NZ234851A - Pendulum type dynamic damper for controlling building vibrations - Google Patents

Description

FORM t.'EW ZEALAND * S.9* RecIl9U) Fee:' $200 234 8! Compete Specification rile-.: Class: j.RZ.y... .fcCUtd^lolr...

PuhHcatisn Pr*e: .. P.O. Joiwnai, He: , PATENTS A Insert number of Frcvisicr.il Scecifieaticn(s) (if any) and date(s) of fUir,:; otherwise leave fciar.k.

Number: Date: COMPLETE SPECIFICATION v ... !. , , r O AUG!990ri Insert Title of Indention. . ■ ; nsert full n a -=, full si reet address ; '"'-and; nsiior.ality cf • •(.each) applicant.

DYNAMIC DAMPER I/V.'E MITSUBISHI JUKOGYO KABUSHIKI KAISHA of 5-1, Marunouchi 2-chome, Chiyoda-ku, Tokyo, Japan, a Japanese Corporation ! • hereby declare the invention for which I/we pray that a patent may be granted to me/us and the method by which it is to be performed, to be particularly described in and by the following statcment:- The following page is numbered "la" Indicate if fcllcning psge is r.urtere'd 11 (a)1 .12.83 • 234 85 SPECIFICATION 1. FIELD OF THE INVENTION AND RELATED ART STATEMENT The present invention relates to a dynamic damper which is used for controlling the vibration of a tower or a towerlike structure, such as steel towers and observation towers, and high-rise buildings.

Previously, as shown in FIG. 12, a dynamic damper has comprised a weight 1 and suspension members 2 and a damper 8 and, if necessary, a spring 9 and has been attached directory to a structure 7. This is what is usually called single suspension (or single-stage suspension), and its period has been adjusted by changing the length of the suspension members. 1 In this damper, no mechanisms have been provided for ""V, moderating shocks to the floor in case the suspension members break and the weight falls.

The conventional dynamic damper has the following problems: (i) In order to make the period of pendulum motion longer in the prior art method, the length of the suspension members (the length of the pendulum) becomes long, and there i'" - ia - has been problems with available space (in vertical directions, in particular). For example, if the period is 6 seconds the length of the pendulum would have to be 9 meters. This length corresponds to the height of three stories in an ordinary high-rise building. This means that the space corresponding to three stories is occupied simply by a conventional dynamic damper and by nothing else. (ii) As a method for adjusting the frequency of the pendulum, the length of the pendulum can be changed to get a desired frequency, if oscillation is only in one direction. However, if the periods are different in two directions, the periods cannot be adjusted well by simply changing the length of the pendulum. (iii) In the prior art damping method, a spring with the stroke of the same length as the amplitude of the pendulum motion is required. For example, if the amplitude of the oscillation is 1.2 meters, the stroke of the spring has to be ±1.2 meters (+ for stretch and - for compression). (iv) Also, the stroke of a damper has to be the same as the amplitude of the pendulum motion with the conventional method. (v) In the conventional method, the period of the pendulum has been adjusted by changing the length of the suspension members, and thus a number of suspension members with different lengths have been necessary. Also, changing the suspension members has taken much of time and efforts, and fine adjustments have been difficult to make. (vi) The weight in a pendulum type dynamic damper is suspended by suspension members. Should the members break and the weight fall down, the impact to the floor can be very large, and it is quite possible for the weight to penetrate the floor. Also, most of the weight of a dynamic damper is concentrated in the weight, and special procedures are required for holding the weight at the time of installation or during maintenance or at similar occasions. (vii) When changing the height of a suspension frame or that of the suspended weight, the setting of a damper and a spring could become difficult. Often the heights of these components become uneven and the overall appearance is spoiled. (iix) If only the length of the suspension members is shortened in order to make the period of the pendulum shorter, an inner suspension frame might come into contact with an outer suspension frame. This limits the range of adjusting the period. Also, in order to make the period longer, the height of suspension of a suspension frame may become uneven, and the setting of a damper and a spring also may become difficult.

Furthermore, when a dynamic damper for controlling vibrations are constructed as shown in FIG. 16, there are 234 8 o another set of problems. In FIG. 16, numeral 71 indicates an weight. This weight is suspended from a suspension frame 3 through a suspension member 79 which does not have flexural rigidity. In addition, this suspension frame 73 is suspended from a structure through a suspension member which also does not have flexural rigidity. Dampers 76 are disposed between the structure 74 and the lower end of the suspension frame 73 and between the weight 71 and the lower end of the suspension frame 73. Springs are disposed, if necessary, between the structure 74 and the lower end of the suspension frame 73 and between the weight 71 and the lower end of the suspension frame 73.

