JPH09228657A - Seismic retrofitting method for RC members - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the tenacity of an RC member by lining the RC member with a steel plate, to which a slit or a slitty notch is formed in the rectangular direction to an axis in the RC member. SOLUTION: Horizontal slits 7 are formed onto one surface of rectangular sectional-shaped flat steel by hot rolling, and a steel plate 2 is manufactured. An existing RC member 1 is lined with the steel plate 2, in which projections 6 in the horizontal direction are molded integrally on the inside in a rib shape and the horizontal slits 7 are formed among the projections 6, and a section between the RC member 1 and the steel plate 2 is filled with fillers 3. The horizontal slits 7 may also be replaced with slitty notches in the horizontal direction. Accordingly, the length of plasticization in the axial direction of the existing RC member can be increased, and the tenacity of the member can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seismic retrofitting method for improving the deformation performance of RC (reinforced concrete) members designed by old seismic standards under earthquake.

[0002]

2. Description of the Related Art In general, structural members whose cross-sectional design is determined mainly by seismic load, such as bridge piers, do not impair serviceability for small and medium earthquakes and do not collapse for large earthquakes. Such a design is performed.

Especially for the latter seismic load, the failure mode of the structural member is important, and in many cases, the bending failure mode and the shear mode are the targets of study. That is, for bending failure of a member, the member is provided with sufficient rigidity (deformability or toughness) so that seismic energy acting on the structure can be absorbed, and for shear failure, the member's rigidity is reduced. Since it can hardly be expected, the member is designed to give sufficient shear strength. And in general,
The member is designed so that bending failure precedes shearing failure.

A design-effective and basic method for the two failure modes is to increase the amount of transverse reinforcement such as stirrup or stirrup.

However, in RC structures designed based on the old seismic standard, large seismic loads during large earthquakes, which are considered in the current seismic standard, were not taken into consideration. Also, the shear fracture type member was not always sufficient in load bearing capacity.
Therefore, there are many structural members that may collapse during a large earthquake.

[0006] By the way, the seismic retrofitting methods for existing RC members are broadly classified. RC winding method for adding lateral reinforcing bars to RC members to increase concrete thickness, and steel plates as a substitute for lateral reinforcing bars. There is a steel plate winding method that winds around the cross section, and a new material winding method that sticks new materials such as carbon fiber around the cross section.

[0007] If there is no room in the building limit for road traffic under the bridge that is subject to seismic reinforcement, it is difficult to adopt the RC winding method which requires a work space for arrangement of bar and formwork. In such a case, the steel plate winding method, which is less expensive than the new material winding method, is often used.

FIG. 10 shows an outline of the steel plate winding method. In the figure, 1 is an existing RC (reinforcing bar concrete) member, 2 is a steel plate, and in this steel plate winding method, a method of filling resin between the existing RC member 1 and the steel plate 2 as a filler 3 and cement. There are two types of methods of filling milk or cement mortar. 4 is a welded seam.

[0009]

Among the steel plate winding methods, a method of filling a resin and a method of filling a cement-based filler, particularly an uneven surface provided inside to improve the adhesion strength with the filler 3. The construction method using the steel plate 2 having the following has the following problems.

That is, in general, a reinforcing bar has a so-called strain hardening region in which the stress level increases as the strain increases after it yields. Therefore, in a sufficiently transversely reinforced original RC member, as shown in FIG. In addition, the axial reinforcing bar 5 is plasticized in a certain section in the axial direction of the member from the fixed end of the member or the member joint. If the region to be plasticized, that is, the volume of the rebar to be plasticized is large, the energy absorption capacity is also large, so that the member has a large stickiness.

The steel sheet winding method for RC members having a small amount of lateral reinforcing bars suppresses the expansion of the width of so-called shear cracks which occur diagonally due to the large deformation of the members,
It has the effect of suppressing the squeezing out and peeling-off of concrete inside the transverse reinforcing bars and the buckling of axial reinforcing bars.

A steel plate 2 having unevenness on the inside even when a resin or a cement-based material is filled as a filler 3 having an effect of integrating the steel plate 2 and member concrete.
The use of is increased in rigidity in the direction perpendicular to the member axis of the steel plate 2 as a result of the cooperative action with concrete.
It is more effective in improving the above functions.

On the other hand, on the other hand, in the inner reinforced region which is separated from the end portion of the steel plate 2 by a certain length in the axial direction of the member, a certain degree of integration with the concrete member is ensured in the axial direction of the member. It is equivalent to the seismic reinforcement in the axial direction. Therefore, the area where the axial reinforcing bars 5 in the existing RC member 1 in the reinforced area are not plasticized or plasticized is significantly reduced as shown in FIG. This is the same when the steel plate 2 whose reinforcing region is regarded as a synthetic member is focused.

