JP2002081019A - Method for repairing or expanding reinforced concrete structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for repairing or expanding a reinforced concrete structure capable of reducing the period of construction work and suppressing noises by making as small as possible the amount of work for shaving concrete portions, in a construction method which includes partially cutting an existing reinforced concrete structure and constructing a new reinforced concrete portion at the cut portion. SOLUTION: The method comprises a cutting process for cutting at the same time existing reinforcement 3 and concrete 2 which constitute a portion of the reinforced concrete structure; a stud welding process for stud welding and extending the end of new reinforcement 4 to the end face of the existing reinforcement exposed to a cut plane 7 of concrete, in such a way that they are approximately coplanar with each other, with the new reinforcement being equal in diameter to the existing reinforcement; and a concrete placement process for placing concrete.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of repairing and expanding a reinforced concrete structure, and more particularly to a method of replacing an expansion device disposed at a connection portion between concrete floor slabs of a bridge or expanding a width of a floor slab. The present invention relates to a method for repairing and expanding a reinforced concrete structure applicable to a building.

[0002]

2. Description of the Related Art In recent years, accidents involving reinforced concrete viaducts and tunnel collapses of shinkansen have frequently occurred, and this has become a major social problem. Regardless of the cause, 1
Reinforced concrete structures, which have rapidly increased since the high growth period of the 960s to 1970s, have become obsolete due to the increase in vehicle exhaust gas, acid rain, and traffic volume. The life of a reinforced concrete structure is said to be more than 50 years, but due to the deterioration of the environment surrounding the reinforced concrete structure, many structures built during the high growth period are approaching the life. However, by performing appropriate maintenance and repair at the appropriate time, the life of the reinforced concrete structure can be significantly extended.

For example, in a reinforced concrete bridge, as represented by a hollow slab bridge, concrete slabs are connected to each other via a telescopic device at a pier portion. As shown in FIG.
01, the steel members 102A, 102B of the telescopic device 102 are integrated with the ends of the concrete floor slabs 100, 101, respectively.
Both steel members 102A and 102B are set in a state where the comb-shaped claw portions are engaged with each other. The expansion and contraction device 102 provided at the ends of the concrete slabs 100 and 101 is the most damaged portion, and needs to be replaced.

[0004] The replacement of the telescopic device 102 is performed first by the concrete section 10 of the concrete slabs 100 and 101.
3 is cut with a rotary cutter or a wire sawing device together with the internal reinforcing bar 104, and then the cut ends of the concrete slabs 100, 101 and the steel members 102A, 102
After removing B, the cut surface of the concrete portion 103 was cut over the entire surface by a rock drill to a thickness of about 10 to 15 cm to expose the end of the reinforcing bar 104, and a new steel member 102A was installed. After that, the new reinforcing bar 105 is extended by flare welding in a state where the new reinforcing bar 105 is overlapped by about 10 cm on the exposed portion of the reinforcing bar 104, the other reinforcing bars are arranged, and finally concrete is cast.

[0005] Here, the most problematic operation is the operation of cutting concrete parts. Typically, this type of telescopic device 10
The replacement work is an intensive work to minimize traffic regulations, so the cutting work may be performed at midnight, and the noise generated may cause a great deal of trouble to local residents. Also, if the noise is severe, the construction itself may be interrupted by complaints from the local residents or the use of skills.

On the other hand, there are sections in which chronic traffic congestion occurs due to an increase in traffic volume, such as the Tomei Expressway, the Meishin Expressway, or the Metropolitan Expressway. Lane widening is being carried out in various places. This lane widening work will be briefly described with reference to FIG. 13, but is common to the above-described expansion and contraction device replacement work. Existing concrete slab 2 shown in FIG.
When extending the end of the concrete part 201,
Is cut along with the internal reinforcing bar 202 along the cutting line L1 shown in FIG. 13B (see FIG. 13C). Then, a cutting line L having a thickness of 10 to 15 cm is cut from the cut surface 203.
2 (see FIG. 13 (d)), the concrete portion 201 is shaved with a rock drill or a water jet to expose the tip of the reinforcing bar 202 (see FIG. 13 (e)). And the existing rebar 2
The newly installed reinforcing bar 204 is connected to the end of No. 02 by enclosure welding or a mechanical joint in a state of being overlapped by about 10 cm, and finally concrete 205 is cast (see FIG. 13 (f)). In the figure, reference numeral 206 indicates the overlap of reinforcing bars.
Also in this case, the work of shaving the concrete portion of the thickness shown in FIG. 13D is the biggest problem of prolonging the construction period and generating noise.

