JP6262966B2 - Reinforced concrete pedestal - Google Patents

Description

  The present invention relates to a reinforced concrete pedestal used for a bridge pier or the like of a bridge.

A reinforced concrete pedestal used to support an upper structure such as a bridge girder as a pier is composed of a foundation called footing and a frame provided on the footing. Such a configuration is basically the same whether it is provided on land or provided to be immersed in water such as a river.
When an earthquake occurs, stress is applied to the bridge that causes the frame to bend and deform. Since such stress acts particularly on the lower part of the frame, if the shaking due to the earthquake is large, the concrete may be cracked in the concrete below the frame and the rigidity may be reduced. Then, the reinforced concrete pedestal functions as a plastic hinge that absorbs vibration energy by plastic deformation of the lower part of the housing for a certain period.

  Conventionally, the lower part of the pedestal is made of fiber reinforced concrete to increase the toughness of the lower part of the pedestal, thereby preventing damage to the concrete and main reinforcing bars in the core during an earthquake and enabling it to function longer as a plastic hinge Has been proposed (see Patent Document 1).

JP 2009-144344 A

However, in the case of reinforced concrete pedestals provided in rivers, the lower part of the frame, which is expected to be a plastic hinge, is located in the water. Will infiltrate. And in the process of bending deformation of the skeleton returning to the original and bending deformation to the opposite side, the cracks will close once, but at that time the water sandwiched between concrete and concrete is pressed from the upper and lower concrete . Therefore, a phenomenon called a wedge effect occurs in which high-pressure water further breaks the concrete inside. This wedge effect is repeated as long as the frame continues to shake, during which the cracks in the core concrete progress.
In other words, reinforced concrete pedestals that are soaked in water, such as rivers, have a problem that their functions as plastic hinges are degraded earlier than those on the ground due to the effects of such phenomena. .

  This invention is made | formed in view of the said subject, and it aims at making the function as a plastic hinge of the reinforced concrete pedestal provided in water hard to deteriorate.

In order to solve the above-mentioned problems, the present invention comprises a footing provided on the bottom of the water, a housing erected upward from the footing, and a main reinforcing bar disposed across the footing and the housing. A reinforced concrete pedestal comprising:
The core portion of the casing is constituted by a plurality of concrete blocks stacked in the vertical direction, and grooves are formed on the upper surface and / or the lower surface of the concrete block so that at least one end thereof reaches the end of the upper surface or the lower surface. It is characterized by.

In this way, the frame has a discontinuous surface between the concrete blocks, so when the frame is bent and deformed by an earthquake or the like, the concrete on the outer periphery of the frame is discontinuous. Cracks occur on the surface extension, and cracks are less likely to occur in concrete blocks. The water that has entered from the cracks that entered the concrete at the outer periphery only enters and exits the discontinuous surface, so that cracks do not progress inside the concrete block, and the frame can continue to function as a plastic hinge. Even if a concrete block is cracked, the wedge action of water is less likely to occur.
In addition, by adjusting the thickness (height) of individual concrete blocks, the number of stacks, the position of stacking, etc., it is possible to control the position of cracks that occur in the concrete on the outer periphery of the frame. A plastic hinge according to various conditions can be formed.

In this way, a long and narrow space is formed between the concrete block and the concrete block so as to be connected to the outside of the concrete block, so that water entering between the concrete block and the concrete block is pressurized from the concrete block. Even if it receives, since it comes to release the pressure by flowing into a groove | channel, it can prevent that a crack progresses inside a concrete block by high water pressure.

Preferably, in the above invention, the groove is formed to extend in the bridge axis direction.
Since the frame swings in the direction of the bridge axis, the wedge action due to the water that has entered the cracks will act greatly in the direction of the bridge axis. In this way, the pressure of the water that entered between the concrete block and the concrete block Can be escaped more efficiently.

Moreover, in the said invention, it is good to make it form so that the said groove | channel may spread in a horizontal direction and / or a depth direction as it goes to the end of the said upper surface or lower surface.
In this way, since the outlet of the groove becomes large, the pressure of water entering between the concrete blocks can be released more efficiently.

Preferably, in the above invention, the concrete block is covered with a waterproof material.
In this way, even if the concrete block is cracked, the waterproof material can prevent water from entering the crack, so the water that enters between the concrete block and the concrete block It can prevent more reliably that a crack will progress.

Preferably, in the above invention, the concrete block may have a thickness that allows a plurality of the concrete blocks to be stacked from the footing to a height exceeding the width of the frame in the bridge axis direction.
Plastic hinges are likely to be formed in the part of the frame from the footing to the height of the width in the direction of the bridge axis, and it is expected that the cracks in the concrete on the outer periphery of the frame and the infiltration of water will increase compared to other parts However, if it does in this way, since a some discontinuous surface will be formed in a plastic hinge, the effect which suppresses the crack progress of the concrete block by water can further be heightened.

