JP2016069883A - Bent reinforcing bar with bearing pressure plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bent reinforcing bar with a bearing pressure plate fitted at the bent part of the reinforcing bar, and a reinforced concrete structure having the bent reinforcing bar with a bearing pressure plate embedded in the concrete.SOLUTION: A reinforcing bar is bent at any location, and a bearing pressure plate is fitted at the bent part. A bent reinforcing bar 1 with a bearing pressure plate secures a pressure bearing area with a bearing pressure plate 8, such that a bearing stress intensity in a radial direction at a bent part 6 of the reinforcing bar that accompanies tensile force exerted on the reinforcing bar is less than an allowable bearing stress intensity of concrete. Therefore, bearing failure is prevented for the concrete even if yielding tensile force is exerted on the bent part 6 of the reinforcing bar that is not mitigated by adhesion resistance at a linear part of the reinforcing bar.SELECTED DRAWING: Figure 6

Description

    The present invention relates to a reinforced concrete structure in which a support plate is attached to a bent portion of a reinforcing bar and a reinforced concrete structure in which the bent reinforcing bar with a support plate is fixed in concrete.

When fixing reinforcing bars to concrete, the straight line fixing length from the point where fixing of reinforcing bars starts (hereinafter referred to as the fixing start point) to the starting point of bending of reinforcing bars is the building construction standard specification / explanation JASS5 reinforced concrete construction (hereinafter referred to as JASS5) ) Is defined as about 20d to 35. The reason for this is that when a tensile force is applied to the reinforcing bar at the bent portion, radial support pressure is generated on the inner concrete of the bent portion.
This supporting pressure is proportional to the magnitude of the tensile force at the point where bending starts.
Therefore, in order to prevent the destruction of the concrete at such a bent portion, it is preferable that the bending fixing of the reinforcing bar secures a linear fixing length of about 20d to 35 for reducing the reinforcing bar tensile force at the point of starting the bending. It is said that.
In recent years, the strength required for pile head joints has become extremely large, and at the site where pile head reinforcing bars are densely arranged, the origin of fixing is the fixing start point in the bending fixing that secures the straight fixing length specified in JASS5 etc. That is, it often interferes with the base bars, the column base anchor bolts, and the main bars of the foundation beam arranged immediately above the upper end of the pile.
Therefore, in many sites, without securing the predetermined straight line defined in JASS5, etc., construction is done such as bending the pile head reinforcement bars directly above the piles to dodge the base bars and foundation beam main bars that interfere. ing.

Building Construction Standard Specification / Explanation JASS5 Reinforced Concrete Work 2009 Edition (10.9 Position and Fixation of Reinforcing Bar Joint P323-324) Copyright The Architectural Institute of Japan

However, when a conventional bent part with a narrow reinforcing bar width is subjected to a tensile force at the time of yielding of the reinforcing bar that does not decrease due to the adhesion resistance of the straight line part, the radial bearing stress level generated in the concrete is reduced to the allowable load of the concrete. Since the bearing area cannot be secured so as to be equal to or less than the degree of pressure stress, there is a risk of bearing failure in concrete.
The reason for this will be explained. In order to prevent concrete bearing failure, the bearing stress level obtained by dividing the bearing pressure generated on the concrete surface by the bearing area (= bearing width x bent part length) It is necessary to make it less than the allowable bearing stress.
However, with the bending portion length obtained from the conventional narrow reinforcing bar width and the bending diameter specified in JASS5, the bearing pressure generated when the tensile force at the time of yielding of the reinforcing bar, which is not reduced by the adhesion resistance of the straight portion, is applied to the concrete. It is not possible to secure a bearing area that is less than the allowable bearing stress level.

In the reinforcing bar that joins the foundation footing that is welded to the side of the steel pipe of the pile and that is connected to the upper part, the conventional bent part just above the welded part where the straight anchoring length is short from the anchoring origin at the top of the pile is the adhesion resistance of the straight part When the tensile force at the time of yielding of a reinforcing bar that does not decrease due to is applied, it cannot resist the bearing pressure acting in the radial direction with the bearing strength of the concrete.
Therefore, the tensile force acting on the reinforcing bar is not a bearing force on the concrete, but acts as a radial out-of-plane component to peel off the weld between the pile head and the pile head reinforcing bar. There is a risk of damage.

