JP2006342522A - Structure for preventing noise from generating from lattice structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To take exhaustively effective measures for suppressing the generation of vibrations and noises, against various phenomena as generation factors, making a lattice structure generate the vibrations and the noises, such as a Karman vortex, a separated flow and a lifting torsion moment. <P>SOLUTION: This structure has a stabilizer 16 which absorbs air transformation energy acting on a side surface of a lattice 14, and which adds weight, balanced with a lift force, to the lattice 14. The stabilizer 16 is fixed to the inside of the lattice in a position equidistant from supporting points at both the ends of the lattice. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lattice structure such as a handrail lattice used in a balcony of a house, and more particularly, to a noise prevention structure that effectively suppresses vibration noise generated when wind strikes the lattice.

  In buildings, lattices are often used for balcony railings. Since the wind directly hits the balcony railing of the balcony, the phenomenon that the lattice vibrates and generates sound is inevitable.

Conventionally, measures against vibration and noise have been taken on the lattice of the balcony. For example, Patent Document 1 discloses that a vibration damping material is filled in a lattice. And as a vibration damping material, urethane foam or rubber has been proposed.
Patent Document 2 proposes to provide a weight inside the lattice.
Japanese Utility Model Publication No. 5-6087 Japanese Utility Model Publication No. 4-55930

  However, conventional vibration and noise countermeasure techniques are not performed after analyzing the behavior peculiar to the lattice structure caused by the wind. That is, even if it is called vibration noise in a bite, the mechanism leading to the generation is complicated and diverse. Actually, various kinds of physical phenomena are generated singly or in combination depending on conditions such as the wind direction and the wind speed, and as a result, vibration noise occurs. Conventionally, this point has been overlooked.

  According to the knowledge of the present inventor, at least three kinds of phenomena are factors in the phenomenon in which sound is generated when wind strikes the lattice structure. The phenomenon is a phenomenon in which a so-called Karman vortex is generated, a separation flow phenomenon, and a torsional moment due to lift.

A phenomenon that causes generation of vibration noise will be described with reference to FIG.
FIG. 12A is a diagram for explaining Karman vortices. The Karman vortex is a wind vortex generated mainly by the wind from the front direction of the lattice 1. In FIG. 12A, the arrows indicate the direction of air flow by the wind. When the air flow hits the grid or passes between the grids, an air flow vortex is created on the rear side of the grid. This vortex is called Karman vortex. When the Karman vortex coincides with the natural frequency of the lattice and the lattice resonates, a vibrational radiated sound is generated. Conventionally, it is known to those skilled in the art that noise generated in a handrail lattice is caused by Karman vortices.

  Next, FIG.12 (b) is a figure explaining the generation | occurrence | production mechanism of peeling flow. The separation flow is mainly caused by wind blown from an oblique direction with respect to the front of the lattice. That is, when wind strikes the grid from an oblique direction, the air flow is separated into two hands from the corners of the grid. Then, vibrations based on fluctuations in the variable pressure are generated on the side surfaces of the lattice due to the overlap of the separated wind and are heard by human ears as noise.

  Finally, FIG. 12 (c) is a diagram illustrating a mechanism for generating a lift torsional moment. This is a phenomenon in which vibration occurs due to fluctuations in the amplifying force of the torsional moment that acts on the lattice in response to wind. When the wind is received from the front, only the drag acts in the direction of the wind, but when the wind is received in the oblique direction, the force acting on the lattice can be divided into two components of drag and lift. Of these, the lifting force adds a twisting moment to the lattice. And the vibration is increased by the amplification force due to the torsional moment, which causes noise.

  As described above, the phenomena that cause the noise generated in the lattice structure include Karman vortices, separated flow, and the torsional moment of lift, and the actual noise is generated by the complex entanglement of these phenomena. It can be said that.

  In this regard, conventionally, the noise phenomenon has been grasped easily, and depending on the conditions, it may be effective in generating sound or may be hardly useful. In reality, in many cases, the noise suppression caused by the Karman vortex is still at a stage where a certain degree of suppression effect can be obtained.

  Therefore, the object of the present invention is to solve the problems of the prior art and cover various phenomena that cause vibration noise in the lattice structure such as Karman vortex, separation flow, and lift torsional moment. An object of the present invention is to provide a structure for preventing the noise of a lattice structure that can effectively take measures for suppressing the generation of vibration noise.

