JP2009019356A - Structure and method for jointing bridge pier and footing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure and a method for joining bridge piers and a footing and capable of securing sufficient quality at reasonable cost. <P>SOLUTION: In the structure 1 for joining bridge piers and a footing, one-side ends of deformed reinforcing bars 6 are buried and anchored to the footing 4, and their other ends are buried and anchored to concrete 7 filled in the steel pipe 2. The deformed reinforcing bars 6 form a reinforced concrete body 8 together with the concrete 7. The reinforced concrete body 8 plays the role of transmitting a horizontal force acting on a top of a steel pier 3 to the footing 4 by being bent and resistant to the centrifugal distortion of the steel pipe 2 caused by the horizontal force. Since the inner surface 9 of the steel pipe 2 opposed to the deformed reinforcing bars 6 is smooth-finished, it is possible to bring the deformed reinforcing bars 6 close to the inner surface of the steel pipe 2 to a minimum distance. Since protrusions 10 are formed on the inner surface of the steel pipe 2 located above the reinforcing bars 6 for joining the steel pipes, it is possible to transmit a compressive load from the bridge pier 3 to the footing 4 via the reinforced concrete body 8 by an engaging action with the filled concrete 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a joining structure and method of a pier and a footing used when joining a lower end of a steel pier to an RC footing.

  When joining the lower end of a steel pier to the foundation, a steel frame called an anchor frame is manufactured in advance, and then embedded in a footing, which is a reinforced concrete foundation, and then anchor bolts extending from the anchor frame are used. A method of bolting the lower end of a steel pier to an anchor frame has been widely used.

  Recently, in addition to such a method, a steel pipe with a large diameter called a socket steel pipe is installed on the foundation constructed in the ground, and then the lower end of the steel pier is inserted into the socket steel pipe, and then the steel pier A method of integrating the lower end of the steel pier, the socket steel pipe and the foundation by filling concrete between the outer surface and the inner surface of the socket steel pipe is also known, and according to such a method, rapid construction is possible. Therefore, it is possible to proceed with construction in a short construction period in a place with a lot of traffic.

JP-A-9-13320 JP-A-9-209308

  However, the joining method using an anchor frame is inherently expensive to produce an anchor frame. Therefore, when the size of a bridge increases, the production cost increases due to the increase in the size of the anchor frame and the strengthening of steel materials. In addition, the so-called double pipe construction method using a socket steel pipe inevitably increases the construction cost because the steel pipe is used twice.

  Under these circumstances, cost-reducing construction methods have been researched and developed from various viewpoints.For example, a rib is provided on the inner surface of a steel pipe constituting a bridge pier, and a reinforcing bar is arranged at a position facing the rib to provide concrete. Although there is a construction method (Patent Documents 1 and 2), there is no joining method that can ensure sufficient quality at a reasonable cost because the rib processing on the inner surface of the steel pipe requires a reasonable cost. is there.

  The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide a structure and method for joining a pier and a footing that can ensure sufficient quality at a reasonable cost.

  In order to achieve the above-mentioned object, the joining structure of a pier and a footing according to the present invention includes a pier and a footing formed by joining a pier composed of a steel pipe to a footing formed of reinforced concrete as described in claim 1. In the joining structure of

  The steel pipe is disposed above the footing in a vertical posture so that a predetermined gap is formed between the lower end of the steel pipe and the upper surface of the footing, and one end of the steel pipe is embedded in the footing. A reinforced concrete body composed of a reinforcing bar and a concrete filled in the steel pipe and the other end of the reinforcing rod for joining the steel pipe is embedded in the steel pipe is formed in the steel pipe, and is an inner surface of the steel pipe and in the steel pipe Of the inner surface in contact with the filled concrete, the inner surface facing the steel pipe joining rebar is made smooth and a protrusion is provided on the inner surface located above the steel pipe joining rebar.

  Moreover, the joining structure of the bridge pier and the footing according to the present invention is such that a lap joint forming a lap joint with the steel pipe joining rebar is opposed to the projection and a horizontal cross-sectional position is more than that of the steel pipe joining rebar. Is embedded in the concrete filled in the steel pipe so as to be on the center side of the steel pipe.