When the structure 74 vibrates, the vibration of the structure 74 is transmitted to the weight 71 through the dampers 76 and the springs 77 and the suspension frame 73, and the weight also vibrates. The vibration of the structure 74 is controlled due to this vibration of the weight 71.

With this type of dynamic damper shown in FIG. 16, the weight and the suspension frame vibrate very much since the action points of the dampers and the springs are located at the lowest portion of the suspension member; 79. Therefore, the dampers 76 and the springs 77 have to have a relatively long stroke. 234 85 Still furthermore, in a conventional dynamic damper, an oil damper with a damping force which is proportional to the velocity has usually been used.

For a conventional dynamic damper which uses an oil damper whose damping force characteristic is more or less proportional to the velocity, the ratio between the oscillation amplitude of a weight and the oscillation amplitude of a structure in which the dynamic damper is placed is constant and independent of the amplitudes. Also, the damping is more effective if the ratio of the oscillation amplitude of the weight to that of the structure is larger.

Recently, in order to improve the comfortability of high-rise buildings, a dynamic damper which is capable of reducing structural oscillations whose amplitude is about 10cm and which can be caused by rather ordinary winds having a velocity of around 10-20m/sec has become necessary. For this purpose, however, a large value is required for the ratio of the oscillation amplitude of a weight to that of the structure: for example, the ratio is designed to be 5-6. In such a case, if a conventional oil damper whose damping force characteristic is proportional to the velocity is used, because this ratio between the oscillation amplitudes of the weight and structure is constant, the amplitude of the weight may become very large. For example, the oscillational amplitude of a building may become lm if strong earthquakes •j I « i J f I 23 A 85 or strong winds of more than 40rn/sec hit the structure, and the amplitude of the weight may become almost 5-6m. Such large amplitudes cannot normally be allowed. To cope with this problem, a stopper is usually used to limit the amplitude of the weight to l-2m. However, large impacts to the stopper are transmitted to the building and cause problems. 2. OBJECT AND SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a compact dynamic damper.

Another object of the present invention is to provide a dynamic damper using damping devices, such as dampers and springs, with shorter strokes.

The dynamic damper of the present invention for controlling vibrations of a tower or a tower-like structure can be summarized as we shall describe below. (1) In a pendulum type dynamic damper for controlling vibrations comprising a weight, a spring, a suspension member and an attachment frame, the dynamic damper of the present invention is characterized in that an upper suspension frame and a lower suspension frame are disposed between the attachment frame and the weight, the upper and the lower suspension frame are rectangular in shape, and the upper suspension frame, the lower suspension frame are connected by four jonnection members so as to form a multistage suspension of the weight, and a certain angle is provided between the upper and the lower suspension frame so that the suspension members do not overlap each other. (2) The dynamic damper as described in (1) above, which is further characterized in that a spring for adjusting the frequency of pendulum motion is disposed between the suspension frames. (3) The dynamic damper as described in (1) above, which is further characterized in that a damper is disposed between the suspension frames. (4) The dynamic damper as described in (1) above, which is further characterized in that a spring for adjusting the frequency of pendulum motion and a damper are disposed between the suspension frames. (5) The dynamic damper as described in any of (2) to (4) above, which is further characterized in that a spring for adjusting the frequency of pendulum motion or a damper are also disposed between the suspension frame and the weight. (6) The dynamic damper as described in any of (2) to (4) above, which is further characterized in that a spring for adjusting the frequency of pendulum motion and a damper are also disposed between the suspension frame and the weight, (7) The dynamic damper as described in any of (1) to (6) above, which is further characterized in that a horizontal support device for the suspension member is disposed for adjusting the frequency of pendulum motion. (8) The dynamic damper of the present invention comprises a structure whose vibration is to be controlled, a plurality of first suspension members which are supported rotatably at their one end by the structure and which have flexural rigidity, a suspension frame which is supported rotatably by the other end of the suspension frames, a plurality of second suspension members whose one end is supported rotatably by the suspension frame and whose other end is supported rotatably by the weight, means for varying strokes which are disposed near the upper end of the first suspension member between the first suspension member and the structure and also near the upper end of the second suspension member between the second suspension member and the suspension frame. (9) In a dynamic damper comprising an oscillating system and an oil damper, the dynamic damper of the present invention is characterized in that an oil damper whose damping force becomes proportional to the square of the velocity above a certain velocity level is used. In the 234 85 1 present invention, in order to automatically control large amplitude oscillations which occur in the events of a strong earthquake or a strong wind, an oil damper is used whose damping force becomes proportional to the square of the velocity when the velocity becomes larger than a certain value.

