U.S. patent application number 10/476987 was filed with the patent office on 2004-07-08 for frictional damper for damping movement of structures.
Invention is credited to Mualla, Imad H.
Application Number | 20040128921 10/476987 |
Document ID | / |
Family ID | 26069019 |
Filed Date | 2004-07-08 |
United States Patent
Application |
20040128921 |
Kind Code |
A1 |
Mualla, Imad H |
July 8, 2004 |
Frictional damper for damping movement of structures
Abstract
The invention is a damper and a method for protecting buildings
and similar structural systems from dynamic loading such as loading
caused by earthquakes, strong winds or machine vibrations. More
specifically, the damper is made from structural members being
interconnected in frictional or visco-elastically dampened
rotational joints. Due to the dampening of the joints, relative
movement between the structural elements is dampened. In
particular, the damper is useful for base isolation, e.g., in order
to allow a building or a machine to move in a dampened movement
relative to its foundation or in order to allow a cable stay of a
cable stay bridge to move in a dampened movement relative to its
fixation point on the bridge.
Inventors: |
Mualla, Imad H; (Rodovre,
DK) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
26069019 |
Appl. No.: |
10/476987 |
Filed: |
February 9, 2004 |
PCT Filed: |
May 9, 2002 |
PCT NO: |
PCT/DK02/00305 |
Current U.S.
Class: |
52/167.1 |
Current CPC
Class: |
E04H 9/0215 20200501;
E01D 19/16 20130101; E01D 11/04 20130101; F16F 7/02 20130101 |
Class at
Publication: |
052/167.1 |
International
Class: |
E04B 001/98; E04H
009/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 9, 2001 |
DK |
PA 2001-00728 |
Oct 16, 2001 |
DK |
2001-01579 |
Claims
1. A device for dampening the relative movement of a first
structural member in relation to a second structural member, the
first structural member being rotationally joined to at least two
elements of a first group of elements, and the second structural
member being rotationally joined to at least two elements of a
second group of elements, wherein each of the elements of the first
group of elements are individually joined to an element of the
second group of elements in a rotational joint, so as to form at
least six rotational joints for dampening relative movement between
the elements of the first group of elements and the elements of the
second group of elements and thus for dampening the movement of the
first structural member in relation to the second structural
member.
2. A device according to claim 1,the device further comprising
clamping means for clamping at least one of the rotational joints
together, so as to maintain a clamping force between elements in
the rotational joints.
3. A device according to claims 1 or 2, further comprising at least
one dampening member arranged in at least one of the rotational
joints
4. A device according to claim 3, wherein the at least one
dampening member is arranged between the elements of the first
group of elements and the elements of the second group of elements
so as to establish contact between the elements and the dampening
member so that the relative movement of the elements is
dampened.
5. A device according to any of claims 3-4, wherein the at least
one dampening member is arranged between first structural member
and the elements of the first group of elements and/or the elements
of the second group of elements so as to establish contact between
the elements and the dampening member and between the structural
member and the dampening member so that the relative movement of
the elements in relation to the structural member is dampened.
6. A device according to any of claims 3-5, wherein the at least
one dampening member is arranged between the second structural
member and the elements of the first group of elements and/or the
elements of the second group of elements so as to establish contact
between the elements and the dampening member and between the
structural member and the dampening member so that the relative
movement of the elements in relation to the structural member is
dampened.
7. A device according to any of claims 3-6, wherein the at least
one dampening member comprises a piece of friction material so that
the relative movement of the elements is dampened by friction.
8. A device according to any of claims 3-7, wherein the at least
one dampening member comprises a piece of a visco-elastic material
so that the relative movement of the elements is dampened by
visco-elasticity.
9. A device according to any of claims 3-5, further comprising a
piece of a third material arranged between the at least one
dampening member and the elements of the first group of elements or
between the at least one member and the elements of the second
group of elements.
10. A device according to any of claims 3-9, further comprising a
piece of a third material arranged between at least two dampening
members in at least one of the rotational joints.
11. A device according to any of claims 8-10, wherein the piece of
visco-elastic material is arranged in at least one of the joints
between the first structural member and one of the at least two
elements of the first group of elements,
12. A device according to any of claims 8-11, wherein the piece of
visco-elastic material is arranged in at least one of the joints
between the second structural member and one of the at least two
elements of the second group of elements,
13. A device according to any of claims 7-12, wherein the piece of
friction material is arranged in at least one of the joints between
elements of the first group of elements and elements of the second
group of elements.
14. A device according to any of the preceding claims, wherein the
clamping means is adapted to enable the clamping force to be
varied.
15. A device according to any of the preceding claims, wherein at
least one of the joints comprises a pin extending through each of
the elements of the joint.
16. A device according to claim 15, comprising a bolt, at least a
portion of the bolt constituting the pin, the bolt having: a bolt
element with a bolt head, a nut with a nut head, the clamping force
being determined by the pretension of the bolt.
17. A device according to claim 16, further comprising means for
maintaining a substantially constant clamping force with time.
18. A device according to claim 17, wherein the means for
maintaining a substantially constant clamping force comprise at
least one spring arranged between the bolt head and a surface of
one of the elements of at least one of the joints and/or between
the nut head and a surface of one of the elements of at least one
of the joints.
19. A device according to claim 18, wherein the spring comprises a
disc spring.
20. A device according to claim 19, comprising at least two disc
springs.
21. A device according to claim 20, wherein at least one disc
spring is arranged between the bolt head and a surface of one of
the elements of the first group of elements, and wherein at least
one disc spring is arranged between the nut head and a surface of
one of the elements of the second group of elements.
22. A device according to claim 17-21, wherein the means for
maintaining a substantially constant clamping force comprise
hydraulic, pneumatic and/or electric means for maintaining the
clamping force.
23. A device according to any of claims 3-22, wherein at least one
dampening member is arranged between at least one of the elements
of at least one of the joints and at least one joint plate.
24. A device according to any of claims 7-23, wherein the piece of
friction material is made of steel, anti-corrosive steel, brass,
aluminium or any alloys comprising aluminium or any other steel
material or composite of steel and plastics or composites of
plastics and fibres of glass, carbon, kevlar or similar or
composites of any ceramics materials and fibres of glass, carbon,
kevlar or similar.
25. A device according to any of claims 7-24, wherein the piece of
friction material comprises an asbestos free composite material
comprising kevlar and brass.
26. A device according to any of the preceding claims, wherein the
element of the first group of elements and/or the element of the
second group of elements are made of steel, anti-corrosive steel,
brass, aluminium or any alloys comprising aluminium or any other
steel material or composite of steel and plastics or composites of
plastics and fibres of glass, carbon, kevlar or similar or
composites of any ceramics materials and fibres of glass, carbon,
kevlar or similar.
27. A device according to any of claims 2-26, wherein the clamping
force shows a variation of less than 5% in a 300 cycle test with
0.5 Hz.+-.0.1 Hz forcing excitement frequency and a rotation
amplitude of one of the at least two structural members of up to
0.2 rad at an applied excitement moment of .+-.1700 kN.mm and an
initial clamping force of 42 kN.+-.0.5 kN.
28. A device according to any of the preceding claims, being
adapted so that a substantially linear relationship between
displacement amplitude of one of the at least two structural
members and energy dissipation in the joints, is provided.