  Further, the method for joining the pier and the footing according to the present invention is as described in claim 3, in the method for joining the pier and the footing for joining the pier composed of the steel pipe to the footing formed of reinforced concrete,

  The steel pipe joining rebar is formed so that one end of the steel pipe joining rebar is embedded in the footing, and a predetermined gap is formed between the lower end of the steel pipe and the upper surface of the footing. The steel pipe is positioned above the footing in a vertical posture so that the other end of the steel pipe is disposed in the steel pipe, the gap is closed with a predetermined formwork material, and the other end of the steel pipe joining rebar is embedded. The steel pipe is filled with concrete, and the inner surface of the steel pipe that is in contact with the concrete filled in the steel pipe is smoothed on the inner surface facing the steel pipe joining rebar. A finish is provided, and protrusions are provided on the inner surface located above the steel pipe joining rebar.

  The method for joining the pier and the footing according to the present invention is to form the mold material so that the vertical load of the steel pipe can be temporarily received, and after the concrete filled in the steel pipe is hardened, The material is removed.

  Further, the method for joining the pier and the footing according to the present invention is such that a lap joint forming a lap joint between the steel pipe joining rebar is opposed to the projection and a horizontal cross-sectional position is more than that of the steel pipe joining rebar. Is embedded in the concrete filled in the steel pipe so as to be on the center side of the steel pipe.

  As described above, the conventional joint structure (Patent Documents 1 and 2) extends the reinforcing bar fixed to the footing into the steel pipe so as to face the rib formed on the inner surface of the steel pipe, and then puts the concrete in the steel pipe. It is to be filled.

  According to such conventional technology, the effect of restraining the concrete by the steel pipe can be expected, and the installation of the formwork and the demolding work at the time of placing the concrete are unnecessary, which is extremely useful as compared with the RC piers until then. It can be said that it is a simple construction method.

  However, due to the need to ensure covering with filled concrete, when placing reinforcing bars so as to face the ribs formed on the inner surface of the steel pipe, the position of the reinforcing bars should be the same as the rib protrusion. Need to be retreated.

  This means that when the reinforcing bars and filled concrete in the steel pipe are considered as reinforced concrete bodies that resist bending moments, the distance between the reinforcing bars along the horizontal direction is shortened and the bending resistance is reduced.

  As a result of accumulating research and development, the present applicant, as a result of accumulating research and development, as described above, the steel pipe in the vertical posture so that a predetermined gap is formed between the lower end of the steel pipe and the upper surface of the footing. A reinforced concrete body, which is arranged above the footing, and which is composed of a steel pipe joining rebar with one end buried in the footing and a concrete filled in the steel pipe and the other end of the steel pipe joining rebar is buried. Of the inner surface of the steel pipe that is formed in the steel pipe and is in contact with the concrete filled in the steel pipe, the inner surface facing the steel pipe joining rebar is made smooth, and the steel pipe joining rebar This has led to a novel invention in which protrusions are provided on the inner surface located further upward.

  In this way, it is possible to transmit the compressive load from above the pier to the footing through the reinforced concrete body by the meshing action of the protrusion provided on the inner surface of the steel pipe and the reinforced concrete body, and Since the facing inner surfaces are smoothed by eliminating protrusions, the steel pipe joining rebar can be brought closer to the inner surface of the steel pipe, and the distance between the rebars along the horizontal direction can be made larger than before.

  The steel pipe targeted by the present invention can have an arbitrary cross-sectional shape, and for example, a cross-sectional shape such as a circle, a square, or a polygon can be considered. For example, when a bridge is constructed in a mountainous area, the pier may become high, and in that case, the steel pipe is added by welding or the like.

  When the pier is composed of a plurality of steel pipes, the steel pipe of the present invention can be composed of a single steel pipe, and can also be composed of a plurality of steel pipes. The lowermost steel pipe and the steel pipe disposed above the lowermost stage and provided with protrusions on the inner surface can be used. In addition, when the steel pipe of the present invention is constituted by a plurality of steel pipes, the steel pipe disposed above does not need to be a steel pipe joined immediately above the lowermost steel pipe, and some steel pipes are interposed therebetween. It doesn't matter.

  In addition, although the steel pipe which comprises a pier is often called a steel shell, in this invention, it shall call a steel pipe as a concept also including a steel shell for convenience.

  The footing is made of reinforced concrete and generally accompanied by a pile, but in the present invention, the foundation structure is constituted only by the footing or it is joined to the pile and its head. It does not matter whether the foundation structure is composed of footing.

  The steel pipe joining rebar is one in which one end is embedded in the footing and the other end is embedded in the concrete filled in the steel pipe, and can be composed of a deformed reinforcing bar, for example.

