MXPA98009867A - Stabilization of puen - Google Patents

Abstract

The present invention relates to a bridge platform 10 supported by tension carriers 11 and 12 and stabilized to reduce the overall aerodynamic lift of the platform 10 with the addition of aerodynamically designed stabilizers 19 and 20 that are secured with pivots around respective axes 21, generally longitudinal to the platform 10. The stabilizers 19 and 20 are driven by a mechanism 21 to 26 that can be operated by the angular movement between the platform 10 and the tension supports 11 and 12, to articulate the stabilizers 19 and 20 to a position that will generate a force in the presence of a transverse wind, to reduce the aerodynamic lift of the platform

Description

STABILIZATION OF BRIDGES FIELD OF THE INVENTION The invention relates to the stabilization of bridges comprising a platform supported by tension supports, and provides both a stabilized structure for bridges and a method for stabilizing an existing bridge.

BACKGROUND OF THE INVENTION Some types of bridges have a platform supported by tension supports from towers or similar structures, erected at the ends of the bridge or intermediate thereto. In the case of a suspended bridge, the tension supports are typically vertical cables, rods or chains that interconnect each longitudinal side of the platform to a corresponding catenary suspended between the towers. A bridge supported by cables also comprises a platform supported by tension supports, usually in the form of rods or cables, which extend from the longitudinal sides of the platform directly towards the towers. Since the disaster of the Tacoma bridge in 1940, it is well known that a suspended bridge can suffer P17 5 / 98MX dramatic structural failures due to the instability of vibrations by a sustained and modest load of the wind which caused a resonant oscillation in the platform that increased progressively until destruction occurred. The problems associated with wind loads on suspended bridges, and certainly on all bridges that comprise a platform supported by tension supports, become much more severe as the opening of the platform arch increases. With a very large arc opening, for example the one proposed for the Straights of the Messina, the wind load along the arc opening can vary in an essential way and can promote the essential asymmetric inclination and weight of the platform . Since the disaster of the Tacoma bridge, some proposals have been made to solve this problem. For example, in European Patent 0233528, it was proposed that a suspended bridge consisting of a suspended structure formed of catenary wires, vertical braces and an essentially rigid flat platform structure hung on the suspended structure, could be stabilized by aerodynamic elements having a profile of wings and that are rigidly fixed to the structure of the bridge to control the action of the wind on the structure, the aerodynamic elements comprise control surfaces P17 5 / 98MX of wings having a symmetrical profile and a positive or negative aerodynamic lift reaction together with a vibration velocity higher than the appropriate vibration speed for the bridge structure, the wing surfaces are fixed just below the lateral edges of the platform structure of the bridge, with its plane of symmetry inclined with respect to the horizontal plane, the structure of the bridge and the surfaces with control of wings interact dynamically in order to change the speed of vibration of all or at least about the maximum expected wind speed in the bridge area. Instead of using rigidly fixed wing profiles to the bridge structure, International Patent Application PCT / GB93 / 01862 (Publication Number WO 94/05862) teaches that a bridge platform can be made less rigid than the platform of the bridge. Existing bridges using fins or ailerons, provided on the side edges of the bridge platform, the fins or ailerons are mounted by pivots from the bridge platform for articulation between the extended position and the retracted position and are computer controlled to regulate the forces on the platform in response to the wind load. International Patent Application PCT / DK-P17 S / 98MX 93/00058 (Publication Number WC 93/16232) teaches a system for counteracting wind induced oscillations in composite beams of the bridge, in bridges supported by long cables, wherein a plurality of control fronts are arranged essentially symmetrically along the longitudinal axis of the bridge and are adapted to utilize the wind energy in response to the motion of the composite beams of the bridge for reducing movement, the control fronts are divided into sections in the longitudinal direction of the bridge, and a plurality of detectors are provided to measure the movements of the composite beams of the bridge, and a local control unit is associated with each section of the front of control and is adapted to control the front section of control in question, in response to the information of one or more detectors. These detectors are arranged to measure the movements or accelerations of the bridge at the referred point and to transmit a signal to the control unit, such as a computer, which uses an algorithm to apply a signal to a servo pump that controls the hydraulic cylinder to rotate the associated front control section. In this way, each control front section can be adjusted continuously in response to the movements of the composite beams of the bridge, at the point in question measured by the detectors P17 S / 98MX which are in the form of accelerometers. This invention essentially requires the provision of a complex electronic system that incorporates a significant number of accelerometers connected by extensive wiring along the composite beams of the bridge to the computers, and an associated hydraulic system for operating the control fronts. From document WO 93/16232 and other documents of the prior art, it is known that a bridge must comprise a platform supported by aerodynamically designed tension supports and stabilizers, mounted by pivots around their respective axes, generally longitudinal to the platform , for the articulation to a position that improves the stability of the platform. From these documents, it is also known how to provide a method for stabilizing a bridge having a platform supported by tension supports including wing profile stabilizers mounted around their respective axes, generally longitudinal to the platform.

