JP4036425B2 - Direct foundation structure such as steel structure building - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a direct foundation structure such as a steel structure building, and more particularly to a foundation for a low-rise steel structure building. And a floor slab that can be integrally formed with a single mat.
[0002]
[Prior art]
A solid foundation type is often used as the foundation of a building. The solid foundation 10 has a large number of beams 12 arranged in a lattice pattern as shown in FIG. 6, and a foundation slab 11 is formed in a portion surrounded by each beam. It looks like a single mat is laid and a reinforcing beam is placed on it.
[0003]
This type of foundation is suitable as the foundation of a heavy building such as RC (reinforced concrete) five-story building. The load received from the pillar 3 is supported by the lattice beam 12, and the reaction force from the ground 6 is the foundation slab 11. It has a balance structure of receiving power. Therefore, the beam 12 is finely and evenly arranged between the columns 3 and 3 as shown in FIG.
[0004]
More specifically, a floor slab 13 having a thickness of about 150 millimeters as shown in FIG. This forms the floor surface 13f of the first floor, but if the area 12A surrounded by the lattice 12 is left as a space, the lattice beam 12 receiving the weight of the floor transmits the force to the foundation slab 11. In the case of backfilling, the weight of the floor is directly transmitted to the foundation slab 11. In any case, the foundation slab transmits a vertical load to the ground over a wide area, but the floor slab 13 does not have a function of transmitting the load entering from the column to the ground.
[0005]
Such a solid foundation is often applied to RC construction and SRC construction. Therefore, assuming that hundreds of tons of load is applied to the entire surface, the foundation slab is considerably thickened. However, since it does not protrude around the building, there is no possibility that the foundation 10 interferes with the outer groove 14 as shown in FIG. There are advantages. This is the same when there is an adjacent land boundary.
[0006]
By the way, in the case of a steel structure (S structure) building, for example, a load of about 20 tons acts on one pillar in the case of two stories, and about five tons in the case of one story. When a solid foundation having the above-described structure is used for a foundation of a building that only applies such a load, even if each of the floor slab, the foundation slab, and the foundation beam is considerably reduced, an excessive sense of quality cannot be avoided.
[0007]
However, if a known independent footing foundation or continuous footing foundation is employed when the beam span or pitch of the building is large, a strong and rigid foundation is required. For example, in the case of an independent footing foundation, the footing must be thickened or extended, and a foundation beam (underground beam) needs to be arranged between adjacent footings. In addition, the same applies to the case of continuous footing foundations (fabric foundations), but if the footing extends from the building and there is an outer groove or the boundary of the adjacent land must be taken into account, the compatibility will be significantly reduced. That's what it means.
[0008]
[Problems to be solved by the invention]
Under such circumstances, the basic structure shown in FIG. 8 is proposed in Japanese Patent Laid-Open No. 9-279741. This is an improvement on the premise of the basic structure of FIG.
[0009]
First, in the solid foundation shown in FIG. 10, a foundation beam 15 is arranged in a portion where the columns 3 are arranged, a foundation slab 11 is provided in a space surrounded by the foundation beam, and a floor slab 13 is formed thereon. It is. In the construction in this case, first, the reinforcing bar frame 15a of the foundation beam and the reinforcing bar 11a of the foundation slab are assembled, and the concrete 11b is placed in the portion that becomes the foundation slab. After the hardening, the concrete 15b is placed on the portion to be the foundation beam, and after the hardening, the reinforcing bars 13a of the floor slab are assembled and the concrete 13b is placed thereon.
[0010]
In such work, even if the discarded concrete 7 is removed, the concrete must be cast three times. In placing, it goes without saying that a form installation work, a concrete placement work, a concrete hardening and curing process are necessary, and the process proceeds to the next place after finishing a series of processes. Considering that it usually takes nearly a month for each, it is inevitable that the construction period will be prolonged if it is repeated three times. Of course, the rebar assembling work prior to placing is not lightly burdened. The structure shown in FIG. 8 has been proposed to improve this.
