not limited to this, and the final pasted state is substantially U-shaped by combining rectangular CFRP plates. You may do it. In this case, the CFRP plate to be attached to both side surfaces of the gusset has a length applied to the crack portion, and another CFRP plate is attached so as to cover the weld bead at the gusset toe end portion. In addition, since the shape of the weld bead does not necessarily become a linear rectangular shape, the “substantially U-shape” in the present invention means a shape that follows the shape of the weld bead on the gusset side surface and the toe end. . For example, the weld bead at the gusset toe portion is likely to have a curved shape as shown in FIG. 6, but the present invention includes a shape along such a shape. Of course, it is not necessary to completely match even the fine irregularities of the weld bead, and such fine irregularities can be easily followed by adjusting the application thickness of the adhesive.

  A room-temperature curable adhesive is used for attaching such a CFRP plate. In general, since the matrix resin of the CFRP plate is an epoxy resin, a preferable result is easily obtained when an epoxy adhesive is used. The adhesive strength of such an adhesive is not particularly limited, as long as the attached CFRP plate does not easily peel off. Moreover, the adhesive which protrudes after CFRP board sticking can be easily removed by wiping off before hardening.

  Prior to the application of the CFRP plate, the surface of the steel structure to be applied is peeled off or the exposed steel surface is subjected to a coupling treatment with an adhesion improver such as a silane coupling agent or a titanate coupling agent. It is also effective to do.

  The weld bead portion is also adjusted by polishing the shape with a grinder or the like, or conversely, the weld bead contact portion of the CFRP plate is polished to match the shape of the weld bead. It is also possible to improve the adhesion between the CFRP plate and the CFRP plate.

  The area of the CFRP plate attached to the base material is not particularly limited, but it is sufficient that at least an area capable of completely covering the generated crack is secured. For example, when using a CFRP plate in which a substantially U-shaped opening is formed, the width and length may be adjusted so that the crack is located at the center of the CFRP plate. Thickening the CFRP plate to be used is preferable because the structural stress concentration due to the gusset is reduced and the effect of smoothly transmitting the stress is obtained. For this reason, a thick CFRP plate may be used or a plurality of thin CFRP plates may be stacked so as to cover the weld bead to a predetermined thickness. Optimally, it is desirable to have the same thickness as the bead.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples.

<Preparation of test piece>
As shown in FIG. 1, gussets 2 (JIS SM400A, 100 × 9 × 140 mm) were turned and welded to both sides of the central part of steel plate base material 1 (JIS SM400A, 250 × 9 × 1040 mm) to prepare test pieces.

  Next, the test piece produced in this way is joined to the loading girder of the I-shaped section with a high-strength bolt, and the tensile stress is applied to the test piece by using the tensile region of the lower flange when the four-point bending loading of the simple girder is performed. It was set as the method of acting. The shape of the stress range in the fatigue test was a sine wave, the minimum stress was 20 MPa, and the maximum stress was changed. An electro-hydraulic servo actuator with a capacity of 1000 kN was used for loading.

  Loading was repeated to generate fatigue cracks. When the crack length a reached 15 mm on one side in the width direction from the center of the test piece, the loading was stopped, the test piece was once removed from the loading girder, and repair was performed by the following method.

<Repair method>
First, as a comparative example 1, repairing was performed on a crack generated from the weld toe by attaching a CFRP plate (25 × 1.2 × 100 mm) to each side of the gusset with an epoxy resin adhesive one by one (Fig. 6). The same was applied to the opposite side. In this method, repair is performed so that the CFRP plate is just applied to the tip of the crack where the stress concentration is the largest, and is a method disclosed in Non-Patent Document 1.

  On the other hand, in the repairing method according to the embodiment of the present invention, first, the cross-sectional shape of the weld bead is finished to be an 8 mm equivalent leg, and then a rectangular cut as shown in FIG. 1 is made in a CFRP plate (50 × 1.2 × 200 mm). Then, five CFRP plates were laminated step by step so that the cut portion was in close contact with the weld bead and affixed with an epoxy resin adhesive. The adhesion state of the CFRP plate at this time is shown in the cross-sectional photographs of FIGS. 3 corresponds to FIG. 1B, and FIG. 4 corresponds to FIG. 1C. As shown in FIG. 3, it can be seen that the crack 5 occurs in the base material near the gusset toe. In this example, the opening of the crack 5 is completely covered with a laminated CFRP plate, and the repair effect is expected to be enhanced by suppressing the opening displacement of the crack.

