The present invention relates to a force limiting and energy dissipating system. More particularly, but not exclusively, it relates to an energy absorbing system to reduce the impact of earthquake induced sway or raking motion of storage racks and buildings.

BACKGROUND

Commercial and industrial storage rack systems are designed to hold various quantities of items and goods. While storage rack systems may withstand the vibrations caused by low levels of seismic forces, increased levels of seismic forces can both damage the racks and cause goods to fall off the racks.

Although they may vary in structure, a storage rack typically consists of a plurality of upright column pairs that are ordered in a rectilinear fashion to form two rows of upright columns. Usually a front row that is adjacent the passage way where forklifts may drive or automated systems operate, and a back row that may be adjacent a wall or a parallel passage. Between the columns are multiple horizontal shelves. The array of such shelves extends upwards to the top of the upright columns. Shelving or pallets installed across pairs of beams normally hold the items or materials being stored. The columns bear the weight of the items or materials and transfer that weight to the bottom of each column to the foundation on which the columns are installed. The racks in plan view are typically rectangular with lengths over 100 m possible, and typical widths of between 0.9 m and 3 m.

Swaying of the racks in the lengthwise direction can occur during an earthquake. This is due to the foundation moving in one direction and the inertial resistance of the masses (pallets) supported by a flexible structure resulting in a motion lag swaying of the rack. This movement can be described as racking. Lengthwise racking can result in very high forces being developed in the rack structure.

Typical ways to reduce the effect of lengthwise racking is to use diagonal ties. The ties may be tensioned cables that are generally anchored at one end to an upper region of the rack and at the other end to the foundation. Multiple ties may be used that form a zig zag pattern along the lengthwise direction of rack. The ties help brace and reduce movement in the lengthwise direction relative to the bottom of the racks. They can make the rack very rigid. This is not ideal as it may result in very high peak loads being experienced by the ties and/or the racks. This may result in catastrophic failure.

In this specification, where reference has been made to external sources of information, including patent specifications and other documents, this is generally for the purpose of providing a context for discussing the features of the present invention. Unless stated otherwise, reference to such sources of information is not to be construed, in any jurisdiction, as an admission that such sources of information are prior art or form part of the common general knowledge in the art.

It is an object of the present invention to provide an energy absorbing system which overcomes, or at least partially ameliorates some of the abovementioned disadvantages or which at least provides the public with a useful choice.

STATEMENTS OF INVENTION

In a first aspect the present invention may be said to be a device or mechanism or more preferably a control structure which is able to limit forces developed within itself or a structure (e.g. building or storage rack) it connects with and is seismically supportive of as it endures ground or base motion input from a seismic event.

The control structure may be comprised of a (preferably relatively inflexible) rocker frame which is pivotably connected to a structural base or structural member. Rotation of the rocker frame about its pivot(s) causes a pivotably anchored flexural member(s) (e.g. preferably plate) which is directly or indirectly connected to the rocker frame, but distal to the rocker frame pivot, to flexurally displace (preferably deform by for example bending). The flexural member(s) (plate(s)), which is a part of the control structure, is configured with free translational or free translational and free rotational boundary conditions to allow it to flex and yield about its minor bending axis to high elasto-plastic displacements (deformation) while maintaining a constant resistive yield force.

The stable constant resistive yield force produced by the flexing plate(s) enables the pivotable control structure to form a stable elasto-plastic mechanism which is able to flow and cycle to high elasto-plastic displacements with a constant resistive force while internal forces within it, or within any adjacent structure it is connected with and seismically supportive of, are maintained and limited to maximum values which are a function of the yield force produced by the flexing yield plate(s) which are part of it.

By flowing as a stable, high displacement capable, elasto-plastic mechanism, with constant resistive yield force, the control structure is limiting the magnitude of accelerations and dynamic forces that can develop within its members or the members of another structure it may be seismically supportive of, as it endures the ground motion (displacement, velocity, acceleration) input of a seismic event.

In one embodiment a rocker frame comprises a vertical (e.g. a tower) aspect and is pivotably connected to a horizontal structural base or foundation. The rocker frame connects by a double pin link or push rod to a flexure member (plate(s)) which is distal to the rocker frames pivot. In one embodiment the flexure member has translatable and rotational boundary conditions and connects to the structural base or foundation with anchor rods. In another embodiment the flexure member (plate(s)) has translational or translational and rotational boundary conditions and is set within a motion controlled rocker which is pivotably connected to the foundation base and maintains a preferably orthogonal connection between the flexure member(s) (plate(s)) and the double pin push rods which link the flexure plate(s) to the rocker frame.

