Patent ID: 12209431

DETAILED DESCRIPTION

The present invention relates to a seismic isolation system for a grid framework structure14forming an anti-seismic grid framework system. The basic principles of the seismic isolation system can be envisaged by the lateral mode of vibration of a non-isolated model shown inFIG.6aand isolated model shown inFIG.6b. Typically, the grid framework structure14is rigidly mounted to a solid concrete foundation in the ground200which can comprise various solid rock soil sediments. Seismic waves produced during earthquakes comprise a wide range of frequencies. While the energy of the waves with higher frequencies tends to be absorbed by solid rock soil, the waves with low frequencies (having periods larger than one second) pass the solid rock soil without being absorbed but are eventually amplified by soft sediments. Without any form of decoupling of the grid framework structure14from the ground200, the seismic waves and thus, seismic forces are transmitted through the solid concrete foundation resulting in structural damage or deformation to the grid framework structure, i.e. the floor shear force is large. The lateral forces generated by the seismic waves causes shaking of the grid framework structure which may cause the load bearing device operative on the grid to derail from the grid. Base isolation is an anti-seismic design strategy than can reduce the effect of earthquake ground motion by uncoupling the grid framework structure from its foundation. As shown to the right ofFIG.6b, the grid framework structure14is decoupled from the horizontal components of the ground motion by interposing structural elements with low horizontal stiffness between the foundation and the grid framework structure. As shown inFIG.6b, the grid framework structure14is mounted to a superstructure or diaphragm202, e.g. reinforced concrete slab, and the superstructure is raised above the ground by one or more base isolator devices204. This gives the grid framework structure a fundamental frequency that is much lower than both its fixed base frequency and the predominant frequencies of the ground motion. This shift of natural period causes a drop in spectral acceleration for the typical earthquake shaking and the resultant forces on the structural and non-structural elements of the grid framework structure which are significantly reduced. The relationship of the spectral acceleration on the period to complete one cycle of seismic wave is best illustrated by the schematic plot shown inFIG.7. As can be illustrated inFIG.7, as the period becomes longer and the damping is increased, the spectral acceleration is reduced. Thus, the seismic force, i.e. the floor shear force becomes small. For the purpose of the present invention, the ground is referred to as a substructure. There are various types of base isolation devices to decouple the grid framework structure from the ground motion as a result of earthquakes and thereby, preventing large deflections being transferred to the grid framework structure. These include but are not limited to elastomeric based bearings, sliding bears. The effect of the seismic isolation system on the grid framework structure is best explained by first discussing the components making up the grid framework structure. This will help understand the areas of the grid framework structure that a vulnerable to seismic forces.

Grid Framework Structure

FIG.8shows a perspective view of the grid framework structure114according to an embodiment of the present invention. The basic components of the grid framework structure114according to the present invention comprises a grid50lying in a horizontal plane mounted to a plurality of upright columns or upright members116. The term “upright member(s)” and “upright column(s)” are used interchangeably in the description to mean the same thing. As shown inFIG.8, the grid50comprises a series of horizontal intersecting beams or grid members118,120arranged to form a plurality of rectangular frames54, more specifically a first a set of grid members118extend in a first direction x and a second set of grid members120extend in a second direction y, the second set of grid members120running transversely to the first set of grid members118in a substantially horizontal plane. Each of the grid members extending in the first direction and/or second direction can be sub-divided or sectioned into discrete grid element that are joined or linked together. A connection plate or cap plate150as shown inFIG.9can be used to link or join the individual grid elements together in both the first direction and the second direction at the junction where the grid elements cross or intersect at each of the upright columns, i.e. the cap plate150is used to connect the grid elements together to the upright columns116. As a result, the upright columns are interconnected at their upper ends at the junction where the multiple grid elements cross in the grid structure by the cap plate150. As shown inFIG.9, the cap plate150is cross shaped having four connecting portions152for connecting to the ends or anywhere along the length of the grid elements at their intersections (seeFIGS.10and11). The cap plate150comprises a spigot or protrusion154that is sized to sit in a hollow central section70of the upright column116(at the second end of the upright column) in a tight fit for interconnecting the plurality of upright columns to the grid members as shown inFIG.12.FIG.13shows the joints at the intersections between adjacent grid elements at an upper end of the upright columns by the one or more cap plates. For the purpose of explanation, a lower end of the upright column mounted to the floor constitutes a first end of the upright column and the upper end of the upright column adjacent the grid50constitutes a second end of the upright column.

The first and the second set of grid members supports a first and a second set of tracks or rails57a.57brespectively for a load handling device to move one or more containers on the grid framework structure. For the purpose of explanation of the present invention, the intersections56constitute nodes of the grid structure. Each of the rectangular frames54constitute a grid cell and are sized for a remotely operated load handling device or bot travelling on the grid framework structure to retrieve and lower one or more containers stacked between the upright columns116. The grid50is raised above ground level by being mounted to the plurality of upright columns116at the intersections or nodes56where the grid members118,120cross so as to form a plurality of vertical storage locations58for containers to be stacked between the upright columns116and be guided by the upright columns116in a vertical direction through the plurality of substantially rectangular frames54. For the purpose of the present invention, a stack of containers can encompass a plurality of containers or one or more containers.

