JP2002115363A - Floor structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a floor structure capable of increasing a soundproof performance while maintaining a framed construction formed of metal sectional frame materials and beams materials. SOLUTION: Granular materials 13 such as reducing pellets are sealed in the space part 11 of a metal sectional beam material 3 to form a framework comprising frame materials and the beam materials 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a floor structure having a frame composed of a metal frame and a metal beam spanned inside the frame. About things.

[0002]

2. Description of the Related Art In recent years, in the construction of houses by the conventional construction method, a floor structure in which a floor plate is joined to a frame made of metal frame members and beams is adopted instead of a floor structure in which a floor plate is joined to a timber frame. It has come to be. Since a frame made of a metal frame and a beam is used, the earthquake resistance and the durability are excellent.

[0003] In particular, when a thin profile having a thickness of 1 to 3 mm is used for the frame member and the beam member, tapping or nailing at the site can be performed, and the same construction as the conventional construction method can be performed.

When such a floor structure having a frame made of a metal frame and a beam is used as a floor at the boundary between the upper and lower floors of an apartment house, it is lightweight and simple, but has a high weight and rigidity. Noise reduction measures are required.
In particular, by simulating the jumping or walking of a person, the magnitude of the impact sound (hereinafter referred to as “heavy floor impact sound”) and the floor vibration generated downstairs when the tire is dropped directly on the floor is measured. ,
It is necessary to take measures against impacts caused by walking on the floor.

[0005] As a method of reducing the heavy floor impact sound,
(1) A method of increasing the weight of the floor structure, and (2) a method of increasing the bending rigidity of the floor structure. In addition, (1) (2)
There is also a method of increasing the impedance corresponding to the multiplication of. Furthermore, the floor vibration after the impact force is attenuated quickly,
As a method of suppressing discomfort, there is also a method of (3) imparting vibration damping properties to the floor. With the provision of the vibration damping property, suppression of a medium-high frequency sound, that is, a metal sound, which is generated in a structure using a lot of metal, is realized.

[0006]

As a method of increasing the weight of the floor structure of (1), there is a method of increasing the weight of a floor plate having a heavy weight such as a cement plate on a frame made of a metal frame and a beam. There is a method of mounting a plurality of sheets in a stacked state. However, when a heavy floorboard is placed, the result is contrary to the original purpose of forming a floor structure easily and lightly by using a metal frame.

As a method (2) for increasing the rigidity of the floor structure, there is a method of increasing the bending rigidity of a component such as a frame member or a beam made of a metal profile. Specifically, this is achieved by increasing the second moment of area by increasing the cross-sectional dimension, the number, and the thickness of the floorboard, or by configuring these members with a material having a high elastic modulus. However, the increase in the number and the number of the frame members, beams, and floorboards increases the weight and occupied volume, and the number of parts increases the material and construction costs. Also,
As a method of (3), there is a method of attaching a vibration damping material to a floor plate or a beam material.
(Less than 00 Hz), a great effect cannot be obtained.
In order to realize the above (1) and (3), instead of a heavy floor plate, sand-like grains are filled in a plurality of hollow portions inside a molded cement panel as disclosed in Japanese Patent Application Laid-Open No. 10-205043. In order to realize the above-mentioned sound insulation floor and the above-mentioned (3), as disclosed in Japanese Patent Application Laid-Open No. H11-217891, a large number of cell spaces (honeycomb cores) are formed between two opposing sheets. Although it is conceivable to use a vibration-damping panel in which elastic particles are enclosed as a floorboard, the use of a thick floorboard with a complicated structure results in an increase in occupied volume and an increase in construction cost.

