WO2010000897A1

WO2010000897A1 - Method for the seismic isolation of a supported object

Info

Publication number: WO2010000897A1
Application number: PCT/ES2009/000351
Authority: WO
Inventors: José RODELLAR BENEDE; Mohammed Ismail; Fayçal IKHOUANE
Original assignee: Universitat Politécnica de Catalunya
Priority date: 2008-07-03
Filing date: 2009-07-01
Publication date: 2010-01-07

Abstract

The invention comprises: an upper plate (2), one face of which is secured to the object to be isolated; a lower plate (3) one face of which is secured to a base; and a rolling body (1) disposed between the two plates (2, 3) so as to support the object, said rolling body (1) being in rolling contact with the opposing inner faces of the two plates (2, 3) and capable of rolling upon the occurrence of a relative lateral movement between the plates in response to dynamic excitation. The inner face of the aforementioned plates (2, 3) includes at least one convex domed portion (2-4) that is in contact with a convex surface (1-3) of the rolling body (1) for every possible position thereof during rolling, such that the distance between the two plates (2, 3) is substantially equal over the entire rolling trajectory of the rolling body (1) therebetween.

Description

SEISMIC ISOLATION SYSTEM OF A SUPPORTED OBJECT

Technical sector

The present invention concerns a seismic isolation system intended to mitigate or reduce the potential damage of structural or non-structural systems due to dynamic impacts, especially seismic impacts.

According to the terminology of this invention the structural systems to which this invention is applicable will cover buildings, bridges, water tanks, etc., while the non-structural systems can be any equipment and / or antiques (objects or monuments) susceptible of being damaged in their integrity or that they are sensitive to movement. The "supported object" referred to in this invention encompasses both structural and non-structural systems.

State of the prior art Although the first patents related to seismic isolation date from the century

XIX and some prototypes of the early twentieth century are known, it was from the 70s when seismic isolation systems were booming within structural engineering. Since bridges are a more natural candidate for insulation than buildings, being normally constructed with supports that separate the superstructure from the substructure, seismic insulation was used in bridges since the early 1970s, while in buildings used only in the late 70s.

The first applications for bridges added energy dissipation to the flexibility already existing in the superstructure. The rubber support with lead or LRB (lead rubber bearing), was invented in the 70s and allowed to include in a single unit flexibility and damping. During those same dates, the first insulation applications were constructed using rubber supports. However, these systems had the disadvantage of poor inherent damping and of not being rigid enough to withstand service loads such as wind. At the beginning of the 80s, the development in rubber technology made it possible to obtain new rubber compounds called high damping rubber or HDR (high damping rubber). With these compounds, supports were obtained with high stiffness against reduced shear strain stresses, but low stiffness against higher deformation levels. On discharge, these supports formed a hysteresis cycle with a significant amount of damping. Although the first applications in bridges and buildings In U.S.A. at the beginning of the 80s they used LRB or HDR supports, these two isolation systems still lacked maximum displacement limiters, effective re-centering mechanisms (return of the support to the initial position after the dynamic impact), as well as aptitudes for structures Low mass In addition, there was a reduction in the support area when they moved laterally, which imposed restrictions on the ratios or proportions of height / width and deformation / height.

In some projects sliding supports were used in parallel with LRB and

HDR to support light components such as stairs. The sliding supports were not used alone as insulation systems because, although they offered high levels of damping, they did not include either re-centering mechanisms, or maximum displacement limitation means. Because of this, a structure supported by this type of sliding support would probably end up in a different position after an earthquake and continue to move in case of aftershocks.

The development of the pendular systems by friction or FPS (friction pendulum system), formed the sliding supports by means of a spherical surface, overcoming the greater Disadvantage of the previous sliding supports. The lateral movement of the FPS system produces a vertical lifting of the supports that provides a gravitational recovery force but, unfortunately, to the detriment of the structural lifting. In addition, the high cost of articulated landslides (in SPF) makes it difficult to use in light buildings because they are not profitable. Another drawback of this system is the increase in the coefficient of sliding friction by increasing the sliding speed.