As a result, the stickiness of the member is not necessarily as large as expected. In addition, since the cross-sectional proof strength near the joints such as the column base increases, the footing may break first against the intention of the design, and other parts may be brittle in statically indeterminate structures such as rigid frame viaducts. May cause sexual destruction.

The object of the present invention is to eliminate the disadvantages of the above-mentioned conventional example and to increase the plasticizing length of the axial reinforcing bar of the RC member, so that the stickiness of the member is remarkably improved as compared with the prior art. An object of the present invention is to provide a seismic strengthening method for RC members.

[0016]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a steel plate winding method in which resin is filled and a cement-based filler is used in a steel plate having unevenness on the inside. In the method of expecting adhesion by using, firstly, using a steel plate provided with a slit or a slit-shaped notch in the direction perpendicular to the axis of the RC member in advance, and winding the RC member with this steel plate, 2 uses a steel plate in which a plurality of headband-shaped strips are joined to a thin steel plate at regular intervals in the direction perpendicular to the axis of the RC member, and the RC member is wound up with this steel plate; The gist of the present invention is to use a steel plate whose shape changes in a wave shape in the axial direction and to wind up the RC member with this steel plate.

According to the first aspect of the present invention, the slits or notches provided in the steel plate resist the lateral force in the RC member in the same manner as in the case of the reinforcing bar or stirrup, and the axial direction of the member. It does not resist at all, or does not resist when the pulling force exceeds a certain level. as a result,
The plasticizing region of the axial reinforcing bars in the existing RC member is improved as shown in FIG. 9 as compared with the case of FIG. 12 using a steel plate without these slits and the like.

According to the second aspect of the present invention, the thin steel plate functions as a slit, and the same effect as in the first aspect can be obtained.

According to the present invention as set forth in claim 3, a steel plate having a corrugated shape (corrugated steel plate) also resists a lateral force of a member but a force in the axial direction of the member. Since there is almost no resistance to this, the same effects as those of claims 1 and 2 can be obtained.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a first embodiment of an RC member earthquake-proof reinforcement method of the present invention. Among the steel plate winding method, a resin filling method and a cement-based filler filling method have unevenness on the inside. This is in a construction method in which adhesion is expected by using a steel sheet having

A steel plate 2 is wound around an existing RC (reinforcing rod concrete) member 1 and a filler 3 of resin, cement milk or cement mortar is filled between the existing RC member 1 and the steel plate 2, and the steel plate 2 is used as an inner side. The horizontal projections 6 were integrally formed into ribs at appropriate intervals, and the horizontal slits 7 were provided between the projections 6. The horizontal slit 7 is a slit extending in a direction perpendicular to the axis of the existing RC member 1 with respect to the steel plate 2 used. This horizontal slit 7 may be replaced with a horizontal slit-shaped notch.

Does this horizontal slit 7 or notch resist the lateral force in the existing RC member 1 as in the case of the reinforcing bar or stirrup, and does not resist the axial force of the member at all. , It is provided intentionally so as not to resist when the tensile force exceeds a certain level.

Steel plate 2 having such horizontal slits 7
The manufacturing method of is described below. As a method for manufacturing a steel sheet having a plurality of protrusions and grooves extending parallel to the longitudinal direction on one surface of a flat steel plate having a rectangular cross section, a method of manufacturing by hot rolling, a plurality of protrusions by hot rolling only There is a method of forming a groove in a steel sheet provided with a groove by machining, but the manufacturing by hot rolling is cheaper than the machining.

When manufacturing by hot rolling, it is often difficult to integrally form the projection 6 and the groove as the horizontal slit 7 on one surface of the flat steel having a rectangular cross section. First, in the rough rolling stage, one groove of flat steel is roll-formed, and in the final finish rolling step, a projection is formed to manufacture a steel sheet provided with the projection and the groove.

An example of this manufacturing method will be described with reference to FIGS. The rolling rolls used in the initial rolling stage are
As shown in FIGS. 5 and 6, the upper rolling roll 8 is provided with a projection 8a for forming a groove in the steel slab 10, and the upper rolling roll 8 forms an initial rolled steel slab having a groove. To do. In the figure, 9 is a lower rolling roll.

