DK1815068T3

DK1815068T3 - Device for damping oscillation movements in a building

Info

Publication number: DK1815068T3
Application number: DK05795034.7T
Authority: DK
Inventors: Uwe Starossek
Original assignee: Soletanche Freyssinet
Priority date: 2004-11-09
Filing date: 2005-10-21
Publication date: 2018-08-13
Also published as: KR101353281B1; KR20070085873A; WO2006050802A1; EP1815068A1; DE102004053898A1; EP1815068B1

Description

The invention concerns a device with damping vibrations in a building, in particular in a bridge.

There is need for increasingly large spans in bridge building. For example, the Akashi Kaikyo bridge erected at the end of the 90s in Japan has a span of almost 2000 m. The planned bridge for crossing the strait of Messina in Italy is planned to have a span of over 3 km. With these extreme bridge lengths, the problem of tendency to vibration in these support structures comes increasingly to the fore. In the construction of bridge supports with large spans, a particularly important effect is the so-called flutter stability of the bridge. This is an aeroelastic phenomenon of wind induced bridge fluttering, in which self-induced, coupled bend and torsion vibrations or uncoupled torsion vibrations of the bridge support occur. Contrary to so-called externally-induced vibrations, which can for example occur as a result of wind gusts or by periodic vortex shedding, self-induced vibrations involve exciting forces which result from a shifting of the bridge. The air forces acting on the support structure influence the dynamic characteristics of the entire aeroelastic system, in particular rigidity and damping parameters. These changes occur also in the case of temporally constant wind speed. If the wind speed reaches a certain critical value, the structural damping of the bridge support is removed. When the wind speed increases further, a system can arise with negative total damping, in which a small initial displacement leads to a growing vibration with virtually unlimited amplitude and thus to a failure of the bridge support structure. The critical wind speed (Ucr) is the structural key word for the flutter stability of bridges. It is known that Ucr decreases with decreasing rigidity and damping of the bridge. Particularly bridges with a large span, however, have a low rigidity, so that in the case of these bridges the problem of fluttering occurs.

For the stabilisation of flutter-endangered bridge supports, a variety of methods and devices can be used. Basically, these can be divided into constructive, active and passive methods. The constructive stabilisation relates to structural measures, such as for example the increase of the torsional rigidity of the support or the addition of additional oblique cables. As passive vibration dampers, passively vibrating additional masses come under consideration, which are described as shock absorbers.

The active vibration dampers can be divided into actively mechanical and actively aerodynamic vibration dampers. The latter are based on the approach of modifying suitably the flow field forming around the bridge supports in order to generate a stabilising effect. For example, lateral flaps can be provided at the bridge supports, which are positioned into the wind such that a stabilising force is exerted as a result of the air which is flowing past, compare for example EP 0 627 031 BI. In the case of the actively mechanical flutter control there occurs a control of, for example, the torsional vibration of the bridge support by means of an additionally mounted torsional moment. For one embodiment, the additional torsional moment is generated by horizontally slidable damping masses in the bridge supports. The generation of a stabilising torque for the bridge supports by means of a masses rotating in the centre of the ridge cross-section is also under consideration. The mentioned devices have inter alia the disadvantage of a relatively large energy requirement and thereby reduced operational reliability.

In addition to the previously described critical phenomenon of fluttering in the case of bridges, similar vibration phenomena occur also in the case of buildings, where they are described as galloping. In addition to these vibrational phenomena which endanger the stability, there occur in the case of buildings and support structures also vibrations externally induced by wind, traffic, earthquake and further external influences, which can compromise both the usability and the stability and which must also be damped and suppressed. A device provided for installation at a structure, said device having an aerodynamic control surface and a spring element, is described in US 2 270 537 A.

The task of the invention is the provision of a device for damping vibrations at buildings and support structures, which suppresses externally-induced vibrations with high operational reliability, with easy measures and with as little power energy input as possible, and which effectively increases the critical wind speed for self-induced vibrations (e.g. fluttering). Both torsional vibrations and vibrations in specified directions should here be suppressed.

