JP7765246B2 - Wind noise reduction device for lattice structures, balusters and lattice structures - Google Patents

Description

The present invention is aimed at reducing the volume of structure-borne sound (hereinafter referred to as wind noise) emitted by lattice structures such as handrails installed on building windows, verandas, balconies, rooftops, emergency stairs, etc., or fences installed on the boundaries of land, houses, etc., when exposed to wind.

The lattice structure comprises a plurality of balusters arranged at intervals and extending linearly vertically, horizontally or diagonally. The wind noise is generated by a resonance phenomenon (vortex-induced vibration) that occurs when the predominant frequency of Kármán vortices generated when wind blows between the balusters of the lattice structure matches the natural frequency of the balusters, or when the predominant frequency of the Kármán vortices is close to the natural frequency of the balusters.

In order to reduce the volume of wind noise in vertical lattice handrails, which are one type of lattice structure, attempts have been made to place a pair of metal plates that partially face each other at the bottom of a hollow balusters with a rectangular cross-section. Each metal plate is fixed to the balusters with bolts, extends upward from the lower end of the balusters, and is in contact with the inner wall surface of the balusters. However, this approach is considered insufficient in terms of preventing wind noise.

JP 2009-30364 A

In consideration of the above-mentioned conventional circumstances, the present invention provides a new wind noise reduction device for reducing wind noise in a lattice structure, a balusters to which the wind noise reduction device is attached, and a lattice structure equipped with the balusters.

This invention (first invention) relates to a wind noise reduction device applicable to a lattice structure consisting of a handrail or fence with a plurality of hollow balusters each having a rectangular cross section. The wind noise reduction device comprises: a pair of opposing plate members arranged inside each baluster, the pair of plate members extending inside the balusters in the extension direction of the balusters; and a plurality of spring members arranged between the two plate members at intervals in the longitudinal direction of the two plate members and fixed to the two plate members, the plurality of spring members applying a pressing force to the two plate members inside each baluster so that the two plate members abut against the inner wall surfaces of the respective balusters. When the lattice structure is hit by wind and each baluster vibrates in one or more of a primary vibration mode, a secondary vibration mode, and a tertiary vibration mode, the length of the two plate members is such that they can abut against the inner wall surfaces of each baluster at points of amplitude peaks of the vibrations that occur.

In the present invention, the phrase "when the lattice structure is subjected to wind and each baluster vibrates in one or more of the primary, secondary, and tertiary vibration modes" is based on the knowledge that the wind speed (wind velocity) that normally acts on the lattice structure is within the range of 5 to 15 m/s, and that within this wind speed range, each baluster vibrates in one or more of the primary to tertiary vibration modes.

This invention (second invention) relates to a balusters used in the manufacture of lattice structures consisting of handrails or fences. The balusters include a tubular member having a rectangular cross-sectional shape and the wind noise reduction device disposed inside the tubular member.

The present invention (third invention) relates to a lattice structure consisting of a handrail or fence with a plurality of balusters. The balusters of the lattice structure are the balusters according to the second invention.

The wind noise reduction device according to the present invention can be placed inside a balustrade by pressing a pair of plate members toward each other to compress the multiple spring members between them, and then inserting the plate members into the interior of the balustrade from one end to the other of the balustrade of an unmanufactured lattice structure. Inside the balustrade, both plate members are subjected to a pressing force, which is the elastic return force of the multiple compressed spring members, and come into contact with the inner wall surface of the baluster, bringing them into close contact with the inner wall surface of the baluster.

According to the present invention, when a lattice-like structure including multiple balusters to which the wind noise reduction device is attached is subjected to wind, and vibrations in one or more of the primary, secondary, and tertiary vibration modes occur in each baluster, the balusters undergo elastic deformation corresponding to the vibrations. At this time, the two plate members within each baluster abut against the inner wall surface of each baluster at the peak amplitude of the vibrations occurring in the baluster. As a result, they receive external forces from the balusters due to their elastic deformation and undergo elastic deformation along the inner wall surface of the baluster. At this time, both plate members vibrate with their respective spring members as fulcrums, sliding slightly on the inner wall surface of the baluster. As a result, friction occurs between the inner wall surface of the baluster and both plate members. This friction dissipates the vibration energy of the baluster, reducing the vibration of the baluster and the associated wind noise.

