JP7641564B2 - Building floor structure equipped with dynamic vibration absorbers - Google Patents

Description

This disclosure relates to floor structures equipped with dynamic vibration absorbers (TMDs) to reduce floor impact noise in buildings such as apartment complexes and hotels.

In buildings such as apartment buildings and hotels, when the floors on the upper floors receive impacts from people walking, the floors vibrate, and the vibrations are transmitted as sound to the floors below, creating a problem of floor impact noise. Various measures to reduce floor impact noise have been proposed in the past.

In a double floor where a floor is placed on a concrete floor slab via support legs, a method of reducing floor impact noise by increasing the mass of the floor itself has been implemented. In addition, in a double ceiling where a ceiling board is attached under a floor slab (ceiling slab) via a ceiling underlayment, an invention has been proposed in which a container containing granular material is placed between the floor slab and the ceiling board, and the granular material moves inside the container to attenuate vibration energy and reduce floor impact noise (for example, Patent Document 1). In addition, in a floor slab where a void (hollow portion) is formed using a steel pipe, an invention has been proposed in which a bag filled with sand is loaded into the steel pipe, and the vibration energy is converted into frictional heat of the sand to reduce floor vibration (for example, Patent Document 2). In addition, an invention has been proposed in which a dynamic vibration absorber equipped with a mass body and a coil spring is installed on the floor (for example, Patent Document 3). Also, an invention has been proposed in which a weight is placed inside a floor slab containing a void formwork material made of foamed plastic, and the void formwork material is used as a spring member to support the weight from above and below with the void formwork material, creating a dynamic vibration absorber (for example, Patent Document 4).

JP 2014-37678 A JP 2015-113694 A JP 2006-161388 A JP 2018-168677 A

However, the means for increasing the mass of the floor plate have problems in that they cannot be used for directly laid floors and the material costs are high. The invention in which a container containing granular material is installed between the floor slab and the ceiling board cannot be used for directly laid ceilings and has the problem that the time required to install the container is time consuming and labor costs increase. The invention in which bags filled with sand are loaded into voids formed by steel pipes also has the problem that the time required to load the bags into the voids is time consuming and labor costs increase. The invention in which a dynamic vibration absorber is installed as described in Patent Document 3 requires the installation of a dynamic vibration absorber equipped with a mass body and a coil spring between the floor and the underfloor structure, which has the problem that the installation is time consuming and labor costs increase. In the invention described in Patent Document 4, which uses void formwork material to provide a dynamic vibration absorber, if the thickness (load) of the top concrete on the half-precast concrete plate is changed, the degree of compaction of the void formwork material, which functions as a spring, changes. Also, depending on the type of material used, the void formwork material below the weight may become significantly distorted due to long-term creep, which may change the degree of contact between the void formwork material supporting the upper side of the weight and the weight, and this may cause the natural frequency of the dynamic vibration absorber to change.

In light of this background, the present invention aims to provide a floor structure for a building equipped with a dynamic vibration absorber that is easy to install and unlikely to deteriorate in performance.

One embodiment of the present invention is a floor structure (1) of a building equipped with a dynamic vibration absorber (3), which comprises a concrete floor slab (2) having a void (11), a void formwork material (5) embedded in the floor slab (2) to form the void (2) and having a hollow part (14) in the formwork, a spring member (28) that includes elastic foamed plastic and is supported by the void formwork material (5) or the floor slab (2), and a weight (29) that is arranged in the hollow part (14) in the formwork and supported from below by the spring member (28) so as to be able to vibrate in the vertical direction in order to cooperate with the spring member (28) to form the dynamic vibration absorber (3), and the member that directly supports the weight (29) to be able to vibrate in the vertical direction is characterized in that it is only one or more of the spring members (28).