According to the invention, the task is carried out by a device with the characteristics from claim 1. The subject matter of sub-claims 2 to 24 form advantageous embodiment.

The device according to the invention serves to damp vibrations at buildings. It possesses at least one aerodynamic control surface which is rotatably and/or slidably mounted at the building. In addition, at least one mechanical shock absorber is provided which is kinematically coupled with the control surface. The device according to the invention, also described as aeroelastic shock absorber, serves to damp vibrations at buildings. It possesses at least one aerodynamic control surface which lies in the wind flow and which is rotatably and/or slidably mounted, which can be formed as control plate, movable edge or wing element, wherein the control surface is necessarily kinematically coupled with the mechanical shock absorber. The necessarily kinematic coupling is preferably carried out by movable mechanical elements, such as for example transmission levers or transmission gears. The mechanical shock absorber has a spring element which exerts a restoring force into a predetermined position on the mechanical shock absorber. The mechanical shock absorber is a vibration-capable secondary system which favourably influences the vibrational behaviour of the building (main system). In addition, the mechanical shock absorber has at least one mass body. The device according to the invention has thus no drive, which would make necessary an external energy supply.

In addition, the mechanical shock absorber has, in addition to the wing element, another damping element. The mechanical shock absorber is connected with its comparatively small mass via the spring element and via the damping element with the building, in particular with its support structure. Its degree of freedom of motion is the rotation around a stationary, with respect to the building, terminal or the displacement relatively to the building in a predetermined direction. The shock absorbing effect arises through the forces of inertia of the mass and the damping in the possibly added damping element. Mechanical shock absorbers per se have been known for a long time.

In the case of the aeroelastic shock absorber, flow forces are exerted on the aerodynamic control surface and on the building, in addition to the forces of inertia and damping forces being exerted in the case of the mechanical shock absorber. As a result of the necessarily kinematic coupling, the vibrations of the shock absorber transmit to the control surface, whereby angle of incidence and/or position of the control surface vary temporally, also in vibrational manner. The flow forces being exerted on the control surface and the building are therefore, with the vibration of the shock absorber, temporarily variable, and with correct coordination and sufficient wind speed exert an additional shock absorbing effect on the building. The shock absorbing effect of the aeroelastic shock absorber exceeds significantly the forces of inertia and damping forces of the mechanical shock absorber. Vibration-encouraging forces are effectively countered by the aeroelastic shock absorber, externally-induced vibrations are suppressed and the critical wind speed for self-induced vibrations (for example fluttering) is increased.

Simultaneously with the controlling of the flow forces through the movement of the shock absorber, the flow forces being exerted on the aerodynamic control surface can react via the existing necessary connection also to the vibration of the mechanical shock absorber. This influence is however not necessary for the effectiveness of the device and can inasmuch as it is disturbance, be minimised through suitable positioning of the control surface or in another way.

In a preferred embodiment, the coupling between mechanical shock absorber and control surface can be effected such that amplitude, phase and/or frequency relationships between a vibrational movement of the mechanical shock absorber and the vibrational movement of the aerodynamic control surface can be adjusted. The coordination can thus be suited to changing operational conditions, such as a changeable wind speed.

In a preferred embodiment a control can be provided which controls the amplitude, phase and/or frequency relationships accordingly.

The aerodynamic control surface can be formed as movable edge or wing element, which attaches directly to the building and is rotatably mounted around a point which is stationary in relation to the building. Alternatively, the aerodynamic control surface can be formed as a plate set apart from the building, which is connected rotatably and/or slidably with the building via pylons. By means of suitable rod assemblies, the movement of the plate can also be guided such that a rotation occurs around a point which is non-stationary in relation to the building.

In a possible embodiment of the aeroelastic shock absorber, the aerodynamic control surface is formed as a wing element, which protrudes freely with one section from the building.