The dynamic damper of the present invention for controlling vibrations of a tower or a tower-like structure as described above has the following functions. (a) The period of the pendulum with the multistage suspension is approximately the same as that of a conventional pendulum whose length is the sum of pendulum lengths in all stages in the multistage suspension. (b) Also, with the addition of a spring, the frequency of the pendulum can be changed without varying its length. (c) In general, the amplitude of pendulum motion at one stage in an n-stage suspension is about 1/n of the amplitude of a conventional pendulum. (d) When dampers are disposed between the suspension frames, the stroke of each damper can therefore be 1/n compared to a conventional pendulum. (e) By holding the middle of a suspension member with a horizontal support piece and constraining the horizontal disposition of the suspension member, the portion of the suspension member below this holding point will not 234 85 contribute to the length of the pendulum. Only the portion above the holding point contributes to the effective length of the pendulum. (f) If pillars on the under side of the weight are disposed so that they almost graze, but do not touch, the floor surface, even if the weight should fall to the floor, the impact to the floor will be considerably smaller because the falling distance is very short. (g) Since each end of the suspension members and the connection portions between the suspension frames and the weight can be made to slide in the vertical direction in the dynamic damper of the present invention, the holding position of the suspension members may be changed. Furthermore, turnbuckles or the like can be disposed on the suspension members so that the length of the suspension members themselves may be varied. The period of pendulum motion can therefore be adjusted by changing the length of the pendulum without changing the vertical position of the weight. This can be done by absorbing changes in the length of the suspension members with the above slide mechanism. (h) By adjusting the length of the suspension members, the length of the pendulum can be changed. At the same time, collisions between the suspension frames and unevenness among the positions of the suspension frames may be avoided by stretching or contracting the suspension frames 234 85 1 (i) The dynamic damper as described in (8) above uses damping devices, such as dampers and springs, with shorter strokes. (,j) According to the present invention constructed as (9) above, if the amplitude becomes larger than a certain velocity level, the damping constant of the dynamic damper increases, and the ratio of the oscillational amplitude of the weight to that of the structure decreases as the amplitude of structural oscillation increases so that the amplitude of the weight in the dynamic damper can be reduced. 3. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a first embodiment of the present invention; FIG. 2 shows a second embodiment of the present invention; FIG. 3 shows a third embodiment of the present invention; FIG. 4 shows a fourth embodiment of the present invention; FIGS 5 to 7 show a fifth embodiment of the present invention; FIG. 8 shows a sixth embodiment of the present invention; 234 85 FIG. 9 shows a seventh embodiment of the present invention; FIGS. 10 and 11 show a eighth embodiment of the present invention; FIG. 12 shows a conventional apparatus; FIG. 13 shows a ninth embodiment of the dynamic damper of the present invention; FIG. 14 shows how the apparatus of the above embodiment operates; FIG. 15 shows a tenth embodiment of the present invention; FIG. 16 shows a dynamic damper with the suspension members which do not have flexural rigidity; FIG. 17 shows a side view of a eleventh embodiment of the present invention; FIG. 18 shows a plan of the same; FIG. 19 shows a relation between the oscillational amplitudes of the weight and the building as well as a relation between the oscillational amplitude of the structure and the added damping to a building; FIG. 20 shows a characteristic graph of an oil damper; and FIGS. 21 to 25 show other embodiments of the present invention. 234 8 4. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Embodiments of the present invention are shown in FIGS. 1 to 11.

FIG. 1 shows a first embodiment of the present invention. This has a three-stage two-point suspension structure. The oscillation is constrained in one direction •J^ (the x-axis direction in FIG. 1).

In FIG. 1, numeral 1 indicates a weight, numerals 2, 3 and 4 suspension members, numerals 5 and 6 upper suspension frames, numerals 5a and 6a connection members, numerals 5' and 6' lower suspension frames, 7 a structure (or an attachment frame), numeral 8 a damper, and numeral 9 a spring.

The weight 1 is suspended from the upper suspension frame 5 through the suspension member 2. The upper suspension frame 5 is in a horizontal position. The connection member 5a, which is quite rigid, is disposed on each end of the upper suspension frame 5 so as to hang down from the frame. The lower suspension frame 5' is suspended from the upper suspension frame 6 through the suspension members 3. The upper suspension frame 6 is in a horizontal position. The connection member 6a is disposed on each end of the upper suspension frame 6 so as to hang down from the frame 6, and the lower suspension frame 6' is disposed. The - 13 234851 lower suspension frame 6' is suspended from the structure 7 (or the attachment frame) through the suspension members 4.