The length of the plate members is preferably set to a size equivalent to 10/12 of the length of each balusters. Here, both plate members are positioned such that one and the other of their ends are spaced apart from the other end of the balusters by a distance equivalent to 1/12 of the length of the balusters. This ensures that even if the wind noise reduction device slides down the inside of the balusters due to its own weight when the balusters vibrate to the bottom, both plate members remain in a state where they can abut against the inner wall surfaces of the balusters at the peak of the vibration amplitude of the balusters.

The plurality of spring members preferably consist of two spring members located near both ends of each plate member, and one spring member located midway between the two spring members. The spring members may be, for example, compression coil springs.

FIG. 1 is a perspective view of a vertical lattice handrail, which is one of the lattice structures according to the present invention. FIG. 2 is a schematic vertical cross-sectional view showing a wind noise reduction device and a balustrade to which the wind noise reduction device is attached. FIG. 3 is a plan view of the wind noise reduction device and balusters shown in FIG. 2 . (a) is a schematic vertical cross-sectional view of a balusters and a wind noise reduction device therein when not vibrating; (b) is a schematic vertical cross-sectional view of a balusters and a wind noise reduction device therein when vibrating in a primary vibration mode; (c) is a schematic vertical cross-sectional view of a balusters and a wind noise reduction device therein when vibrating in a secondary vibration mode; and (d) is a schematic vertical cross-sectional view of a balusters and a wind noise reduction device therein when vibrating in a tertiary vibration mode. 10 is a graph showing the results of verification of wind noise reduction through a wind tunnel experiment.

The present invention is aimed at reducing wind noise from lattice structures such as handrails (vertical lattice handrails, horizontal lattice handrails, diagonal lattice handrails, etc.) installed on building windows, verandas, balconies, rooftops, emergency stairs, etc., or fences installed on the boundaries of land, houses, etc.

Referring to Figure 1, a vertical lattice handrail, which is an example of a lattice structure to which the present invention is applied, is indicated generally by the reference numeral 10. The vertical lattice handrail 10 comprises a plurality of balusters 12 and a wind noise reduction device 14 (Figures 2 and 3) attached to each balusters 12.

The illustrated vertical lattice handrail 10 comprises a pair of posts 16 extending vertically (up and down) and two upper and lower chord members 18 fixed to the posts 16 and extending horizontally. Multiple balusters 12 are spaced apart between the chord members 18 and extend vertically. Each balusters 12, post 16, and chord member 18 is made of extruded aluminum, for example.

As shown in Figures 2 and 3, the balusters 12 are made of tubular members with a rectangular cross-section. They have opposing upper and lower ends 12a and 12b, and are fixed to the upper and lower chord members 18 at their upper and lower ends 12a and 12b. Each balusters 12 also has two pairs of opposing outer wall surfaces (exterior surfaces) 12c and 12d, and two pairs of opposing inner wall surfaces (interior surfaces) 12e and 12f (see Figures 2 and 3). The pair of outer wall surfaces 12c of each balusters 12 faces the adjacent balusters 12 or posts 16. The other pair of outer wall surfaces 12d face the front and rear sides of the vertical lattice railing 10, respectively.

The wind noise reduction device 14 comprises a pair of opposing plate members 22 arranged inside the balusters 12, and multiple (three in the illustrated example) spring members 24. Inside the balusters 12, the plate members 22 extend in the extension direction of the balusters 12 and receive the spring force of the spring members 24, coming into contact with both inner wall surfaces 12e of the balusters 12. The multiple spring members 24 are also arranged between the plate members 22 at intervals in the longitudinal direction.

The pair of plate members 22 of the wind noise reduction device 14 each consist of a flat plate made of metal, such as aluminum or steel, or a flat plate made of wood, synthetic resin, or rubber. The plate members 22 have a length L2 (L2<L1) that is shorter than the length L1 of the balusters 12 (see Figure 3). The balusters 12 also have a width that is smaller than the width of the inner wall surfaces 12e of the balusters 12 (see Figure 3). Taking into account their elastic deformability (bendability), the plate members 22 also preferably have a thickness in the range of 0.5 to 3.0 mm. Note that instead of the illustrated example in which the plate members 22 abut against the pair of inner wall surfaces 12e, they can also abut against the other pair of inner wall surfaces 12d.