In a possible embodiment, the wing element forms, with its mass disposed to both sides of the bearing point in interplay with a spring between wing element and building, the mechanical shock absorber. In an alternative embodiment, the wing element is formed with one arm which protrudes into the building and is there connected by means of a spring with the building. Here, wing element, arm and spring together form the mechanical shock absorber.

In a preferred extension of the device according to the invention the arm of the wing element has at its end a mass body.

In a preferred embodiment, at least two aeroelastic shock absorbers are disposed in pairs at opposite sides of an axis, wherein both torsional vibrations around the axis and vibrations in certain directions are to be damped or absorbed.

According to provided spring constants and where necessary also damping constants, a plurality of spring or damper elements, respectively, can also be provided, the fastening points of which are preferably spatially distributed in the building or support structure.

Two preferred embodiments of the device according to the invention are described in more detail using embodiment examples.

Figure 1 shows a perspective view of a section of a suspension bridge and figure 2 shows a schematic view of the bridge support in cross-section with two damping apparatuses according to the invention of a first embodiment, in each case one on each side of the bridge support, and figure 3 shows a schematic view of a building with a damping apparatus according to the invention in a second embodiment, in which the control surface is set apart from the building.

Figure 1 shows a bridge support 10 in section, as it is used in the case of suspension bridges. The stiffening support 12 is held by suspension members 14 at cables 16 spanned between the masts of the bridge. On both sides of the stiffening supports 12 are mounted rotationally mounted wing elements.

Figure 2 shows the body of the bridge support 12 in cross-section. The longitudinal axis of the bridge support is referenced with 18. To the sides at the bridge support protrude two wing elements 20, 22, which are each pivotably supported in a bearing point 24, 26 and form the aerodynamic control surfaces. On their interior side, in the bridge support 12, the wing elements 20, 22 have arms 28, 30 at the ends of which is provided respectively one mass body 32, 34.

In the shown embodiment example of figure 2, each arm 28 or 30 is connected via a spring element 36 or 40 and a damping element 38 or 42 with the bridge support 12. Wing elements 20, 22 and mass bodies 32, 34 and springs 36, 40 are in each case disposed such that, without external force influence, the wing elements 20, 22 remain in a predetermined position. A displacement of the wing elements out of their rest position leads to a vibration which damps the movement of the bridge support 12.

In the embodiment example from figure 2, the mechanical shock absorber comprises a plurality of respectively involved masses (mass body 32 or 34, arm 28 or 30, wing element 20 or 22), a spring 36 or 40 and a damping element 38 or 42. Its degree of freedom of movement is the rotation around the bearing point 24 or 26. It is stimulated to vibrations by vertical and torsional vibrations of the bridge support. The vibrational stimulation of the shock absorber and thus its effectiveness necessitate in general an imbalance of the mass distribution and therewith a pre-tensioning of the spring 36 or 40 in the static rest position. In the shown embodiment example, the mass of the wing elements should be as small as possible in the interest of high effectiveness of the mechanical shock absorber. The necessary kinematic coupling between mechanical shock absorber and aerodynamic control surface comprises in this embodiment example only the arm 28 or 30 connecting the two elements.

The shock absorbing effect of the mechanical shock absorber arises through the forces of inertia of the masses involved and the damping forces in the damping element.

In the case of the aeroelastic shock absorber of the embodiment example, the rotation of the mechanical shock absorber (relative to the bridge) is transferred to the aerodynamic control surface 20 or 22 which is rotationally supported and lies in the wind flow, which control surface is assigned to the respective mechanical shock absorber. Thus, the flow field is dynamically changed and in addition temporarily changeable air forces are induced. Through the coordination of the shock absorber, these counter the vibration inducing forces, whereby externally-induced bridge vibrations are calmed and the critical wind speed for the fluttering is raised.