The height of attachment portion of the connection "S member 5a and 6a to the suspension members is about the same as that of the attachment portion of the weight 1 to the suspension members 2 so that the z-direction components of the suspension members 2, 3, 4 mostly overlap each other. Also, a stopper (not shown) is disposed so as to constrain the motion of the upper suspension frames 5, 6 in the y-axis direction, which is perpendicular to the xz plane in FIG. 1.

If the lengths of the suspension members are 11, 12, and 13, the period T of the first embodiment is given by: T * 2n{(ll+12+lZ)/g}1f2 , where g is the acceleration of gravity.

In the conventional dynamic damper shown in FIG. 12, the length of the pendulum 1 is required to be 1 - 11+12+13. Therefore, if _Z1 = 2m, 22 = 3m, and 13 = 4m, 1 is equal to 9m. The period T would then be: T « 2n{(2+3+4)xl00/980}1/2 = 6.02 sec.

On the other hand, the length of each suspension member is not more than 4m. This is less than a half of 9m with the n conventional dynamic damper. Thus, the height of the space J required to place the dynamic damper of this embodiment can be reduced to 4m in the case where the conventional type requires 9m. 23 4 85 ■ FIG. 2 shows a second embodiment of the present invention which is a three-stage four-point suspension system.

According to this embodiment, as shown in FIG. 2, the suspension members 2, 3, 4 and the upper suspension frames 5, 6 are staggered by a 45° rotation so that the levels of the upper suspension frames 5, 6 can be held in a single horizontal plane, and the height of the required space can be smaller. The apparatus of this embodiment works as a damper against horizontal vibrations in all directions.

The period T of the apparatus of the second embodiment is given by Equation (1) below, if the lengths of the suspension members 2, 3, 4 are given by 21, 22, and 23, respectively.

T ~ 2n{( 21 + 22 + 23)/*}W2 , (1) where g is the acceleration of gravity.

If 21 = 22 = 23 = 3m, the period of the pendulum is, according to Equation (1), 6.02 sec. This corresponds to a conventional pendulum of single suspension with the length of 9m. With this second embodiment, the length of the pendulum can be divided into three parts and reduced to one third, which is 3m in this case.

FIG. 3 shows a third embodiment of the present invention which is a three-stage four-point suspension system with springs. 234 85 According to the third embodiment, as shown in FIG. 3, the suspension members 3, 4 and the upper suspension frames 5, 6 are staggered by a 45' rotation (see FIG. 3(b)) so that the levels of the upper suspension frames can be in a single plane, and the height of the required space can be reduced. The apparatus of this embodiment works as a damper against oscillations in any horizontal direction. In order to adjust the frequency in each directional component, springs 9, 10 are disposed between the weight 1 and the lower suspension frames 5', 6'.

If the lengths of the suspension members 2, 3, 4 are given by 21, 12 and 13, respectively, and if the spring constants of the springs are given by Ax and Ky , the period of the pendulum shown in FIG. 3 can be calculated by the following equation: Tx * 2n (Mb*/-fox* )x/2 , Ty « 2rc( M>*/flby* )1' 2 , (2) where Tx and Ty are the period of the pendulum in the x and y directions, respectively, A/b* is the mass of the weight, Kdx* = ffit + (Wb" -g)/l, Ko y* = JTy + («b* 'g)/l, 1 = 11 + 12 + 13, and g is the acceleration of gravity.

If we take il = 22 = i3 = 3m, Md* = 102kg • sec2/cm, Kx = 50kg/cm, Ky = lOOkg/cm, Equation (2) gives the values for Tx and Ty as follows: Knx* = 50+102x980/900 = 161.1kg/cm, Kby* = 100+102x980/900 = 211.1kg/cm, and thus Tx « 2h(102/161. I)1'2 » 5 sec, Ty « 2tt{ 102/211 . 1 J1 / 2 » 4.4 sec.

Also, if the amplitude of oscillation of the conventional type is 1.2m, the oscillation amplitude of each pendulum in this embodiment is given by: 1.2m x 1/3 = 0.4m. Therefore, the required stroke of the spring is also a third of the conventional type: if ±1.2m with the conventional type, it would be ±0.4m with this embodiment.

FIG. 4 shows a fourth embodiment of the present invention which is a three-stage four-point suspension system with springs and dampers. The apparatus of this embodiment functions as a damper against vibrations in all directions in a horizontal plane. In order to adjust the frequency of each directional component, springs 9, 10 are disposed between the lower suspension frames 5', 6' and the weight 1.

