JP4864552B2 - Steel structure reinforcing method and reinforcing structure - Google Patents

Description

  The invention according to the claims relates to a method of reinforcing a steel structure such as a bridge or an elevated road for the purpose of dealing with, for example, an increase in traffic volume, and a reinforced steel structure.

  As a means for reinforcing a steel structure such as a bridge, a method of attaching a steel material to a necessary portion on an existing steel member by welding or a bolt is well known. However, according to such a construction method, it is necessary to exert a thermal effect on an existing steel member or to make a bolt hole, so that the strength is reduced accordingly. Moreover, it is common that the effect of the reinforcement by this method is thin with respect to a compression member among steel structures.

  From such a point, conventionally, a method as shown in FIG. 4 using concrete or the like has been adopted as a reinforcement for a rod-shaped member that can receive a compressive force in a steel structure. That is, when the rod-shaped member is, for example, a hollow square box-shaped steel base material 2 as shown in FIG. 4 (a), in order to reinforce it, concrete is placed outside the base material 2 as shown in FIG. 4 (b). 4 'is wound, or the outer side of the concrete 4' is covered with a reinforcing steel plate (concrete formwork) 3 'as shown in FIG. 4 (c).

  The reinforcement by the method of FIG. 4B is called “SRC structure” and is widely adopted, and the concrete 4 ′ is wound around the base material 2 by using a normal formwork (not shown). (Remove the formwork after construction). Further, the reinforcement of FIG. 4C is called “SRC + S structure” or the like, and a steel plate cylindrical formwork 3 ′ also serving as a reinforcing member is attached around the base material 2, and then the base material 2. Concrete 4 'is filled between and the mold 3' (the mold 3 'is not removed). When the proof stress in the case of only the base material 2 is 1.0, generally, the proof strength is about 1.2 by the SRC structure, and the proof strength is increased to about 1.7 by the SRC + S structure.

In addition, the following Patent Document 1 proposes a composite steel frame material in which a steel base material such as a square steel pipe is covered with a coating layer of carbon fiber reinforced plastic. FIG. 5 shows an outline thereof, in which the reference numeral 2 is a steel base material, and the reference numeral 6 is a coating layer of carbon fiber reinforced plastic.
JP 2000-64505 A

  When trying to obtain a high reinforcing effect for the rod-shaped member of the steel structure, the reinforcement (SRC + S) shown in FIG. However, the reinforcing method of FIG. 4C has problems in the following points. In other words, it is necessary to provide an opening for filling concrete inside the mold, but due to the opening, the reinforcing effect may be weakened or the concrete may not be able to exhibit a sufficient service life. obtain. For example, if there is an opening, the wall distance between the molds between them tends to increase, and the mold and the concrete may peel off. When peeling occurs, both the formwork and the concrete cannot be combined to exhibit strength, and the reinforcing effect may be weakened. Further, when a tensile or bending load is applied to the rod-shaped member, the strain tends to increase in the opening portion, so that it is considered that cracks are likely to occur in the concrete. Furthermore, since water easily penetrates between the mold and the concrete through the opening, the mold may be easily rusted or the concrete may be deteriorated. On the other hand, when such an opening is made small, it becomes impossible to observe the concrete filling condition between the mold and the base material, and the construction becomes difficult.

  In addition, the composite steel frame described in Patent Document 1 may be used when a new steel structure is constructed, but is difficult to employ when reinforcing an existing steel structure. This is because it is difficult to integrate the coating layer of carbon fiber reinforced plastic so as to cover the entire surface of the rod-shaped member incorporated in the steel structure. In addition, such a composite steel frame has a disadvantage that a considerable cost is involved.

  The invention according to the claims is configured to realize the reinforcement of the existing steel structure so as to obtain a high reinforcement effect smoothly at a relatively low cost in consideration of the above points.

The method for reinforcing a steel structure according to the claim is:
1) Surround the outside of the rod-shaped member in the steel structure with a steel plate cylindrical formwork (also serving as a reinforcing member) having an opening on a part of the side surface (circumferential surface).
2) After filling the above formwork (that is, between the rod-shaped members) with concrete so as to wind the rod-shaped members, and after the concrete solidifies,
3) The FRP sheet that closes the opening is adhered to the surface of the concrete in the opening and the formwork surface (portion around the opening) of the opening edge so that there is no gap.