Therefore, as a method of reducing the heavy floor impact noise while maintaining the frame made of a metal profile, a method of arranging weights intensively particularly in a portion where vibration is large, and a method of lowering floor noise at a low frequency of, for example, 100 Hz or less. A method of arranging a dynamic vibration absorber (or a dynamic damper: a vibration system composed of a weight and a spring) capable of effectively imparting a vibration damping property can be considered. Floor structure is 20-30k with metal frame
When the floor is vibrated due to an exciting force due to walking or the like acting on the floor when the weight is reduced to about g / m ^{2, the} force is transmitted to the wall and vibrates because the floor is sandwiched between the outer walls. The inertial mass adds to the inertial mass of the floor, and the equivalent mass at the position where the floor vibrates the most is as large as 100 to 300 kg. for that reason,
For example, in order to lower the weight by 3 dB with a heavy floor impact sound using a weight for reducing the floor impact sound, the equivalent mass is doubled to 600 k.
g, so a 300 kg weight is required. Furthermore, since the vibration damping effect of the dynamic vibration absorber increases as the weight of the weight constituting the dynamic vibration absorber increases, a weight for reducing the floor impact sound is added, and the dynamic vibration absorber to the heavier floor is used. In order to provide a vibration damping effect, it is necessary to make the weight of the dynamic vibration absorber heavy, and as a result, the floor weight increases, and the characteristics of the floor structure being lightweight and simple are impaired. Also, since the natural frequency of the dynamic vibration absorber needs to be very close to the natural frequency of the floor structure, the natural frequency of the floor structure where the dynamic vibration absorber is installed is measured for each case, or In practice, it is very difficult to predict the natural frequency by performing a numerical analysis on various floor structures.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a floor structure capable of improving soundproofing performance while maintaining a framed structure made of a metal frame or beam.

[0010]

According to a first aspect of the present invention, there is provided a floor structure comprising: a metal frame; and a metal beam spanning the inside of the frame. Wherein all or a part of the beam material has a hollow portion, and a granular material is accommodated in the hollow portion.
According to the configuration of the first aspect, when the granular material is accommodated in the hollow portion of the beam, the weight can be increased while maintaining the outer shape of the framework of the frame and the beam. In addition, since the floor vibration after the impact force appears largely at the antinode of the beam material, the effect of reducing the heavy floor impact sound by increasing the weight of the beam material is effectively exhibited. In addition, the granular material jumps in the hollow portion due to vibration, so that a vibration damping effect on the floor is exhibited.

[0011] For example, a steel sheet having a thickness of 1 to 3 mm
Used as beam material, wood like structural plywood as floorboard
When used, the mass of the floor structure is 20-30 kg / m^TwoDegree and
And lighter. However, the floorboards that make up the floor structure
When an impact force is applied, the frame material, beam material, and floorboard are integrated
A wall that starts to vibrate and secures the perimeter of the floor structure
Because the surface also vibrates, the position where the floor structure vibrates most
Thus, the equivalent mass becomes 100 kg to 300 kg. There
Then, the granular material is housed in the hollow part of the beam, and the weight of the frame is reduced.
Let it up. For example, 10 / m
The size of the room is 3.64m ×
In the case of 3.64m between 8 tatami mats, it is 36kg per beam.
When beams are installed at intervals of 455 mm, seven beams
Thus, the total weight of the granules becomes 288 kg. At this time,
Equivalent mass m after storing granular material₁Is at least before installation m₀of
It is approximately 588 kg, which is twice as large, and the weight floor impact noise is 10
log (m₁/ M ₀) = 3 dB reduction
You. Also, when vibration exceeding the gravitational acceleration occurs,
The body jumps inside the hollow, repeatedly hits, and shakes the floor.
The impact force is applied in the direction to suppress, so the vibration damping effect on the floor
Be demonstrated.

A floor structure according to a second aspect is the floor structure according to the first aspect, wherein an elastic body or a viscoelastic body is interposed in all or a part between the inner wall of the hollow portion and the granular body. According to this configuration, for example, when the beam is made of a shaped steel, the granular material repeats collision in the hollow portion of the beam, giving an impact force to the shaped steel, and the impact sound is secondarily generated from the shaped steel. Is generated, since the elastic body or the viscoelastic body is interposed between the granular body and the inner wall of the hollow portion, the generation of the secondary impact noise is prevented.

According to a third aspect of the present invention, in the floor structure according to the second aspect, the elastic body or the viscoelastic body is a bag housed in the hollow portion. According to the configuration of the third aspect, for example, the granular material is put in the cylindrical bag, and the bag is simply put in the hollow portion of the shape, and the elastic body or the viscoelasticity is formed between the granular material and the inner wall of the hollow portion. It is a structure that intervenes the body.