In a further embodiment the rocker frame has two pivots and connects in a similar way to both a horizontal base or foundation and a relatively inflexible overhead structure member.

In a further embodiment the rocker frame has a horizontal (spanning truss) aspect and is pivotably connected at each end to vertical chords or towers which are pivotably connected to a horizontal base or foundation. The flexure member(s) (plate(s)) are preferably similarly distal to the rocker frame pivots and preferably connect to the rocker frame through a double pin link or push rod and to the vertical chords or towers by a pivotably connected rocker within which they are supported. The pivotable horizontally orientated rocker frame(s), preferably double pin links, flexure plate(s), plate rocker connectors, and pivotable columns or towers all parts of the control structure.

In a further embodiment a rocker frame comprises a vertical (tower) aspect and is pivotably connected to a horizontal base or foundation. The vertical chord(s) of the rocker frame are parallel with another set of adjacent exterior chords pivotably connected to the structural base of foundation. These exterior chords may connect first to the pivot inclusive centreline of the rocker frame with horizontal relatively inflexible pin ended ties. The flexure members (plates) which have translational or translational and rotational boundary conditions at one end and are fixed against all degrees of movement at their opposite end, are again distal to the rocker frame pivots, and are connected between and distributed along the rocker frame and the opposite face of the adjacent pivotable exterior chords. The pivotable vertically orientated (tower aspect) rocker frame, flexure plates, pin ended exterior chord to rocker frame ties and exterior chord(s) with pivotable base connections, all parts of the control structure.

In a further embodiment the rocker frame(s) may have a horizontal (spanning truss) aspect and is preferably pivotably connected at each end to the vertical chords or towers which are pivotably connected to a horizontal base or foundation. The horizontal exterior chords parallel with the horizontal chords of the rocker frame are similarly pivotably connected to the vertical chords or towers. The flexure members (plates) distal to the rocker frame pivots are preferably located between and along the horizontal chords of the rocker frame and the opposite face of the parallel exterior chords. Vertically orientated pin ended ties may link the exterior chords with the pivot included centreline of the rocker frames. The pivotable horizontally orientated (spanning truss aspect) rocker frames, horizontal exterior chords pivotably connected to the vertical chords or towers with pivotable structural base or foundation connections, the flexure plates and vertical ties connections horizontal exterior chords to centrelines of rocker frame all parts of the control structure.

In one embodiment, the flexural member is composed of steel.

In one embodiment, the elongate member is composed of metal plate.

In one embodiment, the flexural member is replaceable.

In one embodiment, the flexural member undergoes plastic deformation at a yield zone intermediate the first anchor and second anchor during a seismic event as a result of relative oscillatory movement between the rocker frame and the primary structure or base.

In one embodiment, the primary structure is or is part of a warehouse rack, building and/or large civil structure.

In one embodiment, the first anchor or second anchor rigidly constrains the first region so received at the anchor, in 6 degrees of freedom.

In one embodiment, there are a plurality of connector intermediate said rocker frame and said structure or base.

In a second aspect the present invention may be said to be a rocking tie anchor for anchoring at least one diagonal tie of or for a seismically supported structure to a foundation, the anchor having an upstand distally connected with an elongate flexure member to engage, or adapted to engage, the at least one tie; the flexure member having spaced zones or anchor regions to be held to and/or proximate to an underlying support of the structure,wherein at least one anchor region is configured to move in a lateral direction towards and away from the other anchor region, andwherein at least two anchor regions are configured to rotate about a rotational axis perpendicular to said lateral direction and parallel with the plane of the foundation.

In a third aspect the present invention may be said to be a racking constraining system having at least one diagonal tie to resist racking of a structure mounted on a foundation or base; wherein the at least one tie attaches from the rack to a tiltable tie anchor, the tie anchor being a rocker frame connected to an elongate flexure member (plates) held at spaced zones or anchor regions directly or indirectly to the foundation or base

Preferably the elongate flexure member (plates) is held at the spaced zones or anchor regions to the foundation or secondary flexure member base without compromise, or substantial compromise, of the flexure member's resilient and/or plastic flexure uplift responsive to rack racking and/or load inputs via the at least one tie.

In one embodiment, the seismically supported structure is either a rack or a building.