This reinforcing method is similar to that shown in FIG. 4 (c), in which a steel plate-shaped cylindrical formwork that also serves as a reinforcing member is attached to the periphery of the base material, and the concrete is placed between the base material and the formwork. And the formwork is attached as it is. Therefore, as described above, it is estimated that the rod-shaped member that can receive the compressive force can be effectively reinforced, and the proof stress can be increased by about 1.7 times compared to the case of using only the base material.
However, this reinforcing method is further characterized in that the opening of the form 1) used for filling the concrete 2) is closed with an FRP sheet according to 3). When the FRP sheet is bonded to the surface of the concrete exposed from the opening and the formwork surface of the opening edge as in 3) above, the following preferable effects are brought about.
a) Based on the mechanical strength of the FRP sheet (especially the tensile strength in the direction of the width of the rod-shaped member), the opening is prevented from spreading, and therefore the gap between the molds that sandwich the opening is prevented from spreading. Is done. Therefore, the steel plate formwork and the concrete do not peel off, and both exhibit preferable strength as an integral composite material.
b) Even when a tensile or bending load is applied to the rod-shaped member, the strain is also observed at or near the opening based on the mechanical strength of the FRP (particularly the tensile strength in the direction of the length of the rod-shaped member). Therefore, cracks in the concrete are prevented from occurring.
c) Since the FRP is bonded so that there is no gap as described above, it is possible to prevent water from penetrating into the formwork and concrete through the opening. When water permeation is thus prevented, the formwork is prevented from being rusted or the concrete is deteriorated, and the reinforcing effect is maintained for a long time.
d) As described above, since the reduction in the reinforcing effect and the shortened service life due to the opening are prevented, the opening can be formed large. If the opening can be enlarged, the condition of filling the concrete into the formwork through the opening can be easily observed. Therefore, the ease and certainty of the construction including the filling work are improved.
e) Reinforcement method mainly using formwork made of concrete or steel plate, because the amount of special materials (carbon fiber reinforced plastic and other FRP sheets) used is smaller than the method of Patent Document 1. The cost required for reinforcement is low.

As the cylindrical formwork shown in 1) above, in particular, the cross section has a quadrilateral shape and an opening corresponding to one side thereof is opened (therefore, there is a continuous opening in the length direction of the rod-shaped member). A U-shaped cross section is preferably used. FIG. 1 shows an example of using such a formwork.
With such a mold, since the opening is large, filling of the concrete between the mold and the rod-shaped member can be performed smoothly and reliably while observing the filling state.

As the FRP sheet, it is advantageous to use a sheet in which reinforcing fibers are arranged in two directions (that is, two directions in the longitudinal direction and the lateral direction in the plane of the sheet).
When such an FRP sheet is used so that the direction of the reinforcing fiber coincides with the width direction and the length direction of the rod-shaped member, the reinforcing fiber in each direction effectively suppresses the spread of the opening and forms the form. Prevents the concrete from cracking and prevents the concrete from cracking against tension and bending acting on the rod-shaped member. In addition, there is also an advantage that the effect of preventing water penetration is prolonged by preventing the occurrence of cracks in the resin of the FRP sheet.

Adhesion of the FRP sheet was performed by applying an impregnating adhesive (such as epoxy resin) to the surface of concrete and formwork, and before it solidified, a reinforcing fiber sheet (carbon fiber or other reinforcing fiber was made into a cloth-like thin sheet. In this case, the resin is not impregnated) and the impregnated adhesive is applied thereon (at this time, for example, the impregnated adhesive is infiltrated between the fibers using a roller or the like). Such a procedure may be repeated when a plurality of reinforcing fiber sheets are laminated in order to increase the strength.
When the FRP sheet is bonded in this manner, it is easier and more reliable to bond to the surface of the concrete in the opening and the formwork surface of the opening edge than using a pre-solidified FRP sheet. Depending on the position of the opening in the mold, it may be necessary to bend a part of the FRP sheet (for example, the example in FIG. 1). From such a point, the penetration of water into the interior of the formwork or concrete is also reliably prevented.

As the reinforcing fiber of the FRP sheet, carbon fiber (PAN-based or pitch-based carbon fiber), metal fiber (boron fiber, titanium fiber, steel fiber, etc.), glass fiber (glass fiber fiber) or organic fiber (aramid, PBO ( (Polyparaphenylenebenzbisoxazole), polyamide, polyarylate, polyester, etc.) may be used singly or in a mixture of a plurality of types.
These reinforcing fibers have high strength and Young's modulus, and provide an effective reinforcing action by being bonded as FRP sheets to the surface of concrete or the formwork surface of the opening edge. Regardless of the type of reinforcing fiber used, the resin part of the FRP sheet may be a room temperature curing type or thermosetting type epoxy resin, acrylic resin, vinyl ester resin, MMA resin, unsaturated polyester resin or phenol resin. Etc. can be used by impregnating between the fibers.