The mechanical shock absorber according to the invention can also vibrate in a predetermined straight direction and can have, instead of the lever connected rigidly with the aerodynamic control surface, also other necessary connections, such as for example translational levers and gears. The coordination of the aeroelastic shock absorber takes place through the selection of mass m, spring constant k and damping constant c as the central mechanical parameters, the selection of the spacing of the mechanical shock absorber from the bridge axis, the selection of its degree of freedom of movement, the kinematics of the necessary kinematic connections and the contour and the mass of the aerodynamic control surfaces.

As previously already described, the main effect of the aeroelastic shock absorber consists in steering, by means of a vibrational movement of the aerodynamic control surface, the air flow at the building such that a build-up is prevented and the building is stabilised. Simultaneously with the controlling of the flow forces through the movement of the shock absorber, the flow forces being exerted on the aerodynamic control surface can react via the existing necessary connection also to the vibration of the mechanical shock absorber. This influence can, according to building and design of the aeroelastic shock absorber, have a supporting effect or a disturbing effect. By means of a suitable mounting of the aerodynamic control surfaces or other measures, this reaction to the mechanical shock absorber can be suppressed.

An embodiment example in which this reaction is suppressed by the mounting of the control surface is shown in figure 3. In this case, the aerodynamic control surface comprises a plate 44 distanced from the building, said plate being connected with the building by a holding device 46. The plate is here rotatably supported around a bearing point 48 in the middle area of the plate. The necessary kinematic coupling with the mechanical shock absorber 60 located in the interior of the bridge support takes place via a movable linkage member 50, which is coupled selectively via a linkage member 52 or 56 with the plate 44.

The aeroelastic shock absorber can be provided on one side or on both sides (relative to the longitudinal axis of the bridge). In the case of two-sided disposition, both shock absorbers can be also coupled or operated independently from one another. The latter is shown in figure 2. If both shock absorbers are coupled (not shown), an according necessary kinematic connection is to be provided between the two shock absorbers. If, however, the two shock absorbers are independent from one another, there is the possibility of locking them on one side e.g. to the leeward side.

Not shown in the figures is a necessary kinematic coupling between mechanical shock absorber and aerodynamic control surface, which permits the adjusting of frequency ratios between the vibration of the mechanical shock absorber and the vibration of the aerodynamic control surface. The amplitude ratio can be adjusted in the case of a translational linkage e.g. by moving the connection points of the linkage members, as shown in figure 3 or similar. A rotational joint 58 is here fixedly connected with the first linkage member 52 and locked within a longitudinal hole 54 in the second linkage member 50. The adjusting can thus be carried out steplessly by sliding the rotational joint 58 in the longitudinal hole 54.

By connecting the first linkage member in the rear position 52 or in the front position 56, a phase ratio of 0° or 180° can be set, wherein the coupling of the front linkage member 56 can take place exactly the same way as the coupling of the rear linkage member 52 described above.

In the case of a reduction gearing, the amplitude ratio can be set step-wise or steplessly with an appropriate transmission or stepless gear-unit.

The preferred embodiment example of the invention was described in connection with the bridge, but is in no way limited to bridges with respect to its employment. On the contrary, the device according to the invention can also be used in the case of horizontal vibrations, as they occur for example in the case of towers. In this case, the axis 18 then extends in vertical direction.

The aeroelastic shock absorber has as a particular advantage a high degree of economic efficiency and a high level of operational reliability, since there is no need for an external energy supply.

Claims

Apparatus for damping or suppressing vibrations in a building, comprising: at least one aerodynamic control surface (20, 22; 44) mounted as pivotal and / or slidable; - at least one mechanical absorber (60) having a a spring element (36, 40) capable of performing torsional oscillations or oscillations in a predetermined direction relative to the building, and at least one forcing, kinematic coupling between mechanical absorber and aerodynamic control surface, the mechanical absorber comprising at least one mass body (32 , 34), wherein the mechanical absorber comprises, in addition to the spring element, a damper element (38, 42) whereby both torsional vibrations and vibrations in predetermined directions are attenuated or suppressed.