The patent application US-20060174555-A1 is known which describes a sliding pendular seismic isolation system with a support configuration formed by multiple sliding plates along different concave or concave cylindrical spherical surfaces, each of said plates constituting an independent sliding pendulum mechanism, with a predetermined oscillation and friction length. In this patent application, the insulation system is arranged to achieve an increase in effective friction by increasing the amplitudes of lateral displacements by using different cooperating configurations and proposing to combine one or more of said configurations. The aforementioned patent application shows in its figures that the proposed insulation system comprises in its upper and lower plates configurations capable of interfering as a stop with some of the sliding plates in their lateral displacement. Most insulation systems work best with heavy masses. An effective isolation achieves a long response period, which is proportional to the square root of the mass, and inversely proportional to the square root of the stiffness. Therefore, to achieve a given period of isolation, low masses must be associated with low stiffness. The assemblies that are used for seismic isolation do not have an infinite range of stiffness. For example, elastomeric supports need to have a minimum diameter to ensure their stability under seismic displacements. This minimum size establishes a minimum stiffness.

Sliding systems do not have this limitation and, therefore, may be appropriate for low weight buildings. However, even these systems tend not to be profitable for light buildings for different reasons. Despite the weight of the building, the displacement is the same for a given effective period and, therefore, the size of the plates, which are the most expensive part of the sliding support system, is the same for light or heavy structures. This means that, in proportion, the cost of sliding systems for light buildings is higher.

Although several systems have been proposed to insulate light buildings, there are few cases in which they have been shown to be really effective.

In summary, to achieve effective insulation, the insulation system must meet the following conditions: vertical stiffness, horizontal flexibility, wind resistance and include the following mechanisms: re-centering mechanisms, damping mechanisms and maximum displacement limiters. Although the insulation systems market is currently distributed mainly between variations of LRB, HDR, flat sliding supports and FPS, the proposed systems still do not meet some conditions to ensure an ideal insulation. For example, elastomeric supports cannot provide a range of horizontal flexibility suitable for light mass structures. In addition, they deform laterally undergoing a reduction in the support area, lack of built-in maximum displacement limiters and need efficient re-centering mechanisms to prevent structural torsion. On the other hand, FPS systems cannot provide greater horizontal flexibility with lower cost, so they are not economically suitable for light structures. In addition, they cause lifting of the structures, which is not recommended. Likewise, there is a need to overcome the increase in resistance to movement with the increase in friction speed. Patent application WO-A2-2005031088 concerns a seismic isolation system comprising a cylinder arranged in rolling contact between a upper plate and a lower plate. The upper plate is fixed to a superstructure while the lower plate is fixed to a base. One or both support surfaces are inclined to form a central depression in which the cylinder resides under a normal weight of the superstructure, and towards which the cylinder tends to position itself when a relative displacement occurs between the upper and lower plates, providing a constant restorative force. This configuration therefore constitutes a re-centering mechanism of the insulation system. In the seismic isolation system described in said patent application, the cylinder comprises grooves adapted to fit in the upper and lower plates after a lateral displacement, preventing displacement in a direction along the longitudinal axis of the cylinder, but allowing it to roll freely between the two support plates.

It is also known the patent US-A-5862638 which describes a seismic isolation system formed by a central support that absorbs the forces caused by the horizontal sliding movement, located between an upper plate and a lower plate. This system comprises dampers connected between the upper and lower plate with sufficient extension to allow lateral displacement of the central support between both plates.

The present invention proposes a practical, economical and efficient seismic isolation system that overcomes many of the drawbacks of the aforementioned insulation systems, while maintaining its main advantages. The aforementioned insulation system is designed primarily to safeguard a variety of structural and non-structural systems from seismic threat.