The grid framework structure114can be considered as a free standing (or self-supporting) rectilinear assemblage of upright columns116supporting the grid50formed from intersecting horizontal grid members118,120, i.e. a four wall shaped framework. Two or more of the upright columns are braced by at least one diagonal bracing member to provide one or more braced towers80within the grid framework structure114. The structural rigidity and moment resistance of the grid framework structure is largely provided by incorporating one or more truss assemblies or braced towers80at least partially around the periphery and/or within the body of the grid framework structure (seeFIG.8). The truss assembly may have a triangular or other non-trapezoidal shape. For example, the truss assembly can be any type of truss that provides structural rigidity to the grid framework structure against lateral forces including but are not limited to Warren Truss or a K Truss or a Fink Truss or a Pratt Truss or a Gambrel Truss or a Howe Truss. Bolts or other suitable attachment means may be used to secure the diagonal braces to the upright columns. The braced tower80as shown inFIG.14according to an embodiment of the present invention can be formed by rigidly joining a sub-set or sub-group of the plurality of upright columns116by one or more angled or diagonal braces or diagonal bracing members82. For the purpose of the present invention, the diagonal braces82cooperate with the upright columns116in a braced tower80to form one or more triangles. The sub-set of the plurality of upright columns that are braced together to form the braced tower80of the present invention can be two or more adjacent upright columns116lying in a same or in a single vertical plane and joined together by one or more diagonal braces82. Putting it another way, two or more adjacent upright columns116connected by one or more diagonal braces82lie in the same or single vertical plane, i.e. they are co-planar. In the particular embodiment of the present invention shown inFIG.14, each of the braced towers80comprise three upright columns in parallel relation and lie in a single vertical plane (co-planar) that are rigidly connected together by a plurality of diagonal braces82. Two of the three upright columns116a,116bare laterally disposed either side of a middle upright column116cand the two laterally disposed upright column116a,116bare rigidly connected to the middle upright column116cby a plurality of diagonal braces82. In the braced tower80of the present invention, one end of a diagonal bracing member82is connected to the middle upright column by a joining plate121. The joining plate121is inserted into a slot through the hollow centre section of the middle upright column116cin a direction perpendicular to the longitudinal direction of the upright column. By bracing one or more sub-groups of the upright columns116internally within the grid framework structure by one or more diagonal braces82, the structural rigidity of the grid framework structure is improved. For the purpose of the present invention, the term “vertical upright column”, “upright column” and “upright member” are used interchangeably through the description.

The grid framework structure is anchored to the ground, in this case superstructure, by one or more anchor bolts. In an embodiment of the present invention, one or more of upright columns at their lower end are mounted to the superstructure by an adjustable foot (seeFIG.15). The adjustable foot allows the height of the one or more of upright columns and thus, the grid framework structure as a whole, to be adjusted. This allows the level of the grid in the horizontal plane to be substantially flat for the load handling devices, which are largely remotely operated, to travel on the grid structure and thereby, prevent any of the tracks or rails being put under strain due to a variation in the height of one or more of the upright members116in the grid framework structure. The adjustable foot90as shown inFIG.15comprises a base plate92and a threaded spindle or rod94that is threadingly engagable with a separate push fit cap or plug96that sits in the lower end of the upright column as shown inFIG.10. As shown inFIG.8, one or more of the upright columns116are mounted to the floor or superstructure by the base plate92. The base plate92having one or more mounting holes for mounting the base plate92to the floor by one or more bolts.

In addition to mounting the upright columns making up the grid framework structure by the adjustable foot discussed above, one or more of the upright columns making up the braced towers80are anchored to the superstructure by one or more anchor feet132a,132b(seeFIG.14). In the particular embodiment shown inFIG.14, the outer upright columns116a,116bor the laterally disposed upright columns116a,116bare anchored to the concrete foundation by one or more anchor feet132and the middle upright column116cis supported on the adjustable foot90as discussed above. The lower end (first end) of the braced tower is anchored to the concrete foundation by one or more anchor bolts. Various types of anchor feet132a.132bto rigidly anchor the braced tower to the concrete foundation is applicable in the present invention. The anchor foot functions to bear the upright column load and the bracing load of the bracing assembly82of the braced tower80.

FIGS.14and16show two examples of the anchor foot that is used to anchor the braced tower to the concrete foundation according to the present invention. In comparison to the anchor foot shown inFIG.16, the anchor foot shown inFIG.14is more substantial in terms of size and weight in comparison to the anchor foot shown inFIG.16. The anchor foot132ashown inFIG.14is fabricated as a T-joint comprising a base plate133lying in a horizontal plane for anchoring to the floor by one or more anchor bolts and an anchor plate134perpendicular to the base plate133for attaching to the lower end of the upright column and the ends of the bracing member82. The anchor plate134is orientated such that the surface of the anchor plate134with the greatest surface area lies in the same vertical plane as the three upright columns116a,116b,116cof the braced tower80, e.g. the surface of the anchor plate134with the greatest surface area and the upright members116a,116b,116cof the braced tower80are co-planar. The problem with the anchor foot132ashown inFIG.14is the substantial weight and thus, cost to fabricate the anchor foot.

FIG.16shows an alternative anchor foot132bfor anchoring the braced tower80to the concrete foundation according to second embodiment of the present invention. Instead of a solid rectangular base plate133, the anchor foot is topology optimised that optimizes the materials layout within a given design space for a given set of loads. Two loads considered in the topology optimisation of the anchor foot are the loads from the upright columns116a,116b,116cand the bracing members82. Based on the constraints given by the applied loads, the anchor foot132bof the present invention comprises a stabiliser136comprising a plurality of discrete fingers or digits138extending from an upright portion140such that loads are distributed amongst the plurality of fingers138, e.g. separate fingers. In the particular embodiment of the present invention shown inFIG.16, the upright portion140comprises an anchor plate arranged to rigidly connect to the upright column116a,116band the diagonal brace82by one or more bolts so as to bear the load of the upright column116a,116band the applied load of the diagonal brace82. Like the anchor plate134of the first embodiment of the present invention shown inFIG.14, the anchor plate140is oriented such that the surface of the anchor plate140with the greatest surface area lies in the same vertical plate as the three upright columns116a,116b,116cmaking up the braced tower80of the present invention (seeFIG.11). Using the terminology of the present invention, the upright columns116a,116b,116c, the diagonal braces82and the surface of the anchor plate134,140all lie in the same plane, i.e. they are co-planar.

One or more of the discrete fingers138of the anchor foot132bextend or span out in two or more different directions from the upright portion140so as to provide improved stability of the anchor foot132b. One or more of the fingers138are of different lengths to aid with the stability of the anchor foot132bof the present invention. The length of the fingers138can be different so provide different levels of stability of the braced tower80. One or more connecting webs142are used to support the one or more of the fingers138from axial movement. The anchor foot132bis anchored to the concrete foundation by one or more bolts through holes in the fingers138of the anchor foot132b.

In the particular embodiment of the present invention, five fingers138of varying length are shown (seeFIG.16b) that extend from the upright portion140with holes at the distal ends of the fingers138for anchoring the anchor foot to the ground via an anchor bolt. The anchor foot132baccording to the second embodiment of the present invention can be formed as a single body, e.g. casting, or separate parts joined together, e.g. welding.