SUMMARY OF THE INVENTION An object of the present invention is to enable a bridge to be stabilized without the use of an extensive electronic detection and control system.

P1745 / 98MX According to one aspect of the invention, each stabilizer is mechanically connected to the platform and to an adjacent tension support, through a mechanism that can be operated with angular movements between the platform and the tension support. along a longitudinal axis of the bridge, such that when there is an angular movement between a portion of the platform and the adjacent tension support, the associated stabilizer will be articulated by movement through the mechanism to a position that will generate a force in the portion of the platform, in the presence of a transverse wind. In this way, it is possible to stabilize a bridge by minimizing the coupling between the vertical and rotational movements of the platform, therefore any tendency to vibrate the structure is damped. Preferably, each mechanism includes a lever that is secured to the associated tension support and is pivotally mounted to the platform along an axis, generally parallel to the pivot axis of the associated stabilizer. Each mechanism can be arranged to amplify the articulation of its associated stabilizer with respect to angular movement. At least some outriggers may be mounted by pivots along their respective shafts directly to the platform, and may be arranged P1745 / 98MX to be articulated by means of its links mounted by pivots to their respective levers. At least some of the outriggers may be pivotally mounted along their respective axes directly to the platform and may be positioned to modify the aerodynamic properties of the platform. Alternatively, at least some of the outriggers may be mounted by pivots along their respective axes, either from the tension supports or from their respective levers. Preferably, in this case, each stabilizer is arranged to be articulated by a link pivoted on the platform. At least one of the stabilizers may be provided with an independent adjustment control surface. In this way the control surface can be adjusted in relation to the stabilizer, which alters the force that will be generated by the stabilizer and will be applied to the platform. Preferably, the outriggers are arranged in pairs mounted on opposite sides of the platform and are balanced by an interconnection link. In this case, the interconnection link is arranged, preferably, operatively between the mechanisms of the stabilizer pair.

P17 S / 98MX According to another aspect of the invention, a method includes the mechanical connection of the platform and the adjacent tension support when using a mechanism operable by the angular movement between the platform and the tension supports along the axis longitudinal of the bridge, as to articulate the stabilizers by the movement through the mechanism towards a position that will generate a force, in the presence of a transversal wind, to reduce all the aerodynamic lifting of the platform.

BRIEF DESCRIPTION OF THE DRAWINGS OR FIGURES Now, the invention will be described only by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic cross section through the platform of a stabilized bridge. in accordance with the present invention Figure 2 is a view similar to Figure 1, but illustrates the movement of a pair of outriggers during angular movement in a direction between the platform and the adjacent tension support along the longitudinal axis of the bridge Figure 3 is a view similar to Figure 2, but illustrates the movement of the stabilizers during P17 5 / 98MX the angular movement in the opposite direction between the platform and an adjacent tension support. Figure 4 is an amplification of the left portion of Figure 2, illustrating a form of mechanism operable by angular movement between the platform and the adjacent tension support. Figure 5 is a view similar to Figure 4, but showing a modification of the wing profile stabilizers. Figure 6 is a view similar to Figure 1, but illustrates the balance of a pair of stabilizers; Y Figure 7 is a view similar to Figure 1, but illustrates an alternative mounting for the outriggers on a different bridge platform.