At the final rolling stage, that is, the finishing stage, as shown in FIG. 7 and FIG.
10 is provided with a groove for forming a projection, whereby the horizontal projection 6 and the horizontal slit 7 as a groove are formed.
A steel plate 2 having

When manufacturing a steel sheet in which only a plurality of grooves extending in parallel to the longitudinal direction are provided on one surface of flat steel having a rectangular cross section, in the final rolling step of the final manufacturing step in the above manufacturing process. A steel sheet having only grooves is obtained by using the rolling roll used without grooves.

FIG. 2 shows a second embodiment of the present invention, in which the steel plate 2 has a horizontal slit 7 which also has projections 11 in both horizontal and vertical directions.

FIG. 3 shows a third embodiment of the present invention. As the steel plate 2, a thin steel plate 12 is joined to a belt-shaped strip plate 13 at a constant interval in the direction perpendicular to the axis of the existing RC member 1. Use one. A normal steel plate and a strip plate are used for the thin steel plate 12 and the strip plate 13, and the steel plate and the strip plate are integrated to some extent by welding or the like.

When such a steel plate 2 is used, a thin steel plate
12 plays a role of the slit in the first and second embodiments.

FIG. 4 shows a fourth embodiment of the present invention. As the steel plate 2, a so-called corrugated steel plate whose shape changes in a wavy shape in the axial direction of the existing RC member 1 is used.

Similarly, the steel plate 2 made of this corrugated steel plate has a function of resisting the lateral force of the existing RC member 1 but hardly resisting the axial force of the member. .

[0033]

As described above, the seismic retrofitting method for RC members according to the present invention is an existing RC method in which a steel sheet is wound around a section as a substitute for lateral reinforcing bars.
Since the plasticizing length of the axial rebar of the member can be made larger, the stickiness of the member can be remarkably improved as compared with the prior art.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of a seismic strengthening method for RC members according to the present invention.

FIG. 2 is a perspective view showing a second embodiment of an RC member seismic reinforcement method of the present invention.

FIG. 3 is a perspective view showing a third embodiment of the seismic strengthening method for RC members of the present invention.

FIG. 4 is a perspective view showing a fourth embodiment of an RC member seismic reinforcement method of the present invention.

FIG. 5 is a vertical sectional side view showing a front stage of a manufacturing process of a steel sheet.

FIG. 6 is a vertical cross-sectional front view showing the previous stage of the manufacturing process of the steel sheet.

FIG. 7 is a vertical cross-sectional side view showing the latter stage of the manufacturing process of the steel sheet.

FIG. 8 is a vertical sectional front view showing the latter stage of the manufacturing process of the steel sheet.

FIG. 9 is an explanatory diagram showing yield strength as a result of reinforcement of the RC member according to the present invention by the earthquake-proof reinforcement method.

FIG. 10 is a perspective view showing a conventional example.

FIG. 11 is an explanatory diagram showing the yield strength when the steel sheet is not wound up.

FIG. 12 is an explanatory diagram showing the yield strength of a conventional example in which a steel plate is wound up.

[Explanation of symbols]

1 ... Existing RC member 2 ... Steel plate 3 ... Filler 4 ... Weld seam 5 ... Reinforcing bar 6 ... Horizontal projection 7 ... Horizontal slit 8 ... Rolling upper roll 8a, 8b ... Projection 9 ... Rolling lower roll 10 ... Steel strip 11 ... Horizontal, Vertical protrusions 12… Thin steel plate 13… Strip plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kosuke Furuichi 6-3-2 Toyo, Koto-ku, Tokyo Kashima Construction Co., Ltd. Kanto Branch (72) Inventor Reiko Amano 2-1-1, Tobita, Chofu-shi, Tokyo No. Kashima Construction Co., Ltd. Technical Research Institute (72) Inventor Hiroya Okubo 2-32 Uchisaiwaicho, Chiyoda-ku, Tokyo Inside Kawasaki Steel Works (72) Inventor Shuhashi 2-3 2-3 Uchisaiwaicho, Chiyoda-ku, Tokyo Kawasaki Steel Works (72) Inventor Kento Okumura 2-3-2 Uchisaiwaicho, Chiyoda-ku, Tokyo Inside Kawasaki Steel Works

Claims (3)

[Claims] 1. A seismic strengthening method for RC members, characterized in that a steel plate having slits or slit-shaped notches provided in the direction perpendicular to the axis of the RC member is used in advance and the RC member is wound up with this steel plate. 2. An RC member characterized in that a thin steel plate is joined to a plurality of headband-shaped strips at regular intervals in a direction perpendicular to the axis of the RC member, and the RC member is wound up with this steel plate. Seismic strengthening method for members. 3. A seismic strengthening method for an RC member, characterized in that a steel plate whose shape is corrugated in the axial direction of the RC member is used and the RC member is wound up with this steel plate.