Anti-Seismic Grid Framework System

While the current grid framework structure114is adequate where the ground is relatively stable, i.e. having a spectral acceleration less than 0.33 g categorised as Type A and Type B events, this cannot be said where the grid framework structure is subjected to powerful seismic events generating strong lateral forces in excess of 0.55 g spectral acceleration categorised as a Type C or D seismic event. Such powerful seismic events compromise the structural fasteners joining the grid elements (e.g. track support elements) at the intersections, causing them to work their way loose or out of the cap plates to which they are bolted to. The result is the weakening or complete loss of structural integrity of the grid framework as the lateral forces no longer are able to be transferred safely down to the structural foundations. Failure may occur at the intersections of the grid members or track support elements making up the grid. The bracing towers80described above used to maintain the structural integrity of the grid framework structure may not able to withstand the lateral forces as a result of powerful Type D seismic events well in excess of 0.55 g.

In a particular embodiment of the present invention, an anti-seismic grid framework system206is provided whereby the base or footing of the grid framework structure114is adapted with a flexible structure so as to damp or suppress or attenuate excessive movement of the grid framework structure relative to the ground or ground motion as a result of seismic forces. In the particular embodiment of the present invention, the base or footing of the grid framework structure114is made flexible by the provision of a seismic isolation system208and comprises at least one base isolation device204that suppresses or attenuates seismic waves.FIG.17is an example of an anti-seismic grid framework system206whereby the grid framework structure114is uncoupled from its foundation by the at least one base isolation device204to protect the grid framework structure114from lateral forces as a result of ground motion. The base isolation device204effectively dampens ground motion during strong seismic events and thereby, suppresses movement of the grid framework structure which effectively increases the period of vibration of the grid framework structure.

A cross sectional view of the seismic isolation system208according to the embodiment of the present invention is shown inFIG.18. The seismic isolation system208comprises a superstructure or diaphragm202and a substructure or foundation200. The superstructure202comprises at least part of and, in some cases, all of the load bearing structure of the grid framework structure114. The superstructure202can be a concrete load bearing structure. The grid framework structure114, more specifically, the footing of the upright columns116are mounted to the superstructure202by one or more anchor bolts. The upright columns116and thus, the grid framework structure114is mounted to the superstructure202by one or more adjustable feet90and/or anchor feet132. Further detail of the adjustable foot and the anchor foot is discussed above. The requirement of the superstructure202at the base of the grid framework structure has the benefit of redistributing forces concentrated from one or more discrete braced frame locations to a relatively larger number of support points. The substructure200comprises at least the grid framework structure's foundation. This could be the ground or a concrete foundation.

Inter disposed between the superstructure202and the substructure200are one or more base isolation devices204. The distribution of the base isolation devices204can be tuned to remove any irregularities or possible torsional issues in the superstructure202. The one or more base isolation devices204decouples the superstructure202and thus, the grid framework structure114mounted thereon from the motion of the substructure or ground motion during earthquakes. In this way, large deflections and high accelerations are prevented being transmitted to the grid framework structure114. The number and distribution of the one or more base isolation devices202is dependent on the weight of the grid framework structure, the height of the grid framework structure, i.e. container depth, Z and the composition of the ground. For example, while the energy of seismic waves with higher frequencies tends to be absorbed by solid rock soil, the seismic waves with lower frequency pass through the solid rock soil without being absorbed but are eventually amplified by soft sediments. As can be seen inFIG.17, one or more base isolation devices are distributed in an array having a grid like pattern, each of the base isolation devices204being respectively mounted between the substructure200and the superstructure202by lower and upper mounting plates. The number and the pattern of one or more base isolation devices inter-disposed between the superstructure and the substructure is further discussed below. The base isolation devices provide the lateral flexibility of the seismic isolation system to attenuate ground movement being transmitted to the grid framework structure. Various known base isolation devices that attempt to get maximum energy dissipation by damping are permissible in the present invention. Options include elastomeric bearings, sliding bearings or a combination thereof.

In a first embodiment of the present invention, the at least one base isolation device comprises an elastomeric bearing1204which relies on the elastomeric properties of the bearing to attenuate lateral movement. The elastomeric bearing shown inFIG.19comprises a laminated assembly1206of alternating elastomeric layers1207and rigid layers1208vulcanized or glued together in a rubber body and inter disposed between upper and lower mounting plates1210a.1210bfor fixing to the superstructure202and substructure200respectively. An example of an elastomeric bearing is described in U.S. Pat. No. 4,499,694 (Development Finance Corporation of New Zealand), U.S. Pat. No. 4,593,502 (Development Finance Corporation of New Zealand), EP3412929 (Olies Corporation) and/or EP2039958 (Olies Corporation); the details of which are incorporated herein by reference. The elastomeric bearing1204allows flexibility through its ability to move but return to its original position. For example, at the end of an earthquake, if the grid framework structure has not returned to its original position, the restoring force of the at least one elastomeric bearing will slowly bring the grid framework structure back to its original position.

The elastomeric layer1207is composed of an elastomeric material such as natural or synthetic rubber and the rigid layer is preferably fabricated from steel, aluminium, fiberglass, fabric or other suitable rigid material. The elastomeric layers1207provide lateral flexibility and the elastic restoring force to return the elastomeric bearing to its original position. The rigid layers1208reinforce the elastomeric bearing by providing vertical load capacity and preventing lateral bulge. The individual layers in the assembly are bonded to one another to form a unitary assembly or structure, e.g. by vulcanization.

The grid framework structure together with one or more containers stacked in the vertical columns and the one or more load handling devices remotely operative to move the one or more containers stored in the grid framework structure make up a storage system of the present invention. The weight of one or more load handling devices operative on the grid and the additional weight of the containers not only increases the weight of the storage system but also increases the period of oscillation which reduces the spectral acceleration. As there is a lot of mass in the storage system, after a strong earthquake, the grid framework structure could continue to sway back and forth on one or more base isolator devices. Also shown inFIG.19, is an optional energy dissipating core1212provided in a hollow portion in the interior of the laminated body1206and extending across the laminated body. For the purpose of the present invention, the term “laminated assembly” and “laminated body” are used interchangeably in the specification to mean the same feature. The energy dissipating core1212has a cylindrical shape and is adapted to damp the vibration in a shearing direction B of the laminated body by absorbing vibrational energy in the shearing direction B of the laminated assembly through deformation in the shearing direction B. The energy dissipating core1212is typically composed of lead, tin, zinc, aluminium, copper, nickel, or an alloy thereof and can be press fitted in place. Lead is preferably chosen because of its plastic properties. This is because lead is able to deform with the movement of the earthquake but will revert to its original shape, and is capable of deforming many times without losing its strength.