DETAILED DESCRIPTION OF THE INVENTION It is well known that suspended bridges opening very long arc have a tendency to suffer vibrations, such as instability during conditions of very strong winds. One approach to this problem has been to increase the torsional stiffness of the bridge platform, thereby increasing the wind speed, which is when instability occurs. This is achieved by conventional structural techniques that inevitably increase the weight of the bridge platform and P17 5 / 98MX consequently also increase the weight of the suspension cables and the support structure. An alternative approach has been to increase the stability of the bridge platform through an actively controlled wing profile. This active stabilization closely follows the practice already adopted in aviation control systems, where the aerodynamic design or other control services are flexed in an appropriate manner by means of electric, pneumatic or hydraulic actuators in response to the detected motion of the vehicle, which in In this case, it is the local part of the flexible structure of the bridge platform that is going to stabilize. The present invention provides an alternative approach for activating the stabilization by controlling the wing profile mechanically linked by links connected to the suspension members of the bridge platform. In this way, stabilization is achieved without the use of a plurality of accelerometers and the wiring, control of computers and associated service systems that have been proposed to articulate the wing profiles by means of an electric, pneumatic or hydraulic actuator. With reference to Figures 1, 2 and 3, a suspended bridge comprises a platform 10 supported by a pair of catenaries not shown by two series of supports P17 5 / 98MX 11 and 12 of tension that are formed conveniently as rods or cables. The bridge platform can be of any convenient construction known in the art and typically comprises a box 13 of composite beams defining the road tracks 14, 15 separated by the raised cords 16, 17 and 18. Regardless of their cross section profile Specifically, the platform 10 has aerodynamic properties that when exposed to crosswinds, its stability is controlled by two series of wing profile stabilizers 19 and 20 positioned along each longitudinal edge of platform 10. Each stabilizer is connected to the platform 10 by a pivot 21 for articulation along an axis that is generally longitudinal to the platform, which allows the articulation of the stabilizer 19, 20 towards a position that will generate a force, in the presence of a transverse wind, to reduce all the aerodynamic lifting of the associated portion of the platform 10. The lower ends of the supports 11, 12 of tension are firmly connected to the ends of levers 22, which are also secured to platform 10 by their respective pivots 23, which allows angular movement between each tension support 11 or 12 and platform 10 along the axes of the pivots 23, P17 5 / 98MX which are generally parallel to the axis 21 of the associated stabilizer. As can best be seen in Figure 4, a link 24 is connected by a pivot 25 to the stabilizer 19, at a point separate from the pivot 21, and also by a pivot 26 to the lever 22 at a point spaced apart from the pivot 23, pivots 21, 23 25 and 26 are parallel. In this way, any angular movement between the platform 10 and the tension support 11 will cause an angular movement relative to the lever 22 on its pivot 23, which causes the link 24 to transmit this movement to the stabilizer 19, which will rotate therein. direction on its pivot 21. It should be noted that the effective arm of the lever between the pivots 23 and 26 is larger than that between the pivots 21 and 25, where the relative angular movement of the lever 22 causes an amplified movement of the stabilizer 19. It should also be noted that the lever 22 and the link 24, together with their associated pivots 21, 23 and 26 form a mechanism operable by the angular movement between the platform 10 and the adjacent tension support 11. In this way any torsional movement of the platform 10 of the bridge in relation to any of the tension supports 11 or 12, will cause the articulation of the adjacent stabilizer 19 or 20, which modifies the P17 5 / 98MX aerodynamic properties of the platform 10. In this way, in Figure 2, the left rotation of a portion of the platform 10, simultaneously causes the left stabilizer 19 to rise while the right stabilizer 20 descends. In this way, the stabilizers 19 and 20 will execute a restoration coupling for the platform 10 regardless of whether the wind blows on the right or left side. In Figure 3, the platform 10 has been turned to the right and it should be noted that the movement of the stabilizers 19 and 20 is reversed in a similar manner so that they again execute a restoration coupling on the platform 10. It should be noted in In particular, the bending of the stabilizers 19 and 20 will always increase the stability of the platform 10, regardless of the direction in which the wind blows. The ratio of the distances between the pivots 23 and 26 and the pivots 21 and 25 will depend on the dynamics of the platform 10 and its suspension 11, 12 can be determined by the wind tunnel tests and / or theoretical