Seismic isolation assembly

Abstract

A seismic isolation assembly is defined by a first support plate and a second support plate disposed in parallel relation with a spacing being provided between the support plates. The first support plate is connected to ground and the second support plate is attached to a structure to be isolated. A set of wire rope isolators are disposed between the first and second support plates as well as at least one linear damper that is angularly disposed and mounted between the first and second support plates.

Claims

1. A seismic isolation assembly comprising: a first support plate having a top surface and a bottom surface, the first support plate configured for fixed attachment to a base; a second support plate having a top surface and a bottom surface, the second support plate being disposed in parallel relation above the first support plate and configured for fixed attachment to a structure and in which a spacing is defined adjacent to the top surface of the first support plate and the bottom surface of the second support plate; a plurality of wire rope isolators fixedly mounted in spaced relation between the first support plate and the second support plate, each wire rope isolator comprising a pair of mounting blocks, each of the pair of mounting blocks having a plurality of holes and a plurality of cylindrical wire coils threaded through the plurality of holes, the cylindrical wire coils extending along an axis that is parallel to the first and second support plates; and a plurality of linear dampers, each of the linear dampers being angularly mounted between the first support plate and the second support plate, wherein one end of each of the plurality of linear dampers is mounted to the top surface of the first support plate and an opposite end is mounted to the top surface of the second support plate.

2. A seismic isolation assembly as recited in claim 1, wherein the plurality of linear dampers are mounted in spaced relation between adjacent wire rope isolators.

3. A seismic isolation assembly as recited in claim 2, wherein sets of wire rope isolators are disposed in spaced relation between the first and second support plates and in which at least two linear dampers are disposed in parallel relation between adjacent wire rope isolators.

4. A seismic isolation assembly as recited in claim 1, wherein the plurality of linear dampers are mounted at an angle between about 45 and about 90 degrees relative to the second support plate.

5. A seismic isolation assembly as recited in claim 1, wherein the plurality of linear dampers are hydraulic viscous dampers.

6. A seismic isolation assembly as recited in claim 1, wherein the first and second support plates are disposed in a horizontal orientation.

7. A seismic isolation assembly as recited in claim 3, wherein the plurality of linear dampers are independently mounted.

8. A seismic isolation assembly as recited in claim 3, in which the plurality of linear dampers includes at least three (3) side by side linear dampers disposed at the angle relative to the first support plate and the second support plate.

9. A method for isolating a ground supported structure from seismic loads, said method comprising: providing a first support plate having a top surface and a bottom surface, the first support plate being attached to ground; providing a second support plate having a top surface and a bottom surface, the second support plate being in parallel relation to the first support plate, the second support plate being attached to the ground supported structure and in which a spacing is defined adjacent to the top surface of the first support plate and the bottom surface of the second support plate, each of the first support plate and the second support plate being disposed in a horizontal configuration; mounting a plurality of wire rope isolators in the spacing between the first and second support plates, each of the wire rope isolators comprising a pair of mounting blocks, each of the pair of mounting blocks having a plurality of holes and a plurality of cylindrical wire coils threaded through the plurality of holes, the cylindrical wire coils extending along a defined horizontal axis that is parallel to the first and second support plates; and mounting a plurality of dampers to each of the first and second support plates, wherein one end of each of the plurality of dampers is mounted to the top surface of the first support plate and an opposite end is mounted to the top surface of the second support plate, the plurality of dampers being mounted at an angle relative to the first support plate and the second support plate.

10. A method as recited in claim 9, wherein the mounting angle of the plurality of dampers is between about 45 and 90 degrees relative to the horizontally disposed first support plate and the second support plate.

11. A method as recited in claim 9, in which the plurality of dampers comprise linear dampers having a fixed end attached to the first support plate and an axially movable end attached to the second support plate.

12. A method as recited in claim 11, wherein the plurality of linear dampers are hydraulic viscous dampers.

13. A method as recited in claim 9, in which at least one damper is disposed between adjacently mounted wire rope isolators.

14. A method as recited in claim 11, in which at least one damper of the plurality of dampers is disposed between adjacent wire rope isolators.

15. A method as recited in claim 14, in which four wire rope isolators are disposed in spaced relation between the first and second support plates and in which the at least one damper is angularly disposed and in side by side in parallel relation between adjacent wire rope isolators.

16. A method as recited in claim 14, in which each damper of the plurality of dampers is independently mounted.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of an exemplary ground supported structure;

(2) FIG. 2 is top perspective view of a seismic isolation assembly in accordance with an exemplary embodiment;

(3) FIG. 3 is a side elevational view of the seismic isolation assembly of FIG. 2;

(4) FIGS. 4(a) and 4(b) are top plan and side views of an exemplary wire rope isolator for use in the seismic isolation assembly of FIGS. 2 and 3;

(5) FIGS. 5(a) and 5(b) are side views of an exemplary linear damper for use in the seismic isolation assembly of FIGS. 2-4; and

(6) FIG. 6 is a partial view of the ground supported structure of FIG. 1, as supported by the seismic isolation assembly of FIGS. 2-5.