In a particular embodiment of the present invention shown inFIG.19, the body of the laminated assembly1206has a circular cross-sectional shape such that the body of the laminated assembly1206has a cylindrical outer peripheral surface as shown in the top plan view of the elastomeric bearing inFIG.20. Together with the hollow portion within the interior of the body of the laminated body, the laminated assembly constitutes an assembly of alternating annular elastomeric and rigid layers. The annular elastomeric and rigid layers are bonded together by vulcanization to form a cylindrical laminated body. The outer peripheral surface of the cylindrical laminated body is protected by an outer rubber covering1214. The body of the laminated assembly1206is inter disposed between upper1210aand lower mounting plates1210b. The upper and lower mounting plates comprises one or more mount holes1216to mount the body of the laminated assembly to the superstructure and the substructure respectively. The one or more mounted holes are distributed around the circumferential edge or the peripheral edge of the upper and lower mounting plates.

Also shown inFIG.19is the upper and lower mounting plates1210a,1210bare respectively joined by one or more bolts to an upper connection steel plate1218aand a lower connection steel plate1218b. Optionally, the upper connection steel plate1218aand/or the lower connection1218bplate can comprise a relatively low friction material that enables the upper connection steel plate1218aand/or the lower connection1218bto slide against the respective upper mounting plate and/or the lower mounting plate.

The provision of the upper connection steel plate1218aand the lower connection steel plate1218bare optional and the body of the laminated assembly can be inter disposed or sandwiched directly between the upper and lower mounting plates. The body of the laminated assembly is not just limited to having a cylindrical outer peripheral surface and other shapes, e.g. rectangular or square shape, are permissible in the present invention. For example,FIG.21shows an alternative configuration of the elastomeric bearing2204according to an embodiment of the present invention whereby the body of the laminated assembly has a square or rectangular cross-sectional shape. Also shown inFIG.21, the body of the elastomeric bearing2204comprises alternating elastomeric layers2207and steel shims2208vulcanized or glued together, i.e. the steel shims are embedded within an elastomeric body2206. An energy dissipating core2212is adapted to damp the vibration in a shearing direction B of the laminated body.

A more cost effective alternative to dissipate energy by elastic deformation permissible in the present invention, is the body of the laminated assembly can be replaced by a stack or laminated assembly of bonded recycled tyre rubber pads, each of the rubber pads contain interleaved steel reinforcing chords. The steel chords are considered to function similar to the rigid layers in that they reinforce the elastomeric bearing by providing vertical load capacity and preventing lateral bulge.FIG.22is a schematic layout of the laminated assembly3206of recycled rubber tyre layers or pads3210. As can be seen to the left ofFIG.22, the tread part of the recycled tyres3209forms each of the rubber layers or pads of the elastomeric bearing assembly. The tyre pads3210are bonded together using a suitable adhesive. The use of recycled tyre rubber pads as a elastomeric bearing3204for attenuating seismic waves was extensively studied by Mishra et al (Mishra, H. K., Igarashi, A., Matsushima, H. and Furukawa, A (2012) “Experimental and analytical study of unbonded and bonded scrap tire rubber pad as base isolation device” 15th WCEE, Lisbon Portugal) and Munoz et al (Munoz, A. et al (2019) “Applicability Study of low-cost seismic isolator prototype using recycle rubber, Journal TECNIA Vol. 29, No. 2). As with the elastomeric bearing shown inFIGS.19and21, the body of the laminated assembly3206of elastomeric layers are sandwiched between upper and lower mounting plates (not shown) for respectively mounting to the superstructure and substructure. Whilst not as effective in attenuating seismic waves as the elastomeric bearing1204,204comprising a laminate assembly of elastomeric and rigid layers described above, the assembly3206of recycled tyre pads provides a low cost alternative that can be tailored to meet local building regulations. For example, the number and distribution of the base isolation devices inter disposed between the superstructure and the substructure can be tailored to provide different attenuation properties depending on the either the vulnerability of the grid framework structure to seismic effects in particular areas and/or the local building regulations. Further details of the different design alternatives of the base isolation devices are discussed below.

In all of the embodiments of the elastomeric bearing shown inFIGS.19,20,21, and22, the body of the laminated assembly is sandwiched between the upper and lower mounting plates. One or more of the elastomeric bearings can optionally comprise a slider disc (not shown) disposed between the laminated assembly and either the upper mounting plate1210aor the lower mounting plate1210bor both. The slider disc preferably comprises PTFE (Teflon) and allows the upper or the lower bearing plate to move relative to the body of the laminated assembly. The upper mounting plate and/or the lower mounting plate may comprise one or more stops that butt up against an upper end or lower end of the laminated assembly. The slider disc provides additional damping through the sliding friction of the contact surface between the slider disc and the upper mounting plate and/or the lower mounting plate.

FIG.32schematically illustrates an elastomeric bearing with slider disc. InFIG.32(a), the slider disc1220is disposed between the laminated assembly1206and the upper mounting plate1210a. The upper mounting plate1210acomprises stops1222. InFIG.32(b), the slider disc1220is disposed between the laminated assembly1206and the lower mounting plate1210b. The lower mounting plate1210bcomprises stops1222. InFIG.32(c), there are two slider discs1220, the first slider disc1220disposed between the laminated assembly1206and the upper mounting plate1210a, and the second slider disc1220disposed between the laminated assembly1206and the lower mounting plate1210b. Both the upper mounting plate1210aand the lower mounting plate1210bcomprise stops1222.

Embodiments of the elastomeric bearing including a slider disc provide the combined functions of isolation and allowing lateral sliding movement. This better distributes the load of the superstructure and grid between the base isolation devices, and accounts for uneven movement between the support points. This is particularly useful in smaller fulfilment centres, where the loads are smaller, and in some examples the better distribution of loads may mean that a lower quality concrete may be used for the superstructure, thus saving on manufacturing and installation costs.