Here, as a technique for coaxially welding rebars of the same diameter, there is the above-mentioned enclose welding. However, since the welding time is long, the working efficiency is deteriorated. The large size causes a change in the material of the rebar, and furthermore, it is necessary to basically grind the concrete part to secure a welding margin of a predetermined length. In addition, although the technique of stud welding a reinforcing bar to the surface of a steel sheet is common, stud welding is conventionally recommended to be welded to an iron sheet having an area of 15 cm square or more, and common sense due to magnetic blowing phenomenon. Was also applied in such cases.

[0008]

SUMMARY OF THE INVENTION In view of the above situation, the present invention is directed to a method of partially cutting an existing reinforced concrete structure and constructing a new reinforced concrete portion at the cut portion. It is an object of the present invention to provide a method for repairing and expanding a reinforced concrete structure capable of shortening the construction period and reducing noise generation by minimizing the shaving work of a concrete part.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a cutting step for simultaneously cutting an existing reinforcing bar and concrete, which is a part of a reinforced concrete structure, and an existing reinforcing bar exposed to a concrete cut surface. A repair / expansion method for a reinforced concrete structure was established, which consisted of a stud welding process in which the end of a new reinforcing bar of the same diameter was extended almost coaxially on the end face and a concrete placing process in which concrete was cast.

[0010] More preferably, after the cutting step, the cut surface of the reinforced concrete structure has a thickness of 1 to 1 over the entire surface.
Including a coarsening step of removing the ends of the existing reinforcing bars by removing the roughening state by 3 cm, or after the cutting step, the cutting surface of the reinforced concrete structure, and only the periphery of the existing reinforcing bars. This is a method that includes a shaving step of partially shaving to expose the end of the existing rebar.

Further, before the stud welding step, a backing plate made of a conductor having a center hole at the center at the end of the existing reinforcing bar exposed to the cut surface and serving also as a ground terminal and a ferrule contact surface. This method includes a backing plate attaching step of fixing the contact surface so that the contact surface is substantially orthogonal to the newly installed reinforcing bar.

Before the stud welding step, an earth clamp made of a conductor which also serves as an earth terminal and a ferrule contact surface is attached to the end of the existing reinforcing bar exposed on the cut surface.
It is more practical to include a ground connection step of detachably mounting the contact surface so as to be substantially orthogonal to the new reinforcing bar,
Stud welding can be performed without using a backing plate. In this case, a heat insulating and insulating protection ring is attached to the ferrule contact surface of the earth clamp around the end of the existing reinforcing bar, and the ferrule is pressed against the protection ring. The new steel is stud welded.

[0013] The reinforced concrete structure is a concrete slab of a bridge, and the method of the present invention is provided for a replacement work of a telescopic device arranged at a connection portion between the slabs,
Alternatively, when the floor slab is subjected to a width expansion work, the effect is extremely large.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 shows the basic steps of the repair / expansion method of a reinforced concrete structure according to the present invention,
In the figure, reference numeral 1 denotes an existing reinforced concrete structure, 2 denotes an existing concrete portion, 3 denotes an existing reinforcing bar, 4 denotes a new reinforcing bar, 5 denotes an auxiliary reinforcing bar, and 6 denotes a new concrete portion.