[0011]
When the width of the foundation beam 15 in FIG. 10 is 400 mm, the thickness of the foundation slab 11 is 250 mm, and the floor slab 13 is 150 mm, the foundation beam 15 is laid sideways as shown in FIG. If the space 17 (refer FIG. 10) between the foundation slab 11 and the floor slab 13 is eliminated also as the foundation beam 16 made, the thickness of the floor slab 13 and the foundation slab 11 can be ensured as it is. At the same time, it is based on the idea that the upper surface 13u of the floor slab 13 can also coincide with the upper surface 16u of the foundation beam 16.
[0012]
If it does in this way, the foundation slab 11 and the floor slab 13 will become one, and will become one superposition slab 18. This not only forms the floor or soil, but also has the ability to transmit the load entering from the pillars and floor to the ground.
[0013]
Since this overlap slab does not need to reveal the boundary with the foundation beam, simply installing a formwork (not shown) that defines the perimeter of the foundation, a series of concrete placement of the foundation beam and the overlap slab There are advantages that can be built with. Further, as a result of laying the foundation beam on its side, the foundation becomes thinner and the total excavation has to be carried out, but the root cutting can be made shallower than in the case of FIG.
[0014]
If this structure is represented three-dimensionally, the foundation beam 16 exists under the column 1c as shown in FIG. In this case, the load from the column 3 is transmitted from the superposed slab 18 to the ground 6 through the foundation beam 16, and bending due to the ground reaction force acting on the superposed slab is countered by the foundation beam 16. However, for the sake of calculation, if the basic beam is regarded as a one-dimensionally extending member and the propagation of force to the superimposed slab is ignored, the introduction of complicated structural analysis and advanced calculation methods can be avoided. There are advantages.
[0015]
However, the superposed slab 18 is reinforced by the surface lattice 18a as can be seen from FIG. 8A, and as shown in FIG. 8B, the respective foundation beams 16 ₁ and 16 ₂ intersecting each other. In addition, the reinforcing bar frame 16a surrounded by the hoop bars 16a ₁ is required. In other words, this type of solid foundation still has a complicated structure for assembling reinforcing bars, and it is far from eliminating or reducing the rebar assembling and arranging work that require a lot of labor.
[0016]
In addition, if such a solid foundation is applied to a lightweight S building, when the beam span and pitch of the building are large, the foundation beam where the load is concentrated needs to have durable strength and rigidity. As a result, the height of the foundation beam corresponding to it (400 mm in the above example) must be ensured. In this case, even if it is known that the thickness of the superimposed slab becomes excessive, there is also a problem that it is necessary to fill with concrete up to the height of the foundation beam.
[0017]
The present invention has been made in view of the above-described problems. The purpose of the present invention is to reduce the amount of excavation by thinning the foundation even when the column spacing is relatively large in an S structure which is a relatively light building. By providing a direct foundation structure such as a steel building that achieves reduction, reduction of concrete formwork assembly work, simplification of rebar assembly structure, reduction of concrete placement, shortening of construction period by avoiding repeated curing, etc. is there.
[0018]
[Means for Solving the Problems]
The present invention is applied to a mat-type foundation structure which is a low-rise steel structure building of up to about 2 or 3 stories and is installed to spread over the entire bottom surface of the building. 1 (a) and 2 (a), the foundation structure is not provided with a reinforcing beam protruding upward or a foundation beam forming a peripheral portion, but only a foundation slab. The upper surface 1a is positioned above the ground GL so as to exhibit the function of a floor slab, and is formed of a single mat 1 reinforced by reinforcing bars 4 assembled in a grid pattern on a plane. The steel column 3 is directly attached to the mat 1, and the periphery 1b of the steel column (see FIG. 2A) or the column row portion 1c (see FIG. 5) protrudes downward. The flat grid-like reinforcing bars 4 are provided with two stages (reinforcement 4U, 4L) in the upper layer portion and the lower layer portion in the column periphery 1b or the column array portion 1c, and in other portions, the upper layer portion A separate one-stage (reinforcement 4M) independent of each of the upper and lower plane grids is applied to the middle layer below the plane grid. The stress generated on the foundation is countered by the single mat 1 spreading as a surface, while the vertical load can be transmitted to the ground 6 via the mat surface.