calculations. The proportion will depend, for some bridges, on the opening position of the arc of the stabilizer 19 or 20 in particular. In Figure 5, most of the components are P17 5 / 98MX equivalent to those of Figure 4 and are identified with the same reference numbers since they fulfill the same function. The only modification is that the outer end of the stabilizer 19 is provided with a control surface 126 with independent adjustment, which is connected to the stabilizer 19 by a pivot 27 which is parallel to the axis of the pivot 21. The control surface 126 can be articulated, on its pivot 27, relative to the stabilizer 19, by a power actuator 28 which is enclosed within the stabilizer 19, as shown, and drives the control surface 126 through the link 29. The power actuator can be operated mechanically in order to adjust the control surface 126 in a position to provide the stabilizer 19 with a desired feature for the portion of the platform to which it is connected, or it may be operated electrically, pneumatically or hydraulically where the Stabilizer characteristics 19 can be adjusted continuously. The benefit of a mechanically linked stabilizer arrangement, such as that described with reference to Figures 1 through 4, is the absence of large power actuators that will obviously need a continuous and available source of power, even with the rigor of a hurricane, forces of the winds and the absence of P17 5 / 98MX computers and accelerometers. However, an active control approach, in common with comparable aviation systems, is extremely flexible as changes in the control system can be accommodated relatively easily, and the necessary functional complexity can be provided. The attractiveness of the combined implementation shown in Figure 5 is that the best features of both approaches can be included. In this way, the benefit of the large, mechanically driven stabilizers 19, 20 can be achieved and their function can be increased by small surfaces 126 actively controlled in a manner similar to an adjustment projection on an aviation elevator. In this way, the stabilization volume can be executed by large stabilizers 19, 20 operated mechanically, while the small surfaces 126 actively controlled will have a precise performance while they are not demanding in terms of size, cost, requirement of power and integrity, when compared to an independent active control system. Figure 6 shows a construction which is, in general, the same as that described with reference to Figures 1 to 4, and in accordance therewith the same reference numerals have been used to denote the P1745 / 98MX equivalent components. The difference is that the masses of the stabilizers 19, 20 are balanced by interconnecting the links 30 having their outer ends connected to the extensions 31 of the stabilizer mounted by their respective pivots 32, whose axes are parallel with the pivots 21 and 23. Internal ends of the links are joined by a common pivot 33 to a link 34, which is allowed to rotate on a pivot 35 carried by the platform 10 of the bridge. In this way, the masses of the pair of stabilizers 19 and 20 aligned transversely, are balanced independently of their articulation. Er. Figure 7, platform 10 of the bridge is of a somewhat different construction and is that the levers 22 are mounted on the pivots 23 placed within the external longitudinal axes of the platform 10, which defines the roads of roads 36 and 37 The wing profile stabilizers 19 and 20 have been moved so that they are connected to allow articulation on the longitudinally extending pivots 38 in the platform 10 and are carried by their respective levers 22. The stabilizers 19 and 20 are hinged by respective links 39, which are mounted by pivots, as shown, between the platform 10 and the stabilizers 19 and 20. It should be noted that the links 39 cross with the P17 5 / 98MX levers 22 to ensure that the angular movement between the platform 10 and the adjacent tension supports 11 and 12 causes the stabilizers 19 and 20 to articulate in the proper direction. With this arrangement, it can be seen that rather than modifying the aerodynamic properties of the platform 10, the stabilizers 19 and 20 execute compensating forces for the platform 10 through their respective levers 22. If desired, the stabilizers 19 and 20 can be mounted directly on the tension supports 11 and 12. In the case in which the tension supports are formed by suspension rods, the rods themselves will be connected to an appropriate journal that will receive the pivots 23, so that the tension support bar 11 or 12 will replace the upper arm of lever 22, the journal is designed to provide mounting for pivot 26. The mechanisms shown by Figures 4 and 7 can be replaced by another convenient mechanism or gear that will actuate stabilizers 19 and 20 as required. If desired, the bridge platform 10 can be adjusted with the stabilizers 19 and 20 of both Figures 4 and 7. In addition to providing a bridge structure P17 5 / 98MX having a novel form of stabilization, it should be noted that the arrangements shown here can be used to modify existing bridges that have a platform supported by tension supports, and this can be achieved without the need to completely dismantle the bridge P1745 / 98MX