The floor structure according to the fourth aspect is the floor structure according to the first to third aspects.
In any one of the above, the granular material is a reduced pellet. According to the configuration of claim 4, since the reduced pellets are made of iron ore, the specific gravity is large due to the high content of iron,
The shape is uniform, the granular material easily jumps, and even if the granular material repeatedly collides in the hollow portion, the granular material is hardly worn or crushed, and exhibits a vibration control function stably. In addition, since it has been fired, there is little moisture, and there is no fear of mold and bacteria growing after being incorporated into a house. In addition, stable supply is possible, and large quantities can be obtained at low cost.

[0015] The floor structure according to the fifth aspect is characterized by the following:
In any one of the above, the beam material is formed by combining groove-shaped cross-section members so that the hollow portion becomes a closed space. According to the structure of the fifth aspect, by forming the groove-shaped cross-section in combination, the closed space can be easily formed, and the cross-section modulus of the beam increases. For example, a hollow portion is formed by fitting two grooved steel bars formed from a thin steel plate by roll forming with the concave portions facing each other.

[0016] The floor structure according to the sixth aspect is the first to fifth aspects.
In any one of the above, a floor plate is joined to upper surfaces of the frame material and the beam material. According to the configuration of claim 6, since the frame is of a soundproof structure, a floor surface can be formed on the frame by on-site construction or the like using wood such as structural plywood.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a top view showing a framework of a floor structure according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a cross-sectional structure of the beam member of FIG.

In FIG. 1, 1 is a floor structure, 2 is a frame material, 3
Is a beam, and 4 is a floor plate. The frame material 2 is composed of two end joists 2a
And two side joists 2b are assembled into a rectangle. The end joist 2a and the side joist 2b have, for example, a width of 40 m.
A channel-shaped steel thin-walled material of mx height 235 mm x plate thickness 1.2 mm is used.

The beam member 3 is formed of a joist that is stretched between the end joists 2a in parallel with the side joists 2b at substantially equal intervals, and a thin steel bar is used. The beam 3 is joined to the frame 2 by fitting both ends of the beam 3 into the groove of the end joist 2a and tapping the flanges formed at the both ends to the bottom of the groove of the end joist 2a. The frame 5 of the floor structure 1 is formed by the frame 2 and the beam 3. On top of this skeleton 5,
The floor plate 4 is placed, and the floor plate 4 is joined to the skeleton 5 with the nail 21 or the like, whereby the floor structure 1 is formed. This floor panel 4 is usually joined to the frame 5 at the construction site, but a set including the frame 5 and the floor panel 4 may be produced in a factory and transported to the construction site.

As shown in FIG. 2, the beam member 3 is provided with a roll-formed grooved steel second thin wall shape in a groove of a roll-formed grooved steel first thin wall member 3a. The material 3b is fitted so that the grooves face each other to form a hollow portion 11 closed inside. The ends of the ribs of the first thin section 3a are straight, but the ends of the ribs of the second thin section 3b are folded inward so that the hollow portion 11 is formed by fitting. For example, width 40 mm x height 2
Using the shape members 3a and 3b of 35 mm x thickness of 1.0 mm,
The beam 3 is formed.

An elastic bag 12 whose inner and outer surfaces are coated with rubber is inserted into the hollow portion 11, and the inside of the bag 12 is filled with a granular material 13. Therefore, an elastic or viscoelastic bag 12 is interposed between the granular body 13 and the inner walls of the profiles 3a and 3b.

FIG. 3 shows a cross section of a beam 103 of another embodiment. A hollow section steel is formed from a single plate by roll forming and bonding such as caulking, and a granular body 113 is accommodated in a hollow portion 111 inside the hollow section steel. The joint portion of the beam member 103 is overlapped on the floor plate 104 and is joined by a tap screw 122. Although not shown, it is preferable to apply an elastic body or a viscoelastic body to the inner wall of the hollow portion 111.

FIG. 3 shows a cross section of a beam 203 of another embodiment. Groove opening 2 by roll forming
03a forming a flange 203b on both sides
The floorboard 204 made of plywood is placed on the flange 203b, and the two are joined by the nail 221. Beam 203
The inside closed hollow portion 211 is formed in cooperation with the floor plate 204. In this hollow portion 211, the granular material 213 is placed.
Is accommodated. Although not shown, it is preferable that the granular material 213 be housed in the hollow portion 211 in a state of being contained in an elastic or viscoelastic body bag.