  The smooth finish on the inner surface of the steel pipe means that the separation distance between the steel pipe joining rebar and the inner surface of the steel pipe is kept to the minimum necessary. The purpose is to separate the reinforcing bars, and it is not intended to eliminate unevenness of, for example, about 1/10 or less of the cross-sectional dimension of the steel pipe joining reinforcing bars.

  On the other hand, the protrusions provided on the inner surface located above the steel pipe joining rebar are for the purpose of meshing with the concrete filled in the steel pipe, and by this meshing action, the compressive load from above the pier However, since the steel pipe joining rebar does not face the protrusion, there is no concern that the distance between the rebars along the horizontal direction will be shortened.

  It should be noted that an adhesive force is generated between the steel pipe inner surface and the filled concrete at the location where the finish is smooth, and a part of the compression load may be transmitted to the footing through the location where the finish is smooth. .

  The steel pipe joining rebar can be brought close to the inner surface of the steel pipe to the minimum distance by a configuration in which the steel pipe joining rebar does not face the protrusion, but a lap joint that forms a lap joint with the steel pipe joining rebar May be provided separately so that the overlapping muscles face the protrusions.

  In this case, overlaying with filled concrete is required for the lap bars, so the horizontal cross-sectional position of the lap bars must be closer to the center of the steel pipe than the steel pipe joint reinforcing bars. It is possible to sufficiently secure the steel pipe joining rebar with the increased distance between them, and the lap joint forms a lap joint between the steel pipe joining rebar and the protrusion, so that the pulling force acting on the steel pipe is footed. It becomes possible to support with.

  In order to construct a joint structure between a pier and a footing according to the present invention, first, the footing is formed so that one end of a steel pipe joining rebar is embedded in the footing, and then the lower end of the steel pipe and the upper surface of the footing The steel pipe is positioned above the footing in a vertical posture so that a predetermined gap is formed between the steel pipe and the other end of the steel pipe joining rebar is disposed in the steel pipe. The steel pipe may be filled with concrete so that the other end of the steel pipe joining rebar is buried and sealed with the frame material.

  Here, if the formwork material is configured so that the vertical load of the steel pipe can be temporarily received, it is possible to easily perform the temporary reception of the steel pipe before the concrete filling and placing. In such a case, the mold material is removed after the concrete filled in the steel pipe is cured.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a structure and a method for joining a pier and footing according to the present invention will be described below with reference to the accompanying drawings. Note that components that are substantially the same as those of the prior art are assigned the same reference numerals, and descriptions thereof are omitted.

  FIG. 1 is a view showing a joint structure between a pier and a footing according to the present embodiment. As can be seen from the figure, the pier and footing joint structure 1 according to the present embodiment is formed by joining a pier 3 formed of a steel pipe 2 to a footing 4 formed of reinforced concrete.

  Between the lower end of the steel pipe 2 and the upper surface of the footing 4, the steel pipe 2 is arranged above the footing 4 in a vertical posture so that a gap h is formed.

  One end of a deformed rebar 6 as a steel pipe joining rebar is embedded in the footing 4, and the other end of the deformed rebar is embedded in a concrete 7 filled in the steel pipe 2.

  Each of the deformed reinforcing bars 6 is formed in a straight bar shape, and a plurality of deformed reinforcing bars may be arranged along the inner surface at a position separated from the inner surface of the steel pipe 2 by a predetermined distance d. As shown in FIG. If 2 is a square steel pipe, it may be arranged in a rectangular shape at a predetermined pitch, and if it is a circular steel pipe, it may be arranged in a circle.

  Here, the deformed reinforcing bar 6 forms a reinforced concrete body 8 together with the concrete 7 filled in the steel pipe 2, and the reinforced concrete body 8 has a horizontal force acting on the head of the pier 3 as will be described later. It plays a role of bending resistance against rotational deformation of the steel pipe 2 due to the horizontal force and transmitting the horizontal force to the footing 4.

  The steel pipe 2 has a smooth finish on the inner surface 9 facing the deformed reinforcing bar 6 among the inner surfaces, and the deformed reinforcing bar 6 can be brought close to the inner surface of the steel pipe 2 to a minimum distance.

  On the other hand, a protrusion 10 is provided on the inner surface of the steel pipe 2 positioned above the steel pipe joining rebar 6, and a compressive load from the bridge pier 3 is applied to the footing 4 via the reinforced concrete body 8 by meshing action with the filling concrete 7. It can communicate.