According to this configuration, the work after installing the void formwork material is almost the same as the method of using void formwork material in a floor slab that does not have measures against floor impact noise, and the half precast method does not increase the amount of work at the construction site, so workability at the construction site is good. In addition, if the spring members support the weight from above and below, the degree of compaction of the spring members changes when the thickness of the upper concrete is changed, and there is a risk that the lower spring member will distort due to long-term creep, changing the degree of contact of the upper spring member with the weight, and changing the natural frequency of the dynamic vibration absorber. However, with the above configuration, the spring members are placed only below the weight, so changes in the natural frequency of the dynamic vibration absorber are suppressed, and the performance of the dynamic vibration absorber is less likely to deteriorate.

One embodiment of the present invention is characterized in that in the above configuration, the spring member (28) is separate from the void formwork material (5).

With this configuration, since the spring member is separate from the void formwork material, it is possible to select suitable materials for both the spring member and the void formwork material.

One embodiment of the present invention is characterized in that in the configuration described immediately above, the void formwork material (5) contains a different type of foamed plastic than the spring member (28), and the foamed plastic of the spring member (28) has a greater damping constant than the foamed plastic of the void formwork material (5).

This configuration allows vibrations to be reduced widely around the dynamic vibration absorber's natural frequency, and also reduces the amplification of vibrations at frequencies around that frequency.

In one embodiment of the present invention, in any of the above configurations, the weight (29) has a hole (30) penetrating in the vertical direction, and the void formwork material (5) includes a bottom wall (15) that defines the lower surface of the hollow portion (14) in the formwork, a cover wall (19) that defines the upper surface of the hollow portion (14) in the formwork, and a support portion (27) that penetrates the hole (30) and connects to the bottom wall (15) and the cover wall (19).

With this configuration, even if a worker steps on the cover wall during construction, the cover wall is supported by the support column, preventing the cover wall from cracking when stepped on.

One embodiment of the present invention is characterized in that, in the configuration described directly above, the lower surface of the weight (29) is provided with a recess (31) that receives the upper part of the spring member (28).

With this configuration, even if the spring member and weight are transported while placed in the hollow space inside the formwork, the spring member engages with the side of the recess, limiting the horizontal displacement of the weight relative to the spring member within a specified range.

In one embodiment of the present invention, in the configuration described directly above, in a direction in which the first inner surface defining the hole (30) of the weight (29) faces the outer surface of the support (27) when the weight is positioned so that the center of the hole (30) and the center of the support (27) coincide with each other in a plan view, the distance (a) between the second inner surface forming the side surface of the recess (31) of the weight (29) and the side surface of the spring member (28) facing the second inner surface is greater than 0, is smaller than the distance (b) between the outer surface of the weight (29) and the inner surface defining the hollow portion (14) of the formwork of the void formwork material (5), and is smaller than the distance (c) between the first inner surface of the weight (29) and the outer surface of the support (27).

With this configuration, even if the weight is displaced horizontally relative to the spring member during transportation, etc., the weight is engaged with the spring member, so that the weight does not come into contact with the inner surface that defines the hollow portion within the formwork of the void formwork material, and deterioration of the dynamic vibration absorber's function is suppressed.

In one embodiment of the present invention, in any of the above configurations, the underside of the spring member is supported by the void formwork material, and the portion of the void formwork material that supports the spring member has a thickness of 10 mm or more.

With this configuration, even if there are unevenness on the underside that defines the void, the void formwork material mitigates the impact of the unevenness on the spring member.

The present invention provides a building floor structure equipped with a dynamic vibration absorber that is easy to install and unlikely to deteriorate in performance.

FIG. 1 is a vertical cross-sectional view of a floor structure according to an embodiment; FIG. 1 is a plan view of a void formwork material according to an embodiment and components included therein; 3 is a cross-sectional view taken along line III-III in FIG. 2. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. 3 is a cross-sectional view taken along line VV in FIG. 2.

The building floor structure 1 according to the present invention will be described in detail below with reference to the drawings.