In a second embodiment of the present invention, the at least one base isolation device can be based on a sliding system. In a sliding system, energy is dissipated by one or more slide pendulum bearings or friction pendulum bearings where a slider is typically arranged to slide against a surface, e.g. by exploiting the reciprocal sliding arrangement between a convex and spherical concave surface. For the purpose of the present invention, the term “sliding pendulum bearing”, “slide pendulum bearing”, “slide bearing” and “friction pendulum bearing” are used interchangeably in the specification to mean the same feature. The reciprocal sliding arrangement between a convex and spherical concave surface allows the sliding bearing to naturally return to its original position without relying on the elastomeric properties of the body of the bearing, i.e. the concave sliding surface allows a restoring force to ensure self-centring capability. The simplest sliding system comprises a single friction pendulum bearing which consists of a spherical concave surface supporting a frictional slider. The geometry and/or the friction between the slider and the spherical concave surface serves an important function of dissipating the energy associated with seismic movements. The geometry of the contact surface between the slider and the spherical concave surface relates to the radius of curvature of the spherical concave surface. The radius of curvature of the spherical concave surface influences the period of oscillation of the slider and thus the restoring force. The greater the radius of curvature of the spherical concave surface, the greater the period of oscillation. The lateral travel of the slider is accompanied with a vertical movement of the superstructure, and thus, the mass of the storage system provides a restoring force. The lifting of the superstructure during seismic ground motions results in an equivalent pendulum motion having one dynamic natural period of vibration based on a pendulum motion. The natural period of vibration of the sliding system (T) is equivalent to:
T=2π(L/g)1/2(1)where L is the effective pendulum length and g is the acceleration due to gravity. The effective pendulum length L is proportional to the radius of curvature of the spherical concave surface given by the equation:
L=Rcos θ  (2)where θ is the angle the pendulum makes with the vertical and R is the radius of curvature of the spherical concave surface.

In addition to controlling the geometry of the spherical concave surface, the coefficient of friction between the slider and the spherical concave surface is controlled or predetermined so as to provide resistance to loads or forces from the normal operation of the grid framework structure but low enough to be overcome in a seismic event. This prevents the one or more slide bearings being activated, i.e. the frictional slider slipping, during normal operation or use of the storage system. The forces exerted through normal operation of the storage system include but are not limited to the forces generated by one or more load handling devices operational on the grid which include the load handling devices travelling on the rail/tracks as well as the operation of the grabber device to pick and lower a container within the vertical storage columns. The friction coefficient is overcome in a seismic event allowing the slider to move on its respective spherical concave surface. The coefficient of friction between the slider and the spherical concave surface can be tailored by coating or treating the contact surface between spherical concave surface and the slider with a special material. For example, the spherical concave surface is coated with the special material to provide a tailored coefficient of friction between the slider and the spherical concave surface. Equally or in addition, the coefficient of friction between the slider and the spherical concave surface can be controlled by coating just the slider with a bearing liner material. In the case of the elastomeric bearing discussed above, the restoring force can be controlled by controlling the elastic properties of the elastomeric material, e.g. controlling the number of elastomeric and rigid layers and the composition of the energy dissipating core such that the elastomeric bearing is not activated during normal operation of the storage system. This allows the storage system to function normally during operation without the base isolation device being activated.

To cater for different intensities of earthquake ground motion, preferably, the slide bearing comprises multiple slide bearings connected in series to support the grid framework structure each of the multiple slide bearings providing distinct sliding pendulums. When connected in series, a lateral displacement of the substructure will be distributed amongst one or more of the multiple slide bearings. The sum of the displacements occurring in the multiple pendulum mechanisms is equal to the total structure displacement at a support point. In this way, different pendulum mechanism become active at different strengths of seismic motions. This is to mitigate the effects of a sliding bearing selected to minimize the impact of lower strength service level earthquakes that are expected to occur more than once during the life of the grid framework structure but being less effective to minimize the impact of more stronger earthquakes that a have probability of occurring during the life of the grid framework structure.

The different pendulum mechanisms become active at different strengths of seismic motions by using different coefficient of friction for the different pendulum mechanisms, i.e. they exhibit different hysteretic properties at different displacements. In this manner, as each pendulum mechanism is activated both the effective length pendulum length and the effective friction increase as each pendulum mechanism is sequentially activated. In a preferred embodiment of the present invention, the sliding pendulum bearing provides three distinct pendulum mechanism or so called Triple Pendulum™ bearing supplied by Earthquake Protection Systems (EPS), Inc. having a place of business in Vallejo, Canada, that progressively exhibits different hysteretic properties at different stages of displacement. Detail of the Triple Pendulum™ bearing is further discussed in US2006/0174555 (Victor, Zayas and Stanley Low), the details of which are incorporated herein by reference.

FIG.23shows a cross-sectional view of Triple Pendulum™ bearing4204forming the at least one base isolation device of the seismic isolation system of the present invention. As discussed in US2006/0174555 (Victor, Zayas and Stanley Low), the Triple Pendulum™ bearing comprises four concave surfaces to provide three independent pendulum mechanisms. The Triple Pendulum™ bearing comprises an upper bearing element or plate4206having a downward facing concave spherical surface4208with a specified radius of curvature, R1and a lower bearing element4210having an upward facing concave spherical surface4212with a specified radius of curvature, R2. The upper bearing element4206and the lower bearing element4210can be in the form of an upper bearing plate and a lower bearing plate and each can be fabricated from a single material such as stainless steel or iron. A coating is deposited on the concave spherical surface4208,4212of the upper bearing element4206and the lower bearing element4210to facilitate sliding. Bolt holes (not shown) are formed around the perimeters of the upper bearing element4206and the lower bearing element4210for connecting the sliding pendulum bearing to the superstructure and the substructure respectively. Inter disposed and in sliding arrangement between the upper bearing element4206and the lower bearing element4210are a plurality of sliders comprising outer sliders4214,4216and an inner slider4218.

For a Triple Pendulum™ bearing, the outer sliders comprises a first slider4214and a second slider4216. Inter disposed and in sliding arrangement between the outer sliders is the inner slider or a third slider4218. The contact surface of each of the first4214, second4216and third sliders4218are adapted so that each of the first, second and the third sliders progressively slide along their respective concave spherical surfaces to provide pendulum mechanisms that become active at different strengths of seismic motion. The first slider4214has a convex surface4214bthat slides along the upward facing concave spherical surface4212of the lower bearing element4210and has a spherical concave surface4214chaving a radius of curvature R3which is smaller than the radius of curvature of the lower bearing element R2. The contact surface between the first slider4214and the lower bearing element4210is adapted to provide a first coefficient of friction for a design level of earthquake. This could be achieved by either lining the upward facing concave spherical surface4212of the lower bearing element4210and/or lining the convex surface4214bof the first slider4214with a bearing lining material.