  In order to construct the joint structure 1 between the pier and the footing according to the present embodiment, first, as shown in FIG. 2, after the pile 11 is driven into the ground (not shown), the footing 4 is attached to the head of the pile. In the foundation work, the footing is formed so that one end of the deformed reinforcing bar 6 is embedded in the footing 4.

  As described above, if the deformed reinforcing bars 6 are embedded in the footing 4 so that a plurality of deformed reinforcing bars 6 are arranged along the inner surface at a position separated by a predetermined distance d from the inner surface of the steel pipe 2 erected in a later step, Good.

  Next, as shown in FIG. 3, the mold material 12 is placed on the upper surface of the footing 4. The formwork material 12 is composed of a rectangular frame having an L-shaped cross section. By placing the lower end of the steel pipe 2 on the shoulder 13 formed on the inner peripheral side, the lower end of the steel pipe and the upper surface of the footing 4 are formed. The gap h is closed and the load on the steel pipe 2 can be temporarily received.

  The formwork 12 is attached to the upper surface of the footing 4 so as to surround the deformed reinforcing bar 6 so that the other end of the deformed reinforcing bar 6 is disposed in the steel pipe 2 in the next step.

  Next, the lower end of the steel pipe 2 is placed on the shoulder 13 of the mold material 12, the steel pipe 2 is suspended above the footing 4 in a vertical posture, and the steel pipe 2 is temporarily received by the mold material 12.

  Next, the concrete 7 is cast and filled in the steel pipe 2 to a height at which the protrusions 10 formed on the inner surface of the steel pipe are buried.

  When the cast concrete 7 is hardened, the formwork 12 is finally removed.

  In the pier-footing joint structure 1 constructed in this way, as shown in FIG. 4, a compressive load acts from above the pier 3, and this compressive load is reinforced concrete body 8 formed in the steel pipe 2. , And the compression load is supported by the footing.

  Further, as shown in FIG. 5, assuming that a horizontal force P acts on the head of the pier 3 in the right direction, the steel pipe 2 tries to rotate clockwise by the horizontal force.

Therefore, in the reinforced concrete body 8, the supporting pressure from the steel pipe 2 acts on the side surface, and the tensile force T from the deformed reinforcing bar 6 located on the left side is applied to the compressive force C from the deformed reinforcing bar 6 located on the left side bottom surface. Compressive force C ₂ from the right upper surface of ₁ and footing 4 acts on the right bottom surface, but the reinforced concrete body 8 is bent to resist these forces as an RC member made of deformed reinforcing bars 6 and filled concrete 7, and thus acts on the pier 3. The acting horizontal force P is transmitted to the footing 4 through the reinforced concrete body 8 and supported by the footing.

  As described above, according to the joining structure 1 and method of the pier and footing according to the present embodiment, the meshing action of the protrusion 10 provided on the inner surface of the steel pipe 2 and the reinforced concrete body 8 causes the pier 3 from above. A compressive load can be transmitted to the footing 4 through the reinforced concrete body 8 and the inner surface 9 of the steel pipe 2 opposite to the steel pipe joining rebar 6 is smoothed without protrusions. It is possible to approach the inner surface of the steel pipe 2 up to the minimum concrete covering thickness, and the distance between the reinforcing bars, which is the horizontal distance between the deformed reinforcing bars 6 and 6, can be increased.

  Therefore, the bending strength of the reinforced concrete body 8 is increased, and the distance between the reinforcing bars of the deformed reinforcing bars 6 and 6 is increased, so that the bending strength of the deformed reinforcing bar 6 embedded in the footing 4 is not sufficiently increased. It becomes possible to give proof stress.

  Although not particularly mentioned in the present embodiment, when the pier 3 is long, it is possible to sequentially add a steel pipe similar to the steel pipe onto the steel pipe 2 by welding or the like. It is possible to constitute the steel pipe and the steel pipe provided with protrusions on the inner surface with different steel pipes.

  Further, in this embodiment, the mold material 12 has a function of temporarily receiving the weight of the steel pipe 2, but the steel pipe 2 is provisionally received by another known means, and the mold material 12 has only the function of the mold. You may make it have. In this case, it is arbitrary whether the mold material 12 is removed after the concrete is hardened.