Figure 1 is a plan view of a floor structure 1 according to an embodiment of the present invention. The floor structure 1 is used for floors in buildings such as apartment buildings and hotels where reduction of floor impact noise is required. The floor structure 1 comprises a floor slab 2 made of reinforced concrete, and a member that functions as a dynamic vibration absorber 3 is arranged on the floor slab 2. The floor may be a double floor or a direct floor, and the ceiling of the lower floor may be a double ceiling or a direct ceiling.

The floor slab 2 is formed by the half precast construction method and includes a half PCa plate 4 made of precast concrete, slab top reinforcement 6 arranged above void formwork material 5 arranged on the half PCa plate 4 and extending horizontally along the vertical direction (direction perpendicular to the paper surface of FIG. 1) and horizontal direction (left-right direction of FIG. 1), and top concrete 7 poured to embed the void formwork material 5 and the slab top reinforcement 6.

The half PCa plate 4 includes a lower concrete 8, a slab bottom end bar 9 extending horizontally along the vertical and horizontal directions in the lower concrete 8, and truss bars 10. The truss bars 10 include a pair of bottom bars 10a embedded in the lower concrete 8 so as to extend horizontally along the vertical direction and spaced apart from each other in the horizontal direction, a top bar 10b located above the lower concrete 8 and at the midpoint of the spacing direction (horizontal direction) of the pair of bottom bars 10a and extending parallel to the bottom bars 10a, and a pair of lattice bars 10c. The pair of lattice bars 10c each have a wave shape when viewed from the left and right direction of FIG. 1, and abut against the top bar 10b and the corresponding bottom bar 10a near the apex of the wave shape, and the abutting positions are aligned with each other in the spacing direction (horizontal direction) of the bottom bars 10a. In the example shown, the bottom reinforcement 10a is double reinforcement, but it may be single reinforcement.

The void formwork material 5 has a flat plate-like outer shape that is rectangular in plan view. Since the void formwork material 5 is an embedded formwork for forming a void 11 in the floor slab 2, the lower surface of the void formwork material 5 abuts against the half PCa plate 4, and the outer surface other than the lower surface of the void formwork material 5 abuts against the inner surface that defines the void 11 in the top concrete 7. The void formwork material 5 is preferably made of foamed plastic such as polystyrene foam. Note that the void formwork material 5 may contain materials other than foamed plastic such as reinforcement materials. The void formwork material 5 includes a lower formwork material 12 placed on the half PCa plate 4 and an upper formwork material 13 arranged above the lower formwork material 12, and has a hollow portion 14 inside the formwork defined by the lower formwork material 12 and the upper formwork material 13. In the illustrated example, two hollow spaces 14 are provided within the formwork for one void formwork material 5, but one hollow space 14 within the formwork may be provided for one void formwork material 5, or three or more hollow spaces 14 may be provided.

Figures 2 to 5 are plan views of the void formwork material 5 and the members contained in the hollow portion 14 within the formwork, cross-sectional views along line III-III in Figure 2, cross-sectional views along line IV-IV, and cross-sectional views along line V-V.

The lower formwork member 12 includes a generally flat bottom wall 15 that is rectangular in plan view, a lower wall 16 that protrudes upward from the outer periphery of the bottom wall 15, a lower central wall 17 that protrudes upward from the center of the long side direction of the bottom wall 15 and extends in the short side direction, and a lower support 18 that protrudes upward from the bottom wall 15 in the center of the space surrounded by the lower wall 16 and the lower central wall 17. The upper formwork member 13 includes a generally flat cover wall 19 that is rectangular in plan view and generally matches the lower formwork member 12, an upper wall 20 that protrudes downward from the outer periphery of the cover wall 19, an upper central wall 21 that protrudes downward from the center of the long side direction of the cover wall 19 and extends in the short side direction, and an upper support 22 that protrudes downward from the cover wall 19 in the center of the space surrounded by the upper wall 20 and the upper central wall 21.