In the pile head joining method that resists the pile head bending moment mainly by reinforcing the pile head with reinforcing bars, the pile head resistance bending moment, that is, the pile head bending strength, increases as the arrangement diameter of the pile head reinforcing bars increases. I can do it.
However, in the case of a linear reinforcing bar welded to the pile head steel pipe, it is impossible to arrange it larger than the arrangement diameter obtained by adding the reinforcing bar diameter to the outer diameter of the pile, and it is impossible to adjust the pile head bending strength. is there.
In addition, the arrangement | positioning diameter of a pile head reinforcement is the center distance of the pile head reinforcement at the pile upper end position.

  The present invention solves the above problems by developing a reinforced concrete structure in which a bending pressure reinforcing plate with a pressure bearing plate attached to a bending portion of the reinforcing bar and a bending strength reinforcing rod with a pressure bearing plate are fixed in the concrete. Is.

Bending processed reinforcing bars with bearing plates are installed with bearing plates that have been increased to the required bearing width relative to the reinforcing bar width. It is possible to ensure a bearing area that is less than or equal to the allowable bearing stress level of the rebar, even if it is a rebar bending part where the tensile force during yielding of the rebar does not decrease due to adhesion resistance of the linear part It can prevent the bearing pressure failure of concrete.
Therefore, the bending rebar with bearing plate will cause bearing failure in concrete even when it is bent directly on and near the pile with few straight parts from the fixing starting point, as not specified in JASS5 etc. Without making it possible to dodge the interfering reinforcing bars.

For reinforcing bars that are welded to the side of the steel pipe of the pile and are joined to the foundation footing that is built on top of it, the bent reinforcing bars with bearing plates are tensioned at the time of yielding of the reinforcing bars that are not reduced by the adhesion resistance of straight parts such as directly above the weld Even in the rebar bending part where the force acts, the radial bearing pressure generated in the concrete can be reduced below the allowable bearing stress level of the concrete by increasing the bearing area of the bearing plate. It is possible to prevent an out-of-plane direction component force that peels off the welded portion of the pile head and the pile head reinforcement that is damaged.

In the method of resisting the pile head bending moment mainly by reinforcing the pile head with a reinforcing bar, the pile head resistance bending moment, that is, the pile head bending strength is increased as the arrangement diameter of the pile head reinforcing bar at the upper end position of the pile is increased. I can do it.
Therefore, the bending rebar with bearing plate adjusts the angle of the bent part with bearing plate and the number of bent parts that are fixed to the side of the pile in the connection between the pile and the foundation footing built on the pile. By disposing the pile head reinforcement bar at the upper end position away from the outside of the pile so as to increase the resistance bending moment of the pile head joint, that is, the pile head bending strength can be increased.

FIG. 1 is an elevation view of a bent reinforcing bar with a bearing plate according to a first embodiment of the present invention. FIG. 2 is an elevational view of the bent reinforcing bar with a bearing plate from the direction of the arrow A in FIG. FIG. 3 is a detailed cross-sectional view showing a welded portion between a deformed steel bar with a groove and a bearing plate taken along line B-B in FIG. 2. FIG. 4 is an elevational view of a pile head joint structure between a steel pipe pile and a foundation footing using the reinforcing bar bending rebar with a bearing plate of Example 2 according to the present invention. FIG. 5 is a cross-sectional view taken along line CC in FIG. FIG. 6 is an elevational view of a pile head joint structure between a steel pipe pile and a foundation footing using the reinforcing bar bending rebar with a bearing plate of Example 3 according to the present invention. 7 is a cross-sectional view taken along the line DD of FIG. FIG. 8 is an elevational view of a pile head joint structure between a steel pipe pile and a foundation footing using the reinforcing bar bending rebar with a bearing plate of Example 4 according to the present invention. FIG. 9 is a cross-sectional view taken along line EE in FIG.