The second slider4216has a convex surface4216bwhich is adapted to slide along the downward facing spherical concave surface4208of the upper bearing element4206and also has a concave spherical surface4216chaving a radius of curvature R4equal to the radius of curvature of the concave spherical surface Ra of the first slider4214. Like the first slider4214, the radius of curvature R4of the concave spherical surface4216cof the second slider4216is smaller than the radius of curvature R1of the upper bearing element4206. The contact surface between the second slider4216and the upper bearing element4206is adapted to provide a second coefficient of friction but this time suitable for a maximum credible earthquake, typically two to three times or more the friction coefficient of the first slider4214. In this way, the first slider4214is adapted to slide along the upward facing concave spherical surface4212of the lower bearing element4210before the second slider4216is made to slide along the downward facing concave spherical surface4208of the upper bearing element4206.

The third slider4218forms an inner slider and is disposed between the first slider4214and the second slider4216. The third slider4218has convex spherical surfaces at the bottom and top4218b,4218cof the slider that is arranged to respectively slide along the concave spherical surfaces of the first slider4214and the second slider4216. The convex surfaces4218b,4218cof the third slider4218is surfaced with a bearing liner material such that the sliding surface between the third slider4218and the first slider4214has a third coefficient of friction and the sliding surface between the third slider4218and the second slider4216has a fourth coefficient of friction. The coefficient of friction between the sliding surfaces of the third slider4218and both the concave spherical surfaces of the first slider4214and the second slider4216are equal, i.e. the third coefficient of friction is substantially equal to the fourth coefficient of friction. However, the third and/or the fourth coefficient of friction is typically ½ to ⅓ of the coefficient of friction of the first slider against upward facing concave spherical surface of the lower bearing element, i.e. the first coefficient of friction. The low coefficient of friction between the contact surface of the third slider4218and the concave spherical surfaces of the first slider4214and the second slider4216(i.e. the inner pendulum mechanism) minimizes high frequency vibrations of the ground motion being transmitted to the grid framework structure via the superstructure. Reducing such high frequency vibrations mitigates damage to the one or more load handling devices operative on the grid and/or the containers stored within the vertical storage columns, particularly spillage of the contents of the containers. High frequency vibrations have a tendency to derail the one or more load handling devices from the tracks and in a worst case scenario cause the one or more load handling devices to topple over on the grid. Moreover, owing to the low coefficient of friction the third slider is able to accurately return to its equilibrium or original position once displaced.

To protect the interior surfaces, in particular the contact surfaces of the sliders from contamination and to maintain the assembly of the sliders together, the upper bearing element and the lower bearing element can be joined together with an elastic seal (not shown) around the periphery of the upper and lower bearing element. The elastic seal is configured to accommodate large deformations required during earthquake motions. Equally, to protect the interior surfaces of the sliders from contamination and to maintain the components of the first slider4214and the second slider4216together, the first slider and the second slider would typically be joined together with an elastic seal (not shown) around the perimeter of the first and second slider.

FIG.24(a to c) shows the translation of the sliders during earthquake motions to provide the three different pendulum mechanisms of the Triple Pendulum™ bearing. Further detail of the Triple Pendulum™ bearing is discussed in US2006/0174555 (Victor, Zayas and Stanley Low), the details of which are incorporated herein by reference The stages of the lateral horizontal movement of the individual sliders during ground motion are dependent on the friction of the contact surfaces between the respective sliders and against the spherical concave surfaces of the upper and lower bearing elements. In a first instance of ground motion as shown inFIG.24a, the coefficient of friction is such that the first slider4214translates horizontally relative to the second slider4216, but due to the friction (1stcoefficient of friction) between the first slider4214and the lower bearing element4210and the friction (2ndcoefficient of friction) between the second slider4216and the upper bearing element4206both the first slider4214and the second slider4216do not move relative to the respective concave surfaces of the lower bearing element4210and the upper bearing element4206. In other words, the friction between the first slider and the second slider against the respective concave spherical surface of the lower bearing element and the upper bearing element are too high during the initial displacement the slide bearing. A first pendulum motion is thus only provided by the third slider4218rotating and translating horizontally along the concave spherical surface of the first slider4214and the second slider4216. The coefficients of friction between the bottom and top convex surface4218b,4218cof the third slider4218and the concave spherical surfaces of the first slider4214and the second slider4216are such that the third slider4128is able to slide easily so as to dampen the high frequency vibrations.

The first pendulum motion is demonstrated inFIG.24a. As the ground motion progressively gets larger, the first coefficient of friction is overcome causing the first slider4214to slide along the concave spherical surface4212of the lower bearing element4210, and therefore provide a second pendulum motion. The movement of the first slider relative to the lower bearing element is demonstrated by the arrow shown inFIG.24b. WhilstFIG.24bshows the first slider initially moving towards the right, the movement of the first slider is not limited to one direction and can initially move towards the left. In reality, the sliders move in both left and right directions as a result of vibrations of the ground motion. Finally, as the ground motion progressively gets larger, the second coefficient of friction is overcome causing the second slider4216to slide along the upper bearing plate4206to provide a third pendulum mechanism. This is demonstrated inFIG.24c. The coefficients of friction of the sliders are tailored to provide different levels of damping at different strengths of seismic motions.

Multiple slide bearings disposed between the substructure and the superstructure are arranged to isolate the grid framework structure from ground motions at different strengths of seismic motion. For example, the separate pendulum mechanisms of the slide bearing can be tailored to dampen various areas or components of the storage system that are more susceptible to different frequencies of vibration. Whilst the braced towers provide some degree of structural integrity and support to the grid framework structure from ground motions resulting from weak seismic events, e.g. spectral acceleration less than 0.55 g, this may not be the case of the one or more load handling devices operative on the grid or tracks. A slide bearing can be tailored so that different pendulum mechanisms becomes active at different strength of seismic motion so as to provide damping for the different areas of the storage system. These include but are not limited to the one or more load handling devices operative on the grid and/or the one or more containers stacked within the vertical storage columns.