The upper surface of the lower wall 16 is provided with side protrusions 23 along the outer edge of the lower formwork material 12, and the lower surface of the upper wall 20 is provided with side grooves 24 along the outer edge of the upper formwork material 13 into which the side protrusions 23 fit. The upper surface of the lower central wall 17 is provided with a pair of central protrusions 25 extending in the same direction as the lower central wall 17, and the lower surface of the upper central wall 21 is provided with a pair of central grooves 26 extending in the same direction as the upper central wall 21 into which the pair of central protrusions 25 fit. By attaching the upper formwork material 13 to the lower formwork material 12 so that the side protrusions 23 fit into the side grooves 24, the joint between the lower formwork material 12 and the upper formwork material 13 becomes liquid-tight, and the top concrete 7 before hardening is prevented from flowing into the hollow portion 14 in the formwork. Furthermore, by fitting the central protrusion 25 into the central groove 26, the upper formwork material 13 is stabilized relative to the lower formwork material 12 before the top concrete 7 is poured. The upper surface of the lower support 18 and the lower surface of the upper support 22 are in contact with each other, and the lower support 18 and the upper support 22 form a support section 27 that connects the bottom wall 15 and the cover wall 19 within the hollow section 14 of the formwork.

The dynamic vibration absorbers 3 are provided in each hollow section 14 in the formwork. The dynamic vibration absorber 3 provided in one hollow section 14 in the formwork comprises a pair of spring members 28 supported from below by the lower formwork material 12, and one weight 29 that is disposed in the hollow section 14 in the formwork so as not to abut against the inner surface of the void formwork material 5 and is supported from below by the pair of spring members 28 so as to be able to vibrate in the vertical direction.

The pair of spring members 28 are arranged on opposite sides of the support 27 in a plan view. Each spring member 28 is made of elastic foamed plastic. The spring member 28 is separate from the void formwork material 5 and is preferably made of a foamed plastic of a different type from the void formwork material 5, and is more preferably made of a foamed plastic having a larger damping constant than the foamed plastic constituting the void formwork material 5. For example, foamed polyethylene with a damping constant of about 7% may be used as the spring member 28. A pair of formwork recesses 32 are provided on the upper surface of the lower formwork material 12, which are located on opposite sides of the lower support 18, and the lower part of the spring member 28 is fitted into the formwork recesses 32. The thickness from the bottom surface of the formwork recesses 32 in the lower formwork material 12 to the lower surface of the bottom wall 15 is about 10 mm or more, which is the minimum foaming dimension of expanded polystyrene, so as not to significantly change the spring constant of the spring member 28, and is preferably about 10 mm.

The weight 29 is preferably made of a concrete plate. The concrete plate may be made of reinforced concrete or unreinforced concrete. The weight 29 may be made of a material other than concrete, such as steel, or a mixture of these materials. The weight 29 is rectangular in plan view and has a hole 30 that penetrates vertically in the center. The support 27 of the void formwork material 5 penetrates the hole 30. In plan view, the hole 30 and the support 27 are rectangular, and the long sides of the holes 30 and the support 27 are aligned with each other. The lower surface of the weight 29 is provided with a recess 31 that loosely receives the upper parts of the pair of spring members 28. The recess 31 is rectangular in bottom view. The hole 30 is provided from the bottom surface (top surface) of the recess 31 toward the top.

The total weight of the weights 29 placed in one void 11 is preferably 2 to 10% of the weight of the floor slab 2 in the area that defines the bearing area of the void 11 in which the weights 29 are housed. Here, the area that defines the bearing area of the void 11 refers to the area, in plan view, up to the center line of the wall that separates the two voids 11 in the direction in which other voids 11 are adjacent, and up to the end of the floor slab 2 in the direction in which other voids 11 are not adjacent.

It is preferable that the spring member 28 is positioned closer to the center than the outer periphery of the weight 29 in a plan view, and it is even more preferable that the surface of the spring member 28 facing the support portion 27 coincides with or is close to the inner periphery defining the hole 30 of the weight 29, and that the surface of the spring member 28 opposite the surface facing the support portion 27 is spaced inward from the outer periphery of the weight 29.