The length dimension L2 of the plate member 22 is such that when the vertical lattice handrail 10 is exposed to wind and the wind blows through between the balusters 12 of the vertical lattice handrail 10, causing the balusters 12 to vibrate in one or more of the primary vibration mode (Figure 4(b)), secondary vibration mode (Figure 4(c)) and tertiary vibration mode (Figure 4(d)) the plate member 22 can abut against the inner wall surface 12e of the handrail 12 at the amplitude peak points, which are the tops of the mountains or the bottoms of the valleys of the vibrations that occur (the one peak P1 in the primary vibration mode, the two peaks P2 and P3 in the secondary vibration mode, and the three peaks P4 to P6 in the tertiary vibration mode). The reason why this is defined as when the lattice structure 10 is hit by wind and each balusters 12 vibrates in one or more of the primary, secondary, and tertiary vibration modes is because the wind speed (wind velocity) that normally acts on the lattice structure 10 is in the range of 5 to 15 m/s, and within this wind speed range, the vibration of each balusters 12 is in one or more of the primary to tertiary vibration modes.

In the illustrated example, the amplitude of one peak P1 in the vibration of the primary vibration mode is located at a distance from the upper end 12a and lower end 12b of the balusters 12 that corresponds to 6/12 = 1/2 of the length dimension L2 of the balusters 12 (see Figure 4(b)), i.e., at the center position in the longitudinal direction of the balusters 12. Furthermore, the amplitude of two peaks P2 and P3 in the vibration of the secondary vibration mode are located at distances from the upper end 12a and lower end 12b of the balusters 12 that correspond to 3/12 = 1/4 of the length dimension L2 of the balusters 12 (see Figure 4(c)), respectively. Furthermore, of the three peaks in the amplitude of the vibration in the tertiary vibration mode, two peaks P4 and P6 are located at a distance equivalent to 2/12 = 1/6 of the length dimension L2 of the balusters 12 (see Figure 4(d)) from the upper end 12a and lower end 12b of the balusters 12, respectively, and the remaining peak P5 is located at a distance equivalent to 6/12 = 1/2 of the length dimension L2 of the balusters 12, i.e., at the center position in the longitudinal direction of the balusters 12.

In the illustrated example, the three spring members 24 of the wind noise reduction device 14 consist of two spring members 24 located near both ends of each plate member 22, and one spring member 24. The one spring member 24 is located midway between the two spring members 24, i.e., at the center in the longitudinal direction of the handrail 12 (see Figure 4(b)). The illustrated spring member 24 consists of a compression coil spring, and is fixed to both plate members 22 at both ends 24a. The two plate members 22 are thus connected to each other via the three spring members 24.

The wind noise reduction device 14 can be inserted into the interior of the balusters 12 used to manufacture the vertical lattice handrail 10 from one of the upper and lower ends 12a, 12b of the balusters 12 by pressing the pair of plate members 22 toward each other and compressing the multiple spring members 24 between the plate members 22, thereby allowing it to be placed inside the balusters 12. Inside the balusters 12, the plate members 22 are subjected to a pressing force, which is the elastic return force of the multiple compressed spring members 24, and come into contact with the inner wall surfaces 12e of the balusters 12, respectively, and are placed in close contact with the inner wall surfaces 12e of the balusters 12.

When a vertical lattice handrail 10 equipped with multiple balusters 12 fitted with wind noise reduction devices 14 is subjected to wind, the balusters 12 vibrate in one or more of the primary, secondary, and tertiary vibration modes. When the balusters 12 undergo elastic deformation (curving) in response to this vibration, the plate members 22, which are in close contact with the inner wall surfaces 12e of the balusters 12, receive external forces from the balusters 12 due to their elastic deformation and elastically deform along the curved inner wall surfaces 12e of the balusters 12. At this time, the plate members 22 vibrate around the spring members 24 as fulcrums and slide slightly on the inner wall surfaces 12e of the balusters 12. As a result, friction occurs between the inner wall surfaces 12e of the balusters 12 and the plate members 22. This friction dissipates the vibration energy of the balusters 12, reducing the vibration of the balusters 12 and the associated wind noise.

In the illustrated example, the length L2 of the plate members 22 is set to 10/12 of the length L1 of each balusters ( FIG. 4(a) ), and the upper and lower ends 12a, 12b of the plate members 22 are spaced 1/12 of the length L1 of the balusters 12 from the upper and lower ends 12a, 12b of the balusters 12, respectively. According to the illustrated example, even if the wind noise reduction device 14 slides down the inside of the balusters 12 to the lower ends 12b of the balusters due to its own weight when the balusters 12 vibrate, both plate members 22 remain in contact with the inner wall surfaces 12e of the balusters 12 at the peak P1 of the primary vibration mode, the two peaks P2 and P3 of the secondary vibration mode, and the three peaks P4, P5, and P6 of the tertiary vibration mode.