In addition to providing different levels of damping from multiple slide bearings, combination of different base isolation devices can also be used to provide the necessary base isolation properties at different strengths of seismic motions, i.e. load capacity, lateral flexibility, energy dissipation and self-centring capability. For example, slide bearings with low friction can be combined with elastomeric bearings discussed above. The slide bearings with low friction are able to dampen high frequency vibrations that are transmitted to the grid framework structure and the elastomeric bearings are able to dampen strong seismic forces.

Various other factors play a critical role in the effective isolation of the grid framework structure from seismic ground motions. These include but are not limited to the distribution and the pattern of one or more base isolation devices, the type of base isolation device, and/or the size of the base isolation device. As shown inFIG.25, the base isolation devices are distributed in a grid like pattern between the substructure and the superstructure. Amongst other factors discussed above, the number of base isolation devices distributed between the substructure and the superstructure is also dependent on the size of the base isolation device. For example, use of larger base isolation devices204allows the base isolation to be spread out but requires a thicker superstructure to redistribute the concentrated forces of the weight of the storage system amongst the base isolation devices.FIG.17demonstrates the use of larger base isolation devices204each having a width in the range 400 mm to 460 mm and a height in the range 190 mm to 210 mm distributed in a 6 m×6 m grid pattern and supporting a concrete superstructure 200 mm thick. The base isolation device shown inFIG.17could be based on the elastomeric bearing1204,2204,3204or the Triple Pendulum™ 4204 discussed above or a combination of both bearing types. A smaller distribution of 3 m×3 m can be attained with the use of smaller base isolation devices.FIGS.25and26shows an alternative distribution of the base isolation devices204between the substructure and the superstructure using smaller base isolation devices having a width in the range 150 mm to 250 mm and a height in the range of 50 mm to 80 mm. Using smaller base isolation devices204, the base isolation devices are distributed in a 3 m×3 m grid like pattern. As more base isolation devices are distributed between the substructure and the superstructure, the seismic isolation system can afford to use a thinner superstructure. In the particular embodiment shown inFIG.25, the thickness of the concrete superstructure is about 150 mm. The distribution of the base isolation devices can be tuned to remove any irregularities or possible torsional issues in the superstructure. The large continuous grid framework structure extending over a large footprint would mean that the superstructure or diaphragm is equally continuous to accommodate the large footprint of the grid framework structure.

The constructability of the substructure can be adapted to include one or more crawl spaces or trenches to provide inspection areas for the one or more base isolation devices. For example, the substructure can comprises a plurality of pillars or plinths for mounting the one or more base isolation devices on the pillars such that the one or more base isolation devices are disposed between the pillars and the superstructure. The spaces between the pillars or plinths in the substructure provide crawl spaces.

FIG.27is an alternative arrangement of the seismic isolation system208of the present invention. Here, the one or more base isolation devices204are disposed in a well or a depression205in the substructure200having upstanding walls207. The superstructure202is mounted on the one or more base isolation devices204within the well such that a top wall of the superstructure202is level or flush with the surrounding area. The area of the depression or well is sized such that the superstructure disposed within the well is able to be displaced laterally to cater for different seismic motions. To achieve this, the spacing206between the edges of the superstructure and the upstanding walls207of the well are sized to allow lateral movement of the superstructure202on the one or more base isolation devices204. Preferably, the substructure200is cast in place to provide a depression or well205. The spacing209between the edge of the superstructure and the upstanding walls207of the substructure can be covered with a protective covering to improve safety. Examples of a protective covering include but are not limited to a resilient member and/or moveable slats that slide on top of each other.

Different combinations of the base isolation devices can be used to attenuate different strengths of seismic motions and providing different restoring forces. For example, an array of base isolation devices can be disposed between the superstructure and the substructure to comprise a combination or mixture of elastomeric bearings and sliding pendulum bearings.

In some embodiments of the invention, the spacing of the base isolation devices can be 10 metres. The base isolation devices can be arranged in a regular repeating pattern between the superstructure and the substructure. For example, in a regular square array or grid pattern (spacing 10 m×10 m). The isolators could also be arranged in different patterns, for example a hexagonal grid pattern, or a square grid pattern with a base isolation device in the centre of each of the squares of the square grid pattern, or any other suitable arrangement. The same pattern of base isolation devices can be used throughout the whole space between the substructure and the superstructure, or different patterns or distributions of base isolation devices can be used under different parts of the grid framework structure. Optionally, the base isolation devices can be arranged in an irregular pattern between the superstructure and the substructure, where the concentration of the base isolation devices is greater in one or more areas between the superstructure and the substructure to provide increased damping in those areas.

In embodiments where both elastomeric bearings and sliding pendulum bearings are used as base isolation devices, either the same spacing or distribution pattern can be used for both types of isolation device, or different spacing or distribution patterns can be used for the different types of base isolation devices. Different kinds of base isolation devices can be used under different parts of the grid, or the different kinds of base isolation devices may be interspersed.

The area density of base isolation devices in a regular square array at a spacing of 10 m is one per 100 square metres, or 0.01 per square metre. This density may be applied to other arrangements of base isolation devices. The area density of the base isolation devices may be in the range 0.005-0.015 devices per square metre.

The superstructure on which the grid is supported may be composed of pure concrete, or may comprise a composite steel/concrete slab. In the case where the superstructure comprises a composite steel/concrete slab, the concrete may be poured onto a steel decking, such that the concrete is cast and forms a one-piece slab with the steel decking.

The concrete used in the superstructure (whether pure concrete or composite steel/concrete) should be of a suitable quality. The concrete for the superstructure and substructure may be made to a standard specification, with a controlled mix ratio, without defects, flat, level, of a suitable concrete grade, and manufactured within specified tolerances. In some embodiments, the concrete may contain one or more additives. Additives may be used to increase the life of the concrete, control the speed of setting, control the entrainment of air, increase hardness, increase strength, reduce permeability, reduce shrinkage, reduce corrosion, or otherwise control the properties of the substructure and/or superstructure.

In some embodiments, plinths can be used to provide additional space between the substructure and the superstructure. Additional space between the substructure and superstructure can be used for a range of different functions, for example to allow space for employee car parking at a fulfilment centre. Also, the additional space provides access underneath the superstructure, so is convenient for inspection and maintenance. Plinths may be located on top of the base isolation devices, one plinth for each base isolation device. Alternatively or additionally, lower plinths may be located below and supporting the base isolation devices, one lower plinth for each base isolation device. The plinths may be steel, or concrete, or any other suitable material.