The spring member 28 made of elastic foamed plastic elastically supports the weight 29 from below with a certain spring force. Therefore, the spring member 28 and the weight 29 constitute the dynamic vibration absorber 3, which absorbs the vibration energy of the floor structure 1 and reduces floor impact noise. The natural frequency of the dynamic vibration absorber 3 is adjusted by the mass of the weight 29, the shape of the spring member 28, the contact area between the weight 29 and the spring member 28, the foaming ratio of the foamed plastic, etc. In order to mainly reduce heavy floor impact noise caused by people walking, jumping, etc., it is preferable to adjust the natural frequency so that the center frequency in the octave band is within the band of 63 Hz.

The recess 31 of the weight 29 loosely receives the upper part of the spring member 28, so that the weight 29 can be displaced horizontally relative to the spring member 28. The reference position of the weight 29 is the position where the weight 29 is arranged so that the vertical and horizontal directions of the spring member 28 and the weight 29 are aligned with each other in a plan view, and the center of the hole 30 of the weight 29 and the center of the support part 27 coincide with each other. When the weight 29 is placed at the reference position, in the horizontal direction (the direction in which the inner surface defining the hole 30 of the weight 29 faces the outer surface of the support 27), the inner surface defining the recess 31 of the weight 29 and the side surface of the spring member 28 facing this inner surface are separated from each other by a first separation distance a, the outer surface of the weight 29 and the inner surface defining the hollow portion 14 in the formwork of the void formwork material 5 are separated from each other by a second separation distance b, and the inner surface defining the hole 30 of the weight 29 and the outer surface of the support 27 are separated from each other by a third separation distance c. The first separation distance a is greater than 0 and smaller than the second separation distance b and the third separation distance c. For example, the first separation distance a may be 2 mm, the second separation distance b may be 10 mm, and the third separation distance c may be 5 mm. As a result, the upper part of the spring member 28 is received in the recess 31 with a gap, and even if a force is applied that shifts the relative horizontal positions of the weight 29 and the spring member 28, the side of the spring member 28 engages the inner surface of the recess 31 of the weight 29, so the side of the weight 29 and the inner surface of the void formwork material 5 are kept apart.

The construction method of the floor structure 1 will be described. In a precast concrete manufacturing factory, workers manufacture the half PCa plate 4. Immediately after pouring the lower concrete 8 or before it hardens, the lower formwork material 12 is placed on the upper surface of the half PCa plate 4. When the concrete hardens, the lower formwork material 12 is fixed to the half PCa plate 4. The lower formwork material 12 may be fixed to the half PCa plate 4 using nails or the like before the lower concrete 8 hardens. After the concrete constituting the lower concrete 8 hardens, the worker fits the lower part of the spring member 28 into the formwork recess 32, and attaches the weight 29 to the spring member 28 so that the upper part of the spring member 28 is received in the recess 31 of the weight 29. Next, the worker attaches the upper formwork material 13 to the lower formwork material 12 so that the side protrusions 23 and the central protrusions 25 fit into the side grooves 24 and the central grooves 26. The half PCa plate 4 to which the void formwork material 5, spring member 28, and weight 29 are attached is transported to the construction site of the floor structure 1. The spring member 28 may be fitted in advance into the formwork recess 32 of the lower formwork material 12, and the lower formwork material 12 with the spring member 28 fitted therein may be placed on the upper surface of the half PCa plate 4 immediately after the lower concrete 8 is poured or before it hardens, and the weight 29 and upper formwork material 13 may be installed after the lower concrete 8 hardens. If the weight 29 is installed before the lower concrete 8 hardens, the lower formwork material 12 will sink, so it is preferable to install the weight 29 and upper formwork material 13 after the lower concrete hardens.