First, the existing reinforced concrete structure 1
As shown in FIG. 1 (a), the existing rebar 3 is arranged vertically and horizontally inside the existing concrete part 2. For example, in the case of a steel bridge A as shown in FIG. 2, a steel girder 10,... Is installed between piers (not shown), and a concrete floor slab 11 is constructed on the steel girder 10,. . In the concrete floor slab 11, the distribution reinforcing bars 13,... Are disposed in the concrete portion 12 in the upper and lower portions in the bridge axis direction, and the main reinforcing bars 14,. It has a structure. Usually, the number of upper main reinforcing bars 14 is set to twice the number of lower main reinforcing bars 14.
In the replacement work of the expansion and contraction device described later, the newly installed reinforcing bar is connected to the reinforcing bar 13, and the main reinforcing bar 14 is used in the lane widening work.
It is necessary to connect a new main reinforcing bar to

The basic process in the present embodiment is a cutting process (FIG. 1 (a)) for simultaneously cutting the existing reinforcing bar 3 and the existing concrete portion 2 along a cutting line L1 which is a part of the existing reinforced concrete structure 1. b)), and the cut surface 7 of the existing reinforced concrete structure 1 has a thickness of 1 to 3 over the entire surface.
1 cm (up to the coarse line L 2) in a coarse state to expose the end of the existing reinforcing bar 3 (FIG. 1C,
(Refer to (d)), and a backing plate 8 having a center hole through which a reinforcing bar is inserted at the center at the end of the existing reinforcing bar 3 exposed on the cut surface 7 and serving also as a ground terminal and a ferrule contact surface. A backing plate mounting step of fixing the contact surface so as to be substantially orthogonal to the new reinforcing bar 4 (see FIG. 1E), and a new reinforcing bar having the same diameter as the end surface of the existing reinforcing bar 3 exposed on the roughened concrete surface 9. A stud welding step (see FIG. 1 (e)) for extending the ends of the steel bars 4 substantially in a coaxial manner by stud welding (see FIG. 1 (e)), and further welding and connecting the auxiliary reinforcing bars 5 to the newly installed reinforcing bars 4; It consists of a reinforcing arrangement step and a concrete placing step of placing concrete (see FIG. 1 (f)). As a result, the new reinforcing bar 4 and the auxiliary reinforcing bar 5 are provided inside the new concrete section 6 at a part where the existing reinforced concrete structure 1 is partially removed.
Can be rebuilt or newly constructed.

Instead of the coarsening step, only the periphery of the existing reinforcing bar 3 on the cut surface 7 of the reinforced concrete structure 1 is partially cut to expose the end of the existing reinforcing bar 3. It is good also as a shaving process of the degree to be made. in this case,
Since the existing concrete part 2 is only partially removed, the working time is further shortened, and the generation of noise is further reduced.

Further, the roughening step and the shaving step are omitted, and only the end face of the existing reinforcing bar 3 is exposed on the cut surface 7 of the existing concrete portion 3. Can be stud welded. Also in this case, a part of the backing plate 8 made of a conductor is placed along the cut surface 7 so that the magnetic blowing phenomenon at the time of stud welding is suppressed and a good welding can be performed. It is preferable to weld around the end face of the existing reinforcing bar 3 to be electrically connected and fixed. Further, it is desirable that only the surface layer of the heat-affected concrete portion 3 is roughened.

Next, a case where the method of the present invention is applied to the replacement work of the expansion and contraction device 20 provided at the connection portion of the concrete floor slab will be described with reference to FIG. First, as shown in FIG. 3A, the end of the concrete portion 12 of the concrete slab 11 is cut with a rotating cutter or a wire sawing device together with the internal distribution reinforcing bars 13,. The end and one of the existing steel members 21 constituting the telescopic device 20 are removed. Incidentally, reference numeral 15 in FIG.
Is an asphalt layer paved on the upper surface of the concrete part 12. After that, as shown in FIG. 3 (b), the cut surface 22 of the concrete portion 12 is roughened with a rock drill to a thickness of 1 to 3 cm over the entire surface, and the end of the distribution reinforcing bar 13 is exposed. , A new steel member 23 is installed. Then, a backing plate 24 is welded to an end of each of the distribution bars 13 to be electrically conductive and fixed. Then, as shown in FIGS. 3 (c) and 3 (d), a stud is attached to the end of each of the power distribution rebars 13 while pressing a ferrule 26 against the backing plate 24 with a newly installed L-shaped power distribution rebar 25. Weld. In addition, the ends of the power distribution rebars 25, 25 located above and below are overlapped and bound by a binding wire to form a U-shaped rebar in side view. Then, FIG. 3 (e),
As shown in (f), the auxiliary reinforcing bar 28 is screwed into the nuts 27 fixed to the side surfaces of the new steel member 23 by stud welding, and the other auxiliary reinforcing bars 29
Assemble Finally, if necessary, formwork is constructed and jet concrete is poured, and after hardening, traffic is released to complete the work.

