Foundation structure of a building

Abstract

In a building foundation structure where a pile cap, comprising a steel pipe section joined to a steel column-beam joint and a concrete section inside, is provided as a foundation footing, and the steel pipe section of the pile cap is installed on a foundation slab constructed along the ground surface, increasing the thickness of the foundation slab contributes to improving the allowable bending strength of the pile head-side joint of the pile cap, thereby enabling a rational design. [Solution] The foundation footing 20 includes a pile cap 21 having a steel pipe section 23 and a concrete section 24, and a concrete foundation slab 17 constructed along the ground surface Ga, with the steel pipe section 23 of the pile cap 21 installed on the foundation slab 17. The concrete section 24 of the pile cap 21 is provided with reinforcing main bars 30 whose lower end is embedded in the foundation slab 17 and which extend along the axis C of the steel pipe section 23.

Description

Technical Field

[0001] The present invention relates to a foundation structure of a building including a pile cap having a steel pipe portion joined with a steel structure column-beam joint and a concrete portion inside thereof, wherein the steel pipe portion of the pile cap is installed on a foundation slab constructed along the ground surface.

Background Art

[0002] A foundation structure of a building including a pile cap having a steel pipe portion joined with a steel structure column-beam joint and a concrete portion inside thereof, wherein the steel pipe portion of the pile cap is installed on a foundation slab constructed along the ground surface is known (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional foundation structure of a building provided with a pile cap and a foundation slab as described above, when calculating the allowable bending strength of the pile head side joint portion of the pile cap, the length of the pile head portion penetrating the foundation slab cannot be evaluated as the penetration depth of the pile at the pile head side joint portion, and only the length of the pile head portion embedded inside the steel pipe portion can be evaluated as the penetration depth of the pile at the pile head side joint portion. Therefore, even when the thickness of the foundation slab is increased, it cannot contribute to an increase in the allowable bending strength at the pile head side joint portion of the pile cap, resulting in an unreasonable design. In view of this situation, the main objective of the present invention is to provide a technology that enables rational design in a foundation structure of a building in which a pile cap having a steel pipe section to which a steel column-beam joint is joined and a concrete section inside it is provided as a foundation footing, and the steel pipe section of the pile cap is installed on a foundation slab constructed along the ground surface, by increasing the thickness of the foundation slab to improve the allowable bending strength of the pile head side joint of the pile cap. [Means for solving the problem]

[0005] The first characteristic configuration of the present invention is a pile cap that is joined to the pile head of a pile embedded in the ground, and comprises a steel pipe section that surrounds the pile head and has a steel column-beam joint joined to its upper end, and a concrete section made of concrete filled inside the steel pipe section. A foundation structure for a building comprising a concrete foundation slab constructed along the ground surface of the aforementioned ground, wherein the steel pipe portion of the pile cap is installed on the foundation slab, The key feature is that the concrete portion of the pile cap is provided with reinforcing main bars, the lower end of which is embedded in the foundation slab and extending along the axis of the steel pipe portion.

[0006] In this configuration, the concrete portion of the pile cap, into which the pile head is embedded and which can bear the bearing pressure on the side of the pile, and the foundation slab, through which the pile head passes and which can bear the bearing pressure on the side of the pile, are integrated by reinforcing main bars provided across them. As a result, the portion of the frictional force generated between the concrete portion of the pile cap and the foundation slab and the side of the pile that is transmitted to the foundation slab is transmitted to the steel pipe portion through the reinforcing main bars. This allows the length of the pile head portion penetrating the foundation slab to be evaluated as the pile insertion depth at the pile head-side joint when calculating the allowable bending strength of the pile cap's pile head-side joint. Accordingly, the present invention provides a foundation footing for a building whose foundation structure includes a pile cap having a steel pipe section to which a steel column-beam joint is joined and a concrete section inside it, and in which the steel pipe section of the pile cap is installed on a foundation slab constructed along the ground surface, the increase in the thickness of the foundation slab contributes to improving the allowable bending strength of the pile head side joint of the pile cap, thereby enabling a rational design.

[0007] A second characteristic feature of the present invention is that hoop reinforcement surrounding the main reinforcing bars is provided in the concrete portion of the pile cap.

[0008] With this configuration, since hoop reinforcement surrounding the main reinforcing bars is provided in the concrete portion of the pile cap, the concrete portion can exhibit excellent shear resistance against the bearing pressure on the side of the pile. [Brief explanation of the drawing]

[0009] [Figure 1] Longitudinal cross-sectional view of the foundation structure of the building according to this embodiment. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described with reference to the drawings. The foundation structure of the building in this embodiment, as shown in Figure 1, includes a pile cap 21 as a foundation footing 20, which is joined to the pile head 15a of a pile 15 embedded in the ground G.

[0011] The pile cap 21 has a steel pipe section 23 that surrounds the pile head 15a of the pile 15 and has a steel column-beam joint 10 joined to its upper end, and a concrete section 24 made of concrete filled inside the steel pipe section 23. The steel column-beam joint 10 has a steel column section 11 that is erected above the pile head 15a, and a steel beam section 12 that is joined to the steel column section 11 and extends laterally through the upper end portion of the steel pipe section 23. These steel pipe sections 23 and steel column-beam joints 10 are pre-assembled into a single unit and then transported to the construction site.