  In order to achieve the above object, the present invention provides a noise preventing structure for suppressing vibration noise caused by wind generated in a lattice structure in which metal lattices having a rectangular hollow cross section are arranged at regular intervals. A stabilizer that absorbs air transformation energy acting on the side of the grid and adds a balance weight to the lift to the grid, and the stabilizer is positioned at equidistant positions from fulcrums at both ends of the grid. It is characterized by being fixed inside.

  According to the present invention, vibration noise generation suppression measures effective for any phenomenon such as Karman vortex, separation flow, lift torsional moment, and other phenomena that cause vibration noise in the lattice structure. Can be taken.

Hereinafter, an embodiment of a structure for preventing noise from a lattice structure according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a handrail grid to which the present invention is applied. On the left and right pillars 10 and 11, a headboard 12 and a lower trunk edge 13 are attached in parallel in the vertical direction to constitute a frame of a lattice structure. Between the headboard 12 and the lower trunk edge 13, a lattice 14 is bridged in parallel at a constant interval. The grid 14 is a metal grid having a rectangular cross section, and the grid itself is a mold material generally used for this type of handrail grid.

As shown in FIG. 2, a stabilizer 16 is mounted inside the grid 14. FIG. 3 shows a cross section of the stabilizer 16.
The stabilizer 16 is a square bar member having a cross section corresponding to the cross section of the lattice 14. The stabilizer 16 is mounted so as to be in close contact with the inner wall surface of the lattice 14. As a material of the stabilizer 16, a polymer viscoelastic material, for example, a rubber-based material is ethylene propylene rubber (EPDM) or ritryl rubber (NBR). And it adjusts so that specific gravity may have about 1.4.

  In the present embodiment, the length of the main body of the stabilizer 16 is approximately 1/6 of the entire length of the lattice 14. The stabilizer 16 is positioned inside the lattice as follows, and the side surface of the stabilizer 16 main body is brought into close contact with the inner wall surface of the lattice 14.

As shown in FIG. 3A, a through hole 17 penetrating the center is formed in the length direction in the main body of the stabilizer 16. Further, a concave portion 15 is formed in the length direction on one side surface of the stabilizer 16, and a pair of projecting portions 19 a and 19 b protruding from the inner wall surface of the lattice 14 is formed in the concave portion 15. In the concave portion 15 of the stabilizer 16, a ridge 18 that fits into the protruding portions 19 a and 19 b is formed. And as shown in FIG.3 (b), the rod 20 with a diameter larger than the hole diameter is inserted in the through-hole 17 of the stabilizer 16. As shown in FIG. The rod body 20 allows the 16 main bodies of the stabilizer to be expanded, and the side surfaces thereof can be brought into close contact with the inner wall surface of the lattice 14.
The sounding prevention structure of the lattice structure according to the present embodiment is configured as described above, and the operation thereof will be described next.

  The reason why noise such as noise is generated by the wind hitting the lattice structure is basically caused by vibrations in the lattice 14.

Therefore, in the present invention, by providing the stabilizer 16, the vibration generated in the grating 14 is attenuated as follows.
As shown in FIG. 4, in the case of a lattice structure such as a handrail lattice, each lattice can be modeled as the behavior of a rod with pins supported at both ends (FIG. 4 (a)). It is thought that the movement that bows like a bow is vibration. As shown in FIGS. 4B to 4D, the vibration mode includes a primary vibration mode, a secondary vibration mode, and a tertiary vibration mode. In the case of a structure such as a handrail lattice, the primary vibration mode is mainly used. Mode vibration is occurring. Since the amplitude is related to the noise level, reducing the amplitude leads to an improvement in noise reduction.

  Therefore, when the stabilizer 16 is provided in the lattice 14, as shown in FIG. 5, the vibration generated in the lattice 14 can be considered in parallel with the vibration of the physical pendulum. In this case, the upper and lower ends of the lattice 14 are fixed ends which are fulcrums, respectively. The moment of inertia is greatly related to the suppression of the amplitude, and this moment of inertia becomes smaller as the position of the stabilizer 16 is closer to the fulcrum, and becomes larger as the position away from the fulcrum. The greater the moment of inertia, the more effectively it works and the lower the amplitude speed, the better the position of the stabilizer 16 is the farthest from the fulcrum. However, in this case, when it is far from one fulcrum, it is close to the other fulcrum, so that it is preferable to attach it at an equal distance from the upper and lower fulcrum after all.