In one embodiment, there are 2 ties connected to the anchor.

In one embodiment, the ties are connected to an uppermost region of the seismically supported rack.

In one embodiment, the 2 ties are connected to either side of the anchor.

In one embodiment, the ties are subjected to tensile loads during seismic activity in operation.

In one embodiment, the rocker frame extends centrally from the flexure member(s).

In an alternative embodiment, the rocker frame is located with only one flexure member.

In one embodiment, the tie anchor comprises a hold down anchor at each anchor region of a secondary flexure member, (which underlies and supports the primary flexure members) where the rocker frame is centrally located between both hold down anchors.

In one embodiment, at least one hold down anchor is configured to allow its respective anchor region to move in a lateral translational direction towards and away from the other anchor.

In one embodiment, both hold down anchors are configured to allow the respective anchor region of the secondary flexure member to rotate about a rotational axis, located at the respective end region, perpendicular to said elongate direction of the secondary flexure member and parallel to the foundation or base during flexural uplift of the primary flexure member.

In one embodiment, the central pivotal connection is formed in a central hold down anchor intermediate the 2 end hold down anchors of the secondary flexure member.

In one embodiment, the secondary flexure member is over 1 m long.

In one embodiment, the secondary flexure member is 2 m long.

In one embodiment, the rocker frame upstand is over 500 mm tall.

In one embodiment, the rocker frame upstand is 1 m tall.

In one embodiment, the rocker frame upstand is significantly stiff enough to resist substantial elastic deformation so as to transfer the tie forces into the flexure member.

In one embodiment, the primary flexure member is highly flexible relative the upstand.

In one embodiment, the primary flexure member is highly ductile relative the upstand.

In one embodiment, the secondary flexure member which underlies the primary flexure member (plates), substantially forms a curved shape of a standing second order harmonic wave during to deformation.

In one embodiment, the secondary flexure member substantially forms a sideways S shape during deformation.

In one embodiment, the secondary flexure member substantially forms a positive lobe to one side of the upstand and a negative lobe to the other side of the upstand.

In one embodiment, the curved shape of the secondary flexure member has a point coincident with the pivot point of the central anchor that does not translate in any direction.

In one embodiment, the secondary flexure member is divided into two wings, a first wing located at a first side of the central anchor and a second wing located at a second of the central anchor.

In one embodiment, the tie anchor comprises primary elongate flexure members located and connected above each of the first wing and second wing.

In one embodiment, the rocker frame is connected to an intermediate location on each primary flexure member.

In one embodiment, the upstand is a rocking member.

In one embodiment, the upstand is able to rock laterally with respect to the central hold down anchor.

In one embodiment, the upstand is part of the rocker.

In one embodiment, the rocker rocks laterally relative to the central hold down anchor.

In one embodiment, the primary flexure member and secondary flexure member act substantially in series.

In one embodiment, each primary and secondary flexure member has respective primary and secondary end regions.

In one embodiment, each primary and secondary end region has a primary and secondary end anchor.

In one embodiment the primary and secondary end regions of the primary and secondary flexure members are configured to pivot.

In one embodiment, at least one end region of each primary and secondary flexure member is configured to translate with respect to secondary in anchors.

In a further aspect the present invention may be said to be an anchored storage rack assembly, the use of diagonal ties from the rack into a tiltable upstand from a triple anchored damping plate capable of absorbing or dissipating energy provided in the upstand via the ties during a seismic or high force load event.

Preferably the triple anchoring of the plate allows a single curvature flexure upwardly on one side of the upstand and a single curvature flexure downwardly on the other side of the upstand under any racking of the rack relative to the underlying support for the anchors.

In a further aspect the present invention may be said to an energy absorbing structure assembly, the spaced anchoring from an underlying support of an energy absorbing flexure member attached directly or indirectly (e.g. via bolts, ties, ties via an upstand, or the like) to the rack to anchor the rack, the anchoring allowing a symmetric and/or asymmetric arc like movement of the flexure member without endwise cantilevering from its ends from its resilient extent into plastic deformation.

In one embodiment, both ends of the flexure member each allow a rotation about a single axis.

In one embodiment, at least one end of the flexure member allows lateral translation in one direction.

In one embodiment, the lateral translation is towards the other end.

In one embodiment, at least one end is a pinned slot constraint allowing rotation about a single axis and a lateral translation towards the other end.