The granular materials 13, 113, 213 accommodated in the beam members 3, 103, 203 satisfy conditions to some extent that they are heavy, inexpensive, uniform in shape, and do not change over time. Anything can be used. Among them, reduced iron pellets, slags (for example, blast furnace slow cooling slag, blast furnace granulated slag, converter slag, electric furnace slag, etc.), reduced pellets, tap iron, sintered steel, Cold pellets (iron powder, dust, flash ash, etc. solidified into pellets by cement) or the like are preferable as the granular material 13. In particular, reduced pellets are available inexpensively and have the same grain size.
It is particularly preferable because it has a low water content and a high specific gravity because it is fired.

The degree of filling of the granules 13, 113, 213 contained in the beam members 3, 103, 203 depends on the degree of the
If it is possible for 3,113,213 to collide with the flow, it can be allowed from a state of being almost full to a state of being in a space above. When gaining weight, the granules 13, 113, 213 in the hollow portions 11, 111, 211 can be substantially filled to such an extent that collision can be repeated.

With respect to three types of granular materials, ie, converter slag, granulated blast furnace slag, and reduced pellets, the particle size,
The relationship between the filling amount and the dynamic mass was determined, and the type and particle size of the granular material to be enclosed in the joist steel with a box cross-section and the determinants of the filling amount were investigated so that the ratio of the dynamic mass to the filling amount was maximized. Various granular materials were sealed in a box section joist steel cut to a length of 220 mm, attached to a vibrator of 30 kgf via an impedance head, and subjected to sine wave sweeping vibration to generate a vibration force and vibration. From the point vibration acceleration, a transfer function was obtained using FFT, thereby obtaining a moving mass in a frequency region of interest. As a result, no large difference in dynamic mass depending on the type of granular material was observed. Therefore, it is preferable to use cheaper reduced pellets having a uniform particle size. Although the particle size of converter slag is widely distributed from φ5 mm or less to φ22 mm or more, the difference in the damping effect due to the particle size is 31.5 Hz band (22.4 to 44.7 Hz).
As a result, when the diameter was smaller than φ5 mm, the vibration damping effect was almost the same at other particle diameters.

FIG. 5 shows that the reduced pellets are used as the granular material, and the filled amount is almost full, 3.95 kg, the filled amount is slightly 3.3 kg, and the filled amount is 2.2 kg. The relationship between the excitation acceleration and the moving mass in the case of is shown. According to this, the dynamic mass that is a measure of the damping effect is
It tends to be proportional to the excitation acceleration and not dependent on the filling amount. For example, due to the fall of a tire used as a vibration source in a weight floor impact test, the upper part jumps and exerts a vibration damping effect regardless of the filling amount of the granular material, and the remaining part does not jump,
Acts as a weight for reducing heavy floor impact noise. Therefore, the filling amount may be determined from the weight required to reduce the heavy floor impact sound.

The elastic body or viscoelastic body interposed between the inner walls of the hollow portions 11, 111, 211 and the granules 13, 113, 213 is arranged by sticking to the inner wall or inserting a bag-like cylindrical body. Is established. Various types of elastic or viscoelastic materials are used as long as they exhibit elasticity or viscoelasticity, such as those obtained by coating the surface of a core fiber with resin or rubber, resin sheets, rubber sheets, and thick fabrics. it can.

As examples of the elastic body or the viscoelastic body, an available rubber bag and a thick drainage hose were used. A rubber or hose is filled with 2.2 kg of reduced pellets, sealed in a beam, and the radiated noise when the beam is excited by a vibrator is measured by installing a sound level meter at a point 10 mm from the jig surface. did. FIG. 6 shows the result. The radiation noise level of both the rubber bag and the drainage hood is lower than in the case where no rubber bag is provided, but the radiated sound of the drainage hose is slightly smaller than that of the rubber bag. In addition, the measurement was made using a welded fabric coated with a core fiber + surface resin, a fabric coated with a core fiber + surface rubber-based material, a rubber sheet, and a bag made of air-permeable woven fabric without surface coating. Also showed a similar decrease in radiation noise, and could be used as an elastic body or a viscoelastic body.