29. A device according to any of the preceding claims, wherein the
first structural member is attached to a first lower part of a
building structure and wherein the second structural member is
attached to a second upper part of the building structure.
30. A damper for dampening the relative movement of a first
structural member in relation to a second structural member,
wherein the first structural member is rotationally attached to the
second structural member in a rotational joint for frictional
dampening of relative rotational movement between the first
structural member and the second structural member and thus for
dampening the rotational movement of the first structural member in
relation to the second structural member.
31. A device for dampening movements of structural and non
structural elements in civil engineering structures, the device
comprising: at least two members, a piece of a visco-elastic
material arranged between and in contact with the at least two
members in a joint for visco-elastic dampening of relative movement
between the at least two members, clamping means for clamping the
at least two members together, so as to provide a clamping force
applying a compressive force against the visco-elastic material,
and means for connecting each of the at least two members to
respective ones of the structural elements.
32. A device according to claim 31, further comprising a piece of a
friction material arranged between and in contact with a first one
of the two members and the visco-elastic material for a combined
frictional and visco-elastic dampening of relative movement between
the at least two members.
33. A device according to claim 31 or 32, wherein the clamping
means are adapted to vary the clamping force and thus the applied
compressive force against the visco-elastic material.
34. A device according to claim 31-33, wherein the visco-elastic
material is adapted to change the dampening characteristic based on
the compressive force applied.
35. A device according to any of claims 32-34, further comprising a
piece of a third material arranged between the friction material
and the first of the two members.
36. A device according to any of claims 32-35, further comprising a
piece of a third material arranged between the friction material
and the visco-elastic material.
37. A device according to any of claims 32-36, further comprising a
piece of a third material arranged between the visco-elastic
material and one of the two members.
38. A device according to any of claims 31-37, further comprising a
piece of piezoelectric material arranged between the at least two
members.
39. A device according to any of claims 31-38, wherein the
visco-elastic material is selected from the group consisting of
rubber, acrylic polymers and any visco-elastic materials.
40. A device according to any of claims 32-39, wherein the friction
material is selected from the group consisting of: steel,
anti-corrosive steel, brass, aluminium and any alloys comprising
aluminium and any other steel material and composites of steel and
plastics and composites of plastics and fibres of glass, carbon,
kevlar and composites of any ceramics materials and fibres of
glass, carbon or kevlar.
41. A device according to any of claims 36-40, wherein the third
material is made of a material selected from the group consisting
of: steel, anti-corrosive steel, brass, aluminium and any alloys
comprising aluminium and any other steel material and composites of
steel and plastics and composites of plastics and fibres of glass,
carbon, kevlar and composites of any ceramics materials and fibres
of glass, carbon or kevlar.
42. A device according to any of claims 31-41, wherein the at least
two members are made of a material selected from the group
consisting of: steel, anti-corrosive steel, brass, aluminium and
any alloys comprising aluminium and any other steel material and
composites of steel, plastics and composites of plastics and fibres
of glass, carbon, kevlar and composites of any ceramics materials
and fibres of glass, carbon or kevlar.
43. A device according to any of claims 31-42, wherein the joint
comprises a pin extending through each of the at least two members
so as provide a rotational joint.
44. A device according to claim 43, comprising a bolt, at least a
portion of the bolt constituting the pin, the bolt having: a bolt
member with a bolt head, a nut with a nut head, the clamping force
being determined by the pretension of the bolt.
45. A device according to claims 43-44, further comprising means
for maintaining a substantially constant clamping force with
time.
46. A device according to claim 45, wherein the means for
maintaining a substantially constant clamping force comprise at
least one spring arranged between the bolt head and a surface of
one of the members and/or between the nut head and a surface of one
of the members.
47. A device according to claim 46, wherein the spring comprises at
least one disc spring.
48. A device according to claim 45, wherein at least one disc
spring is arranged between the bolt head and a surface of one of
the members, and wherein at least one disc spring is arranged
between the nut head and a surface of another one of the
members.
49. A device according to claim 48, wherein at least one washer is
arranged between at least one of the disc springs and the
corresponding surface of one of the members.
50. A device according to any of claims 31-49, wherein the clamping
means comprises an actively adjustable clamping actuator.
51. A device according to claim 50, wherein the actively adjustable
clamping actuator is actuated hydraulically, pneumatically and/or
electrically.
52. A device according to claim 51, wherein the actively adjustable
clamping actuator is actively controlled by a controller.
53. A device according to claim 52, wherein the controller controls
the adjustable clamping actuator based on a feedback from at least
one sensor system.
54. A device according to claim 53, wherein the at least one sensor
system is adapted to measure a measure or a combination of measures
indicative of: acceleration, velocity, displacement in the
structural system, temperature, stress in the structural system
and/or strain in the structural system.
55. A device according to any of claims 31-54, wherein the at least
two members comprise: a side plate and a central plate extending in
substantially parallel planes.
56. A device according to claim 55, wherein the piece of
visco-elastic material is arranged between the side plate and the
central plate.
57. A device according to claims 55 or 56, wherein the piece of
friction material is arranged between the side plate and the
central plate.
58. A device according to claims 55-57, wherein the piece of a
third material is arranged between the side plate and the central
plate.
59. A device according to any of claims 31-58, and comprising two
side plates arranged symmetrically around the central plate.
60. A device according to claim 59, comprising two pieces of
visco-elastic materials, each piece being arranged between a
respective one of the side plates and the central plate.
61. A device according to claims 59-60, comprising two pieces of
friction materials, each piece being arranged between a respective
one of the side plates and the central plate.
62. A device according to claims 59-61, comprising two pieces of
the third material, each piece being arranged between a respective
one of the side plates and the central plate.
63. A device according to any of claims 55-62, wherein the central
plate is adapted to be connected to one of the structural elements
in a pivotal manner, so as to allow relative rotational movement
between the central plate and the structural element.
64. A device according to any of claims 55-62, wherein the central
plate is adapted to be connected to one of the structural elements
in a fixed manner, so as to prevent relative movement between the
central plate and the structural element.
65. A device according to any of claims 55-64, wherein the side
plates are adapted to be connected to one of the structural
elements in a pivotal manner, so as to allow relative rotational
movement between the side plates and the structural element.
66. A device according to any of claims 55-64, wherein the side
plates are adapted to be connected to one of the structural
elements in a fixed manner, so as to prevent relative movement
between the side plates and the structural element.
Description
TECHNICAL FIELD
[0001] This invention generally relates to the protection of
structural systems against dynamic loading such as loading caused
by earthquakes or caused by impact from oceanic waves, vibrations
from traffic, machines or impact of the wind. More specifically the
invention relates of substantially horizontal movement of
structures and in particular to the dampening of torsion in
building structures.
BACKGROUND OF THE INVENTION
[0002] When a structural member is excited by a horizontal external
force, torsion or similar horizontal movement may occur. Torsion,
especially in high building structures or towers may have serious
impact on the conditions of the structure or even result in a
collapse.
[0003] Dampers play an important role in the protection of
structures, e.g. houses or similar building structures, and they
exist in numerous variants. Dampers are typically dampening the
motion by means of a frictional force between two moving parts
attached between structural members of the building or by means of
a fluid being pressed to flow between two chambers through a
restricted tube. Some dampers are actively changing the dampening
effect corresponding to external conditions, and other dampers are
passive dampers having a constant dampening characteristic. Typical
dampers are costly to produce and even more costly to assemble into
a structural member of a building. Typically a building have to be
designed for a specific damper, either due to the bulky design of
the existing dampers or due to correlation between the structural
characteristics of the damper versus the characteristics of the
building.