Also, dampers 8, 11 are disposed between the lower suspension frames 5', 6' and the weight.

If the amplitude of the pendulum of conventional type (shown in FIG. 12) is 1.2m, the amplitude of the pendulum according to the present invention can be 0.4m or a third of the conventional type. Therefore, while a large damper with a stroke of ±1.2m is required with the conventional type, the apparatus according to the present invention shown in FIG. 4 requires a damper with a stroke of ±1.2m x 1/3 = ±0.4m because it is a three-stage suspension. 234 85 FIGS. 5 to 7 show a fifth embodiment of the present invention.

FIG. 5(a) shows an embodiment of a two-stage suspension ^ pendulum which comprises a weight 1, suspension members 2, 3, a suspension frame 5, horizontal support pieces 14 for the suspension members and support stages sticking out of the weight 1, Also, the horizontal support pieces 14 for the suspension members are held as shown in FIG. 5(b) if each of the suspension members 2, 3 is bundled up to one, and they are held as shown in FIG, 5(c) if each of the suspension members 2, 3 is made up of a plurality of lines. The horizontal support pieces 14 are held onto the support stages 12 and the suspension frame 5 with bolts so that they can be moved up or down. In addition, the suspension members are fixed by bolts 15 through metal pieces 16, 17 or 18, 19, 20, 21. In this case, the suspension members 2, 3 may be either completely fixed against metal pieces 14 or held only in the horizontal direction and left to be free in the vertical direction. jj jj ; FIG, 6 shows a variation of the embodiment shown in FIG.

II U " 5 in which the horizontal support piece 14 for the suspension ll members is divided into two so that the period of the pendulum can be adjusted for each of two directions in the plane of pendulum motion (x and y directions) independently of each other. 234 85 FIG. 6(a) shows only the suspension member 2 and the support piece 14 in FIG. 5. As shown here, the support piece 14 is divided into two pieces: X14 for the x direction and Y14 for the y direction. FIG. 6(b) shows the piece for the x direction. This piece X14 allows free motion in the x direction and constrains motion in the y direction. FIG. 6(c) shows Y14 for the y direction. This allows free motion in y direction, but constrains motion in the x direction.

Because of the horizontal support pieces 14 for the suspension members which are attached as shown in FIG. 5 and which constrain horizontal displacements of the suspension members 2, 3, the pendulum shows such a motion as shown in FIG. 7. The length 1 of the suspension members 2, 3 above the support piece 14 becomes the effective length of the pendulum, and the period which is realized corresponds to this length 1. Although only the motion of the weight 1 is shown in FIG. 7, the motion of the suspension frame 5 in FIG. 5 against the structure 7 is the same.

Also, in the embodiment shown in FIG. 6, by varying the positions (in the height direction) of the x-direction piece X14 and the y-direction piece Y14, the periods in the x and y directions can be changed independently.

FIG. 8 shows a sixth embodiment of the present invention which is a two-stage suspension pendulum comprising a weight 1, suspension members 2, 3, a suspension frame 5, pillars 34 and jacks 35. The suspension frame comprises an upper suspension frame and a lower suspension frame and connection members.

FIG. 9 shows a seventh embodiment of the present invention.

This embodiment is a double suspension pendulum which comprises a weight 1, suspension members 2, 3, turnbuckles 44 for varying the length of the suspension members, and slide mechanisms 45 between an end of the suspension member and the weight or the suspension frame. This slide mechanism is fixed to the weight or to the suspension frame with bolts 46. A number of bolt holes are disposed on the weight and the suspension frame at small intervals in the vertical direction so that fixing positions can be changed according to the desired length 1 of the suspension members.

It should be noted here that mechanisms for adjusting the effective length of the suspension members and therefore that of the pendulum and slide mechanisms are by no means restricted to the ones shown above as the embodiments of the present invention and can be replaced by any mechanism having similar functions.

The slide mechanism 45 and the turnbuckle 44 have similar variable ranges. If the length 1 of the suspension members is designed to be in the center of the variable range, 1 can be made either shorter or longer. If it is 234 8 5 1 necessary to make the period of the pendulum longer, turnbuckle is stretched to make 1 larger and, at the same time, the slide mechanism 45 is lowered by the same amount as the stretching of the turnbuckle. If it is necessary to make the period shorter, the turnbuckle 44 is contracted to make 1 shorter, and also the slide mechanism 45 is moved up by the same length as the contraction of the turnbuckle. With these procedures, the period can be adjusted without changing the suspension height L of the weight and the suspension frame.

FIGS. 10 and 11 show an eighth embodiment of the present invention.

