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
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.
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.
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.
 US 4,480, 731
discloses a vibration damping apparatus incorporated in the crossing of diagonal members such as braces of a framed structure for damping vibration imparted by external force such as an earthquake or a strong wind. The apparatus comprises a plurality of rotatable members or discs, a resistive body disposed between the discs, and a pair or pairs of link bars causing relative rotation of the discs in response to the impartation of the external force, whereby the vibration is damped by the resistance force of the resistive body resisting to the external force.
Description of the invention
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.
The present invention relates to a device for dampening movements of structural and non structural elements in civil engineering structures, the device comprising:
- two side plates,
- a first piece of a visco-elastic material in a joint for visco-elastic damping of relative movement between the side plates,
- a first piece of a friction material arranged in contact with the visco-elastic material,
- clamping means for clamping the plates together, so as to provide a clamping force applying a compressive force against the visco-elastic material, and
- means for connecting each of the two side plates to respective ones of the structural elements, the device further comprising:
- a central plate, a second piece of a visco-elastic material, a second piece of a friction material, and means for connecting the central plate to a respective one of the structural elements, wherein
- the two side plates are arranged symmetrically around the central plate,
- each piece of the two pieces of a visco-elastic material is arranged between a respective one of the side plates and the central plate in said joint for visco-elastic damping of relative movement between the side plates and the central plate,
- each piece of the two pieces of friction material is arranged between and in contact with a respective one of the plates and the visco-elastic material for a combined frictional and visco-elastic damping of relative movement between the two side plates and the central plate, and
- each end of each of the two pieces of a visco-elastic material is fixed and non-slidable attached to an adjacent plate or to a piece of a friction material in said joint.
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.
The dampening of the movement arises from the relaxation and recovery of the polymers network after it has been deformed.
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 wails such as brick walls, panels and partition walls.
The damper device can be mounted in reinforced concrete frame structures with or without walls.
The damper device can be mounted in elevated water tanks to reduce their vibration response.
The damper device can be mounted in bridges and elevated highways The damper device can be used to reduce the vibration caused by elevated machines, which are mounted on a frame structure.
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.
The damper device can be mounted in ready-made garages.
The damper device can be mounted in portable metal tents for dampening the movements of the carrying columns and beams of the tent.
The damper device can be used to reduce the rotation of joints in frame structures.
The damper device can be mounted in several storeys industrial buildings.
The damper device can be mounted in timber frame structures.
The damper device can be mounted in metal towers.
The damper device can be mounted in one, or multiple storey houses.
The damper device can be mounted in cables of suspension bridges or cable stay bridges.
The damper device can be mounted in cables in pretension structures, e. g. stadiums or large halls, e. g. the Millennium Hall in London.
The damper device can be mounted in floors to damp the floor vibration caused by human or machines.
The damper device can be mounted in pipes that transferring fluids which cause some vibration through the fluid movements.
The damper device can be mounted in Oil, Gas, liquids, fuel tanks
The damper device can be mounted in roof ceilings that hold a false ceilings or heavy chandelier.
The damper device can be mounted in museums, e. g. underneath a table or a platform holding a statue etc.
The damper device can be mounted behind many types of furniture, e. g. cupboards.
The damper device can be mounted behind shelves which are used to store parts in factories or store houses.
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.
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.
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.
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.
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.
In a preferred embodiment of the invention the joint comprises a pin extending through each of the plates. 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
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: - a bolt member with a bolt head, - a nut with a nut head, 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.
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.
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 plates and/or between the nut head and a surface of one of the plates. 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 plates, and another disc spring or more disc springs arranged between the nut head and a surface of another of the plates. Preferably, a washer is placed between the disc spring (s) and the surface of the plates. 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, plates with a lower wall thickness may be chosen and accordingly, the weight of the damper may be reduced.
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.
Similarly, the third material may preferably be 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 keviar.
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.
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.
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
Embodiments of the invention will now be described in details with reference to the drawings. Figures 1-17 as well as figures 19-22 show embodiments not according to the invention.
Fig. 1 shows a device for base isolation the device comprising four dampers,
Fig. 2 shows a side view of a system with a damper connecting a structural system to a foundation,
Fig. 3 and Fig. 4 show the mechanism of the dampers when the base is rotating because of torsion,
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,
Fig. 6 shows a specific configuration of the device for dampening movement of a machine,
Figs. 7,8 and 9 shows three alternative embodiments of the device shown in Fig. 6,
Fig. 10 shows an embodiment of the device comprising a sliding member,
Figs 11 and 12 shows alternative embodiments of the device shown in Fig. 10,
Fig. 13 is a perspective picture of a friction damper device according to the present invention,
Fig. 14 shows a steel frame with a friction damper device,
Fig. 15 shows the mechanism of the damper for dampening movement of a frame,
Fig. 16 shows the flexibility of using the friction damper in different types of bracing systems,
Fig. 17 shows a damper with to side members and a central plate and two pieces of a visco-elastic material,
Fig. 18 shows a damper according to an embodiment of the invention being similar to the damper of Fig. 17, but further including two pieces of a friction material,
Fig. 19 shows the damper of Fig. 18, further including two pieces of a third material, e. g.
a disc made of brass,
Fig. 20 shows the damper of Fig. 18, further including two pieces of a piezoelectric material,
Fig. 21 shows the damper device used in a cable stay bridge, and
Fig. 22. shows a damper for dampening pounding.