Claims (10)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. A bridge comprising a platform supported by tension supports and profile stabilizers. of wings mounted by pivots on their respective axes, generally longitudinal to the platform, for articulation to a position to improve the stability of the platform; characterized in that each stabilizer is mechanically connected to the platform, and an adjacent tension support through a mechanism, is operable by the angular movement between the platform and the tension supports on a longitudinal axis of the bridge, in such a way that, when there is an angular movement between a portion of the platform and the adjacent tension support, the associated stabilizer will be articulated by that movement through the mechanism to a position that will generate a force in the portion of the platform, in the presence of a transversal wind. A bridge, according to Claim 1, characterized in that each mechanism includes a lever, which is secured to the associated tension support and is pivoted to the platform on an axis, which is P17 5 / 98MX generally parallel to the pivot axis of the associated stabilizer. 3. A bridge, according to Claim 1, characterized in that each mechanism is arranged to amplify the articulation of its associated stabilizer with respect to angular movement. A bridge, according to Claim 2, characterized in that at least some of the stabilizers are mounted by pivots on their respective axes, directly on the platform, and are arranged to be articulated by their respective links, which are assembled by pivots to their respective levers. A bridge, according to Claim 1, characterized in that at least some of the stabilizers are mounted by pivots on their respective axes, directly on the platform and are positioned to modify the aerodynamic properties of the platform. A bridge, according to Claim 1, characterized in that at least some of the stabilizers are mounted by pivots to their respective axes from the tension supports. 7. A bridge, according to Claim 2, characterized in that at least some of the P17 5 / 98MX outriggers are mounted by pivots on their respective shafts from their respective levers. A bridge, according to Claim 7, characterized in that each stabilizer is arranged to be articulated by a link mounted by pivots on the platform. A bridge, according to Claim 1, characterized in that at least one of the stabilizers is provided with a control surface with independent adjustment. A bridge, according to Claim 1, characterized in that a pair of outriggers are mounted on opposite sides of the platform and are balanced by an interconnecting link. A bridge, according to Claim 10, characterized in that the interconnection link is operatively arranged between the mechanisms of the stabilizer pair. 12. A method for stabilizing a bridge having a platform 10 supported by tension supports, and having wing profile stabilizers mounted on their respective axes, generally longitudinal to the platform, characterized by mechanically connecting the platform to a support of adjacent tension when using a mechanism operable by angular movement between the P17 5 / 98MX platform and the tension supports on a longitudinal axis of the bridge, in order to articulate the stabilizers for the movement through the mechanism towards a position that will generate a force, in the presence of a transversal wind, to reduce the lifting aerodynamic total of platform 10. P1745 / 98MX