[0019]
【The invention's effect】
According to the present invention, the foundation slab and the floor slab are formed by a single mat that is integrated vertically, so that the load from the column is also transmitted to the upper part of the mat corresponding to the floor slab. The burden on the lower part of the mat corresponding to is reduced.
[0020]
Even if the stress generated in the foundation around the column base increases due to the large span and pitch of the beams used in the building, it is burdened by propagating to the mat that spreads as a surface reinforced by reinforcing bars stretched in all directions. Is distributed. Excessive concentration at locations where mechanical balance should be achieved is eliminated, and the strength and rigidity imparted to the mat can be reduced.
[0021]
In other words, there is no high-strength and high-rigidity foundation beam as described in the section of the prior art, so a thick mat corresponding to that is not required, and the foundation structure can be further thinned. Reinforcement with reinforcing bars can be done in the form of a plane lattice, which greatly simplifies the rebar assembly work. In some cases, even a slightly soft ground can be applied, and ground reinforcement work can be reduced.
[0022]
Needless to say, the amount of excavation at the time of root cutting is significantly reduced by thinning the mat, and excavation and backfilling operations can be suppressed to a small scale. The foundation consisting of a single mat greatly contributes to the reduction of construction period and cost, such as simplification of formwork and bar arrangement work, minimum number of concrete placements, and shortening of the curing period.
[0023]
Since the mat thickness is locally increased by projecting the column periphery or column row part downward, not only can the proof strength be increased at that part, but also the concrete placement amount at other parts can be greatly increased. You can save.
[0024]
The upper and lower layers of the mat are arranged in two layers in the upper and lower layers of the mat around the columns and column rows, and the upper and lower layers are located in the middle layer that is below the plane lattice of the upper layer at locations other than the columns and column columns. Since a separate one-stage bar arrangement independent of each of the plane grids of the above is provided, it is possible to obtain a sufficient thin mat reinforcement while avoiding partial excessive reinforcement and saving the bar arrangement material.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Below, direct foundation structures, such as a steel frame building concerning the present invention, are explained in detail based on a drawing showing the embodiment. FIG. 1 is a perspective view of a foundation structure formed of a single mat 1 in which parts corresponding to the foundation slab and floor slab described in the section of the prior art are integrated vertically.
[0026]
This is suitable for low-rise steel buildings with a relatively large span L _S and pitch L _{P of} the beam 2 up to about 2 or 3 stories as shown in FIG. It is provided to spread throughout.
[0027]
As shown in FIG. 2 (a), the foundation structure 1 has a single mat shape in which the upper surface 1a is located above the ground GL so that it can function not only as a foundation slab but also as a floor slab. Is formed.
[0028]
Such a mat 1 is not provided with a reinforcing beam 12 as shown in FIG. 6 or a foundation beam 16 (see FIG. 9) as shown in FIG. Moreover, it is a single mat reinforced by a large number of reinforcing bars 4a, 4a which are flat and assembled in a lattice pattern.
[0029]
As shown in FIG. 2 (a), the steel column 3 is directly attached to the mat 1 with an anchor bolt 5 or the like, and the stress generated in the foundation is countered by a single mat spreading as a surface, while the vertical load is It is transmitted to the ground 6 through the mat surface. As can be seen from FIG. 1, the base structure 1 has a column 1b protruding downward, and the mat thickness is locally large at that portion, but the other portions are thin overall, generally forming a single board. is doing.
[0030]
In order to reinforce such a mat, the upper layer portion and the lower layer portion of the entire surface are each provided with a single step, that is, two steps of reinforcing bars 4U and 4L in total (see FIG. 2A). . Since the mat does not include beams, it is not necessary to incorporate a rebar frame using hoop bars. For example, 13 mm diameter rebar bars 4a and 4a are connected sequentially by binding wires to form a large number of lattices. Is sufficient. By the way, the end of each step is folded down or up, and the bar arrangement is integrated by tying it down, etc., but the other part is simply a large number of lattices spreading as a plane .