Explanation of the invention

The present invention concerns a seismic isolation system to protect a supported object from dynamic excitations. The aforementioned system includes:

- an upper plate of rigid material, adapted to be fixed by a face facing upwards to said object in order to provide a support plane;

- a bottom plate of rigid material, adapted to be fixed by a face facing down to a base; Y

- a rolling or insulating body, disposed between the two plates, supporting said object, the rolling body being in rolling contact with internal faces of both plates opposite each other, or of laminar elements that cover at least part thereof. , and defining a housing between both plates, which allows roll to the rolling body when there is a relative lateral displacement between both plates.

At least one of the two aforementioned plates comprises, on its inner face, a domed portion with a curvature determined according to the curvature of the face of the rolling body, with which it establishes contact for each of the possible positions to be adopted when rolling , so that the distance between the two plates is substantially equal during the entire rolling path between them of said rolling body. In a preferred embodiment of the present invention, each of the plates comprises on its internal face, in a substantially central area thereof, a respective bulged portion.

Likewise, the rolling body comprises peripheral retention configurations adapted to engage and / or fit into respective limit stop configurations defined at edges of the internal faces of the plates, upon reaching said rolling body, a predetermined maximum lateral displacement. This avoids the lifting of the supported object, said edges defining the limits of the plates for said rolling path of the rolling body.

For a preferred embodiment of the present invention the rolling body is circular and said bulging or bulging are revolution bulges. For another embodiment of the present invention said rolling body is an elliptical solid, while for another embodiment it is a cylinder.

The system object of the present invention further comprises ipos mechanical damping or dissipating elements that connect said upper and lower plates by their internal faces in an area close to their peripheral edges. Said damping elements, for an exemplary embodiment, have a triple curvature configuration, the central curve being arranged towards the outside of the system. In another embodiment of the present invention, said damping elements comprise a hollow cylinder of an elastomeric material, said cylinder having a determined thickness depending on the weight of the object to be supported. To obtain a better damping efficiency, the hollow cylinder comprises in its interior a lead bar of a length substantially similar to that of the hollow cylinder, extending in a direction parallel to the longitudinal axis thereof. This lead bar confers greater resistance to the system, as well as greater flexibility by deforming plastically to shear stresses.

On the other hand and according to the aforementioned, the rolling body is in rolling contact with the inner face of both plates or of laminar elements, which are of a more flexible material than those of said plates, thus causing a damping effect. Each of these laminar cover elements extends over most of the internal face of a respective plate, covering at least the aforementioned limit stop configurations.

The system further comprises rigid elements attached to said upper face of said upper plate and / or said lower face of said lower plate, at least above and / or below, respectively, of said end areas of the edges of the inner faces of said plates to improve the dynamic performance of the damping elements.

Brief description of the drawings

The foregoing and other advantages and features will be more fully understood from the following detailed description of some embodiments with reference to the attached drawings, which should be taken by way of illustration and not limitation. Figure 1 is an elevation view of a first implementation of the system of this invention showing a multidirectional seismic isolation support, with a rolling or insulating body formed by a solid of revolution suitable for light to moderate masses.

Figure 2 shows the exemplary embodiment of the previous Figure, exploded. Figures 3a and 3b illustrate the behavior of the system illustrated in Figure

1, in front of dynamic excitations, showing a central neutral position and positions of maximum horizontal displacement to the left and right. Figure 3a corresponds to a multidirectional seismic isolation support for heavy mass systems while Figure 3b corresponds to a solution for light to moderate mass systems, differentiated by the damping systems used in each case.

Figures 4a-4c schematically illustrate (insulator or rolling body and forces applied to the left and inter-plate insulator to the right) the behavior of the proposed insulation system that involves an inherent re-centering given the contact between the rolling body and the bulging configurations of the internal faces of the support plates.

Figures 5a-5b and 6a-6b show details related to the dampers and the union thereof to the upper and lower plates of the set for seismic isolation. Figures 7a, 7b and 7c show different configurations of the solid of revolution as well as the location of the laminar coating in a less rigid material between the inner faces of the plate and the rolling body.