Next, the half PCa plate 4 with the void formwork material 5, spring member 28 and weight 29 attached is placed in the part of the construction site where the floor structure 1 is to be manufactured. The half PCa plate 4 is supported from below by shoring (not shown) and is spanned between the beams (not shown) of the half precast structure. Workers arrange the slab upper end reinforcement 6 that extends horizontally so that it intersects perpendicularly between the multiple top reinforcement 10b, and arrange the slab upper end reinforcement 6 that extends vertically so that it spans between the multiple slab upper end reinforcement 6 that extend horizontally.

Next, workers set up a formwork (not shown) for pouring the top concrete 7, and pour the top concrete 7 together with the concrete on top of the beam. After the top concrete 7 hardens, workers dismantle the formwork and shoring for the top concrete 7.

The effect of the floor structure 1 will be explained. The floor structure 1 is equipped with a dynamic vibration absorber 3, so that the weight 29 resonates with the vibration of the floor, thereby suppressing floor impact noise.

The work at the construction site is roughly the same as that for half-precast floor slabs that do not have floor impact sound countermeasures, so workability at the site is not compromised.

By supporting the weight 29 from below, the spring member 28 maintains contact with the weight 29 even if the spring member 28 deforms due to long-term creep, so performance is unlikely to deteriorate even with long-term use. In addition, even if the cross-sectional specifications of the floor slab 2 are changed, there is no effect on the compaction of the spring member 28 that supports the weight 29 from below, so there is no need to change the structure of the dynamic vibration absorber 3.

Because the spring member 28 is separate from the void formwork material 5, the spring member 28 and the void formwork material 5 can be made of materials suitable for springs and forms. A suitable material for forms is polystyrene foam, but a dynamic vibration absorber using polystyrene foam with a damping constant of about 1% as a spring greatly reduces floor vibrations having frequencies near the natural frequency of the dynamic vibration absorber, but greatly amplifies (anti-resonates) vibrations of frequencies before and after that frequency. This reduces the floor impact sound reduction effect evaluated in the octave band. On the other hand, a dynamic vibration absorber 3 using a material such as foamed polyethylene (damping constant: about 7%), which has a damping constant larger than polystyrene foam, as the spring member 28 reduces vibrations widely near the natural frequency of the dynamic vibration absorber 3, and the amplification of vibrations of frequencies before and after that frequency is also small. This increases the floor impact sound reduction effect evaluated in the octave band.

Because the weight 29 is plate-shaped, rocking occurs. If the spring members 28 of the dynamic vibration absorber 3 are arranged in a dispersed manner, the natural frequency of the dynamic vibration absorber 3 and the rocking frequency become close, which may reduce the effect of the dynamic vibration absorber 3 in suppressing floor vibration noise. In this embodiment, the spring members 28 are arranged near the center of the weight 29 in a plan view, thereby lowering the rocking frequency to a value away from the natural frequency of the dynamic vibration absorber 3, and therefore the effect of suppressing floor vibration noise is not reduced.

The upper formwork material 13 is attached to the lower formwork material 12 by fitting the side protrusions 23 and central protrusions 25 into the side grooves 24 and central grooves 26, preventing poured concrete from flowing into the hollow space 14 within the formwork.

It is expected that workers will stand on the void formwork material 5 when placing the slab top end reinforcement 6. Therefore, by providing a support section 27 that passes through the hole 30 of the weight 29, the cover wall 19 is supported from below in the center of the void formwork material 5, and downward deflection of the cover wall 19 is suppressed. By suppressing the deflection of the cover wall 19, cracks in the upper formwork material 13 are prevented, and changes in the spring constant of the spring member 28 caused by the cover wall 19 pressing down on the weight 29 and compressing the spring member 28 can be prevented.

The upper part of the spring member 28 is loosely received in the recess 31 of the weight 29, so that the weight 29 is prevented from damaging the spring member 28 when it is attached to the spring member 28, and the spring member 28 acts as a stopper to limit the horizontal displacement of the weight 29 when the void formwork material 5, the spring member 28, and the half PCa board 4 to which the weight 29 is attached are transported from the factory to the construction site. In addition, since the first separation distance a is smaller than the second separation distance b and the third separation distance c at the reference position, even if the weight 29 is displaced horizontally from the reference position, the weight 29 does not come into contact with the inner surface of the void formwork material 5, and the vertical vibration of the weight 29 is not hindered.