[0031]
In the case of an S structure (steel structure) building, especially in the case of a factory or warehouse building, or a simple office building, the span of the beam is generally increased in order to secure a large space, unlike a general residential house. Of course, the beam pitch is often increased, but the normal pitch is selected to be shorter than the span (see FIG. 4).
[0032]
As described in the section of the prior art, since the S structure is lighter than the RC structure or the SRC structure, the load on the foundation is small. However, when the span and pitch of the beam are large, the foundation is subjected to a large bending due to the load entered from the column although it is lightweight in the conventional foundation structure. However, in the present invention, the stress (mainly bending stress, shear stress, etc.) generated in the foundation by integrating the foundation slab and the floor slab is also applied to the portion corresponding to the floor slab, so that I try to suppress the thickening.
[0033]
On the other hand, from the viewpoint of construction, the floor slab and the foundation slab are formed as a single mat at the same time. Therefore, compared to the case where the foundation slab and the floor slab are separately constructed, it is more effective for placing concrete and curing. The required time is halved and the construction period is greatly shortened. Since there are no beams, the assembly work of the reinforcing bars 4 (see FIG. 2) becomes simple, and the simplification of the entire construction progresses rapidly.
[0034]
Since the foundation structure does not include foundation beams that are regarded as wires for calculation, it is indispensable to design a flat mat that pursues three-dimensional deformation and two-dimensional propagation of stress. As a result of the dispersion of the load acting on the ground as described above, the stress level (ground pressure) of the ground is also reduced. Therefore, it can be applied to soft ground where it is not easy to install independent footing foundations or continuous footing foundations, or it can be started without any significant ground improvement, and the scope of application of the foundation structure according to the present invention is extremely wide. Become.
[0035]
As can be seen from the above description, this foundation structure does not have a foundation beam, but is a mat that integrates a foundation slab and a floor slab, so the thickness is determined regardless of the dimensions required for the foundation beam. be able to. Since the load is distributed in the mat, a mat thinner than the thickness required for the foundation beam is realized. For example, the thickness around the pillar 1b (see FIG. 2A) can be designed to be 250 millimeters, and the rest is 150 millimeters.
[0036]
In order to function as a floor slab as well as making the mat thinner, the upper surface is made 50 mm higher than the ground, so even if it includes the laying cost of crushed stone 7 and the placing cost of throwing away kon 8 The amount of excavation when cutting is significantly reduced. Therefore, the backfilling work is greatly reduced, and the labor and cost required for the residual soil treatment can be reduced. As shown in FIG. 8, the consumption of mortar for level adjustment of the floor surface is not necessary, and the amount of placing concrete is reduced as a whole, and the construction material is greatly reduced.
[0037]
Incidentally, in FIG. 1, only the periphery of the column is thicker than the others, but if there are parts where several columns are arranged in a straight line, the stress generated on the foundation by increasing the thickness of the column array as in the case of the columns, although not shown. It is better to use a mat with a structure that is easier to counter.
[0038]
FIG. 3A shows an example in which the upper layer portion and the lower layer portion of the entire surface of the mat 1 are provided with one step of reinforcing bars 4U and 4L. In each step, the density around the column 1b is, for example, a quadruple density. And that part will be strengthened. Further, at the location 1c that becomes the column, it is also possible to arrange reinforcement with double the density along the edge as shown on the left side in the drawing. Incidentally, the throwing-out container 8 may be provided on the entire surface, but there may be a case where only the periphery of the pillar may be provided as shown in FIG. 2A, or it may not be required at all.
[0039]
FIG. 4 is an example of the basic structure 1A when the entire mat has the same thickness. Also in this case, as shown in FIG. 2 (b), two stages of reinforcing bars 4U and 4L are applied in the upper and lower layers. Thus, if the entire mat has the same thickness, ground excavation and bar arrangement become extremely simple, and workability is improved. As shown in FIG. 3 (b), it is also possible to keep the arrangement of the reinforcing bars only in the column periphery 1b.