Figure 8 shows an exemplary embodiment similar to that of Figure 1 with an insulator formed by a solid of revolution and damping and reinforcement systems suitable for heavy mass systems.

Figure 9 is equivalent to the previous one showing only an alternative damping mechanism.

Figure 10 shows an exemplary embodiment of a unidirectional seismic isolation support for light to moderate mass systems, where the rolling or insulating body has been produced by extrusion.

Figures 11 a, 11 b and 11c show various possible shapes for the cylindrical rolling body of the example of Fig. 10.

The same numerical references have been used for those elements with identical functionality that appear in the various illustrated embodiments.

Detailed description of some embodiments

Example 1 (light to moderate mass systems) Figures 1 and 2 show a concrete embodiment of the proposed insulation system. It is composed of a rolling or insulating body consisting of a solid of revolution (1) located between the two upper (2) and lower (3) plates. The contact between the plates (2, 3) and the solid (1) is made by means of laminar elements (4, 5) of a less rigid material perfectly attached (eg by gluing) to the plates (2, 3) in Your inner faces. Looking at Figure 2, the bulges of the upper (2) and lower (3) plates and how they fit with the convex curvature of the revolution solid (1) are appreciated. Referring to the upper plate, it can be seen how it has a triple curvature (2-4) (central bulging and slightly concave valleys on the sides) that matches the rolling surfaces (1-2) and (1, 3) of The upper part of the solid of revolution (1) during its rolling. In this embodiment, the parts (1-2) are flat and the part (1-3) is spherical. With this, it is possible to maintain a horizontal line that the solid (1) never exceeds in its rolling between the positions of maximum horizontal displacements to the left and right, as illustrated in Figure 3. This manages to avoid elevations of the structure supported by the insulation system Figures 1 and 2 also show how the stops materialize to limit maximum displacements. In this case, it is achieved with the surfaces (2-1) and (2- 2) for the upper plate (2) and (3-1) and (3-2) for the lower plate (3), which in shape of step connect with the grooves or grooves (1-1) of the solid of revolution. The flat part (1-2) of the solid (1) serves to maintain a greater contact surface between the solid or insulator (1) and the structure supported in the extreme displacement positions (see Figure 3) and to reduce the speed of the rolling solid (1) before being braked by the aforementioned stop configurations (2-1), (2-2), (3-1 and (3-2).

The quasi-elliptical shape of the solid of revolution (1) guarantees an efficient re-centering mechanism, as illustrated in Figure 4, through the restorative moment M of the pair of vertical gravitational forces generated by rolling the solid (1) of the system of isolation. In other words, gravity recovers the initial position of the system in the absence of external excitations. This restorative mechanism prevents structural torsion and eliminates the effect P ^~ Δ_ In Figures 1, 2, 5a-5b and 6a-6b, the dampers (6) considered in this example are also appreciated. These are steel elements coupled to the plates (2) and (3) through the joints (9) along the perimeter. The number and section of these dampers are designed based on the resistance required for minor earthquakes and the desired level of damping. The curvature, arranged outwards, is chosen to ensure that the dampers can extend sufficiently within the maximum displacements expected for the supported structure, as illustrated in Figure 3, in which the dampers are appreciated in their maximum extent coinciding with the maximum displacements of the structure. This can be achieved by providing the dampers with an external triple curvature indicated by (6-1) in Figure 2, or a similar shape. In order to improve its efficiency, the dampers (6) are rigidly coupled to the plates (2) and (3) by the joints (9) as detailed in Figures 5 and 6. During the installation of the insulation system, this coupling is realizes that, initially, the solid of revolution (1) slightly touches the less rigid covers of the less rigid upper (4) and lower (5) parts. From this connection, the supported structure is gradually loaded onto the insulators so that the dampers (6) all acquire the same prestress below the creep limit. The remaining deformation until reaching said limit is sufficient to resist minor vibrations. Consequently, the dissipation of energy in the dampers (6) takes place by effect of the hysteresis in said dampers (6) quickly when a significant excitation occurs above the creep limit. To achieve better performance dynamic, the parts (2-1) and (3-1) are fixed to the upper plate (2) and the lower plate (3) respectively by means of vertical reinforcements (7) and (8) that can be seen in Figure 6 , in the plan view of one of the plates (2) of the system.