[0004] Typically the existing dampers are adapted to individually
dampen movement of the vertically mounted structural members of
building structures. This result in the dampening of the movement
of individual parts of the building in relation to other parts of
the same building, which dampening may protect e.g. a building from
collapsing. However, if the entire building is moved horizontally,
e.g. rotationally, the building may be damaged severely, even
though the individual structural members of the building is being
dampened individually. Horizontal movement may occur e.g. if the
foundation of a building is displaced by an earthquake or by
similar vibrations transmitted through the ground.
DESCRIPTION OF THE INVENTION
[0005] It is an object of the present invention to provide a damper
for dampening substantially horizontal movement or torsion in
structures such as torsion in buildings. It is a further object to
provide a damper which is based on a very simple design and
comprises parts that are easily produced and assembled as well as
easy to retrofit into existing structures as well as to fit into
new structures. The present invention further provides a price
efficient damper with a reliable dampening effect.
[0006] According to a first aspect, the present invention relates
to a device for dampening the relative movement of a first
structural member in relation to a second structural member,
[0007] the first structural member being rotationally joined to at
least two elements of a first group of elements, and
[0008] the second structural member being rotationally joined to at
least two elements of a second group of elements,
[0009] wherein each of the elements of the first group of elements
are individually joined to an element of the second group of
elements in a rotational joint, so as to form at least four
rotational joints for dampening relative movement between the
elements of the first group of elements and the elements of the
second group of elements and thus for dampening the movement of the
first structural member in relation to the second structural
member.
[0010] The first structural member and/or the second structural
member may as an example be structural frames comprising e.g. three
or four beams joined to form a triangle or a quadrangle. The
structural members may serve for supporting a building structure,
e.g. a house or in a multi-storeys building e.g. as a part of the
foundation of the building and/or sandwiched into in a certain
level of the building, e.g. for dampening the top of the building.
As an example a water tank or machine may be placed on the roof of
large buildings, attached to the building through a damper. As an
example fire fighting equipment, swimming pools, air conditioners,
ventilation systems etc, may be mounted to the building in such a
way. As another example, a building may fastened to its foundation
through a damper.
[0011] The two structural members may preferably be provided in the
form of two steel structural members. E.g. 4 bars of steel welded
together so as to form an open quadrangle. One of the quadrangles
serving for attachment of the structure or building and the other
is attached to the foundation. The structural members could also be
made from concrete elements. The damper is integrated in the
building structure by attaching the first structural member to one
part of the building structure and the other structural member to
another part of the building structure. As an example, a solid
concrete foundation is moulded into the ground, and the first
structural member--a quadrangle made of steel profiles is
integrated in--or attached to the upper part of the foundation,
e.g. by bolts.
[0012] The second structural member is attached to the first
structural member through the two sets of elements, rotationally
interconnected in a joint. The second structural member is then
again attached to the rest of the building structure, e.g. bolted
to a steel building structure, or the building structure is simply
arranged on top of the second structural member, held in place by
its weight. The weight of the building structure thereby rests on
top of the second structural member. The weight of the building
structure may as an example be carried by concrete blocks slidingly
supporting the second structural member.
[0013] The damper may further comprise clamping means for clamping
the rotational joints together, so as to maintain a clamping force
between elements in the rotational joints. The clamping means may
be constituted by a pin or bolt extending through two elements and
thus forms a rotational joint therein between or the rotational
joint may be formed in any other way, e.g. like an axial
ball-bearing wherein the two elements of the bearing is held
together by a locking engagement between each of the two elements
and a mutual element such as a ball. The corresponding joints
between the elements and the structural members may likewise be
formed with a through-going pin or in any similar way, e.g. like an
axial ball bearing.
[0014] At least one of the rotational joints or all of the
rotational joints may be provided with at least one dampening
member. The dampening member may be constituted by one or more
pieces of a material which dampens the mutual movements between the
joined elements, e.g. between the structural frame and one of the
elements of the first or second group of elements or between two
elements of the first or second group of elements.
[0015] According to a preferred embodiment, at least one dampening
member is arranged between the elements of the first group of
elements and the elements of the second group of elements so as to
establish contact between the elements and the dampening member so
that the relative movement of the elements is dampened.
[0016] According to another preferred embodiment, the at least one
dampening member is arranged between the first structural member
and the elements of the first group of elements and/or the elements
of the second group of elements so as to establish contact between
the elements and the dampening member and between the structural
member and the dampening member so that the relative movement of
the elements in relation to the structural member is dampened.
[0017] According to another preferred embodiment, the at least one
dampening member is arranged between the second structural member
and the elements of the first group of elements and/or the elements
of the second group of elements so as to establish contact between
the elements and the dampening member and between the structural
member and the dampening member so that the relative movement of
the elements in relation to the structural member is dampened.
[0018] The dampening member may comprise one or more pieces of a
friction material and/or one or more pieces of a visco-elastic
material. Through the contact between the material and the elements
of a joint, the mutual movement of those elements is dampened
either by the friction or by the viscosity of the material.
[0019] As an example, the device may comprise a frictional pad
arranged between the two elements as a part of the rotational
joint. The frictional pad may be arranged between the elements in a
sandwich fashion. The frictional pad provides a dry frictional
lubrication and is intended to maintain a mainly constant
frictional coefficient. At the same time the frictional pad is
intended to dampen the grinding noise prevailing from the
frictional movement of the elements. Similarly, frictional pad
material may be arranged in the joints where the elements are
rotationally attached to the structural members.
[0020] In a similar fashion, the at least one dampening member may
comprise a piece of a visco-elastic material. The visco-elastic
material may preferably be selected from the group consisting of
rubber, acrylic polymers, copolymers, any glassy substances, and
any visco-elastic materials such as 3M visco-elastic materials or
in general, any material which dissipate energy when subjected to
shear deformation.
[0021] The dampening of the movement arises from the relaxation and
recovery of the polymers network after it has been deformed.
[0022] In order to separate more pieces of visco-elastic or
friction material respectively, a piece of a third material may be
arranged between the at least one dampening member and the elements
of the first group of elements or between the at least one member
and the elements of the second group of elements. The third
material could be a low friction material such as Teflon or nylon.
Moreover, if one of the joints is provided with more than one
dampening members, a piece of the third material may be arranged
between two of these dampening members in at least one of the
rotational joints.
[0023] According to a preferred embodiment, the piece of
visco-elastic material is arranged in at least one of the joints
between the first structural member and one of the at least two
elements of the first group of elements. The piece of friction
material may then be arranged in at least one of the joints between
elements of the first group of elements and elements of the second
group of elements. In that way, the friction material and the
visco-elastic material is kept completely separated in different
joints of the dampening device.
[0024] The separation between the visco-elastic material in one of
the joints and the friction material in another one of the joints
has the advantage, that the dampening characteristics may easily be
changed. As an example, the one and maybe only joint purely
provided with visco-elastic material may be prevented from rotating
by a locking arrangement. In that way the damper changes from
dampening with a combined visco-elastic and frictional
characteristics to dampening with a purely frictional
characteristics. The opposite situation is also applicable, i.e.
that one joint provided purely with frictional material is
prevented from rotation by a locking arrangement.