FIG. 4 shows details of the stud welding of the new distribution reinforcing bar 25 to the end of the existing distribution reinforcing bar 13. In the present embodiment, the backing plate 24 has a thickness of 5 mm,
cm steel having a central hole 30 at the center for inserting the distribution reinforcing bar 13, and also serving as a ground terminal and a ferrule contact surface 31. The center hole 3 of this backing plate 24
The power distribution rebar 13 is inserted into the power distribution rebar 0, and two-point welding is easily performed with the ferrule contact surface substantially flush with the end face of the power distribution rebar 13. Then, at the end of the new distribution reinforcing bar 25, only the crest of the deformed reinforcing bar is cut off, the ferrule 26 is inserted there, and the stud gun (not shown) is set. Here, FIG.
(B) As shown in (c), the diagonal portion of the backing plate 24 is clamped by a holding tool 32 in order to ground the existing distribution bar 13.
It is sandwiched between. The holding member 32 is newly developed to carry out the present invention, and it is assumed that the tip portion is bent when the gap between the concrete portion 12 and the roughened surface is small.

The stud welding method itself is well known. First, the distal end of the new distribution reinforcing bar 25 is brought into contact with the end face of the existing distribution reinforcing bar 13, and the new distribution is performed while a large current is applied to both distribution reinforcing bars 13, 25. The force reinforcement 25 is slightly retracted to maintain the arc discharge between the two reinforcements, and immediately after the end of the reinforcement is melted, the new distribution reinforcement 25 is advanced and the existing distribution reinforcement 13 is advanced.
Welded to the end of the. Here, the ferrule 2
6 has an escape hole 33 for gas generated at the time of welding and a space 34 for confining the molten rebar. By using the backing plate 24, a conductor surface having a sufficient area is formed around the welding surface, thereby alleviating the magnetic blowing phenomenon at the time of stud welding, and newly installing the same diameter as the existing distribution reinforcing bar 13. It is possible to satisfactorily weld the distribution steel bars 25 coaxially.
Further, since the length of one side of the backing plate 24 is the same as or slightly larger than the diameter of the ferrule 26, the positioning of the ferrule 26 during stud welding is facilitated, and the centering of the reinforcing steel is thereby reduced. It will be accurate.
Further, it is also preferable to provide a structure for positioning the ferrule 26 on the backing plate 24, for example, an uneven fitting portion.

In the present embodiment, the backing plate 24 has a square shape, but may have a circular shape and a thickness of about 2 to 3 mm. Further, the backing plate 24
May or may not be in contact with the concrete portion 12, and if so, the roughened or cut surface of the concrete portion 12 needs to be dry.

FIG. 5 shows that the size of the backing plate 24 is minimized and at least two terminal portions 3 are provided around the backing plate 24.
5, 35 are protruded laterally, and the terminal portions 35, 35 are sandwiched by a holding member 32 to be grounded. Further, after the stud welding, the backing plate 24 becomes unnecessary and is left inside the new concrete part. Therefore, the V-shaped groove 36 provided at the base of the terminal part 35 is used so as not to affect the concrete strength. It is broken and removed. It should be noted that the backing plate 24 may be left as it is if there is no problem in strength even if it is left inside the new concrete part. Further, instead of the holding tool 32, the backing plate 24 is used.
A grounding device having a socket structure that can be detachably connected to the backing plate 24 may be used. In this case, a structure in which the peripheral portion of the backing plate 24 is gripped from the side, or a cylindrical member concentrically arranged outside the ferrule 26 Thus, a structure or the like that grips the peripheral edge of the backing plate 24 from the axial direction is conceivable.