In a further aspect the present invention may be said to consist in a bracing anchor that is able to substantially convert lateral tensile forces from a structure (preferably of a racking type) into substantially vertical forces in operation, so as to absorb the vertical forces by means of elastic and plastic yielding on one or more elongate flexure members that are dependent (directly or indirectly) from a foundation for the structure.

In one embodiment, the vertical forces are transmitted to the flexure member that absorbs energy, received from the tensile forces, in a controlled manner.

In one embodiment, the structure is held rigidly to the foundation in the absence of seismic activity.

In one embodiment, upon seismic activity the structure has its energy damped via the rocker.

In one embodiment, the flexure members are held rigidly to the foundation in all degrees of freedom with the absence of seismic activity, upon seismic activity and yielding of the flexure members, there is a relative ease of lateral translation along the elongate direction at at least one end region of the flexure member, and relative ease of rotation about a rotational axis, perpendicular to the elongate axis and parallel to the foundation at both end regions of a flexure member.

In one embodiment, there are 2 flexure members.

In one embodiment, there are 3 flexure members.

In one embodiment, at least 2 primary flexure members are supported by a secondary flexure member.

In one embodiment, the relative ease of lateral translation and relative ease of rotation at the end regions limits yielding to a central yield zone.

In a further aspect the present invention may be said to an assembly for absorbing energy from a structure, mounted to a foundation, that will rock in a lateral plane from a seismic event, the assembly comprising

a stiff elongate body configured to rock, during said seismic event, about a pivotable anchor located at a first end of the body, the pivotable anchor having a pivot axis perpendicular to the lateral plane and parallel to the foundation,

a deformable yield member dependent from the body and spaced apart from the pivotable anchor in at least a direction perpendicular to said pivot axis, the deformable yield member connecting the body to a first member of one selected from;said foundation,a vertical chord connected (preferably pivotally) in operation to said foundation,a horizontal chord pivotally connected to a vertical chord connected (preferably pivotally) in operation to said foundation,

the pivotable anchor configured and located so that the body during rocking causes relative movement between the body and the first member and wherein one or more selected from the body, and vertical chord, are configured to engage, or are integral, with the structure in operation so the movement of the structure is transferred to the one or more selected from the body, and vertical chord.

In one embodiment, the relative movement causes plastic deformation of the deformable member.

In one embodiment, the body is a column.

In one embodiment, the body is a truss.

In one embodiment, one or both of the chords are columns.

In one embodiment, one or both of the chords are trusses.

In one embodiment, the deformable yield member is plate like.

In one embodiment, the deformable yield member is a steel plate.

In one embodiment, the deformable yield member is a damper comprising a spring or rubber element.

In one embodiment, the deformable member bends about its minor axis.

In one embodiment, the body and chords are substantially stiff compared to the yield member(s).

In one embodiment, the body is pivotally fixed to the structure two thirds up the height of the structure.

In one embodiment, the vertical chord is pivotally fixed to the structure two thirds up the height of the structure.

In one embodiment, the pivotable anchor is configured to pivotally engage the body with the foundation.

In one embodiment, the deformable member is engaged between the body and the foundation.

In one embodiment, the body comprises a pivotable anchors located at each end of the body, a first pivotable anchor and a second pivotable anchor.

In one embodiment, the second pivotable anchor is attached to an upper region such as an upper floor, ceiling or other upper region of said structure.

In one embodiment, further deformable members are engaged between the body and the upper region.

in one embodiment, the stiff elongate body is substantially horizontal.

In one embodiment, there are two vertical chords, a first vertical chord and a 2nd vertical chord, pivotally connected in operation to said foundation, at each end of the elongate body.

In one embodiment, the first pivotable anchor is attached to the said first vertical chord and the 2nd pivotable anchor is attached to the 2nd vertical chord.

In one embodiment, both vertical chords are configured to pivotally attach to the foundation.

In one embodiment, both vertical chords are configured to pivotally attach to an upper region.

In one embodiment, the body is further engaged to each vertical chord by spaced apart deformable members.

In one embodiment, there are multiple bodies and associated deformable members along the height of the vertical chords.

In one embodiment, the deformable members are substantially plate like members intermediate the body and the vertical chord.

In one embodiment, the deformable members act in a shear like motion between the vertical chord and the body.

In an alternative embodiment, the deformable member has at least two end regions, one first end region constrained relative the body, and the vertical chord is configured to act at the second end region opposite the first end region to deform the deformable member during relative movement.