The apparatus shown in FIG. 10(a) is a two-stage suspension pendulum which comprises a weight 1, suspension members 2, 3, suspension frames 5, 6, turnbuckles 54 and slide mechanisms 55 for contraction and stretching.

FIG. 10(b) shows a case in which the period of the pendulum is shortened. The lengths of the suspension members 2, 3 are made shorter by adjusting the turnbuckles 54, and the length of the suspension frames is also made shorter using the slide mechanisms 55.

FIG. 10(c) shows another case in which the period is lengthened. The length of the suspension members 2, 3 is made longer by adjusting the turnbuckles 54, and the length of the suspension frames is also made longer using the slide mechanisms 55. 234 8 5 1 The turnbuckles 54 for the suspension members 2, 3 can be ordinary turnbuckles.

Any mechanism that is capable of adjusting length can be used for the slide mechanism on the suspension frames 5, 6. An example of such a mechanism is shown in FIG. 11.

The mechanism shown in FIG. 11(a) is an example in which the upper portion 56 and the lower portion 57 of the suspension frame are connected by inserting one into the other and by bolting together 60 through holes 58, 59 that are bored beforehand.

The mechanism shown in FIG. 11(c) is an example in which the upper portion and the lower portion of the suspension frame are also connected by inserting one into the other and by using clamping bolts disposed on the outer side (of the lower portion, in this case).

The present invention as described above shows the effects listed below. (1) It is possible to make smaller the total height of the pendulum in a dynamic damper (an apparatus for controlling vibration) by dividing the desired length of a pendulum into a number of portions and by using a multistage suspension. (2) The period of this multistage suspension dynamic damper can be obtained by calculating the period of the pendulum with a length corresponding to the sum of the 234 8! lengths of pendulums in all stages. Compared to a conventional dynamic damper for controlling vibrations, therefore, the total height of the multistage suspension dynamic damper of the present invention can be smaller for the same period of pendulum motion. The larger the number of divisions (stages) is, the smaller the total height of a system can be. (3) With the addition of a spring, the frequency may be adjusted freely while keeping the length of the pendulum constant. (4) By disposing them between the suspension frames, springs with smaller strokes may be used. Also, the stroke of a damper for amplitude attenuation in an n-stage suspension apparatus can be 1/n of that for a conventional pendulum. (5) By changing the position of the horizontal support piece for the suspension member, the length of the pendulum can be adjusted freely. (6) By making small the clearance between the pillars 34 attached to the under side of the weight and the floor 36, the impact to the floor 36 can be moderated even if the weight should fall down.

Also, the jack 35 placed in the pillar 34 makes maintenance simpler since it becomes easier to lift up the we ight 1. 23 4 8 The weights of the pillar 34 attached to the weight 1 and of the jack 35 can be considered as a part of the weight of the weight 1. (7) By changing the length of the suspension members using the turnbuckles and by changing the length of the suspension frames using the slide mechanisms at the same time, it becomes possible to adjust the period without changing the suspension height L of the suspension frames and the weight. This contributes a better appearance of the system, and it becomes unnecessary to prepare suspension members with different lengths. (8) By changing the length of the suspension members using turnbuckles and by changing the length of the suspension frame with a slide mechanism, the period of the multistage pendulum of the present invention can be adjusted arbitrarily.

Now, referring to FIGS. 13 to 16, we will explain another set of embodiments of the dynamic damper of the present invention. In FIG. 13, numeral 71 indicates an weight. The oscillation of this weight 71 controls the oscillation of the structure 74. Either end of this weight 71 is supported by the suspension member 72' having flexural rigidity through a pin joint 75 at one end of the suspension member so as to be able to rotate in any direction. Also, the other end of the suspension member 72' is supported by 254 8 5 the suspension frame 73 through a pin joint 75 so as to be able to rotate freely. This suspension frame has a rectangular shape whose one side is cut open. Dampers 76 for absorbing vibrational energy of the structure 74 and, if necessary, springs 77 for determining the frequency of the pendulum are disposed between points on the suspension members 72' near said other end of the suspension members and the suspension frame 73.

I Furthermore, either end of the suspension frame is supported by one end of the suspension member 72 having flexural rigidity through a pin joint 75 so as to be able to rotate in any direction. Also, the other end of the suspension member 72 is supported by the structure 74 through a pin joint 75. Dampers 76 for absorbing vibrational energy of the structure 74 and, if necessary, springs 77 for determining the frequency of the pendulum are disposed between points on the suspension members 72 near said other end of the suspension members and the suspension frame 73.