FIG. 6 shows a case where the end of the concrete floor slab 11 is actually cut along the cutting line L1.
Indicates that there are some that are cut at a right angle to the longitudinal direction and some that are cut diagonally. Therefore, in order to realize the method of the present invention, it is necessary that the new reinforcing bar 25 can be stud-welded not only to the right-angled cut end surface of the existing reinforcing bar 13 but also to the obliquely cut end surface at right angles to the end surface. FIG.
Indicates that stud welding is possible in each case. FIG. 7A shows the concrete portion 12.
7B shows a case where the longitudinal direction of the existing reinforcing bar 13 is perpendicular to the cut surface 22 of FIG. 7 and only the periphery of the existing reinforcing bar 13 is partially cut off the cut surface 22. FIG. 3 shows a case where the roughening treatment is not performed before the stud welding. FIG. 7C shows a case where the longitudinal direction of the existing reinforcing bar 13 is inclined with respect to the cutting surface 22 of the concrete portion 12 and only the cutting surface 22 around the existing reinforcing bar 13 is partially shaved. FIG. 7D shows a case where the shaving process in the case of FIG. 7C is not performed before the stud welding. However, finally, in order to improve the adhesion to the newly-installed concrete part, it is necessary to roughen and treat the entire cut surface 22.
In the drawing, reference numeral 37 denotes a concave portion formed by a partial shaving process. When the shaving process is performed (see FIGS. 7A and 7C), the backing plate 24 is placed in the concave portion 37. Will be located. When the coarsening process is performed later (FIG. 7B)
(See (d)), the backing plate 24 is connected to the concrete portion 12.
Is welded to the end face of the existing reinforcing bar 13 at the inner hole edge of the center hole 30 and fixed. In addition, the center hole 30 of the backing plate 24 is formed by the existing reinforcing bar 13 having the cut surface 22.
If it is inclined with respect to, it must be formed obliquely in accordance with the inclination angle. This is to reduce the magnetic blowing phenomenon.

In the above-described method using the backing plate 24,
The purpose of using the backing plate 24 is to reduce the magnetic blowing phenomenon at the time of stud welding by forming a conductor surface having a sufficient area around the welding surface to reduce the magnetic blowing phenomenon. If the same operation as that described above can be realized by another device, it is not necessary to use the backing plate 24. Further, since the backing plate 24 is still fixed to the existing reinforcing bar 13 even after the stud welding, when the concrete is poured, the backing plate 24 is fixed.
It cannot be denied that concrete may not run around to the rear of the car. Therefore, if good stud welding can be performed without using the backing plate 24, the number of steps and the period of work can be further reduced. In the present embodiment, a method not using the backing plate 24 will be described with reference to FIGS.

In this method, before the stud welding step,
An earth clamp 38 made of a conductor that also serves as an earth terminal and a ferrule contact surface is provided on an end of the existing reinforcing bar 3 exposed on the cut surface 7 of the existing concrete portion 2, and the contact surface 39 is substantially orthogonal to the new reinforcing bar 4. It is characterized in that it includes a ground connection step of detachably mounting so as to perform connection. Then, a heat insulating and insulating protection ring 40 is attached to the ferrule contact surface 39 of the earth clamp 38 around the end of the existing reinforcing bar 3, and the ferrule 26 is attached to the protection ring 4.
The newly installed reinforcing bar 4 is stud-welded while being pressed against zero.