Figure 5 shows a graph of the results of wind tunnel testing of three vertical lattice handrails conducted to verify the effectiveness of wind noise reduction by the wind noise reduction device 14. Each vertical lattice handrail has 22 balusters 12 with a rectangular cross section, and these balusters 12 are spaced 25 mm apart. The wind tunnel testing was conducted by blowing wind at a speed of 5 to 15 m/s, which is equivalent to everyday wind, from the front to the back of each vertical lattice handrail.

In the figure, one vertical lattice handrail to which a wind noise reduction device 14 is not attached is labeled "No measures." Furthermore, two vertical lattice handrails to which a wind noise reduction device 14 is attached are labeled "Measures applied (1 mm)" and "Measures applied (2 mm)," respectively. The 1 mm and 2 mm in parentheses indicate the thicknesses of the plate members 22 of the wind noise reduction device 14, respectively.

The balusters 12 of the vertical lattice handrail are made of extruded aluminum. The widths of the outer wall surfaces 12c and 12d of the vertical lattice handrail are 30 mm and 15 mm, respectively, the length L1 is 1055 mm, and the thickness is 0.85 mm.

Each plate member 22 of the wind noise reduction device 14 is made of steel plate and has a width of 15 mm and a length L2 of 1000 mm. Each spring member 24 is made of piano wire (SWP-A) and has an outer diameter of 12 mm, a wire diameter of 1.2 mm, and a spring constant of 5.05 N/mm. The wind noise reduction device 14 is arranged in the same manner as shown in Figure 4(a).

The graph in Figure 5 shows that the A-weighted sound pressure levels for "with measures (1 mm)" and "with measures (2 mm)" are equal to or greater than the A-weighted sound pressure level for "without measures" at wind speeds of 6 m/s and 8 m/s, and are lower than the A-weighted sound pressure level for "without measures" at other wind speeds.

We then investigated the cause of this and found that at wind speeds of 6 m/s and 8 m/s, wind passing between the left support post 16 of the vertical lattice handrail 10 and the balusters 12 adjacent to said support post (see Figure 1) generates a whistling sound that is different from the structure-borne sound, and that this whistling sound increases the A-weighted sound pressure level.

From the above, it was confirmed that the A-weighted sound pressure levels for "measures applied (1 mm)" and "measures applied (2 mm)" were lower than the A-weighted sound pressure level for "no measures applied" at all wind speeds between 5 and 15 m/s, demonstrating the effectiveness of wind noise reduction.

10 Vertical lattice handrail 12 Baluster 14 Wind noise reduction device 22 Plate member 24 Spring members P1 to P6 Vibration peak points

Claims (7)

A wind noise reduction device applied to a lattice structure consisting of a handrail or fence having a plurality of hollow balusters with a rectangular cross section,
a pair of plate members facing each other and disposed inside each balusters, the pair of plate members extending in the extension direction of the balusters inside the balusters;
a plurality of spring members disposed between both plate members at intervals in the length direction of both plate members and fixed to both plate members, the plurality of spring members exerting a pressing force on both plate members inside each balusters so that both plate members abut against the inner wall surfaces of each balusters. 2. The wind noise reduction device according to claim 1 , wherein the plurality of spring members comprise two spring members located near both ends of each of the plate members, and one spring member located midway between the positions of the two spring members. 3. The wind noise reduction device according to claim 1, wherein the spring member is a compression coil spring. A balusters used in the manufacture of a lattice structure consisting of a handrail or fence,
a tubular member having a rectangular cross-sectional shape;
a pair of plate members facing each other and disposed inside the tubular member, the pair of plate members extending in the extension direction of the tubular member inside the tubular member;
a plurality of spring members disposed between the plate members at intervals in the longitudinal direction of the plate members and fixed to the plate members, the plurality of spring members exerting a pressing force on the plate members inside the tubular member so that the plate members each come into contact with an inner wall surface of the tubular member;
Both plate members have length dimensions that allow them to abut against the inner wall surface of the pipe member at the peak of the amplitude of the vibration that occurs when the lattice structure is exposed to wind and the pipe member vibrates in one or more of the primary vibration mode, secondary vibration mode, and tertiary vibration mode. 5. A balusters according to claim 4, wherein each of the plate members has a length dimension corresponding to 10/12 of the length dimension of the tubular member. 6. The handrail according to claim 5, wherein one and the other of the ends of each of the plate members are respectively arranged at a distance equivalent to 1/12 of the length dimension of the tubular member from one and the other of the ends of the tubular member. A lattice structure consisting of a handrail or fence having a plurality of balusters,
A lattice structure, each of which is made of a balusters according to any one of claims 4 to 6 .