  The adhesive used here is a room-temperature curing type in both the comparative example and the example, and in order to suppress variations in the curing conditions of the adhesive, heat insulation was performed for 1 week after the CFRP plate was attached. Further, the surface of the base material to which the CFRP plate was attached was also surface treated using a grinder.

  Tables 1 and 2 show the mechanical properties of the steel plates and CFRP plates used and the physical properties of the adhesive, respectively. The CFRP plate used is a unidirectional reinforced resin plate having a thickness of 1.2 mm in which carbon fibers are arranged in one direction in the longitudinal direction and cured with resin.

<Fatigue test>
Thus, the repaired test piece (Comparative Example 1, Example) and the test piece not subjected to the repair process (Comparative Example 2) were returned to the loading girder and repeatedly loaded under the same conditions as described above. The number of repetitions (remaining life) until each test piece broke was measured. The results are shown in FIG.

  As can be seen from FIG. 5, by attaching a CFRP plate, it is possible to extend the remaining life to some extent in the low stress range even in Comparative Example 1, but according to the method of the present invention, the repair is remarkably excellent regardless of the stress range. The effect is recognized, and the remaining life reaches about 16 times that of the case where the repair process is not performed.

  In the examples of the present invention, the CFRP plate was not peeled until just before the total break, but in Comparative Example 1, the crack length from one side to the center was around 75 mm (a crack length of about 60% with respect to the full width). ).

  In the present invention, repair after the occurrence of a fatigue crack is described. However, by applying a CFRP plate in advance to the site where the occurrence of a fatigue crack is predicted by the method of the present invention, the occurrence of a crack It is also possible to extend the entire life until the final rupture, and it is also useful as a reinforcement.

  The scope of application of the present invention is not limited to existing structures such as steel bridges, but can also be used for gusset joint application sites such as ships.

It is a figure explaining the repair method of this invention, (a) is a top view, (b) is sectional drawing in the A-A 'line, (c) shows sectional drawing in the B-B' line. It is a perspective view which shows the external appearance of the lamination | stacking CFRP board used by this invention. It is a cross-sectional photograph which shows the adhesion state of the CFRP board in an Example, and is equivalent to FIG.1 (b). It is a cross-sectional photograph which shows the adhesion state of the CFRP board in an Example, and is equivalent to FIG.1 (c). It is a figure which shows the measurement result of the frequency | count of repetition from the time of repair to a fracture | rupture. It is a figure which shows the sticking method of the CFRP board by a prior art (comparative example 1).

Explanation of symbols

1 Base material 2 Gusset 3 Weld bead 4 Laminated CFRP plate 5 Crack

Claims (6)

  In a steel structure in which a joint steel member is turned and welded out of the plane of the steel base material, a crack generated at the toe of the joint steel member is repaired by attaching a carbon fiber reinforced resin plate. At least the carbon fiber reinforced resin plate is pasted on both side surfaces of the joint steel member and the base material surface of the toe portion in a substantially U shape, and at the same time, the substantially U-shaped inner surface is the base material. A repair method characterized by being adhered in close contact with a weld bead of a welded portion between the steel and the joint steel member.   The repair according to claim 1, wherein a plurality of the carbon fiber reinforced resin plates are stuck in a laminated manner, and each of the carbon fiber reinforced resin plates to be stuck is in close contact with the weld bead. Method.   The repair method according to claim 1 or 2, wherein the carbon fiber reinforced resin plate is formed by previously laminating a plurality of prepregs.   The carbon fiber reinforced resin plate has a substantially U-shaped opening, the opening is inserted from the toe of the joint steel member, and the inner surface of the opening is adhered to the weld bead and pasted. The repair method according to any one of claims 1 to 3, wherein:   In a steel structure in which a joint steel member is turned and welded out of the surface of the steel base material, a crack generated in the toe part base material of the joint steel member is attached to the base material surface for repair. A repair member made of a carbon fiber reinforced resin plate, having an approximately U-shaped opening at one end of the resin plate, and an inner surface of the approximately U-shaped opening being formed of the joint steel member. The repair member as described above, wherein the repair member is in close contact with a weld bead surface of a weld portion.   A steel structure obtained by turning and welding a joint steel member outside a surface of a steel base material, wherein the steel structure is repaired by the repair method according to any one of claims 1 to 4.