[0025] The device may furthermore comprise means adapted to vary
the clamping force. By varying the clamping force, the frictional
force and thereby the dampening characteristic is changed and can
thus be adapted for a specific purpose, e.g. to match the movement
of a certain wind force, earthquake etc. The means for varying the
clamping force could be an electro-mechanic, electro-hydraulic,
pneumatic or similar mechanically or electrically controlled device
enabling dampers in a building to be actively adjusted to actual
conditions.
[0026] In a preferred embodiment of the invention, the joint
comprises a pin extending through each of the elements in the
rotational joints. The pin can act as the only element holding the
joints together and thus provide for easy fitting of the damper and
adjustment of the dampening effect. The frictional movement between
the elements or alternatively between the frictional pad arise from
rotation of the elements around the pin, which thus acts like a
hinge pin.
[0027] In a preferred embodiment of the invention the device may
comprise a bolt, where at least a portion of the bolt constitutes
the pin, the bolt having:
[0028] a bolt element with a bolt head,
[0029] a nut with a nut head,
[0030] the clamping force being determined by the pretension of the
bolt. This is a simple and reliable embodiment of the invention,
where only simple tools are necessary for the assembly of the
device as well as for the adjustment of the clamping force.
[0031] The device may further comprise means for maintaining a
substantially constant clamping force over time. This is essential,
since the frictional force is a function of the clamping force and
since the frictional force is adjusted to match the dampening
conditions.
[0032] The means for maintaining a substantially constant clamping
force may comprise at least one spring arranged between the bolt
head and a surface of one of the elements and/or between the nut
head and a surface of one of the elements. The spring may
preferably be a disc spring or more disc springs arranged in series
or it could be one or more disc spring(s) arranged between the bolt
head and a surface of one of the elements, and another disc spring
or more disc springs arranged between the nut head and a surface of
another of the elements.
[0033] According to a preferred embodiment of the invention, at
least one frictional pad is arranged between at least one of the
elements of at least one of the joints and at least one joint
plate. As an example, the joint may be made by applying a bolt
though an element from the first group of elements, a shim or
metallic plate, a circular pad material and an element from the
second group of elements. All parts being pressed together by the
bolt and thus providing a frictional resistance against the
rotation of one of the elements in relation to the other one of the
elements of that joint.
[0034] The friction pad may preferably be made of brass, aluminium
or any alloys comprising brass or aluminium or composites of
plastics and fibres of glass, carbon, kevlar or similar or
composites of any ceramics materials and fibres of glass, carbon,
kevlar or similar. Many of such compositions may be known e.g. from
materials for clutches or brakes.
[0035] The frictional pad is intended to maintain a constant
frictional force over a period of time and even after many cycles
of movement. Such materials are readily available on the market,
produced e.g. for the purpose of transferring frictional forces in
brakes or clutches.
[0036] It has been found, that a device wherein the shim or
metallic plate or plates and the elements are made of steel,
anti-corrosive steel or brass is suitable but other materials are
adaptable such as aluminium or any alloys comprising aluminium or
any other steel material or composite of steel and plastics or
composites of plastics and fibres of glass, carbon, Kevlar.TM. or
similar or composites of any ceramics materials and fibres of
glass, carbon, kevlar.TM. or similar.
[0037] Preferably, the clamping force shows a variation of less
than 10% such as 8% or even less than 7% such as 5% in a long term
test, such as a 200-1000 cycle test such as a 300 cycle test with
0.2-1 Hz forcing excitement frequency such as 0.5 Hz forcing
excitement frequency and a rotation amplitude of one of the at
least two elements of 0.01-0.22 rad such as 0.20 at an applied
moment force of +10.000 KN.mm to -10.000 KN.mm such as .+-.1700
KN.mm. and an initial clamping force of 1-100 KN such as 42 KN. In
a specific test (cf. the below discussion of experimental results,
the variation was 5% in a 300 cycle test).
[0038] It is preferred that the relationship between displacement
amplitude of one of the at least two elements of a joint and energy
dissipation in the frictional joint is substantially linear. This
makes the damper easier to model and thereby easier to design for a
specific purpose.
[0039] According to a second aspect, the present invention relates
to a device for dampening movements of structural and non
structural elements in civil engineering structures, the device
comprising:
[0040] at least two members,
[0041] a piece of a visco-elastic material arranged between and in
contact with the at least two members in a joint for visco-elastic
dampening of relative movement between the at least two
members,
[0042] clamping means for clamping the at least two members
together, so as to provide a clamping force applying a compressive
force against the visco-elastic material, and
[0043] means for connecting each of the at least two members to
respective ones of the structural elements.
[0044] The visco-elastic material may preferably be selected from
the group consisting of rubber, acrylic polymers, copolymers, any
glassy substances, and any visco-elastic materials such as 3M
visco-elastic materials or in general, any material which dissipate
energy when subjected to shear deformation.
[0045] The dampening of the movement arises from the relaxation and
recovery of the polymers network after it has been deformed.
[0046] The structural element in civil engineering could be beams,
columns and slabs, e.g. of a building structure such as a house.
The wall which is dampened by the damper may comprise a combination
of structural elements as well as non structural elements, and
consequently the damper may dampen the movement of both structural
and non structural elements. The non structural elements could be
windows, doors, infill walls such as brick walls, panels and
partition walls.
[0047] Accordingly:
[0048] The damper device can be mounted in 2 or more directions
e.g. in a several storeys building.
[0049] The damper device can be mounted in reinforced concrete
frame structures with or without walls.
[0050] The damper device can be mounted in large panel walls to
reduce their sliding failure mechanism. The panels would typically
be made from concrete but they may be made from other material such
as timber, steel or composite materials.
[0051] The damper device can be mounted in elevated water tanks to
reduce their vibration response.
[0052] The damper device can be mounted in bridges and elevated
highways. It can be installed in two directions to reduce the
response. As an example a number of dampers may be arrange in a
first direction and a number of dampers may be arranged in a second
direction. The dampers in the first direction may be provided with
a dampening structure, which is different from the dampening
structure of the dampers arranged in the second direction.
[0053] The damper device can be used to reduce the vibration caused
by elevated machines, which are mounted on a frame structure.
[0054] The damper device can be mounted in many kinds of offshore
structures to reduce their vibration response due to wave loads,
e.g. from water or wind.
[0055] The damper device can be mounted in ready-made garages.
[0056] The damper device can be mounted in portable metal tents for
dampening the movements of the carrying columns and beams of the
tent.
[0057] The damper device can be used to reduce the rotation of
joints in frame structures.
[0058] The damper device can be mounted in several storeys
industrial buildings.
[0059] The damper device can be mounted in timber frame
structures.
[0060] The damper device can be mounted in metal towers.
[0061] The damper device can be mounted in one, or multiple storey
houses.
[0062] The damper device can be mounted in cables of suspension
bridges or cable stay bridges.
[0063] The damper device can be mounted in cables in pretension
structures, e.g. stadiums or large halls, e.g. the Millennium Hall
in London.
[0064] The damper device can be mounted in large panels of glass
that used in the facade of glazing buildings.