  ADVANTAGE OF THE INVENTION According to this invention, the function as a plastic hinge of the reinforced concrete pedestal provided in water can be made hard to deteriorate.

It is the figure which showed the reinforced concrete pedestal based on embodiment of this invention, (a) is the longitudinal cross-sectional view, (b) is a cross-sectional view.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, a reinforced concrete pedestal (hereinafter referred to as a pedestal 10) in this embodiment will be described. FIG. 1A is a longitudinal sectional view when the pedestal 10 is viewed from a direction perpendicular to the bridge axis (the width direction of the bridge), and FIG. 1B is a view when the pedestal 10 is viewed from above. FIG.

  As shown in FIG. 1A, the pedestal 10 is composed of a footing 1 embedded in the bottom of the water and a housing 2 erected upward from the footing 1. The casing 2 includes a block-shaped core concrete (concrete block) 21 stacked in an upward direction from the upper surface of the footing, a cover concrete (outer peripheral concrete) 22 around the core concrete 21, and an interior of the cover concrete 22. And the main rebar 23 arranged in the. On the frame 2, a bridge seat and a bridge girder (not shown) are provided.

The core concrete 21 has a prismatic shape that lies so that the direction perpendicular to the bridge axis direction is the longitudinal direction, and a plurality of core concretes 21 are stacked until the surface is above the water surface. Grooves 21 a extending from one end in the longitudinal direction to the other end are formed on the upper and lower surfaces of the core concrete 21. In addition, a plurality of grooves 21b extending from one end to the other end in the short direction and orthogonal to the grooves 21a are formed on the upper and lower surfaces of the core concrete 21. Each groove 21b is formed at equal intervals along the longitudinal direction of the core concrete. As it goes from the center orthogonal to the groove 21a toward the end, the horizontal direction and the depth direction (downward if the groove is formed on the upper surface). If the groove is formed on the lower surface, it is formed so as to spread upward). When the core concrete 21 is stacked, the grooves 21a and 21b formed on the lower surface of the upper core concrete 21 and the grooves 21a and 21b and a on the upper surface of the lower core concrete 21 are overlapped to form a circular shape as shown in FIG. A cross-sectional flow path 2c is formed. The surface of the core concrete 21 is coated with a waterproof material 21c.
In the figure, the core concrete 21 is shown thicker. However, the portion of the frame 2 from the lower end to the height approximately equal to the width of the pillar 10 in the bridge axis direction is a plastic hinge when a large earthquake occurs. Therefore, it is preferable to adjust the thickness so that a plurality of layers are stacked in this portion.

A plurality of main reinforcing bars 23 are arranged along the side peripheral surface of the core concrete 21 so as to surround the core concrete 21 and to extend in the vertical direction. The lower end portion of the main reinforcing bar 23 is fixed to the footing 1 and the upper end portion is fixed to a bridge seat portion (not shown).
The cover concrete 22 forms the outer periphery of the housing 2. The cover concrete 22 and the core concrete 21 are integrated, but when the cover concrete 22 is placed, the mortar paste cannot enter between the overlapping core concrete 21 and the core concrete 21, so the core concrete 21 that overlaps the top and bottom. The core concrete 21 is not integrated, and the housing 2 has a plurality of discontinuous surfaces 2a inside.

Next, the behavior of the pedestal 10 when a large earthquake occurs will be described.
For example, when a stress is applied to the bridge to move the superstructure to one end side in the bridge axis direction (left and right direction in FIG. 1 (a)), first, bending deformation is performed so that the frame 2 is bent toward one end side in the bridge axis direction. Begin to. Then, when the side surface on the other end side in the bridge axis direction of the frame 2 is pulled up and down and the deformation amount reaches a certain size, the cover concrete 22 is cracked. Although the cover concrete 22 and the core concrete 21 are integrated, since the gap between the core concrete 21 and the core concrete 21 is a discontinuous surface 2a, cracks are generated mainly on the extension of the discontinuous surface 2a. become. Moreover, the main reinforcing bar 23 on the other end side in the bridge axis direction, which was responsible for the tensile stress, yields. Thereafter, the lower part of the housing 2 functions as a plastic hinge.

  When the cover concrete 22 is cracked, water enters from the crack. When cracking occurs, the core concretes 21 that are in contact with each other inside are slightly separated to form a gap, so that the infiltrated water enters the gap. When the deflection of the housing 2 returns to the original state with water entering the gap, the water that has entered the gap receives pressure from the upper and lower core concrete, but this water flows into the groove 21a and moves sideways. By being discharged, the pressure of water is reduced. Moreover, since the surface of the core concrete 21 is waterproofed by the waterproof material 21 c, water does not enter the core concrete 21. Thereafter, the bending deformation of the housing 2 once returns to the original state, and the same action is applied when the bending deformation is performed toward the other end side in the bridge axis direction. After the earthquake, the cracked cover concrete 22 may peel off, but the core concrete 21 is not damaged, so the proof strength of the pedestal 10 is maintained at the same level as before the earthquake.