The above-mentioned formwork before filling with concrete is supported on each part of the surface of the bar-shaped member by a support member (which should be of a size that does not discontinuously divide the inside of the formwork) attached to the outside of the bar-shaped member. It is preferable to hold at a position where an interval (for example, an interval of about 50 to 200 mm) is provided. FIG. 2 shows an example in the case of holding the formwork as such.
It is desirable that there is an interval of about 50 mm or more between each part of the surface of the rod-shaped member and the mold for the convenience of filling the concrete with every corner. In order to provide such a space around the entire area of the rod-shaped member, it is necessary to support the mold frame in a floating state so as not to directly contact the rod-shaped member. If the formwork is held using the support member as described above, the formwork support necessary for properly filling the concrete can be achieved.

The reinforcing structure of the steel structure according to the claims is such that the outside of the rod-shaped member in the steel structure is wrapped with concrete, and the outside is surrounded by a cylindrical formwork made of steel plate having an opening on a part of the side surface. The concrete surface of the opening and the formwork surface of the opening edge are covered with a FRP sheet bonded so as to close the opening without any gap.
In such a reinforcing structure, the rod-shaped member as a base material is reinforced by a concrete and steel plate formwork, and generally by an FRP sheet having mechanical strength (tensile strength, etc.) equal to or higher than steel. Similar to the SRC + S structure shown in c), it is considered that the yield strength is increased by about 1.7 times compared to the case of using only the base material.
In addition, according to this reinforcing structure, the opening portion and the like are covered with the FRP sheet, so that the opening is prevented from spreading, the generation of strain is suppressed, and the penetration of water is prevented. Therefore, the operational merits a) to e) are brought about.

  According to the reinforcing method and the reinforcing structure of the claimed invention, the reinforcement of the steel structure with respect to the rod-shaped member has the advantage that the reinforcing effect is high, the reinforcing effect lasts for a long time, and the construction is easy and low cost. Can be done with. In the reinforcing method and the reinforcing structure of the invention, a) a steel sheet formwork and concrete exhibit a preferable strength as an integral composite material without peeling, b) the occurrence of cracks in the concrete is prevented, c) The penetration of water does not rust the mold or deteriorate the concrete, d) Easily and reliably fill the mold into the concrete, e) The cost of reinforcement due to the low use of special materials This is because there is an operational characteristic such as low ----.

  1 to 3 show an embodiment relating to an embodiment of the invention. FIG. 1 is a cross-sectional view conceptually showing a reinforcing structure 1 applied to a base material 2 which is a rod-shaped member in a steel structure. FIG. 2 shows a state in which the formwork 3 is attached to the base material 2 in the construction process of the reinforcement structure 1 (concrete is not filled). FIG. ) Is a detailed view of part b in FIG. 9A, and FIG. 10C is a detailed view of part c in FIG. 3 (a) and 3 (b) are diagrams illustrating a steel structure to be reinforced.

A reinforcing structure 1 shown in FIG. 1 is obtained by applying the following reinforcement to a steel base material 2 formed in a hollow square (quadrangle) box shape. That is,
・ The outside of the base material 2 is wrapped with concrete 4. The thickness of the concrete is preferably about 50 to 200 mm, but in this example 140 to 160 mm.
The outer side of the concrete 4 is surrounded by a cylindrical form 3 made of steel plate that is in close contact therewith. The mold 3 is used as a mold for filling the concrete 4 and winding it around the base material 2. However, the mold 3 is not removed after the concrete 4 is applied, and is used as a reinforcing member as it is. Although it is cylindrical, the mold 3 has a quadrilateral cross section like the base material 2, and has a “U” -shaped cross section with one side of the opening 3X. Each surface (each side in the cross-sectional view) is arranged so as to be parallel (or almost parallel) to each surface (each side in the cross-sectional view) of the base material 2, and the opening 3X is positioned vertically upward. .
The FRP sheet 5 having a dimension extending over both sides of the mold 3 from the surface of the concrete 4 exposed from the opening 3X to the surface of both side edges of the opening 3X is bonded. As the FRP sheet 5, a thin sheet having a thickness of 1.0 mm or less in which reinforcing fibers such as carbon fibers are arranged in two vertical and horizontal directions is used. The sheet 5 is adhered to the surface of the concrete 4 and the edge surface of the mold 3 without a gap, and the width of the sheet 5 is wider than the width of the upper surface of the mold 3 so that Both end portions are bent so that they are also bonded to the vicinity of the upper ends of both side surfaces of the mold 3.