[0065] The damper device can be mounted in floors to damp the floor
vibration caused by human or machines.
[0066] The damper device can be mounted in pipes that transferring
fluids which cause some vibration through the fluid movements.
[0067] The damper device can be mounted in Oil, Gas, liquids, fuel
tanks
[0068] The damper device can be mounted in roof ceilings that hold
a false ceilings or heavy chandelier.
[0069] The damper device can be mounted in museums, e.g. underneath
a table or a platform holding a statue etc.
[0070] The damper device can be mounted behind many types of
furniture, e.g. cupboards.
[0071] The damper device can be mounted behind shelves which are
used to store parts in factories or store houses.
[0072] When the damper dampens movement, the at least two members
are brought from a mutually original position to a mutually
displaced position wherein at least one of the at least two members
are rotated in relation to the other(s) of the at least two
members. The damper could further be provided with means for
bringing the at least two members back to the original position. As
an example, a spring or a set of springs may be provided between
the members. The springs should have sufficient strength to ensure
that the members, after being displace from the original position,
are drawn back to the original mutual position. The spring or set
of springs may e.g. be constituted by (a) clock-spring(s), (a)
compression spring(s), (a) torsion spring(s) or (a)
rotational-spring(s) or any combination of the mentioned
springs.
[0073] According to a preferred embodiment of the invention the
damper is adapted for dampening the movement of prefabricated
panels or walls made of timber or light weight metal frames such as
frames made from a light weight steel alloy. The panels could as an
example be made in a panel factory and be pre-mounted with the
damper. The dampers could either be pre-adjusted for a specific use
of the panel or the dampers could be adjusted at a later stage when
they are mounted, e.g. in a residential structure.
[0074] The nature of the damper enables the use of the damper both
in existing structures as well as in new structures due the
simplicity of the concept.
[0075] As movement in the damper starts, the visco-elastic material
will deforme elastically and thus dampen the movement. As the
amplitude of the movements may raise to a limit where the friction
forces can not resist the applied forces, then sliding starts.
[0076] It may be preferred to combine the visco-elastic material
with one or more pieces of a friction material arranged between the
two members and/or between one or more pieces of the visco-elastic
material arranged between the two members. The friction material
provides a dry frictional lubrication and intends to maintain a
mainly constant friction coefficient when the pieces of material
arranged between the two members starts to slip.
[0077] The device may further comprise pieces of a third material
arranged between the pieces of visco-elastic materials and/or the
pieces of friction material. As an example, pieces of brass or
similar metals may provide an excellent dry lubrication for the
frictional movement between the different pieces.
[0078] The device may furthermore comprise means adapted to vary
the clamping force. By varying the clamping force the frictional
force and thereby the dampening characteristic is being changed and
can thus be adapted for a specific purpose, e.g. to match the
movement of a certain wind force, earthquake etc. The means for
varying the clamping force could be an electro-mechanic,
electro-hydraulic, pneumatic or similar mechanically or
electrically controlled device enabling dampers in a building to be
actively adjusted to actual conditions.
[0079] According to a preferred embodiment of the present
invention, one or more pieces of a piezoelectric material is
inserted between the two members. The piezoelectric elements may be
inserted anywhere and in contact with any of the other inserted
elements. By application of an electrical voltage to the elements,
the size of the elements and thus the clamping force may be
varied.
[0080] In a preferred embodiment of the invention the joint
comprises a pin extending through each of the at least two members.
The pin can act as the only member holding the damper together and
thus provide for a easy fitting of the damper and adjustment of the
dampening effect. The frictional movement between the members or
alternatively between the frictional pad arise from rotation of the
members around the pin, which thus acts like a hinge pin.
[0081] In a preferred embodiment of the invention the device may
comprise a bolt, where at least a portion of the bolt constitutes
the pin, the bolt having:
[0082] a bolt member with a bolt head,
[0083] a nut with a nut head,
[0084] the clamping force being determined by the pretension of the
bolt. This is a simple and reliable embodiment of the invention,
where only simple tools are necessary for the assembly of the
device as well as for the adjustment of the clamping force.
[0085] The device may further comprise means for maintaining a
substantially constant clamping force over time. This is essential,
since the frictional force is a function of the clamping force and
since the frictional force is adjusted to match the dampening
conditions.
[0086] The means for maintaining a substantially constant clamping
force can comprise at least one spring arranged between the bolt
head and a surface of one of the members and/or between the nut
head and a surface of one of the members. The spring can preferably
be a disc spring or more disc springs arranged in series or it
could be one or more disc spring(s) arranged between the bolt head
and a surface of one of the members, and another disc spring or
more disc springs arranged between the nut head and a surface of
another of the members. Preferably, a washer is placed between the
disc spring(s) and the surface of the members. The washer should be
adapted to uniformly distributed the pressure over there the
friction or viscoelastic pads. The washer could be a hard steel
disc with a thickness allowing the washer to sustain the pressure
from the nut or bolt substantially without deforming. By the
introduction of a washer, members with a lower wall thickness may
be chosen and accordingly, the weight of the damper may be
reduced.
[0087] In a preferred embodiment of the invention, the at least two
members comprise a side plate and a central plate extending in
substantially parallel planes. The side plate could preferably be
arranged in either fixed or pivotal connection with one of the
braces of the bracing system, the brace being connected fixed or
pivotally to a member of the frame structure at the other end. The
central plate is attached fixed or pivotally to one of the members
of the frame structure, so as respectively to prevent or allow
relative rotational movement between the central plate and the
structural element. In this setup the pieces of visco-elastic
and/or frictional material(s) can preferably be arranged between
the side plate and the central plate and thus provide a
visco-elastic dampening or friction between these plates. In a
further preferred embodiment, two side plates are accomplishing the
central plate, each being arranged symmetrically around the central
plate. Each of the two side plates are connected pivotally or fixed
to one of the structural members or to a brace of the bracing
system, the braces are either fixed to or pivotally connected to
members of the frame structure at the other end. In this setup it
is preferred to adapt two pieces of visco-elastic material or
pieces friction material, each piece being arranged between a
respective one of the side plates and the central plate.
[0088] The friction material is intended to maintain a constant
frictional force over a period of time and even after many cycles
of movement. It has been found, that a friction material selected
from the group consisting of: steel, anti-corrosive steel, brass,
aluminium and any alloys comprising aluminium and any other steel
material and composites of steel and plastics and composites of
plastics and fibres of glass, carbon, kevlar and composites of any
ceramics materials and fibres of glass, carbon or kevlar are
preferred.
[0089] Similarly, the third material may preferably a material or a
composition of materials selected from the group consisting of:
steel, anti-corrosive steel, brass, aluminium and any alloys
comprising aluminium and any other steel material and composites of
steel and plastics and composites of plastics and fibres of glass,
carbon, kevlar and composites of any ceramics materials and fibres
of glass, carbon or kevlar.
[0090] Furthermore it has been found that the side plates and/or
the central plate may preferably be made of steel, anti-corrosive
steel or brass is suitable but other materials are adaptable such
as aluminium or any alloys comprising aluminium or any other steel
material or composite of steel and plastics or composites of
plastics and fibres of glass, carbon, kevlar or similar or
composites of any ceramics materials and fibres of glass, carbon,
kevlar or similar.