  In this way, the stabilizer 16 functions as a pendulum weight to attenuate the vibration of the grating 14. The damping effect in this case acts regardless of the cause of vibration noise generation.

  In the present embodiment, the function of the stabilizer 16 is not limited to the vibration damping function as a weight of the pendulum, but rather, as will be described below, a factor of vibration noise generation, that is, a phenomenon in which Karman vortex is generated, peeling It works individually for each factor of flow phenomenon and generation of torsional moment due to lift, and has a fundamental suppression effect by tracing back to the factor of vibration.

First, the Karman vortex will be described. As shown in FIG. 6, when the wind blown from the front direction passes between the lattices 14, Karman vortices are generated on the rear side of the lattices 14. However, the presence of the stabilizer 16 inside the grating 14 makes a certain portion of the stabilizer 16 heavy, and adds a time difference to the natural period with the other portions. As a result, the resonance with the Karman vortex is suppressed, so that resonance hardly occurs.
Next, FIG. 7 is a diagram for explaining the action of the stabilizer 16 with respect to the influence of the separation flow. The separation flow is likely to occur mainly when wind blown from an oblique direction hits the grid 1. That is, when the air flow is separated into two hands from the corners of the lattice 14, a pressure change is applied to the side surface of the lattice 14 due to the overlap of the separated wind, and this becomes the excitation force of the lattice 16. However, the stabilizer 16 in the lattice 14 absorbs the fluid transformation energy generated by the separated flow rapidly because it is a viscoelastic material, and attenuates the excitation force applied to the lattice 14. As a result, the transmission of the excitation force is reduced, and as a result, the amplitude of vibration due to the separated flow is reduced.

  Next, the action of the stabilizer 16 on the lift torsional moment will be described with reference to FIG. The lift torsion moment tends to occur mainly when the wind is received in an oblique direction. At this time, if the force acting on the lattice 14 is divided into two component forces of drag and lift, the lift adds a twisting moment to the lattice 14. However, since the stabilizer 16 is provided inside the lattice 14, the stabilizer 16 adds a balance weight that reduces the lift force. Therefore, the lift force is reduced to suppress the action of the torsional moment, and the amplitude is reduced.

  As described above, the stabilizer 16 has a function of individually suppressing the amplitude of the cause of vibration for each of the phenomenon of the Karman vortex generation phenomenon, the separation flow phenomenon, and the generation of the torsional moment due to the lift force. It is effective in suppressing the wind noise of the lattice under various conditions.

  Next, a description will be given of test results obtained by conducting a wind tunnel test on an example of the structure for preventing noise generation of the lattice structure according to the present invention.

  In the examples, the present invention was applied to three types of lattices having different cross-sectional dimensions (18 × 18 lattice, 24 × 20 lattice, 40 × 22 lattice (unit mm)).

The stabilizer was prepared by using EPDM (specific gravity 1.4) as a material and having a lattice length of 1/6, and was mounted at a position 1/2 the material length.
9 (a) to 9 (c) show the noise generated by the wind tunnel test while changing the wind direction and the wind speed for the lattice structure in which the stabilizer is mounted on the 18 × 18 lattice, 24 × 20 lattice and 40 × 22 lattice, respectively. The measurement results are shown.

  10A to 10C are comparative examples, and the noise was measured under the same conditions for a lattice structure without a stabilizer in an 18 × 18 lattice, a 24 × 20 lattice, and a 40 × 22 lattice, respectively. Indicates. In these figures, ◯, ●, ◎, ☆, and ★ indicate the magnitude of noise in order.

  As is clear from comparison between the wind tunnel test of the example and the comparative example, it can be seen that a noise reduction effect can be obtained by mounting the stabilizer on the grid.

  Next, it will be examined whether the noise reduction effect is effective for the Karman vortex phenomenon, the separation flow phenomenon, and the generation of the torsional moment due to the lift.