  This reinforcing structure 1 can be applied to various existing steel structures. For example, as shown in FIG. 3, it is applied to a truss bridge to reinforce its upper chord material, lower chord material or diagonal material, or applied to an arch bridge to reinforce its arch ribs and vertical members, etc. The member can be effectively reinforced. This is because the steel plate mold 3 and the FRP sheet 5 resist the tensile force, and the concrete 4 can resist the compressive force.

Moreover, the reinforcing structure 1 of FIG. 1 has the following effects based on the presence of the large opening 3X in the mold 3 and covering the portion with the FRP sheet 5. That is,
-Since the opening 3X is large, the state of filling the concrete 4 into the mold 3 through the opening 3X can be observed well, and therefore the concrete 4 can be wound smoothly and reliably.
-Based on the mechanical strength of the FRP sheet 5 (mainly the tensile strength in the width direction of the base material 2), the mold frame 3 is prevented from spreading in the width direction across the opening 3X. The concrete 4 does not peel off and exhibits a preferable strength as an integral composite material.
-Based on the mechanical strength of the FRP sheet 5 (mainly the tensile strength in the length direction of the base material 2), the strain in the length direction of the base material 2 is suppressed, and therefore cracking of the concrete 5 is prevented. Is done.
-Since the FRP sheet 5 is adhered to the concrete 4 and the formwork 3 without a gap, penetration of rainwater and the like through the opening 3X is prevented, and rusting of the formwork 3 and deterioration of the concrete are prevented.

Hereinafter, the construction procedure of the reinforcing structure 1 of FIG. 1 will be described using FIGS. 2 (a) to 2 (c) and the like.
i) First, a support metal 2a for concrete is attached to the entire surface of the steel base material 2. The support metal 2a is a member for fixing the concrete 4 to the surface of the base material 2, with an interval of about 100 to 200 mm between adjacent ones, and the ends of the shafts of the many support metal 2a are used as the base. Weld to the surface of the material 2.
Further, attachment members 2b and 2c are also attached to the surface of the base material 2. The attachment members 2b and 2c are members for holding the mold 3 in a state of being spaced from the base material 2 so as to be filled with the concrete 4, and are formed of an angle material or the like and welded to the base material 2. Install using stud bolts 2d. In the example of FIG. 2, the attachment member 2b is attached to the lower part of the base material 2 so as to protrude downward (see FIG. 2C), and the attachment member 2c is attached to the upper part of the base material 2 so as to protrude laterally. (See FIG. 2 (b)).

ii) A cylindrical form 3 made of steel plate is attached to the outside of the base material 2. As described above, the mold frame 3 has a quadrilateral cross section, and has three sides of a “U” shape with one side portion being an opening 3X (however, in addition to the three sides, on both sides of the opening 3X) It has a narrow edge 3Y). The thickness of each surface is about 4 to 12 mm, and reinforcing members 3a made of an angle material are attached to a plurality of locations on the inner surface by welding in order to maintain the shape.
When the mold 3 is attached as a single unit, the vicinity of the bottom cannot be connected to the base material 2 (for example, it cannot be coupled to the mounting member 2b). Therefore, the bottom 3A and the side 3B (the edge 3Y are connected to each other). Including them), and they can be connected and separated. Therefore, the mold 3 is attached by the following procedure. That is, first, as shown in FIG. 2 (c), the base material 2 is obtained by connecting the bottom 3A of the mold 3 to the mounting member 3b provided on the inner surface and the mounting member 2b on the base material 2 by the connecting tool 3d. Connect to In addition, side portions 3B provided on both sides are connected to base material 2 and bottom portion 3A. As shown in FIG. 2 (b), the side member 3B and the base material 2 are connected to each other by attaching the attachment member 3c provided on the inner surface of the side part 3B to the attachment member 2c on the base material 2. The side 3B and the bottom 3A are connected by connecting the bolt 3f from the outside to the nut 3e fixed to a part of the bottom 3A by welding as shown in FIG. 2 (c). To do.