[0091] Preferably the bracing system comprises any of the features
of the damper according to the present invention. The device for
dampening could preferably comprise at least two side plates as
earlier mentioned and which are interconnected at at least one of
their ends by means of an interconnecting element, and wherein a
brace is mounted to the interconnecting element. In a further
preferred embodiment at least one of the side plates are being
interconnected to one of the structural elements by means of a
brace, and wherein the central plate is connected or mounted to
another one of the structural elements. Furthermore at least one of
the side plates could be connected to one of the structural
elements by means of two braces, the two braces being connected to
opposite ends of the side plate(s), and wherein the central plate
is connected or mounted to another one of the structural
elements.
[0092] The bracing system can be arranged with the side plates
being connected to one of the structural elements by means of two
braces and the damper being arranged in a V-shaped bracing. In some
technical literature this kind of bracing is referred to as being
an invert-V bracing or a Chevron Bracing. Similarly the bracing
system can be arranged with at least one of the side plates being
connected to one of the structural elements by means of two braces
and the damper being arranged in a D-shaped bracing, and similarly
the bracing system can be arranged with at least one of the side
plates being connected to one of the structural elements by means
of two braces and the damper being arranged in a K-shaped bracing.
The choice of arrangement may depend on the actual situation and
will be selected by a professional designer.
DETAILED DESCRIPTION OF THE INVENTION
[0093] A preferred embodiment of the invention will now be
described in details with reference to the drawing in which
[0094] FIG. 1 shows a device for base isolation the device
comprising four dampers,
[0095] FIG. 2 shows a side view of a system with a damper
connecting a structural system to a foundation,
[0096] FIG. 3 and FIG. 4 show the mechanism of the dampers when the
base is rotating because of torsion,
[0097] FIG. 5 shows a side view of a system similar to the one
shown in FIG. 1 including a spring for holding the first structural
member in an original position wherein the first and second
structural members are in a mutual position above each other,
[0098] FIG. 6 shows a specific configuration of the device for
dampening movement of a machine,
[0099] FIGS. 7, 8 and 9 shows three alternative embodiments of the
device shown in FIG. 6,
[0100] FIG. 10 shows an embodiment of the device comprising a
sliding member,
[0101] FIGS. 11 and 12 shows alternative embodiments of the device
shown in FIG. 10,
[0102] FIG. 13 is a perspective picture of a friction damper device
according to the present invention,
[0103] FIG. 14 shows a steel frame with a friction damper
device,
[0104] FIG. 15 shows the mechanism of the damper for dampening
movement of a frame,
[0105] FIG. 16 shows the flexibility of using the friction damper
in different types of bracing systems,
[0106] FIG. 17 shows a damper with to side members and a central
plate and two pieces of a visco-elastic material,
[0107] FIG. 18 shows the damper of FIG. 17, including two pieces of
a friction material,
[0108] FIG. 19 shows the damper of FIG. 18, further including two
pieces of a third material, e.g. a disc made of brass,
[0109] FIG. 20 shows the damper of FIG. 18, further including two
pieces of a piezoelectric material,
[0110] FIG. 21 shows the damper device used in a cable stay
bridge,
[0111] FIG. 22. shows a damper for dampening pounding,
[0112] FIG. 23 shows a damper for dampening rectangular panels,
and
[0113] FIG. 24 shows a damper wherein a dampening member of a
friction material is arranged in one rotational joint and a
dampening member of a visco-elastic material is arranged in another
joint.
[0114] As shown in FIGS. 1 and 2, the device according to the
present invention comprises a first structural member 1 and a
second structural member 2. The first member is rotationally joined
to at least two elements 7 of a first group of elements (in FIG. 2,
only one of these elements is shown). The second structural member
is also rotationally joined to at least two elements of a second
group of elements 4 (in FIG. 2, only one of these elements is
shown). The elements of the first group of elements are
individually joined to an element of the second group of elements
in rotational joints 6. In at least one and preferably in each of
the joints, the parts are clamped together by clamping means, e.g.
a bolt 8 extending throughout both parts of the joint.
[0115] In one of the joints or in each of the joint, a dampening
member 3, 5 may be arranged for dampening the movement of one of
the parts in relation to the other of the parts of the joint. The
dampening member 3,5 can be a piece of a material adapted to reduce
the ability of one of the joint-parts to move in relation to the
other part of the joint. As an example, a piece of a rubber
material arranged between the two parts of the joint and in contact
with both parts. Preferably, the dampening member is either a piece
of a friction material, e.g. an asbestos containing material known
from brakes or clutches or the member is a piece of a visco-elastic
material, e.g. a relatively thick and soft silicone pad arranged
between the two parts, e.g. adhesively bonded to one or both of the
parts. Moreover, the dampening member may comprise one or more
pieces of both types of material, e.g. a sandwich construction with
one or more layers of a visco-elastic material and one or more
layers of a friction material. The dampening member may also be
made from a material which is visco-elastic and which on its
surfaces has a high surface friction, i.e. a combination between a
visco-elastic material and a friction material.
[0116] The damper can be arranged in different ways. As seen in
FIG. 1, the damper may have not only 2 but up to 4 or even more
sets of rotational, frictional or visco-elastic joints or dampers
11, one on each of the sides of the rigid structures 1,10. Each set
of joints comprising at least one joint between an element and the
first structure, one joint between another element and the second
structure and finally, one joint connecting the two elements.
According to another preferred embodiment, the damper may have a
number of frictional or visco-elastic dampers arranged on each side
of the rigid structures or at least on some of the sides of the
rigid structures. As an example it may be an advantage to provide 4
frictional dampers along two of the four sides of the rigid
structures, 2 along each side. In this way, space will be saved on
the other 2 of the 4 sides of the rigid structures. There may even
be provided 2 or more rotational dampers along each of the 4 sides
of the rigid structures.
[0117] In FIG. 2 the device is shown in a side view. The device is
provided with a first and a second structural member 1,2. The first
structural member is 4, 7. The first structural member 1 is
attached by a rotational joint 8 to the element 7 of a first group
of elements, which element in the joint 6 is connected to an
element of the second group of elements. The elements of the first
group of elements and/or the hinge pins of the rotational joints 8
may be made from steel or any other suitable material such as
carbon fibres composite materials including polyester or epoxy
resins or from ceramics. The structural members 1,2 is connected to
respective parts of a building structure to be dampened, e.g. to
the foundation and the first level of the building respectively, so
that the entire building is allowed to move in the horizontal
plane. The elements 4,7 are interconnected in a joint with the
hinge pin 6. When the structural element (or building) 10 moves,
the movement will cause that the elements 4,7 to rotate against
each other in mutually opposite directions around the hinge pin. In
the joint, the dampening member 3 will cause a frictional or a
visco-elastic resistance against the movement and thus dampen the
movement of the building 10. The device may further have any number
of dampening members, e.g. in the form of circular disc shims 3,5
of friction pad material or visco-elastic material placed between
the parts of the rotational joints. The friction or visco-elastic
pads are ensuring stable frictional or visco-elastic force acting
on the joint-parts. Friction pad material or visco-elastic material
may further be placed in one or both of the rotational joints
connecting the elements of the first and second group 4,7
respectively to the first and second structural members 1,2.