  Here, with reference to the drawings, Examples 1 to 4 of the reinforced concrete structure in which the bending plate reinforcing plate with the bearing plate attached to the bent portion of the reinforcing bar and the bending rod with the bearing plate fixed in the concrete are fixed in the concrete. explain.

FIG. 1 is an elevational view of a bent reinforcing bar 1 with a bearing plate according to the invention of claim 1.
The rebar 2 is generally a round steel, a deformed steel bar with a node 5 formed on the surface, and a deformed steel bar 3 with a groove formed with a node 5 and a groove 4.
In addition, the groove | channel 4 is a groove | channel suitable for the welding formed with the deformed steel bar 3 with a groove | channel, and the bearing plate 8, and melts a welding metal and forms a welding part.
The folding reinforcing bar 1 with a bearing plate of the first embodiment is a bending reinforcing bar with a bearing plate in which an arbitrary portion of the reinforcing bar is bent and the bearing plate 8 is attached to the bent portion, and is deformed with a groove. In the figure, a support plate 8 is attached by welding 9 to a groove 4 on a bent portion 6 in which two portions of a steel bar 3 are bent at about 45 °.
Further, the bearing plate 8 can be mechanically fixed to the reinforcing bar bending portion 6.

FIG. 2 is an elevational view of the bent reinforcing bar 1 with a bearing plate as seen from the direction A in FIG.
The supporting plate 8 shows an example in which a steel plate having a width that secures about three times the reinforcing bar width necessary for the supporting resistance and a length that covers the bent portion 6 is used.
In some cases, the bearing plate 8 may be a striped steel plate having convex portions that are effective for the attachment of stripes on the surface, or a curved plate that is formed on a curved surface in order to disperse the bearing pressure.

FIG. 3 is a detailed cross-sectional view showing the deformed steel bar 3 with a groove, the groove 4 of the bearing plate 8 and its welded portion 9 along the line BB in FIG.
The weld 9 between the deformed steel bar 3 with a groove and the bearing plate 8 is attached by welding the groove 4 and the bearing plate 8 formed in the axial direction of the deformed steel bar 3 with a groove.
The bearing plate 8 may be flared or butt welded to the side of the groove 4 on the surface of the deformed steel bar 3 with a groove 5.
Further, the attachment of the reinforcing bar 2 and the bearing plate 8 such as round steel and deformed steel bar in which the groove 4 is not formed is generally performed by flare welding.
However, in order to ensure adhesion of round steel, it is necessary to attach a fixing body to the end.

FIG. 4 shows welding of the bending reinforcing bar 1 with a bearing plate to the side surface of the pile head steel pipe 11 of the steel pipe pile 10 according to the invention of claim 2 and claim 3 and the reinforcing bar bending part 6 in the foundation footing 12. It is the elevation which showed the pile head joining structure which joins the steel pipe pile 10 and the foundation footing 12 built in the upper part by fixing.
It has a reinforced concrete structure in which the bending rebar with the bearing plate is fixed in the concrete.
The support plate 8 of the bent reinforcing bar 1 with the support plate is attached in the direction facing the pile head steel pipe 11 inside the processed reinforcing bar 1.
The bearing plate 8 can be attached outside the processed reinforcing bar 1.
In this second embodiment, in order to dodge the reinforcing bars arranged in the vicinity of the pile such as the base reinforcement installed about 75 mm from the upper end of the pile, the deformed steel bar 3 with a groove is folded at about 15 ° at one place with a bearing plate. It is an example of construction of bending work reinforcement 1.
In addition, although the bending rebar 1 with a bearing plate has shown what welded 13 to the side surface of the pile head steel pipe 11, the number according to the intensity | strength required for a pile head junction part will be arrange | positioned.
In addition, although the pile head joining structure of the present Example 2 has shown the bending rebar 1 with a bearing plate welded to the pile head steel pipe 11, it is screw-type joining to the end plate in the pile head upper end part of an existing concrete pile. Or it is applicable also to the bending part of the pile head reinforcement which carries out stud welding.
In addition to the pile head joint structure of this embodiment, the bending rebar 1 with a bearing plate is a concrete structure that is fixed in a concrete structure such as a column and beam main bar, a foundation beam main bar, and a steel frame embedded column base reinforcement. Applicable.