More specifically, the earth clamp 38
Is provided so that the bases of a pair of holding arms 41, 41 are pivotably connected to each other, and holding plates 42, 42 for holding the ends of the existing reinforcing bar 3 are provided at the distal ends of the holding arms 41, 41, respectively. A fastening means 43 comprising a bolt and a wing nut is provided at an intermediate portion between the arms 41, 41, and a connection portion 44 for a ground wire (not shown) is provided at an appropriate position. Reference numeral 41A in the figure indicates a pivotal connection between the holding arms 41, 41. Here, the clamping plates 42, 42 are attached to the distal ends of the clamping arms 41, 41 by means of detachable fixing means such as bolting so that they can be replaced in the event of thermal damage during stud welding. . A semicircular engaging recess 4 for receiving an end of the existing reinforcing bar 3 is provided on both joining surfaces.
4 and the clamping means 43 are used to hold the holding arms 41, 41.
When the is tightened, the end of the existing reinforcing bar 3 can be held in a press-contact state in both engagement recesses 44, 44. Further, the distal ends of the holding arms 41, 41 are bent in an angle α in a side view, so that the base of the earth clamp 38 is connected to the existing concrete part 2 even when the exposed length of the end of the existing reinforcing bar 3 is short. Is not in contact with the cut surface 7 of the slab. In the present embodiment, the aforementioned angle α is set to 30 degrees.

The holding arms 41, 41 and the holding plates 42, 42 constituting the earth clamp 38 are formed of conductors, and the holding plates 42, 42 are formed on the ferrule contact surface 39 described above.
Is formed, so that it has the area and shape required to alleviate the magnetic blowing phenomenon during stud welding. For example,
In the present embodiment, the holding plate 42 is a plate having a side of 4 to 5 cm and a thickness of about 3 to 5 mm. The dimensions of the engaging recesses 44 are set in accordance with the diameter of the existing reinforcing bars 3. In the case of the existing reinforcing bars 3 having different diameters, the fitting recesses 44 having the engaging recesses 44 corresponding to the diameters can be used. good. The protection ring 40 is provided to protect the sandwiching plates 42 and 42 from high heat at the time of stud welding and to form the space 34 of the ferrule 26. The material of the protection ring 40 is the same as that of the ferrule 26, such as ceramics and the like. It is possible to mold using the heat insulating material. Further, the shape of the protection ring 40 is a circular ring shape in the present embodiment, but the outer shape may be a square shape or another shape. The structure and mechanism of the earth clamp 38 are merely examples, and can be modified.

In the method using the earth clamp 38, first, as described above, the existing concrete portion 2 is cut together with the existing reinforcing bars 3 (existing distribution bars 13), and a roughening process or a partial shaving process is performed. After exposing the end of the existing reinforcing bar 3, the end of the existing reinforcing bar 3 is securely clamped between the sandwiching plates 42, 42 of the earth clamp 38 to be connected to the ground.
Then, after inserting the protection ring 40 into the end of the existing reinforcing bar 3, with the ferrule 26 pressed against the protection ring 40, the new reinforcing bar 4 is coaxially formed with the existing reinforcing bar 3 (the existing distribution bar 13). (Newly-installed distribution bars 25) are extended by stud welding.

An appearance inspection and a tensile test were performed on seven specimens in which the deformed reinforcing bars (D16) were stud-welded coaxially without using the above-mentioned backing plate 24, and the appearance of the welded portions was all good. And a tensile load of 1
The results were that the tensile strength was not less than 00 kN, the tensile strength was not less than 510 N / mm ² , and the breaking position was the shaft.

Next, FIG. 11 shows a state of widening work of the concrete floor slab 11 in the hollow slab bridge B. In the figure, reference numeral 11A indicates an existing concrete slab, and 11B indicates a new concrete slab.
In this widening work, first, the existing concrete floor slab 11A
Is cut along the bridge axis direction, and a new concrete floor slab 11B is constructed on the side by the method of the present invention. More specifically, the existing concrete floor slab 11
A side 11C of A is cut along the cutting line L1, and a new concrete slab 11B is constructed at a position distant from the cut surface, and a space between the existing concrete slab 11A and the new concrete slab 11B is formed. The construction method of the present invention is applied to construct the continuous portion 11D. The details thereof are the same as those described above, and the description is omitted. In addition, it is also possible to directly construct a new concrete floor slab 11B by applying the method of the present invention without providing the connecting portion 11D.