DETAILED DESCRIPTION

(7) The following relates to an exemplary embodiment of an assembly that is utilized to isolate seismic load inputs and in particular those inputs relative to an eccentric ground supported structure, such as the circuit breaker 10 depicted in FIG. 1. It will be readily apparent to those of sufficient skill from the following description, however, that this assembly and variants thereof can easily be employed for effectively isolating other ground supported structures. In addition and in the course of discussion, certain terms such as horizontal”, “vertical”, “upper”, “lower”, “top”, “bottom”, “above”, “below” and the like are used in order to provide a suitable frame of reference with regard to the accompanying drawings. These terms, however, are not intended to limit the scope of the inventive concepts, including the appended claims, unless such limitations are specifically indicated.

(8) In addition, the drawings being intended to depict salient features are not necessarily to scale. As a result, the drawings should not be relied upon for scaling purposes.

(9) Referring to FIGS. 2 and 3, an exemplary seismic isolation assembly 100 includes a first or lower support plate 104 and a second or upper support plate 110. Each of the lower and upper support plates 104, 110 are made from a suitable structural material, such as stainless steel, and disposed in substantially parallel relation with one another. The perspective view of FIG. 2 shows that the lower support plate 104 is attached, such through the use of bolts (not shown) secured through openings 105 extending through the thickness of the lower support plate 104 to a support structure on the ground. As more clearly seen in FIG. 3, a spacing 117 is defined between an upper surface or side 109 of the lower support plate 104 and a lower surface or side 111 of the upper support plate 110, as discussed herein. According to this embodiment, the lower support plate 104 is substantially rectangular in terms of configuration, with each corner 107 of the lower support plate 104 being beveled. The upper support plate 110 is smaller in terms of its overall length and width dimensions than that of the lower support plate 104. For purposes of this exemplary embodiment, the upper support plate 110 is further defined by a substantially octagonal shape defined by respective sides 115. It should be noted, however, that the herein described configuration is exemplary and other suitable polygonal shapes, including circular configurations, could be alternatively provided for either or both of the lower and upper support plates 104, 110, provided each are substantially planar. When assembled, the upper support plate 110 is substantially centered above the lower support plate 104, the support plates being disposed in a substantially horizontal configuration. A top or upper side 112 of the upper support plate 110 includes at least one set of openings 119 that are spaced and configured for fixedly and securely retaining an end of the structure to be isolated.

(10) Still referring to FIGS. 2 and 3, a plurality of wire rope isolators 118 are disposed within the defined spacing 117 between the lower and upper support plates 104, 110. According to this embodiment, each wire rope isolator 118 is individually secured to the lower surface 111 of the upper support plate 110 and to the upper surface of a support block or platform 127, the latter being bolted or otherwise fixedly mounted to the upper surface 109 of the lower support plate 104. The support block 127 is exemplary and other mounting techniques to the lower support surface 104 or the base 113 can be utilized. According to this exemplary embodiment, a total of four (4) wire rope isolators 118 are disposed in equally spaced relation to one another between the lower and upper support plates 104, 110, although this parameter can also be easily varied depending on loading conditions and the structure to be isolated.

(11) More specifically and referring to FIGS. 4(a) and 4(b), each wire rope isolator 118 according to this exemplary embodiment includes a rectangular shaped upper mounting block 130 and a parallel and correspondingly shaped lower mounting block 134, respectively. A plurality of cylindrical wire coils 140 are introduced between the mounting blocks 130, 134 through a spaced series of lateral holes 144 provided in each mounting block 130, 134, as the coils 140 are threaded therethrough and in which the ends of each coil 140 are attached to the upper mounting block 130. According to this embodiment, the mounting blocks 130, 134 are each formed from aluminum and the cylindrical wire coils 140 are formed from stainless steel, but these materials can be suitably varied. In addition, the size of the mounting blocks 130, 134 and the lateral holes 144 of the isolators 118, as well as the thickness of the cylindrical wire in the coils 140 used can also be suitably varied, depending on the structure being supported and required spring rate, deflection and damping characteristics of a particular application. For example, one suitable wire rope isolator design which can be used for this purpose is described in commonly owned U.S. Pat. No. 5,449,285 to Collins, the entire contents of which are herein incorporated by reference. It will be readily apparent from the following discussion that other suitable isolator assemblies can be alternatively used.