[0118] In a preferred embodiment of the invention the damper
comprise two elements, each one of them connected to a separate
platform. As seen in FIG. 2 the element 7 is pivotally connected
via a pin 8 to the first structural member 1 and thereby e.g. to
the foundation of a building. The dampening member 5 reduces the
ability of the element to rotate in relation to the first
structural member. Additional elements could be arranged in serial
with the element 5 or instead of the element 5, e.g. for adjusting
the height of the element 7 and thereby the height of the second
structural element in relation to the first structural element.
[0119] Similarly, the element 4 is pivotally connected via pin 8 to
the second structural element 2 through the member 5.
[0120] The joint 6 may be provided with a hinge pin, e.g. a bolt,
connecting the plates 4 and 7. The bolt may preferably be a
pretension bolt.
[0121] Several disc spring washers could be inserted between the
head or the nut of the bolt of joint 6 and one of the respective
elements 4 and 7. The disc spring washers will ensure constant
pressure on the friction pads and thus a relatively constant
counter force against mutual rotation of the parts of the
joints.
[0122] The first and second structural members should preferably be
strongly rigid structures. They can slide on each other by
different types of sliders and isolators 9. As sliding or isolating
material rubber, steel, metal or ball bearings may be used. It can
also be any solid block that can move or slide. According to one
layout, the second structural member 2 slides on the first
structural member 1 via a ball bearing with an upwardly extending
free ball surface, the ball being arranged in a bearing attached to
the first structural member and being allowed freely to roll. The
second structural member is provided with a parabolic surface
defining an upwardly extending dome shape in which the ball may
support the second structural member 2. If the second structural
member 2 is off-set in relation to the first structural member 1,
the
[0123] When designing a damper for a specific purpose, it should
taken into consideration that there is a relationship between the
size of the horizontal movement of the rigid structures and the
rotational movement of the rotational dampers. Preferably the
damper should designed so that even very small horizontal movements
of the rigid structures effects considerable rotational movement of
the rotational damper or dampers and thus enables the damper or
dampers to dissipate as much energy as possible. By making the
elements 4 and 7 as short as possible, the best possible
relationship between the horizontal movement of the rigid
structures and the rotational movement of the rotational dampers
may be achieved and thereby most energy will be dissipated.
[0124] FIGS. 3 and 4 shows two different situations wherein the
system is displaced from the unloaded "original" position of FIG.
1.
[0125] FIG. 5 shows a side view of a system similar to the one
shown in FIG. 1. The system comprises two structural members in the
form of two quadrangular frames. The two frames are connected via a
number of rotational joints. The rotational joints are provided
with a number of disc springs 51 arranged to ensure a constant
clamping pressure against the dampening members. In order to allow
the one frame to move in relation to the other frame, and yet to
ensure, that the frames, over time, stays at least substantially on
top of each other in an "original" mutual position, the structural
members 1,2 are biased towards the "original" position by means of
one or more strong springs 52 forcing the structural members
towards the "original position".
[0126] FIG. 6 shows a configuration of the device, wherein the
first structural member 61 is comprised in a heavy foundation block
62 and wherein the second structural member 63 is comprised in a
foundation for a centrifugal machine 64, i.e. a machine with the
need for dampening vibrations. As shown, the first structural
member 61 is joined to a first and a second element 65, 66 via
first and second rotational joints 67, 68. The first element 65 is
again joined to a third element 69 via a third rotational joint 70.
The second element 66 is joined to the third element in a fourth
rotational joint 71. The second structural member 63 is joined to
fourth and fifth elements 72,73, which elements are interconnected
in a fifth rotational joint 74. The fifth rotational joint and the
fourth rotational joints are interconnected by a sixth element 75.
As indicated in FIG. 6, the device allows the centrifugal machine
to move in all directions of a horizontal plane. Frictional and/or
visco-elastic resistance in the joints will dampen movement in any
direction.
[0127] FIGS. 7 and 8 shows two alternative embodiments of the
device shown in FIG. 6. In both Figs, the sliding member 81 is
provided to provided either frictional and/or visco-elastic
resistance against sliding between the two elements 82, 83. FIG. 9
shows a simpler embodiment of the device shown in FIG. 6 with a
reduced number of rotational joints and elements.
[0128] FIG. 10 shows an embodiment of the device, wherein the rigid
joint 101 connects the element 102 with the structure, e.g. a
machine, 103 to be dampened. The rotational joints 104 and 107 are
provided to dampen mutual movement between the respective
elements--the joint 104 dampens movement between element 105, 106
and 102, whereas the joint 107 dampens movement between the
elements 106 and 108. The joints 104 and 107 may be provided with a
dampening member for provision of a friction and/or visco-elastic
resistance. The system may be provided additionally with a spring
or a set springs allowing the structure 103 to return after
displacement to its original position. The spring or set of springs
may be provided either between the structure 103 and a fixed point
of the surroundings, e.g. a point of the foundation or the spring
or set of springs may be provided integrated into one or both of
the rotational joints 104 an 107.
[0129] FIG. 11 shows an alternative embodiment of the device shown
in FIG. 10. In this embodiment, horizontal movement of the machine
is dampened by friction and/or by visco-elastic resistance in joint
112. In the combined linear and rotational joint 111, the element
113 is allowed to slide horizontally and rotate around the hinge
pin 114. The system may be provided additionally with a spring or a
set springs allowing the structure 115 to return after displacement
to its original position. The spring or set of springs may be
provided either between the structure 115 and a fixed point of the
surroundings, e.g. a point of the foundation or the spring or set
of springs may be provided integrated into the rotational joint
112.
[0130] FIG. 12 shows yet another embodiment of the damper shown in
FIG. 10. In this assembly, the machine is dampened by two
rotational joints 121,122. A spring 125 is connected between the
rotational joint 123 and joint 124. Elements 127 and 128 are
separately connected to joint 124 by a hinge. In order for the
structure, e.g. a machine 126, not to rotate, it should preferably
be supported by a plurality, e.g. 2, 3, 4 or more assemblies of the
shown kind.
[0131] The remaining Figs. all shows various embodiments of a
damper according to the second aspect of the present invention.
[0132] As seen in FIGS. 13 and 14, a damper according to the
present invention may have a central plate 131 provided with a hole
138 for attachment of the plate e.g. to an upper frame 1418 of a
structural system. The damper is further provided with two side
plates 134. The side plates are also provided with holes for
attaching the side plates to braces 1413. Shims of either a
friction material or a visco-elastic material 133 has been arranged
between the central plate 131 and the side plates 134. The bolt
132, the nut 135 and the disc springs 136 serves for applying a
compressive clamping force against the pads or shims of
visco-elastic or friction material. If the shims is made of a
visco-elastic material, they may be glued or in any similar way
fastened to the steel plates or as an alternative, the disc or
discs may simply be loosely arranged between the steel plates. If
the friction between the steel plates and the shim(s) is relatively
high compared with the visco-elastic resistance against movement of
the steel plates, it will be ensured that the movement will be
visco-elastically damped before slipping between the steel plates
and the visco-elastic disc(s), if slipping should occur. A washer
137 may be inserted between the side plate and the disc
springs.
[0133] When the damper is installed in a structural frame, as seen
in FIG. 14, it follows the horizontal motion of the frame--as seen
in FIG. 15. Due to the hinge connection between the central plate
and the upper column and hinge connections between the side plates
and the braces 1413, again being pivotally connected to the base
column 1417, the forces of the movement of the structural frame is
being transferred rotationally to the dampening parts--as can be
seen in FIG. 15. When the displacement of the structural frame
starts, the damper will dissipate energy by means of the
visco-elastic forces which starts to build up.