Next, we will describe the operation of this embodiment of the present invention. First, when the structure 74 oscillates, the weight 71 oscillates around suspension points B, and the suspension frame oscillates around suspension points A. The weight 71 and the suspension frame 73 take a simple pendulum motion. Here, the relative displacements between the structure 74 and the suspension frame 73 and 23 4 8 5 ..-s between the suspension frame 73 and the suspension member 72' become smaller near the suspension points A or B. The strokes of the dampers 76 and the springs 77 disposed between the structure 74 and the suspension member 72 and between the suspension frame 73 and the suspension member 72' can therefore be shorter.

Next, referring to FIG. 15, we will explain another embodiment of the present invention. In this embodiment, in place of the dampers 76 and the springs 77, shakers 78 which operate under automatic control are disposed between the structure 74 and the suspension member 72 and between the suspension frame 73 and the suspension member 72'. According to this embodiment, even if the shaker has a short stroke, it can give a large amplitude to the oscillation of the weight 71. By sensing oscillation of the structure 74 and controlling the strokes of the shakers 78, the oscillation of the structure can be absorbed by the oscillational energy of the weight 71.

As we have described above, according to the present invention, rod-like members whose ends are supported through pins and which have flexural rigidity are used as suspension members, dampers and, if necessary, springs are disposed near the suspension points of the suspension members between the suspension members and the structure and between the suspension member and the suspension frame so that dampers 234 and springs with shorter strokes can be used to provide large amplitude damping of the weight. Furthermore, if shakers which are controlled automatically are disposed in place of the dampers, shakers with shorter strokes can provide large amplitude damping of the weight.

Referring to FIGS. 17 to 25, we will now explain still another set of embodiments of the dynamic damper of the present invention. FIG. 17 shows a side view of an embodiment of the present invention, and FIG, 18 shows a plan of the same embodiment. In FIGS. 17 and 18, numeral 81 indicates a weight, numeral 82 a floor, numeral 83 hydrostatic bearings or rollers, numeral 84 links, numeral 85 universal joints, numeral 86 pin joints, numeral 87 a reaction wall, numeral 88 springs, and numeral 89 oil dampers.

In FIGS. 17 and 18, the weight 81 is placed on the floor 82 with the hydrostatic bearings or rollers 83 between them. The two links 84 are disposed between the weight 81 and the floor 82 through the universal joint 85 and the pin joint 86.

Also, the reaction wall 87, which is placed and fixed to the floor 82, is connected to the link 84 through the spring 88 and the oil damper 89.

FIG. 19 shows a relation between the oscillational amplitudes of the building and the weight, and a relation between the amplitude of building oscillation and the effect 234 85 of damping to the building (damping effect) with the embodiment of the present invention as described above, if the oil damper shows the damping force characteristic which is proportional to the square of the velocity when the velocity of the weight becomes over 60cm/sec (the angular frequency is assumed to be l.Orad/sec, and this corresponds to an amplitude of 60cm/sec.). This embodiment is intended for improving the comfortability by reducing oscillations of a building (the amplitude is a few cm) caused by winds of 10-20m/sec which occur normally. The added damping is designed to be at least 4%. Up to about 12cm of the oscillation amplitude of a building, the amplitude of the weight oscillation increases linearly, and when the building's amplitude is 12cm, the weight's amplitude becomes about 60cm. If the amplitudes are lager than these values, the ratio of the weight's amplitude to the building's amplitude begins to decrease. When the building's amplitude becomes 100cm (this value corresponds to strong earthquakes.), the weight's amplitude remains to be 160cm. While the added damping effect to the building is about 4.5% up to the point where the building amplitude is 12cm, it is reduced to almost a half or 2.2% when the building's amplitude is 100cm. Even in this case, however, compared to the use of a stopper which gives sudden reaction to a building and produces bad influences, it is advantageous to have a small added damping 23 4 85 effect despite the smallness of damping. As for the conventional dynamic damper, when the building's amplitude is 100cm the amplitude of the weight becomes 500cm (with the same ratio as up to 12cm of the building's amplitude), and the displacement is 1000cm or 10m. This value is too large for a practical building design. A stopper therefore becomes required to limit the amplitude, but use of a stopper would give large reactive impacts to a building and causes ill effects.

As shown in FIG. 20, an ordinary oil damper having a damping characteristic which is proportional to the velocity automatically switches itself to another characteristic which is proportional to the square of the velocity by restricting the amount of oil flowing through a valve as the velocity become greater than a certain level vo . Normally, the damper operates below this level. In the present invention, the damper is used in the velocity range above this level so as to achieve the above-mentioned effects. Also, the components of the dynamic damper of the present invention are designed to secure sufficient structural strength so that they can withstand a strong earthquake or wind which causes the amplitude to be larger than the normal level.