In one embodiment, the body is substantially elongate in a horizontal direction and pivotally engaged intermediate 2 vertical chords.

In one embodiment, there is least one horizontal chord pivotally engaged intermediate two vertical chords.

In one embodiment, there are two chords pivotally engaged intermediate the two vertical chords.

In one embodiment, the deformable members are intermediate the body and the horizontal chord/s.

In one embodiment, during movement structure or assembly from a seismic event, there is relative movement between the stiff elongate body and the horizontal chord to cause deformation of the deformable members.

In one embodiment, the foundation is one of a ground, a floor, a ceiling, a beam, and a truss.

In one embodiment, at least one end region of the deformable member has a sliding engagement with either the body or the first member.

In one embodiment, there is a tie system to tie the vertical chords and/or body together.

In one embodiment there is a tie system to tie the horizontal chords and/or body together.

In a further aspect the present invention may be said to consist in an energy absorbing system for a structure mounted to a foundation, to constrain lateral movement of an upper region of said structure during a seismic event with respect to the foundation, wherein the system comprises;

a rocker rigidly connected at a first end of a stiff body engaged to said structure and configured to transfer lateral movement of said upper region about the body, the rocker comprisinga pivot anchor that is configured to pivot the body about a pivot axis perpendicular to said lateral movement and parallel said foundation, andat least two spaced apart anchors, one anchor each side of the pivot axis, each anchor dependent from, and intermediate, said foundation and the body, each anchor comprising at least one deformable member configured to plastically deform during said lateral movement, and

wherein a second end of the body opposite the rocker is constrained to one selected from the upper region, and a second rocker.

In one embodiment, said structure is a rack, ceiling, and/or building.

In one embodiment, the foundation is one of a ground, a floor, a ceiling, a beam, and a truss.

In one embodiment, the deformable member is dependent from the foundation.

In one embodiment, the deformable member is dependent from an vertical chord engaged to said structure.

In one embodiment, the vertical chord is substantially stiff compared to the deformable member.

In one embodiment, the vertical chord is pivotally dependent from the foundation on via a vertical chord pivot anchor comprising a vertical chord pivot axis parallel to the pivot anchor pivot axis.

In one embodiment, there are two vertical chords, each with their own respective vertical chord pivot anchor and spaced apart anchors, the anchors and central pivot anchor rigidly joined together by the body.

In one embodiment, the body is a truss.

In one embodiment, the body is substantially rigid compared relative to the deformable members.

In one embodiment, the upper region of the vertical chords are engaged to the structure.

In one embodiment, the vertical chords are engaged to the structure two thirds up the height of the structure.

In a further aspect the present invention may be said to an energy absorbing system for a structure mounted to a foundation to absorb lateral movement of said structure during earthquake, the upper region of the structure moving laterally during a seismic event, wherein the system comprises a body comprising a top region laterally constrained in operation to the upper region of said structure and a base opposite the top region comprising

a pivot that is configured to pivotally depend from said foundation about an axis perpendicular to the lateral movement and parallel the foundation, the pivot allowing the body to rock back and forth about the axis andat least two spaced apart yield connectors, one yield connector on each side of the pivot, each spaced apart yield connector dependent from said foundation and body, and comprising one or more deformable members configured to plastically deform during rocking.

In one embodiment, the upper region of the system is constrained two thirds up the height of the structure.

In one embodiment, the height of the structure is more than 30 metres.

In one embodiment, the top region of the body is constrained with the upper region via cables.

In one embodiment, in operation one yield connector will deform in a clockwise direction and the opposite yield connector will deform in a counter clockwise direction when the body is rocked about the pivot.

In one embodiment, there are two ties connected to the upper region.

In one embodiment, the two ties are connected to the structure either side of the body.

In one embodiment, the ties are subjected to tensile loads during seismic activity in operation.

In one embodiment, the body is substantially stiff so as to allow minimal elastic deformation, and no plastic yielding, during lateral movement of the structure.

In one embodiment, the body may be a multimember truss system.

In one embodiment, the yield connectors are intermediate the body, and one selected from a vertical chord, horizontal chord, and foundation.

In one embodiment, the system comprises cables retaining the body to the vertical and/or or horizontal chord.

In one embodiment, the top region of the body is constrained to the structure from a substantially single point.

In an alternative embodiment, the top region of the body is constrained to the structure from laterally spaced apart regions.