  First, since the Karman vortex has a feature that it tends to be generated by the wind direction from the front, in FIGS. The vibration noise generated in the range shown is considered to be mainly caused by Karman vortices. On the other hand, in the embodiment, as shown in FIGS. 9A and 9B, no vibration noise is generated under the same conditions. Therefore, by installing the stabilizer inside the lattice, the Karman vortex It can be seen that the noise suppression effect resulting from the above can be obtained.

  Next, the vibration noise caused by the torsional moment due to the separation flow and the lift is likely to occur when the wind direction is oblique, so that in FIGS. 10 (a) to 10 (c), C, D, The vibration noise generated in the range indicated by E is considered to be vibration noise generated due to the torsional moment due to the separation flow and the lift force, and these factors combined to increase the vibration.

  On the other hand, in FIG. 9A of the example, the noise that was in the range of C in FIG. 10A of the comparative example is lost, and FIG. 9B and FIG. In c), the ranges F and G in which vibration occurs are limited to narrow ranges as compared to the noise generation regions D and E in the comparative example. From this result, it can be seen that by mounting the stabilizer inside the lattice, there is also an effect of suppressing vibration noise caused by the torsional moment due to the separation flow and the lift force.

  FIG. 11 is a graph further demonstrating that the example has an effect of suppressing vibration noise caused by the torsional moment due to the separation flow and the lift force.

  FIG. 11 is a graph showing the results of measurement of vibration acceleration on a 24 × 20 grid under conditions of a wind direction angle of 75 ° and a wind speed of 14 m / s. According to FIG. 10B, the wind direction angle of 75 ° and the wind speed of 14 m / s are conditions in which vibration noise caused by the torsional moment due to the separation flow and the lift is likely to occur. In FIG. 11, the upper row shows the measurement results for the lattice without the stabilizer, and the lower row is an example in which the stabilizer is attached. From this result, it can be seen that the vibration is remarkably reduced by clearly mounting the stabilizer.

The perspective view of the handrail lattice to which the present invention is applied. The side view which shows the attachment position of the stabilizer attached to the handrail lattice. The cross-sectional view of the handrail lattice. Explanatory drawing which modeled the vibration of the lattice. The figure which represented typically the vibration of the lattice with a stabilizer as a physical pendulum. The figure explaining the effect | action of the stabilizer with respect to Karman vortex. The figure explaining the effect | action of the stabilizer with respect to a separation flow. The figure explaining the effect | action of a stabilizer with respect to a lift twist moment. The graph which shows the measurement result of the vibration noise which concerns on the Example of this invention. The chart which shows the measurement result of vibration noise about the comparative example which does not use a stabilizer. The graph which shows the measurement result of the vibration acceleration which concerns on the Example of this invention. Explanation of the cause of wind noise in the lattice

Explanation of symbols

10 pillars 11 pillars 12 coping 13 lower trunk edge 14 lattice 16 stabilizer 17 through-hole 20 rod

Claims (6)

A noise prevention structure for suppressing vibration noise caused by wind generated in a lattice structure in which metal lattice bodies having a rectangular hollow cross section are arranged at intervals,
A stabilizer that absorbs air transformation energy acting on the side surface of the grid and adds a balance weight to lift to the grid, and the stabilizer is placed at an approximately equidistant position from the fulcrums at both ends of the grid. A structure for preventing the sound of a lattice structure that is fixed.   2. The structure according to claim 1, wherein the stabilizer is made of a polymer viscoelastic material that adheres to an inner wall surface of the lattice and absorbs air-transforming energy.   The structure according to claim 2, wherein the polymer viscoelastic material is made of a rubber material and has a specific gravity of approximately 1.4.   The structure according to claim 3, wherein the rubber-based material is made of ethylene propylene rubber (EPDM) or ritryl rubber (NBR).   The main body of the stabilizer has a length approximately 1/6 of the entire length of the lattice, and includes means for positioning the main body inside the lattice and closely attaching the side surface of the main body to the inner wall surface of the lattice. The structure for preventing sounding of the lattice structure according to claim 1.   The main body of the stabilizer has a through hole penetrating the center in the length direction, and a rod body having a diameter larger than the hole diameter is inserted into the through hole, whereby the main body is expanded and the side surface of the stabilizer is 6. The structure for preventing noise from being produced by a lattice structure according to claim 5, wherein the structure is in close contact with an inner wall surface.

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