(12) Each of the mounting blocks 130, 134 of the wire rope isolators 118 further includes a set of equally spaced transverse through openings 152 that are provided in opposing top and bottom sides thereof to permit attachment to the bottom surface 111 of the upper support plate 110 and the top surface of the supporting block 127, respectively, using appropriately sized threaded fasteners.

(13) As shown in FIGS. 2 and 3, the herein described isolation assembly further includes an additional plurality of linear dampers 160 that are disposed between the lower support plate 104 and the upper support plate 110. These dampers 160 provide additional damping that cannot be provided by the wire rope isolators 118 due to loading conditions of the supported structure 10, FIG. 1.

(14) Referring to FIGS. 5(a) and 5(b), each of the linear dampers 160 according to this exemplary embodiment are defined by a cylindrical housing 168 having a fixed end 164 and an oppositely disposed axially movable end 166. The axially movable end 166 is further attached to a piston assembly 174 that includes a piston rod 176 extending within the interior of the cylindrical housing 168. The interior of the cylindrical housing 168 defines a damping chamber that is configured to retain a quantity of a hydraulic fluid and in which the piston assembly 174 is configured to displace fluid within the cylinder and induce damping. Each of the movable and fixed ends 164, 166 of the cylinder 168 include fittings that enable transverse mounting. The stroke of the piston assembly 174 can be selected based on the loading characteristics and structure to be supported and isolated. One example of a suitable hydraulic damper for these purposes is the LD damper series, manufactured by ITT Enidine, Inc., although other versions can be substituted. Alternatively, other forms of linear dampers such as linear friction dampers can also be substituted herein for the linear hydraulic dampers described herein.

(15) According to this exemplary embodiment, four (4) sets of linear dampers 160 are vertically disposed between the adjacently spaced wire rope isolators 118. Each of the four sets of linear dampers 160 include a plurality of hydraulic viscous dampers in which each fixed end 164 is independently secured to the lower support plate 104 and the movable end 166 is secured to an upwardly extending portion of a mounting block 190, the latter being fixedly attached to the top surface 112 of the upper support plate 110 and secured thereto using bolts or other suitable fasteners (not shown). Each of the linear dampers 160 according to this particular embodiment are vertically disposed at an angle of approximately 68 degrees relative to the upper support plate 110. According to this exemplary embodiment, each set of linear dampers 160 is defined by four (4) hydraulic dampers, which are disposed in side by side parallel relation to one another and independently mounted to the lower support plate 104 and mounting block 190. The number of sets of linear dampers 160 and the number of dampers in each set can be varied, as well as the vertical angle at which the linear dampers 160 are disposed. As a result and due to their ease in accessibility and independent mounting, the number of dampers 160 can be changed “on the fly” for purposes of testing and support/damping in actual use and in which the support block 127 and mounting plate can include a plurality of spaced attachment positions.

(16) As previously noted, the stroke length of each linear damper 160 can be suitably selected based on the loading characteristics, as well as the type of hydraulic fluid retained in the housing 168 and the damping coefficient.

(17) As shown in the figures, particularly FIG. 6 and in terms of overall operation, the circuit breaker of FIG. 1 is again shown having a supporting vertical bracket 15 disposed at the lower or bottom end of the structure 10 that is fixedly mounted to the upper side 112 of the upper support plate 110 while the lower support plate 104 is attached to ground. This supported structure 10 is isolated from seismic inputs from the ground, which is a multi-directional input. Based on the high and/or eccentric center of gravity of the supported structure a rocking component is created, which is non-axial. For purposes of tensile and compressive damping of the supported structure, the wire rope isolators 118 providing a low spring rate and some hysteretic damping in all directions. The linear dampers 160, being angularly mounted relative to the primary axis of the supported structure 10 are configured to provide additional damping to the system in all directions. That is, angular mounting of a plurality of linear dampers 160 at the spaced locations enables additional damping as caused by seismic loads in all directions. The hydraulic damping is required because the wire rope isolators 118 fail to provide sufficient damping in all directions.

PARTS LIST FOR FIGS. 1-6

(18) 10 structure, circuit breaker 14 vertical mast 15 supporting vertical bracket 18 horizontal or cross member 22 disc-like insulator plates 100 seismic isolation assembly 104 lower support plate 105 openings 107 corners, lower support plate 109 upper or top side, lower support plate 110 upper support plate 111 lower or bottom side, upper support plate 112 upper or top side, upper support plate 115 sides, upper support plate 117 spacing 118 wire rope isolators 119 openings 127 support block 130 mounting block (upper) 134 mounting block (lower) 140 cylindrical wire coils 144 openings, lateral 152 openings, transverse 160 linear dampers 164 fixed end, viscous damper 166 movable end, viscous damper 168 housing 174 piston assembly 176 piston rod 190 mounting block

(19) It will be readily apparent that other variations and modifications are possible utilizing the inventive concepts that have been described herein and further in accordance with the following appended claims.