In one embodiment, the deformable member has at least two spaced apart anchor regions.

In one embodiment, a seismic event creates relative movement between the foundation and body, which creates relative movement between the deformable member anchor regions.

In one embodiment, the anchors are configured to allowat least one anchor region to move in a lateral direction towards and away from the other anchor region, andat least one anchor region to rotate about a rotational axis perpendicular to said lateral direction and parallel with the plane of the foundation.

In one embodiment, the deflection of the deformable member caused by plastic yielding is far greater than the deflection caused by elastic deflection.

In one embodiment, the deformable member is highly flexible and/or ductile relative the truss.

In a further aspect a secondary flexural member is located intermediate of the rocker frame(s) inclusive of primary flexural members (plates), and a horizontal (e.g. foundation) or vertical (e.g. columns) structural base.

The invention relates to a control structure which helps direct and control the motion of connected force limiting and energy dissipating structural members (preferably a plate or plates), which are capable of stable cycling high displacement elasto-plastic flexure about their minor bending axis.

The plates enable the control structure to form a stable cycling high displacement elasto-plastic mechanism in resistive response to a seismic ground (base) motion input. The flexural yielding action of the plates in turn, limits the magnitude of forces that can develop within the control structure and within adjacent structures that the control structure may also be seismically supportive of.

That is, the control structure directs and controls the motion of the yielding plates; while the plates, yielding at a constant resistive force, limit the forces generated within the structure(s).

The present invention incorporates a rocker as part of a substantially stiff control structure that incorporates at least one yield connector to(a) transfer movement induced forces from the upper region of a storage rack or building structure to the foundation, and(b) intermediate of the foundation and the upper region through plastic yielding of the yield members (plates) of the control structure, limit forces that could develop both within the control structure and any adjacent structure it is seismically supportive of (rack or building).

In a further aspect the present invention may utilise a yield connector for absorbing energy during oscillatory movement between two structure members, the connector comprises:a first anchor secured directly or indirectly to and to move with one of two structure memberssecond anchor secured to and to move with the other of said structure members,a flexural member having a first region (preferably an end region of the flexural member) supported at the first anchor and a second region (preferably an end region of the flexural member) spaced from the first region and supported at the second anchor in a simply supported manner.

In a further aspect the shear type control structure (alpha2type) may be combined with the direct axial type control structure (alpha1type) to form a composite alpha1/alpha2control structure.

This is to preferably allow the flexural member to yield in a bending mode as the first and second anchors move relative each other in a direction (and reverse) that is normal to the plane of the flexural member.

Preferably at one of the first and second regions, the flexural member is able to rotate and translate relative to its respective anchors and at the other of the first and second regions the flexural member is pinned or cantilever to its respective anchor.

In a further aspect the present invention may be said to a control structure which is able to dissipate energy and limit forces developed within itself or a structure (e.g. building or storage rack) it connects with and is seismically supportive as it endures ground or base motion input from a seismic event, the control structure is comprised of a rocker frame which is pivotably connected to a structural base or structural member, wherein rotation of the rocker frame about its pivot causes a pivotably anchored elongate flexural member(s) which is directly or indirectly connected to the rocker frame, but distal to the rocker frame pivot, to flexurally displace, the flexural member(s) is configured with (i) free translational or (ii) free translational and free rotational boundary conditions to allow it to flex and yield about its minor bending axis to high elasto-plastic displacements (deformation) while maintaining a constant resistive yield force.

Other aspects of the invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings.

As used herein the term “and/or” means “and” or “or”, or both.

As used herein “(s)” following a noun means the plural and/or singular forms of the noun.

The term “comprising” as used in this specification [and claims] means “consisting at least in part of”. When interpreting statements in this specification [and claims] which include that term, the features, prefaced by that term in each statement, all need to be present but other features can also be present. Related terms such as “comprise” and “comprised” are to be interpreted in the same manner.

As used herein the term ‘diagonal’ and its derivatives refers to any angle(s) obliquely of the vertical and the horizontal directions.

‘Single curvature’ means without forming a plural lobed arch form. It includes a symmetric form on either side of its intended attachment to the structure or rack from its anchoring, encumbered, fettered or like adaptions or zones.

As described herein the term plastic or ductile can be interchangeable and relate to material deformation past elastic deformation. When a stress is sufficient to permanently deform a material (such as a flexure member), it is called plastic or ductile deformation.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