The method of repairing and expanding a reinforced concrete structure according to the present invention is not limited to the above-described work for replacing and expanding the expansion device of the concrete slab, and can be widely applied to general reinforced concrete structures. ,
It is apparent from the description of the present specification and the drawings.

[0033]

The method for repairing and expanding a reinforced concrete structure according to the first aspect of the present invention comprises a cutting step of simultaneously cutting an existing reinforcing bar and concrete, which is a part of a reinforced concrete structure, and a concrete cut surface. It consists of a stud welding process of extending the end of a new reinforcing bar of the same diameter to the existing reinforcing bar end surface or round bar end surface exposed to the shaft by substantially stud welding, and a concrete placing process of placing concrete. Construction work can be shortened and noise generation can be reduced by minimizing the shaving work of the part as much as possible, furthermore, the amount of industrial waste generated is greatly reduced, and the disposal cost can be suppressed, and construction Very effective in the field.

According to the second aspect, the amount of shaving of the concrete portion after cutting can be suppressed to about 1/5 or less as compared with the conventional construction method, and the time of noise generated in the work is extremely short. And the effect of shortening the construction period is great.

According to the third aspect, it is possible to further shorten the construction period and reduce noise generation as compared with the second aspect.

According to the fourth aspect, a new reinforcing bar having the same diameter as the existing reinforcing bar can be stud-welded coaxially to the end of the existing reinforcing bar.

According to the fifth aspect, a new reinforcing bar having the same diameter as that of the existing reinforcing bar can be stud-welded to the end of the existing reinforcing bar coaxially without using a backing plate. It can be shortened.

According to the sixth aspect, thermal damage to the earth clamp can be suppressed, and the earth clamp can be used repeatedly, which can contribute to cost reduction and achieve good stud welding. it can.

According to claims 7 and 8, in addition to the above-mentioned effects, the period of traffic regulation is shortened to reduce the influence on industrial activities using roads. The effect can be reduced.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified explanatory view for explaining a basic step of a construction method of the present invention, and (a) to (f) are cross-sectional views showing states of a reinforced concrete structure in each step.

FIG. 2 is a simplified sectional view orthogonal to a bridge axis direction of a hollow slab bridge.

FIG. 3 is a simplified explanatory view for explaining a replacement work of an extension device to which the method of the present invention is applied, and (a) to (f) are cross-sectional views showing states of a concrete slab in each step.

FIGS. 4A and 4B show details of stud welding; FIG. 4A is a partial cross-sectional view showing a state before a holding tool is attached; FIG. 4B is a side view showing a state where a backing plate is held by the holding tool; (c) is a partial cross-sectional view showing a state after the holding tool is attached.

FIG. 5 is a partial cross-sectional view when a backing plate of another embodiment is used.

FIG. 6 is a simplified sectional view of an end of a concrete floor slab.

FIG. 7A is a partial cross-sectional view when the longitudinal direction of the existing reinforcing bar is perpendicular to the cut surface of the concrete part and only the periphery of the existing reinforcing bar is partially cut off, and FIG. )
(C) is a partial cross-sectional view of the case where the roughing treatment is not performed before the stud welding, in which the longitudinal direction of the existing reinforcing bar is inclined with respect to the cut surface of the concrete portion, and only the periphery of the existing reinforcing bar is partially cut off. (D) is (c)
FIG. 6 shows a partial cross-sectional view in a case where the roughening process in the case of (1) is not performed before stud welding.

FIG. 8 is a side view of an earth clamp for realizing stud welding without using a backing plate according to another embodiment.

FIG. 9 is a partial cross-sectional view showing a state where an earth clamp is attached to an exposed end of an existing reinforcing bar.

FIG. 10 is a partial sectional view showing a set state before deformed reinforcing bars are stud-welded to each other.

FIG. 11 is a simplified explanatory view of widening work of a concrete floor slab.

FIG. 12 is an explanatory cross-sectional view of a conventional extension device replacement work.