[0134] When the applied forces in the damper exceed the frictional
forces, a sliding between the central plate and the visco-elastic
or frictional shims takes place. The plates now slides in a
circular movement around the hinge pin or bolt. Due to the tensile
forces in the bracing a sliding between the shims of friction
material and the side plates or between the shims of frictional
material and the shims of a visco-elastic material also. In the
sliding phase, the damper will dissipate energy by means of
friction between the sliding surfaces. This phase will keep on and
change to the visco-elastic phase when the load reverses its
direction.
[0135] This process of moving from phase to phase is repeated upon
reversal of the direction of the force application.
[0136] In order to keep a constant clamping force when the damper
is in operation, one or more disc springs 136 are preferably
mounted between the bolt head and the side plate, between the nut
and the side plate or at both sides. The spring could be of any
kind but in a preferred embodiment of the invention a combination
of discs springs 136 and washers 137, such as Belleville Washers,
are used. These springs are initially cone shaped annular disc
springs that flatten under compression. The washers are placed in
order to prevent any marks on the steel plates due to the disc
springs when they are in compression
[0137] The damper is based on a very simple design and comprises
only parts that are easily produced. At the same time it is easy to
assemble and very flexible in arrangement. As seen in FIGS. 14, 15
and 16, the damper can be arranged in different configurations as
well as in different types of bracing systems.
[0138] The two side plates 134 connect the damper to a bracing
system such as a Chevron bracing--as seen in FIG. 14--or similar
arrangement of braces e.g. in a D shape or a K shape. The bracing
system could have bars 1413 being pre-tensioned in order to prevent
them from buckling due to the compression force but. However, the
bracing system could also have structural members capable of
absorbing compression. The braces are preferably pivotally
connected at both ends 1401 and 1403, by having a simple bearings
member for. connecting the bracing to the damper 1402 and to the
column base connection 1417, as shown in FIG. 14. The frame 1418 is
the upper frame column.
[0139] The reason for, if necessary, using two side plates is to
increase the frictional surface area and to provide the necessary
symmetry to obtain plane behaviour of the device. All plates and
the frictional pads have a centred hole for assembly with a bolt
132 with a nut 135 or similar kind of confining hinge pin. The bolt
or similar hinge pin compresses the three plates 131 and 134 of the
damper and the visco-elastic or frictional pads 133 in a hinge like
connection. At the same time, the bolt 132 is used to control the
normal force applied on the visco-elastic friction pad discs and
the steel plates, whereby the dampening characteristics of the
damper is being changed.
[0140] FIG. 16 shows an example of multiple unit dampers, which
give the designer the ability to build a damper comprising several
units. The simplicity of the damper design allows the construction
of a device with multiple units, based on the requirements of the
designed applied forces and the space limitations.
[0141] FIG. 17A shows a side-view of the damper of FIG. 13. The
damper has a central plate 131 and two side plates 134. Between the
central plate and the side plates, shims or pads of either a
visco-elastic material or a friction material is arranged. The
material may also be a combination between a visco-elastic material
providing a frictional resistance on its surfaces.
[0142] FIG. 17B shows another embodiment of the damper of FIG. 17A,
wherein a plurality of disc springs 136 have been arranged adjacent
one or both of the side plates 134 or, as shown in FIG. 17B,
adjacent the washer 137. The disc springs 136 are important in the
case wherein the shims or pads 133 are made of a friction material
or at least in the case where the shims or pads have a frictional
surface characteristics being used for dampening the mutual
movement between the central plate and the side plates by
friction.
[0143] As seen in FIG. 18, more circular disc shims 133 of either a
visco-elastic and/or a friction material may be arranged between
the steel plates, e.g. the centre plate 131, and the shim(s) 133 of
a visco-elastic material or between more shims of visco-elastic
material. The movement thereby being damped by a combination
between the visco-elastic dampening of the visco-elastic material
and the friction dampening of the friction material. The
visco-elastic dampening will typically occur already for very small
vibrations of the structure, whereas the friction dampening occurs
as the movement becomes so strong that slipping between the shims
and/or the steel plates occur.
[0144] As seen in FIG. 19, even more side-plates 134 and/or shims
133 of a third material, e.g. steel plates, may be arranged between
any of the other shims of either visco-elastic material or friction
material or between one of the shims and one of the steel plates.
The plates are introduced in order to ensure a uniform pressure on
the entire surfaces of the visco-elastic shims and/or the friction
shims.
[0145] As seen in FIG. 20, even more shims 2021 of a piezoelectric
material may be arranged between any of the other plates, in this
case between side-plates 134 and visco-elastic shims 133. By
application of an electrical voltage to the piezoelectric material,
the size of those plates will change. Thereby, the pressure against
the visco-elastic shims and/or the pressure against the friction
shims will change and accordingly, the characteristics of the
damper will change. In general, the side plates 134 and a plurality
of shims either of a friction material or shims of a visco-elastic
material may be arranged in any order. As an example, in the order
from the central plate and towards the washer 137, the plates and
discs may be as follows:
[0146] visco-elastic, friction, visco-elastic, a third material
(e.g. a steel disc), and a side plate, or
[0147] visco-elastic, a third material (e.g. a steel disc),
friction, visco-elastic, and a side plate, or
[0148] friction, visco-elastic, a third material (e.g. a steel
disc), visco-elastic, and a side plate, or
[0149] friction, visco-elastic, friction, a third material (e.g. a
steel disc), and a side plate.
[0150] All possible combinations between material may be used
depending on the desired dampening characteristics.
[0151] FIG. 21 shows the damper 212 in three different situations
for dampening vibrations in bridge cables. The bridge cable 211 is
connected to a fixed part of the bridge through sets of dampened
rotational joints.
[0152] FIG. 22 shows two adjacent building structures 221, 222
being interconnected by a number of elements 223 interconnected in
dampened rotational joints 224. The movement of both of the to
buildings may thus be dampened. The dampening mechanism thus
protects the buildings from pounding each other.
[0153] FIG. 23 shows a wall damper specifically adapted to dampen
movement of small structures, e.g. houses or rigid frames such as
wall panels being relatively high compared to their width, i.e. a
structure having two side surfaces 231 which are relatively long
compared to other side surfaces 232 of the structure. The damper
233 is provided in one or both of either the top and/or the bottom
surfaces, i. e. at one or both of the end parts of the relatively
long side surfaces of the structure. A plurality of such dampers
may be provided in these areas of the structure. Each damper is
attached to the structure 239 which could be a rigid panel or a
rigid frame. The dampers thus connects the frame or panel to a
surrounding frame or panel 240, via first and second rotational
joints 237, 238 respectively. One or both of the rotational joints
may be dampened by dampening members, e.g. a pad of a visco-elastic
material or a pad of a friction material.
[0154] FIG. 24 shows a combined friction and visco-elastic damper
comprising 2 dampened rotational joints 241, 242. A first of the
joints 241 is dampened by a friction material 243, arranged between
the centre plate 244 and the side plates 245, 246. A visco-elastic
material arranged in a similar way dampens the second of the joints
242.
* * * * *