iii) The concrete 4 is filled between the base material 2 and the mold 3 from the upper opening 3X. The filling is performed so that the concrete 4 spreads to every corner in the mold 3 while observing the filling condition in the vicinity of the bottom 3A of the mold 3 and the like.
When the concrete 4 is sufficiently filled until it reaches the opening 3X, the surface 4a of the concrete 4 in the opening 3X is flattened and between the edge 3Y of the mold 3 as shown in FIG. Finish so that there are no steps or grooves and wait for the concrete 4 to solidify.

iv) When the concrete 4 is hardened, the FRP sheet 5 is bonded to the concrete 4 exposed from the opening 3X of the mold 3 and the periphery thereof as shown in FIG. The FRP sheet 5 is constituted by, for example, impregnating a reinforcing fiber sheet made of carbon fiber with an epoxy resin on site, and the adhesion is performed so that no gap is formed between the concrete 4 and the edge 3Y. Follow the procedure.
First, an impregnation adhesive made of an epoxy resin is applied to the surface of the concrete 4 and the surface of the mold 3 (the edge 3Y along the surface of the concrete 4 and the upper portion of the side perpendicular to them). Prior to solidification, a reinforcing fiber sheet (cloth-like one having a thickness of about 0.1 to 0.3 mm) which is not impregnated with resin is stacked. According to FIG. 1, the reinforcing fiber sheets are folded and overlapped at two places on both sides. Then, before the adhesive is solidified, the same impregnating adhesive is applied on the reinforcing fiber sheet, and the adhesive is infiltrated between the fibers using a roller or the like. When the adhesive is solidified, the above-described reinforcing structure 1 is completed.

  The present invention can be practiced without being limited to the form introduced above. For example, the cross-sectional shape of the base material (and hence the cross-sectional shape of the formwork), the thickness of the concrete, the FRP sheet (reinforced fiber or resin) The type etc. can be changed.

It is a figure which shows embodiment of invention, and is a cross-sectional view which shows notionally the reinforcement structure 1 given to the base material 2 in a steel structure. FIG. 2 shows a construction process (before filling with concrete) of the reinforcing structure 1 in FIG. 1, FIG. 2 (a) is a cross-sectional view of the whole, FIG. 2 (b) is a detailed view of a part b in FIG. ) Is a detailed view of part c in FIG. FIGS. 3A and 3B are schematic views illustrating a steel structure to be reinforced by the invention. 4A, 4B, and 4C are schematic cross-sectional views showing a steel base material and a conventional general reinforcing structure corresponding thereto. It is a perspective view (Drawing 5 (a)) and a transverse cross section (Difference (b)) showing a composite steel frame material which strengthened a base material indicated in patent documents 1.

Explanation of symbols

1 Steel structure 2 Base material (bar-shaped member)
3 Formwork 3X Opening 4 Concrete 5 FRP sheet

Claims (6)

The outside of the rod-shaped member in the steel structure is surrounded by a steel plate- shaped cylindrical form having a U-shaped cross section with an open upper portion corresponding to one side of the quadrilateral cross section ,
While observing from the opening, after filling the concrete through the opening into the mold like winding a rod-shaped member, after the concrete solidified,
A method for reinforcing a steel structure, characterized in that the FRP sheet that closes the opening is bonded to the surface of the concrete in the opening and the formwork surface of the opening edge so that there is no gap. The method for reinforcing a steel structure according to claim 1, wherein the FRP sheet uses reinforcing fibers arranged in two directions. Adhesion of the FRP sheet is performed by applying an impregnation adhesive on the surface of the concrete and the formwork, and by overlapping the sheet of reinforcing fiber and applying the impregnation adhesive thereon, before it solidifies. A method for reinforcing a steel structure according to claim 1 or 2 . As the reinforcing fiber of the FRP sheet, carbon fiber, metal fiber, alone glass fibers or organic fibers, or to any of claims 1 to 3, characterized in that plural kinds using contaminating those arranged A method for reinforcing steel structures as described. The above-mentioned formwork before filling with concrete is held at a position spaced from each part of the surface of the rod-like member by an attachment member attached to the outside of the rod-like member . 4. A method for reinforcing a steel structure according to any one of 4 above. The outside of the rod-shaped member in the steel structure is wrapped with concrete, and the outside has a quadrilateral cross section, and the upper part corresponding to one side is an opening as the above-mentioned concrete filling and observation path. Surrounded by a cylindrical formwork made of steel plate having a letter-shaped cross section, the surface of the concrete in the opening and the formwork surface of the opening edge are covered without gaps by an FRP sheet bonded to close the opening. Reinforced structure of steel structure characterized by

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