The superstructure may additionally comprise one or more beams, supporting a concrete or composite concrete/steel slab.FIG.28illustrates an exemplary embodiment of a seismic isolation system where the superstructure202comprises a slab203supported by beams210,212. The beams210,212may be steel, and may be I-beams as illustrated inFIG.28, or any other suitable shape. Primary beams210extend substantially horizontally in the first direction (x-direction), substantially perpendicular to secondary beams212extending substantially horizontally in the second direction (v-direction). The beams210,212form a grid-like pattern in a substantially horizontal plane. Base isolation devices204are located between the superstructure and the substructure200, supported by the substructure200. The primary beams210are supported by the base isolation devices204, and the secondary beams212are supported by the primary beams210. The slab203is supported by the secondary beams212.

In the embodiment illustrated inFIG.28, the base isolation devices204are arranged in a regular square array with spacing of 10 m in both x and y directions. Four base isolation devices are shown for ease of illustration, but it will be appreciated that larger arrays of base isolation devices can be used, and may extend over a larger area. Since the primary beams210are supported by the base isolation devices, the spacing of the primary beams210in the y-direction is 10 m, the same as the spacing for the base isolation devices. The secondary beams212are spaced more closely together, in this case with a spacing of 2 m in the x-direction.

FIG.29illustrates the seismic isolation system ofFIG.28, as a side view, showing one base isolation device disposed between the substructure200and the superstructure202for ease of illustration. The base isolation device204is positioned on the substructure200. A plinth214is supported by the base isolation device204. In the particular embodiment shown inFIG.29, the plinth214is shown mounted on the base isolation device204such that the plinth is disposed between the substructure200and the superstructure202. A primary beam210is supported by the plinth214such that the plinth214is sandwiched between the base isolation device204and the primary beam210. A secondary beam212is supported by the primary beam210. The slab203is supported by the secondary steel beam. The upright columns116of the grid framework structure are supported by the slab203. The superstructure202comprises the composite steel/concrete slab203, the primary beams210, and the secondary beams212. In some embodiments, the seismic isolation system can include building columns220that provide structural support for the building housing the anti-seismic grid framework system206, and/or pillars222that extend downwards below ground level. In some embodiments, in addition to the plinths214located between the base isolation devices204and the superstructure, additional plinths216(referred to as lower plinths216) may be provided below the base isolation devices204. The use of both plinths214and lower plinths216has the advantage of further increasing the available vertical space between the substructure200and the superstructure202, so that this space can be used for applications such as car parking.

FIG.30schematically illustrates a seismic isolation system incorporating building columns220, pillars222, and lower plinths216. The substructure200is at ground level218. Pillars222extend downwards below ground level into the earth to provide a stable foundation for the building housing the seismic isolation system. Lower plinths216are located at ground level, either partially within (as illustrated) or supported by the substructure200. A subset of the lower plinths216are disposed above the pillars222. Base isolation devices204are located on the lower plinths216, and plinths214are supported by the base isolation devices204(so the base isolation devices204are located between the lower plinths216and the plinths214). The superstructure202is supported by the plinths214.

A subset of plinths, lower plinths, and base isolation devices support building columns220, which extend upwards from the plinths. These plinths, lower plinths, and base isolation devices supporting the building columns220will be referred to with reference numbers214a,216a, and204arespectively. The building columns220are located above the pillars222extending downwards into the ground, in order to withstand large compressive loads and support the weight of the building structure above. The building columns220are supported by plinths214a. The plinths214aare supported by base isolation devices204a. The base isolation devices204aare supported by lower plinths216a, which are located above and supported by the pillars222.

The subset of base isolation devices204awhich are located above the pillars222and below the building columns220may be sliding pendulum bearings. Sliding pendulum bearings can withstand high compressive loads, so are suitable for use in this location. In embodiments where a combination of sliding pendulum bearings and elastomeric bearings are used, the subset of base isolation devices204awhich are located above the pillars222and below the building columns220may be sliding pendulum bearings, and the other base isolation devices204may be elastomeric bearings.

FIG.31schematically illustrates a base isolation device204asupporting a building column220. The substructure200is shaped such that the base isolation device204ais located in a well or depression205. The base isolation device204acomprises a top isolator plate230and a bottom isolator plate232. In applications where the base isolation device204ais an elastomeric bearing, the upper mounting plate1210aand lower mounting plate1210bmay be the same as the top and bottom isolator plates230,232respectively. The bottom isolator plate232of the base isolation device204ais mounted on a base plate226, which is mounted on the substructure200by anchor bolts228. A plinth214ais supported by the base isolation device204a, with a plinth base plate230mounted to its underside. The plinth base plate is mounted directly on top of the top isolator plate230of the base isolation device204a. The plinth214asupports the superstructure202. In the embodiment illustrated inFIG.31, the superstructure202comprises beams212supporting a slab203, with the beams212being supported by the plinth214a.

Definitions

In this document, the language “movement in the n-direction” (and related wording), where n is one of x, y and z, is intended to mean movement substantially along or parallel to the n-axis, in either direction (i.e. towards the positive end of the n-axis or towards the negative end of the n-axis).

In this document, the word “connect” and its derivatives are intended to include the25possibilities of direct and indirection connection. For example, “x is connected to y” is intended to include the possibility that x is directly connected to y, with no intervening components, and the possibility that x is indirectly connected to y, with one or more intervening components. Where a direct connection is intended, the words “directly connected”, “direct connection” or similar will be used. Similarly, the word “support”30and its derivatives are intended to include the possibilities of direct and indirect contact.

For example, “x supports y” is intended to include the possibility that x directly supports and directly contacts y, with no intervening components, and the possibility that x indirectly supports y, with one or more intervening components contacting x and/or y. The word “mount” and its derivatives are intended to include the possibility of direct and indirect mounting. For example, “x is mounted on y” is intended to include the5possibility that x is directly mounted on y, with no intervening components, and the possibility that x is indirectly mounted on y, with one or more intervening components.

In this document, the word “comprise” and its derivatives are intended to have an inclusive rather than an exclusive meaning. For example, “x comprises y” is intended to include the possibilities that x includes one and only one y, multiple y's, or one or 10 more y's and one or more other elements. Where an exclusive meaning is intended, the language “x is composed of y” will be used, meaning that x includes only y and nothing else.