  FIG. 5 is a cross-sectional view taken along line CC in FIG.

FIG. 6 shows the steel pipe pile 10 and its upper part by welding the bending rebar 1 with a bearing plate to the side of the pile head steel pipe 11 of the steel pipe pile 10 and fixing the reinforcing bar bent part 6 in the foundation footing 12. It is the elevation which showed the pile head joining structure which joins the foundation footing 12 constructed | assembled in FIG.
In the third embodiment, a deformed steel bar 3 with a groove is bent at two locations around 45 ° in order to dodge a base plate larger than the pile diameter installed on the upper part.
In addition, in order to resist the punching shearing force that causes the cover concrete outside the bent portion to be chipped, a ring-shaped strip is attached to each position of the supporting plate 8 of the bending reinforcing bar 1 with the supporting plate by welding or the like. There is also.

7 is a cross-sectional view taken along the line DD of FIG.

FIG. 8 shows that the bent reinforcing steel bar 1 with a bearing plate welded 13 to the side surface of the pile head steel pipe 11 is connected to the side surface of the pile head steel pipe 11 at about 45 ° within the side surface of the pile. Pile head joint structure in which the pile head reinforcement bars are arranged outside the pile diameter at the upper end position of the pile by dodging the base plate larger than the pile diameter installed at the top of the pile by bending two places. FIG.
In addition, the bending part 6 which contact | connects the pile head steel pipe 11 of the bending rebar 1 with a bearing plate shows the example which attached the bearing plate 8 by butt-welding 9 to the side surface of the groove | channel 4 of the deformed bar 3 with a groove | channel. However, if there is no problem in terms of strength and fit, it may be attached to the surface of the outer joint 5 or the inside of the groove 4.
Further, in the fourth embodiment, an example is shown in which the bearing plates 8 are attached to the deformed steel bar 3 with a groove one by one. However, several ring bearing plates 8 are formed by collecting the bearing plates 8. It can also be attached to the rebar bending part 6.
Furthermore, the steel pipe pile 10 and the bending rebar 1 with a bearing plate can be made into an integral structure by welding via the ring-shaped bearing plate 8, the pile head steel pipe 11, and metal fittings.

FIG. 9 is a cross-sectional view taken along the line E-E in FIG. 8, and the bent reinforcing steel bar 1 with a bearing plate that joins the steel pipe pile 10 and the foundation footing 12 constructed on the steel pipe pile 10 is piled up at the pile upper end position. The pile head joint structure arranged outside the diameter is shown.

DESCRIPTION OF SYMBOLS 1 Bending rebar with bearing plate 2 Reinforcing bar 3 Deformed bar steel with groove 4 Groove formed into reinforcing bar 5 Node molded into reinforcing bar 6 Reinforcing bar bending part 7 Reinforcing bar straight part 8 Bearing pressure plate 9 Bearing plate and reinforcing bar bending 10 Steel pipe pile 11 Pile head steel pipe 12 Foundation footing 13 Welded part between pile head steel pipe and bending rebar with bearing plate 14 Arrangement diameter of bending rebar with bearing plate at pile upper end position (rebar core Distance)

Claims (3)

A bending rebar with a support plate in which any part of the rebar is bent and a support plate is attached to the bent part. 2. A reinforced concrete structure in which the bent reinforcing bar with a bearing plate according to claim 1 is fixed in concrete. The reinforced concrete structure in which the bending reinforcing bar with bearing plate according to claim 1 is fixed in the concrete, and the bending reinforcing bar with supporting plate is fixed to the pile so that the bending portion with the supporting plate is fixed in the foundation footing concrete. A welded structure of steel pipe piles, concrete piles wound with steel pipes, and a foundation footing built on top of the steel pipe piles.