  Moreover, in this embodiment, it was set as the structure which can make the deformed rebar 6 close to the inner surface of the steel pipe 2 to the minimum distance by making the deformed rebar 6 not to face the protrusion 10, but it is shown in FIG. In this manner, a lap bar 61 that forms a lap joint with the deformed bar 6 may be provided separately, and the lap bar may be opposed to the protrusion 10.

  In this case, since the covering with the filling concrete 7 is necessary for the overlap bars 61, it is necessary to make the horizontal cross-sectional position of the overlap bars 61 closer to the center side of the steel pipe 2 than the deformed reinforcing bars 6. It is possible to sufficiently secure the deformed reinforcing bars 6 and 6 in which the distance between the reinforcing bars is increased, and the overlapping bars 61 act on the steel pipe 2 by forming a lap joint between the deformed reinforcing bars 6 and the protrusions 10. The pulling force to be supported can be supported by the footing 4.

It is a figure which shows the junction structure 1 of the bridge pier and footing which concern on this embodiment, (a) is a longitudinal cross-sectional view, (b) is sectional drawing which follows an AA line. The construction procedure figure which showed the procedure of the joining method of the bridge pier and footing which concern on this embodiment. The construction procedure figure which showed the procedure of the joining method of the bridge pier and footing which concern on this embodiment continuously. The figure which showed the effect | action of the joining structure and method of the bridge pier and footing which concern on this embodiment. The figure which similarly showed the effect | action of the joining structure and method of the bridge pier and footing which concern on this embodiment. It is a figure which shows the junction structure of the bridge pier and footing which concern on a modification, (a) is a longitudinal cross-sectional view, (b) is sectional drawing which follows a BB line.

Explanation of symbols

1 Joint structure of pier and footing 2 Steel pipe 3 Bridge pier 4 Footing 6 Deformed bar (steel pipe joint)
7 Filled concrete 8 Reinforced concrete body 9 Steel pipe inner surface 10 Protrusion 12 Formwork material 61 Overlay

Claims (5)

In the joint structure of pier and footing, which is formed by joining a pier composed of steel pipes to a footing formed of reinforced concrete,
The steel pipe is disposed above the footing in a vertical posture so that a predetermined gap is formed between the lower end of the steel pipe and the upper surface of the footing, and one end of the steel pipe is embedded in the footing. A reinforced concrete body composed of a reinforcing bar and a concrete filled in the steel pipe and the other end of the reinforcing rod for joining the steel pipe is embedded in the steel pipe is formed in the steel pipe, and is an inner surface of the steel pipe and in the steel pipe A bridge pier and a footing characterized in that, among the inner surfaces in contact with the filled concrete, the inner surface facing the steel pipe joining rebar has a smooth finish, and a protrusion is provided on the inner surface located above the steel pipe joining rebar. Bonding structure. The steel pipe is filled in such a manner that a lap joint forming a lap joint with the steel pipe joining rebar is opposed to the projection and the horizontal cross-sectional position is closer to the center side of the steel pipe than the steel pipe joining rebar. The joint structure of a pier and a footing according to claim 1, which is embedded in concrete. In the joining method of the pier and footing that joins the pier composed of steel pipes to the footing formed of reinforced concrete,
The steel pipe joining rebar is formed so that one end of the steel pipe joining rebar is embedded in the footing, and a predetermined gap is formed between the lower end of the steel pipe and the upper surface of the footing. The steel pipe is positioned above the footing in a vertical posture so that the other end of the steel pipe is disposed in the steel pipe, the gap is closed with a predetermined formwork material, and the other end of the steel pipe joining rebar is embedded. The steel pipe is filled with concrete, and the inner surface of the steel pipe that is in contact with the concrete filled in the steel pipe is smoothed on the inner surface facing the steel pipe joining rebar. A method for joining a bridge pier and a footing, characterized in that a finish is provided and a protrusion is provided on an inner surface located above the steel pipe joining rebar. The method for joining a pier and a footing according to claim 3, wherein the mold frame material is configured to temporarily receive a vertical load of the steel pipe, and the mold material is removed after the concrete filled in the steel pipe is hardened. . The steel pipe is filled in such a manner that a lap joint forming a lap joint with the steel pipe joining rebar is opposed to the projection and the horizontal cross-sectional position is closer to the center side of the steel pipe than the steel pipe joining rebar. The method for joining a pier and a footing according to claim 3 embedded in concrete to be carried out.

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