Figures 7a-7c present some variants in relation to the isolation system for illustrative but not limiting purposes. Figure 7a shows that the less rigid material of the laminar elements (4, 5) that cover the internal faces of the plates (2, 3) can have a flat surface, instead of a curve as in the case of Figures 1- 6. Figure 7a also illustrates that the upper and lower surfaces of the rolling body must not necessarily be smooth, and may have a regular roughness. Figure 7b illustrates that the laminar element (4, 5) of a less rigid material can alternatively cover the external surface of the rolling body (4,5) or possibly be on the inner faces of the plates (2, 3) and on that external surface of the rolling body.

Figure 7b also shows that the upper and lower plates (2,3) can include the reinforcements (7,8) forming a single body. Figure 7c shows a rolling body (1) of reduced height, with a configuration of the maximum displacement limit stops easier than in the case of Figures 1-6. In this case, a single stop (1-1) is provided that fits on the surfaces (2-2) and (5-2).

Example 2 (large mass systems)

The present invention can be specifically adapted to support large mass systems. For this, the main support system of Figure 1, which is constituted by the contact between the rolling or insulating body (1) and the upper and lower plates (2,3), is modified in the manner shown in Figure 8 In this case, a hollow cylinder made of reinforced elastomer (11) is used as the main support. In this scheme, the contact between the insulator and the plates serves as a secondary support element. The hollow cylinder, which surrounds the rolling body (1), has a variable thickness to provide sufficient support area based on the weight of the supported structure. The reinforcements (7) and (8) as well as the support plates (2) and (3) are modified to a certain extent, as illustrated in Figure 8, to correctly fix the upper and lower surfaces of the hollow cylinder (11 ) to the plates (2) and (3) and then be correctly fixed to the structure and base respectively.

In this example of application, the energy dissipation is achieved by inserting lead rods (6), as seen in Figure 8, axially within the hollow cylinder, thus forming a main support surrounding the insulator ( 1), leaving the contact between the insulator and the plates (2,3,4,5) as a secondary support system. The number of lead bars and their diameter are properly chosen to achieve maximum dynamic performance of the isolated system.

The present invention is then superior to elastomeric supports and

Known LRBs since the hollow elastomeric support area can be reduced without restrictions to provide greater horizontal flexibility in the necessary value without fear of probable buckling failure, which is not the case in normal elastomeric supports.

In addition, the proposed insulator or rolling body (1) does not cause any structural elevation, as illustrated in Figure 3, when lateral movements occur. This provides a superior advantage over the FPS systems cited. In addition, FPS cannot provide low cost supports for light mass systems, while the present invention can provide a wide range of horizontal flexibility values with much lower cost.

Figure 9 is an exemplary embodiment where it is illustrated that the hollow cylinder (with or without lead rods) can be combined with a series of metal dampers (6) such as those considered in Example 1.

Example 3 (unidirectional embodiment)

The principles of the present invention can be adapted for vibration isolation in a single direction. In such a case, the rolling body (1) is designed in the form of a cylinder obtained by extrusion of a section along a perpendicular axis. Figure 10 shows an insulation system where the rolling body is a cylinder whose section has the same shape as the three-dimensional body considered in Example 1. The rest of the system elements are analogous to the case of Example 1 with the logical adaptations to Ia different geometry

Different sections can be considered to generate the cylinder by extrusion. Figure 11 shows some possibilities for illustrative but not limiting purposes.