FIG. 21 shows a single pendulum type embodiment of the present invention, FIG. 22 shows a multistage suspension type, FIG. 23 shows an inclined pendulum type, FIG. 24 shows 23 4 85 an inverted pendulum type, and FIG. 25 shows an apparatus in which oil dampers and springs are directly attached to the weight. The functions and effects of these embodiments are the same as described above.

Also, in FIG. 21, numeral 91 indicates a weight, numeral 92 suspension rods or cables, numeral 93 an oil damper, numeral 94 a ceiling, and numeral 95 a reaction wall. In FIG. 22, numeral 101 indicates a weight, numeral 102 suspension rods or cables, numeral 103 oil dampers, numeral 104 a ceiling, numeral 105 a reaction wall and numeral 106 frames. In FIG. 23, numeral 111 indicates a weight, numeral 112 rods, numeral 113 an oil damper, numeral 114 a wall, and numeral 115 a reaction wall. In FIG. 24, numeral 121 a weight, numeral 122 a rod, numeral 123 an oil damper, numeral 124 a floor, numeral 125 a reaction wall, and numeral 126 a spring. In FIG. 25, numeral 131 indicates a weight, numeral 132 rollers, numeral 133 an oil damper, numeral 134 a floor, numeral 135 a reaction wall, and numeral 136 a spring.

Also, the velocity level vo above which the damping force becomes proportional to the square of the velocity can be set very small. In some extreme cases, it can be zero so that the damping characteristic which is proportional to the square of the velocity is used in the entire velocity range.

According to the present invention as described just above, a dynamic damper is provided which can operate even » 1 234 85 1 under the conditions of a strong earthquake or wind and which can control the oscillational amplitude of a weight while maintaining a certain level of vibrational damping under such conditions. Thus, the required space for a dynamic damper can be reduced, and a stopper becomes unnecessary. This should contribute to reduce costs of a building and efforts in its designing. t

Claims (13)

1. :i 4 a !5 i WHAT I/WE CLAIM IS: 1.
2. In a pendulum type dynamic damper for controlling vibrations comprising a weight, a spring, a suspension member and an attachment frame, a dynamic damper which is characterized in that an upper suspension frame and a lower suspension frame are disposed between the attachment frame and the weight, the upper and the lower suspension frame are rectangular in shape, and the upper suspension frame and the lower suspension frame are connected by four connection members so as to form a multistage suspension of the weight, and a certain angle is provided between the upper and the lower suspension frames so that the suspension members do not overlap each other. wherein the spring for adjusting the frequency of pendulum motion is disposed between the suspension frames.
3. 3. The dynamic damper as described in claim 1, wherein a damper is disposed between the suspension frames.
4. 4. The dynamic damper as described in claim 1, wherein the spring for adjusting the frequency of pendulum motion and a damper are disposed between the suspension frames.
5. 5. The dynamic damper as described in any one of claims 2 to 4, wherein the spring for adjusting the frequency of The dynamic damper as described in claim 1, 32 pendulum motion or a damper are also disposed between the suspension frame and the weight.
6. 6. The dynamic damper as described in any one of claims 2 to 4, wherein the spring for adjusting the frequency of pendulum motion and a damper are also disposed between the suspension frame and the weight.
7. 7. The dynamic damper as described in any one of claims 1 to 6, wherein a horizontal support device for the suspension member is disposed for adjusting the frequency of pendulum motion.
8. 8. A dynamic damper as described in claim 1 wherein said suspension member has flexural rigidity and is rotatably connected at the upper and lower ends thereof, and means for varying strokes are disposed near the upper end of the suspension member between the suspension member and the connection member,and between the suspension member and the attachment frame.
9. 9. The dynamic damper as described in claim 8, wherein the means for varying strokes are oil dampers and springs.
10. 10. The dynamic damper as described in claim 8 wherein the means for varying strokes are oil dampers or springs. ~ 33
11. 11 . The dynamic damper as described in claim 8, wherein the means for varying strokes are shakers which can be controlled automatically.
12. 12 • The dynamic damper as described in any one of claims 9 to 11, comprising an oscillating system and an oil damper, a dynamic damper which is characterized in that an oil damper whose damping force characteristic becomes proportional to the square of the velocity above a certain velocity level is used.
13. 13 . The dynamic damper as described in any one of claiirs 3 to 7, wherein the damper is an oil damper whose damping force characteristic becomes proportional to the square of the velocity above a certain velocity level. Potent Attorneys^ the Applicants). - 34 -