As shown in Figs. 1 and 2, the device 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.
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.
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.
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.
In an embodiment 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.
Similarly, the element 4 is pivotally connected via pin 8 to the second structural element 2 through the member 5.
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.
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.
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.
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.
Figs. 3 and 4 shows two different situations wherein the system is displaced from the unloaded"original"position of Fig 1.
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".
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 viscoelastic resistance in the joints will dampen movement in any direction.
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.
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.
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.
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.
As seen in Fig. 13 and 14, a damper 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 viscoelastic 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 viscoelastically 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.
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.
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.
This process of moving from phase to phase is repeated upon reversal of the direction of the force application.
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 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.
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.
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.
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.
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.
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.
Fig. 18 shows a damper according to the invention having two side plates 134, a central plate 131, two pieces of a visco-elastic material 133 and two pieces of a fraction material 133. As seen in Fig. 18, the circular disc shims 133 of 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.
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.
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.
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 : visco-elastic, friction, visco-elastic, a third material (e. g. a steel disc), and a side plate, or visco-elastic, a third material (e. g. a steel disc), friction, visco-elastic, and a side plate, or friction, visco-elastic, a third material (e. g. a steel disc), visco-elastic, and a side plate, or friction, visco-elastic, friction, a third material (e. g. a steel disc), and a side plate.
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.
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.
Vorrichtung (1402) zum Dämpfen von Bewegungen von strukturellen und nichtstrukturellen Elementen (1418) in Tiefbaukonstruktionen, wobei die Vorrichtung umfasst:
- zwei Seitenplatten (134),
- ein erstes Teil eines viskoelastischen Materials (133) in einer Verbindung zur viskoelastischen Dämpfung der Relativbewegung zwischen den Seitenplatten (134),
- ein erstes Teil eines Reibungsmaterials (133), das in Kontakt mit dem viskoelastischen Material (133) angeordnet ist,
- Klemmmittel (132, 135, 136, 137) zum Zusammenklemmen der Platten (134), um eine Klemmkraft bereitzustellen, die eine Druckkraft gegen das viskoelastische Material (133) ausübt, und
- Mittel (1413) zum Verbinden jeder der beiden Seitenplatten (134) mit jeweiligen der Strukturelemente (1418), dadurch gekennzeichnet, dass
- die Vorrichtung ferner eine zentrale Platte (131), ein zweites Teil eines viskoelastischen Materials (133), ein zweites Teil eines Reibungsmaterials (133) und Mittel zum Verbinden der zentralen Platte (131) mit einem jeweiligen der Strukturelemente (1418) umfasst, wobei
- die beiden Seitenplatten (134) symmetrisch um die zentrale Platte (131) angeordnet sind,
- jedes Teil der beiden Teile eines viskoelastischen Materials (133) zwischen einer jeweiligen der Seitenplatten (134) und der zentralen Platte (131) in der Verbindung für eine viskoelastische Dämpfung der Relativbewegung zwischen den Seitenplatten (134) und der zentralen Platte (131) angeordnet sind,
- jedes Teil der beiden Teile von Reibungsmaterial (133) zwischen und in Kontakt mit einer jeweiligen der Platten (134, 131) und dem viskoelastischen Material (133) für eine kombinierte reibungs- und viskoelastische Dämpfung der Relativbewegung zwischen den beiden Seitenplatten (134) und der zentralen Platte (131) angeordnet ist, und
- jedes Ende jedes der beiden Teile eines viskoelastischen Materials (133) fest und nicht verschiebbar an einer benachbarten Platte (134, 131) oder an einem Teil eines Reibungsmaterials (133) in der Verbindung angebracht ist.
2. Vorrichtung nach Anspruch 1, wobei die Klemmmittel (132, 135, 135, 137) angepasst sind, um die Klemmkraft und damit die gegen das viskoelastische Material (133) ausgeübte Druckkraft zu variieren.
3. Vorrichtung nach Anspruch 1 oder 2, wobei das viskoelastische Material (133) angepasst ist, um die Dämpfungseigenschaft basierend auf der aufgeübten Druckkraft zu ändern.
4. Vorrichtung nach einem der Ansprüche 1-3, wobei das viskoelastische Material (133) aus der Gruppe ausgewählt ist, die aus Kautschuk, Acrylpolymeren und beliebigen viskoelastischen Materialien besteht.
5. Vorrichtung nach einem der Ansprüche 1-4, wobei die Verbindung einen Stift (132) umfasst, der sich durch jede der Platten (134, 131) erstreckt, um eine Drehverbindung bereitzustellen.
Vorrichtung nach Anspruch 5, umfassend einen Bolzen (132), wobei mindestens ein Teil des Bolzens den Stift bildet, wobei der Bolzen aufweist:
- ein Bolzenelement mit einem Bolzenkopf,
- eine Mutter (135) mit einem Mutterkopf,
wobei die Klemmkraft durch die Vorspannung des Bolzens (132) bestimmt wird.