According to the above experimental results, the elastic modulus of the elastic body or the viscoelastic body is from 1 * 10 ⁶ (Pa) to 1 * 10 ⁶
A polymer material of ⁹ (Pa) is preferable. Also,
Preferably, the elastic body or the viscoelastic body is a foam material. Further, it is preferable that the viscoelastic body is made of a polymer material having a loss coefficient of 0.05 to 5.0. Further, it is preferable that a tubular bag structure is formed using an elastic body or a viscoelastic body, and a granular material is sealed in the bag structure. In addition, it is preferable that the tubular bag structures are arranged in the longitudinal direction and arranged in the tubular hollow portion. In addition, it is preferable that the tubular bag structures are arranged in the height direction of the floor structure and installed in the hollow portion.

Next, the measurement results of the floor impact sound of the floor structure described above will be described below. FIG. 7 shows 3.64 m × 3.64.
The vibration mode of the floor structure which installed seven beam members at intervals of 455 mm in the frame material for 8 tatami mats of m is illustrated. Third-order mode included in 63 Hz octave band (44.7-89.1 Hz) that determines sound insulation performance of heavy floor impact sound,
In each of the next mode and the fifth mode, the amplitude is large at the beam material. Therefore, the non-jumping part of the granular material charged in the hollow part inside the beam material works effectively as a weight effect to reduce the heavy floor impact sound, and the jumping part is as a vibration damping effect on the floor. It turns out that it works effectively. Although the granular material may be charged on the entire surface of the flooring material, the granular material only partially operates, resulting in poor efficiency. In particular, even if the granular material is not charged in all the beam materials, if the granular material is charged in the beam material serving as the antinode of the vibration, the granular material works effectively.

As the floor structure of the present invention, 3.64 m × 3.
Figure 7 shows the weight floor impact sound level of a beam in which seven hollow beams are installed at intervals of 455 mm in a frame material for 8 tatami mats of 64 m, and 36 kg of reduced pellets are charged per beam. 8, the light floor impact sound level is shown in FIG. 9, and the vibration level during hammer impact vibration (floor amplitude per unit excitation force) is shown in FIG. 8 and 10,
For comparison, data of a floor (1) using a heavy concrete floor and data of a floor (2) in which a weight is installed on a beam and a dynamic damper is installed are also shown.
Both floor (1) and floor (2) are JIS (A)
Clear 1418 LH65 class.

In the heavy floor impact sound grade shown in FIG. 8, the one in which the granular material is encapsulated has the same level as the floor (1) and the floor (2) and can be used practically. In the case of the lightweight floor impact sound grade shown in FIG. 10, the use of the soundproof flooring in the case of the granular material enclosure example is reduced to a practically usable level. According to the vibration level at the time of hammer strike excitation in FIG. 9, compared with the basic floor without any treatment, 1
Vibration of about 0 decibels is reduced, and a vibration damping effect equivalent to that of the floor (1) and the floor (2) is obtained.

The above-described embodiment can be modified and implemented as follows. (1) It is preferable to store the granular material in all of the beams, but it is also possible to store the granular material in a part of the multiple beams or a part of the length of the beams. The portion for storing the granular material may be selected according to the vibration mode of the floor structure. (2) The beam material is not limited to the joist, and may have a portion corresponding to a pulling. The pulling portion may be formed into a hollow shape to accommodate a granular material. Further, the frame material may be a hollow shape material to accommodate the granular material. (3) When the beam is made of a material having a damping effect such as a damping steel plate, the elastic body or the viscoelastic body provided in the hollow portion of the beam can be omitted. (4) The frame material and the beam material are not limited to steel materials but may be aluminum alloys. Also, the profile material forming the frame material and beam material is
It is not limited to roll forming but may be an extruded product. (5) In the case where the space above the ceiling directly below the floor of the floor is filled with sound-absorbing material, when the ceiling and the space above the ceiling can prevent secondary noise generated from the beam due to the operation of the granular material, The elastic body or the viscoelastic body provided in the hollow portion of the beam member can be omitted. (6) The hollow portion of the beam is not limited to the one closed in cooperation with the beam itself or the floor plate as shown in FIGS. FIG.
As in 1, the beam member 303 may have a C-shaped cross section and the concave portion at the bottom may be a hollow portion. In this case, the granular material 313
In the bag 312 so that the bag 312 does not fall from the hollow portion by being caught in the concave portion. Also,
The beam member may have a U-shaped cross section, and may be fixed with a wire so that the bag body containing the granular material does not fall from the opening.