As described above, the core portion of the frame 2 provided in the reinforced concrete pedestal 10 of the present embodiment is constituted by the core concrete (concrete block) 21 that is stacked in the vertical direction.
By doing so, the frame 2 has a discontinuous surface 2a between the core concrete 21 and the core concrete 21. Therefore, when the frame 2 is bent and deformed by an earthquake or the like, the cover concrete 22 (the outer peripheral portion) Concrete) is cracked on the extension of the discontinuous surface 2a, and the core concrete 21 is less likely to be cracked. Since the water that has entered from the cracks entering the cover concrete 22 only enters and exits the discontinuous surface 2a, the cracks do not advance inside the core concrete 21, and the housing 2 can continue to function as a plastic hinge. . Even if the core concrete 21 is cracked, the wedge action of water hardly occurs.
In addition, by adjusting the thickness (height) of individual core concrete 21, the number of stacked cores, the stacking position, etc., the position of cracks generated in cover concrete 22 can be controlled. Plastic hinges according to conditions can be formed.

Moreover, in this embodiment, the groove | channel 21a is formed in the upper surface and / or lower surface of the core concrete 21 so that it may reach the end of an upper surface or a lower surface.
By doing so, an elongate space connected to the outside of the core concrete 21 is formed between the core concrete 21 and the core concrete 21, so that water that has entered between the core concrete 21 and the core concrete 21 Even if the pressure is received, the pressure is released by flowing into the groove 21a. Therefore, it is possible to prevent the crack from proceeding inside the core concrete 21 due to the high water pressure.

Moreover, in this embodiment, the core concrete 21 is covered with the waterproof material 21c.
By doing so, even if the core concrete 21 is cracked, the waterproof material 21c can prevent water from entering the crack. It can prevent more reliably that the crack of a core concrete will advance.

Further, in the present embodiment, the core concrete 21 has a thickness that allows a plurality of core concrete 21 to be stacked from the footing 1 to a height exceeding the width of the frame 2 in the bridge axis direction.
The plastic hinge is easy to be formed in the part of the frame 2 from the footing 1 to the height of the width in the direction of the bridge axis, and it is expected that the cover concrete 22 is more cracked and water enters than other parts. However, if it does in this way, since the some discontinuous surface 2a will be formed in a plastic hinge, the effect which suppresses the crack progress of the core concrete 21 by water can further be heightened.

As mentioned above, although this invention was concretely demonstrated based on embodiment, this invention is not limited to the said embodiment, It can change in the range which does not deviate from the summary.
For example, in this embodiment, one groove is formed along the longitudinal direction of the core concrete. However, the groove may be formed in the short direction, or may be formed in parallel or radially.
Moreover, in the said embodiment, although the groove | channel was formed in both the upper and lower surfaces of core concrete, since a flow path should just be formed between core concrete and core concrete, it is good also as either an upper surface or a lower surface.
Moreover, in this embodiment, although the manufacturing location of core concrete was not specifically limited, if it is a location which can install a formwork, a factory may be sufficient and a construction site may be sufficient. If manufactured near the construction site, the transport distance of the core concrete is shortened, so that the construction of the pedestal can be facilitated.

10 Reinforced concrete pedestal 1 Footing 2 Housing 21 Core concrete (concrete block)
21a, 21b Groove 21c Waterproofing material 22 Cover concrete (peripheral concrete)
23 Main reinforcement

Claims (5)

A reinforced concrete pedestal comprising: a footing provided at the bottom of the water; a housing erected upward from the footing; and a main rebar disposed across the footing and the housing;
The core of the casing is constituted by concrete blocks stacked in the vertical direction ,
A reinforced concrete pedestal characterized in that grooves are formed on the upper surface and / or lower surface of the concrete block so that at least one end thereof reaches the end of the upper surface or the lower surface . The reinforced concrete pedestal according to claim 1 , wherein the groove is formed to extend in a bridge axis direction. In accordance with the grooves toward the upper or lower surface of the end, the horizontal and / or reinforced concrete pedestal of claim 1 or 2, characterized in that it is formed so as to extend in the depth direction. The reinforced concrete pedestal according to any one of claims 1 to 3 , wherein the concrete block is covered with a waterproof material. Said concrete blocks, from said footing, any one of claims 1 to 4, wherein a stacking plural has a thickness as possible until a height greater than the width of the bridge axis direction of the skeleton Reinforced concrete pedestal described in 1.

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