Device according to claim 1, characterized in that the forced kinematic coupling between mechanical absorber and control surface is realized by movable mechanical elements such as, for example, transmission arms, transmission rods (50, 52, 56) or transmission gears.

Device according to one of claims 1 to 2, characterized in that the coupling between mechanical absorber and control surface enables adjustment of an amplitude and / or phase and / or frequency relationship between the oscillation of the mechanical absorber and the oscillation of the aerodynamic control surface.

Device according to claim 3, characterized in that the coupling comprises a rod having a first rod element (52 or 56) and a second rod element (50), whereby the amplitude ratio can be adjusted by the position of a connection point (58). between the rod elements (50, 52, 56) and the phase ratio can be set by the position of a junction between the rod element (52 or 56) and the guide surface (44).

Device according to one of claims 3 or 4, characterized in that a control is provided which controls the amplitude, phase and / or frequency ratio.

Device according to one of claims 1 to 5, characterized in that, as an aerodynamic guide surface, a movable edge or wing element (20, 22) is provided which protrudes freely from the building with a section.

Device according to claim 6, characterized in that the blade element (20, 22) is pivotally mounted at a bearing point (24, 26).

Device according to claim 7, characterized in that the wing element with its mass disposed on both sides of the bearing point (24, 26) forms the mechanical absorber.

Device according to one of claims 6 to 8, characterized in that the wing element (20, 22) comprises an arm (28, 30).

Device according to claim 9, characterized in that the wing element (20, 22), the arm and the spring element form the mechanical absorber.

Device according to claim 10, characterized in that the arm (28, 30) comprises at its free end a mass body (32, 34).

Device according to one of claims 1 to 5, characterized in that, as an aerodynamic control surface, a shield (44) displaced relative to the building is provided, which is connected to the building (12) via holding devices (46).

Device according to claim 12, characterized in that the shield (44) displaced relative to the building is mounted as pivotable and / or displaceable, whereby the movement of the shield is controlled so that a rotation about a pole which is stationary or non-stationary in relation to the building.

Device according to one of claims 1 to 13, characterized in that the flow forces acting on the aerodynamic control surface act back on the oscillations of the mechanical absorber.

Device according to one of claims 1 to 13, characterized in that the flow forces acting on the aerodynamic control surface, when selecting a suitable bearing of the control surface, do not act back on the oscillations of the mechanical absorber.

Device according to claim 15 with reference to claims 12 and 13, characterized in that, as an aerodynamic control surface, a shield is displaced relative to the building, and which is positioned so that the movement of the shield takes place as a rotation about a pole. in the middle area of the shield.

Device according to one of claims 1 to 16, characterized in that the mechanical absorber is coupled via two forced kinematic couplings to two aerodynamic control surfaces, which are arranged in pairs on opposite sides of a building axis (18), whereby both rotational oscillations about the axis (18) and oscillations in a predetermined direction, in particular in the direction perpendicular to the connecting line between the two guide surfaces, are attenuated or absorbed.

Device according to one of claims 1 to 16, characterized in that at least two aerodynamic control surfaces with respective associated mechanical absorbers and their forced kinematic coupling are arranged in pairs on opposite sides of a building axis (18), whereby both rotational vibrations about the axis (18) and oscillations in a predetermined direction, in particular in the direction perpendicular to the connecting line between two opposite control surfaces, are damped or absorbed.

Device according to claim 18, characterized in that at least one of the guide surfaces is arrested.

Device according to claim 18, characterized in that at least two mechanical absorbers are coupled to each other by means of a forced kinematic coupling.

Device according to claim 20, characterized in that the forced kinematic coupling for the mechanical absorber comprises a gearing device which enables the adjustment and control of amplitude, phase and / or frequency ratios.

Device according to one of claims 1 to 21, characterized in that for each mechanical absorber, several spring elements are provided.

Device according to one of claims 1 to 22, characterized in that for each mechanical absorber, several damper elements are provided.

Device according to claim 22 or 23, characterized in that the spring elements and / or the damper elements are fixed to different points.