FIG. 13 is a simplified explanatory view for explaining basic steps of a conventional method, and (a) to (f) are cross-sectional views showing states of a reinforced concrete structure in each step.

[Explanation of symbols]

 1 Existing Reinforced Concrete Structure 1A New Reinforced Concrete Structure 2 Existing Concrete Part 3 Existing Reinforcement 4 New Reinforcement 5 Auxiliary Reinforcement 6 New Concrete Part 7 Cut Surface 8 Backing Plate 9 Roughened Surface 10 Bridge Girder 11 Concrete Floor Slab 11A Existing Concrete Floor Plate 11B Newly installed concrete slab 11C Existing concrete slab side portion 11D Continuously connected portion 12 Concrete portion 13 Existing distribution reinforcing bar 14 Main reinforcing bar 15 Asphalt layer 20 Telescopic device 21 Existing steel member 22 Cutting surface 23 New steel member 24 Backing plate 25 Newly-installed reinforcing steel bar 26 Ferrule 27 Nut 28 Auxiliary reinforcing bar 29 Auxiliary reinforcing bar 30 Center hole 31 Ferrule contact surface 32 Clamping tool 33 Gas escape hole 34 Space 35 Terminal 36 V-shaped groove 37 Recess 38 Ground clamp 39 Ferrule contact surface 40 Protection Ring 41 clamping arm 41A pivot supports 42 holding plate 43 fastening means 44 engages the recess A steel bridge B Horosurabu bridge L1 cutting lines L2 roughening line

Claims (8)

[Claims] 1. A cutting step of simultaneously cutting an existing reinforcing bar and concrete, which is a part of a reinforced concrete structure,
It is characterized by a stud welding process of extending the end of a new reinforcing bar of the same diameter to the end face of the existing reinforcing bar exposed on the concrete cut surface by substantially stud welding, and a concrete placing process of placing concrete. Repair and expansion of reinforced concrete structures. 2. The method according to claim 1, further comprising: after the cutting step, removing a cut surface of the reinforced concrete structure in a coarse state by a thickness of 1 to 3 cm over the entire surface to expose an end of the existing reinforcing bar. A method for repairing and expanding a reinforced concrete structure according to claim 1. 3. The method according to claim 1, further comprising, after the cutting step, a shaving step of partially shaving only the periphery of the existing reinforcing bar on a cut surface of the reinforced concrete structure to expose an end of the existing reinforcing bar. Item 6. The method for repairing and expanding a reinforced concrete structure according to Item 1. 4. Before the stud welding step, the end of the existing reinforcing bar exposed to the cut surface has a center hole at the center,
The backing plate mounting step of fixing a backing plate made of a conductor also serving as a ground terminal and a ferrule contacting surface so that the contacting surface is substantially orthogonal to the newly installed reinforcing bar. Repair and expansion of reinforced concrete structures. 5. An earth clamp made of a conductor which also serves as an earth terminal and a ferrule abutting surface, and an abutting surface of a new reinforcing bar is attached to an end of the existing reinforcing bar exposed to the cut surface before the stud welding step. The method for repairing and expanding a reinforced concrete structure according to any one of claims 1 to 3, further comprising a ground connection step of detachably attaching the reinforced concrete structure so as to be substantially orthogonal to the above. 6. A protection ring having heat insulation and insulation properties is attached to the ferrule contact surface of the earth clamp around the end of the existing reinforcing bar, and the ferrule is newly installed with the ferrule pressed against the protection ring. The repair / expansion method for a reinforced concrete structure according to claim 5, wherein the reinforcement is stud-welded. 7. The reinforced concrete structure according to claim 1, wherein the reinforced concrete structure is a concrete slab of a bridge, and the reinforced concrete structure is used for a replacement work of an extension device arranged at a connection portion between the slabs. Repair and expansion method. 8. The repair / expansion method for a reinforced concrete structure according to claim 1, wherein the reinforced concrete structure is a concrete slab of a bridge, and the slab is subjected to a width expansion work of the slab.