[0040]
By the way, depending on the distribution of various stresses generated in the foundation, it is possible to arrange 4M bars (see the one-dot chain line in FIG. 5) with only one step in the middle layer at locations far from the column, and two steps on the entire surface. Reinforcing bars are consumed less than reinforcing, and excessive reinforcement can be avoided. In any case, since the surface lattice is stretched in the mat, the stress in the foundation easily propagates to the entire mat.
[0041]
The concrete can be placed once except for the throwing away container 8, and the formwork assembled at that time is only around the mat. Preparatory work required for placing is simplified. Curing after placement is only required once, and the burden on the worker, including the work to disassemble the formwork, is greatly reduced. Needless to say, the construction period can be shortened.
[0042]
8 (a) and 8 (b) listed as the prior art is designed to counter most of the stress generated in the foundation with the foundation beam incorporating the reinforcing bar frame. There is no idea of causing the superimposed slab 18 constituting the slab to bear even bending stress. In addition, since the foundation beams that are directly subjected to the force from the columns are reinforced intensively, the dispersion of the force is also hindered.
[0043]
On the other hand, generally speaking, the present invention avoids concentration by absorbing the stress generated in the mat over the entire surface of the mat, and in this respect, the structure is very contrasting with FIG. The present invention promotes the dispersion of stress and intends to further reduce the thickness of the foundation. As shown in FIG. 2, the light steel structure foundation generally adopts a pin support type in which a column base is fixed by an anchor bolt 5 via a support plate. May be applied, and may be selected as appropriate in consideration of other design factors.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of a basic structure according to the present invention.
FIGS. 2A and 2B are cross-sectional views of a basic structure, and FIGS. 2A and 2B are enlarged views around a column.
FIG. 3 is a perspective view showing a bar arrangement form of a basic structure, in which (a) and (b) are both vertically aligned to form two steps on the entire surface.
FIG. 4 is a perspective view of an example of a mat having a substantially constant thickness and a steel building built on the mat.
FIG. 5 is a perspective view of a bar arrangement that is one-tiered around the pillars and at places other than the pillar row portions.
FIG. 6 is a perspective view of a known solid foundation.
7 is a cross-sectional view taken along line VII-VII in FIG.
8 is a slab according to the prior art in which a foundation beam and a superposed slab are integrated, in which (a) is a cross-sectional view taken along line VIII-VIII in FIG. 9, and (b) is a cross-sectional view taken along line IX-IX. Figure.
FIG. 9 is a perspective view showing a framework of a slab in the prior art in which a foundation beam and a superimposed slab are integrated.
FIG. 10 is a cross-sectional view of the foundation structure before that, which is the basis for devising the foundation structure of FIG. 8;
[Explanation of symbols]
1 ... mat (substructure), 1a ... top, 1b ... pillar around, 1c ... Hashiraretsu portion, 2 ... beams, 3 ... steel column, 4U, 4L, 4M ... reinforcement, L _S ... beam span, L _P ... Pitch of beams, GL ... Ground.

Claims (1)

It is a low-rise steel structure building of up to about 2 or 3 stories, and it is spread over the entire bottom of the building.
The above-mentioned foundation structure is not provided with a reinforcing beam protruding upward or a foundation beam forming a peripheral portion, etc., and the upper surface is located above the ground so that it functions not only as a foundation slab but also as a floor slab. Formed with a single mat that is reinforced by reinforcing bars assembled in a grid pattern
Steel mats are directly attached to the mat, and the periphery of the steel column or the column row part protrudes downward, and the rest is thin overall.
The planar grid-like reinforcing bars are provided with a total of two steps on the upper layer portion and the lower layer portion around the column or in the column row portion, and the upper layer portion on the middle layer portion that is lower than the planar lattice of the upper layer portion in other portions. And one separate step independent from each plane lattice of the lower layer,
A direct foundation structure such as a steel-frame building, in which the stress generated in the foundation is countered by a single mat that spreads as a surface, while the vertical load can be transmitted to the ground via the mat surface.

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