[0035]

According to the first aspect of the present invention, by enclosing the granular material in the hollow portion of the beam, an excellent soundproofing effect can be obtained while maintaining the basic structure of the frame member and the beam. Can be demonstrated. The whole can be manufactured inexpensively as compared with the case where soundproofing is performed on the entire surface of the floorboard. In addition, since there are no restrictions on floor boards, various floor boards such as synthetic wood can be used in combination. Further, since a thin plate member can be used for the frame member and the beam member, the present invention can be applied to a steel house or the like which can be constructed on site.

According to the second aspect of the invention, in addition to the effect of the first aspect, it is possible to prevent the generation of a secondary impact sound caused by the vibration inside the beam of the granular material.

According to the third aspect of the present invention, in addition to the effect of the second aspect, a plurality of bags are serially arranged in the longitudinal direction of the beam in order to insert the cylindrical bag containing the granular material into the beam. Place it,
By stacking a plurality of bags in the height direction of the beam material, the granular material can be easily and appropriately stored inside the beam material.

According to the fourth aspect of the invention, in addition to the effects of the first to third aspects, an inexpensive granular material that effectively produces a soundproofing effect can be used.

According to the fifth aspect of the invention, in addition to the effects of the first to fourth aspects, a beam having a closed internal space can be easily obtained.

According to the sixth aspect of the invention, in addition to the effects of the first to fifth aspects, the selection of the floorboard can be freely performed.

[Brief description of the drawings]

FIG. 1 is a top view showing a framework of a floor structure according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a sectional structure of the beam member of FIG.

FIG. 3 is a cross-sectional view showing a cross-sectional structure of another embodiment of a beam member.

FIG. 4 is a sectional view showing a sectional structure of still another embodiment of a beam member.

FIG. 5 is a graph showing a relationship between an excitation acceleration and a moving mass when a filling amount of a granular material into a beam material is changed.

FIG. 6 is a graph showing a reduction in radiated sound due to the use of a silencing material.

FIG. 7 is a side view showing a vibration mode of a floor structure having a framework of a frame member and a beam member.

FIG. 8 is a graph showing the results of heavy floor impact sound level measurement.

FIG. 9 is a graph showing measurement results of a lightweight floor impact sound level.

FIG. 10 is a graph showing a vibration level at the time of hammer strike excitation.

FIG. 11 is a sectional view showing a sectional structure of still another embodiment of a beam member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Floor structure 2 Frame material 3 Beam material 4 Floor plate 5 Frame 11 Hollow part 12 Elastic body or viscoelastic body 13 Granular body

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mikishi Harada 3-23-8 Kodashimachi, Tokorozawa-shi, Saitama Pref. Inside Harada Corporation (72) Inventor Kazuki Tsujihashi 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Prefecture No. 5 F term in Kobe Steel, Ltd. Kobe Research Institute (reference) 2E001 DF01 FA11 GA03 GA10 GA20 GA46 GA66 HE01 JA00

Claims (6)

[Claims] 1. A floor structure comprising a frame made of a metal profile and a beam made of a metal profile spanned inside the frame, wherein all or a part of the beam is formed in a hollow portion. A floor structure in which a granular material is accommodated in the hollow portion. 2. The floor structure according to claim 1, wherein an elastic body or a viscoelastic body is interposed between all or a part of an inner wall of the hollow portion and the granular body. 3. The floor structure according to claim 2, wherein the elastic body or the viscoelastic body is a bag housed in the hollow portion. 4. The floor structure according to claim 1, wherein the granules are reduced pellets. 5. The floor structure according to claim 1, wherein said beam member is formed by combining groove-shaped cross-section members so that said hollow portion becomes a closed space. 6. The floor structure according to claim 1, wherein a floor plate is joined to upper surfaces of said frame member and said beam member.