If the installation position of the spring member 28 differs from product to product, there is a risk of variation in the performance of the dynamic vibration absorber 3. However, because the spring member 28 is fitted into the formwork recess 32 and positioned at a specified position, variation in the performance of the dynamic vibration absorber 3 is suppressed.

There is a risk of unevenness occurring on the top surface of the half PCa plate 4. If the spring member 28 is directly supported on the top surface of the half PCa plate 4, which has unevenness, the top surface of the spring member 28 will not be in close contact with the weight 29, and this may affect the performance of the dynamic vibration absorber 3. Therefore, by having the spring member 28 supported on a lower formwork material 12 having a predetermined thickness, the thickness of the lower formwork material 12 mitigates the effect of unevenness on the top surface of the half PCa plate 4 on the spring member 28.

Although the specific embodiment has been described above, the present invention is not limited to the above embodiment and can be modified in a wide range of ways. The floor slab may be made of full precast concrete or cast-in-place concrete. The shape of the weight and spring member may be changed as long as the weight can vibrate in the vertical direction. The arrangement of the protrusions and grooves may be reversed on the upper and lower side walls and central wall of the lower and upper formwork. The formwork recesses may be through holes so that the spring members are directly supported on the floor slab.

Reference Signs List 1: Floor structure 2: Floor slab 3: Dynamic vibration absorber 4: Half PCa plate 5: Void formwork material 7: Top concrete 11: Void 12: Lower formwork material 13: Upper formwork material 14: Hollow portion inside formwork 15: Bottom wall 19: Cover wall 27: Support portion 28: Spring member 29: Weight 30: Hole 31: Recess

Claims (5)

A floor structure of a building equipped with a dynamic vibration absorber,
a concrete floor slab having a void;
A void formwork material embedded in the floor slab to form the void and having a hollow portion inside the formwork;
A spring member including a resilient foamed plastic and supported on the void formwork material or the floor slab;
a weight that is disposed in the hollow portion of the formwork and supported from below by the spring member so as to cooperate with the spring member to form the dynamic vibration absorber, and that is capable of vibrating in a vertical direction;
a member directly supporting the weight so as to be able to vibrate the weight in the vertical direction is composed only of one or more of the spring members;
The weight has a hole passing through in the vertical direction,
The void formwork material includes a bottom wall that defines a lower surface of the hollow portion in the formwork, a cover wall that defines an upper surface of the hollow portion in the formwork, and a support portion that penetrates the hole and connects to the bottom wall and the cover wall,
A floor structure characterized in that a recess is provided on the lower surface of the weight to receive the upper part of the spring member . The floor structure according to claim 1, characterized in that the spring member is separate from the void formwork material. the void formwork material includes a foamed plastic of a different type than the spring member;
3. The floor structure according to claim 2, wherein the foamed plastic of the spring member has a damping constant greater than that of the foamed plastic of the void formwork material. A floor structure as described in any one of claims 1 to 3, characterized in that, in a direction in which a first inner surface defining the hole of the weight and an outer surface of the support portion face each other when the weight is positioned so that the center of the hole and the center of the support portion coincide with each other in a planar view, the distance between a second inner surface forming a side surface of the recess of the weight and a side surface of the spring member facing the second inner surface is greater than 0, smaller than the distance between the outer surface of the weight and an inner surface defining the hollow portion within the formwork of the void formwork material, and smaller than the distance between the first inner surface of the weight and the outer surface of the support portion. A floor structure as described in any one of claims 1 to 4 , characterized in that the underside of the spring member is supported by the void formwork material, and the portion of the void formwork material that supports the spring member has a thickness of 10 mm or more.

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