[0012] A reinforced concrete foundation slab 17 is constructed along the ground surface Ga of the ground G. The steel pipe section 23 of the pile cap 21 is then installed on the foundation slab 17, and its upright position is adjusted by height-adjustable adjustment bolts 28 provided at multiple locations on the outer circumference of the lower end of the steel pipe section 23. Next, the gap formed at the lower end of the steel pipe section 23 is sealed with mortar 26 or the like, and then concrete is poured inside the steel pipe section 23 to construct the concrete section 24, thus constructing it as part of the foundation structure.

[0013] Furthermore, at a time such as before concrete is poured into the concrete section 24 inside the steel pipe section 23, another beam member 42 is connected to the tip of the steel beam section 12 via a beam joint 45 using a splice plate and high-strength bolts. These steel beam sections 12 and the connected beam member 42 constitute a foundation beam, on which a slab (not shown) is constructed. In addition, another column member 41 is connected to the upper end of the steel column section 11.

[0014] The steel beam section 12 is made of H-shaped steel with flanges on the top and bottom, and is positioned at a height where its upper end is flush with the upper end of the steel pipe section 23. Furthermore, the steel beam section 12 extends in four directions (up, down, left, and right) from the axis C of the steel pipe section 23 in a roughly cross shape in a plan view. On the other hand, the steel column section 11 is made of steel pipe or H-shaped steel and is joined by welding to the intersection of the steel beam section 12 located inside the steel pipe section 23 in an upward-extending position. In general, the intersection position of the steel beam section 12 and the joining position of the steel column section 11 to the steel beam section 12 inside the steel pipe section 23 can be at the position of the axis C of the steel pipe section 23, but they can also be positioned offset from the axis C as appropriate. Furthermore, although the steel pipe section 23 is made of a circular steel pipe having a circular cross-section in this embodiment, a rectangular steel pipe having a rectangular cross-section or a steel pipe having other cross-sectional shapes can be used.

[0015] In the foundation structure of the building in this embodiment, a feature configuration is employed that allows for a rational design by increasing the thickness of the foundation slab 17, which contributes to improving the allowable bending strength of the pile cap 21's joint on the pile head 15a side. The details of this feature configuration will be explained below.

[0016] The concrete portion 24 of the pile cap 21 is provided with reinforcing main reinforcement bars 30, the lower end portion 30a of which is embedded in the foundation slab 17 and which extend along the axis C of the steel pipe portion 23. These reinforcing main reinforcement bars 30 are arranged at approximately equal intervals at multiple locations around the pile head 15a, and the lower end portion 30a of each reinforcing main reinforcement bar 30 is bent so as to extend horizontally at the lower end inside the foundation slab 17.

[0017] As described above, the reinforcing main bars 30 are provided in the concrete portion 24 of the pile cap 21. This integrates the concrete portion 24 of the pile cap 21, where the pile head 15a is embedded and can bear the bearing pressure on the side of the pile 15, with the foundation slab 17, through which the pile head 15a penetrates and can bear the bearing pressure on the side of the pile 15, through the reinforcing main bars 30. Consequently, the portion of the frictional force generated between the concrete portion 24 of the pile cap 21 and the foundation slab 17 that is transmitted to the foundation slab 17 is transmitted to the steel pipe portion 23 through the reinforcing main bars 30. This allows the length of the pile head 15a portion penetrating the foundation slab 17 to be evaluated as the insertion depth of the pile 15 at the pile head side joint of the pile cap 21 when calculating the allowable bending strength of the pile head side joint of the pile cap 21 (the portion where the pile head 15a is joined to the pile cap 21). Furthermore, the force from the reinforcing main reinforcement 30 to the steel pipe section 23 can be transmitted by the adhesion force between the steel pipe section 23 and the concrete section 24, but a shear key may be provided in the steel pipe section 23 to ensure better force transmission. In this embodiment, reinforcing bars 30 are provided at multiple locations around the pile head 15a, but the locations and number of reinforcing bars 30 can be changed as appropriate.

[0018] In the concrete portion 24 of the pile cap 21, hoop bars 31 surrounding these plurality of main reinforcement bars 30 are provided. These hoop bars 31 are arranged in parallel at substantially equal intervals at a plurality of locations along the axis C from the concrete portion 24 to the foundation slab 17. By providing the hoop bars 31 in the concrete portion 24 of the pile cap 21 in this way, it is possible to exhibit excellent shear resistance against the lateral bearing pressure of the pile 15 borne by the concrete portion 24. In addition, in this embodiment, the hoop bars 31 are provided at a plurality of locations along the axis C, but the installation locations and the number of installed hoop bars 31 can be appropriately changed. Also, the hoop bars 31 can be appropriately omitted.

Explanation of Reference Numerals

[0019] 10 Steel frame column-beam joint 15 Pile 15a Pile head 17 Foundation slab 20 Foundation footing 21 Pile cap 23 Steel pipe portion 24 Concrete portion 30 Main reinforcement bar 30a Lower end portion 31 Hoop bar C Axis G Ground Ga Ground surface

Claims

1. The foundation footing, which is joined to the pile head of a pile embedded in the ground, comprises a pile cap having a steel pipe section that surrounds the pile head and has a steel column-beam joint joined to its upper end, and a concrete section made of concrete filled inside the steel pipe section. A foundation structure for a building comprising a concrete foundation slab constructed along the ground surface of the aforementioned ground, wherein the steel pipe portion of the pile cap is installed on the foundation slab, A foundation structure for a building, wherein the concrete portion of the pile cap is provided with reinforcing main bars that are embedded in the foundation slab at their lower end and extend along the axis of the steel pipe portion.

2. The foundation structure for a building according to claim 1, wherein hoop reinforcement surrounding the main reinforcing bars is provided in the concrete portion of the pile cap.

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