Claims

1.- Seismic isolation system of a supported object to protect said object from dynamic excitations, the system comprising: - an upper plate adapted to be fixed by a face facing upwards to said object in order to provide a support plane;

- a lower plate adapted to be fixed by a face facing downwards to a base; Y

- a rolling body disposed between said two plates, supporting said object, said rolling body being in rolling contact with internal faces, facing each other, of both plates defining a housing for said rolling body with the possibility of rolling when a lateral displacement occurs relative between said plates; characterized in that at least one of said two plates comprises, on its inner face, at least one convex, bulged portion, with a curvature determined in function of the also convex, bulging curvature of the face of said rolling body, with which it contacts for each of the possible positions thereof when rolling, so that the distance between the two plates is substantially equal during the entire rolling path of the rolling body between them.

2 - Seismic isolation system according to claim 1, characterized in that said upper plate and said lower plate comprise, on their respective internal faces, at least said bulged portion.

3. Seismic isolation system according to claim 2, characterized in that said rolling body is of a quasi-elliptical configuration so that its rolling contact with said convex, domed internal faces, provides an inherent re-centering mechanism.

4. Seismic isolation system according to any one of the preceding claims characterized in that said rolling body comprises retention configurations adapted to engage in respective limit stop configurations defined at edges of said internal faces of said plates, upon reaching said rolling body, a predetermined maximum lateral displacement, thus avoiding the lifting of said object, said edges defining the limits of the plates for said rolling path of the rolling body.

5 - Seismic isolation system according to claim 4, characterized in that said retention configurations comprise at least one groove or groove surrounding said rolling body and said stop configurations Limiters comprise perpendicular fins extending from said edges into said housing.

6. Seismic isolation system according to claim 4, characterized in that some laminar elements are provided that cover at least part of said internal faces, facing each other, of said upper plate and lower plate, each of said laminar elements extending along the Ia most of the internal face of a respective plate, comprising at least said limit stop configurations.

7. Seismic isolation system according to any one of claims 1 to 5, characterized in that there are provided laminar elements that cover at least part of the external surface of said rolling body or body.

8. Seismic isolation system according to any one of claims 1 to 5, characterized in that there are provided laminar elements that cover at least part of the internal faces of the plates and / or of the external surface of said rolling body.

9. System, according to any one of claims 6-8, characterized in that said upper and lower plates are rigid material plates and because said laminar elements are of a more flexible material than the one of said upper and lower plate, causing a damping effect.

10. Seismic isolation system according to any one of claims 1 to 5, characterized in that said rolling body is a solid of revolution providing multidirectional insulation.

11 - Seismic isolation system according to any one of claims 1 to 5, characterized in that said rolling body is a body obtained by extrusion.

12. Seismic isolation system according to claim 11, characterized in that said rolling body is a cylinder providing unidirectional insulation.

13, - Seismic isolation system, according to any one of claims 1 to 5, characterized in that said rolling body is a body that has a regular surface roughness on at least the contact surface with said convex, bulged portion, which is at least one of the upper and lower plates.

14 - Seismic isolation system according to claim 4, characterized in that it comprises at least one damping element or energy dissipator mechanical that connects said upper and lower plates by their internal faces in an area close to said edges.

15. Seismic isolation system according to claim 14, characterized in that said damping element, which is at least one, has a curved configuration arranged towards the outside of said system.

16. Seismic isolation system according to claim 14, characterized in that said damping element, which is at least one, comprises a hollow cylinder of an elastomeric material, said cylinder having a determined thickness depending on the weight of the object to be supported.

17. Seismic isolation system according to claim 16, characterized in that said hollow cylinder comprises at least one lead rod inserted inside, said lead rod having a height substantially similar to that of the hollow cylinder and extending in a direction parallel to the longitudinal axis of said hollow cylinder.

18. Seismic isolation system according to claim 9, characterized in that it comprises at least one rigid element attached to said upper face of said upper plate and / or said lower face of said lower plate, at least above and / or <below, respectively, of said end zones of the edges of the inner faces of said plates to improve the dynamic performance of said damping elements.

19. Symmetric isolation system according to claims 1 or 2, characterized in that said bulging or bulging are in a substantially central area of said plates.